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1.  Towards crystal structure prediction of complex organic compounds – a report on the fifth blind test 
Following on from the success of the previous crystal structure prediction blind tests (CSP1999, CSP2001, CSP2004 and CSP2007), a fifth such collaborative project (CSP2010) was organized at the Cambridge Crystallographic Data Centre. A range of methodologies was used by the participating groups in order to evaluate the ability of the current computational methods to predict the crystal structures of the six organic molecules chosen as targets for this blind test. The first four targets, two rigid molecules, one semi-flexible molecule and a 1:1 salt, matched the criteria for the targets from CSP2007, while the last two targets belonged to two new challenging categories – a larger, much more flexible molecule and a hydrate with more than one polymorph. Each group submitted three predictions for each target it attempted. There was at least one successful prediction for each target, and two groups were able to successfully predict the structure of the large flexible molecule as their first place submission. The results show that while not as many groups successfully predicted the structures of the three smallest molecules as in CSP2007, there is now evidence that methodologies such as dispersion-corrected density functional theory (DFT-D) are able to reliably do so. The results also highlight the many challenges posed by more complex systems and show that there are still issues to be overcome.
PMCID: PMC3222142  PMID: 22101543
2.  Efficacy of a modern neuroscience approach versus usual care evidence-based physiotherapy on pain, disability and brain characteristics in chronic spinal pain patients: protocol of a randomized clinical trial 
Among the multiple conservative modalities, physiotherapy is a commonly utilized treatment modality in managing chronic non-specific spinal pain. Despite the scientific progresses with regard to pain and motor control neuroscience, treatment of chronic spinal pain (CSP) often tends to stick to a peripheral biomechanical model, without targeting brain mechanisms. With a view to enhance clinical efficacy of existing physiotherapeutic treatments for CSP, the development of clinical strategies targeted at ‘training the brain’ is to be pursued. Promising proof-of-principle results have been reported for the effectiveness of a modern neuroscience approach to CSP when compared to usual care, but confirmation is required in a larger, multi-center trial with appropriate evidence-based control intervention and long-term follow-up.
The aim of this study is to assess the effectiveness of a modern neuroscience approach, compared to usual care evidence-based physiotherapy, for reducing pain and improving functioning in patients with CSP. A secondary objective entails examining the effectiveness of the modern neuroscience approach versus usual care physiotherapy for normalizing brain gray matter in patients with CSP.
The study is a multi-center, triple-blind, two-arm (1:1) randomized clinical trial with 1-year follow-up. 120 CSP patients will be randomly allocated to either the experimental (receiving pain neuroscience education followed by cognition-targeted motor control training) or the control group (receiving usual care physiotherapy), each comprising of 3 months treatment. The main outcome measures are pain (including symptoms and indices of central sensitization) and self-reported disability. Secondary outcome measures include brain gray matter structure, motor control, muscle properties, and psychosocial correlates. Clinical assessment and brain imaging will be performed at baseline, post-treatment and at 1-year follow-up. Web-based questionnaires will be completed at baseline, after the first 3 treatment sessions, post-treatment, and at 6 and 12-months follow-up.
Findings may provide empirical evidence on: (1) the effectiveness of a modern neuroscience approach to CSP for reducing pain and improving functioning, (2) the effectiveness of a modern neuroscience approach for normalizing brain gray matter in CSP patients, and (3) factors associated with therapy success. Hence, this trial might contribute towards refining guidelines for good clinical practice and might be used as a basis for health authorities’ recommendations.
Trial registration Identifier: NCT02098005.
PMCID: PMC4028010  PMID: 24885889
Chronic pain; Low back pain; Neck pain; Education; Exercise; Motor control; Neuroscience; Randomized controlled trial
3.  Immunogenicity when utilizing adenovirus serotype 4 and 5 vaccines expressing circumsporozoite protein in naïve and Adenovirus (Ad5) immune mice 
Malaria Journal  2012;11:209.
Induction of potent long lasting effector T cell responses against liver stage malaria antigens strongly correlates with protection from malaria. While Adenovirus serotype 5 (Ad5) based malaria vaccine platforms have the ability to induce potent effector T cell responses against transgenes, high rates of pre-existing Ad5 immunity in malaria endemic regions has prompted study of alternative Ad serotype based malaria vaccines as replacements for Ad5 based malaria vaccines. The research described in this article examines the utility of alternative serotype adenovirus serotype 4 (Ad4) expressing a sporozoite surface protein (circumsporozoite protein (CSP)) (Ad4-CSP) to induce immune responses against CSP. The immunogenicity of Ad4-CSP was also tested in homologous and heterologous prime boost vaccinations in both Ad5 naïve and Ad5 immune backgrounds as compared to use of Ad5-CSP.
In Ad5 naïve animals, use of Ad4-CSP priming vaccinations followed by boosting with Ad5-CSP (Ad4-CSP/Ad5-CSP) maximally increased the numbers of CSP specific cytokine secreting cytotoxic T cells relative to repeated use of Ad5-CSP. The Ad4-CSP/Ad5-CSP regimen also induced equivalent levels of CSP specific cell killing as did homologous prime-boost vaccinations with Ad5-CSP, despite stimulating lower numbers of CSP specific cytotoxic T cells. Priming with Ad4-CSP followed by a homologous boost resulted in significantly less CSP specific humoral responses than any other vaccination regimen tested in Ad naïve animals. In Ad5 immune animals, addition of Ad4-CSP in homologous or heterologous prime boost resulted in inductions of higher CSP specific responses than animals repeatedly vaccinated with Ad5-CSP alone. However, the observed responses were well below those observed in similarly treated Ad naïve mice.
While the Ad4-CSP/Ad5-CSP and Ad5-CSP/Ad5-CSP vaccination regimens resulted in equivalent CSP specific killing in Ad naïve animals, Ad4-CSP/Ad5-CSP achieved this result with a lower percentage of CSP specific CD8+ T cells and a higher number of IFNγ secreting cells, suggesting that the Ad4-CSP/Ad5-CSP vaccination regimen elicits more efficient cytotoxic T cells. In Ad5 immune animals use of Ad4-CSP improved CSP specific immune responses as compared to repeated use of Ad5-CSP, but could not achieve the levels of immunogenicity observed when the same vaccine regimens were used in Ad naïve animals. These data indicate the existence of some level of immunological cross-reactivity between these two adenovirus subgroups. Based on these results, it is suggested that future studies should undertake similarly stringent analyses of alternative Ad serotypes to establish their effectiveness as replacements for Ad5.
PMCID: PMC3472263  PMID: 22720732
Serotype 5; Serotype 4; Adenovirus; Malaria; Circumsporozoite protein; Vaccine; Heterologous; Homologous; Prime; Boost
4.  Cavum Septum Pellucidum in Schizophrenia: Clinical and Neuropsychological Correlates 
Psychiatry research  2007;154(2):147-155.
Increased frequency of cavum septum pellucidum (CSP) has been inconsistently observed in schizophrenia, and little is known about its functional implications. We investigated whether patients with schizophrenia were more likely than healthy controls to have CSP, and among patients assessed the relationship between CSP, psychiatric symptoms, and selected neuropsychological functions. Seventy-seven patients with diagnoses of DSM-IV schizophrenia spectrum disorders and 55 healthy controls were studied and completed a 1.5 T MRI scan. Two raters, blind to group membership, determined the presence, length and grade of the CSP. A subset of participants also underwent neuropsychological testing. A CSP of at least 1 mm in length was present in 68.8% of patients and 76.4% of controls, and the groups did not differ significantly with respect to presence or absence, length, overall size, or percent with an abnormally large CSP (≥ 6 mm). Patients with an abnormally large CSP demonstrated poorer performance on measures of verbal learning and memory than patients with smaller CSP. Among patients, CSP length was significantly correlated with negative symptoms, verbal learning, and sentence comprehension. Among patients with abnormally large CSP, CSP length was correlated with reaction time on two conditions of a Continuous Performance Test. CSP, while prevalent, was not more frequent in our sample of patients with schizophrenia, and had few associations with symptom severity or neuropsychological deficits.
PMCID: PMC1858669  PMID: 17291728
Schizophrenia; MRI; Cavum Septum Pellucidum; Neuropsychology
5.  Adenovirus 5-Vectored P. falciparum Vaccine Expressing CSP and AMA1. Part A: Safety and Immunogenicity in Seronegative Adults 
PLoS ONE  2011;6(10):e24586.
Models of immunity to malaria indicate the importance of CD8+ T cell responses for targeting intrahepatic stages and antibodies for targeting sporozoite and blood stages. We designed a multistage adenovirus 5 (Ad5)-vectored Plasmodium falciparum malaria vaccine, aiming to induce both types of responses in humans, that was tested for safety and immunogenicity in a Phase 1 dose escalation trial in Ad5-seronegative volunteers.
Methodology/Principal Findings
The NMRC-M3V-Ad-PfCA vaccine combines two adenovectors encoding circumsporozoite protein (CSP) and apical membrane antigen-1 (AMA1). Group 1 (n = 6) healthy volunteers received one intramuscular injection of 2×10∧10 particle units (1×10∧10 each construct) and Group 2 (n = 6) a five-fold higher dose. Transient, mild to moderate adverse events were more pronounced with the higher dose. ELISpot responses to CSP and AMA1 peaked at 1 month, were higher in the low dose (geomean CSP = 422, AMA1 = 862 spot forming cells/million) than in the high dose (CSP = 154, p = 0.049, AMA1 = 423, p = 0.045) group and were still positive at 12 months in a number of volunteers. ELISpot depletion assays identified dependence on CD4+ or on both CD4+ and CD8+ T cells, with few responses dependent only on CD8+ T cells. Intracellular cytokine staining detected stronger CD8+ than CD4+ T cell IFN-γ responses (CSP p = 0.0001, AMA1 p = 0.003), but similar frequencies of multifunctional CD4+ and CD8+ T cells secreting two or more of IFN-γ, TNF-α or IL-2. Median fluorescence intensities were 7–10 fold higher in triple than single secreting cells. Antibody responses were low but trended higher in the high dose group and did not inhibit growth of cultured P. falciparum blood stage parasites.
As found in other trials, adenovectored vaccines appeared safe and well-tolerated at doses up to 1×10∧11 particle units. This is the first demonstration in humans of a malaria vaccine eliciting strong CD8+ T cell IFN-γ responses.
Trial Registration NCT00392015
PMCID: PMC3189181  PMID: 22003383
6.  BcL-xL Conformational Changes upon Fragment Binding Revealed by NMR 
PLoS ONE  2013;8(5):e64400.
Protein-protein interactions represent difficult but increasingly important targets for the design of therapeutic compounds able to interfere with biological processes. Recently, fragment-based strategies have been proposed as attractive approaches for the elaboration of protein-protein surface inhibitors from fragment-like molecules. One major challenge in targeting protein-protein interactions is related to the structural adaptation of the protein surface upon molecular recognition. Methods capable of identifying subtle conformational changes of proteins upon fragment binding are therefore required at the early steps of the drug design process. In this report we present a fast NMR method able to probe subtle conformational changes upon fragment binding. The approach relies on the comparison of experimental fragment-induced Chemical Shift Perturbation (CSP) of amine protons to CSP simulated for a set of docked fragment poses, considering the ring-current effect from fragment binding. We illustrate the method by the retrospective analysis of the complex between the anti-apoptotic Bcl-xL protein and the fragment 4′-fluoro-[1,1′-biphenyl]-4-carboxylic acid that was previously shown to bind one of the Bcl-xL hot spots. The CSP-based approach shows that the protein undergoes a subtle conformational rearrangement upon interaction, for residues located in helices 2, 3 and the very beginning of 5. Our observations are corroborated by residual dipolar coupling measurements performed on the free and fragment-bound forms of the Bcl-xL protein. These NMR-based results are in total agreement with previous molecular dynamic calculations that evidenced a high flexibility of Bcl-xL around the binding site. Here we show that CSP of protein amine protons are useful and reliable structural probes. Therefore, we propose to use CSP simulation to assess protein conformational changes upon ligand binding in the fragment-based drug design approach.
PMCID: PMC3662666  PMID: 23717610
7.  Structure and Function of Cold Shock Proteins in Archaea▿  
Journal of Bacteriology  2007;189(15):5738-5748.
Archaea are abundant and drive critical microbial processes in the Earth's cold biosphere. Despite this, not enough is known about the molecular mechanisms of cold adaptation and no biochemical studies have been performed on stenopsychrophilic archaea (e.g., Methanogenium frigidum). This study examined the structural and functional properties of cold shock proteins (Csps) from archaea, including biochemical analysis of the Csp from M. frigidum. csp genes are present in most bacteria and some eucarya but absent from most archaeal genome sequences, most notably, those of all archaeal thermophiles and hyperthermophiles. In bacteria, Csps are small, nucleic acid binding proteins involved in a variety of cellular processes, such as transcription. In this study, archaeal Csp function was assessed by examining the ability of csp genes from psychrophilic and mesophilic Euryarchaeota and Crenarchaeota to complement a cold-sensitive growth defect in Escherichia coli. In addition, an archaeal gene with a cold shock domain (CSD) fold but little sequence identity to Csps was also examined. Genes encoding Csps or a CSD structural analog from three psychrophilic archaea rescued the E. coli growth defect. The three proteins were predicted to have a higher content of solvent-exposed basic residues than the noncomplementing proteins, and the basic residues were located on the nucleic acid binding surface, similar to their arrangement in E. coli CspA. The M. frigidum Csp was purified and found to be a single-domain protein that folds by a reversible two-state mechanism and to exhibit a low conformational stability typical of cold-adapted proteins. Moreover, M. frigidum Csp was characterized as binding E. coli single-stranded RNA, consistent with its ability to complement function in E. coli. The studies show that some Csp and CSD fold proteins have retained sufficient similarity throughout evolution in the Archaea to be able to function effectively in the Bacteria and that the function of the archaeal proteins relates to cold adaptation. The initial biochemical analysis of M. frigidum Csp has developed a platform for further characterization and demonstrates the potential for expanding molecular studies of proteins from this important archaeal stenopsychrophile.
PMCID: PMC1951829  PMID: 17545280
8.  Ultrastructural Characterization of Olfactory Sensilla and Immunolocalization of Odorant Binding and Chemosensory Proteins from an Ectoparasitoid Scleroderma guani (Hymenoptera: Bethylidae) 
The three-dimensional structures of two odorant binding proteins (OBPs) and one chemosensory protein (CSP) from a polyphagous ectoparasitoid Scleroderma guani (Hymenoptera: Bethylidae) were resolved bioinformatically. The results show that both SguaOBP1 and OBP2 are classic OBPs, whereas SguaCSP1 belongs to non-classic CSPs which are considered as the “Plus-C” CSP in this report. The structural differences between the two OBPs and between OBP and CSP are thoroughly described, and the structural and functional significance of the divergent C-terminal regions (e.g., the prolonged C-terminal region in SguaOBP2 and the additional pair of cysteines in SguaCSP1) are discussed. The immunoblot analyses with antisera raised against recombinant SguaOBP1, OBP2, and CSP1, respectively, indicate that two SguaOBPs are specific to antennae, whereas SguaCSP1, which are more abundant than OBPs and detected in both male and female wasps, expresses ubiquitously across different tissues.
We also describe the ultrastructure of the antennal sensilla types in S. guani and compare them to 19 species of parasitic Hymenoptera. There are 11 types of sensilla in the flagellum and pedicel segments of antennae in both male and female wasps. Seven of them, including sensilla placodea (SP), long sensilla basiconica (LSB), sensilla coeloconica (SC), two types of double-walled wall pore sensilla (DWPS-I and DWPS-II), and two types of sensilla trichodea (ST-I and ST-II), are multiporous chemosensilla. The ultralsturctures of these sensilla are morphologically characterized. In comparison to monophagous specialists, the highly polyphagous generalist ectoparasitoids such as S. guani possess more diverse sensilla types which are likely related to their broad host ranges and complex life styles. Our immunocytochemistry study demonstrated that each of the seven sensilla immunoreacts with at least one antiserum against SguaOBP1, OBP2, and CSP1, respectively. Anti-OBP2 is specifically labeled in DWPS-II, whereas the anti-OBP1 shows a broad spectrum of immunoactivity toward four different sensilla (LSB, SP, ST-I and ST-II). On the other hand, anti-CSP1 is immunoactive toward SP, DWPS-I and SC. Interestingly, a cross co-localization pattern between SguaOBP1 and CSP1 is documented for the first time. Given that the numbers of OBPs and CSPs in many insect species greatly outnumber their antennal sensilla types, it is germane to suggest such phenomenon could be the rule rather than the exception.
PMCID: PMC3149280  PMID: 21814481
Scleroderma guani; OBP; CSP; tertiary structure; sensilla; immunolocalization
9.  Sulfated and sulfonated polysaccharide as chiral stationary phases for capillary electrochromatography and capillary electrochromatography–mass spectrometry 
Journal of chromatography. A  2008;1216(5):857-872.
The applications of polysaccharide phenyl carbamate derivatives as chiral stationary phases (CSPs) for capillary electrochromatography (CEC) are often hindered by longer retention times, especially using a normal-phase (NP) eluent due to very low electroosmotic flow (EOF). Therefore, in this study, we propose an approach for the aforementioned problems by introducing two new types of negatively charged sulfate and sulfonated groups for polysaccharide CSPs. These CSPs were utilized to pack CEC columns for enantioseparation with a NP eluent. Compared to conventional cellulose tris(3,5-dimethylphenyl carbamate) or CDMPC CSPs, the sulfated CDMPC CSP (sulfur content 4.25%, w/w) shortened the analysis time up to 50% but with a significant loss of enantiomeric resolution (~60%). On the other hand, the sulfonated CDMPC CSP (sulfur content 1.76%, w/w) not only provided fast throughput but also maintained excellent resolving power. In addition, its synthesis is much more straightforward than the sulfated one. Furthermore, we studied several stationary phase parameters (CSP loading and silica gel pore size) and mobile phase parameters (including type of mobile phase and its composition) to evaluate the throughput and enantioselectivity. Using the optimized conditions, a chiral pool containing 66 analytes was screened to evaluate the enantioselectivity under three different mobile phase modes (i.e., NP, polar organic phase (POP) and reversed-phase (RP) eluents). Among these mobile phase modes, the RP mode showed the highest success rate, whereas some degree of complementary enantioselectivity was observed with NP and POP. Finally, the feasibility of applying this CSP for CEC–MS enantioseparation using internal tapered column was evaluated with NP, POP and RP eluents. In particular, the NP-CEC–MS provided significantly enhanced sensitivity when methanol was replaced with isopropanol in the sheath liquid. Using aminog-lutethimide as model chiral analyte, all three modes of CEC–MS demonstrated excellent durability as well as excellent reproducibility of retention time and enantioselectivity.
PMCID: PMC2752677  PMID: 19108837
Sulfonated polysaccharide; Chiral stationary phase loading; Pore size; Normal-phase CEC–MS; Reversed-phase CEC–MS; Polar organic phase CEC–MS
10.  CspA, the major cold shock protein of Escherichia coli, negatively regulates its own gene expression. 
Journal of Bacteriology  1997;179(22):7081-7088.
When the gene for CspA, the major cold shock protein of Escherichia coli, was disrupted by a novel positive/negative selection method, the deltacspA cells did not show any discernible growth defect at either 37 or 15 degrees C. By two-dimensional gel electrophoresis, total protein synthesis was analyzed after temperature downshift in the deltacspA strain. The production of the CspA homologs CspB and CspG increased, and the duration of their expression was prolonged, suggesting that both CspB and CspG compensate for the function of CspA in the absence of CspA during cold shock adaptation. Interestingly, the production of the 159-base 5'-untranslated region (5'-UTR) of cspA from the chromosomal cspA::cat gene, detected by primer extension, failed to be repressed after cold shock. When an independent system to produce CspA was added to the deltacspA strain, the 5'-UTR production for the cspA::cat gene was significantly reduced compared to that of the deltacspA strain. By examining the expression of translationally fused cspA and cspB genes to lacZ in the deltacspA strain, it was found that cspA is more strongly regulated by CspA than cspB is. We showed that the increased expression of the 5'-UTR of the cspA mRNA in the deltacspA strain occurred mainly at the level of transcription and, to a certain extent, at the level of mRNA stabilization. The mRNA stabilization in the deltacspA strain was observed for other mRNAs, supporting the notion that CspA functions as an mRNA chaperone to destabilize secondary structures in mRNAs.
PMCID: PMC179650  PMID: 9371456
11.  Identification of a nonameric H-2Kk-restricted CD8+ cytotoxic T lymphocyte epitope on the Plasmodium falciparum circumsporozoite protein. 
Infection and Immunity  1995;63(5):1955-1959.
Class I-restricted CD8+ cytotoxic T lymphocytes (CTL) against the circumsporozoite protein (CSP) protect mice against the rodent malaria parasite, Plasmodium yoelii, and vaccines designed to produce protective CTL against the P. falciparum CSP (PfCSP) are under development. Humans and B10.BR (H-2k) mice have been shown to have CD8+ CTL activity against a 23-amino-acid region of the PfCSP (residues 368 to 390 from the PfCSP 7G8 sequence) that is too long to bind directly to class I major histocompatibility complex molecules. To identify within this 23-amino-acid peptide a shorter peptide that binds to an H-2k class I major histocompatibility molecule, a primarily CD8+ (97.8%) T-cell line (PfCSP TCL.1) was produced by immunizing B10.BR mice with recombinant vaccinia virus expressing the PfCSP and stimulating in vitro spleen cells from these immunized mice with L cells transfected with the PfCSP gene (LPF cells). PfCSP TCL.1 lysed LPF cells and L cells pulsed with peptide PfCSP 7G8 368-390. When 15 overlapping nonamer peptides spanning the 368 to 390 sequence were tested, only one peptide, PfCSP 7G8 375-383 (Y E N D I E K K I), which includes an H-2Kk-binding motif, E at amino acid residue 2, and I at residue 9, sensitized targets for lysis by PfCSP TCL.1. Furthermore, a 10(3)- to 10(4)-fold lower concentration of the nonamer than that of the 23-amino-acid peptide was required to sensitize target cells for lysis by PfCSP TCL.1. Presentation by H-2Kk was demonstrated by using 3T3 fibroblast cells transfected with the murine H-2Kk or H-2Dk genes, and only the H-2Kk transfectants were lysed by PfCSP TCL.1 after incubation with peptide PfCSP 7G8 375-383. Binding to H-2Kk was confirmed by competitive inhibition of binding of labelled peptides to affinity-purified Kk molecules. Substitution of the anchor amino acid residue, E, at position 2 with A dramatically reduced binding to Kk and eliminated the capacity of the peptide to sensitize target cells for killing. Variation of non-anchor residues did not markedly reduce binding to Kk but in some cases eliminated the capacity of the peptide to sensitize targets for cytolysis by PfCSP TCL.1, presumably by eliminating T-cell receptor-binding sites. These data suggest that similar studies with human T cells will be required for optimal development of peptide-based vaccines designed to produce protective class I-restricted CD8+ CTL against the PfCSP in humans.
PMCID: PMC173249  PMID: 7537251
12.  Identification of minimal human MHC-restricted CD8+ T-cell epitopes within the Plasmodium falciparum circumsporozoite protein (CSP) 
Malaria Journal  2013;12:185.
Plasmodium falciparum circumsporozoite protein (CSP) is a leading malaria vaccine candidate antigen, known to elicit protective antibody responses in humans (RTS,S vaccine). Recently, a DNA prime / adenovirus (Ad) vector boost vaccine encoding CSP and a second P. falciparum antigen, apical membrane antigen-1, also elicited sterile protection, but in this case associated with interferon gamma ELISpot and CD8+ T cell but not antibody responses. The finding that CSP delivered by an appropriate vaccine platform likely elicits protective cell-mediated immunity provided a rationale for identifying class I-restricted epitopes within this leading vaccine candidate antigen.
Limited samples of peripheral blood mononuclear cells from clinical trials of the Ad vaccine were used to identify CD8+ T cell epitopes within pools of overlapping 15mer peptides spanning portions of CSP that stimulated recall responses. Computerized algorithms (NetMHC) predicted 17 minimal class I-restricted 9-10mer epitopes within fifteen 15mers positive in ELISpot assay using PBMC from 10 HLA-matched study subjects. Four additional epitopes were subsequently predicted using NetMHC, matched to other study subjects without initial 15mer ELISpot screening. Nine of the putative epitopes were synthesized and tested by ELISpot assay, and six of these nine were further tested for CD8+ T cell responses by ELISpot CD4+ and CD8+ T cell-depletion and flow cytometry assays for evidence of CD8+ T cell dependence.
Each of the nine putative epitopes, all sequence-conserved, recalled responses from HLA-matched CSP-immunized research subjects. Four shorter sequences contained within these sequences were identified using NetMHC predictions and may have contributed to recall responses. Five (9-10mer) epitopes were confirmed to be targets of CD8+ T cell responses using ELISpot depletion and ICS assays. Two 9mers among these nine epitopes were each restricted by two HLA supertypes (A01/B07; A01A24/A24) and one 9mer was restricted by three HLA supertypes (A01A24/A24/B27) indicating that some CSP class I-restricted epitopes, like DR epitopes, may be HLA-promiscuous.
This study identified nine and confirmed five novel class I epitopes restricted by six HLA supertypes, suggesting that an adenovirus-vectored CSP vaccine would be immunogenic and potentially protective in genetically diverse populations.
PMCID: PMC3683343  PMID: 23738590
Malaria; Vaccine; Circumsporozoite protein; ELISpot; Flow cytometry; NetMHC; Epitope mapping; Class I restriction; Localization
13.  Characterization of cspB, a Bacillus subtilis inducible cold shock gene affecting cell viability at low temperatures. 
Journal of Bacteriology  1992;174(20):6326-6335.
A new class of cold shock-induced proteins that may be involved in an adaptive process required for cell viability at low temperatures or may function as antifreeze proteins in Escherichia coli and Saccharomyces cerevisiae has been identified. We purified a small Bacillus subtilis cold shock protein (CspB) and determined its amino-terminal sequence. By using mixed degenerate oligonucleotides, the corresponding gene (cspB) was cloned on two overlapping fragments of 5 and 6 kb. The gene encodes an acidic 67-amino-acid protein (pI 4.31) with a predicted molecular mass of 7,365 Da. Nucleotide and deduced amino acid sequence comparisons revealed 61% identity to the major cold shock protein of E. coli and 43% identity to a family of eukaryotic DNA binding proteins. Northern RNA blot and primer extension studies indicated the presence of one cspB transcript that was initiated 119 bp upstream of the initiation codon and was found to be induced severalfold when exponentially growing B. subtilis cell cultures were transferred from 37 degrees C to 10 degrees C. Consistent with this cold shock induction of cspB mRNA, a six- to eightfold induction of a cspB-directed beta-galactosidase synthesis was observed upon downshift in temperature. To investigate the function of CspB, we inactivated the cold shock protein by replacing the cspB gene in the B. subtilis chromosome with a cat-interrupted copy (cspB::cat) by marker replacement recombination. The viability of cells of this mutant strain, GW1, at freezing temperatures was strongly affected. However, the effect of having no CspB in GW1 could be slightly compensated for when cells were preincubated at 10 degrees C before freezing. These results indicate that CspB belongs to a new type of stress-inducible proteins that might be able to protect B. subtilis cells from damage caused by ice crystal formation during freezing.
PMCID: PMC207576  PMID: 1400185
14.  Pathogenic Yersinia Species Carry a Novel, Cold-Inducible Major Cold Shock Protein Tandem Gene Duplication Producing both Bicistronic and Monocistronic mRNA 
Journal of Bacteriology  1999;181(20):6449-6455.
Inverse PCR was used to amplify major cold shock protein (MCSP) gene families from a diverse range of bacteria, including the psychrotolerant Yersinia enterocolitica, which was found to have two almost identical MCSP coding regions (cspA1 and cspA2) located approximately 300 bp apart. This tandem gene duplication was also found in Y. pestis, Y. pseudotuberculosis, and Y. ruckeri but not in other bacteria. Analysis of the transcriptional regulation of this MCSP gene in Y. enterocolitica, performed by using both reverse transcriptase-PCR and Northern blot assays, showed there to be two cold-inducible mRNA templates arising from this locus: a monocistronic template of approximately 450 bp (cspA1) and a bicistronic template of approximately 900 bp (cspA1/A2). The former may be due to a secondary structure between cspA1 and cspA2 causing either 3′ degradation protection of cspA1 or, more probably, partial termination after cspA1. Primer extension experiments identified a putative transcriptional start site (+1) which is flanked by a cold-box motif and promoter elements (−10 and −35) similar to those found in Escherichia coli cold-inducible MCSP genes. At 30°C, the level of both mRNA molecules was negligible; however, upon a temperature downshift to 10°C, transcription of the bicistronic mRNA was both substantial (300-fold increase) and immediate, with transcription of the monocistronic mRNA being approximately 10-fold less (30-fold increase) and significantly slower. The ratio of bicistronic to monocistronic mRNA changed with time after cold shock and was higher when cells were shocked to a lower temperature. High-resolution, two-dimensional protein gel electrophoresis showed that synthesis of the corresponding proteins, both CspA1 and CspA2, was apparent after only 10 min of cold shock from 30°C to 10°C. The data demonstrate an extraordinary capacity of the psychrotolerant Y. enterocolitica to produce major cold shock proteins upon cold shock.
PMCID: PMC103781  PMID: 10515936
15.  Comparison of patients diagnosed with gonorrhoea through community screening with those self-presenting to the genitourinary medicine clinic 
BMJ Open  2014;4(3):e004862.
To compare the clinical, socioeconomic and demographic characteristics of individuals diagnosed with Neisseria gonorrhoeae (NG) in the community using a concomitant nucleic acid amplification test (NAAT, AptimaCombo2) as part of the (community-based) UK Chlamydia Screening Programme (CSP), with those diagnosed in hospital-based genitourinary medicine (GUM) services.
A retrospective case note review of all 643 patients treated for NG at a GUM in north west England (January 2007–April 2009).
All 643 treated for NG (including CSP cases, since all cases were referred to GUM for treatment). Limited data were available for 13 CSP cases who failed to attend GUM.
Primary outcome measure
Whether the case was detected in the community or GUM services. Predictors were demographics (age, gender, postcode for deprivation analysis), sexual history (eg, number of partners) and clinical factors (eg, culture positivity).
131 cases were diagnosed by CSP (13 of whom did not attend GUM). A further four cases were contacts of these. The GUM caseload was thus inflated by 23% (from 521 to 643). Community cases were overwhelmingly female (85% vs 27% in GUM, p<0.001) and younger (87% females were <25 years vs 70% GUM females, p=0.001). Logistic regression analysis restricted to the target age of the CSP (<25 years) revealed that CSP cases, compared with GUM cases, were more likely to reside in deprived areas (adjusted OR=5.6, 95% CI 1.4 to 21.8 and 5.3, CI 1.7 to 16.6 for the most and second most deprived group respectively, compared with the averagely deprived group, p=0.037) and be asymptomatic (adjusted OR=1.9, CI 1.1 to 3.4, p=0.02).
Community screening for NG led to a 79% increase in the number of infections detected in women aged <25 years. Screening is targeted at young people, and tends to disproportionately attract young women, a group under-represented at GUM. Screening also contributed further to case detection in deprived areas.
PMCID: PMC3963091  PMID: 24633530
Genitourinary Medicine; Socioeconomic Status; Mass screening; Community Health Services; Residence Characteristics; Neisseria Gonorrhoeae
16.  Structural and Functional Analysis of the CspB Protease Required for Clostridium Spore Germination 
PLoS Pathogens  2013;9(2):e1003165.
Spores are the major transmissive form of the nosocomial pathogen Clostridium difficile, a leading cause of healthcare-associated diarrhea worldwide. Successful transmission of C. difficile requires that its hardy, resistant spores germinate into vegetative cells in the gastrointestinal tract. A critical step during this process is the degradation of the spore cortex, a thick layer of peptidoglycan surrounding the spore core. In Clostridium sp., cortex degradation depends on the proteolytic activation of the cortex hydrolase, SleC. Previous studies have implicated Csps as being necessary for SleC cleavage during germination; however, their mechanism of action has remained poorly characterized. In this study, we demonstrate that CspB is a subtilisin-like serine protease whose activity is essential for efficient SleC cleavage and C. difficile spore germination. By solving the first crystal structure of a Csp family member, CspB, to 1.6 Å, we identify key structural domains within CspB. In contrast with all previously solved structures of prokaryotic subtilases, the CspB prodomain remains tightly bound to the wildtype subtilase domain and sterically occludes a catalytically competent active site. The structure, combined with biochemical and genetic analyses, reveals that Csp proteases contain a unique jellyroll domain insertion critical for stabilizing the protease in vitro and in C. difficile. Collectively, our study provides the first molecular insight into CspB activity and function. These studies may inform the development of inhibitors that can prevent clostridial spore germination and thus disease transmission.
Author Summary
Clostridium difficile is the leading cause of health-care associated diarrhea worldwide. C. difficile infections begin when its spores transform into vegetative cells during a process called germination. In Clostridium sp., germination requires that the spore cortex, a thick, protective layer, be removed by the cortex hydrolase SleC. While previous studies have shown that SleC activity depends on a subtilisin-like protease, CspB, the mechanisms regulating CspB function have not been characterized. In this study, we solved the first crystal structure of the Csp family of proteases and identified its key functional regions. We determined that CspB carries a unique jellyroll domain required for stabilizing the protein both in vitro and in C. difficile and a prodomain required for proper folding of the protease. Unlike all other prokaryotic subtilisin-like proteases, the prodomain remains bound to CspB and inhibits its protease activity until the germination signal is sensed. Our study provides new insight into how germination is regulated in C. difficile and may inform the development of inhibitors that can prevent germination and thus C. difficile transmission.
PMCID: PMC3567191  PMID: 23408892
17.  Establishing the definition and inter-rater reliability of cortical silent period calculation in subjects with focal hand dystonia and healthy controls 
Neuroscience letters  2009;464(2):84-87.
The purpose of this paper is to describe a clearly defined manual method for calculating cortical silent period (CSP) length that can be employed successfully and reliably by raters after minimal training in subjects with focal hand dystonia (FHD) and healthy subjects. A secondary purpose was to explore intra-subject variability of the CSP in subjects with FHD vs. healthy subjects.
Two raters previously naïve to CSP identification and one experienced rater independently analyzed 170 CSP measurements collected in six subjects with focal hand dystonia (FHD) and nine healthy subjects. Intraclass correlation coefficient (ICC) was calculated to quantify inter-rater reliability within the two groups of subjects. The relative variability of CSP in each group was calculated by coefficient of variation (CV). Relative variation between raters within repeated measures of individual subjects was also quantified by CV.
Reliability measures were as follows: mean of three raters: all subjects: ICC= 0.976; within healthy subjects: ICC=0.965; in subjects with FHD: ICC= 0.956. The median within-subject variability for the healthy group was CV=7.33% and in subjects with FHD: CV= 11.78%. The median variability of calculating individual subject CSP duration between raters was CV=10.23% in subjects with dystonia and CV=10.46% in healthy subjects.
Manual calculation of CSP results in excellent reliability between raters of varied levels of experience. Healthy subjects display less variability in CSP. Despite greater variability, the CSP in impaired subjects can be reliably calculated across raters.
PMCID: PMC2752976  PMID: 19686807
cortical silent period; cortical excitability; focal hand dystonia; reliability; definition; methodology; transcranial magnetic stimulation
18.  Protection of Rhesus Monkeys by a DNA Prime/Poxvirus Boost Malaria Vaccine Depends on Optimal DNA Priming and Inclusion of Blood Stage Antigens 
PLoS ONE  2007;2(10):e1063.
We have previously described a four antigen malaria vaccine consisting of DNA plasmids boosted by recombinant poxviruses which protects a high percentage of rhesus monkeys against Plasmodium knowlesi (Pk) malaria. This is a multi-stage vaccine that includes two pre-erythrocytic antigens, PkCSP and PkSSP2(TRAP), and two erythrocytic antigens, PkAMA-1 and PkMSP-1(42kD). The present study reports three further experiments where we investigate the effects of DNA dose, timing, and formulation. We also compare vaccines utilizing only the pre-erythrocytic antigens with the four antigen vaccine.
In three experiments, rhesus monkeys were immunized with malaria vaccines using DNA plasmid injections followed by boosting with poxvirus vaccine. A variety of parameters were tested, including formulation of DNA on poly-lactic co-glycolide (PLG) particles, varying the number of DNA injections and the amount of DNA, varying the interval between the last DNA injection to the poxvirus boost from 7 to 21 weeks, and using vaccines with from one to four malaria antigens. Monkeys were challenged with Pk sporozoites given iv 2 to 4 weeks after the poxvirus injection, and parasitemia was measured by daily Giemsa stained blood films. Immune responses in venous blood samples taken after each vaccine injection were measured by ELIspot production of interferon-γ, and by ELISA.
1) the number of DNA injections, the formulation of the DNA plasmids, and the interval between the last DNA injection and the poxvirus injection are critical to vaccine efficacy. However, the total dose used for DNA priming is not as important; 2) the blood stage antigens PkAMA-1 and PkMSP-1 were able to protect against high parasitemias as part of a genetic vaccine where antigen folding is not well defined; 3) immunization with PkSSP2 DNA inhibited immune responses to PkCSP DNA even when vaccinations were given into separate legs; and 4) in a counter-intuitive result, higher interferon-γ ELIspot responses to the PkCSP antigen correlated with earlier appearance of parasites in the blood, despite the fact that PkCSP vaccines had a protective effect.
PMCID: PMC2031826  PMID: 17957247
Brain research  2010;1324:34-42.
Until recently, organized and state-dependent neocortical activity in infant rats was thought to commence with the emergence of delta waves at postnatal day (P)11. This view is changing with the discovery of several forms of cortical activity that are detectible soon after birth, including spindle bursts (SBs) and slow activity transients (SATs). Here we provide further evidence of surprisingly rich cortical activity patterns during early development and document, in P5-P13 rats, the appearance, disappearance, and transient expression of three cortical events and oscillations. EEG activity in frontal, parietal, and occipital cortices was recorded in unanesthetized, head-fixed subjects using 16-channel laminar silicon electrodes and Ag-AgCl electrodes. In addition to SATs, we identified two novel forms of activity: cortical sharp potentials (CSPs) and gamma bursts (GBs). SBs were not observed in these areas. CSPs, defined as discrete, biphasic events with a duration of 250 ms, exhibited an inverted-U developmental trajectory with peak prevalence at P9. In contrast, GBs, defined as brief bursts of 40-Hz activity, increased steadily in prevalence and duration from P5 through P13. The prevalence of SATs decreased steadily across the ages tested here. Furthermore, both CSPs and GBs were more likely to occur during sleep than during wakefulness. Because SATs, CSPs, and GBs exhibit different developmental trajectories and rates of occurrence, and can occur independently of each other, they appear to be distinct patterns of neuronal activity. We hypothesize that these diverse patterns of neurophysiological activity reflect the instantaneous local structure and connectivity of the developing neocortex.
PMCID: PMC2848902  PMID: 20138849
sleep; EEG; delta activity; slow activity transient; spindle burst; GABA
20.  Reduced Expression of Inflammatory Genes in Deceased Donor Kidneys Undergoing Pulsatile Pump Preservation 
PLoS ONE  2012;7(4):e35526.
The use of expanded criteria donor kidneys (ECD) had been associated with worse outcomes. Whole gene expression of pre-implantation allograft biopsies from deceased donor kidneys (DDKs) was evaluated to compare the effect of pulsatile pump preservation (PPP) vs. cold storage preservation (CSP) on standard and ECD kidneys.
Methodology/Principal Findings
99 pre-implantation DDK biopsies were studied using gene expression with GeneChips. Kidneys transplant recipients were followed post transplantation for 35.8 months (range = 24–62). The PPP group included 60 biopsies (cold ischemia time (CIT)  = 1,367+/−509 minutes) and the CSP group included 39 biopsies (CIT = 1,022+/−485 minutes) (P<0.001). Donor age (42.0±14.6 vs. 34.1±14.2 years, P = 0.009) and the percentage of ECD kidneys (PPP = 35% vs. CSP = 12.8%, P = 0.012) were significantly different between groups. A two-sample t-test was performed, and probe sets having a P<0.001 were considered significant. Probe set level linear models were fit using cold ischemia time and CSP/PPP as independent variables to determine significant probe sets (P<0.001) between groups after adjusting for cold ischemia time. Thus, 43 significant genes were identified (P<0.001). Over-expression of genes associated with inflammation (CD86, CD209, CLEC4, EGFR2, TFF3, among others) was observed in the CSP group. Cell-to-cell signaling and interaction, and antigen presentation were the most important pathways with genes significantly over-expressed in CSP kidneys. When the analysis was restricted to ECD kidneys, genes involved in inflammation were also differentially up-regulated in ECD kidneys undergoing CSP. However, graft survival at the end of the study was similar between groups (P = 0.2). Moreover, the incidence of delayed graft function was not significant between groups.
Inflammation was the most important up-regulated pattern associated with pre-implantation biopsies undergoing CSP even when the PPP group has a larger number of ECD kidneys. No significant difference was observed in delayed graft function incidence and graft function post-transplantation. These findings support the use of PPP in ECD donor kidneys.
PMCID: PMC3335841  PMID: 22545113
21.  Probabilistic Common Spatial Patterns for Multichannel EEG Analysis 
Common spatial patterns (CSP) is a well-known spatial filtering algorithm for multichannel electroencephalogram (EEG) analysis. In this paper, we cast the CSP algorithm in a probabilistic modeling setting. Specifically, probabilistic CSP (P-CSP) is proposed as a generic EEG spatio-temporal modeling framework that subsumes the CSP and regularized CSP algorithms. The proposed framework enables us to resolve the overfitting issue of CSP in a principled manner. We derive statistical inference algorithms that can alleviate the issue of local optima. In particular, an efficient algorithm based on eigendecomposition is developed for maximum a posteriori (MAP) estimation in the case of isotropic noise. For more general cases, a variational algorithm is developed for group-wise sparse Bayesian learning for the P-CSP model and for automatically determining the model size. The two proposed algorithms are validated on a simulated data set. Their practical efficacy is also demonstrated by successful applications to single-trial classifications of three motor imagery EEG data sets and by the spatio-temporal pattern analysis of one EEG data set recorded in a Stroop color naming task.
PMCID: PMC4441303  PMID: 26005228
Common spatial patterns; Fukunaga-Koontz transform; sparse Bayesian learning; variational Bayes; electroencephalogram; brain-computer interface
22.  Serological responses to a soluble recombinant chimeric Plasmodium vivax circumsporozoite protein in VK210 and VK247 population 
Malaria Journal  2013;12:323.
Circumsporozoite protein (CSP) is essential for sporozoite formation and sporozoite invasion into human hepatocyte. Previously, a recombinant P. vivax CSP based on chimeric repeats (rPvCSP-c) representing two major alleles VK210 and VK247 within central region has been designed. Naturally acquired humoral immune responses study show that antigenicity of rPvCSP-c was much higher than that of native strain. However, the serologic reactivity of rPvCSP-c was still unclear in detail.
In present study, recognition of rPvCSP-c in vivax malaria typed VK210 and VK247 alleles was assessed. VK210 typed and VK247 typed sera from adult residents reacted specifically with rPvCSP-c using protein array and immunoblot assay. Additionally, anti-rPvCSP-c serum recognized the fixed VK210 and VK247 sporozoites by immunofluorescence assay. Furthermore, statistic analysis was performed for correlational detection.
The rPvCSP-c reacted with both VK210 typed and VK247 typed P. vivax infected patient sera and anti-rPvCSP-c immune serum also reacted with VK210 and VK247 sporozoite parasites of P. vivax specifically. There was a positive correlation between increased antibody level, age of patients and also associated with pvcsp repeat number, although the level of responses did vary considerably in their reactivity to the rPvCSP-c from negative to very high level within each age group.
These data confirmed the serologic reactivity of the novel rPvCSP-c in exposed both VK210 and VK247 populations. These results strongly suggested that this recombinant CSP was biologically active and potently immunogenic across major strains and raised the prospect that this protein could be used as serologic marker.
PMCID: PMC3847697  PMID: 24034268
23.  DNA Prime/Adenovirus Boost Malaria Vaccine Encoding P. falciparum CSP and AMA1 Induces Sterile Protection Associated with Cell-Mediated Immunity 
PLoS ONE  2013;8(2):e55571.
Gene-based vaccination using prime/boost regimens protects animals and humans against malaria, inducing cell-mediated responses that in animal models target liver stage malaria parasites. We tested a DNA prime/adenovirus boost malaria vaccine in a Phase 1 clinical trial with controlled human malaria infection.
Methodology/Principal Findings
The vaccine regimen was three monthly doses of two DNA plasmids (DNA) followed four months later by a single boost with two non-replicating human serotype 5 adenovirus vectors (Ad). The constructs encoded genes expressing P. falciparum circumsporozoite protein (CSP) and apical membrane antigen-1 (AMA1). The regimen was safe and well-tolerated, with mostly mild adverse events that occurred at the site of injection. Only one AE (diarrhea), possibly related to immunization, was severe (Grade 3), preventing daily activities. Four weeks after the Ad boost, 15 study subjects were challenged with P. falciparum sporozoites by mosquito bite, and four (27%) were sterilely protected. Antibody responses by ELISA rose after Ad boost but were low (CSP geometric mean titer 210, range 44–817; AMA1 geometric mean micrograms/milliliter 11.9, range 1.5–102) and were not associated with protection. Ex vivo IFN-γ ELISpot responses after Ad boost were modest (CSP geometric mean spot forming cells/million peripheral blood mononuclear cells 86, range 13–408; AMA1 348, range 88–1270) and were highest in three protected subjects. ELISpot responses to AMA1 were significantly associated with protection (p = 0.019). Flow cytometry identified predominant IFN-γ mono-secreting CD8+ T cell responses in three protected subjects. No subjects with high pre-existing anti-Ad5 neutralizing antibodies were protected but the association was not statistically significant.
The DNA/Ad regimen provided the highest sterile immunity achieved against malaria following immunization with a gene-based subunit vaccine (27%). Protection was associated with cell-mediated immunity to AMA1, with CSP probably contributing. Substituting a low seroprevalence vector for Ad5 and supplementing CSP/AMA1 with additional antigens may improve protection.
Trial Registration
PMCID: PMC3573028  PMID: 23457473
24.  Inhibition of Competence Development, Horizontal Gene Transfer and Virulence in Streptococcus pneumoniae by a Modified Competence Stimulating Peptide 
PLoS Pathogens  2011;7(9):e1002241.
Competence stimulating peptide (CSP) is a 17-amino acid peptide pheromone secreted by Streptococcus pneumoniae. Upon binding of CSP to its membrane-associated receptor kinase ComD, a cascade of signaling events is initiated, leading to activation of the competence regulon by the response regulator ComE. Genes encoding proteins that are involved in DNA uptake and transformation, as well as virulence, are upregulated. Previous studies have shown that disruption of key components in the competence regulon inhibits DNA transformation and attenuates virulence. Thus, synthetic analogues that competitively inhibit CSPs may serve as attractive drugs to control pneumococcal infection and to reduce horizontal gene transfer during infection. We performed amino acid substitutions on conserved amino acid residues of CSP1 in an effort to disable DNA transformation and to attenuate the virulence of S. pneumoniae. One of the mutated peptides, CSP1-E1A, inhibited development of competence in DNA transformation by outcompeting CSP1 in time and concentration-dependent manners. CSP1-E1A reduced the expression of pneumococcal virulence factors choline binding protein D (CbpD) and autolysin A (LytA) in vitro, and significantly reduced mouse mortality after lung infection. Furthermore, CSP1-E1A attenuated the acquisition of an antibiotic resistance gene and a capsule gene in vivo. Finally, we demonstrated that the strategy of using a peptide inhibitor is applicable to other CSP subtype, including CSP2. CSP1-E1A and CSP2-E1A were able to cross inhibit the induction of competence and DNA transformation in pneumococcal strains with incompatible ComD subtypes. These results demonstrate the applicability of generating competitive analogues of CSPs as drugs to control horizontal transfer of antibiotic resistance and virulence genes, and to attenuate virulence during infection by S. pneumoniae.
Author Summary
Streptococcus pneumoniae is a major cause of pneumonia, ear infection and meningitis. Antibiotic resistance among S. pneumoniae isolates is increasingly a major clinical problem. The acquisition of antibiotic resistance genes in S. pneumoniae is controlled by a peptide pheromone called competence-stimulating peptide (CSP). CSP binds to a receptor called ComD, which in turn activates its cognate transcription factor ComE to initiate DNA uptake and integration into the S. pneumoniae genome. CSP-ComD/E also regulates the expression of virulence factors required for infection. In this study, multiple synthetic analogues of CSP pheromone were examined for their ability to inhibit acquisition of exogenous DNA, and to control infection by S. pneumoniae in mice. Two of these analogues, CSP1-E1A and CSP2-E1A, competitively inhibit the ability of S. pneumoniae to acquire the streptomycin resistance rpsL gene and the capsule gene cap3A during mouse models of acute pneumonia and bacteremia. CSP1-E1A also reduces mouse mortality during lung infection by S. pneumoniae. This is the first demonstration of the use of CSP analogues to attenuate virulence and to inhibit acquisition of an antibiotic resistance gene in S. pneumoniae. Because the CSP-ComD/E system is conserved among many pathogenic bacteria, CSP analogues may be applicable to reduce the spread of antibiotic resistance genes and to treat infections.
PMCID: PMC3164649  PMID: 21909280
25.  Sterile Protection against Malaria Is Independent of Immune Responses to the Circumsporozoite Protein 
PLoS ONE  2007;2(12):e1371.
Research aimed at developing vaccines against infectious diseases generally seeks to induce robust immune responses to immunodominant antigens. This approach has led to a number of efficient bacterial and viral vaccines, but it has yet to do so for parasitic pathogens. For malaria, a disease of global importance due to infection by Plasmodium protozoa, immunization with radiation-attenuated sporozoites uniquely leads to long lasting sterile immunity against infection. The circumsporozoite protein (CSP), an important component of the sporozoite's surface, remains the leading candidate antigen for vaccines targeting the parasite's pre-erythrocytic stages. Difficulties in developing CSP-based vaccines that reproduce the levels of protection afforded by radiation-attenuated sporozoites have led us to question the role of CSP in the acquisition of sterile immunity. We have used a parasite transgenic for the CSP because it allowed us to test whether a major immunodominant Plasmodium antigen is indeed needed for the induction of sterile protective immunity against infection.
Methodology/Main Findings
We employed a P. berghei parasite line that expresses a heterologous CSP from P. falciparum in order to assess the role of the CSP in the protection conferred by vaccination with radiation-attenuated P. berghei parasites. Our data demonstrated that sterile immunity could be obtained despite the absence of immune responses specific to the CSP expressed by the parasite used for challenge.
We conclude that other pre-erythrocytic parasite antigens, possibly hitherto uncharacterised, can be targeted to induce sterile immunity against malaria. From a broader perspective, our results raise the question as to whether immunodominant parasite antigens should be the favoured targets for vaccine development.
PMCID: PMC2147056  PMID: 18159254

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