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1.  The HIV-1 late domain-2 S40A polymorphism in antiretroviral (or ART)-exposed individuals influences protease inhibitor susceptibility 
Retrovirology  2016;13(1):64.
The p6 region of the HIV-1 structural precursor polyprotein, Gag, contains two motifs, P7TAP11 and L35YPLXSL41, designated as late (L) domain-1 and -2, respectively. These motifs bind the ESCRT-I factor Tsg101 and the ESCRT adaptor Alix, respectively, and are critical for efficient budding of virus particles from the plasma membrane. L domain-2 is thought to be functionally redundant to PTAP. To identify possible other functions of L domain-2, we examined this motif in dominant viruses that emerged in a group of 14 women who had detectable levels of HIV-1 in both plasma and genital tract despite a history of current or previous antiretroviral therapy.
Remarkably, variants possessing mutations or rare polymorphisms in the highly conserved L domain-2 were identified in seven of these women. A mutation in a conserved residue (S40A) that does not reduce Gag interaction with Alix and therefore did not reduce budding efficiency was further investigated. This mutation causes a simultaneous change in the Pol reading frame but exhibits little deficiency in Gag processing and virion maturation. Whether introduced into the HIV-1 NL4-3 strain genome or a model protease (PR) precursor, S40A reduced production of mature PR. This same mutation also led to high level detection of two extended forms of PR that were fairly stable compared to the WT in the presence of IDV at various concentrations; one of the extended forms was effective in trans processing even at micromolar IDV.
Our results indicate that L domain-2, considered redundant in vitro, can undergo mutations in vivo that significantly alter PR function. These may contribute fitness benefits in both the absence and presence of PR inhibitor.
Electronic supplementary material
The online version of this article (doi:10.1186/s12977-016-0298-1) contains supplementary material, which is available to authorized users.
PMCID: PMC5011916  PMID: 27600154
HIV Gag; HIV protease; Protease inhibitors; Late domain; Anti-retroviral drugs; ESCRT
2.  Integrated sequence and immunology filovirus database at Los Alamos 
The Ebola outbreak of 2013–15 infected more than 28 000 people and claimed more lives than all previous filovirus outbreaks combined. Governmental agencies, clinical teams, and the world scientific community pulled together in a multifaceted response ranging from prevention and disease control, to evaluating vaccines and therapeutics in human trials. As this epidemic is finally coming to a close, refocusing on long-term prevention strategies becomes paramount. Given the very real threat of future filovirus outbreaks, and the inherent uncertainty of the next outbreak virus and geographic location, it is prudent to consider the extent and implications of known natural diversity in advancing vaccines and therapeutic approaches. To facilitate such consideration, we have updated and enhanced the content of the filovirus portion of Los Alamos Hemorrhagic Fever Viruses Database. We have integrated and performed baseline analysis of all family Filoviridae sequences deposited into GenBank, with associated immune response data, and metadata, and we have added new computational tools with web-interfaces to assist users with analysis. Here, we (i) describe the main features of updated database, (ii) provide integrated views and some basic analyses summarizing evolutionary patterns as they relate to geo-temporal data captured in the database and (iii) highlight the most conserved regions in the proteome that may be useful for a T cell vaccine strategy.
Database URL:
PMCID: PMC4839628  PMID: 27103629
3.  Comparative genomic analyses reveal broad diversity in botulinum-toxin-producing Clostridia 
BMC Genomics  2016;17:180.
Clostridium botulinum is a diverse group of bacteria characterized by the production of botulinum neurotoxin. Botulinum neurotoxins are classified into serotypes (BoNT/A–G), which are produced by six species/Groups of Clostridia, but the genetic background of the bacteria remains poorly understood. The purpose of this study was to use comparative genomics to provide insights into the genetic diversity and evolutionary history of bacteria that produce the potent botulinum neurotoxin.
Comparative genomic analyses of over 170 Clostridia genomes, including our draft genome assemblies for 59 newly sequenced Clostridia strains from six continents and publicly available genomic data, provided in-depth insights into the diversity and distribution of BoNT-producing bacteria. These newly sequenced strains included Group I and II strains that express BoNT/A,/B,/E, or/F as well as bivalent strains. BoNT-producing Clostridia and closely related Clostridia species were delineated with a variety of methods including 16S rRNA gene, concatenated marker genes, core genome and concatenated multi-locus sequencing typing (MLST) gene phylogenies that related whole genome sequenced strains to publicly available strains and sequence types. These analyses illustrated the phylogenetic diversity in each Group and the diversity of genomic backgrounds that express the same toxin type or subtype. Comparisons of the botulinum neurotoxin genes did not identify novel toxin types or variants.
This study represents one of the most comprehensive analyses of whole genome sequence data for Group I and II BoNT-producing strains. Read data and draft genome assemblies generated for 59 isolates will be a resource to the research community. Core genome phylogenies proved to be a powerful tool for differentiating BoNT-producing strains and can provide a framework for the study of these bacteria. Comparative genomic analyses of Clostridia species illustrate the diversity of botulinum-neurotoxin-producing strains and the plasticity of the genomic backgrounds in which bont genes are found.
Electronic supplementary material
The online version of this article (doi:10.1186/s12864-016-2502-z) contains supplementary material, which is available to authorized users.
PMCID: PMC4778365  PMID: 26939550
Clostridium botulinum; Botulinum neurotoxin; Whole genome sequence; Comparative genomics
4.  Comment on “The Origins of Sexually Transmitted HIV Among Men Who Have Sex with Men” 
Science translational medicine  2010;2(50):50le1-50lr1.
Whether HIV from seminal cells or free HIV in semen is the origin of transmitted virus has important implications for the design of transmission prevention strategies. We found that a recent claim that HIV originates from seminal plasma and not from seminal cells was erroneous, because it was based on biological specimens that had been mislabeled, mixed-up, or contaminated. The origin of transmitted virus from semen therefore remains an open question.
PMCID: PMC4745562  PMID: 20861507
5.  CATNAP: a tool to compile, analyze and tally neutralizing antibody panels 
Nucleic Acids Research  2015;43(Web Server issue):W213-W219.
CATNAP (Compile, Analyze and Tally NAb Panels) is a new web server at Los Alamos HIV Database, created to respond to the newest advances in HIV neutralizing antibody research. It is a comprehensive platform focusing on neutralizing antibody potencies in conjunction with viral sequences. CATNAP integrates neutralization and sequence data from published studies, and allows users to analyze that data for each HIV Envelope protein sequence position and each antibody. The tool has multiple data retrieval and analysis options. As input, the user can pick specific antibodies and viruses, choose a panel from a published study, or supply their own data. The output superimposes neutralization panel data, virus epidemiological data, and viral protein sequence alignments on one page, and provides further information and analyses. The user can highlight alignment positions, or select antibody contact residues and view position-specific information from the HIV databases. The tool calculates tallies of amino acids and N-linked glycosylation motifs, counts of antibody-sensitive and -resistant viruses in conjunction with each amino acid or N-glycosylation motif, and performs Fisher's exact test to detect potential positive or negative amino acid associations for the selected antibody. Website name: CATNAP (Compile, Analyze and Tally NAb Panels). Website address:
PMCID: PMC4489231  PMID: 26044712
6.  Chemically Exfoliated MoS2 as Near-Infrared Photothermal Agents** 
PMCID: PMC4193793  PMID: 23471666
dichalcogenides; molybdenum; organic—inorganic hybrid composites; photothermal therapy; supramolecular chemistry
7.  Phylogenetic Analysis of Near Full-Length HIV Type 1 Genomic Sequences from 21 Korean Individuals 
The Korean subclade of subtype B (KSB) is the most prevalent HIV-1 strain found in Korea. To date, only two near full-length HIV-1 sequences from Korean patients have been reported. Here, we analyzed a total of 24 near full-length genomes of HIV-1 strains that were isolated from 17 antiretroviral therapy (ART)-naive patients and four ART-exposed patients. Proviral DNA from peripheral blood mononuclear cells was PCR amplified and directly sequenced. Phylogenetic analyses were used to classify viruses from 19 patients as KSB, from one patient as subtype B, from one patient as subtype D, and three viruses from one patient as CRF02_AG. All KSB viruses demonstrated TAAAA instead of TATAA at the TATA box in the LTR. Of the 19 KSB patients, their sequence identities at the nucleotide level ranged from 89.8% to 97.1% from the lowest env gene to the highest pol gene. Other than the CRF02_AG viruses, no recombination events were noted in any of the 19 KSB patients, which is consistent with our previous studies on the pol, vif, and nef genes. Except for one strain, all of the strains were classified as non-syncytium-inducing strains. This is the first report to describe near full-length KSB.
PMCID: PMC3607908  PMID: 23199052
8.  Laser Capture Microdissection Assessment of Virus Compartmentalization in the Central Nervous Systems of Macaques Infected with Neurovirulent Simian Immunodeficiency Virus 
Journal of Virology  2013;87(16):8896-8908.
Nonhuman primate-simian immunodeficiency virus (SIV) models are powerful tools for studying the pathogenesis of human immunodeficiency virus type 1 (HIV-1) in the brain. Our laboratory recently isolated a neuropathogenic viral swarm, SIVsmH804E, a derivative of SIVsmE543-3, which was the result of sequential intravenous passages of viruses isolated from the brains of rhesus macaques with SIV encephalitis. Animals infected with SIVsmH804E or its precursor (SIVsmH783Br) developed SIV meningitis and/or encephalitis at high frequencies. Since we observed macaques with a combination of meningitis and encephalitis, as well as animals in which meningitis or encephalitis was the dominant component, we hypothesized that distinct mechanisms could be driving the two pathological states. Therefore, we assessed viral populations in the meninges and the brain parenchyma by laser capture microdissection. Viral RNAs were isolated from representative areas of the meninges, brain parenchyma, terminal plasma, and cerebrospinal fluid (CSF) and from the inoculum, and the SIV envelope fragment was amplified by PCR. Phylogenetic analysis of envelope sequences from the conventional progressors revealed compartmentalization of viral populations between the meninges and the parenchyma. In one of these animals, viral populations in meninges were closely related to those from CSF and shared signature truncations in the cytoplasmic domain of gp41, consistent with a common origin. Apart from magnetic resonance imaging (MRI) and positron-emission tomography (PET) imaging, CSF is the most accessible assess to the central nervous system for HIV-1-infected patients. However, our results suggest that the virus in the CSF may not always be representative of viral populations in the brain and that caution should be applied in extrapolating between the properties of viruses in these two compartments.
PMCID: PMC3754082  PMID: 23720733
9.  Recombination Between Variants from Genital Tract and Plasma: Evolution of Multidrug-Resistant HIV Type 1 
AIDS Research and Human Retroviruses  2012;28(12):1766-1774.
Multidrug-resistant (MDR) HIV-1 presents a challenge to the efficacy of antiretroviral therapy (ART). To examine mechanisms leading to MDR variants in infected individuals, we studied recombination between single viral genomes from the genital tract and plasma of a woman initiating ART. We determined HIV-1 RNA sequences and drug resistance profiles of 159 unique viral variants obtained before ART and semiannually for 4 years thereafter. Soon after initiating zidovudine, lamivudine, and nevirapine, resistant variants and intrapatient HIV-1 recombinants were detected in both compartments; the recombinants had inherited genetic material from both genital and plasma-derived viruses. Twenty-three unique recombinants were documented during 4 years of therapy, comprising ∼22% of variants. Most recombinant genomes displayed similar breakpoints and clustered phylogenetically, suggesting evolution from common ancestors. Longitudinal analysis demonstrated that MDR recombinants were common and persistent, demonstrating that recombination, in addition to point mutation, can contribute to the evolution of MDR HIV-1 in viremic individuals.
PMCID: PMC3505048  PMID: 22364185
10.  Near Full-Length Sequence Analysis of HIV Type 1 BF Recombinants from Italy 
Recombination between HIV-1 subtypes B and F has generated several circulating and unique recombinant forms, particularly in Latin American areas. In Italy, subtype B is highly prevalent while subtype F is the most common pure non-B subtype. To investigate the recombination pattern in Italian BF recombinant viruses, we characterized full-length sequences derived from 15 adult patients, mostly Italian and infected by the heterosexual route. One of the BF mosaics was a CRF29, three sequences clustered with low bootstrap values with CRF39, CRF40, and CRF42. With the exception of the CRF29-like sequence, the other recombination patterns were unique, but two possible clusters were identified. Analysis of the gp120 V3 domain suggested a possible link with subtype F from Eastern Europe rather than from Latin America, favoring the hypothesis of local recombination between clade B and F viruses over that of import of BF recombinants from Latin America. HIV-1 subtypes B and F appear prone to generation of unique recombinants in Italy, warranting epidemiological surveillance and investigation of a possible clinical significance.
PMCID: PMC3292755  PMID: 21740272
11.  Characterization of full-length HIV-1 CRF17_BF genomes and comparison to the prototype CRF12_BF strains ☆ 
The aim of this work is to characterize the full-length intersubtype recombinant structure of the HIV-1 Circulating Recombinant Form CRF17_BF. A single genome of CRF17_BF was originally described in 2001 as being largely similar to CRF12_BF. Since then, more genomes of CRF17_BF have been sequenced but not adequately described in publications. Here we describe CRF17_BF as a genuine CRF, and analyze its recombination pattern based on bootscan analyses, subtype signature patterns, and phylogenetic reconstruction of subtype-delimited segments. We show that CRF17_BF can be distinguished from CRF12_BF in several regions of the genome, including vpu, pol, env and nef. A complete and accurate characterization and description of recombination breakpoints in CRFs is required for a proper surveillance of HIV-1 genotypes, and important for epidemiological purposes.
PMCID: PMC3471996  PMID: 22266022
HIV-1 subtypes; Argentina; BF recombinants; HIV diversity; Molecular epidemiology; CRF17_BF
12.  Designing and Testing Broadly-Protective Filoviral Vaccines Optimized for Cytotoxic T-Lymphocyte Epitope Coverage 
PLoS ONE  2012;7(10):e44769.
We report the rational design and in vivo testing of mosaic proteins for a polyvalent pan-filoviral vaccine using a computational strategy designed for the Human Immunodeficiency Virus type 1 (HIV-1) but also appropriate for Hepatitis C virus (HCV) and potentially other diverse viruses. Mosaics are sets of artificial recombinant proteins that are based on natural proteins. The recombinants are computationally selected using a genetic algorithm to optimize the coverage of potential cytotoxic T lymphocyte (CTL) epitopes. Because evolutionary history differs markedly between HIV-1 and filoviruses, we devised an adapted computational technique that is effective for sparsely sampled taxa; our first significant result is that the mosaic technique is effective in creating high-quality mosaic filovirus proteins. The resulting coverage of potential epitopes across filovirus species is superior to coverage by any natural variants, including current vaccine strains with demonstrated cross-reactivity. The mosaic cocktails are also robust: mosaics substantially outperformed natural strains when computationally tested against poorly sampled species and more variable genes. Furthermore, in a computational comparison of cross-reactive potential a design constructed prior to the Bundibugyo outbreak performed nearly as well against all species as an updated design that included Bundibugyo. These points suggest that the mosaic designs would be more resilient than natural-variant vaccines against future Ebola outbreaks dominated by novel viral variants. We demonstrate in vivo immunogenicity and protection against a heterologous challenge in a mouse model. This design work delineates the likely requirements and limitations on broadly-protective filoviral CTL vaccines.
PMCID: PMC3463593  PMID: 23056184
13.  Analysis of Clostridium botulinum Serotype E Strains by Using Multilocus Sequence Typing, Amplified Fragment Length Polymorphism, Variable-Number Tandem-Repeat Analysis, and Botulinum Neurotoxin Gene Sequencing▿ 
Applied and Environmental Microbiology  2011;77(24):8625-8634.
A total of 41 Clostridium botulinum serotype E strains from different geographic regions, including Canada, Denmark, Finland, France, Greenland, Japan, and the United States, were compared by multilocus sequence typing (MLST), amplified fragment length polymorphism (AFLP) analysis, variable-number tandem-repeat (VNTR) analysis, and botulinum neurotoxin (bont) E gene sequencing. The strains, representing environmental, food-borne, and infant botulism samples collected from 1932 to 2007, were analyzed to compare serotype E strains from different geographic regions and types of botulism and to determine whether each of the strains contained the transposon-associated recombinase rarA, involved with bont/E insertion. MLST examination using 15 genes clustered the strains into several clades, with most members within a cluster sharing the same BoNT/E subtype (BoNT/E1, E2, E3, or E6). Sequencing of the bont/E gene identified two new variants (E7, E8) that showed regions of recombination with other E subtypes. The AFLP dendrogram clustered the 41 strains similarly to the MLST dendrogram. Strains that could not be differentiated by AFLP, MLST, or bont gene sequencing were further examined using three VNTR regions. Both intact and split rarA genes were amplified by PCR in each of the strains, and their identities were confirmed in 11 strains by amplicon sequencing. The findings suggest that (i) the C. botulinum serotype E strains result from the targeted insertion of the bont/E gene into genetically conserved bacteria and (ii) recombination events (not random mutations) within bont/E result in toxin variants or subtypes within strains.
PMCID: PMC3233090  PMID: 22003031
14.  Phylogenetic Analysis of the Earliest nef Gene from Hemophiliacs and Local Controls in Korea 
BioResearch Open Access  2012;1(1):41-49.
Twenty hemophiliacs (HPs) were found to have human immunodeficiency virus type-1 (HIV-1) 1–2 years after exposure to Factor IX manufactured in Korea in late 1989. Plasma samples collected from donors O and P during their pre-seroconversion acute infection stage were used to manufacture clotting factors, including Factor IX, to treat these patients. To assess whether a genetic relationship exists between the viruses infecting HIV-1-positive HPs and those infecting plasma donors, we evaluated the nef sequences in 216 individuals. Frozen-stored serum samples obtained 1–3 years after the diagnosis of HIV-1 in the 20 HPs were used for amplification of the nef gene by reverse transcriptase–polymerase chain reaction, and amplicons were subjected to direct sequencing. Phylogenetic analysis revealed that the nef sequences from 143 of the samples belonged to the Korean subclade of HIV-1 subtype B (KSB). Sequences of the nef gene from donors O and P and the 20 HPs comprised two subclusters within KSB together with several local control (LC) sequences. In addition, signature pattern analysis revealed the presence of conserved nucleotides at eight positions in donors O and P compared with LCs (p<0.01). These nationwide and comprehensive nef data support the previous conclusion that HPs were infected with HIV-1 from the clotting factor, although the stringency of nef is weaker than for the pol and vif genes.
PMCID: PMC3559220  PMID: 23514897
hemophilia; HIV-1; nef; phylogenetic analysis; signature pattern analysis
15.  Evolution and Recombination of Genes Encoding HIV-1 Drug Resistance and Tropism during Antiretroviral Therapy 
Virology  2010;404(1):5-20.
Characterization of residual plasma virus during antiretroviral therapy (ART) is a high priority to improve understanding of HIV-1 pathogenesis and therapy. To understand the evolution of HIV-1 pol and env genes in viremic patients under selective pressure of ART, we performed longitudinal analyses of plasma-derived pol and env sequences from single HIV-1 genomes. We tested the hypotheses that drug resistance in pol was unrelated to changes in coreceptor usage (tropism), and that recombination played a role in evolution of viral strains. Recombinants were identified by using Bayesian and other computational methods. High-level genotypic resistance was seen in ~70% of X4 and R5 strains during ART. There was no significant association between resistance and tropism. Each patient displayed at least one recombinant encompassing env and representing a change in predicted tropism. These data suggest that, in addition to mutation, recombination can play a significant role in shaping HIV-1 evolution.
PMCID: PMC3186207  PMID: 20451945
HIV-1 drug resistance; HIV-1 recombination; HIV-1 tropism
16.  HIV-1 subtype distribution in the Gambia and the significant presence of CRF49_cpx, a novel circulating recombinant form 
Retrovirology  2010;7:82.
Detailed local HIV-1 sequence data are essential for monitoring the HIV epidemic, for maintaining sensitive sequence-based diagnostics, and to aid in designing vaccines.
Reported here are full envelope sequences derived from 38 randomly selected HIV-1 infections identified at a Gambian clinic between 1991 and 2009. Special care was taken to generate sequences from circulating viral RNA as uncloned products, either by limiting dilution or single genome amplification polymerase chain reaction (PCR). Within these 38 isolates, eight were subtyped as A and 18 as CRF02_AG. A small number of subtype B, C, D viruses were identified. Surprising, however, was the identification of six isolates with subtype J-like envelopes, a subtype found normally in Central Africa and the Democratic Republic of the Congo (DRC), with gag p24 regions that clustered with subtype A sequences. Near full-length sequence from three of these isolates confirmed that these represent a novel circulating recombinant form of HIV-1, now named CRF49_cpx.
This study expands the HIV-1 sequence database from the Gambia and will provide important data for HIV diagnostics, patient care, and vaccine development.
PMCID: PMC2964586  PMID: 20932333
17.  Complex Mosaic Composition of Near Full-Length Genomes of Two NED (NIH-ENVA-DOD) Subtype Panel HIV Type 1 Strains, BCF-Dioum and BCF-Kita, Originating from the Democratic Republic of Congo (DRC) 
AIDS Research and Human Retroviruses  2009;25(10):1039-1043.
Sequence characterization of the near full-length genomes of HIV-1 isolates BCF-Dioum and BCF-Kita, originating from the Democratic Republic of Congo (DRC), was continued. These NED panel isolates, contributed by F. Brun-Vezinet (ENVA-France), were first identified as subtypes G and H, respectively. Our earlier analyses of portions of their pol genes showed that both were likely to be intersubtype recombinants of different composition. This study analyzed the remainder of each genome, confirming them to be complex recombinants. The BCF-Dioum genome resembles CRF06_cpx strains found in West Africa, composed of subtypes A/G/J/K. The BCF-Kita genome is a unique complex recombinant A–F–G–H–K–U strain. These data support previous observations of the complexity of strains originating from the DRC. BCF-Dioum may be a suitable strain for standards and reagents since it matches a defined circulating recombinant form. Studies and reagents made from BCF-Kita should take into account its complex genome.
PMCID: PMC2828238  PMID: 19795987
18.  The role of recombination in the emergence of a complex and dynamic HIV epidemic 
Retrovirology  2010;7:25.
Inter-subtype recombinants dominate the HIV epidemics in three geographical regions. To better understand the role of HIV recombinants in shaping the current HIV epidemic, we here present the results of a large-scale subtyping analysis of 9435 HIV-1 sequences that involve subtypes A, B, C, G, F and the epidemiologically important recombinants derived from three continents.
The circulating recombinant form CRF02_AG, common in West Central Africa, appears to result from recombination events that occurred early in the divergence between subtypes A and G, followed by additional recent recombination events that contribute to the breakpoint pattern defining the current recombinant lineage. This finding also corrects a recent claim that G is a recombinant and a descendant of CRF02, which was suggested to be a pure subtype. The BC and BF recombinants in China and South America, respectively, are derived from recent recombination between contemporary parental lineages. Shared breakpoints in South America BF recombinants indicate that the HIV-1 epidemics in Argentina and Brazil are not independent. Therefore, the contemporary HIV-1 epidemic has recombinant lineages of both ancient and more recent origins.
Taken together, we show that these recombinant lineages, which are highly prevalent in the current HIV epidemic, are a mixture of ancient and recent recombination. The HIV pandemic is moving towards having increasing complexity and higher prevalence of recombinant forms, sometimes existing as "families" of related forms. We find that the classification of some CRF designations need to be revised as a consequence of (1) an estimated > 5% error in the original subtype assignments deposited in the Los Alamos sequence database; (2) an increasing number of CRFs are defined while they do not readily fit into groupings for molecular epidemiology and vaccine design; and (3) a dynamic HIV epidemic context.
PMCID: PMC2855530  PMID: 20331894
19.  Recombination and insertion events involving the botulinum neurotoxin complex genes in Clostridium botulinum types A, B, E and F and Clostridium butyricum type E strains 
BMC Biology  2009;7:66.
Clostridium botulinum is a taxonomic designation for at least four diverse species that are defined by the expression of one (monovalent) or two (bivalent) of seven different C. botulinum neurotoxins (BoNTs, A-G). The four species have been classified as C. botulinum Groups I-IV. The presence of bont genes in strains representing the different Groups is probably the result of horizontal transfer of the toxin operons between the species.
Chromosome and plasmid sequences of several C. botulinum strains representing A, B, E and F serotypes and a C. butyricum type E strain were compared to examine their genomic organization, or synteny, and the location of the botulinum toxin complex genes. These comparisons identified synteny among proteolytic (Group I) strains or nonproteolytic (Group II) strains but not between the two Groups. The bont complex genes within the strains examined were not randomly located but found within three regions of the chromosome or in two specific sites within plasmids. A comparison of sequences from a Bf strain revealed homology to the plasmid pCLJ with similar locations for the bont/bv b genes but with the bont/a4 gene replaced by the bont/f gene. An analysis of the toxin cluster genes showed that many recombination events have occurred, including several events within the ntnh gene. One such recombination event resulted in the integration of the bont/a1 gene into the serotype toxin B ha cluster, resulting in a successful lineage commonly associated with food borne botulism outbreaks. In C. botulinum type E and C. butyricum type E strains the location of the bont/e gene cluster appears to be the result of insertion events that split a rarA, recombination-associated gene, independently at the same location in both species.
The analysis of the genomic sequences representing different strains reveals the presence of insertion sequence (IS) elements and other transposon-associated proteins such as recombinases that could facilitate the horizontal transfer of the bonts; these events, in addition to recombination among the toxin complex genes, have led to the lineages observed today within the neurotoxin-producing clostridia.
PMCID: PMC2764570  PMID: 19804621
20.  Adaptive Evolution of Simian Immunodeficiency Viruses Isolated From 2 Conventional Progressor Macaques with Encephalitis 
The Journal of infectious diseases  2008;197(12):1695-1700.
Simian immunodeficiency virus (SIV) infection of macaques may result in encephalitis, a feature more commonly observed in macaques with rapid progressive disease than in those with conventional disease. This is the first report of two conventional progressors (H631 and H636) with encephalitis in rhesus macaques inoculated with a derivative of SIVsmE543-3. Phylogenetic analyses of viruses isolated from the cerebral spinal fluid (CSF) and plasma from both animals demonstrated tissue compartmentalization. Furthermore, these viruses appear to have undergone adaptive evolution to preferentially replicate in their respective cell targets in infectivity assays with monocyte derived macrophages and peripheral blood mononuclear cells. Analysis of the number of potential N-linked glycosylation sites (PNGS) in gp160 showed that there was a statistically significant loss of PNGS in viruses isolated from CNS in both macaques compared to SIVsmE543-3. These viruses provide a relevant model to study the adaptations required for SIV to induce encephalitis.
PMCID: PMC2710246  PMID: 18454679
SIV; neuroAIDS; encephalitis; adaptive evolution; preferential cell tropism; compartmentalization; potential N-linked glycosylation sites
21.  Analysis of the Neurotoxin Complex Genes in Clostridium botulinum A1-A4 and B1 Strains: BoNT/A3, /Ba4 and /B1 Clusters Are Located within Plasmids 
PLoS ONE  2007;2(12):e1271.
Clostridium botulinum and related clostridial species express extremely potent neurotoxins known as botulinum neurotoxins (BoNTs) that cause long-lasting, potentially fatal intoxications in humans and other mammals. The amino acid variation within the BoNT is used to categorize the species into seven immunologically distinct BoNT serotypes (A–G) which are further divided into subtypes. The BoNTs are located within two generally conserved gene arrangements known as botulinum progenitor complexes which encode toxin-associated proteins involved in toxin stability and expression.
Methodology/Principal Findings
Because serotype A and B strains are responsible for the vast majority of human botulism cases worldwide, the location, arrangement and sequences of genes from eight different toxin complexes representing four different BoNT/A subtypes (BoNT/A1-Ba4) and one BoNT/B1 strain were examined. The bivalent Ba4 strain contained both the BoNT/A4 and BoNT/bvB toxin clusters. The arrangements of the BoNT/A3 and BoNT/A4 subtypes differed from the BoNT/A1 strains and were similar to those of BoNT/A2. However, unlike the BoNT/A2 subtype, the toxin complex genes of BoNT/A3 and BoNT/A4 were found within large plasmids and not within the chromosome. In the Ba4 strain, both BoNT toxin clusters (A4 and bivalent B) were located within the same 270 kb plasmid, separated by 97 kb. Complete genomic sequencing of the BoNT/B1 strain also revealed that its toxin complex genes were located within a 149 kb plasmid and the BoNT/A3 complex is within a 267 kb plasmid.
Despite their size differences and the BoNT genes they contain, the three plasmids containing these toxin cluster genes share significant sequence identity. The presence of partial insertion sequence (IS) elements, evidence of recombination/gene duplication events, and the discovery of the BoNT/A3, BoNT/Ba4 and BoNT/B1 toxin complex genes within plasmids illustrate the different mechanisms by which these genes move among diverse genetic backgrounds of C. botulinum.
PMCID: PMC2092393  PMID: 18060065
22.  Preclinical evaluation of MORAb-003, a humanized monoclonal antibody antagonizing folate receptor-alpha 
The highly restricted distribution of human folate receptor-alpha (FRα) in normal tissues and its high expression in some tumors, along with its putative role in tumor cell transformation, make this antigen a suitable target for antigen-specific, monoclonal antibody-based immunotherapy for oncology indications. We have developed a therapeutic humanized monoclonal antibody with high affinity for FRα, named MORAb-003, which was derived from the optimization of the LK26 antibody using a whole cell genetic evolution platform. Here we show that MORAb-003 possesses novel, growth-inhibitory functions on cells overexpressing FRα. In addition, MORAb-003 elicited robust antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) in vitro, and inhibited growth of human ovarian tumor xenografts in nude mice. Because of its multimodal activity in vitro and its safe toxicology profile in non-human primates, MORAb-003 development has recently been advanced to clinical trials involving ovarian cancer patients.
PMCID: PMC2935753  PMID: 17346028
preclinical drug evaluation; monoclonal antibody; folate receptor; antibody-dependent cellular cytotoxicity; complement-dependent cytotoxicity
23.  Kinetic studies of HIV-1 and HIV-2 envelope glycoprotein-mediated fusion 
Retrovirology  2006;3:90.
HIV envelope glycoprotein (Env)-mediated fusion is driven by the concerted coalescence of the HIV gp41 N-helical and C-helical regions, which results in the formation of 6 helix bundles. Kinetics of HIV Env-mediated fusion is an important determinant of sensitivity to entry inhibitors and antibodies. However, the parameters that govern the HIV Env fusion cascade have yet to be fully elucidated. We address this issue by comparing the kinetics HIV-1IIIB Env with those mediated by HIV-2 from two strains with different affinities for CD4 and CXCR4.
HIV-1 and HIV-2 Env-mediated cell fusion occurred with half times of about 60 and 30 min, respectively. Binding experiments of soluble HIV gp120 proteins to CD4 and co-receptor did not correlate with the differences in kinetics of fusion mediated by the three different HIV Envs. However, escape from inhibition by reagents that block gp120-CD4 binding, CD4-induced CXCR4 binding and 6-helix bundle formation, respectively, indicated large difference between HIV-1 and HIV-2 envelope glycoproteins in their CD4-induced rates of engagement with CXCR4.
The HIV-2 Env proteins studied here exhibited a significantly reduced window of time between the engagement of gp120 with CD4 and exposure of the CXCR4 binding site on gp120 as compared with HIV-1IIIB Env. The efficiency with which HIV-2 Env undergoes this CD4-induced conformational change is the major cause of the relatively rapid rate of HIV-2 Env mediated-fusion.
PMCID: PMC1693918  PMID: 17144914
24.  Sensitivity and Specificity of the ViroSeq Human Immunodeficiency Virus Type 1 (HIV-1) Genotyping System for Detection of HIV-1 Drug Resistance Mutations by Use of an ABI PRISM 3100 Genetic Analyzer 
Journal of Clinical Microbiology  2005;43(2):813-817.
The ViroSeq human immunodeficiency virus type 1 (HIV-1) genotyping system is an integrated system for identification of drug resistance mutations in HIV-1 protease and reverse transcriptase (RT). Reagents are included for sample preparation, reverse transcription, PCR amplification, and sequencing. Software is provided to assemble and edit sequence data and to generate a drug resistance report. We determined the sensitivity and specificity of the ViroSeq system for mutation detection using an ABI PRISM 3100 genetic analyzer with a set of clinical samples and recombinant viruses. Twenty clinical plasma samples (viral loads, 1,800 to 10,500 copies/ml) were characterized by cloning and sequencing individual viral variants. Twelve recombinant-virus samples (viral loads, approximately 2,000 to 5,000 copies/ml) were also prepared. Eleven recombinant-virus samples contained drug resistance mutations as 40% mixtures. One recombinant-virus sample contained an insertion at codon 69 in RT (100% mutant). Plasma and recombinant-virus samples were analyzed using the ViroSeq system. Each sample was analyzed on three consecutive days at each of three testing laboratories. The sensitivity of mutation detection was 99.65% for the clinical plasma samples and 99.7% for the recombinant-virus preparations. The specificity of mutation detection was 99.95% for the clinical samples and 100% for the recombinant-virus mixtures. The base calling accuracy of the 3100 instrument was 99.91%. Mutations in clinical plasma samples and recombinant-virus samples were detected with high sensitivity and specificity, including mutations present as mixtures. This report supports the use of the ViroSeq system for identification of drug resistance mutations in HIV-1 protease and RT genes.
PMCID: PMC548107  PMID: 15695685
25.  Human Immunodeficiency Virus Type 1 Genomic RNA Sequences in the Female Genital Tract and Blood: Compartmentalization and Intrapatient Recombination 
Journal of Virology  2005;79(1):353-363.
Investigation of human immunodeficiency virus type 1 (HIV-1) in the genital tract of women is crucial to the development of vaccines and therapies. Previous analyses of HIV-1 in various anatomic sites have documented compartmentalization, with viral sequences from each location that were distinct yet phylogenetically related. Full-length RNA genomes derived from different compartments in the same individual, however, have not yet been studied. Furthermore, although there is evidence that intrapatient recombination may occur frequently, recombinants comprising viruses from different sites within one individual have rarely been documented. We compared full-length HIV-1 RNA sequences in the plasma and female genital tract, focusing on a woman with high HIV-1 RNA loads in each compartment who had been infected heterosexually and then transmitted HIV-1 by the same route. We cloned and sequenced 10 full-length HIV-1 RNA genomes from her genital tract and 10 from her plasma. We also compared viral genomes from the genital tract and plasma of four additional heterosexually infected women, sequencing 164 env and gag clones obtained from the two sites. Four of five women, including the one whose complete viral sequences were determined, displayed compartmentalized HIV-1 genomes. Analyses of full-length, compartmentalized sequences made it possible to document complex intrapatient HIV-1 recombinants that were composed of alternating viral sequences characteristic of each site. These findings demonstrate that the genital tract and blood harbor genetically distinct populations of replicating HIV-1 and provide evidence that recombination between strains from the two compartments contributes to rapid evolution of viral sequence variation in infected individuals.
PMCID: PMC538688  PMID: 15596829

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