Clostridium difficile is the leading cause of antibiotic-associated diarrhea in hospitals worldwide, due to hypervirulent epidemic strains with the ability to produce increased quantities of the large toxins TcdA and TcdB. Unfortunately, accurate quantification of TcdA and TcdB from different toxinotypes using small samples has not yet been reported. In the present study, we quantify C. difficile toxins in <0.1 mL of culture filtrate by quantitative label-free mass spectrometry (MS) using data-independent analysis (MSE). In addition, analyses of both purified TcdA and TcdB as well as a standard culture filtrate were performed using gel-based and gel-independent proteomic platforms. Gel-based proteomic analysis was then used to generate basic information on toxin integrity and provided sequence confirmation. Gel-independent in-solution digestion of both toxins using five different proteolytic enzymes with MS analysis generated broad amino acid sequence coverage (91% for TcdA and 95% for TcdB). Proteomic analysis of a culture filtrate identified a total of 101 proteins, among them TcdA, TcdB, and S-layer proteins.
Determining protein content in biologics is an important part of the production process. An example of interest to public health is the influenza vaccine, where the amount of the major antigenic protein hemagglutinin and the amount of egg proteins from the expression system are regulated. Mass spectrometry has advantages of higher specificity, speed and permits other proteins to be analyzed simultaneously. Here, we present the use of a MRM method for quantitation of hemagglutinin and other vaccine proteins developed in our laboratory and compare this approach to a label free method (MSE) for simultaneous identification and absolute quantitation of virus and egg proteins.
Influenza vaccine samples were tryptically digested using a protocol developed in our laboratory to ensure consistent and reproducible results. Traditional IDMS measurements were made on ThermoFisher Scientific TSQ quantum triple quadrupole platform. Label free methods (LC-MSE) were performed on a Waters qTOF Premier platform and the PLGS software. Both instruments were coupled to an Identical Agilent 1200 LC platform to insure an accurate comparison.
The results of the study illustrated that IDMS remains the gold standard for absolute protein quantitation via mass spectrometry. MSE performed with comparable precision and accuracy in cases where the sample was less complex (monovalent pandemic vaccines vs. seasonal trivalent vaccines). In addition the choice of peptides made by the MSE algorithm and the choice of influenza proteins used in the database also affected the precision and accuracy of the MSE absolute quantitation results.
Botulinum neurotoxins (BoNTs) cause botulism by cleaving proteins necessary for nerve transmission. There are seven serotypes of BoNT, A-G, characterized by their response to antisera. Many serotypes are further distinguished into differing subtypes based on amino acid sequence some of which result in functional differences. Our laboratory previously reported that all tested subtypes within each serotype have the same site of enzymatic activity. Recently, three new subtypes of BoNT/F; /F3, /F4, and /F5, were reported. Here, we report that BoNT/F5 cleaves substrate synaptobrevin-2 in a different location than the other BoNT/F subtypes, between 54L and 55E. This is the first report of cleavage of synaptobrevin-2 in this location.
A non-immune library of human single chain fragment variable (scFv) antibodies displayed on Saccharomyces cerevisiae was screened for binding to the Clostridium botulinum neurotoxin serotype A binding domain [BoNT/A (Hc)] with the goal of identifying scFv to novel epitopes. To do this, an antibody-mediated labeling strategy was used in which antigen-binding yeast clones were selected after labeling with previously characterized monoclonal antibodies (MAbs) specific to the Hc. Twenty unique scFv clones were isolated that bound Hc. Of these, three also bound to full-length BoNT/A toxin complex with affinities ranging from 5 nM to 48 nM. Epitope binning showed that the three unique clones recognized at least two epitopes distinct from one another as well as from the detection MAbs. After production in E. coli, scFv were coupled to magnetic particles and tested for their ability to capture BoNT/A holotoxin using an Endopep-MS assay. In this assay, toxin captured by scFv coated magnetic particles was detected by incubation of the complex with a peptide containing a BoNT/A-specific cleavage sequence. Mass spectrometry was used to detect the ratio of intact peptide to cleavage products as evidence for toxin capture. When tested individually, each of the scFv showed a weak positive Endopep-MS result. However, when the particles were coated with all three scFv simultaneously, they exhibited significantly higher Endopep-MS activity, consistent with synergistic binding. These results demonstrate novel approaches toward the isolation and characterization of scFv antibodies specific to unlabeled antigens. They also provide evidence that distinct scFv antibodies can work synergistically to increase the efficiency of antigen capture onto a solid support.
Affinity reagents; molecular probes; scFv; antibodies; BoNT/A; yeast display
Clostridium botulinum strains that produce botulinum neurotoxin type E (BoNT/E) are most commonly isolated from botulism cases, marine environments, and animals in regions of high latitude in the Northern hemisphere. A strain of C. botulinum type E (CDC66177) was isolated from soil in Chubut, Argentina. Previous studies showed that the amino acid sequences of BoNT/E produced by various strains differ by < 6% and that the type E neurotoxin gene cluster inserts into the rarA operon.
Genetic and mass spectral analysis demonstrated that the BoNT/E produced by CDC66177 is a novel toxin subtype (E9). Toxin gene sequencing indicated that BoNT/E9 differed by nearly 11% at the amino acid level compared to BoNT/E1. Mass spectrometric analysis of BoNT/E9 revealed that its endopeptidase substrate cleavage site was identical to other BoNT/E subtypes. Further analysis of this strain demonstrated that its 16S rRNA sequence clustered with other Group II C. botulinum (producing BoNT types B, E, and F) strains. Genomic DNA isolated from strain CDC66177 hybridized with fewer probes using a Group II C. botulinum subtyping microarray compared to other type E strains examined. Whole genome shotgun sequencing of strain CDC66177 revealed that while the toxin gene cluster inserted into the rarA operon similar to other type E strains, its overall genome content shared greater similarity with a Group II C. botulinum type B strain (17B).
These results expand our understanding of the global distribution of C. botulinum type E strains and suggest that the type E toxin gene cluster may be able to insert into C. botulinum strains with a more diverse genetic background than previously recognized.
Botulism; Mass spectrometry; Genomics; Whole genome sequencing
Botulinum neurotoxins (BoNTs) cause the disease botulism, which can be lethal if untreated. There are seven known serotypes of BoNT, A–G, defined by their response to antisera. Many serotypes are distinguished into differing subtypes based on amino acid sequence, and many subtypes are further differentiated into toxin variants. Previous work in our laboratory described the use of a proteomics approach to distinguish subtype BoNT/A1 from BoNT/A2 where BoNT identities were confirmed after searching data against a database containing protein sequences of all known BoNT/A subtypes. We now describe here a similar approach to differentiate subtypes BoNT/B1, /B2, /B3, /B4, and /B5. Additionally, to identify new subtypes or hitherto unpublished amino acid substitutions, we created an amino acid substitution database covering every possible amino acid change. We used this database to differentiate multiple toxin variants within subtypes of BoNT/B1 and B2. More importantly, with our amino acid substitution database, we were able to identify a novel BoNT/B subtype, designated here as BoNT/B7. These techniques allow for subtype and strain level identification of both known and unknown BoNT/B rapidly with no DNA required.
FigureIdentification of an existing or new BoNT/B can be accomplished through MS/MS analysis of digestion fragments of the protein.
Botulinum neurotoxin; Botulism; Mass spectrometry; Proteomics
Anthrax is caused by infection with Bacillus anthracis, a spore-forming Gram-positive bacterium. A major virulence factor for B. anthracis is an immunomodulatory tripartite exotoxin that has been reported to alter immune cell chemotaxis and activation. It has been proposed that B. anthracis infections initiate through entry of spores into the regional draining lymph nodes where they germinate, grow, and disseminate systemically via the efferent lymphatics. If this model holds true, it would be predicted that surgical removal of infected tissues, debridement, would have little effect on the systemic dissemination of bacteria. This model was tested through the development of a mouse debridement model. It was found that removal of the site of subcutaneous infection in the ear increased the likelihood of survival and reduced the quantity of spores in the draining cervical lymph nodes (cLN). At the time of debridement 12 hours post-injection measurable levels of exotoxins were present in the ear, cLN, and serum, yet leukocytes within the cLN were activated; countering the concept that exotoxins inhibit the early inflammatory response to promote bacterial growth. We conclude that the initial entry of spores into the draining lymph node of cutaneous infections alone is not sufficient to cause systemic disease and that debridement should be considered as an adjunct to antibiotic therapy.
The Bacillus anthracis exosporium protein BclA contains an O-linked antigenic tetrasaccharide whose terminal sugar is known as anthrose (J. M. Daubenspeck et al., J. Biol. Chem. 279:30945–30953, 2004). We hypothesized that serologic responses to anthrose may have diagnostic value in confirming exposure to aerosolized B. anthracis. We evaluated the serologic responses to a synthetic anthrose-containing trisaccharide (ATS) in a group of five rhesus macaques that survived inhalation anthrax following exposure to B. anthracis Ames spores. Two of five animals (RM2 and RM3) were treated with ciprofloxacin starting at 48 hours postexposure and two (RM4 and RM5) at 72 h postexposure; one animal (RM1) was untreated. Infection was confirmed by blood culture and detection of anthrax toxin lethal factor (LF) in plasma. Anti-ATS IgG responses were determined at 14, 21, 28, and 35 days postexposure, with preexposure serum as a control. All animals, irrespective of ciprofloxacin treatment, mounted a specific, measurable anti-ATS IgG response. The earliest detectable responses were on days 14 (RM1, RM2, and RM5), 21 (RM4), and 28 (RM3). Specificity of the anti-ATS responses was demonstrated by competitive-inhibition enzyme immunoassay (CIEIA), in which a 2-fold (wt/wt) excess of carbohydrate in a bovine serum albumin (BSA) conjugate of the oligosaccharide (ATS-BSA) effected >94% inhibition, whereas a structural analog lacking the 3-hydroxy-3-methyl-butyryl moiety at the C-4" of the anthrosyl residue had no inhibition activity. These data suggest that anti-ATS antibody responses may be used to identify aerosol exposure to B. anthracis spores. The anti-ATS antibody responses were detectable during administration of ciprofloxacin.
Cutaneous anthrax outbreaks occurred in Bangladesh from August to October 2009. As part of the epidemiological response and to confirm anthrax diagnoses, serum samples were collected from suspected case patients with observed cutaneous lesions. Anthrax lethal factor (LF), anti-protective antigen (anti-PA) immunoglobulin G (IgG), and anthrax lethal toxin neutralization activity (TNA) levels were determined in acute and convalescent serum of 26 case patients with suspected cutaneous anthrax from the first and largest of these outbreaks. LF (0.005–1.264 ng/mL) was detected in acute serum from 18 of 26 individuals. Anti-PA IgG and TNA were detected in sera from the same 18 individuals and ranged from 10.0 to 679.5 μg/mL and 27 to 593 units, respectively. Seroconversion to serum anti-PA and TNA was found only in case patients with measurable toxemia. This is the first report of quantitative analysis of serum LF in cutaneous anthrax and the first to associate acute stage toxemia with subsequent antitoxin antibody responses.
Clostridium botulinum is the taxonomic designation for at least six diverse species that produce botulinum neurotoxins (BoNTs). There are seven known serotypes of BoNTs (/A through/G), all of which are potent toxins classified as category A bioterrorism agents. BoNT/G is the least studied of the seven serotypes. In an effort to further characterize the holotoxin and neurotoxin-associated proteins (NAPs), we conducted an in silico and proteomic analysis of commercial BoNT/G complex. We describe the relative quantification of the proteins present in the/G complex and confirm our ability to detect the toxin activity in vitro. In addition, we review previous literature to provide a complete description of the BoNT/G complex.
An in-depth comparison of protein sequences indicated that BoNT/G shares the most sequence similarity with the/B serotype. A temperature-modified Endopep-MS activity assay was successful in the detection of BoNT/G activity. Gel electrophoresis and in gel digestions, followed by MS/MS analysis of/G complex, revealed the presence of four proteins in the complexes: neurotoxin (BoNT) and three NAPs--nontoxic-nonhemagglutinin (NTNH) and two hemagglutinins (HA70 and HA17). Rapid high-temperature in-solution tryptic digestions, coupled with MS/MS analysis, generated higher than previously reported sequence coverages for all proteins associated with the complex: BoNT 66%, NTNH 57%, HA70 91%, and HA17 99%. Label-free relative quantification determined that the complex contains 30% BoNT, 38% NTNH, 28% HA70, and 4% HA17 by weight comparison and 17% BoNT, 23% NTNH, 42% HA70, and 17% HA17 by molecular comparison.
The in silico protein sequence comparisons established that the/G complex is phenetically related to the other six serotypes of C. botulinum. Proteomic analyses and Endopep-MS confirmed the presence of BoNT and NAPs, along with the activity of the commercial/G complex. The use of data-independent MSE data analysis, coupled to label-free quantification software, suggested that the weight ratio BoNT:NAPs is 1:3, whereas the molar ratio of BoNT:NTNH:HA70:HA17 is 1:1:2:1, within the BoNT/G progenitor toxin.
Botulinum neurotoxins (BoNTs) cause botulism, which can be fatal if it is untreated. BoNTs cleave proteins necessary for nerve transmission, resulting in paralysis. The in vivo protein target has been reported for all seven serotypes of BoNT, i.e., serotypes A to G. Knowledge of the cleavage sites has led to the development of several assays to detect BoNT based on its ability to cleave a peptide substrate derived from its in vivo protein target. Most serotypes of BoNT can be subdivided into subtypes, and previously, we demonstrated that three of the currently known subtypes of BoNT/F cleave a peptide substrate, a shortened version of synaptobrevin-2, between Q58 and K59. However, our research indicated that Clostridium baratii type F toxin did not cleave this peptide. In this study, we detail experiments demonstrating that Clostridium baratii type F toxin cleaves recombinant synaptobrevin-2 in the same location as that cleaved by proteolytic F toxin. In addition, we demonstrate that Clostridium baratii type F toxin can cleave a peptide substrate based on the sequence of synaptobrevin-2. This peptide substrate is an N-terminal extension of the original peptide substrate used for detection of other BoNT/F toxins and can be used to detect four of the currently known BoNT/F subtypes by mass spectrometry.
A new rapid, mass spectrometry-based method to detect and differentiate botulinal neurotoxins is described.
Botulinum neurotoxins (BoNTs) are proteases that cleave specific cellular proteins essential for neurotransmitter release. Seven BoNT serotypes (A–G) exist; 4 usually cause human botulism (A, B, E, and F). We developed a rapid, mass spectrometry–based method (Endopep-MS) to detect and differentiate active BoNTs A, B, E, and F. This method uses the highly specific protease activity of the toxins with target peptides specific for each toxin serotype. The product peptides derived from the endopeptidase activities of BoNTs are detected by matrix-assisted laser-desorption ionization time-of-flight mass spectrometry. In buffer, this method can detect toxin equivalents of as little as 0.01 mouse lethal dose (MLD)50 and concentrations as low as 0.62 MLD50/mL. A high-performance liquid chromatography–tandem mass spectrometry method for quantifying active toxin, where the amount of toxin can be correlated to the amount of product peptides, is also described.
bioterrorism; botulism; mass spectrometry; botulinum neurotoxin; research
Botulinum neurotoxins (BoNTs) are extremely potent toxins that are capable of causing respiratory failure leading to long-term intensive care or death. The best treatment for botulism includes serotype-specific antitoxins, which are most effective when administered early in the course of the intoxication. Early confirmation of human exposure to any serotype of BoNT is an important public health goal. In previous work, we focused on developing Endopep-MS, a mass spectrometry-based endopeptidase method for detecting and differentiating the seven serotypes (BoNT/A-G) in buffer and BoNT/A, /B, /E, and /F (the four serotypes that commonly affect humans) in clinical samples. We have previously reported the success of antibody-capture to purify and concentrate BoNTs from complex matrices, such as clinical samples. However, to check for any one of the four serotypes of BoNT/A, /B, /E, or /F, each sample is split into 4 aliquots, and tested for the specific serotypes separately. The discovery of a unique monoclonal antibody that recognizes all four serotypes of BoNT/A, /B, /E and /F allows us to perform simultaneous detection of all of them. When applied in conjunction with the Endopep-MS assay, the detection limit for each serotype of BoNT with this multi-specific monoclonal antibody is similar to that obtained when using other serotype-specific antibodies.
Bordetella pertussis (Bp) is the causative agent of pertussis, a vaccine preventable disease occurring primarily in children. In recent years, there has been increased reporting of pertussis. Current pertussis vaccines are acellular and consist of Bp proteins including the major virulence factor pertussis toxin (Ptx), a 5-subunit exotoxin. Variation in Ptx subunit amino acid (AA) sequence could possibly affect the immune response. A blind comparative mass spectrometric (MS) analysis of commercially available Ptx as well as the chemically modified toxoid (Ptxd) from licensed vaccines was performed to assess peptide sequence and AA coverage variability as well as relative amounts of Ptx subunits. Qualitatively, there are similarities among the various sources based on AA percent coverages and MS/MS fragmentation profiles. Additionally, based on a label-free mass spectrometry-based quantification method there is differential relative abundance of the subunits among the sources.
Botulinum neurotoxins (BoNTs) are extremely potent toxins that are capable of causing death or respiratory failure leading to long-term intensive care. Treatment includes serotype-specific antitoxins, which must be administered early in the course of the intoxication. Rapidly determining human exposure to BoNT is an important public health goal. In previous work, our laboratory focused on developing Endopep-MS, a mass spectrometry-based endopeptidase method for detecting and differentiating BoNT/A–G serotypes in buffer and BoNT/A, /B, /E, and /F in clinical samples. We have previously reported the effectiveness of antibody-capture to purify and concentrate BoNTs from complex matrices, such as clinical samples. Because some antibodies inhibit or neutralize the activity of BoNT, the choice of antibody with which to extract the toxin is critical. In this work, we evaluated a panel of 16 anti-BoNT/A monoclonal antibodies (mAbs) for their ability to inhibit the in vitro activity of BoNT/A1, /A2, and /A3 complex as well as the recombinant LC of A1. We also evaluated the same antibody panel for the ability to extract BoNT/A1, /A2, and /A3. Among the mAbs, there were significant differences in extraction efficiency, ability to extract BoNT/A subtypes, and inhibitory effect on BoNT catalytic activity. The mAbs binding the C-terminal portion of the BoNT/A heavy chain had optimal properties for use in the Endopep-MS assay.
Streptococcus pneumoniae (pneumococcus [Pnc]) is a causative agent of many infectious diseases, including pneumonia, septicemia, otitis media, and conjunctivitis. There have been documented conjunctivitis outbreaks in which nontypeable (NT), nonencapsulated Pnc has been identified as the etiological agent. The use of mass spectrometry to comparatively and differentially analyze protein and peptide profiles of whole-cell microorganisms remains somewhat uncharted. In this report, we discuss a comparative proteomic analysis between NT S. pneumoniae conjunctivitis outbreak strains (cPnc) and other known typeable or NT pneumococcal and streptococcal isolates (including Pnc TIGR4 and R6, Streptococcus oralis, Streptococcus mitis, Streptococcus pseudopneumoniae, and Streptococcus pyogenes) and nonstreptococcal isolates (including Escherichia coli, Enterococcus faecalis, and Staphylococcus aureus) as controls. cPnc cells and controls were grown to mid-log phase, harvested, and subsequently treated with a 10% trifluoroacetic acid-sinapinic acid matrix mixture. Protein and peptide fragments of the whole-cell bacterial isolate-matrix combinations ranging in size from 2 to 14 kDa were evaluated by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Additionally Random Forest analytical tools and dendrogramic representations (Genesis) suggested similarities and clustered the isolates into distinct clonal groups, respectively. Also, a peak list of protein and peptide masses was obtained and compared to a known Pnc protein mass library, in which a peptide common and unique to cPnc isolates was tentatively identified. Information gained from this study will lead to the identification and validation of proteins that are commonly and exclusively expressed in cPnc strains which could potentially be used as a biomarker in the rapid diagnosis of pneumococcal conjunctivitis.
New technologies and methods for assessing human exposure to chemicals, dietary and lifestyle factors, infectious agents, and other stressors provide an opportunity to extend the range of human health investigations and advance our understanding of the relationship between environmental exposure and disease. An ad hoc Committee on Environmental Exposure Technology Development was convened to identify new technologies and methods for deriving personalized exposure measurements for application to environmental health studies. The committee identified a “toolbox” of methods for measuring external (environmental) and internal (biologic) exposure and assessing human behaviors that influence the likelihood of exposure to environmental agents. The methods use environmental sensors, geographic information systems, biologic sensors, toxicogenomics, and body burden (biologic) measurements. We discuss each of the methods in relation to current use in human health research; specific gaps in the development, validation, and application of the methods are highlighted. We also present a conceptual framework for moving these technologies into use and acceptance by the scientific community. The framework focuses on understanding complex human diseases using an integrated approach to exposure assessment to define particular exposure–disease relationships and the interaction of genetic and environmental factors in disease occurrence. Improved methods for exposure assessment will result in better means of monitoring and targeting intervention and prevention programs.
body burden; epidemiology; exposure; exposure assessment; exposure technology; geographic information systems; GIS; sensors
Under a mandate from the U.S. Congress, the National Toxicology Program (NTP) of the U.S. Department of Health and Human Services conducts animal bioassays for carcinogenicity of potentially toxic chemicals to which the U.S. population might be exposed. Methyleugenol, a natural as well as synthesized substance, was nominated for study because it is structurally similar to safrole, a known animal carcinogen. Methyleugenol was found to be a very potent multisite carcinogen in male and female F344/N rats and B6C3F1 mice at all doses tested in 2-year NTP bioassays using gavage dosing. For this reason, human toxicokinetic studies were added to the traditional NTP protocol. A commercial brand of gingersnaps was found by chemists at the Centers for Disease Control and Prevention to contain a relatively high concentration of methyleugenol. After thorough scientific and clinical review, and approval by a National Institutes of Health institutional review board for the protection of human subjects, a study was conducted with nine healthy adult male and female human volunteers. The volunteers were given 12 gingersnaps for breakfast. Blood was drawn immediately before the meal and at 15, 30, 60, and 120 min afterward. The mean +/- SD fasting level of methyleugenol in serum was 16.2 +/- 4.0 pg/g wet weight. Peak blood levels were found at 15 min (mean +/- SD, 53.9 +/- 7.3 pg/g wet weight), followed by a rapid decline; the half-life of elimination was about 90 min. The peak levels were within the range of methyleugenol blood levels in the U.S. population, as measured concurrently in a subset of nonfasting participants in the Third National Health and Nutrition Examination Survey (NHANES III).
We have measured 29 pesticides in plasma samples collected at birth between 1998 and 2001 from 230 mother and newborn pairs enrolled in the Columbia Center for Children's Environmental Health prospective cohort study. Our prior research has shown widespread pesticide use during pregnancy among this urban minority cohort from New York City. We also measured eight pesticides in 48-hr personal air samples collected from the mothers during pregnancy. The following seven pesticides were detected in 48-83% of plasma samples (range, 1-270 pg/g): the organophosphates chlorpyrifos and diazinon, the carbamates bendiocarb and 2-isopropoxyphenol (metabolite of propoxur), and the fungicides dicloran, phthalimide (metabolite of folpet and captan), and tetrahydrophthalimide (metabolite of captan and captafol). Maternal and cord plasma levels were similar and, except for phthalimide, were highly correlated (p < 0.001). Chlorpyrifos, diazinon, and propoxur were detected in 100% of personal air samples (range, 0.7-6,010 ng/m(3)). Diazinon and propoxur levels were significantly higher in the personal air of women reporting use of an exterminator, can sprays, and/or pest bombs during pregnancy compared with women reporting no pesticide use or use of lower toxicity methods only. A significant correlation was seen between personal air level of chlorpyrifos, diazinon, and propoxur and levels of these insecticides or their metabolites in plasma samples (maternal and/or cord, p < 0.05). The fungicide ortho-phenylphenol was also detected in 100% of air samples but was not measured in plasma. The remaining 22 pesticides were detected in 0-45% of air or plasma samples. Chlorpyrifos, diazinon, propoxur, and bendiocarb levels in air and/or plasma decreased significantly between 1998 and 2001. Findings indicate that pesticide exposures are frequent but decreasing and that the pesticides are readily transferred to the developing fetus during pregnancy.
During the last several years, illegal commercial application of methyl parathion (MP) in domestic settings in several U.S. Southeastern and Midwestern States has affected largely inner-city residents. As part of a multiagency response involving the U.S. Environmental Protection Agency (U.S. EPA), the Agency for Toxic Substances and Disease Registry (ATSDR), and state and local health departments, our laboratory developed a rapid, high-throughput, selective method for quantifying p-nitrophenol (PNP), a biomarker of MP exposure, using isotope dilution high-performance liquid chromatography-tandem mass spectrometry. We measured PNP in approximately 16,000 samples collected from residents of seven different states. Using this method, we were able to receive sample batches from each state; prepare, analyze, and quantify the samples for PNP; verify the results; and report the data to the health departments and ATSDR in about 48 hr. These data indicate that many residents had urinary PNP concentrations well in excess of those of the general U.S. population. In fact, their urinary PNP concentrations were more consistent with those seen in occupational settings or in poisoning cases. Although these data, when coupled with other MP metabolite data, suggest that many residents with the highest concentrations of urinary PNP had significant exposure to MP, they do not unequivocally rule out exposure to PNP resulting from environmental degradation of MP. Even with their limitations, these data were used with the assumption that all PNP was derived from MP exposure, which enabled the U.S. EPA and ATSDR to develop a comprehensive, biologically driven response that was protective of human health, especially susceptible populations, and included clinical evaluations, outreach activities, community education, integrated pest management, and decontamination of homes.
A novel mass spectral fingerprinting and proteomics approach using MALDI-TOF MS was applied to detect and identify protein biomarkers of group A Streptococcus (GAS) strains. Streptococcus pyogenes ATCC 700294 genome strain was compared with eight GAS clinical isolates to explore the ability of MALDI-TOF MS to differentiate isolates. Reference strains of other bacterial species were also analyzed and compared with the GAS isolates. MALDI preparations were optimized by varying solvents, matrices, plating techniques, and mass ranges for S. pyogenes ATCC 700294. Spectral variability was tested. A subset of common, characteristic, and reproducible biomarkers in the range of 2000–14 000 Da were detected, and they appeared to be independent of the culture media. Statistical analysis confirmed method reproducibility. Random Forest analysis of all selected GAS isolates revealed differences among most of them, and summed spectra were used for hierarchical cluster analysis. Specific biomarkers were found for each strain, and invasive GAS isolates could be differentiated. GAS isolates from cases of necrotizing fasciitis were clustered together and were distinct from isolates associated with noninvasive infections, despite their sharing the same emm type. Almost 30% of the biomarkers detected were tentatively identified as ribosomal proteins.
matrix-assisted laser desorption/ionization time of flight mass spectrometry; biomarkers; protein fingerprints; Streptococcus pyogenes; ribosomal proteins; necrotizing fasciitis
Botulism is caused by botulinum neurotoxins (BoNTs), extremely toxic proteins which can induce respiratory failure leading to long-term intensive care or death. Treatment for botulism includes administration of antitoxins, which must be administered early in the course of the intoxication; therefore, rapid determination of human exposure to BoNT is an important public health goal. In previous work, our laboratory reported on Endopep-MS, a mass spectrometry-based activity method for detecting and differentiating BoNT/A, /B, /E, and /F in clinical samples. We also demonstrated that antibody-capture is effective for purification and concentration of BoNTs from complex matrices such as clinical samples. However, some antibodies inhibit or neutralize the enzymatic activity of BoNT, so the choice of antibody for toxin extraction is critical.
In this work, we evaluated 24 anti-BoNT/B monoclonal antibodies (mAbs) for their ability to inhibit the in vitro activity of BoNT/B1, /B2, /B3, /B4, and /B5 and to extract those toxins. Among the mAbs, there were significant differences in ability to extract BoNT/B subtypes and inhibitory effect on BoNT catalytic activity. Some of the mAbs tested enhanced the in vitro light chain activity of BoNT/B, suggesting that BoNT/B may undergo conformational change upon binding some mAbs.
In addition to determining in vitro inhibition abilities of a panel of mAbs against BoNT/B1-/B5, this work has determined B12.2 and 2B18.2 to be the best mAbs for sample preparation before Endopep-MS. These mAb characterizations also have the potential to assist with mechanistic studies of BoNT/B protection and treatment, which is important for studying alternative therapeutics for botulism.
Chemokines have been found to exert direct, defensin-like antimicrobial activity in vitro, suggesting that, in addition to orchestrating cellular accumulation and activation, chemokines may contribute directly to the innate host response against infection. No observations have been made, however, demonstrating direct chemokine-mediated promotion of host defense in vivo. Here, we show that the murine interferon-inducible CXC chemokines CXCL9, CXCL10, and CXCL11 each exert direct antimicrobial effects in vitro against Bacillus anthracis Sterne strain spores and bacilli including disruptions in spore germination and marked reductions in spore and bacilli viability as assessed using CFU determination and a fluorometric assay of metabolic activity. Similar chemokine-mediated antimicrobial activity was also observed against fully virulent Ames strain spores and encapsulated bacilli. Moreover, antibody-mediated neutralization of these CXC chemokines in vivo was found to significantly increase host susceptibility to pulmonary B. anthracis infection in a murine model of inhalational anthrax with disease progression characterized by systemic bacterial dissemination, toxemia, and host death. Neutralization of the shared chemokine receptor CXCR3, responsible for mediating cellular recruitment in response to CXCL9, CXCL10, and CXCL11, was not found to increase host susceptibility to inhalational anthrax. Taken together, our data demonstrate a novel, receptor-independent antimicrobial role for the interferon-inducible CXC chemokines in pulmonary innate immunity in vivo. These data also support an immunomodulatory approach for effectively treating and/or preventing pulmonary B. anthracis infection, as well as infections caused by pathogenic and potentially, multi-drug resistant bacteria including other spore-forming organisms.
Innate immunity is critical to host defense and plays a central role in protecting the lungs from respiratory pathogens. Among the mediators important in the innate host response to pulmonary infection are chemokines, proteins originally described for their ability to regulate immune cell trafficking during an inflammatory response. More recently, chemokines have been found to exert direct antimicrobial activity against a broad range of bacteria and fungi in vitro. While these observations suggest chemokines may contribute to host defense by killing microorganisms at local sites of infection through activities not associated with cellular chemokine receptors, the biological relevance of direct chemokine-mediated antimicrobial activity in vivo has not been established. Here we show that the murine chemokines CXCL9, CXCL10, and CXCL11 exert direct antimicrobial effects against B. anthracis in vitro and that neutralization of these CXC chemokines, but not their shared receptor CXCR3, increases host susceptibility to pulmonary B. anthracis infection in vivo. These data provide unique insight into the host mediators important in host-pathogen interaction and pathogenesis of disease and support the emerging concept that host chemokines mediate efficient, pleiotropic roles that include receptor-independent promotion of host defense in vivo.
Systemic anthrax manifests as toxemia, rapidly disseminating septicemia, immune collapse, and death. Virulence factors include the anti-phagocytic γ-linked poly-d-glutamic acid (PGA) capsule and two binary toxins, complexes of protective antigen (PA) with lethal factor (LF) and edema factor. We report the characterization of LF, PA, and PGA levels during the course of inhalation anthrax in five rhesus macaques. We describe bacteremia, blood differentials, and detection of the PA gene (pagA) by PCR analysis of the blood as confirmation of infection. For four of five animals tested, LF exhibited a triphasic kinetic profile. LF levels (mean ± standard error [SE] between animals) were low at 24 h postchallenge (0.03 ± 1.82 ng/ml), increased at 48 h to 39.53 ± 0.12 ng/ml (phase 1), declined at 72 h to 13.31 ± 0.24 ng/ml (phase 2), and increased at 96 h (82.78 ± 2.01 ng/ml) and 120 h (185.12 ± 5.68 ng/ml; phase 3). The fifth animal had an extended phase 2. PGA levels were triphasic; they were nondetectable at 24 h, increased at 48 h (2,037 ± 2 ng/ml), declined at 72 h (14 ± 0.2 ng/ml), and then increased at 96 h (3,401 ± 8 ng/ml) and 120 h (6,004 ± 187 ng/ml). Bacteremia was also triphasic: positive at 48 h, negative at 72 h, and positive at euthanasia. Blood neutrophils increased from preexposure (34.4% ± 0.13%) to 48 h (75.6% ± 0.08%) and declined at 72 h (62.4% ± 0.05%). The 72-h declines may establish a “go/no go” turning point in infection, after which systemic bacteremia ensues and the host's condition deteriorates. This study emphasizes the value of LF detection as a tool for early diagnosis of inhalation anthrax before the onset of fulminant systemic infection.