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PubMed1997

Subtyping of Neisseria meningitidis strains isolated in Quebec, Canada: correlation between deduced amino acid sequences and serosubtyping techniques.

Routine serosubtyping of Neisseria meningitidis relies upon reactivity of whole cells to monoclonal antibodies (mAbs). This procedure is limited in providing maximum serosubtype information because some epitopes in whole cells are masked and because mAbs are currently unavailable for some epitopes. To address masking of epitopes in whole cells, we isolated outer membrane vesicles (OMVs) from nine representative meningococcal strains that were isolated (1991-1993) in the province of Quebec, Canada; the OMVs were used in enzyme-linked immunosorbent assay for reactivity to mAbs, and improved serosubtyping information was obtained. A recent proposal assigns subtypes based on deduced amino acid sequences in the variable regions of the class 1 outer membrane protein. This scheme maintains the subtyping nomenclature that is based on reactivity to mAbs by defining the sequences in the epitopes recognized by the mAbs. We used this technique to assign subtypes to the meningococcal strains isolated in Quebec. For the strains tested, serosubtyping using mAbs and subtyping based on deduced amino acid sequences were in complete agreement. Subtyping using deduced amino acid sequences is superior because it does not depend on the availability of mAbs.

Amino Acid Sequence↗
PubMed1988

Antibody response of adults to an aluminum hydroxide-adsorbed Neisseria meningitidis serotype 2b protein-group B polysaccharide vaccine.

A group B Neisseria meningitidis serotype protein vaccine was studied clinically in adults. The vaccine comprised lipopolysaccharide-depleted outer membrane vesicles from a serotype 2b strain, 3006-M2, noncovalently complexed with group B meningococcal polysaccharide. Volunteers received 25 micrograms each of protein and polysaccharide administered intramuscularly either in 0.9% NaCl or adsorbed onto aluminum hydroxide on weeks 0 and 6. Most individuals experienced mild local reactions, but there were no systemic reactions. Both vaccine formulations stimulated antibodies to the outer membrane proteins of serotypes 2a:P1.2 and 2b:P1.2, but higher levels were achieved with the aluminum hydroxide-adsorbed vaccine after two immunizations. Vaccine-induced antibodies were primarily IgG and were bactericidal for both a serotype 2a and a serotype 2b strain. Induction of bactericidal antibodies has been shown to be a major predictor of protection against meningococcal disease.

Adult↗
PubMed1996

T-cell responses to outer membrane proteins of Neisseria meningitidis: comparative study of the Opa, Opc, and PorA proteins.

Former studies have shown that the class 5 outer membranes proteins (Opa and Opc proteins) of Neisseria meningitidis are at least as immunogenic as meningococcal porin proteins. High antibody titers to class 5 proteins have been observed in sera obtained during convalescence after meningococcal infection. A strong increase in anti-class 5 antibodies has also been observed in vaccinees who received a meningococcal outer membrane vesicle preparation. The enhanced B-cell response to class 5 proteins may be due to the presence of immunodominant helper T-cell epitopes in these proteins. In order to investigate this hypothesis, we tested purified Opa, Opc, and class 1 proteins for recognition by human T cells. a hierarchy of T-cell immunogenicity was observed among the outer membrane proteins, the Opa protein being more immunogenic than the other proteins. In most cases, the proliferative responses elicited by Opc were higher than the responses observed for the class 1 protein. The epitopes recognized by the immune T cells were identified by using overlapping synthetic peptides spanning the protein sequences of OpaB, Opa5d, and Opc.

Adult↗
PubMed1984

Comparison of the degradative fate of monoamine oxidase in endogenous and transplanted mitochondrial outer membrane in rat hepatocytes. Implications for the cytomorphological basis of protein catabolism.

The degradative fate of monoamine oxidase in endogenous and transplanted mitochondrial outer membrane has been compared in rat hepatocyte monolayers. Monoamine oxidase was specifically irreversibly radiolabelled by the suicide inhibitor [3H]pargyline. Hepatocyte monolayers were cultured in conditions in which rates of protein catabolism like those in vivo are maintained [Evans & Mayer (1983) Biochem. J. 216, 151-161]. Incubation of hepatocyte monolayers for 17 h with [3H]pargyline specifically radiolabels mitochondrial monoamine oxidase, as shown by Percoll-gradient fractionation of broken hepatocytes. Monoamine oxidase is degraded at a similar rate to that observed in liver in vivo (t1/2 approx. 63 h). The effects of leupeptin, methylamine and colchicine on the degradation of endogenous radiolabelled enzyme has been studied over prolonged culture periods. Culture of hepatocytes for periods of up to 80 h with inhibitors was not cytotoxic, as demonstrated by measurements of several intrinsic biochemical parameters. Leupeptin, methylamine and colchicine inhibit the degradation of endogenous monoamine oxidase by 60, 38 and 18% respectively. Monoamine oxidase in mitochondrial-outer-membrane vesicles introduced into hepatocytes by poly(ethylene glycol)-mediated vesicle-cell transplantation is degraded at a similar rate (t1/2 55 h) to the endogenous mitochondrial enzyme. Whereas leupeptin inhibits the degradation of endogenous and transplanted enzyme to a similar extent, methylamine and colchicine inhibit the degradation of transplanted enzyme to a much greater extent (85 and 56% respectively). Fluorescence microscopy (with fluorescein isothiocyanate-conjugated mitochondrial outer membrane) shows that transplanted mitochondrial outer membrane undergoes internalization and translocation to a sided perinuclear site, as observed previously with whole mitochondria [Evans & Mayer (1983) Biochem. J. 216, 151-161]. The effects of the inhibitors on the distribution of transplanted membrane material in the cell and inhibition of proteolysis show the importance of cytomorphology for intracellular protein catabolism.

Animals↗
PubMed1999

Glycylsarcosine uptake in rabbit renal brush border membrane vesicles isolated from outer cortex or outer medulla: evidence for heterogeneous distribution of oligopeptide transporters.

Studies were initially performed in rabbit brush border membrane vesicles (BBMV) prepared from whole cortex plus outer medulla. In these studies using combined tissues, two distinct peptide/H+transport systems were found for glycylsarcosine (GlySar) uptake, with one representing a low-affinity/high-capacity system (Vm1 = 974 pmol/mg/10 sec and Km1 = 4819 microM) and the other a high-affinity/low-capacity system (Vm2 = 220 pmol/mg/10 sec and Km2 = 96 microM). Thus, under linear conditions, the high-affinity transporter accounted for about 92% of the total transport of dipeptide. To better define the regional heterogeneity of peptide transporter activity in kidney, subsequent studies were performed in vesicles prepared from separately harvested outer cortical and outer medullary tissue. In BBMV studies prepared from outer cortex, two saturable components were revealed for GlySar transport (low-affinity/high-capacity transport system: Vm1 = 1921 pmol/mg/10 sec and Km1 = 11714 microM; high-affinity/low-capacity transport system: Vm2 = 143 pmol/mg/10 sec and Km2= 138 microM). However, in BBMV studies prepared from outer medulla, only one saturable component was revealed for GlySar transport (high-affinity/low-capacity transport system:Vm2= 168 pmol/mg/10 sec and Km2 = 230 microM). Overall, these studies support the contention that peptides are handled sequentially in kidney (ie, first by low-affinity transporter PEPT1, and then by high-affinity transporter PEPT2) and that PEPT2 is primarily responsible for the renal reabsorption of peptides and peptidomimetics.

Animals↗
PubMed1991

Antibodies to outer membrane proteins but not to lipopolysaccharide inhibit pulmonary proliferation of Pasteurella multocida in mice.

The role of rabbit antibodies against Pasteurella multocida outer membrane proteins and lipopolysaccharides (LPS) in resistance remains unknown. Pooled immune sera against P. multocida outer membranes were prepared from specific-pathogen-free rabbits immunized with sucrose gradient-purified P. multocida outer membranes. Western immunoblotting showed that purified outer membrane protein antibodies reacted strongly against the outer membrane proteins but not the purified LPS. Affinity-purified LPS antibodies exhibited strong reactivity against purified LPS and very little reactivity against outer membrane vesicles. Mice were inoculated intranasally with immune serum or normal rabbit serum, challenged intranasally with 10(6) CFU of P. multocida, and euthanatized 48 h later to determine the number of P. multocida organisms in the lungs. Mice inoculated with pooled immune serum had a 3,300-fold reduction (P less than 0.001) in the numbers of P. multocida in the lungs as compared with the controls. Similarly, mice inoculated with purified outer membrane protein antibodies had a 201-fold reduction (P less than 0.001) in the numbers of P. multocida. Conversely, mice inoculated with affinity-purified LPS antibodies had a 1.1-fold reduction (P greater than 0.50) in the numbers of P. multocida. These results show that antibodies against the outer membrane proteins but not the LPS are the components of rabbit immune sera which inhibit P. multocida proliferation in mouse lungs.

Animals↗
PubMed1991

Mitochondrial creatine kinase mediates contact formation between mitochondrial membranes.

Purified mitochondrial creatine kinase (Mi-CK) (EC 2.7.3.2) from chicken heart was shown to interact simultaneously with purified inner and outer mitochondrial membranes, thereby creating an intermembrane chondrial membranes, thereby creating an intermembrane were purified from rat liver and thus were fully devoid of Mi-CK. Intermembrane contact formation was demonstrated by measuring the binding of inner membrane vesicles to outer membranes spread at the air-water interface. Mi-CK also mediated intermembrane adhesion when membranes formed with total lipid extracts of both membranes were used, pointing to the role of lipids as potential membrane anchors of Mi-CK in the mitochondrial intermembrane space. Other enzymes of the intermembrane space that (like Mi-CK) are also cationic, as well as cytosolic isoenzymes of creatine kinase, failed to induce contact formation. Thus, of the proteins tested, membrane contact formation was specific for Mi-CK. The two oligomeric forms of Mi-CK (octamer and dimer) differed in their ability to mediate intermembrane adhesion, the octamer being more potent. Highly basic peptides, i.e. poly-L-lysines, were shown to strongly interact with membranes formed with lipid extracts of mitochondrial membranes: they both induced intermembrane binding and fusion. Interestingly, the extent of contact formation mediated by poly-L-lysines was lower than that of octameric Mi-CK. The implications of these findings on the function and localization of Mi-CK and on the structure of the mitochondrial intermembrane compartment are discussed.

Animals↗
PubMed2002

Meningococcal vaccines.

The successful introduction of a protein-polysaccharide conjugate vaccine against serogroup C meningococci into the UK infant immunization schedule, in combination with a catch-up campaign for individuals less than 18 years of age, has seen virtually all group C disease eliminated in childhood. From being a devastating disease with a very high mortality, the possibility of eradicating invasive meningococcal disease now seems eminently feasible. Since similar technology is likely to facilitate prevention of disease caused be serogroup A, Y and W135 meningococci, the major hurdle in achieving the goal of eradication is development of a safe and immunogenic vaccine against serogroup B infections. Outer membrane vesicle vaccines remain in development and further trials are anticipated. Through the recent availability of the meningococcal genome sequence, many new vaccine candidates are being identified and there is increasing optimism that a solution to the problem can be found.

Animals↗
PubMed1995

Antibody response against Pseudomonas aeruginosa membrane proteins in experimentally infected sheep.

Shedded sheep inoculated epicutaneously with P. aeruginosa and then wetted experimentally by a sprinkler system, rapidly develop a green bacterial stain. This was associated with an outpouring of serious exudates onto the skin surface in the fleecerot lesion site. Histopathological analysis of dermatitic lesions revealed an infiltration of polymorphonuclear leucocytes into the dermis and the formation of a mosaic of microabscesses beneath the sloughed sheets of cornified epithelium. P. aeruginosa if present, was always localized as aggregates at the leading front of the seropurulent exudate and was never observed to invade the dermis. Animals that had been inoculated with P. aeruginosa but kept dry, showed no signs of dermatitis or serological reactivity against the inoculated bacterium. In contrast, sheep that had been inoculated and wetted, reacted serologically against P. aeruginosa whole cells in an enzyme-linked immunosorbent assay (ELISA). Eleven of 18 sheep were considered to be high-antibody responders and registered an ELISA ratio > 2.5 at one or more time points over the duration of the experiment (14 weeks). Analysis of ELISA reactivity of fleecerot sheep against fractionated cell envelope proteins of P. aeruginosa showed a preferential antibody response to outer (OMP) rather than inner (IMP) membrane proteins. Immunoblots revealed strong antibody activity against 2 major OMPs-Opr F and Opr H with apparent molecular masses of 39 and 21 kDa respectively. OMPs prepared from sarkosyl-resistant outer membrane vesicles were electrophoretically identical to OMPs prepared by a more rapid and efficient organic phase partitioning procedure (Chin and Dai, 1990). Although two other OMPs-Opr E (44 kDa) and Opr G (25 kDa) were seen in Coomassie blue-stained SDS-PAGE gels of P. aeruginosa OMPs, they were not reactive with sera from fleecerot affected sheep. It is likely that sheep with high levels of circulating serum antibody against major outer membrane proteins of P. aeruginosa may, in the event of a fleecerot episode, exude such antibodies onto the skin surface. This could provide a strategy for the control of ovine fleecerot by vaccination if highly conserved outer membrane proteins of P. aeruginosa were found to be protective.

Animals↗
PubMed1999

The infant rat model adapted to evaluate human sera for protective immunity to group B meningococci.

The infant rat infection model previously developed to evaluate protective ability of passively administered murine antibodies to group B meningococcal (MenB) surface antigens was adapted for human sera. Several challenge doses were tested, aiming at sensitive detection of protection with little interassay variability. Doses of 10(5) and 10(6) colony forming units of strain IH5341 (MenB:15:P1.7,16) injected intraperitoneally gave consistently high levels of bacteremia and meningitis developed in 6 h in 50-100% of the pups. A monoclonal antibody mAb735 to the MenB capsule, injected 1-2 h before bacterial challenge, gave full protection at a dose of 2 microg/pup. Sera from adult volunteers immunized with a MenB outer membrane vesicle vaccine reproducibly reduced bacterial counts in the blood and cerebrospinal fluid, whereas a normal human serum, lacking bactericidal and opsonophagocidal activity, was unprotective.

Adult↗
PubMed2002

Sequential immunization with vesicles prepared from heterologous Neisseria meningitidis strains elicits broadly protective serum antibodies to group B strains.

The capsular polysaccharide of Neisseria meningitidis group B is an autoantigen, whereas noncapsular antigens are highly variable. These factors present formidable challenges for development of a broadly protective and safe group B vaccine. Mice and guinea pigs were sequentially immunized with three doses of micovesicles or outer membrane vesicles prepared from three meningococcal strains that were each antigenically heterologous with respect to the two major porin proteins, PorA and PorB, and the group capsular polysaccharide. The resulting antisera conferred passive protection against meningococcal group B bacteremia in infant rats and elicited complement-mediated bactericidal activity against genetically diverse group B strains that were either homologous or heterologous with respect to PorA of the strains used to prepare the vaccine. By using knockout strains, a portion of the bactericidal antibody was directed against the highly conserved protein, neisserial surface protein A (NspA). Further, an anti-NspA monoclonal antibody elicited by the sequential immunization was highly bactericidal against strains that were previously shown to be resistant to bacteriolysis by anti-NspA antibodies produced by immunization with recombinant NspA. Sequential immunization with heterologous vesicle preparations offers a novel approach to eliciting broadly protective immunity against N. meningitidis strains. An NspA-based vaccine prepared from protein expressed by Neisseria also may be more effective than the corresponding recombinant protein made in Escherichia coli.

Animals↗
PubMed2001

Protein import channel of the outer mitochondrial membrane: a highly stable Tom40-Tom22 core structure differentially interacts with preproteins, small tom proteins, and import receptors.

The preprotein translocase of the yeast mitochondrial outer membrane (TOM) consists of the initial import receptors Tom70 and Tom20 and a approximately 400-kDa (400 K) general import pore (GIP) complex that includes the central receptor Tom22, the channel Tom40, and the three small Tom proteins Tom7, Tom6, and Tom5. We report that the GIP complex is a highly stable complex with an unusual resistance to urea and alkaline pH. Under mild conditions for mitochondrial lysis, the receptor Tom20, but not Tom70, is quantitatively associated with the GIP complex, forming a 500K to 600K TOM complex. A preprotein, stably arrested in the GIP complex, is released by urea but not high salt, indicating that ionic interactions are not essential for keeping the preprotein in the GIP complex. Under more stringent detergent conditions, however, Tom20 and all three small Tom proteins are released, while the preprotein remains in the GIP complex. Moreover, purified outer membrane vesicles devoid of translocase components of the intermembrane space and inner membrane efficiently accumulate the preprotein in the GIP complex. Together, Tom40 and Tom22 thus represent the functional core unit that stably holds accumulated preproteins. The GIP complex isolated from outer membranes exhibits characteristic TOM channel activity with two coupled conductance states, each corresponding to the activity of purified Tom40, suggesting that the complex contains two simultaneously active and coupled channel pores.

Fungal Proteins↗
PubMed1985

Localization of a sulphate-activating system within Euglena mitochondria.

Intact mitochondria, obtained from Euglena gracilis Klebs var. bacillaris Cori mutant W10BSmL, which lacks plastids, and purified on Percoll density gradients, form adenosine 3'-phosphate 5'-phosphosulphate from sulphate. The optimal conditions include addition of 17 mM-Tricine/KOH, pH 7.6, 18 mM-MgCl2, 250 mM-sucrose, 5.66 mM-sodium ADP (or 0.94 mM-sodium ATP), 1 mM-K2SO4, carrier-free 35SO4(2-) (32.1 microCi) and 1.0 mg of mitochondrial protein in a total volume of 2.65 ml and incubation at 30 degrees C. Experiments with the inhibitor of adenylate kinase P1, P5-di(adenosine 5'-)pentaphosphate indicate that ATP is the preferred substrate for sulphate activation; ADP is utilized by conversion into ATP via adenylate kinase. ATP sulphurylase, adenylylsulphate kinase (APS kinase) and inorganic pyrophosphatase constitute the sulphate-activating system; ADP sulphurylase is undetectable. Fractionation of Euglena mitochondria with digitonin and centrifugation allowed the separation of outer-membrane vesicles and mitoplasts as judged by electron microscopy and selected enzymic markers. The detergent-labile association of the sulphate-activating system with the mitoplasts (similar to that of adenylate kinase), the fact that most of the adenosine 3'-phosphate 5'-phosphosulphate formed by intact mitochondria is found in the surrounding medium, and the ease with which nucleotide substrates reach the activating system in intact organelles, suggest that the enzymes of sulphate activation are located on the outer surface of the mitochondrial inner membrane.

Adenine Nucleotides↗
PubMed1998

Opsonophagocytic and bactericidal activity mediated by purified IgG subclass antibodies after vaccination with the Norwegian group B meningococcal vaccine.

To study how the different immunoglobulin (Ig)G subclass antibodies may confer protection against systemic meningococcal disease, we isolated IgG1, IgG2 and IgG3 antibodies from plasma from vaccinees immunized with the Norwegian meningococcal outer membrane vesicle vaccine. Four IgG1, one IgG2 and four IgG3 preparations were purified. The IgG2 and IgG3 subclass preparations were free from contaminating subclasses, whereas the IgG1 preparations contained from 0 to 14% of IgG2 and/or IgG3. Immunoblotting against whole-cell meningococcal antigens showed broad specificities of the various preparations, both within and between subclasses. These subclass preparations were tested for opsonophagocytic and bactericidal activity. As targets we used two different variants of the meningococcal vaccine strain, with low (44/76-SL) and high (44/76-1) expression of the outer membrane protein Opc. Using polymorphonuclear leucocytes as effector cells in the presence of human complement, all three IgG subclass preparations revealed high, and similar, opsonophagocytic activities against 44/76-SL, whereas against 44/76-1 the IgG2 preparation showed a reduced activity and most IgG3 preparations were slightly more active than the IgG1 preparations. Regarding bactericidal activity, all the three subclasses were highly active against 44/76-SL. Against 44/76-1 the bactericidal activities were somewhat more varied: all IgG1 and three IgG3 preparations exhibited higher activities than against 44/76-SL. Due to the low concentration in the IgG2 preparations, only a weak activity was seen against 44/76-1. One IgG3 preparation that was highly opsonophagocytic revealed no bactericidal activity against either of the two bacterial variants examined. In conclusion, we have shown that the IgG subclass effector functions differ from person to person, but that antibodies of IgG1, IgG2 and IgG3 subclasses, judged by their behaviour in the functional tests, may all contribute to protection against meningococcal disease.

Antibody Specificity↗
PubMed2003

Vesicle-mediated export and assembly of pore-forming oligomers of the enterobacterial ClyA cytotoxin.

The ClyA protein is a pore-forming cytotoxin expressed by Escherichia coli and some other enterobacteria. It confers cytotoxic activity toward mammalian cells, but it has remained unknown how ClyA is surface exposed and exported from bacterial cells. Outer-membrane vesicles (OMVs) released from the bacteria were shown to contain ClyA protein. ClyA formed oligomeric pore assemblies in the OMVs, and the cytotoxic activity toward mammalian cells was considerably higher than that of ClyA protein purified from the bacterial periplasm. The redox status of ClyA correlated with its ability to form the oligomeric pore assemblies. In bacterial cells with a defective periplasmic disulphide oxidoreductase system, the ClyA protein was phenotypically expressed in a constitutive manner. The results define a vesicle-mediated transport mechanism in bacteria, and our findings show that the localization of proteins to OMVs directly may contribute to the activation and delivery of pathogenic effector proteins.

Animals↗
PubMed1995

Mitochondrial protein import: reversible binding of the presequence at the trans side of the outer membrane drives partial translocation and unfolding.

The mechanism of translocation of matrix-targeted, cleavable preproteins across the mitochondrial outer membrane was studied using purified outer membrane vesicles. The N-terminal presequence interacts in a sequential and reversible fashion with two specific binding sites. The first one is provided by protease-sensitive receptors on the surface of the membrane (cis site); the second one is located at the inner face of the outer membrane (trans site). Binding to the trans site drives translocation of the N-terminal portion of the preprotein and, at the same time, unfolding of its mature part. We suggest that the outer membrane protein import machinery forms a translocation channel that permits reversible sliding of preproteins and prevents their lateral aggregation in the membrane. Although translocation can be initiated by the outer membrane, its completion requires coupling to the energetic system of the inner membrane. Our data assign an essential role to the presequence, not only for efficient targeting, but also for the translocation step.

Binding Sites↗
PubMed2006

Characterization of the Moraxella catarrhalis opa-like protein, OlpA, reveals a phylogenetically conserved family of outer membrane proteins.

Moraxella catarrhalis is a human-restricted pathogen that can cause respiratory tract infections. In this study, we identified a previously uncharacterized 24-kDa outer membrane protein with a high degree of similarity to Neisseria Opa protein adhesins, with a predicted beta-barrel structure consisting of eight antiparallel beta-sheets with four surface-exposed loops. In striking contrast to the antigenically variable Opa proteins, the M. catarrhalis Opa-like protein (OlpA) is highly conserved and constitutively expressed, with 25 of 27 strains corresponding to a single variant. Protease treatment of intact bacteria and isolation of outer membrane vesicles confirm that the protein is surface exposed yet does not bind host cellular receptors recognized by neisserial Opa proteins. Genome-based analyses indicate that OlpA and Opa derive from a conserved family of proteins shared by a broad array of gram-negative bacteria.

Amino Acid Sequence↗
PubMed2005

A monoclonal antibody that conveys in vitro killing and partial protection in experimental syphilis binds a phosphorylcholine surface epitope of Treponema pallidum.

Immunization with purified Treponema pallidum outer membrane vesicles (OMV) has previously resulted in high-titer complement-dependent serum bactericidal activity. In this study, OMV immunization resulted in the isolation of a monoclonal antibody, M131, with complement-dependent killing activity. Passive immunization of rabbits with M131 administered intravenously conferred significant immunity demonstrated by the failure of syphilitic lesions to appear at 29% of intradermal challenge sites (7/24) and a mean delay of approximately 8 days to lesion appearance at the remaining sites (17/24). M131 not only bound to OMV and to the surfaces of intact motile T. pallidum cells but also bound to organisms whose outer membranes were removed, indicating both surface and subsurface locations for the killing target. This target was determined to be a T. pallidum lipid. Lipid extracted from T. pallidum and made into liposomes bound M131. Reverse-phase high-pressure liquid chromatography separation and fraction collection mass spectrometry (LC-MS+) of T. pallidum lipid showed that the target of M131 was phosphorylcholine. M131 binding required both liposome formation and a critical concentration of phospholipid containing phosphorylcholine, suggesting that the epitope has both a conformational and a compositional requirement. M131 did not react with red blood cells, which have phosphorylcholine-containing lipids in their exterior membrane leaflets, or with Venereal Disease Research Laboratory antigen that also contains phosphorylcholine, further indicating the specificity of M131. This is the first physical demonstration of an antigen on the T. pallidum surface and indication that such a surface antigen can be a target of immunity.

Animals↗