Isolation of the outer sheath of Leptospira and its immunogenic properties in hamsters

Cellular Pathophysiology of Leptospirosis: Role of Na/K-ATPase

Inada and Ido identified Leptospira sp. as the pathogen responsible for Weil's Disease in 1915. Later, it was confirmed that Leptospira causes leptospirosis. The host microorganism's interaction at the cellular level remained misunderstood for many years. Although different bacterial components have been isolated and purified, the complexity of the molecular interactions between these components and the host and the molecular mechanisms responsible for the systemic dysfunctions still needs to be fully unveiled. Leptospirosis affects virtually all animal species. Its cellular pathophysiology must involve a ubiquitous cellular mechanism in all eukaryotes. Na/K-ATPase is the molecular target of the leptospiral endotoxin (glycolipoprotein-GLP). Na/K-ATPase dysfunctions on different types of cells give rise to the organ disorders manifested in leptospirosis. Concomitantly, the development of a peculiar metabolic disorder characterized by dyslipidemia, with increased levels of circulating free fatty acids and an imbalance in the fatty acid/albumin molar ratio, triggers events of cellular lipotoxicity. Synergistically, multiple molecular stimuli are prompted during the infection, activating inflammasomes and Na/K-ATPase signalosome, leading to pro-inflammatory and metabolic alterations during leptospirosis. Leptospirosis involves diverse molecular mechanisms and alteration in patient inflammatory and metabolic status. Nonetheless, Na/K-ATPase is critical in the disease, and it is targeted by GLP, its components, and other molecules, such as fatty acids, that inhibit or trigger intracellular signaling through this enzyme. Herein, we overview the role of Na/K-ATPase during leptospirosis infection as a potential therapeutic target or an indicator of disease severity.

Leptospiral Infection, Pathogenesis and Its Diagnosis-A Review

Leptospirosis is a perplexing conundrum for many. In the existing literature, the pathophysiological mechanisms pertaining to leptospirosis is still not understood in full. Considered as a neglected tropical zoonotic disease, leptospirosis is culminating as a serious problem worldwide, seemingly existing as co-infections with various other unrelated diseases, including dengue and malaria. Misdiagnosis is also common as non-specific symptoms are documented extensively in the literature. This can easily lead to death, as the severe form of leptospirosis (Weil's disease) manifests as a complex of systemic complications, especially renal failure. The virulence of Leptospira sp. is usually attributed to the outer membrane proteins, including LipL32. With an armament of virulence factors at their disposal, their ability to easily adhere, invade and replicate within cells calls for a swift refinement in research progress to establish their exact pathophysiological framework. As an effort to reconstitute the current knowledge on leptospirosis, the basis of leptospiral infection, including its risk factors, classification, morphology, transmission, pathogenesis, co-infections and clinical manifestations are highlighted in this review. The various diagnostic techniques are also outlined with emphasis on their respective pros and cons.

Human leptospirosis vaccines in China

The present incidence of leptospirosis in China is significantly lower than past rates, although small localized outbreaks continue to occur in epidemic regions. Improvements in sanitation, as well as vaccination of high-risk populations, have played crucial roles in reducing the disease burden. Several types of human leptospirosis vaccines have been developed, including inactivated whole-cell, outer-envelope, and recombinant vaccines. Of these, only a multivalent inactivated leptospirosis vaccine is available in China, which was added to the Chinese Expanded Program on Immunization in 2007. However, this vaccine elicits serogroup-specific immunity, and serogroup epidemiology should continue to be monitored to enhance vaccine coverage and distribution. On the other hand, the efficiency of the inactivated vaccine should be further improved by optimizing the formulation, and by expanding the target population. More importantly, additional investments should be made to develop universal recombinant vaccines.

Vaccines against leptospirosis

Vaccines against leptospirosis followed within a year of the first isolation of Leptospira, with the first use of a killed whole cell bacterin vaccine in guinea pigs published in 1916. Since then, bacterin vaccines have been used in humans, cattle, swine, and dogs and remain the only vaccines licensed at the present time. The immunity elicited is restricted to serovars with related lipopolysaccharide (LPS) antigen. Likewise, vaccines based on LPS antigens have clearly demonstrated protection in animal models, which is also at best serogroup specific. The advent of leptospiral genome sequences has allowed a reverse vaccinology approach for vaccine development. However, the use of inadequate challenge doses and inappropriate statistical analysis invalidates many of the claims of protection with recombinant proteins.

Immunogenicity of whole cell and outer envelope leptospiral vaccines in hamsters

The immunogenicity of leptospiral whole cell (WC) and outer envelope (OE) vaccines from virulent and avirulent strains was compared in hamsters. The 50% protective dose against death (PD(50D)) and kidney infection (PD(50K)) was evaluated for serotypes icterohaemorrhagiae, canicola, pomona, and grippotyphosa. The OE and WC of virulent strains possessed greater immunogenicity than the OE and WC of avirulent strains. More vaccine (<0.1 to 11.0 mug [dry weight] per hamster) was required for the PD(50K) than for the PD(50D) (<0.1 to 1.7 mug [dry weight] per hamster). The OE from virulent strains of these four serotypes plus hardjo were combined to form a pentavalent OE vaccine which proved to be satisfactory in immunogenic potency. Duration of immunity was not evaluated.

Proteomic strategies to elucidate pathogenic mechanisms of spirochetes

Spirochetes are a unique group of bacteria that include several motile and highly invasive pathogens that cause a multitude of acute and chronic disease processes. Nine genomes of spirochetes have been completed, which provide significant insights into pathogenic mechanisms of disease and reflect an often complex lifestyle associated with a wide range of environmental and host factors encountered during disease transmission and infection. Characterization of the outer membrane of spirochetes is of particular interest since it interacts directly with the host and environs during disease and likely contains candidate vaccinogens and diagnostics. In concert with appropriate fractionation techniques, the tools of proteomics have rapidly evolved to characterize the proteome of spirochetes. Of greater significance, studies have confirmed the differential expression of many proteins, including those of the outer membrane, in response to environmental signals encountered during disease transmission and infection. Characterization of the proteome in response to such signals provides novel insights to understand pathogenic mechanisms of spirochetes.

The shape and dynamics of the Leptospiraceae

Most swimming bacteria produce thrust by rotating helical filaments called flagella. Typically, the flagella stick out into the external fluid environment; however, in the spirochetes, a unique group that includes some highly pathogenic species of bacteria, the flagella are internalized, being incased in the periplasmic space; i.e., between the outer membrane and the cell wall. This coupling between the periplasmic flagella and the cell wall allows the flagella to serve a skeletal, as well as a motile, function. In this article, we propose a mathematical model for spirochete morphology based on the elastic interaction between the cell body and the periplasmic flagella. This model describes the mechanics of the composite structure of the cell cylinder and periplasmic flagella and accounts for the morphology of Leptospiraceae. This model predicts that the cell cylinder should be roughly seven times stiffer than the flagellum. In addition, we explore how rotation of the periplasmic flagellum deforms the cell cylinder during motility. We show that the transition between hook-shaped and spiral-shaped ends is purely a consequence of the change in direction of the flagellar motor and does not require flagellar polymorphism.

The flagellar cytoskeleton of the spirochetes

The recent discoveries of prokaryotic homologs of all three major eukaryotic cytoskeletal proteins (actin, tubulin, intermediate filaments) have spurred a resurgence of activity in the field of bacterial morphology. In spirochetes, however, it has long been known that the flagellar filaments act as a cytoskeletal protein structure, contributing to their shape and conferring motility on this unique phylum of bacteria. Therefore, revisiting the spirochete cytoskeleton may lead to new paradigms for exploring general features of prokaryotic morphology. This review discusses the role that the periplasmic flagella in spirochetes play in maintaining shape and producing motility. We focus on four species of spirochetes: Borrelia burgdorferi, Treponema denticola, Treponema phagedenis and Leptonema (formerly Leptospira) illini. In spirochetes, the flagella reside in the periplasmic space. Rotation of the flagella in the above species by a flagellar motor induces changes in the cell morphology that drives motility. Mutants that do not produce flagella have a markedly different shape than wild-type cells.

Determination of the genus-specific antigens in outer membrane proteins from the strains of Leptospira interrogans and Leptospira biflexa with different virulence

OBJECTIVE

To determine the existence of genus-specific antigens in outer membrane proteins (OMPs) of leptospira with different virulence.

METHODS

Microscope agglutination test (MAT) was applied to detect the agglutination between commercial rabbit antiserum against leptospiral genus-specific TR/Patoc I antigen and 17 strains of Leptospira interrongans belonging to 15 serogroups and 2 strains of Leptospira biflexa belonging to 2 serogroups. The outer envelopes (OEs) of L.interrogans serogroup Icterohaemorrhagiae serovar lai strain lai (56601) with strong virulence and serogroup Pomona serovar pomona strain Luo (56608) with low virulence, and L.biflexa serogroup Semaranga serovar patoc strain Patoc I without virulence were prepared by using the method reported in Auran et al.(1972). OMPs in the OEs were obtained by treatment with sodium deoxycholate. SDS-PAGE and western blot were used for analyzing the features of the OMPs on electrophoretic pattern and the immunoreactivity to the antiserum against TR/Patoc I antigen, respectively.

RESULTS

All the tested strains belonging to different leptospiral serogroups agglutinated to the antiserum against leptospiral genus-specific TR/Patoc I antigen with agglutination titers ranging from 1:256-1:512. A similar SDS-PAGE pattern of the OMPs from the three strains of leptospira with different virulence was shown and the molecular weight of a major protein fragment in the OMPs was found to be approximately 60 KDa. A positive protein fragment with approximately 32 KDa confirmed by Western blot, was able to react with the antiserum against leptospiral genus-specific TR/Patoc I antigen, and was found in each the OMPs of the three stains of leptospira.

CONCLUSION

There are genus-specific antigens on the surface of L.interrogans and L.biflexa. The OMP with molecular weight of 32 KDa may be one of the genus-specific protein antigens of leptospira.

Characterization of the leptospiral outer membrane and description of three novel leptospiral membrane proteins

The outer membrane (OM) of the mammalian pathogen Leptospira kirschneri was isolated in the form of membrane vesicles by alkaline plasmolysis and separated from the protoplasmic cylinder by sucrose density gradient ultracentrifugation. All four components of the alkaline plasmolysis buffer, including 1.0 M NaCl, 27% sucrose (wt/vol), 2 mM EDTA, and 10 mM Tris (pH 9), were required for efficient OM release, as judged by recovery of leptospiral lipopolysaccharide. Two populations of OM vesicles (OMVs) were recovered, with peak concentrations found in the sucrose gradient at densities of 1.16 and 1.18 g/ml. Transmission electron microscopy revealed that the more buoyant OMV population was smaller (<0.1 micro m in diameter) than the denser OMV population (0.2 to 0.3 micro m in diameter). The densities of both populations of OMVs were distinct from that of the protoplasmic-cylinder material, which was found in the sucrose gradient at a density of 1.20 g/ml. The OMV fractions were free of protoplasmic-cylinder material, as judged by immunoblotting with antibodies to the endoflagellar sheath protein, heat shock protein GroEL, and two novel cytoplasmic membrane proteins, lipoprotein LipL31 and transmembrane protein ImpL63. The protein components of the OMVs were characterized by one- and two-dimensional immunoblotting and found to include previously described OM proteins (OMPs), including the porin OmpL1; the lipoproteins LipL32, LipL36, and LipL41; and the peripheral membrane protein P31(LipL45). A number of less well-characterized OMPs were also identified, including those with molecular masses of 16, 21, 21.5, 22, 31, 36, 44, 48, 90, and 116 kDa. The 48-kDa OMP was identified as a novel OM lipoprotein designated LipL48. The use of membrane-specific markers in OM isolation techniques facilitates an accurate description of the leptospiral OM and its components.

Identification of the hemolysis-associated protein 1 as a cross-protective immunogen of Leptospira interrogans by adenovirus-mediated vaccination

New vaccine strategies are needed for the prevention of leptospirosis, a widespread human and animal disease caused by pathogenic leptospires. Our previous work determined that a protein leptospiral extract conferred cross-protection in a gerbil model of leptospirosis. The 31- to 34-kDa protein fraction of Leptospira interrogans serovar autumnalis was shown sufficient for this purpose. In the present study, N-terminal sequencing of a 32-kDa fraction and Southern blotting of genomic DNA with corresponding degenerated oligonucleotide probes identified two of its constituents: hemolysis-associated protein 1 (Hap1) and the outer membrane Leptospira protein 1 (OmpL1). Adenovirus-mediated Hap1 vaccination induces significant protection against a virulent heterologous Leptospira challenge in gerbils, whereas a similar OmpL1 construct failed to protect the animals. These data indicate that Hap1 could be a good candidate for developing a new generation of vaccines able to induce broad protection against leptospirosis disease.

Evidence of cross-protection within Leptospira interrogans in an experimental model

Killed whole-cell preparations were used as bacterins against leptospirosis. As this type of protection is considered to be serogroup-specific, several serogroups were added to the usual vaccines, and the most pathogenic serovar was chosen for each group. Different leptospire extracts were evaluated for their protective capacity against acute lethal leptospirosis in gerbils (Meriones unguiculatus). Total extracts induced complete protection against homologous challenges and partial protection against heterologous challenges. LPS fractions protected against homologous but not heterologous challenges, whereas protein extract induced significant protection against both types of challenge. Thus, cross-protection within L. interrogans was related to the protein extract.

Amino acid sequences of proteins from Leptospira serovar pomona

This report describes a partial amino acid sequences from three putative outer envelope proteins from Leptospira serovar pomona. In order to obtain internal fragments for protein sequencing, enzymatic and chemical digestion was performed. The enzyme clostripain was used to digest the proteins 32 and 45 kDa. In situ digestion of 40 kDa molecular weight protein was accomplished using cyanogen bromide. The 32 kDa protein generated two fragments, one of 21 kDa and another of 10 kDa that yielded five residues. A fragment of 24 kDa that yielded nineteen residues of amino acids was obtained from 45 kDa protein. A fragment with a molecular weight of 20 kDa, yielding a twenty amino acids sequence from the 40 kDa protein.

Identification of a 36-kDa fibronectin-binding protein expressed by a virulent variant of Leptospira interrogans serovar icterohaemorrhagiae

We investigated the ability of a virulent strain of Leptospira interrogans serovar icterohaemorrhagiae, its isogenic avirulent variant and a saprophytic strain to bind fibronectin using alkaline phosphatase-labelled fibronectin. A single 36-kDa fibronectin-binding protein was expressed only by the virulent strain and was located in the outer sheath according to proteinase K treatment results. The interaction of this protein with fibronectin was specific and the region of fibronectin bound to this potential adhesin overlapped the gelatin-binding domain. The inability of a RGDS synthetic peptide to inhibit the binding of fibronectin indicated that the cell-binding domain was not involved in this interaction. Considering the wide distribution of fibronectin within a host and the diversity of mammals involved in the epidemiology of leptospirosis, its implication in the cell attachment process of virulent leptospires is coherent with the multiplicity of target cells.

The leptospiral major outer membrane protein LipL32 is a lipoprotein expressed during mammalian infection

We report the cloning of the gene encoding the 32-kDa lipoprotein, designated LipL32, the most prominent protein in the leptospiral protein profile. We obtained the N-terminal amino acid sequence of a staphylococcal V8 proteolytic-digest fragment to design an oligonucleotide probe. A Lambda-Zap II library containing EcoRI fragments of Leptospira kirschneri DNA was screened, and a 5.0-kb DNA fragment which contained the entire structural lipL32 gene was identified. Several lines of evidence indicate that LipL32 is lipid modified in a manner similar to that of other procaryotic lipoproteins. The deduced amino acid sequence of LipL32 would encode a 272-amino-acid polypeptide with a 19-amino-acid signal peptide, followed by a lipoprotein signal peptidase cleavage site. LipL32 is intrinsically labeled during incubation of L. kirschneri in media containing [(3)H]palmitate. The linkage of palmitate and the amino-terminal cysteine of LipL32 is acid labile. LipL32 is completely solubilized by Triton X-114 extraction of L. kirschneri; phase separation results in partitioning of LipL32 exclusively into the hydrophobic, detergent phase, indicating that it is a component of the leptospiral outer membrane. CaCl(2) (20 mM) must be present during phase separation for recovery of LipL32. LipL32 is expressed not only during cultivation but also during mammalian infection. Immunohistochemistry demonstrated intense LipL32 reactivity with L. kirschneri infecting proximal tubules of hamster kidneys. LipL32 is also a prominent immunogen during human leptospirosis. The sequence and expression of LipL32 is highly conserved among pathogenic Leptospira species. These findings indicate that LipL32 may be important in the pathogenesis, diagnosis, and prevention of leptospirosis.

Leptospiral outer membrane proteins OmpL1 and LipL41 exhibit synergistic immunoprotection

New vaccine strategies are needed for prevention of leptospirosis, a widespread human and veterinary disease caused by invasive spirochetes belonging to the genus Leptospira. We have examined the immunoprotective capacity of the leptospiral porin OmpL1 and the leptospiral outer membrane lipoprotein LipL41 in the Golden Syrian hamster model of leptospirosis. Specialized expression plasmids were developed to facilitate expression of leptospiral proteins in Escherichia coli as the membrane-associated proteins OmpL1-M and LipL41-M. Although OmpL1-M expression is highly toxic in E. coli, this was accomplished by using plasmid pMMB66-OmpL1, which has undetectable background expression without induction. LipL41-M expression and processing were enhanced by altering its lipoprotein signal peptidase cleavage site to mimic that of the murein lipoprotein. Active immunization of hamsters with E. coli membrane fractions containing a combination of OmpL1-M and LipL41-M was found to provide significant protection against homologous challenge with Leptospira kirschneri serovar grippotyphosa. At 28 days after intraperitoneal inoculation, survival in animals vaccinated with both proteins was 71% (95% confidence interval [CI], 53 to 89%), compared with only 25% (95% CI, 8 to 42%) in the control group (P < 0.001). On the basis of serological, histological, and microbiological assays, no evidence of infection was found in the vaccinated survivors. The protective effects of immunization with OmpL1-M and LipL41-M were synergistic, since significant levels of protection were not observed in animals immunized with either OmpL1-M or LipL41-M alone. In contrast to immunization with the membrane-associated forms of leptospiral proteins, hamsters immunized with His(6)-OmpL1 and His(6)-LipL41 fusion proteins, either alone or in combination, were not protected. These data indicate that the manner in which OmpL1 and LipL41 associates with membranes is an important determinant of immunoprotection.

Expression and distribution of leptospiral outer membrane components during renal infection of hamsters

The outer membrane of pathogenic Leptospira species grown in culture media contains lipopolysaccharide (LPS), a porin (OmpL1), and several lipoproteins, including LipL36 and LipL41. The purpose of this study was to characterize the expression and distribution of these outer membrane antigens during renal infection. Hamsters were challenged with host-derived Leptospira kirschneri to generate sera which contained antibodies to antigens expressed in vivo. Immunoblotting performed with sera from animals challenged with these host-derived organisms demonstrated reactivity with OmpL1, LipL41, and several other proteins but not with LipL36. Although LipL36 is a prominent outer membrane antigen of cultivated L. kirschneri, its expression also could not be detected in infected hamster kidney tissue by immunohistochemistry, indicating that expression of this protein is down-regulated in vivo. In contrast, LPS, OmpL1, and LipL41 were demonstrated on organisms colonizing the lumen of proximal convoluted renal tubules at both 10 and 28 days postinfection. Tubular epithelial cells around the luminal colonies had fine granular cytoplasmic LPS. When the cellular inflammatory response was present in the renal interstitium at 28 days postinfection, LPS and OmpL1 were also detectable within interstitial phagocytes. These data establish that outer membrane components expressed during infection have roles in the induction and persistence of leptospiral interstitial nephritis.

Identification of a 35-kilodalton serovar-cross-reactive flagellar protein, FlaB, from Leptospira interrogans by N-terminal sequencing, gene cloning, and sequence analysis

During the screening of antibodies to pathogenic leptospires, a murine monoclonal antibody (designated M138) was found to react with various serovars. An antigen of approximately 35 kDa from Leptospira interrogans serovar pomona, which reacted strongly with M138, was characterized by N-terminal amino acid sequencing and identified as a flagellin, a class B polypeptide subunit (FlaB) of the periplasmic flagella. The gene encoding the FlaB protein, flaB, was amplified from the genomic DNA of several pathogenic serovars by PCR with a single pair of oligonucleotide primers, suggesting that FlaB is highly conserved among these serovars. Cloning and sequence analysis of flaB from serovar pomona revealed that it contains an 849-bp open reading frame with a G + C content of 46.88% which encodes a 283-amino-acid protein with a calculated molecular mass of 31.297 kDa and a predicted pI of 9.065. A sequence comparison of flagellin proteins revealed that the amino acid sequence is most variable in the central portion of the serovar pomona FlaB, which is believed to contain specific sequence information and which may thus be useful in the design of DNA or synthetic peptide probes suitable for the detection of infection with pathogenic leptospires.

Development and initial evaluation of an indirect enzyme-linked immunosorbent assay for the detection of Leptospira interrogans serovar hardjo antibodies in bovine sera

Outer sheath antigen from Leptospira interrogans serovar hardjo type hardjoprajitno and acetic acid extracted antigens from serovar hardjo types hardjoprajitno and hardjobovis were evaluated in an immunoassay for ability to detect hyperimmune rabbit serum to serovar hardjo. The degree of cross-reactivity with hyperimmune rabbit sera to L. interrogans serovars pomona, copenhageni, grippotyphosa, canicola and sejroe, and Leptospira biflexa serovar patoc was also measured for each antigen. All of the antigens reacted with the antiserum to L. interrogans serovar hardjo. The outer sheath antigen however, also showed wide cross-reactivity with the antisera to all of the serovars of L. interrogans tested and with the antiserum to L. biflexa serovar patoc. The acetic acid extracted antigen from either type hardjoprajitno, or type hardjobovis, showed a high degree of specificity for serovar hardjo antiserum. The hardjobovis acetic acid extracted antigen was characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis and immunoblotting, and was incorporated into an indirect ELISA for detection of anti-serovar hardjo antibodies in bovine serum. This ELISA showed a relative specificity of 100% with 156 bovine sera which were negative at a dilution of 1:100 in the microscopic agglutination test (MAT) for L. interrogans serovars hardjo, pomona, sejroe, icterohaemorrhagiae, copenhageni, canicola, and grippotyphosa. The relative sensitivity of this assay with 192 bovine sera which had serovar hardjo MAT titres of > or = 100 was 95.3% (95% confidence limit = 2.99%). The degree of cross-reactivity with 289 bovine sera which had serovar pomona MAT titres of > or = 100 (with no detectable serovar hardjo MAT titres) was approximately 1.0%. This assay was: easily standardized, scored objectively, repeatable, semi-automated and used a non-hazardous antigen that can be routinely prepared in gram amounts.

Molecular cloning and sequence analysis of the gene encoding LipL41, a surface-exposed lipoprotein of pathogenic Leptospira species

We report the cloning of the gene encoding a surface-exposed leptospiral lipoprotein, designated LipL41. In a previous study, a 41-kDa protein antigen was identified on the surface of Leptospira kirschneri (D. A. Haake, E. M. Walker, D. R. Blanco, C. A. Bolin, J. N. Miller, and M. A. Lovett, Infect. Immun. 59:1131-1140, 1991). We obtained the N-terminal amino acid sequence of a staphylococcal V8 proteolytic-digest fragment in order to design an oligonucleotide probe.A Lambda ZAP II library containing EcoRI fragments of L. kirschneri DNA was screened, and a 2.3-kb DNA fragment which contained the entire structural lipL41 gene was identified. The deduced amino acid sequence of LipL41 would encode a 355-amino-acid polypeptide with a 19-amino-acid signal peptide, followed by an L-X-Y-C lipoprotein signal peptidase cleavage site. A recombinant His6-LipL41 fusion protein was expressed in Escherichia coli in order to generate specific rabbit antiserum. LipL41 is solubilized by Triton X-114 extraction of L. kirschneri; phase separation results in partitioning of LipL41 exclusively into the detergent phase. At least eight proteins, including LipL41 and the other major Triton X-114 detergent phase proteins, are intrinsically labeled during incubation of L. kirschneri in media containing [3H] palmitate. Processing of LipL41 is inhibited by globomycin, a selective inhibitor of lipoprotein signal peptidase. Triton X-100 extracts of L. kirschneri contain immunoprecipitable OmpL1 (porin), LipL41, and another lipoprotein, LipL36. However, in contrast to LipL36, only LipL41 and OmpL1 were exposed on the surface of intact organisms. Immunoblot analysis of a panel of Leptospira species reveals that LipL41 expression is highly conserved among leptospiral pathogens.

Immunochemical characteristics and localization on cells of protective antigen (PAg) prepared from Leptospira interrogans serovar lai

Immuno-electron microscopic methods revealed that the protective antigen (PAg) of Leptospira interrogans serovar lai exists on the outer envelope sheathing the leptospiral cell body. PAg lost its protective activity after treatment by hydrolysis with 2 M formic acid at 100 C for 2 hr, or oxidation with periodate at 4 C for 40 hr. The antigenic oligosaccharide fraction was further purified from the hydrolyzed PAg by immunoaffinity column coupled with protective monoclonal antibody, LW2, and by gel filtration of HPLC. The antigenic oligosaccharide fraction contained two unknown sugars and 4-O-methylmannose (molar ratio 3:5:1). These findings suggested that these sugars are components of an antigenic determinant contributing to the protective immunity against serovar lai infection.

Prevalence of Leptospira spp. in wild brown rats (Rattus norvegicus) on UK farms

Wild brown rats (Rattus norvegicus) are frequently implicated in the carriage and spread of Leptospira spp. Wild brown rats (n = 259) were trapped from 11 UK farms and tested for Leptospira spp. using a number of diagnostic tests. The prevalence of leptospiral infection was low, but there was variation in the results obtained with the different diagnostic tests. Estimates of prevalence ranged between 0% by silver-staining of tissues, 1% by the microscopic agglutination test, 4% by the enzyme-linked immunosorbent assay, 4% by culture, and 8% by fluorescent antibody technique. In total, 37 (14%) rats were positive by at least one of the tests, which contrasts with the frequently reported prevalences of 50-70% for wild rats in the UK. Serovar bratislava was a prevalent as icterohaemorrhagiae, although it was present only on farms with larger rat populations.

Characterization of the wheat germ agglutinin-binding property of Treponema denticola

Lectins were used to characterize glycoconjugates on the cell surface of Treponema denticola, a suspected periodontopathogen. Bacteria were first screened by light microscopy using fluorescein isothiocyanate-coupled lectins. Wheat germ agglutinin (WGA) showed a high reactivity to T. denticola. While the WGA-binding activity was accentuated following heating or detergent treatments of bacterial cells, the reaction was inhibited by incorporation of competing carbohydrates. Scanning and transmission electron microscope studies were conducted in order to characterize the distribution of the WGA-binding sites on the cell surface of T. denticola. Data from these studies confirmed that heat treatment increases the percentage of labeled profiles and suggest that the WGA-binding sites are concentrated on specific regions on the spirochete surface. Initial biochemical analysis indicated that the high reactivity to WGA resides in a peptidoglycan fraction.

Assay for measuring relative potency of leptospiral bacterins containing serovar pomona

An enzyme-linked immunosorbent assay (ELISA) was developed for the quantitation of leptospiral antigen in bacterins containing Leptospira interrogans serovar pomona type kennewicki. A monoclonal antibody (MAb), 2D7, which is directed against a surface antigen on whole cells of L. interrogans serovar pomona type kennewicki, was used in the assay. The capture of antigen in bacterins by a polyclonal antiserum was followed by the addition of the 2D7 ascites fluid, an anti-mouse conjugate and substrate. Biologicals evaluated with this system included preparations containing type kennewicki antigen (homologous) and those not containing type kennewicki antigen (heterologous). Heterologous bacterins gave optical density (OD) values comparable to those of blank wells. Homologous bacterins yielded OD values equal to or greater than those of the National Veterinary Services Laboratories (NVSL) reference pomona bacterin. The relative potencies (RP) of 84 licensed commercial Leptospira pomona bacterin serials were evaluated against the NVSL reference pomona bacterin using the NVSL Relative Potency computer program. Random samples of 1, 2, 3 and 5 ml dose products were selected for evaluation with this system. All products tested passed the hamster potency assay required for leptospiral bacterins. This ELISA system enables detection of antigen in bacterins containing L. interrogans serovar pomona type kennewicki and demonstrates the potential for in vitro testing of leptospiral bacterins.

Immunoblotting study of the antigenic relationships among eight serogroups of Leptospira

Seven strains of Leptospira interrogans belonging to seven different serogroups, and one strain of Leptospira biflexa were analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with gradient gels and immunoblotting with hyperimmune rabbit sera raised against each strain. The molecular masses of the proteins were calculated with a polynomial regression model. The SDS-PAGE patterns of the L. interrogans strains were similar and characterized by 24 common bands. This profile was not found for L. biflexa. The immunoblots obtained either with the seven anti-L. interrogans sera or the anti-L. biflexa serum allowed a clear distinction between the two species. Taken as a whole, the L. interrogans strain patterns revealed by the seven anti-L. interrogans sera were similar, sharing eight common major bands. A serovar- or serogroup-specific antigenic zone, ranging from 21 to 26 kDa, was also identified.

The relapsing fever agent Borrelia hermsii has multiple copies of its chromosome and linear plasmids

Borrelia hermsii, a spirochete which causes relapsing fever in humans and other mammals, eludes the immune response by antigenic variation of the "Vmp" proteins. This occurs by replacement of an expressed vmp gene with a copy of a silent vmp gene. Silent and expressed vmp genes are located on separate linear plasmids. To further characterize vmp recombination, copy numbers were determined for two linear plasmids and for the 1-megabase chromosome by comparing hybridization of probes to native DNA with hybridization to recombinant plasmids containing borrelial DNA. Plasmid copy numbers were also estimated by ethidium bromide fluorescence. Total cellular DNA content was determined by spectrophotometry. For borrelias grown in mice, copy numbers and 95% confidence intervals were 14 (12-17) for an expression plasmid, 8 (7-9) for a silent plasmid, and 16 (13-18) for the chromosome. Borrelias grown in broth medium had one-fourth to one-half this number of plasmids and chromosomes. Staining of cells with 4',6-diamidino-2-phenylindole revealed DNA to be distributed throughout most of the spirochete's length. These findings indicate that borrelias organize their total cellular DNA into several complete genomes and that cells undergoing serotype switches do one or more of the following: (1) coexpress Vmps from switched and unswitched expression plasmids for at least three to five generations, (2) suppress transcription from some expression plasmid copies, or (3) partition expression plasmids nonrandomly. The lower copy number of the silent plasmid indicates that nonreciprocal Vmp gene recombination may result from loss of recombinant silent plasmids by segregation.

Protein and antigen profiles of prevalent serovars of Leptospira interrogans

Whole-cell and detergent-soluble proteins, enriched for outer membrane antigens, of the Leptospira interrogans serovars present in commercially available pentavalent vaccines (hardjo, pomona, icterohaemorrhagiae, grippotyphosa, and canicola) were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting (immunoblotting). Protein and antigenic profiles of these serovars, representing several serogroups, were compared with similar profiles of the most common North American bovine pathogen, serovar hardjo type hardjo bovis. The reference strain of serovar balcanica and a hardjoprajitno bovine field isolate (serovar hardjo) were also assayed. Coomassie blue-stained gels revealed extensive protein similarities, and Western blots demonstrated antigenic relatedness throughout the low- and high-molecular-weight regions. Possible quantitative differences in protein expression among the strains were noted, as were similarities in the protein profiles of type hardjo bovis and the balcanica reference strain. A cocktail composed of these homologous antigens may serve as an efficacious subunit vaccine for leptospirosis.

Comparison of protective effects with tetra-valent glycolipid antigens and whole cell-inactivated vaccine in experimental infection of Leptospira

The protective antigens (PAgs), glycolipid substance, were extracted from Leptospira interrogans serovars autumnalis, hebdomadis, australis and copenhageni, which were considered as main causal serovars of human leptospirosis in Japan, with chloroform-methanol-water (1:2:0.8, [vol/vol/vol]) solution. The tetra-valent formalin-inactivated leptospiral vaccine (Weil's disease and Akiyami combined vaccine) composed of the four serovars mentioned are used as vaccine to protect human from leptospiral infection in Japan. The protective effect, agglutinating antibody-inducing activity and opsonin-inducing activity of tetra-valent PAgs were compared with those of vaccines now in use, which were supplied by two companies, Takeda Chemical Industries, Ltd., and Denka-Seiken Co., in Japan. The tetra-valent PAgs which contained 10 micrograms of each PAg protected hamsters and cyclophosphamide-treated mice from lethal infection of serovar copenhageni and induced agglutinating antibodies against the four serovars in the same degrees as vaccines. These results suggested that the tetra-valent PAgs might be useful as a component vaccine against leptospiral infection instead of formalized whole cells vaccines for human.

Biological activities and endotoxic activities of protective antigens (PAgs) of Leptospira interrogans

The biological and endotoxic activities of protective antigens (PAgs) prepared by the chloroform-methanol-water method from Leptospira interrogans serovars lai, copenhageni and canicola were examined. The PAg preparations did not show a local Shwartzman reaction in the rabbits at doses of 100 micrograms and 50 micrograms/site and lethal toxicity to galactosamine-sensitized mice at the dose of 12.5 micrograms to 50 micrograms/mouse. PAgs exhibited a weak cytotoxic action on peritoneal exudate macrophages of C3H/HeJ and C3H/HeN mice at the dose of 500 micrograms/ml in vitro, but did not show cytotoxicity for BHK-21 cells kidney cells of the Syrian hamster, CHO-K1, ovary cells of the Chinese hamster, and CHL, lung cells of the Chinese hamster, at doses of 5 and 500 micrograms/ml. Gelation activity in the Limulus test was only observed at PAg concentrations over 100 ng/ml, which dose was 10,000 times that of lipopolysaccharide (LPS) of Escherichia coli O55:B5. Furthermore, an adjuvant activity of PAgs was not observed in the production of anti-sheep red blood cell antibody in mice. Mitotic conversion of spleen cells from C3H/HeJ and C3H/HeN mice was observed by the addition of PAgs in vitro. These results indicated that the biological properties of PAgs were different from those of LPS prepared from gram-negative enterobacteria, that PAgs had no endotoxic activity and that the biological safety of PAgs as vaccine was proved.

Evaluation of an enzyme immunoassay for diagnosis of bovine leptospirosis caused by Leptospira interrogans serovar hardjo type hardjo-bovis

Sensitivity and specificity of 4 different antigen preparations from Leptospira interrogans serovar hardjo were compared in an enzyme immunoassay for detection of antibodies against serovar hardjo type hardjo-bovis in serum. Two antigens prepared using detergents showed serogroup cross-reactivity. A mechanically extracted membrane and a lipopolysaccharide antigen showed a high degree of leptospiral serogroup specificity. The lipopolysaccharide antigen was the most suitable antigen for detection of anti-hardjo antibodies. Enzyme immunoassay was more sensitive than the microscopic agglutination test for detecting antibodies in serum from experimentally and naturally infected cattle. It was not possible to differentiate vaccinated from infected animals or to detect a secondary immune response in vaccinated animals that were subsequently infected.

Immunological reactivity and passive protective activity of monoclonal antibodies against protective antigen (PAg) of Leptospira interrogans serovar lai

Monoclonal antibody (MAb) AG1 against the protective antigen (PAg) was produced and characterized. It had been extracted from Leptospira interrogans serovar lai by the chloroform-methanol-water method and was of glycolipid nature (23-30Kd). The fact that the PAg was a serogroup-specific antigen was shown by MAb AG1, because MAb AG1 agglutinated serovars of serogroup Icterohaemorrhagiae. Purified MAb LW2 and LW3 which are agglutinating antibodies of serovar lai and AG1 passively protected hamsters from leptospiral infection. Induction of the reactive oxygen intermediates by MAbs from peritoneal exudate macrophages of mice were observed in the chemical luminescence assay and the MAbs reacted with the PAg in the dot enzyme-linked immunosorbent assay. However, MAb LW4a against the genus-specific antigen present in the sub-surface of leptospiral cells did not show protective and reactive-oxygen-inducing activities; they reacted with the non-protective glycolipid antigen of low molecular weight (Fr I, 10-15Kd) in the dot enzyme-linked immunosorbent assay. These results indicated that anti-PAg antibody exhibited opsonic activity against Leptospira and the production of reactive oxygens by macrophages led to leptospiricidal action as one of the defence mechanisms of the host against leptospiral infection. However, the antibody against the genus-specific glycolipid antigen may not be important for protection against leptospiral infection.

Immunological characteristics of the glycolipid antigen of Leptospira interrogans serovar lai

The protective antigen (PAg), a glycolipid substance, was extracted from Leptospira interrogans serovar lai strain 017 with a chloroform-methanol-water (1:2:0.8 [vol/vol/vol]) solution and partially purified by silica gel column chromatography. The PAg was not detected by Coomassie brilliant blue staining in sodium dodecyl sulfate-polyacrylamide gel electrophoresis but was observed as a smearlike band, which corresponded to a 24- to 30-kilodalton standard protein, by silver staining. The outer envelope (OE) fraction showed the same band, suggesting that the PAg was one of the chemical components of the OE. The immunogenicity and protective activity of the PAg were compared with those of the OE. The PAg as well as the OE and whole cells was able to induce agglutinating antibody against L. interrogans. Furthermore, the immune sera exhibited opsonic activity against L. interrogans, as observed by measurement of chemical luminescence derived from reactive oxygen. The PAg exhibited protective activity in hamsters challenged with lethal doses of L. interrogans. Therefore, the antigen may be useful as a component vaccine against leptospiral infection.

Diagnostic specificity, sensitivity and cross-reactivity of an enzyme-linked immunosorbent assay for the detection of antibody against Leptospira interrogans serovars pomona, sejroe and hardjo in cattle

Outer sheath antigen was prepared from Leptospira interrogans serovars pomona, sejroe and hardjo by treating the organisms with 1.0M NaC1 followed by 0.04% sodium dodecyl sulfate (SDS). Sodium dodecyl sulfate was removed from the SDS-protein complexes by the extraction of dodecyl sulfate anions as ion pairs with triethylammonium cations into an organic solvent. The outer sheath antigen was recovered from the organic solvent as a precipitate and used as the source of leptospiral enzyme-linked immunosorbent assay (ELISA) antigen. Utilizing this antigen, ELISA was adapted to detect bovine serum antibody to L. interrogans serovars pomona, sejroe and hardjo. The specificity of this assay in 344 bovine sera, which were negative in the microscopic agglutination test (MAT) for seven serovars, was 99.4%. In sera from 37 and 87 cattle which revealed MAT titers greater than or equal to 1:50 for L. interrogans serovars pomona and sejroe, the relative sensitivity of the test was 100%. The ELISA also showed a considerable degree of low level cross-reactivity with other serovars. Sixty-six (75.9%) out of 87 bovine sera which were MAT-positive (MAT titer of greater than or equal to 1:50) with serovars sejroe and hardjo only were ELISA positive with heterologous pomona antigen; 16 (43.2%) and six 16.2%) out of 37 bovine sera which were MAT positive MAT titer of greater than or equal to 1:50) with serovar pomona only were ELISA positive with heterologous sejroe and hardjo ELISA antigen respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Classification of Leptospira interrogans serovar lai strain 017 by using monoclonal antibodies

Leptospira interrogans serovar lai was identified in China in 1966 as a new serovar of the icterohaemorrhagiae serogroup by cross-absorption tests. In this study, we established three hybridoma cell lines producing monoclonal antibodies (MAbs) of the immunoglobulin G3 subclass (LW1, LW2, and LW3) and of the immunoglobulin M class (LW4a) against serovar lai strain 017 by the cell fusion technique. Immunological reactivities of the MAbs were determined by the microscopic agglutination test, enzyme-linked immunosorbent assay (ELISA), and indirect immunofluorescence assay. MAbs LW1 and LW3 agglutinated cells of serovars lai, birkini, and gem of serogroup icterohaemorrhagiae. LW2 agglutinated various serovars of serogroup icterohaemorrhagiae, except for serovar tonkini. LW4a reacted positively with various Leptospira species, including a new species, Leptospira parva, in the ELISA and indirect immunofluorescence assay. However, LW4a did not react with Leptonema illini 3055. The results of an inhibition ELISA with heated outer envelope (OE) or periodate-oxidized OE suggested that these MAbs recognize a carbohydrate moiety of the OE as the antigenic determinant.

Leptospiral lipopolysaccharide presence in the outer envelope: electrophoretic evidence and immunological specificity

Purified preparations of lipopolysaccharides (LPS) extracted from two different strains of Leptospira interrogans have been electrophoretically analyzed in order to determine their location at the level of outer envelope (OE). Evidence has been collected for the presence of some LPS fractions in the OE, suggesting that a part of this molecule is embedded in the membrane structure. The serological specificity of the LPS has been in addition tested by means of monoclonal antiserovar antibodies (Moabs); the results indicated that the LPS structure is endowed of the immunodeterminants of the serovar. The remarkable relevance of this finding for the Leptospira taxonomy is discussed.

Broad reacting surface antigens in Leptospira biflexa serovar andamana

Previous investigations had demonstrated that genus-specific and species-specific antigens of leptospires are deep-seated within the leptospiral cell. Conversely, the present study has shown that strain CH11, serovar andamana of the non-pathogenic species of Leptospira biflexa is endowed on its surface with two cross-reacting antigens; a newly recognized antigen common to L. interrogans and L. biflexa spp. and an antigenic determinant common to a previously described genus-specific protein antigen (GP-Ag). The serovar andamana, when thimerosal-treated, behaved like an interspecies-specific antigen, cross-reacting in the complement fixation test with sera from rabbits immunized with L. interrogans and L. biflexa spp. and with sera from subjects with leptospirosis from various serovars. In the immuno electron microscopic test, human leptospirotic sera bound to the surface of thimerosal-treated andamana and not to the surface of untreated andamana showing that an interspecies-specific antigen was located underneath the outermost layer of this serovar. In the same test, the monoclonal antibody GP-7 against the GP-Ag bound to the surface of untreated andamana and not to the surface of thimerosal-treated andamana, showing that an antigenic determinant, common to GP-Ag and different from the first one, was located on the outer membrane of andamana. In human leptospirotic sera, antibodies against the cross-reacting antigen of thimerosal-treated andamana demonstrated by the complement fixation test were formed earlier and in a higher percentage of sera than the serovar-specific antibodies against 16 L. interrogans serovars demonstrated by the microagglutination test.

Identification and localization of integral membrane proteins of virulent Treponema pallidum subsp. pallidum by phase partitioning with the nonionic detergent triton X-114

Integral membrane proteins of Treponema pallidum subsp. pallidum (T. pallidum) were identified by phase partitioning with the nonionic detergent Triton X-114; antigens with apparent molecular masses of 47, 38, 36, 34, 32, 17, and 15 kilodaltons (kDa) were identified in the detergent phase. Immunoblotting with murine monoclonal antibodies directed against pathogen-specific 47- and 34-kDa T. pallidum antigens confirmed their presence in the detergent phase. Endoflagellar proteins of T. pallidum were not detected in immunoblots of detergent-phase proteins when monospecific antisera directed against endoflagella of the nonpathogenic T. phagedenis biotype Reiter were used. At detergent concentrations (0.02 and 0.1%) which appeared to solubilize selectively the outer membranes of treponemes radiolabeled with 35S in vitro, limited amounts of detergent-phase proteins were immunoprecipitated. Greater amounts of detergent-phase proteins were extracted at higher detergent concentrations (0.5 and 2.0%) which resulted in both outer membrane solubilization and ultrastructural derangements of the residual cytoplasmic bodies. Furthermore, Triton X-114 extraction of both intact treponemes and organisms without outer membranes yielded detergent phases with similar protein profiles. The results of these experiments indicate that the hydrophobic proteins identified by Triton X-114 are not located exclusively in the T. pallidum outer membrane. The results are also consistent with the hypothesis that the T. pallidum outer membrane is a protein-deficient lipid bilayer.

Isolation of the outer envelope from Borrelia burgdorferi

Borrelia burgdorferi consists of an inner protoplasmic cylinder, containing the genome and cytoplasmic elements, surrounded by a number of axial filaments, all completely encased within a multiple-layered outer envelope structure (OE). In this study, a sodium dodecyl sulfate-mediated technique was used to isolate the OE from Borrelia burgdorferi in an attempt to better understand this structure in terms of its antigenic reactivity to Lyme disease patient sera. Electron microscopic evidence suggested that the OE product was relatively free of other spirochete cellular components. SDS-PAGE analysis indicated that the electrophoretic pattern of the OE was consistent with that of the remaining protoplasmic cylinder (PC) and whole spirochete controls. Antigenic determinants in the OE were recognized by sera from Lyme disease patients in Western blots. Chemical analysis of the OE revealed a composition of 45.90% protein, 50.75% lipid and 3.33% carbohydrate. The OE comprised 16.5% by lyophilized dry weight of the whole spirochete. Antigenic determinants located within or associated with this structure are likely to play a significant role in the development of immunity in the infected host.

Isolation, and structural and chemical characterization of outer sheath carrying a polygonal array from Treponema phagedenis biotype Reiter

An outer sheath was isolated from Treponema phagedenis biotype Reiter by our previously developed method (Masuda, K., and Kawata, T. 1982. J. Bacteriol. 150: 1405-1413). The isolated outer sheath was observed as a triple-layered, closed vesicle carrying a polygonal array by electron microscopy. The outer sheath was mainly composed of protein (41.0%), phospholipid (38.7%), and carbohydrate (11.0%). Sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the isolated outer sheath in the presence of 2-mercaptoethanol (EtSH) gave one major protein band with an apparent molecular weight of about 69,000 and several minor protein bands. On the other hand, in the absence of EtSH, the major protein band disappeared but two new protein bands at positions of molecular weights of about 65,000 and 72,000 appeared. The SDS-PAGE profiles of the minor protein bands did not change with or without EtSH. Sodium deoxycholate (DOC)-solubilized materials from the isolated outer sheath were reassembled into thin membranous sheets carrying a roughly polygonal array upon removal of DOC by dialysis against Tris-HCl buffer in the absence of Mg2+.

Use of enzyme immunoassay in a serological survey of leptospirosis in sheep

A total of 731 serums, all from Merino rams from 20 farms, were tested for antibodies against Leptospira interrogans serovars hardjo, pomona and tarassovi using the microscopic agglutination test (MAT). The enzyme immunoassay (EIA) technique was used to test all serums for IgM and IgG antibodies to serovar hardjo. In the MAT, reactions to serovar hardjo were most common with 236 rams (32.3%) reacting at 1/100 or greater. Only 1.9% of serums reacted against serovar tarassovi and 1.1% against serovar pomona. The percentage of sheep with positive MAT reactions to serovar hardjo ranged from 0 0 to 94.9 between farms. When using EIA, 46 (6.2%) of the serums were positive for IgM antibody and 246 (33.6%) were positive for IgG antibody. Correlation of the EIA for detection of IgG antibody with the MAT was good. The EIA detection of IgG antibody was considered to be a good alternative test to the MAT for epidemiological studies in sheep.

Studies on equine recurrent uveitis. II: The role of infection with Leptospira interrogans serovar pomona

An enzyme linked immunosorbent assay was developed for the detection of immunoglobulin class specific antibodies to Leptospira interrogans serovar pomona in the serum and aqueous humor of horses. Serum antibody was also assayed by microscopic agglutination tests. Although higher levels of antibody were found in sera from horses with signs of uveitis, the association was not statistically significant. Antibodies to pomona were detected in the aqueous of 12 eyes from the 101 horses sampled at a slaughterhouse, and in most instances, a comparison of the aqueous/serum antibody level with that of the total aqueous/serum IgG level indicated intraocular antibody synthesis. Antibodies were also found in 4 aqueous (or vitreous) samples out of 9 obtained from horses with clinically documented uveitis and the above comparison again indicated intraocular antibody synthesis. The data point to an important role for pomona as an etiology of equine recurrent uveitis but also emphasize that the initiating cause for this disease is often obscure in that association with leptospirosis cannot be shown in many instances.

Identification and characterization of the protein antigens of Leptospira interrogans serovar hardjo

We radiolabeled Leptospira proteins with [35S]methionine. Solubilized extracts of radiolabeled L. interrogans serovar hardjo strain hardjoprajitno were analyzed by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. We compared the protein profile obtained in this manner to the protein profiles of various [35S]methionine-labeled Leptospira spp. The profiles of the pathogenic L. interrogans strains were very similar but not identical and exhibited no obvious relationship to those of the two nonpathogenic species. We used solubilized, radiolabeled hardjoprajitno extracts and a sensitive radioimmunoprecipitation procedure to identify protein antigens recognized by immunoglobulin G antibodies present in various rabbit anti-hardjo sera. Homologous hyperimmune rabbit serum efficiently precipitated a large subset of proteins, the majority of which were between 30,000 and 66,500 daltons. Radioimmunoprecipitations with sera prepared against each of four recent hardjo isolates cultured from infected cattle produced similar results. Immunoprecipitations done with various radiolabeled Leptospira extracts and anti-hardjoprajitno serum demonstrated that the pathogenic leptospires possessed a number of cross-reactive major and minor protein antigens. By cell fractionation procedures, we found that most of the major protein antigens were present in the outer envelope. These proteins were exposed on the leptospiral cell surface because intact radiolabeled leptospires bound antibodies directed against them.

Effects of products of autolysis of tissue and urine on the viability, morphology, and antigenicity of Leptospira interrogans serovar pomona

The effect of the products of autolysis on Leptospira interrogans serovar pomona was investigated in bovine kidney tissues and urine inoculated with this organism. No viable leptospires were found at 24 h or subsequently after inoculation of kidney tissues or urine. Leptospires and their soluble antigens were rapidly destroyed in tissues stored at 20 degrees C and could not be detected by the fluorescent-antibody test and the enzyme-linked immunosorbent assay. On the other hand, leptospires were detectable by dark-field microscopy and fluorescent-antibody test 38 days after addition to urine. The rate of destruction proceeded less rapidly in tissues stored at 4 degrees C. Under the conditions of this study, soluble leptospiral antigen levels decreased less rapidly than did the number of detectable leptospires. Similarly, breakdown of leptospires, demonstrated by dark-field microscopy and fluorescent-antibody test, progressed during the first 5 days after inoculation of urine, when levels of soluble leptospiral antigen remained constant. Although the number of intact leptospires was markedly reduced after freezing of tissues at -20 degrees C, soluble leptospiral antigen levels remained unaltered. Neither intact leptospires nor their soluble antigens were detected after preservation of tissues in Formalin. However, formolization of urine delayed the destruction of leptospires and increased the levels of soluble leptospiral antigen during at least the first 5 days after inoculation. These results indicate that assays such as the enzyme-linked immunosorbent assay should be useful for the detection of soluble leptospiral antigens in urine and in autolyzing tissues such as those taken from a bovine fetus aborted as a result of leptospiral infection.

Serodiagnosis of canine leptospirosis by solid-phase enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay (ELISA) to detect antibodies to Leptospira interrogans serotype canicola in dogs was developed and evaluated. Comparison of the ELISA with the microscopic agglutination test (MAT) showed that, during the first two weeks after an experimental infection with serotype canicola, the ELISA detected antibody at higher dilutions than the MAT. After the second week post-infection both tests detected antibody at almost equal titres (r = 0.89). The outer envelope (OE) antigen of serotypes icterohaemorrhagiae, copenhageni and canicola was fairly serotype-specific, whereas the pellet (P) antigen showed more cross-reactivity. Both OE and P antigen of Leptospira biflexa strain Patoc I could be used as cross-reacting antigen in the ELISA. Compared to the MAT, the ELISA has some technical advantages. It is suggested that the ELISA would be useful as a screening test.