Serogroup Antigens Research Articles

Reduction of Escherichia coli O157 and non-O157 O groups in the feces of commercial feedlot cattle using a high-dose of NP51, a Lactobacillus-based pre-harvest intervention

Lactobacillus acidophilus strain NP51 is a commercially available direct-fed microbial. This specific direct-fed microbial is recommended by the United States Department of Agriculture, Food Safety and Inspection Service (USDA FSIS) to be a pre-harvest management control and intervention option for the reduction of Escherichia coli (E. coli) O157:H7 in cattle. The addition of NP51 to cattle diets at a dose of 109 /head/day (high dose) has been proven to reduce E. coli O157:H7 and Salmonella in cattle feces. Currently, there has been no research conducted on the impact of feeding NP51 and the reduction of the “Big Six” non-O157 O serogroups which include E. coli O26, O45, O103, O111, O121 and O145 in cattle feces. The purpose of these studies was to evaluate the impact of NP51 fed at a dose of 109/head/day on the reduction of E. coli O157:H7 and six non-O157 O serogroups in cattle feces in two separate cattle feeding studies. Both studies were randomized complete block design. In one study, conducted in a commercial feedlot, approximately 1,800 cattle were blocked by weight and randomized into treatment and control pens. The pens contained 75 head/pen and included 12 control pens and 12 treatment pens. The control pens included cattle not fed NP51 and treatment pens included cattle supplemented with 109 CFU/head/day NP51 (Bovamine Defend®). Twenty-five fecal pats were taken from each pen (n = 600 samples) prior to transport for slaughter. In the research feedlot study, 112 head of cattle were blocked by weight and randomized into treatment or control pens at the Texas Tech University Research Feedlot. The pens included 14 control pens and 14 treatment pens and four head per pen. Fecal grabs were collected from each animal (n = 112 samples) prior to transport for slaughter. All samples were analyzed for the presence E. coli O157 using Immunomagnetic separation (IMS) and the genes that encode for the “Big 6” non-O157 serogroup (E. coli O26, O45, O103, O111, O121 and O145) antigens using a commercially available real time PCR system (BAX Q7, DuPont Qualicon, Wilmington, DE). Quantitative estimates were derived from fecal samples that were positive for E. coli O157 using direct-plating and MPN analysis. Generalized linear mixed models were used to analyze the qualitative data and general linear mixed models were used to analyze the quantitative data. In the commercial feedlot study, a significant (44%) reduction of E. coli O157 in fecal samples was observed when comparing control groups to treatment groups (P = 0.001) in that E. coli O157 was recovered from 15.7% of the treatment cohort and 28.0% of the control cohort. Overall E. coli O157 enumeration resulted in a significant reduction of 0.33 log10 CFU/g when comparing control and treatment groups (P = 0.1). Of the “Big Six” Non-O157 serogroups, results indicated a reduction in O serogroups O26, O45, O103 and O121 with a reduction of 52.7% (P = 0.02), 36.0% (P = 0.001), 33.0% (P = 0.03) and 42.0% (P = 0.02), respectively. In the research feedlot…

Incident Of Leptospirosis Among Cattle And Poultry Workers In Chennai (South India)

A serological survey was carried out in suspected cases of leptospirosis with fever, Jaundice, Myalgia, Diarrhoea, Conjunctival hemorrhage etc in cattle and poultry workers. A total 165 serum samples from male and female individual at different age groups were tested including control. The prevalence data were analyzed in relation to age, sex and sero groups. Of the sample 18.7 % reacted with antigens of different sero groups of titer ranging from 1/40 to 1/1280 with predominance of titer less than (or) equal to 1/160; of positive sera reacted with respective of the autumnalis sero group. Reaction with autumnalis (25.8), hebdomalis (22.5), australis (19.3), pomona, (9.6) grippotyphosa (6.5), copenhageni (9.6) and mixed (6.5) were also detected, through at lower frequencies. The true incidence of the diseases is probably much higher here. Male comprised above (24%) or the cases, the higher rule of infection was in the 20 – 45 years age groups. For female incidence increased with age up to late middle – age. The incidence of disease much higher among cattle and poultry workers.

Differential immunogenicity of Vibrio cholerae O139 variants expressing different combinations of naturally occurring and atypical forms of the serogroup polysaccharide

Field testing of an inactivated bivalent O1/O139 cholera vaccine suggests that Vibrio cholerae O1 is more immunogenic than V. cholerae O139. To investigate whether this might be partly attributable to the production of capsular polysaccharide (CPS) by O139 isolates, we have compared the immunogenicity of variant strains expressing different combinations of lipopolysaccharide (LPS) and CPS. These studies indicate that the core-linked LPS structure is of paramount importance for induction of antibodies to the serogroup antigen. By contrast CPS was minimally immunogenic. Significantly the presence of CPS did not modulate the immunogenicity of the underlying LPS. To examine whether differences in LPS structure might contribute to the differing immunogenicities of the O1 and O139 serogroups, an attempt was made to modify the normal O139 LPS structure by provision of one of several heterologous wzz genes. The resulting variants displayed additional, atypical surface polysaccharide, whose modal length was characteristic for the particular wzz gene. By immunoblotting this novel material showed a ladder-like banding pattern typical of LPS, but its failure to be stained by silver indicated that it was not core-associated and was therefore more like truncated CPS. Consistent with our earlier findings, studies using systemic or mucosal routes of immunization failed to demonstrate any consistent enhancement of antibody responses associated with production of these aberrant polysaccharide polymers.

Characterization of Neisseria meningitidis strains isolated from invasive meningococcal disease cases in Canada in 2001.

With the recent introduction of polysaccharide-protein conjugated vaccines for the control of serogroup C meningococcal disease and the emergence of different variants of serogroup C meningococci, it is likely the epidemiology of meningococcal disease in many countries may be affected. We have therefore analysed and reported the characteristics of Neisseria meningitidis strains collected in 2001 from the Canadian surveillance program on invasive meningococcal disease. Only strains collected from normally sterile clinical sites of patients were studied. Of the 289 isolates obtained from individual patients, 173 (59.9%) were serogroup C, 76 (26.3%) were serogroup B, 30 (10.4%) were serogroup Y, and 10 (3.5%) were serogroup W135. Ninety-six percent of the serogroup C isolates belonged to the ET-15 clone, with an additional 2.3% belonging to other electrophoretic types within the ET-37 clonal complex. Different antigenic variants of the endemic serogroup C ET-15 clone were responsible for localized outbreaks in different parts of the country. One novel variant with the antigenic composition of C:2a:P1.1,7 was reported in two provinces, Quebec and Ontario. Eighteen percent of the meningococci isolated from patients in Ontario belonged to serogroup Y, compared with only 8% in the rest of Canada. The current data highlight the importance of strain characterization by serogroup, serotype, and serosubtype antigens in providing useful information for the surveillance of meningococcal disease in Canada.

Serum IgG3 to the Plasmodium falciparum merozoite surface protein 2 is strongly associated with a reduced prospective risk of malaria.

The merozoite surface protein 2 (MSP2) of Plasmodium falciparum is recognized by human antibodies elicited during natural infections, and may be a target of protective immunity. In this prospective study, serum IgG antibodies to MSP2 were determined in a cohort of 329 Gambian children immediately before the annual malaria transmission season, and the incidence of clinical malaria in the following 5 months was monitored. Three recombinant MSP2 antigens were used, representing each of the two major allelic serogroups and a conserved region. The prevalence of serum IgG to each antigen correlated positively with age and with the presence of parasitaemia at the time of sampling. These antibodies were associated with a reduced subsequent incidence of clinical malaria during the follow-up. This trend was seen for both IgG1 and IgG3, although the statistical significance was greater for IgG3, the most common subclass against MSP2. After adjusting for potentially confounding effects of age and pre-season parasitaemia, IgG3 reactivities against each of the major serogroups of MSP2 remained significantly associated with a lower prospective risk of clinical malaria. Individuals who had IgG3 reactivity to both of the MSP2 serogroup antigens had an even more significantly reduced risk. Importantly, this effect remained significant after adjusting for a simultaneous strong protective association of antibodies to another antigen (MSP1 block 2) which itself remained highly significant.

Enzyme-Linked Immunosorbent Assay forSalmonellaSerology using Lipopolysaccharide Antigen

Enzyme-linked immunosorbent assay (ELISA) using Salmonella lipopolysaccharide (LPS) to measure specific IgG titers in cattle has proven useful. Serology can be used to assess vaccine responses and infection rates, to detect carriers, and to aid in epidemiologic studies. The objective of this study was to assess cross-reactions using sera from cattle vaccinated with different Salmonella serogroups. ELISA plates using lipopolysaccharide from serogroup B, C1, C3, D1 or E1 as the plate antigens were tested. LPS was extracted from Salmonella typhimurium (Serogroup B; somatic antigens 01, 4, 12), S. montevideo (C1; 06, 7), S. kentucky (C3; 08, 20), S. dublin (D1; 01, 9, 12) and S. anatum (E1; 03, 10) using the Westphal method. Fifteen cows were found to be seronegative for all 5 of these serogroup antigens. Each cow was then vaccinated 3 times at 2-week intervals with a killed Salmonella bacterin. The 15 different serotypes used for vaccination were chosen to represent a wide array of Salmonella serogroups with a wide array of somatic "O" antigens expressed, including somatic antigens 1, 2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 18, 19, 20, 22, 23, 25, and 27. With each antigen tested, the highest ELISA titers were seen with sera from cattle vaccinated with homologous O antigens, indicating that reactions were highly O antigen-specific. Some cross reactions between subgroups sharing one O factor antigen were found; these titers were lower than those found with homologous serogroups sharing 2 or more antigens. Only serum from the cow vaccinated from S. anatum (group E; antigens 03, 10) cross-reacted at a low titer with group C1 (O somatic antigens 6, 7) and D1 (O somatic antigens 1, 9, 12) plate antigens, with which no somatic antigens were shared. We conclude from these results that Salmonella serology using LPS antigens is highly O antigen-specific and predictable.

The Vibrio cholerae O139 serogroup antigen includes an O-antigen capsule and lipopolysaccharide virulence determinants.

Vibrio cholerae serogroup O139 emerged on the Indian subcontinent in October 1992 to become the first non-O1 V. cholerae serogroup documented to cause epidemic cholera. Although related to V. cholerae El Tor O1 strains, O139 strains have unique surface structures that include a capsular surface layer and lipopolysaccharide (LPS). Immunoblot analysis of either whole-cell lysates or LPS preparations revealed three electrophoretic forms of the O139 antigen: two slowly migrating forms and one rapidly migrating form that appeared identical to O139 LPS. All three forms of the antigen shared an epitope defined by an O139-specific monoclonal antibody. A serum-sensitive nonencapsulated mutant was isolated that lacks only the slow migrating forms. The slow migrating forms did not stain with silver whereas the rapidly migrating form did, suggesting that the former might constitute highly polymerized O-antigen side-chain molecules that were not covalently bound to core polysaccharide and lipid A (an "O-antigen capsule"). A single transposon insertion resulted in the loss of immunoreactivity of both the LPS and the O-antigen capsule, implying that there are genes common to the biosynthesis of both these macromolecules. The O139 LPS and O-antigen capsule were both important for colonization of the small intestine of the newborn mouse and for serum resistance, demonstrating that both of these forms of the O139 serogroup antigen are virulence factors.

Antigenic competition in a multivalent foot rot vaccine

The antigenic competition that occurs when pilus antigens of different serogroups are combined in multivalent vaccines for foot rot has been investigated using recombinant pilus antigens. Our prototype vaccine contains pili from nine serogroups of Dichelobacter nodosus which are expressed in Pseudomonas aeruginosa. Sheep inoculated with this multivalent vaccine were not as well protected against foot rot as those given the monovalent vaccine. Levels of agglutinating and total antibody specific for any particular pili serogroup were found to be significantly reduced in sheep vaccinated with six or more closely related pili. This effect was more pronounced for agglutinating antibody, which is thought to mediate protection, but was also observed with total antibody levels measured by ELISA. The antigenic competition was not associated with the total antigen load as a tenfold higher dose of monovalent pili induced high titres of antibody. Furthermore, distributing the vaccine to four sites, each draining to a different lymph node, failed to overcome the competition. Experiments with mixtures of monospecific sera indicate that the phenomenon is unlikely to be due to blocking of serogroup-specific protective antibodies by an excess of cross-reactive non-protective antibody elicited by heterologous pili.

Salmonella serogroups C2 and C3 identified by agglutination using an immunoglobulin G3(kappa) monoclonal antibody (32-1-E3) reactive with a somatic factor 8-like polysaccharide antigen.

An immunoglobulin G3(kappa) monoclonal antibody (MAb), MAb 32-1-E3, which was prepared in BALB/c mice by using a heated, alcohol-acetone-extracted Salmonella newport CDC 50 antigen, reacted with protein-free lipopolysaccharides from Salmonella groups C2 (O:6,8) and C3 (O:-,8) but not with those from any other serogroup tested. Sodium periodate did not inhibit antigen reactivity, which was consistent with its identity as the abequose-containing disaccharide O:8 antigen. Reactivity was inhibited by competition with serogroup C2 (O:6,8) and C3 (O:-,8) antigens but not with non-O:8 antigens. Reactivity was also inhibited by preincubation of the antigen with polyclonal rabbit antiserogroup C2 or C3 antibodies but not with antisera to serogroup C1 or other Salmonella serogroups. The MAb agglutinated with all strains of Salmonella serogroups C2 and C3 tested but not with other bacteria. Agglutination was inhibited by preabsorbing the MAb with either of two serogroup C3 Salmonella strains, S. virginia CDC 189 or S. haardt MDL 83A4545, which contain only O:8, but not by preabsortion with O:8-negative S. cholerasuis MDL 81A7623 (group C1; O:6,7), S. paratyphi type B CDC 157 (group B; O:1,[4],5,12), or Escherichia coli (O:157) (which contains no Salmonella serogroup antigens). The MAb reacted strongly (4+ agglutination) with all 140 wild-type strains of group C2 and C3 Salmonella spp. tested and showed no reaction with any of 1,324 wild-type strains of non-C2 or non-C3 Salmonella spp. tested. The MAb is useful as a replacement for absorbed, polyclonal, single-factor O:8 antiserum to discriminate Salmonella serogroups C2 and C3 from serogroup C1.

The protective efficacy of pili from different strains of Moraxella bovis within the same serogroup against infectious bovine keratoconjunctivitis

Three groups of ten calves were each immunised with a total of 400 μg pili prepared from three separate strains of Moraxella bovis in Alhydrogel-oil adjuvant as two divided, equal doses 21 days apart. Groups 1 and 2 each received a monovalent vaccine made from strain 4L and S276R respectively, which belonged to pili serogroup A. Group 3 received vaccine made from pili of strain Maff1, belonging to serogroup F. A further group of ten calves served as non-vaccinated controls. Calves in groups 1 and 2 had developed serogroup A-specific antibody and those in group 3 developed serogroup F-specific antibody, and some evidence of cross-reacting antibody was also detected when measured by an agglutination test using formalin-killed piliated cells of serogroup A strain 4L. Although antibody titres measured against purified pili by ELISA were highest with homologous serogroup antigens, cross-reactive titres to shared epitopes of M. bovis pili were also detected by this method. Occular challenge of the 40 calves with virulent M. bovis of serogroup A strain S276R was carried out 14 days after the second vaccine dose. All non-vaccinated calves developed infectious bovine keratoconjunctivitis (IBK). The percentage protection in groups 1 (strain 4L) and 2 (strain S276R) was 60% and 80% respectively ( P<0.05), with mean lesion scores of 0.7 and 0.3 out of a possible 6.0. The percentage protection of calves in group 3 (strain Maff1) was only 30%, with a mean lesion score of 1.4 compared with 2.2 for non-vaccinated controls. The present findings, together with other evidence indicating that immunity to IBK is serogroup-specific, suggest that inclusion of pili from one representative strain from each of the seven Australian and British serogroups in a polyvalent, subunit vaccine should effectively protect the majority of cattle against IBK caused by most field strains of M. bovis encountered in Australia and the United Kingdom.

Muskrats as carriers of pathogenic leptospires in The Netherlands.

Leptospires were isolated from 24 of 327 (7%) muskrats (Ondatra zibethicus) caught in The Netherlands. All isolates were identified as Leptospira interrogans. One isolate was typed as serovar copenhageni in the Icterohaemorrhagiae serogroup, one as serovar lora in the Australis serogroup. Twenty-one isolates showed a close relationship with serovars grippotyphosa, valbuzzi, muelleri and ratnapura from the Grippotyphosa serogroup. One isolate was lost. Sera from 196 muskrats were examined by the microscopic agglutination test. Forty-five (23%) sera reacted positively (titers greater than or equal to 1:160), 42 (21%) of these 45 sera to Grippotyphosa and 3 (2%) to Sejroe serogroup antigens. This is the first report of serological and cultural evidence of leptospira infection in muskrats in The Netherlands.

Molecular cloning and comparative sequence analyses of bluetongue virus S1 segments by selective synthesis of specific full-length DNA copies of dsRNA genes

Using primers complementary to the conserved sequences of the 3′ ends of bluetongue virus genomic dsRNA segments, full-length DNA clones of all 10 dsRNA genes from the five U.S. BTV serotypes were synthesized and amplified by a novel method (CIampR). This amounts to nearly 100,000 base pairs of dsRNA cloned as unique full-length DNA copies. This continuous one-tube procedure combined cloning of the denatured dsRNA with reverse transcriptase and the selective amplification of full-length DNA by the polymerase chain reaction. CIampR-derived clones of the genomic segment S1 of BTV-11 encoding the serogroup antigen, VP7, were sequenced and shown to be complete copy, containing a total of 1156 by and a long open reading frame of 349 amino acids. Comparative sequence analyses of BTV-11 S1 with those of the other U.S. serotypes show that 95.2% of the nucleotides are conserved between BTV-11 and -10, while only 79.0% of the bases are identical between BTV-11 and -13. Comparison of the VP7 proteins demonstrates that 100% of the amino acids are conserved between BTV-11 and -10 and 93.7% of these residues are identical between VP7 of BTV-11 and -13. The adaptation of the polymerase chain reaction to the full-length cloning and amplification of dsRNA (CIampR) should greatly facilitate molecular studies within the Reoviridae family.

Human leptospirosis in a slum area in the city of Rio de Janeiro, Brazil: a serological and epidemiological study

A serologic survey was carried out on slum dwellers in the city of Rio de Janeiro. A total of 259 serum samples from male and female individuals of different age groups were tested for the presence of antileptospire antibodies by microagglutination. Prevalence data were analyzed in relation to the major risk factors present at the site, mainly represented by the presence of carrier animals and the occurrence of frequent floods. Of the samples tested, 25% reacted with antigens of different serogroups at titres ranging from 1:100 to 1:6400, with a predominance of titres less than or equal to 1:400; 35% of positive sera reacted with leptospirae of the Icterohaemorrhagiae serogroup. Reactions with Djasiman, Panama, Javanica, Canicola, Pyrogenes, Australis, Ballum, Sejroe, Bataviae, Grippotyphosa, Autumnalis and Cynopteri were also detected, though at lower frequencies. There was no statistically significant difference between sexes, but higher prevalence rates were found to be associated with increasing age. A focus of infection was characterized, in which social and economic factors contribute to the persistence of leptospirae by favoring the proliferation of the main reservoir.

Similar DNA restriction endonuclease profiles in strains of Legionella pneumophila from different serogroups.

DNA of strains of Legionella pneumophila serogroups 1, 3, 4, and 6, isolated from patients and environmental sources, was examined by restriction endonuclease analysis (REA). Major differences in profiles enabled subtyping in many strains with the same serogroup antigen. However, a cluster of L. pneumophila strains, originating from all the examined serogroups, had similar restriction endonuclease profiles, sometimes with minor differences. This suggests that the genetic similarity between strains of L. pneumophila of different serogroups is sometimes closer than in strains with the same serogroup antigen. Seven environmental sources harbored two L. pneumophila strains with various serogroup antigens; six sources had similar restriction endonuclease profiles. The resolution of small differences in profiles is hampered in REA by the great magnitude of DNA fragments; even upon extensive analysis, these differences are not always readily visualized. Double digestions with the restriction enzymes HpaI and HpaII showed the best results and sometimes revealed differences not evident by digestions with a single endonuclease. REA has a great capacity for accurate epidemiological typing of L. pneumophila, in addition to classical serogrouping; it appeared that the results of the two techniques do not necessarily correlate. On the other hand, it should be stressed that small differences in profiles are not easily detected by REA.

Serogrouping single colonies of beta-hemolytic streptococci with achromopeptidase extraction

Achromopeptidase (TBL-1; Wako Chemicals, USA, Inc., Dallas, Tex.) prepared as a 2,000-U/ml solution will extract the serogroup antigens from single colonies of groups A, B, C, F, and G streptococci in 1 min at room temperature. This enzyme extraction is not effective for the serogrouping of all group D streptococcus species. Achromopeptidase extracts can be used with latex or coagglutination reagents.

The relationship between the serogroup antigen and lipopolysaccharide ofLegionella pneumophila

Serogroup-specific antigen was extracted from a number of Legionella pneumophila strains and compared with phenol-water extracted lipopolysaccharide on the basis of gel filtration, chemical analysis, SDS-PAGE and reaction with serogroup-specific antibody in immunoblots. Serogroup specificity is apparently borne by the O side-chains of the lipopolysaccharide, which, although smooth in type, partitions in the phenol phase. For four serogroup 1 strains tested, there was no qualitative correlation between O side-chain length and pulmonary virulence for guinea-pigs.

Isolation and characterization of the cytoplasmic and outer membranes of the Legionnaires' disease bacterium (Legionella pneumophila).

Legionella pneumophila, the etiologic agent of Legionnaires' disease, is phagocytized in an unusual way and multiplies in human mononuclear phagocytes in a novel phagosome. As a first step toward understanding these L. pneumophila-phagocyte interactions, we have studied the envelope of L. pneumophila Philadelphia 1 strain. We isolated cell envelopes by treating whole bacterial cells with lysozyme and EDTA to convert them to spheroplasts, then lysing the spheroplasts osmotically or sonically. We resolved the cell envelopes into two membrane fractions by isopycnic centrifugation. We localized NADH oxidase to the fraction of buoyant density 1.145, which we designated cytoplasmic membrane, and lipopolysaccharide (LPS) to the fraction of density 1.222, which we designated outer membrane. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the L. pneumophila outer membrane contains a single major protein species migrating at 28,000 mol wt; this is the major protein of the bacterium. The cytoplasmic membrane also contains a single major protein species migrating at 65,000 mol wt. Surface iodination of the bacteria and agglutination and immunofluorescence studies with rabbit antibody produced against the purified major outer membrane protein (MOMP) revealed that this protein is exposed at the cell surface. We isolated LPS from L. pneumophila membranes by SDS-EDTA treatment. The pattern obtained by subjecting the LPS to SDS-PAGE and staining the gel with silver nitrate suggests that L. pneumophila LPS might be atypical. We studied patient serologic responses to cell envelope components of L. pneumophila Philadelphia 1, a serogroup 1 organism. Sera from patients with evidence of infection with serogroup 1 L. pneumophila contained large amounts of antibody to this strain. Few of these antibodies recognized the MOMP of L. pneumophila. In contrast, greater than 98% of these antibodies were directed against the LPS. This indicates that LPS is the dominant serogroup antigen and the major antigen responsible for the reactivity of patient sera in the indirect fluorescent antibody assay, currently the principal diagnostic assay for Legionella infection.

Serological evidence of infection with California serogroup viruses (family Bunyaviridae) in residents of Long Hua, suburb of Shanghai, People's Republic of China

Sera from 126 residents of Long Hua, a suburb of Shanghai, in the People's Republic of China, were studied. Sera were tested for haemagglutination inhibiting antibodies to alphavirus (eastern equine encephalitis, western equine encephalitis), flavivirus (St. Louis encephalitis, Powassan, dengue) and California serogroup (snowshoe hare) antigens. Flavivirus antibodies were found in 14 (11·1%) and California serogroup antibodies in 5 (3·9%) individuals. Neutralizing antibodies with highest titres to snowshoe hare virus were demonstrated in 3 of the 5 California serogroup reactors. We believe this to be the first report of California serogroup virus antibodies in Chinese residents and the first evidence to suggest that California serogroup viruses may be circulating in the Orient.

Antigens and Toxic Components of Legionella in Pathogenesis and Immunity

Legionellae are opportunistic facultative intracellular pathogens with several antigens and toxic components which may function synergistically in contribution to pathogenesis and immunity. The serogroup specific antigens are associated with endotoxic activities of the bacteria and are potent adjuvants in inducing hypersensitivity and potentiating antibody responses to various antigens. Two protein toxins interfere with oxidative metabolism of host cells and are potential inhibitors of intracellular bactericidal activities. Tissue damage in the host appears to be caused by lysis of infected cells with release of toxic substances of host and bacterial origins. In host defense, the serogroup antigens provide primarily group-specific immunity, and the acid soluble protein toxin induces cross-protection among different serogroups. The combined effects of antibodies to these antigens in promoting phagocytosis and abrogating toxicity would enhance intracellular killing of the invading bacteria. The serogroup antigen complexes may also function as a potent adjuvant to modulate host responses to the invading bacteria.

Inapparent infection of sheep in Britain by leptospires of the Australis serogroup

Routine serological surveillance of a flock identified 17 out of 300 sheep which developed antibodies to leptospires during a period of one year. The predominant serological reaction was with Australis serogroup antigens and leptospires belonging to the Australis serogroup were isolated from the urine of two animals.