Detection of Vibrio cholerae with monoclonal antibodies specific for serovar O1 lipopolysaccharide

Generation and Characterization of Monoclonal Antibodies to the Ogawa Lipopolysaccharide of Vibrio cholerae O1 from Phage-Displayed Human Synthetic Fab Library

Vibrio cholerae, cause of the life-threatening diarrheal disease cholera, can be divided into different serogroups based on the structure of its lipopolysaccharide (LPS), which consists of lipid-A, corepolysaccharide and O-antigen polysaccharide (O-PS). The O1 serogroup, the predominant cause of cholera, includes two major serotypes, Inaba and Ogawa. These serotypes are differentiated by the presence of a single 2-O-methyl group in the upstream terminal perosamine of the Ogawa O-PS, which is absent in the Inaba O-PS. To ensure the consistent quality and efficacy of the current cholera vaccines, accurate measurement and characterization of each of these two serotypes is highly important. In this study, we efficiently screened a phage-displayed human synthetic Fab library by bio-panning against Ogawa LPS and finally selected three unique mAbs (D9, E11, and F7) that specifically react with Ogawa LPS. The mAbs bound to Vibrio cholerae vaccine in a dose-dependent fashion. Sequence and structure analyses of antibody paratopes suggest that IgG D9 might have the same fine specificity as that of the murine mAbs, which were shown to bind to the upstream terminal perosamine of Ogawa O-PS, whereas IgGs F7 and E11 showed some different characteristics in the paratopes. To our knowledge, this study is the first to demonstrate the generation of Ogawa-specific mAbs using phage display technology. The mAbs will be useful for identification and quantification of Ogawa LPS in multivalent V. cholerae vaccines.

Diagnostic techniques for rapid detection of Vibrio cholerae O1/O139

Cholera caused by the toxigenic Vibrio cholerae is still a major public health problem in many countries. This disease is mainly due to poor sanitation, hygiene and consumption of unsafe water. Several recent epidemics of cholera showed its increasing intensity, duration and severity of the illness. This indicates an urgent need for effective management and preventive measures in controlling the outbreaks and epidemics. In preventing and spread of epidemic cholera, rapid diagnostic tests (RDTs) are useful in screening suspected stool specimens, water/food samples. Several RDTs developed recently are considered as investigative tools in confirming cholera cases, as the culture techniques are difficult to establish and/or maintain. The usefulness of RDTs will be more at the point-of-care facilities as it helps to make appropriate decisions in the management of outbreaks or epidemiological surveillance by the public health authorities. Apart from RDTs, several other tests are available for the direct detection of either V. cholerae or its cholera toxin. Viable but non-culturable (VBNC) state of V. cholerae poses a great challenge in developing RDTs. The aim of this article is to provide an overview of current knowledge about RDT and other techniques with reference to their status and future potentials in detecting cholera/V. cholerae.

Hybridoma as a specific, sensitive, and ready to use sensing element: a rapid fluorescence assay for detection of Vibrio cholerae O1

Over the last decade, isolation and purification of monoclonal antibodies, for diagnostic analysis, have been carried out using the hybridoma expression system. The present study describes a novel example of a detection system using hybridoma cells containing antibody against O1 antigen directly for V. cholerae diagnosis, which is a major health problem in many parts of the world, especially in developing countries. This method has advantages such as simplicity, ease of process, and it does not require manipulation of hybridoma cell. For this approach, an efficient amount of fluorescence calcium indicator, fura 2-AM, was utilized, which emitted light when the intracellular calcium concentration increased as result of antigen binding to specific antibody. More reliable results are obtained via this method and it is considerably faster than other methods, which has the response time of less than 45 s for detection of V. Cholerae O1. Also, the limit of detection was computed to be 50 CFU/mL (<13 CFU per assay). In addition, no significant responses were observed in the presence of other bacteria with specific hybridoma or other cell lines exposed to V. cholerae O1. Furthermore, this method was successfully applied to V. cholerae O1 detection in spiked environmental samples, including water and stool samples without any pretreatment. All results reveal that hybridoma cells can provide a valuable, simple, and ready to use tool for rapid detection of other pathogenic bacteria, toxins, and analytes.

A luminescent hybridoma-based biosensor for rapid detection of V. cholerae upon induction of calcium signaling pathway

In this study, a hybridoma based biosensor was developed for rapid, sensitive and selective detection of Vibrio cholerae O1 which converts the antibody-antigen binding to bioluminescence light. After investigation on hybridoma performance, the biosensor was constructed by transfecting specific hybridoma cells with aequorin reporter gene and the bioluminescence activities of stable biosensor were measured. The sensitivity of biosensor was as few as 50 CFU/ml and it showed no responses to other entric bacteria. Moreover, the response time of biosensor was estimated in 7th second which means this method is considerably faster than many available detection assays. In addition, this biosensor was successfully applied to V. cholerae detection in environmental samples with no significant loss in sensitivity, demonstrating our proposed biosensor provides a sensitive and reliable method for detection of V. cholerae in natural samples. The application of whole hybridoma cell directly as a sensing element in biosensor construction which mentioned for the first time in present study suggests that hybridoma cells could provide a valuable tool for future studies in both basic and diagnostic sciences and could be considered as a fast and specific sensing element for detection of other pathogens in different applications.

The ABCs (Antibody, B Cells, and Carbohydrate Epitopes) of Cholera Immunity: Considerations for an Improved Vaccine

Cholera, a diarrheal disease, is known for explosive epidemics that can quickly kill thousands. Endemic cholera is a seasonal torment that also has a significant mortality. Not all nations with extensive rural communities can achieve the required infrastructure or behavioral changes to prevent epidemic or endemic cholera. For some communities, a single-dose cholera vaccine that protects those at risk is the most efficacious means to reduce morbidity and mortality. It is clear that our understanding of what a protective cholera immune response is has not progressed at the rate our understanding of the pathogenesis and molecular biology of cholera infection has. This review addresses V. cholerae lipopolysaccharide (LPS)-based immunogens because LPS is the only immunogen proven to induce protective antibody in humans. We discuss the role of anti-LPS antibodies in protection from cholera, the importance and the potential role of B cell subsets in protection that is based on their anatomical location and the intrinsic antigen-receptor specificity of various subsets is introduced.

Evaluation of monoclonal antibody based immunochromatographic strip test for direct detection of Vibrio cholerae O1 contamination in seafood samples

A strip test for the detection of Vibrio cholerae O1 was developed using two monoclonal antibodies (MAbs), VC-223 and VC-1226, specific to the lipopolysaccharides of Vibrio cholerae O1 Inaba and Ogawa serovars. The sensitivity of the test was 5 × 10(5)cfu/mL which was similar to that of dot blot test. The detection limit could be improved to 1cfu/mL of the original bacterial content after pre-incubation of the bacterium in alkaline peptone water (APW) for 12h. Detection of V. cholerae O1 in various fresh seafood samples such as shrimp, blood clam, mussel and oyster could be performed directly with sensitivities ranged from 5 × 10(5) to 10(6)cfu/mL. After pre-enrichment of the shrimp sample in APW, the detection sensitivities increased to 10(2) to 10CFU/mL of the original bacterial content after incubation for 12 and 24h. However, the detection sensitivities were also depending on the content of the other bacteria that might inhibit the growth of V. cholerae during pre-enrichment step. The V. cholerae O1 strip test has advantages in speed, and simplicity in not requiring sophisticated equipment or specialized skills and the sample could be directly examined without requirement for sample processing.

Differentiation among the Vibrio cholerae serotypes O1, O139, O141 and non-O1, non-O139, non-O141 using specific monoclonal antibodies with dot blotting

Seven different monoclonal antibodies (MAbs) specific to only Vibrio cholerae were produced using a combination of five representative serotypes of V. cholerae for immunization. The first three MAbs (VC-93, VC-82 and VC-223) were specific to the V. cholerae serogroup O1 with different avidity for the serotypes O1 Inaba and O1 Ogawa. The fourth and the fifth MAbs were specific to V. cholerae O139 (VC-812) or O141 (VC-191) serogroups, respectively. The sixth MAb (VC-26) bound to all three serogroups of V. cholerae. The seventh MAb (VC-63) bound to all twenty five isolates of V. cholerae used in this study. None of the seven MAbs showed cross-reactivity with other Vibrio spp. or closely-related V. cholerae species, V. mimicus or other gram-negative bacteria. The eighth MAbs (VC-201) specific to almost all Vibrio spp. was also obtained. In dot blotting, these MAbs can be used to detect a diluted pure culture of V. cholerae in solution with a sensitivity range of from 10(5) to 10(7) CFU ml(-1). However, the detection capability could be improved equivalent to that of PCR technique after preincubation of samples in alkaline peptone water (APW). Thus, these MAbs constitute convenient immunological tools that can be used for simple, rapid and simultaneous direct detection and differentiation of the individual serotypes of V. cholerae in complex samples, such as food and infected animals, without the requirement for bacterial isolation or biochemical characterization.

Characterization of a novel protective monoclonal antibody that recognizes an epitope common to Vibrio cholerae Ogawa and Inaba serotypes

A novel protective monoclonal antibody (mAb) that recognizes a lipopolysaccharide (LPS) epitope common between serotypes Ogawa and Inaba of the O1 serogroup of Vibrio cholerae was characterized and the potential to develop peptide mimics of this protective LPS epitope was investigated. mAb 72.1 recognizes both Ogawa and Inaba LPS and it is vibriocidal and protective in passive immunization against infection by strains of both serotypes. The cDNA-derived amino acid sequence of mAb 72.1 is closely related to the previously characterized mAb ZAC-3, which is thought to recognize an epitope in the lipid A core region of O1 LPS. In an attempt to develop a peptide mimic-based vaccine against V. cholerae, phage display libraries were screened with mAb 72.1 and 11 peptide mimics were identified. Remarkably, all of the peptide sequences identified from linear phage display libraries contained two cysteine residues, suggesting that mAb 72.1 preferentially binds to peptides constrained with a disulphide bond. One of the peptide mimics was immunologically characterized. Although immunization of mice with this peptide mimic conjugated to KLH elicited antibodies against the peptide itself, these antibodies did not cross-react with Ogawa or Inaba LPS. Effectiveness of a peptide mimic as a vaccine may depend on how well the peptide can mimic the carbohydrate interactions when binding to the anti-carbohydrate antibody. Thus, investigating how peptides and LPS bind to mAb 72.1 may be useful in improving current peptide mimics or designing more effective peptide mimics. Identification and characterization of novel protective anti-LPS antibodies may be useful in studying protective epitopes of LPS, which may help develop LPS-based therapeutics against V. cholerae.

B-cell responses to lipopolysaccharide epitopes: Who sees what first - does it matter?

PROBLEM

Cholera is the paradigm for waterborne bacterial diseases. For over a 100 years, scientists have tried to develop a universally effective vaccine for cholera. We are hampered in our efforts because we do not know the details of the basic immune response to Vibrio cholerae antigens. What are the most proactive antigens? What special needs for immunization are engendered by previous exposure to cholera or the age of the individual? How long does immunity last, and is this immunity a classic immunologic memory or re-exposure and continual boosting?

METHOD OF STUDY

Immunization with synthetic derivatives of the carbohydrate moieties of V. cholerae lipopolysaccharide (LPS) coupled to different carrier proteins (neoglycoconjugates, NGC) has allowed dissection of the response to the disaccharide array of perosamine that represent either the Inaba or the Ogawa serotype. Studying serum anti-LPS endpoint titers and the serum vibriocidal response to NGC provides insight into the importance of LPS serotype-specific B-cell epitopes and how antibody response are influenced by the form of the LPS immunogen.

RESULTS

We found that murine serum antibody responses to V. cholerae LPS are dynamic. The magnitude of serum anti-LPS antibody titers and the capacity to induced vibriocidal antibodies (immunoglobulin M) are influenced by the initial immunizing serotype of LPS, the structure of the LPS immunogen (native LPS versus NGC), and the order of serotype immunization in a prime boost immunization strategy. The dynamic of the immune response to LPS immunogens is typified by the fact that the host species can affect the immunization response. We found mice do not make vibriocidal antibody to Inaba NGC but rabbits do. This is in contrast to the Ogawa NGC that induced vibriocidal antibody in mice.

CONCLUSION

The results suggest that the host's B-cell repertoire can influence the immunization efficacy; therefore, the development of the new generation of NGC V. cholerae vaccines should focus on human volunteers and their ability to mount protective responses.

Effect of saccharide length on the immunogenicity of neoglycoconjugates from synthetic fragments of the O-SP of Vibrio cholerae O1, serotype Ogawa

A synthetic hexasaccharide, identical to the terminal hexasaccharide of Ogawa LPS, coupled to bovine serum albumin induced protective antibodies in mice. To determine if there was a minimum saccharide length required for immunogenicity and efficacy, shorter (mono- to pentasaccharide) neoglycoconjugates (CHO-BSA) were tested in mice. The Ogawa CHO-BSA was inoculated at either a constant mass but differing moles, or equal moles but differing masses. Humoral responses were essentially the same when mice received 9 microg of the carbohydrate (0.007 mM with the pentasaccharide) in each of the neoglycoconjugates prepared from mono- through the pentasaccharide, or the same molar amount (0.007 mM), proportionally less by weight when going from the penta- to the monosaccharide. These data show that, within this dose range, the responses occurred virtually independently of the amount of immunogen. Humoral antibodies induced by these immunogens were generally not vibriocidal. Selected antisera induced by CHO-BSA immunogens were protective, but the ELISA titers of the sera were not predictive of the protective capacity. Purified, Ogawa LPS induced anti-Ogawa LPS IgM antibody titers similar to those induced by the Ogawa CHO-BSA conjugates. The anti-whole LPS sera were strongly vibriocidal, as were the previously reported sera induced by hexasaccharide conjugates. This suggests either that the shorter oligosaccharides lack a conformational epitope provided by the hexasaccharide or that the LPS has additional B cell epitopes or selects different B cells in the primary response.

Synthetic fragments of Vibrio cholerae O1 Inaba O-specific polysaccharide bound to a protein carrier are immunogenic in mice but do not induce protective antibodies

Development of Vibrio cholerae lipopolysaccharide (LPS) as a cholera vaccine immunogen is justified by the correlation of vibriocidal anti-LPS response with immunity. Two V. cholerae O1 LPS serotypes, Inaba and Ogawa, are associated with endemic and pandemic cholera. Both serotypes induce protective antibody following infection or vaccination. Structurally, the LPSs that define the serotypes are identical except for the terminal perosamine moiety, which has a methoxyl group at position 2 in Ogawa but a hydroxyl group in Inaba. The terminal sugar of the Ogawa LPS is a protective B-cell epitope. We chemically synthesized the terminal hexasaccharides of V. cholerae serotype Ogawa, which comprises in part the O-specific polysaccharide component of the native LPS, and coupled the oligosaccharide at different molar ratios to bovine serum albumin (BSA). Our initial studies with Ogawa immunogens showed that the conjugates induced protective antibody. We hypothesized that antibodies specific for the terminal sugar of Inaba LPS would also be protective. Neoglycoconjugates were prepared from synthetic Inaba oligosaccharides (disaccharide, tetrasaccharide, and hexasaccharide) and BSA at different levels of substitution. BALB/c mice responded to the Inaba carbohydrate (CHO)-BSA conjugates with levels of serum antibodies of comparable magnitude to those of mice immunized with Ogawa CHO-BSA conjugates, but the Inaba-specific antibodies (immunoglobulin M [IgM] and IgG1) were neither vibriocidal nor protective in the infant mouse cholera model. We hypothesize that the anti-Inaba antibodies induced by the Inaba CHO-BSA conjugates have enough affinity to be screened via enzyme-linked immunosorbent assay but not enough to be protective in vivo.

Monoclonal antibodies specific for Campylobacter fetus lipopolysaccharides

Four monoclonal antibodies (mAbs) (M1357, M1360, M1823 and M1825) which reacted with Campylobacter fetus lipopolysaccharide (LPS) core region epitopes were produced and characterized. Reactivity of these mAbs with C. fetus core LPS epitopes was determined by enzyme-linked immunosorbent assay (ELISA) with whole cell proteinase K digests and phenol-water extracted LPS, and by immunoblotting with proteinase K digests. The specificities of the four mAbs were evaluated using an indirect ELISA. One of the mAbs reacted with 42 and three of the mAbs reacted with 41 of the 42 C. fetus strains examined. No reaction was observed between the four mAbs and 32 non-C. fetus bacteria tested, with the exception of one mAb with one organism. The four mAbs reacted with serotype A and B strains indicating the presence of shared epitopes in C. fetus LPS core oligosaccharides. The specificities of three mAbs previously produced to C. fetus LPS O-antigens (M1177, M1183 and M1194) were also evaluated and no reaction was observed with these mAbs and the 32 non-C. fetus bacteria tested. Strong immunofluorescence reactions were observed with the anti-O chain mAbs and selected C. fetus strains of the homologous serotype. These anti-LPS core oligosaccharide and anti-LPS O chain mAbs are highly specific for C. fetus and are potentially useful as immunodiagnostic reagents for detection, identification and characterization of C. fetus.

Immunochemical characterization of an Ogawa-Inaba common antigenic determinant of Vibrio cholerae O1

Cholera remains an important public health problem in many parts of the world and the availability of an effective cholera vaccine is important for the prevention of cholera in the countries affected by this disease. Despite the appearance in 1992 of a new serogroup, 0139, of Vibrio cholerae, most of the cholera outbreaks are still caused by V. cholerae O1 biotype El Tor. Vaccine trials in Asia from 1968 to 1971, and studies of the production of serotype-specific antiserum in rabbits and of the protective activity of monoclonal antibodies against diarrhoeal disease in neonatal mice, have led to the conclusion that the Ogawa serotype contains a specific antigenic determinant whereas the Inaba serotype contains a different antigenic determinant that cross-reacts with the Ogawa serotype. By studying the binding of anti-Ogawa monoclonal antibodies to synthetic oligosaccharide fragments mimicking the Ogawa O-specific polysaccharide, it has been shown that the terminal monosaccharide, bearing the 2-O-methyl group in the O-specific polysaccharide, is most probably the serotype-specific determinant for the Ogawa strain. However, study of the binding of a monoclonal antibody recognizing both Ogawa and Inaba serotypes suggested partial recognition of the core as well as of the O-specific polysaccharide of the LPS of V. cholerae O1. To further characterize this antigenic determinant that is common to the Ogawa and Inaba serotypes, the core and the O-specific polysaccharide linked to the core of V. cholerae O1 LPS were purified by preparative electrophoresis. The O-specific polysaccharide linked to the core was subjected to periodate oxidation to destroy sugars from the core. Binding studies of these purified saccharide fragments to a monoclonal antibody which is protective in mice and specific to the antigenic determinant common to Ogawa and Inaba serotypes showed that both the core and the O-specific polysaccharide are involved in this common antigenic determinant. This explains how the presence or the absence of the Ogawa-specific antigenic determinant would lead to the expression of two independent antigenic determinants of V. cholerae O1, one specific to the Ogawa serotype and the other common to both Ogawa and Inaba serotypes.

Development of highly specific monoclonal antibodies for the diagnosis of Vibrio cholerae 01

We report here the development of two monoclonal antibodies, termed 5G8 and 5C12, belonging to the IgM and IgG1 class, respectively, suitable for the identification of Vibrio cholerae 01 in clinical and environmental samples. The specificities of the monoclonals were evaluated by ELISA and indirect immunofluorescent microscopy of microorganisms normally present in stool samples and with two bacterial panels. One panel included 72 potentially antigenically related bacterial strains and the second panel included 20 pathogenic bacterial strains involved in diarrhea cases. The results of these extensive analyses indicate that monoclonal antibodies 5G8 and 5C12 are highly specific and suitable for the clinical diagnosis of Vibrio cholerae 01 in human stool samples by indirect immunofluorescent microscopy. Although the antigenic sites recognized by these antibodies were not identified in this study, the observation of Western blot patterns suggested that 5G8 and 5C12 monoclonal antibodies bind to LPS epitopes, a good structural marker for the detection of V. cholerae 01 because it is present in all bacterial cell walls.

Production and cross-reactivity patterns of a panel of high affinity monoclonal antibodies to Vibrio cholerae O139 Bengal

A series of monoclonal antibodies of different isotypes specific for Vibrio cholerae O139, the new pandemic strain of cholera, was produced. These mAbs reacted only with the reference strain (MO45) representing serovar O139 but did not react with any of the other reference strains representing serovars O1 to O140. Significantly, the mAbs did not agglutinate the R-cultures of V. cholerae (CA385, 20-93) which demonstrated the exceptional specificity of these mAbs and indicated that the mAbs recognized antigenic determinants unique for the O139 serovar. There was heterogeneity in the intensity of reactivity of the mAbs with strains of V. cholerae O139 isolated from diverse sources. Apart from 4H6, the other mAbs agglutinated all the O139 strains examined. 2D12 and 2F8 were the best mAbs based on the intensity of agglutination with all the O139 strains. Evaluation of 3A10 in comparison with a polyclonal anti-O139 antibody raised in rabbit using the slide agglutination format revealed that 3A10 fared as well as the polyclonal antibody for the laboratory identification of the O139 serovar. The acquisition of these mAbs provide reagents which would be very useful in the development of simple immunodiagnostic assays for the diagnosis of V. cholerae O139 infections.

Development of monoclonal antibodies that identify Vibrio species commonly isolated from infections of humans, fish, and shellfish

Monoclonal antibodies (MAbs) against Vibrio species that infect humans, fish, and shellfish were developed for application in rapid identifications. The pathogens included Vibrio alginolyticus, V. anguillarum, V. carchariae, V. cholerae, V. damsela, V. furnissii, V. harveyi, V. ordalii, V. parahaemolyticus, and V. vulnificus. Three types of MAbs were selected. The first important group included MAbs that reacted with only a single species. A second group comprised a number of MAbs that reacted with two, taxonomically closely related Vibrio species. For example, of 22 MAbs raised against V. alginolyticus, 6 recognized a 52-kDa flagellar H antigen common to both V. alginolyticus and V. parahaemolyticus; V. anguillarum and V. ordalii also shared antigens. A third group included three genus-specific MAbs that reacted with almost all Vibrio species but did not react with other members of the family Vibrionaceae (e.g., members of the Aeromonas, Photobacterium, and Plesiomonas genera) or a wide range of gram-negative bacteria representing many genera. This last group indicated the possible existence of an antigenic determinant common to Vibrio species. Two of these three genus-specific MAbs reacted with heat-stable antigenic determinants of Vibrio species as well as lipopolysaccharide extracted from Vibrio species. The use of the MAbs in blind tests and diagnosis of clinical isolates indicated that three different types of bacteria, viz., live, formalin-fixed, and sodium azide-killed bacteria, were detected consistently. Overall, it was found that the genus-specific MAbs were very useful for rapidly identifying vibrios in the screening of acute infections, while the species-specific MAbs and others were useful for completing the diagnosis.

Characterization and specificity controls of murine monoclonal antibodies against serogroup C1 Salmonella

Two IgG3 murine monoclonal antibodies, Cl-1 and Cl-2, that showed serologic specificities for the O antigens of serogroup C1 (0:6,7) Salmonella were established. The epitopes for the antibodies were found to reside on the repeating units of the serogroup C1 Salmonella lipopolysaccharide and were labile to sodium metaperiodate oxidation. Serologic reactivities of Cl-1 and Cl-2 were not inhibited by commercial monospecific antiserum to O antigen 7, but were inhibited to various degrees by anti-[O:6,7] serum. Both antibodies reacted strongly with all strains of serogroup C1 Salmonella that have either O:6(1),7, O:6(2),7, or O:6(1,2),7 antigens. Reactivities of Cl-1 and Cl-2 with the phage-14 lysogenized C1 strains that bear the phage-modified O antigen (O:6,7----O:6,7,14) were detected by slide agglutination method only and not by whole-cell enzyme-linked immunosorbent assay. Both Cl-1 and Cl-2 antibodies did not react with other O serogroups of salmonellae, nor with other Gram-negative or Gram-positive bacteria. The diagnostic value of these monoclonal antibodies together with a previously described monoclonal antibody against the serogroup C2 Salmonella was demonstrated using the slide agglutination method with monoclonal antibodies ascitic fluids.

Characterization of murine monoclonal antibodies against serogroup B salmonellae and application as serotyping reagents

Six murine hybridoma monoclonal antibodies reactive with lipopolysaccharide antigens of Salmonella typhimurium were obtained from a fusion of immune spleen cells from mice immunized with S. typhimurium and NS1 myeloma cells. Four antibodies appeared to be specific for serogroup B salmonellae, while the remaining two antibodies were found to be cross-reactive with Salmonella paratyphi A. The exquisite specificities of the Salmonella serogroup B monoclonal antibodies were demonstrated by their unique reactivities with different serotypes of group B salmonellae but with neither other O serogroups of salmonellae nor a wide spectrum of standard strains of other bacterial species. Serotyping of salmonella strains by the slide agglutination method with two of the serogroup B-specific monoclonal antibodies demonstrated their usefulness as serotyping reagents for the identification of serogroup B salmonellae in a routine diagnostic bacteriology laboratory.

Identification of Vibrio vulnificus O serovars with antilipopolysaccharide monoclonal antibody

A serotyping scheme for Vibrio vulnificus predicated on the detection of lipopolysaccharide (LPS) antigens is proposed. The serovar O typing scheme used to type V. vulnificus employs polyclonal antisera raised in rabbits immunized with heat-killed whole-cell vaccines. Polyclonal typing sera produced in this manner cross-react with heterologous strains. Affinity purification of polyclonal antisera with LPS affinity columns resolved some of these cross-reactions; however, affinity-purified polyclonal antisera still showed cross-reactions that were nonreciprocal. On the basis of the serological patterns that were obtained with affinity-purified polyclonal antisera, V. vulnificus strains were selected as vaccine strains for production of monoclonal antibody. Spleen cells harvested from BALB/c mice immunized with formalin-killed V. vulnificus cells were fused with SP2/O-Ag 14 myeloma cells. Hybridomas were screened by using LPS and whole-cell enzyme-linked immunosorbent assay to identify clones secreting LPS-specific antibodies. Monoclonal antibodies identified five LPS serological varieties of V. vulnificus and a single serovar each for Vibrio damsela and Vibrio hollisae. No cross-reactions between V. vulnificus and V. hollisae or V. damsela were observed.

Characterization and application of a murine monoclonal antibody that reacts specifically with the serogroup D1 Salmonella

A murine hybridoma cell line that produces monoclonal antibody (mAb) against the serogroup D1 Salmonella lipopolysaccharide (LPS) antigen was established. The trisaccharide tyvelose alpha 1----3 mannose alpha 1----4 rhamnose was shown to be involved in the reactive epitope of the mAb since this mAb reacted strongly with strains of serogroup D1 Salmonella but not with Salmonella strains from the O serogroups of A, B, and D2, and sodium meta-periodate was found to destroy the reactivity of the serogroup D1 O-antigen with the mAb. As such this mAb was found to be a useful serotyping reagent for the identification of serogroup D1 Salmonella, and for the differentiation of strains of serogroups D1 and D2 Salmonella which have identical flagellar H antigens.

The construction of a monoclonal diagnostic system for the field detection of Vibrio cholerae

An enzyme-based double monoclonal field diagnostic system detecting both serotypes of Vibrio cholerae has been developed. The system uses nitrocellulose as a solid support, 1.25% skimmed dried milk as blocking reagent, water as washing reagent, and alkaline phosphatase cross-linked to antibody by means of glutaraldehyde as detecting reagent. The sensitivity of the system was 10(5) vibrios/ml. The biotin-avidin system gave sensitivity an order of magnitude weaker. There were no cross-reactions with the range of other bacteria tested.

Production and characterization of murine monoclonal antibodies specific for serogroups E1 and E4 Salmonella

Two anti-Salmonella serogroup E-specific monoclonal antibodies (MAbs) are described. Neither antibody reacted with any of the 58 strains of serogroups A-D Salmonella tested by enzyme immunoassays nor did they react with any of the 21 other species of enterobacteria, 15 species of other Gram-negative bacteria, and 6 species of Gram-positive bacteria. In contrast, all 14 strains of serogroups E1 and E4 Salmonella reacted with both antibodies. Ascitic fluids of these two antibodies agglutinated all 42 strains of serogroups E1 and E4 Salmonella tested by slide agglutination method but did not agglutinate any of the 107 strains of other serogroups of Salmonella. Lysogenic conversion of serogroup E1 Salmonella strains by phages epsilon 15 and epsilon 34 resulted in loss of reactivities of these strains with the MAbs.