Two strains ofVibrio cholerae non-O1 possessing somatic (O) antigen factors in common withV. cholerae serogroup O139 synonym “Bengal”

Two strains (O22 reference strain, 169–68, and strain 490–93 isolated from a patient with diarrhea in Thailand) ofVibrio cholerae non-O1 possessing somatic (O) antigen factors in common withV. cholerae O139 synonym Bengal are described. The O antigens of these two strains were closely related to that ofV. cholerae O139 in an a,b-a,c type of relationship, but were not completely identical with serogroup O139. Therefore, both these strains are not classified into the O139 serogroup ofV. cholerae, because they have their own major antigens. As the strain 490–93 could not be placed into any of the 154 established O serogroups ofV. cholerae, this strain was assigned to a new serogroup, O155. For practical use, the diagnostic antiserum prepared against the O139 reference strain (MO45, ATCC 51394) ofV. cholerae must be absorbed with reference strains 169–68 and 490–93 representing serogroups O22 and O155 ofV. cholerae to remove cross-reacting agglutinins of the O22 and O155 strains, respectively.     

Antigenic specificity of opsonophagocytic antibodies in rabbit anti-sera to group B streptococci.

An opsonophagocytic assay has been developed which requires human polymorphonuclear leukocytes, immune serum, and complement for optimal killing of Group B streptococci. Only with all three of these components was killing of greater than 1.0 log10 of the initial inoculum achieved, using rabbit antisera directed to homologous strains of each of the five known serotypes of Group B streptococci. Titers of specific antisera which opsonized the strains and resulted in greater than 1 log 10 reduction of colony-forming units, ranged from 1:100 (serotype Ib) to 1:3200 (serotype Ia). Cross-reactions between serotype-specific sera and heterologous strains were seen in certain instances. Type Ic strain and serotype Ic antiserum demonstrated cross-reactions with types Ia and Ib which were explainable by known shared antigens among these types. The only other cross-reaction which resulted in greater than 1 log 10 reduction in colony-forming units was when unabsorbed antiserum to strain Ia was used to opsonize a strain of serotype III. Opsonization of 10 serotype III strains was demonstrated with a single type III antiserum. Killing of nine of these strains required polymorphonuclear leukocytes, complement, and antiserum, but one strain, D136C, the reference strain, could be killed (greater than 1 log 10 reduction in colony-forming units) without either complement or specific antiserum. Inhibition studies were performed utilizing large m.w. polysaccharide antigens extracted from each serotype. These antigens inhibited opsonization of homologous strains by homologous antisera with 50% inhibition points ranging between 0.5 and 4 mug.     

Immunoelectrophoretic characteristics ofOphiobolus graminis Sacc. as an aid in classification and determination

Antigens from four cultures ofO. graminis were compared immunoelectro-phoretically. Each culture produced a characteristic immunogram. More common antigens were found between the two cultures isolated from wheat or the two cultures isolated from oat than between a wheat and an oat isolate. Cell-wall antigens were the best reference antigens for serologic analysis of strain relationship. O. graminis antisera were cross-reacted with antigens from a number of other species of fungi. Relatively few of these cross-reacted with antisera to cell-wall antigens whereas more cross-reacted with antisera to whole-cell antigens.Immunoelectrophoretic analysis of antigens from a range of isolates ofO. graminis indicates specific immunograms which can be determined and separated from the immunograms developed by all other fungi when tested againstO. graminis antiserum. Immunoelectrophoresis can therefore be used as an aid in determiningO. graminis.     

Extended serotyping scheme forVibrio cholerae

Fifty-seven new O serogroups have been added to the existing serotyping scheme ofVibrio cholerae to extend the scheme from O84 to O140. Prominent new additions were serogroups O139 and O140. The reference strain of O139 was isolated from a patient from an epidemic of cholera-like diarrhea in Madras, Southern India. Serogroup O140 was assigned to a group ofV. cholerae strains which were tentatively named as the Hakata serogroup and which possessed the C (Inaba) factor but not the B (Ogawa) nor the A (major specific antigen of O1 serogroup ofV. cholerae). As all antisera against reference strains ofV. cholerae contained some amount of antibody to the rough (R) antigen, all diagnostic O antisera must be absorbed with the reference rough strain, CA385.     

Development of an O-antigen serotyping scheme for Cronobacter sakazakii

Cronobacter sakazakii is an opportunistic pathogen that can cause severe infections. Serotyping provides a basis for the categorization of bacterial strains and is an important tool for epidemiological and surveillance purposes. In this study, of the 135 Cronobacter strains tested initially, 119 were identified as C. sakazakii and used. A serotyping scheme for C. sakazakii that classifies strains based on their different O antigens was developed. Seven antisera that exhibited high agglutinin titers (>640) were produced. O2 and O6 antisera were specific for their homologous strains, O4 and O7 antisera gave heterologous titers with O1 and O6 antigens, respectively, and O1, O3, and O5 antisera cross-reacted with each other and require preabsorption with the other two antigens. All of these 119 C. sakazakii strains were clearly assigned to these seven serotypes. O1 and O2 are the dominant serotypes, comprising 69.7% of the isolates. We also characterized the O-antigen gene clusters using restriction fragment length polymorphism (RFLP). The grouping of C. sakazakii strains based on their RFLP banding patterns correlated well with the grouping of strains based on our serotyping scheme. The serotype scheme presented here could prove to be a useful tool for serotyping C. sakazakii isolates.     

Chemical and serological properties of lipopolysaccharides from Vibrio parahaemolyticus O-untypeable strains isolated from patients

Chemical and serological studies have been carried out on the O-antigenic lipopolysaccharides (LPS) of six strains, U-6443, W-90144, X-3972, AD-7999, 90A-6611 and KX-V212, of Vibrio parahaemolyticus isolated from patients. The O-serotypes of these strains have not been identified because they were not agglutinated by any diagnostic antisera against known O-serotype strains. A compositional sugar analysis of their LPS revealed that out of the six O-untypeable (OUT) strains, U-6443, W-90144 and AD-7999 strains belonged to chemotype II (chemotype of O2), 90A-6611 and KX-V212 strains to chemotype III (chemotype of O3, O5, O11 and O13) and X-3972 strain to chemotype IV (chemotype of O4). A structural analysis of LPS isolated from KX-V212 revealed that the inner core region of the LPS consisted of only one mole of 2-keto-3-deoxy-D-manno-octonic acid, which carried a phosphate group at position C4 and the outer core at position C5. In passive hemolysis tests performed by using LPS as the antigen to sensitize sheep red blood cells (SRBC), and diagnostic antisera (O1 to O11) or anti-whole-cell rabbit antisera raised against O12, O13 and the six OUT strains, strong cross-reactivity was observed among LPS derived from the strains belonging to chemotype II (U-6443, W-90144, AD-7999 and O2). Strong cross-reactivity was also observed between X-3972 (chemotype IV) and O4 LPS. In contrast, LPS from two of the strains belonging to chemotype III (90A-6611 and KX-V212) did not react with any of the antisera raised against known O-serotypes. Cross-absorption tests showed that the O-antigens of U-6443, W-90144 and AD-7999 were identical to that of O2, and the O-antigen of X-3972 to that of O4. On the other hand, after the absorption of antisera raised against 90A-6611 and KX-V212 with O2 cells, the hemolytic activities against SRBC sensitized with homologous LPS were still retained at a high titer, whereas the hemolytic activities against SRBC sensitized with LPS from other O-serotype strains were completely eliminated. A cross-absorption test revealed that the O-antigens of these two strains were identical to each other. Thus, it was demonstrated that the O-serotype of OUT strains 90A-6611 and KX-V212 was not involved in the known O-serotypes; rather it represented a novel serotype which has not hitherto been reported.     

Antigenic epitope in Pseudomonas aeruginosa lipopolysaccharide immunologically cross-reactive with Escherichia coli 026 lipopolysaccharide

The human monoclonal antibody MH-4H7 recognizes the lipopolysaccharide outer core region of some Pseudomonas aeruginosa strains and in of some Pseudomonas aeruginosa strains and in particular strongly binds to strains of Lányi serotype 04. In this paper, we report that this monoclonal antibody also reacts with Escherichia coli O26 LPS. However, our results suggest that the previous reported immunological cross reaction between P. aeruginosa 04 and E. coli O26 strains (which was observed by using antisera against heat-stable antigens) is not due to the similarity of the O-polysaccharides.     

Characterization of polyagglutinating and surface antigens in Pseudomonas aeruginosa

Mutants of Pseudomonas aeruginosa PAC1R (serotype O:3) which were resistant to bacteriophage D were isolated and shown to react with O:5d, O:9 and O:13 antisera as well as O:3. Antisera to the parent strain and to the three polyagglutinating (PA) mutants also showed cross-reactions. The mutants differed from the parent strain in their lipopolysaccharide (LPS) composition. The LPS from two of the three mutants yielded high molecular weight polysaccharide fractions. Although the high molecular weight fraction from one of the mutants contained the amino sugars and other components characteristic of the O:3 serotype strains, its mobility on Sephadex G75 was different from that of the parent strain. The high molecular weight material from the second mutant lacked the O-antigenic determinants but these were present in a semi-rough LPS fraction. The third mutant appeared rough and completely lacked the O-antigenic components. These three mutants were compared with the parent strain and with a non-agglutinating LPS-defective mutant which lacked both O-antigenic side chains and all neutral sugars in the outer core. Agglutination with absorbed sera and haemagglutination using purified LPS and ELISA detection suggested that wall components other than LPS were responsible for some of the cross-reactions observed. The components responsible were detected after SDS-PAGE of crude outer membrane fractions by a combination of Coomassie blue and silver-staining and antigenic components were detected by immunoelectrophoresis and ELISA-linked immunoblotting of the gels. The main antigenic determinants detected by antiserum to the parent strain were in the high molecular weight O-polysaccharide fractions and in the semirough fractions of the LPS, with some activity due to the H protein of the outer membrane. O:5d antisera reacted with unidentified high molecular weight polysaccharide fractions. Cross-reactions with the O:9 antiserum appeared to be due mainly to the F porin and, to a lesser extent, to the G and E proteins of the outer membrane. O:13 antiserum reacted with high molecular weight polysaccharide fractions but also with the rough core and F and H protein. Cross-reactivity of the other three mutant antisera could largely be interpreted in terms of the outer membrane components exposed in each strain. One reacted strongly with the F porin and the rough core, while the others reacted with a number of protein and LPS-derived fractions.(ABSTRACT TRUNCATED AT 400 WORDS)     

Structural and Genetic Basis for the Serological Differentiation of Pasteurella multocida Heddleston Serotypes 2 and 5

Pasteurella multocida is classified into 16 serotypes according to the Heddleston typing scheme. As part of a comprehensive study to define the structural and genetic basis of this scheme, we have determined the structure of the lipopolysaccharide (LPS) produced by P. multocida strains M1404 (B:2) and P1702 (E:5), the type strains for serotypes 2 and 5, respectively. The only difference between the LPS structures made by these two strains was the absence of a phosphoethanolamine (PEtn) moiety at the 3 position of the second heptose (Hep II) in M1404. Analysis of the lpt-3 gene, required for the addition of this PEtn residue, revealed that the gene was intact in P1702 but contained a nonsense mutation in M1404. Expression of an intact copy of lpt-3 in M1404 resulted in the attachment of a PEtn residue to the 3 position of the Hep II residue, generating an LPS structure identical to that produced by P1702. We identified and characterized each of the glycosyltransferase genes required for assembly of the serotype 2 and 5 LPS outer core. Monoclonal antibodies raised against serotype 2 LPS recognized the serotype 2/5-specific outer core LPS structure, but recognition of this structure was inhibited by the PEtn residue on Hep II. These data indicate that the serological classification of strains into Heddleston serotypes 2 and 5 is dependent on the presence or absence of PEtn on Hep II.Pasteurella multocida is a gram-negative pathogen that causes serious diseases in animals and humans. It is the causative agent of fowl cholera (7), hemorrhagic septicemia in cattle (9), atrophic rhinitis in pigs (6), and dog and cat bite infections in humans (28).P. multocida isolates may be grouped serologically based on capsular antigens into five serogroups—A, B, D, E, and F—using a passive hemagglutination test with erythrocytes sensitized with capsular antigen. Structural information is available for the capsular polysaccharides synthesized by serogroups A (hyaluronic acid) (22), D (heparin) (10), and F (chondroitin) (10). The genes involved in biosynthesis of the capsules have been identified for all five serogroups (27), and capsule is a critical virulence factor for serogroups A (8) and B (3).Lipopolysaccharide (LPS) is also an important virulence factor in P. multocida (13) and can be used for the identification of strains, with two main somatic typing systems reported (14, 17). The Namioka system is based on a tube agglutination test and is able to recognize 11 serotypes (17), whereas the Heddleston system uses a gel diffusion precipitation test and can recognize 16 serotypes; the Heddleston system is currently the preferred method (14). Current classification of P. multocida strains combines capsular typing with Heddleston somatic typing. Strains are given a designation in which the first letter indicates the capsular group and the number designates the Heddleston LPS serotype (e.g., A:1 indicates a strain that is capsular group A and LPS serotype 1). LPS produced by each of the 16 Heddleston serotype strains has been examined previously for sugar content and reactivity with LPS antisera (21). The LPS isolated from serotype 2 and 5 strains was virtually identical in sodium dodecyl sulfate-polyacrylamide gel electrophoresis migration profile (19), sugar composition, and serological reactivity with anti-LPS antibodies (21). Interestingly, serotypes 2 and 5 were the only serotypes found to elaborate two isomers of heptose in their LPS, namely l-glycero-d-manno-heptose (ld-Hep) and d-glycero-d-manno-heptose (dd-Hep) (21). The aims of this study were to determine whether the LPS molecules made by these two serotypes were structurally distinct and to compare the LPS structures with those previously determined for P. multocida serotypes 1 and 3 (24-26). Furthermore, we identified the transferase genes responsible for the assembly of the outer core LPS structure in each of these strains and characterized the function of each glycosyltransferase.     

Serological Characterization of Actinobacillus pleuropneumoniae Biotype 1 Strains Antigenically Related to both Serotypes 2 and 7

Nine Danish Actinobacillus pleuropneumoniae biotype 1 isolates were shown by latex agglutination and indirect haemagglutination to possess capsular polysaccharide epitopes identical to those of serotype 2 strain 1536 (reference strain of serotype 2) and strain 4226 (Danish serotype 2 strain). Immunodiffusion confirmed the antigenic relationship with serotype 2 and further demonstrated an antigenic relationship with strain WF83 (reference strain of serotype 7). SDS-PAGE with LPS from strains 1536, 4226, WF83 and strain 7317 (representative of the 9 isolates examined) showed that strains WF83 and 7317 had an identical smooth ladder pattern whereas LPS from strains 1536 and 4226 showed a distinctly different pattern. The antigenic similarities of the LPS of strains WF83 and 7317 were confirmed by immunoblots using rabbit or pig antisera prepared against the 3 strains. No antigenic similarities in the LPS of strains 1536 and 7317 were revealed. Since an antigenic determinant specific for the 9 isolates could not be demonstrated with the methods used, the strains are proposed to be designated K2:O7.     

<Emphasis Type="Italic">RT1.L</Emphasis>: a family of MHC class Ib genes of the rat major histocompatibility complex with a distinct promoter structure

RT1.L class I antigens have originally been identified in LEW rats by LEW.1LV3-anti-LEW.1LM1 antisera and have been classified as nonclassical. We report now that LEW.1LV3-anti-LEW.1LM1 antisera react with three different antigens, termed RT1.L1, RT1.L2, and RT1.L3. This was found by serological analysis of a panel of transfectants expressing different class I genes of strain LEW with a LEW.1LV3-anti-LEW.1LM1 antiserum and two monoclonal antibodies (mAbs HT20 and HT21) generated in the same strain combination. The antiserum reacted with all three antigens: the two mAbs with RT1.L1 and RT1.L2, respectively. Sequence analysis showed that the genes encoding RT1.L1, RT1.L2, and RT1.L3 cluster together in a phylogenetic analysis of rat and mouse ₁-₂ sequences and that they share an unusual MHC class I promoter in which Enhancer A and B, as well as the interferon response element (IRE), are missing. Exchange of the promoter in RT1.L2 against the classical RT1.A promoter resulted in high surface expression in appropriate transfectants, indicating that the deviant promoter is responsible for the weak surface expression of the RT1.L2 gene. The very similar promoter structures of RT1.L1 and RT1.L3 are likely to contribute also to the weak expression of these genes. As RT1.L3 maps closely to the deletion in the mutant haplotype lm1, the RT1.L family can be located in the class I region extending from Bat1 to Pou5f1. Different from other allogeneic mAbs detecting known class I molecules encoded by genes of the RT1.C/E region, HT20 and HT21 react with a wide panel of strains carrying different RT1 haplotypes. This suggests that nonclassical class I genes of the RT1.L family are present in most RT1 haplotypes.Nucleotide sequences reported in this paper have been submitted to GenBank with accession numbers AF457139 (RT1.L1), AY397759 (RT1.L2) and AY445668 (RT1.L3)     

Serological Activity of 'Bacteroides fragilis' Culture Supernatants

Culture supernatants of 17 strains of the ' Bacteroides fragilis ' group were treated with four volumes of acetone. The precipitates, after dialysis and lyophilization, were used as antigens in the double diffusion test with antisera against serotype strains of ' B. fragilis '. In the culture supernatant of one strain we did not demonstrate the presence of serologically active substances. Sixteen preparations reacted in immunodiffusion with antiserum against ' B. ovatus ' serotype B. Ten preparations reacted with antiserum B only and six preparations gave, additionally, precipitation lines with other serotype antisera (A, E₂).     

Antigenic determinants and specificity of antisera against acidophilic bacteria

Polyclonal antisera, produced against whole cells of Thiobacillus thiooxidans, T. ferrooxidans and Leptospirillum ferrooxidans, gave highly specific reactions when cross-reacted with 23 strains of acidophilic bacteria using an immunofluorescence (IF) staining technique. Strains of identical serotype exhibited maximum cross-reaction whereas strains of different serotype reacted only weakly. Lipopolysaccharides (LPS) examined by SDS-PAGE showed different, serotype-specific migration patterns indicating their rough or smooth character. LPS patterns may therefore be used for serological classification of acidophilic bacteria. Surface antigens of four strains were identified by immunoblot staining; LPS and some proteins were antigenic determinants with LPS the most specific.The authors are with the Universität Hamburg, Institut für Allgemeine Botanik, Abteilung für Mikrobiologie, Ohnhorststrasse 18, D-22609 Hamburg, Germany     

Some serological properties ofActinobacillus pleuropneumoniae strains of serotypes 1 through 5

Rabbits were hyperimmunized with live, formalin-killed, and heat-treated antigen preparations of the reference strains of serotypes 1 through 5 ofActinobacillus pleuropneumoniae in order to study the antibody response to both soluble and particulate antigens. The antibody response was studied by means of precipitation, agglutination, coagglutination, indirect hemagglutination, and complement fixation tests.Serotyping ofA. pleuropneumoniae strains was done by ring precipitation (RP) and coagglutination (CoA) tests with unheated and heated cell-saline extract as antigens and rabbit hyperimmune sera produced against either live cultures or formalin-killed whole-cell suspensions. The results showed that live cultures provoked more cross-reactive antibodies in rabbits, thus making the antisera unsuitable for use in serotyping by the RP test when unheated wholecell saline extract was used as antigen. Rabbit hyperimmune serum produced against formalinkilled bacterial suspension gave serotype-specific reactions in the RP test. Boiled or autoclaved cell-saline extracts gave serotype-specific reactions in the RP test even when rabbit anti-livecell sera were used. Serotype-specific reactions were obtained in the CoA test in both rabbit anti-live or anti-formalin-killed cell sera with either unheated or heated bacterial cell suspensions as antigens.Live and formalin-killed whole-cell suspensions as well as their saline extracts provoked a high antibody response in rabbits. Heating the cell suspension at 100°C for 1 h caused a significant reduction in their immunogenic potency, whereas autoclaving (121°C) of the cell suspension for 1 h almost completely destroyed their serotype-specific immunogenic properties, since the antibody response was either absent or very poor and not type-specific. However, neither boiling nor autoclaving of the cell suspensions caused significant reduction in their ability to react with preformed antibodies. Phenol-water-extracted antigens gave the highest degree of serotype specificity in the complement fixation test.     

Characteristics of lipopolysaccharides ofSalmonella typhi isolated from carriers and patients suffering from typhoid fever

Lipopolysaccharides (LPS) ofSalmonella typhi strains, isolated from carriers and patients suffering from typhoid fever, were characterised according to their biochemical properties, morphological structure and degree of aggregation of complexes. All preparations of LPS, regardless of their origin, were morphologically heterogeneous. Free electrophoresis and immunoelectrophoresis demonstrated that LPS preparations were composed of components possessing different mobilities in electric fields. LPS of bacterial strains isolated from both carriers and patients, split upon reaction in immunoelectrophoresis with specific antiserum 73, rabbit antiserum toSalmonella typhi Vi Bhatnagar and 0–901 split into anodic and cathodio fractions. The anodic fraction reacted similarly as Vi antigen. LPS fromSalmonella typhi Ty-2 yielded only the cathodic fraction, typical for O antigen. LPS from strains whioh were passaged twice in nutritional medium possessed identical properties as LPS from fresh cultures ofSalmonella typhi. Electron microscopy revealed that LPS appears as long bands, rods, ellipsoid forms and amorphous material. Contrary to amorphous material, the bands, rods and ellipsoid forms possessed three-layer structure.     

Immunoelectrophoretic study of lipopolysaccharide antigens fromVibrio anguillarum strains,serogroup O2

Vibrio anguillarum isolates, derived from feral as well as cultured fish and recorded as serogroup O2 by slide agglutination, were selected for an immunoelectrophoretic study of lipopolysaccharide antigens. Antigenic preparations for the immunoelectrophoretic analyses were simple water extracts, heated to 100°C for 1 h. Two immunoelectrophoretic distinct lipopolysaccharide entities were detected. The analyses did not demonstrate serologic variations in lipopolysaccharide antigens among 16 O group 2 strains. The study also included an O1K1V. anguillarum strain. Antigenic extract from this strain was not precipitated by OK antiserum againstV. anguillarum serogroup O2.     

Monoclonal antibodies against Vibrio anguillarum O2 and Vibrio ordalii identify antigenic differences in lipopolysaccharide O-antigens

Abstract Monoclonal antibodies (mAbs) that recognize distinct species-specific antigenic epitopes in O-antigens from Vibrio anguillarum O2, O2a and certain O2b strains (mAb 7B4) and from Vibrio ordalii strains (mAbs A16 and 7D11) were generated. Western immunoblot analysis using these mAbs revealed that vibrio strains grown in the presence of fresh rainbow trout blood expressed lipopolysaccharide (LPS) with longer (high molecular mass) O-antigens and extracellular capsular layers when compared to strains grown without rainbow trout blood. We also generated mAbs that react with O-antigens from V. anguillarum serotype O1 (mAbs 7B8, 7B5 and 1C3) and serotype O3 (mAbs 13A1 and 14C5) strains. These mAbs provide rapid and accurate diagnostic reagents for serological differentiation of V. ordalii from serotype O2 strains of V. anguillarum , and for serotyping of these pathogenic vibrios.     

Phenotypic characterization and description of two major O-serotypes in Tenacibaculum maritimum strains from marine fishes

Tenacibaculum maritimum is the etiological agent of marine flexibacteriosis disease, with the potential to cause severe mortalities in various cultured marine fishes. The development of effective preventive measures (i.e. vaccination) requires biochemical, serological and genetic knowledge of the pathogen. With this aim, the biochemical and antigenic characteristics of T. maritimum strains isolated from sole, turbot and gilthead sea bream were analysed. Rabbit antisera were prepared against sole and turbot strains to examine the antigenic relationships between the 29 isolates and 3 reference strains. The results of the slide agglutination test, dot-blot assay and immunoblotting of lipopolysaccharides (LPS) and membrane proteins were evaluated. All bacteria studied were biochemically identical to the T. maritimum reference strains. The slide agglutination assays using O-antigens revealed cross-reaction for all strains regardless of the host species and serum employed. However, when the dot-blot assays were performed, the existence of antigenic heterogeneity was demonstrated. This heterogeneity was supported by immunoblot analysis of the LPS, which clearly revealed 2 major serological groups that were distinguishable without the use of absorbed antiserum: Serotypes O1 and O2. These 2 serotypes seem to be host-specfic. In addition, 2 sole isolates and the Japanese reference strains displayed cross-reaction with both sera in all serological assays, and are considered to constitute a minor serotype, O1/O2. Analysis of total and outer membrane proteins revealed that all strains share a considerable number of common bands that are antigenically related.     

Somatic and flagellar antigens ofSerratia ficaria from the United States and the Mediterranean region

Somatic (O) and flagellar (H) antigens of 37Serratia ficaria strains were studied. All strains shared a common H antigen (H1). Four O antigens were identified that defined four serovars (O1:H1, O2:H1, O3:H1, and O4:H1). All American strains studied (isolated from the fig-fig wasp biological cycle or from a human patient) belonged to serotype O1:H1. Strains from the Mediterranean region (Sicily, Tunisia, France) were not so antigenically uniform and all four serotypes were found in figs from Sicily.     

A novel Helicobacter pylori cell-surface polysaccharide

Helicobacter pylori bacteria colonize the gastric mucosa of more than half of the world's human population and its infection may instigate a wide spectrum of gastric diseases in the host. At the moment, there is no vaccine against H. pylori, a microorganism recognized as a category 1 human carcinogen, and treatment is limited to antibiotic management. Pioneering antigenic studies carried out by Penner and co-workers, which employed homologous H. pylori antisera specific for cell-surface lipopolysaccharide (LPS), revealed the presence of six distinct H. pylori serotypes (O1 to O6). Subsequent studies have shown that H. pylori serotype O1 expressed LPS with lengthy O-chain polysaccharide (PS) composed of Lewis blood-group structures ('Lewis O-chains'), serotype O3 LPS produced 'Lewis O-chains' attached to a heptoglycan domain, serotype O4 LPS possessed LPS with glucosylated 'Lewis O-chains' and serotype O6 LPS expressed the heptoglycan domain capped by a short 'Lewis O-chain'. These LPSs were terminated at the reducing-end by a core oligosaccharide and lipid A of conserved structures. With the intent of formulating a multivalent H. pylori LPS-based vaccine, we are studying the structural variability of H. pylori cell-surface glycans. Here, we describe the novel LPS structure produced by H. pylori serotype O2 that differed markedly from the typical H. pylori 'Lewis O-chain' structures, in that its main component was an elongated PS composed of alternating 2-, and 3-monosubstituted alpha-D-Glcp residues [-->2)-alpha-D-Glcp-(1-->3)-alpha-D-Glcp-(1-->]n. These findings revealed the bio-molecular basis for the observed serospecificity of H. pylori serotype O2, and that this unique bacterial PS must be included in the formulation of a multivalent LPS H. pylori vaccine.