Production of Vibrio cholerae O1 and non-O1 typing sera in rabbits immunized with polysaccharide-protein carrier conjugates.

Two systems are currently used to serologically type Vibrio cholerae O1 and non-O1 isolates. Antiserovar-serotype serum in the Smith system is produced in rabbits immunized with live whole-cell vaccines, and that in the Sakazaki system is produced in rabbits immunized with heat-killed vaccines. In neither system is the serovar-serotype-specific antigen clearly defined. During the course of a serological survey, ca. 10% of more than 2,500 V. cholerae isolates examined agglutinated in the optimal dilutions of two, three, or four different anti-serovar sera prepared by the methods of Sakazaki. An occasional isolate agglutinated in both anti-O1 and non-O1 sera. Lipopolysaccharide was extracted from eight of these possible multiple serovars, coated onto rabbit erythrocytes, and retested in these same antisera by passive hemagglutination. With one exception the lipopolysaccharide-rabbit erythrocytes were now agglutinated in a single antiserum. Antipolysaccharide sera were produced in rabbits immunized with the polysaccharide moiety extracted from eight non-O1 and two O1 vaccine strains conjugated to bovine gamma globulin protein carrier. The antipolysaccharide sera showed passive hemagglutination titers versus lipopolysaccharide-rabbit erythrocytes comparable to those achieved in antisera from rabbits immunized with heat-killed whole-cell vaccines. In the slide agglutination test antipolysaccharide sera serologically discriminated between two O1 isolates that were previously agglutinated in both anti-O1 and anti-non-O1 whole-cell sera. It is recommended that serological types or varieties of V. cholerae non-O1 be based upon serologically recognizable differences in lipopolysaccharide-associated antigens as are antigens A, B, and C in the O1 group.     

Type-specific indirect hemagglutinating antibody in patients with Pseudomonas aeruginosa Infection.

Lipopolysaccharide antigens were extracted from heated cell extracts of several serotypes of Pseudonomas aeruginosa. Indirect hemagglutination with the extracts indicated specific reactivity with sera from rabbits immunized with homologous serotypes of P. aeruginosa. Sera from healthy adults and patients infected with P. aeruginosa were studied subsequently and shown to possess antibodies against P. aeurginosa. In patients infected with P. aeruginosa type E, indirect hemagglutination antibody against type E was resistant to 2-mercaptoethanol (2-ME) and classified as immunoglobulin G. In patients infected with any other type of P. aeruginosa and in healthy adults, it was sensitive to 2-ME and classified as immunoglobulin M. The antibody in the seven patients infected with P. aeruginosa was titrated during the course of infection with lipopolysaccharide antigen prepared from the infecting strain. As a result, all patients either possessed 2-ME-resistant antibody or showed antibody rise to homotypic antigen during the infection. However, no patient showed 2-ME-resistant antibody against hetero-typic lipopolysaccharide antigens. In hospitalized patients, the incidence of anti body against type E, G, and I Pseudomonas strains was greater than that against type A. In particular, 2-ME-resistant antibody to all four serotypes was detected at a higher rate in hospitalized patients than in healthy adults.     

Enzyme-linked immunosorbent assay for immunoglobulin G antibody to Pasteurella multocida in rabbits.

Three antigen preparations of Pasteurella multocida, lipopolysaccharide antigen, boiled-cell extract antigen, and boiled whole-bacterium antigen, were used in an enzyme-linked immunosorbent assay (ELISA) to detect rabbit immunoglobulin G antibody to P. multocida. The sensitivity of each antigen preparation was compared by using sera from P. multocida-infected and uninfected rabbits and sera from two rabbits immunized with different serotypes of P. multocida. In the ELISA, all three antigen preparations detected high titers of antibodies in infected rabbits and markedly lower levels in uninfected rabbits. When whole-bacterium or boiled-cell extract antigens were used, the ELISA detected antibodies in sera from both immunized rabbits, but with lipopolysaccharide antigen, only antibody to the homologous serotype was detected. Sera absorbed with P. multocida and Bordetella bronchiseptica, another respiratory pathogen of rabbits, revealed that antibodies detected in the ELISA did not cross-react. Since the lipopolysaccharide antigen was more difficult to prepare and may be type specific, and since the whole-bacterium antigen was the least sensitive, the boiled-cell extract was chosen as the best antigen preparation to use in the ELISA.     

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis immunoblotting as a serological tool in the diagnosis of syphilitic infections.

The utility of sodium dodecyl sulfate-polyacrylamide gel electrophoresis immunoblotting as a serological tool in the diagnosis of human syphilitic infections was examined. In model experiments, rabbits were immunized with Treponema pallidum or T phagedenis, and the antisera were tested for cross-reactivities with both sets of antigens. A major T. pallidum antigen with a molecular weight of ca. 17,000 appeared to be the most reliable specific antigenic marker as assessed by the immunoblotting technique with peroxidase-labeled second antibodies. Antibodies to this antigen were never detected in hyperimmune rabbit anti-T. phagedenis sera or in the sera of nonsyphilitic humans. In contrast, reactive antibodies were found in all syphilitic human sera and also in liquor samples that were positive in the passive hemagglutination test. Differentiation between immunoglobulin M and immunoglobulin G antibodies was directly possible by applying the respective specific second antibodies. Immunoblotting tests were performed with sera exhibiting low passive hemagglutination test titers and equivocal fluorescent treponemal antibody and rapid plasma reagin card reactions. In more than 60% of these cases, immunoblot positivity with respect to the 17,000-molecular-weight antigen was found. The same results were obtained with partially purified 17,000-molecular-weight antigen. The immunoblot technique should be useful as an additional diagnostic tool for differentiating between true and false-positive serological reactions.     

7株O139霍乱弧菌CT基因阴性菌的生物学性状研究

目的拟从毒力基因ｃｔｘ阴性的Ｏ１３９霍乱弧菌中筛选疫苗候选株。方法用常规鉴定技术、Ｓｏｕｔｈｅｒｎｂｌｏｔｉｎｇ技术和兔肠段结扎试验检测了７株霍乱肠毒素（ＣＴ）基因阴性的Ｏ１３９霍乱弧菌的一般特性、毒性和毒性基因;通过小肠免疫家兔,用ＰＢＬ－ＥＬＩＳＡ、ＥＬＩＳＡ和杀弧菌抗体试验评价抗原性;用家兔主动保护试验和乳鼠被动保护试验研究保护效果。结果７株菌都具有Ｏ１３９霍乱弧菌的一般特性,均不引起肠段积液,毒力基因ｃｔｘ、ｚｏｔ、ａｃｅ和ＲＳ１探针杂交结果均为阴性。Ｂ１３和９４００１免疫后０～２８天血清抗体ＩｇＧ效价一直上升,而９４００２免疫后１４天最高;９４００２的血清杀弧菌抗体峰值最高。Ｂ１３免疫家兔后可保护１０５ＣＦＵ毒株的攻击,９４００１和９４００２免疫后可保护１０５～７ＣＦＵ毒株的攻击,９４００２加强免疫后能保护１０７ＣＦＵ毒株的攻击。Ｂ１３免疫血清１４稀释后对乳鼠的保护率为２０％,９４００１和９４００２的免疫血清１１６稀释后的保护率为５０％。结论７株Ｏ１３９霍乱弧菌属于毒力基因遗传单元缺失,无毒或毒性低,其中９４００２的免疫原性和保护效果较好,且初次免疫后存在免疫记忆     

Serological and biological activities of anti-Haemophilus influenzae ribosomal serum.

The antibody content in serum from rabbits immunized with ribosomes from Haemophilus influenzae type b was determined by passive hemagglutination, enzyme-linked immunosorbent assay, and complement fixation. Attempts to use passive hemagglutination to assay anti-ribosomal antibodies were unsuccessful. In the enzyme-linked immunosorbent assay tests, rabbit antiserum was allowed to react with ribosomes that adhered to microtiter plates. The enzyme-linked immunosorbent assay method detected, in two ribosome-immunized rabbits and by 3 days postimmunization, titers which rose to plateaus on days 24 to 31 and declined thereafter. With the complement fixation method, the serum from one immunized rabbit also showed a titer on day 3 and reached a plateau on days 20 to 31. Serum from the other immunized rabbit did not develop a titer until day 11; it reached a lower plateau on days 20 to 24 and then declined on days 27 to 55. Although there were no apparent differences between the two immunized rabbits by the enzyme-linked immunosorbent assay, there were differences between the complement fixation antibodies in these rabbits. Passive protection experiments were performed with these sera. Maximal passive protection was achieved when mice were challenged intraperitoneally with 100 50% lethal doses of H. influenzae and immunized intravenously 1 h later with rabbit serum collected 27 days postimmunization. Rabbit anti-ribosomal sera were evaluated for bactericidal activity. Undiluted immune sera showed bactericidal activity; however, when diluted 1:10, activity was lost. Although bactericidal activities of immune sera were correlated to passive protection activities, it is unlikely that such protection was due to bactericidal antibodies. Immune serum had opsonizing activity since it enhanced phagocytosis of H. influenzae by mouse leukocytes.     

Antigenic Specificity of Neutralizing Antibody to Cholera Toxin

Selected rabbit antisera to cholera toxin antigens and convalescent cholera patient sera were analyzed using the permeability factor neutralization test and two sensitive in vitro serological assays specific for cholera toxin, cholera toxin A subunit, and cholera toxin B subunit. The results indicated that antisera to cholera toxin contained toxin-neutralizing activity as well as antibodies specific for both the A subunit and B subunit. It was clearly established that antisera to B subunit, devoid of significant anti-A subunit activity, neutralized the vascular permeability activity of cholera toxin. Antisera to A subunit contained neutralizing antibodies and antibodies to both A and B subunits. Absorption with B subunit removed both the toxin-neutralizing and anti-B subunit activities, while the anti-A activity was unaffected. Neutralizing antibody titers of rabbits immunized with B subunit were also observed to be significantly higher than neutralizing antibody titers of sera from A subunit-immunized rabbits, despite the overall similarity in anti-B subunit titers as determined by passive hemagglutination and radioimmunoassay of sera from the two groups of rabbits. Anti-alpha chain sera neither neutralized cholera toxin nor possessed significant antitoxin or anti-B subunit titers as determined by passive hemagglutination and radioimmunoassay. The anti-alpha chain sera contained high levels of antibody specific for A subunit, which is consistent with the hypothesis that the alpha chain is part of the A subunit structure. In contrast, the gamma chain was not shown to be antigenic. Sera from convalescent cholera patients possessed toxin-neutralizing antibody as well as passive hemagglutination and radioimmunoassay antibody against both A and B subunits.     

Agglutinating antibody titers to members of the family Legionellaceae in cystic fibrosis patients as a result of cross-reacting antibodies to Pseudomonas aeruginosa.

The objective of this study was to evaluate the prevalence and significance of antibody titers to organisms in the family Legionellaceae in 128 serum samples collected from cystic fibrosis patients at routine examinations. Antibody titers were determined for 10 antigenic types of Legionellaceae; Legionella pneumophila serogroups 1 to 6, Fluoribacter (Legionella) bozemanae, Fluoribacter (Legionella) dumoffii, Fluoribacter (Legionella) gormanii, and Tatlockia (Legionella) micdadei. The method of antibody titer determination was the microagglutination test. Elevated titers (greater than or equal to 1:64) to one or more antigens were found in 41.3% of cystic fibrosis patients but in only 9.7% of 103 normal control subjects (P less than 0.01). Titers to 8 of the 10 antigens were directly correlated with the number of Pseudomonas aeruginosa precipitating antibodies in patient sera, as determined by crossed immunoelectrophoresis (correlation coefficients, greater than or equal to 0.74). Cross-reactions between P. aeruginosa and L. pneumophila were substantiated by crossed immunoelectrophoresis of hyperimmune rabbit serum as well as patient sera against P. aeruginosa and Legionellaceae antigens. Monospecific antibody to the "common antigen" of P. aeruginosa was used to demonstrate the presence of this antigen in L. pneumophila. The presence of cross-reacting antibodies in cystic fibrosis patients chronically infected with P. aeruginosa emphasizes the need for cautious interpretation of antibody titers to members of the family Legionellaceae.     

Human monoclonal antibodies against Pseudomonas aeruginosa lipopolysaccharide derived from transgenic mice containing megabase human immunoglobulin loci are opsonic and protective against fatal pseudomonas sepsis

Pseudomonas aeruginosa is a significant human pathogen, and no vaccine is commercially available. Passive antibody prophylaxis using monoclonal antibodies (MAb) against protective P. aeruginosa epitopes is an alternative strategy for preventing P. aeruginosa infection, but mouse MAb are not suitable for use in humans. Polyclonal human antibodies from multiple donors have variable antibody titers, and human MAb are difficult to make. We used immunoglobulin-inactivated transgenic mice reconstituted with megabase-size human immunoglobulin loci to generate a human MAb against the polysaccharide (PS) portion of the lipopolysaccharide O side chain of a common pathogenic serogroup of P. aeruginosa, 06ad. The anti-PS human immunoglobulin G2 MAb made from mice immunized with heat-killed P. aeruginosa was specific for serogroup 06ad pseudomonas. The MAb was highly opsonic for the uptake and killing of P. aeruginosa by human polymorphonuclear leukocytes in the presence of human complement. In addition, 25 microg of the MAb protected 100% of neutropenic mice from fatal P. aeruginosa sepsis. DNA sequence analysis of the genes encoding the MAb revealed V(H)3 and Vkappa2/A2 variable-region genes, similar to variable-region genes in humans immunized with bacterial PS and associated with high-avidity anti-PS antibodies. We conclude that human MAb to P. aeruginosa made in these transgenic mice are highly protective and that these mice mimic the antibody response seen in humans immunized with T-cell-independent antigens such as bacterial PS.     

Enzyme-linked immunospecific antibody test for detecting antibody to Klebsiella.

The enzyme-linked immunospecific antibody test was performed in standard test tubes and microtiter plates to meausre high-titer antibody against Klebsiella capsular polysaccharide. Initial studies were conducted with rabbit sera; other studies were conducted with the serum of a patient infected with type 9 Klebsiella. Both immunized rabbits and an infected patient disclosed high titers of anticapsular antibody. Control sera from other immunized rabbits and other infected humans failed to show this substantial antibody titer against type 9 Klebsiella. Comparisons between counterimmunoelectrophoresis and indirect immunofluorescence disclosed that the sensitivity of the enzyme-linked immunospecific antibody test for anti-Klebsiella antibody ranged between 400 and 10,000 times that of these tests.     

Serological differentiation between infected and vaccinated cattle by using purified soluble antigens from Brucella abortus in a hemagglutination system.

Serological tests used in current brucellosis eradication schemes, such as bacterial tube agglutination, do not readily distinguish between infected animals and those immunized with strain 19 or 45/20 Brucella abortus vaccines. In this study, sera from naturally infected cattle were used to identify serologically important antigens in extracts of virulent B. abortus by gel diffusion techniques. Antisera from rabbits hyperimmunized with selected precipitation lines were used for purification by affinity chromatography of two precipitating and one non-precipitating antigen from crude bacterial extracts. A passive hemagglutination test using these antigens was developed. A number of characterized bovine sera were screened by passive hemagglutination and conventional bacterial tube agglutination test. A considerable improvement in discrimination between sera from infected and vaccinated cattle was obtained with the hemagglutination test compared with bacterial tube agglutination.     

Production of leukocidin by clinical isolates of Pseudomonas aeruginosa and antileukocidin antibody from sera of patients with diffuse panbronchiolitis.

The ratio of leukocidin-producing strains to clinical isolates of Pseudomonas aeruginosa was investigated together with the production of protease, elastase, and exotoxin A. We also examined whether these strains contain the common antigen which resides in the cell wall. By using the agar gel diffusion test with specific antisera, we found that 87 of 90 (96.7%) of clinical isolates produced leukocidin. Protease, elastase, and exotoxin A were also produced at high percentages. The common antigen was found to exist in all strains. Next, to estimate antileukocidin antibody in the sera of patients, we used an enzyme-linked immunosorbent assay with horseradish peroxidase-protein A. The sera of 39 patients with diffuse panbronchiolitis (DPB) were investigated for antileukocidin antibody. The mean antileukocidin titer in the sera of 17 DPB patients who were not infected with P. aeruginosa and 5 DPB patients who were transiently infected with the bacteria was about the same as the mean antileukocidin titer in the sera of 11 healthy controls, whereas the mean antileukocidin titer in the sera of 17 DPB patients who were persistently colonized was significantly higher than that in healthy controls. These results indicate that leukocidin was produced at the local site of infection in DPB patients.     

The Production of Anti-A1 Agglutinins in A-Like Rabbits Injected with Human Group A1 Erythrocytes

A-like and non-A-like rabbits were injected with human group A₁ erythrocytes. The rabbit sera were examined serologically for their hemagglutination patterns with human red cells of groups A₁ and A₂ before and after sequential adsorption with human group O, B and A₂ erythrocytes. The A-like rabbits produced specific anti-A₁ heteroagglutinins that resisted further adsorptions with group A₂ cells. The tissues of A-like rabbits obviously do not contain antigenic configurations equivalent to those on human group A₁ erythrocytes. Cross-reacting antibodies were also formed, by the non-A-like rabbits especially, as evidenced by the increased titer of agglutinins reactive with human group B red cells.     

Role of Nonagglutinating Antibody in the Protracted Immunity of Vaccinated Mice to Pseudomonas aeruginosa Infection

Effective immunization against infection with Pseudomonas aeruginosa is difficult to evaluate because agglutinin levels decline rapidly. Because fractionation of hyperimmune sera often yields more specific antibody than can be accounted for by direct agglutination tests, an immunoglobulin-specific assay based on antiglobulin augmentation was used to characterize antibody responses of C3H/HeJ mice vaccinated with P. aeruginosa type 2 lipopolysaccharide. Nonagglutinating antibodies, initially detected at 2 weeks post-primary vaccination, were predominantly immunoglobulin G after 5 weeks, and they remained elevated at levels usually 32-fold higher than the direct titer throughout the 4-month study period. The sequential production of immunoglobulin M, then immunoglobulin G, followed that found in orthodox immunological responses. Sera that contained nonagglutinating antibodies but not direct agglutinins (14 to 16 weeks) enhanced phagocytosis of P. aeruginosa type 2 by macrophages from unimmunized mice and passively immunized mice against lethal challenge doses; bactericidal activity of these sera was not demonstrated in the presence or absence of complement. When challenged with 1, 10, and 100 50% lethal doses at 16 weeks, survival rates of actively immunized mice were significantly higher than those of unvaccinated mice (P < 0.001). Thus, at a time when no direct agglutinins were detectable, the augmented system detected nonagglutinating antibodies that could confer protracted resistance in vaccinated mice to pseudomonas infection.     

Detection of Antibodies to Pasteurella multocida by capture enzyme immunoassay using a monoclonal antibody against P37 antigen.

As infection with Pasteurella multocida is common in rabbits, an enzyme immunoassay (EIA) was developed for its detection. A murine immunoglobulin G monoclonal antibody was used to capture a 37-kDa polypeptide of P. multocida serotype A:12 in an EIA to detect antibodies to P. multocida. The 37-kDa antigen was selected since it was previously shown to be a major immunogen during P. multocida infection in rabbits. The sensitivity of the P37 EIA, determined with sera from 56 rabbits infected with P. multocida, was 98%. Specificity, evaluated with sera from 62 rabbits from colonies free of P. multocida, was 92%. Titration curves of sera from rabbits immunized with P. multocida serotype A:3 or A:12 coincided, indicating that the P37 EIA was equally efficient in detecting antibodies to the two major serotypes of the organism. Comparison of the P37 EIA with the current serodiagnostic test, a bacterial lysate EIA, revealed relatively good correlation (r = 0.68). However, specificity was greatly improved, as 34% of uninfected rabbits were falsely positive by the lysate EIA whereas only 3% of uninfected rabbits were falsely positive by the P37 EIA. The coefficient of variation for same-day tests was 10%, and that for interday tests was 15%, indicating good reproducibility. The greater sensitivity and specificity of the P37 EIA should significantly enhance diagnostic capability to identify rabbits infected with P. multocida.     

Passive immunization against Pseudomonas with a ribosomal vaccine-induced immune serum and immunoglobulin fractions.

Passive protection of mice against Pseudomonas aeruginosa using specific antisera and immunoglobulin fractions induced by immunizing rabbits with a ribosomal vaccine is reported. The results demonstrated that protection by the ribosomal vaccine against challenge with live organisms can be serum mediated. Previous work has shown that the vaccine can be separated into two components on the basis of molecular weight and that both higher (peak A)- and lower (peak B)-molecular-weight fractions were capable of inducing active immunity in mice. The present report indicates that both fractions are also capable of eliciting the production of mouse-protective antibody in rabbits. Agar gel diffusion with antisera to peaks A and B or unfractionated vaccine indicated a common antigenic component among them in addition to an extra antigen in unfractionated vaccine not present in peak B. Passive hemagglutination with antisera to peaks A and B demonstrated high-titer agglutinating antibody only with antiserum to peak A when a method of erythrocyte sensitization for lipopolysaccharide antigens was used. Also, passive hemagglutination was greatly inhibited by small amounts of lipopolysaccharide prepared from the same organism from which the vaccine was made. Both antisera to peaks A and B fixed complement with either A or B antigens. Antisera to peaks A and B, when reacted with peak B antigen, had about the same complement fixation titer (as determined by a quantitative complement fixation test). However, when peak A antigen was used, antiserum to peak A had about twice the complement fixation titer that antiserum to peak B had. These results are consistent with previous observations which suggest that the ribosomal vaccine contains lipopolysaccharide in addition to an unidentified immunogenic principle associated with ribosomes. Furthermore, this immunogen was present in both peaks A and B, but detectable amounts of lipopolysaccharide were present only in peak A. The relative importance of the immunoglobulin G (IgG) and IgM classes of antibodies was also compared. The results indicated that both IgG and IgM isolated from immune rabbit serum are protective in mice. Only IgG precipitated with the vaccine in agar gel diffusion, but both IgG and IgM were active in passive hemagglutination and in complement fixation. The passive hemagglutination titer of the IgM was higher than that of the IgG, but the complement fixation titer of the IgG was higher than that of the IgM. The mouse-protective capability of the IgG and IgM was about the same.     

Immunogenicity and protective role of an IgA reactive 31-kDa antigen of Vibrio cholerae O139

Immunoglobulin A (IgA) is important in protective immunity against infection by Vibrio cholerae. In this study, the immune response to and protective role of a 31-kDa antigen of V. cholerae O139, reacting with IgA antibodies present in the sera of cholera patients and common to V. cholerae strains O139 and O1 was evaluated in BALB/c mice. From the various antigens of V. cholerae O139 and V. cholerae O1 which reacted with IgA antibodies in sera of a cholera patient, a 31-kDa common antigen was selected and purified by DEAE-Sepharose CL 6B column chromatography. Oral administration of live V. cholerae O139 in BALB/c mice elicited an IgA response to the 31-kDa antigen in serum and intestinal fluid, and a proliferation of the splenic lymphocytes on stimulation with the same antigen. The cytokine profile of these splenic lymphocytes revealed a shift from a mixed Th1 and Th2 response--interleukin-10 (IL-10) and interferon-gamma--in the first week after infection to a Th2 type of response--IL-10--in the third week. In passive protection studies, hyperimmune serum to the 31-kDa antigen was able to protect infant mice against challenge with O139 and O1 strains. These results demonstrate the ability of the 31-kDa antigen of V. cholerae O139 to induce humoral and cellular immune responses in mice, and its immunoprotective nature.     

Enterotoxin-specific immunoglobulin E responses in humans after infection or vaccination with diarrhea-causing enteropathogens

Cholera toxin (CT)-specific antibody responses of the immunoglobulin E (IgE) isotype in the sera of adult patients suffering from infection with either Vibrio cholerae O1, V. cholerae O139, or enterotoxigenic Escherichia coli (ETEC) were analyzed and compared with those in the sera of volunteers immunized with a bivalent B subunit O1/O139 whole-cell cholera vaccine. A significant IgE response to CT was observed in 90% of the patients with V. cholerae O1 infection (18 of 20; P = <0.001) and 95% of the patients with V. cholerae O139 infection (19 of 20; P = <0.001). Similarly, the majority of the patients with ETEC diarrhea (83%; 13 of 15) showed a positive IgE response to CT. Eight of 10 North American volunteers (80%) orally challenged with V. cholerae O1 showed CT-specific IgE responses (P = 0.004). In contrast, Swedish volunteers immunized with the oral cholera vaccine showed no IgE responses to CT (P value not significant). During the study period, total IgE levels in the sera of the diarrheal patients, the North American volunteers, and the Swedish cholera vaccinees alike remained unchanged. However, the total IgE levels in the sera of patients and healthy Bangladeshi controls were on average 89-fold higher than those in the sera of the healthy Swedish volunteers and 34-fold higher than those in the sera of the North American volunteers.     

Humoral antibody response of rabbits against experimental Serratia marcescens septicemia

Rabbits reconvalescent from experimental septicemia due to serologically defined strains of Serratia marcescens were examined for the diversity of their humoral antibody response with traditional serological procedures and the Western blot (immunoblotting) technique. Trichloracetic acid (TCA)-whole cell extracts of the homologous and heterologous O-antigen reference strains served as the antigen for the latter procedure. Reconvalescent rabbit sera contained antibodies against the homologous lipopolysaccharide (LPS) moiety (molecular weight (MW) range = 45-31 kilodaltons (= k] and antibodies against numerous heat-modifiable, cross-reactive proteins, in particular 7 proteins characterized by MWs of 117 k, 95 k, 91 k, 71 k, 68 k, 38 k, and 33 k in TCA-whole cell extracts from the homologous as well as from 11 heterologous S. marcescens O-antigen reference strains. Rabbits, which had been actively immunized with TCA-whole cell extracts from representative S. marcescens strains, mounted a humoral antibody response remarkably similar to that of rabbits which had recovered from septicemia, except that the sera from the actively immunized animals interacted somewhat more strongly with an additional cross-reactive protein (MW = 47 k). Conversely, conventional anti-O and anti-H rabbit immune sera revealed antibodies directed predominantly against the homologous LPS moiety (MW range = greater than or equal to 200 k - less than or equal to 15 k). It was concluded that numerous proteinaceous cellular constituents of S. marcescens accounted for immunoblot cross-reactivity.     

Immunoglobulins in bile and serum of the rabbit associated with protection after Vibrio cholerae infection and vaccination

Previous studies have shown that cholera, as well as protective immunity against infection with Vibrio cholerae, can be induced in the rabbit. This protection is long-lasting (up to 30 months) and is characterized on challenge by rapid, symptom-free disappearance of V. cholerae from the intestine; we therefore believe this to be vibriocidal protection. In this study, we analysed the humoral and secretory immune response against various subcellular V. cholerae components in vibriocidally protected, non-vibriocidally protected, and unprotected animals. Only vibriocidal protection was found to be associated with high levels of biliary IgA directed against lipopolysaccharide O antigen. We did not find such a correlation between either type of protection and response in serum. Therefore, anti-lipopolysaccharide antibodies are essential in protection against experimental infection with V. cholerae.