Oral delivery of Hyperimmune bovine serum antibodies against CS6-expressing enterotoxigenic Escherichia coli as a prophylactic against diarrhea.

BACKGROUND: . Oral administration of bovine antibodies active against enterotoxigenic Escherichia coli (ETEC) have demonstrated safety and efficacy against diarrhea in human challenge trials. The efficacy of bovine serum immunoglobulins (BSIgG) against recombinant colonization factor CS6 or whole cell ETEC strain B7A was assessed against challenge with the CS6-expressing B7A. METHODS: . This was a randomized, double-blind, placebo-controlled trial in which healthy adults received oral hyperimmune BSIgG anti-CS6, anti-B7A whole cell killed or non-hyperimmune BSIgG (placebo) in a 1:1:1 ratio then challenged with ETEC B7A. Two days pre-challenge, volunteers began a thrice daily, seven day course of immunoprophylaxis. On day 3, subjects received 1 × 1010 CFUs of B7A. Subjects were observed for safety and the primary endpoint of moderate-severe diarrhea (MSD). RESULTS: . A total of 59 volunteers received product and underwent ETEC challenge. The BSIgG products were well-tolerated across all subjects. Upon challenge, 14/20 (70%) placebo recipients developed MSD, compared to 12/19 (63%; p = .74) receiving anti-CS6 BSIgG and 7/20 (35%; p = .06) receiving anti-B7A BSIgG. Immune responses to the ETEC infection were modest across all groups. CONCLUSIONS: . Bovine-derived serum antibodies appear safe and well tolerated. Antibodies derived from cattle immunized with whole cell B7A provided 50% protection against MSD following B7A challenge; however, no protection was observed in subjects receiving serum antibodies targeting CS6. The lack of observed efficacy in this group may be due to low CS6 surface expression on B7A, the high dose challenge inoculum and/or the use of serum derived antibodies versus colostrum-derived antibodies.

Toxins and virulence factors of enterotoxigenic Escherichia coli associated with strains isolated from indigenous children and international visitors to a rural community in Guatemala.

Diarrhoea remains a common cause of illness in Guatemala, with children suffering most frequently from the disease. This study directly compared the frequency, enterotoxin, and colonization factor (CF) profiles of enterotoxigenic Escherichia coli (ETEC) strains isolated from children living in a rural community in Guatemala and from Western visitors to the same location during the same seasons, using similar detection methodologies. We found that ETEC accounted for 26% of severe cases of diarrhoea in children requiring hospitalization, 15% of diarrhoea in the community, and 29% of travellers' diarrhoea in visitors staying ⩾2 weeks. The toxin and CF patterns of the ETEC strains isolated from both groups differed significantly (P < 0·0005) as determined by χ 2 = 60·39 for CFs and χ 2 = 35 for toxins, while ETEC phenotypes found in Guatemalan children were comparable to those found in children from other areas of the world.

Development and preclinical evaluation of a trivalent, formalin-inactivated Shigella whole-cell vaccine.

Studies were undertaken to manufacture a multivalent Shigella inactivated whole-cell vaccine that is safe, effective, and inexpensive. By using several formalin concentrations, temperatures, and incubation periods, an optimized set of inactivation conditions was established for Shigella flexneri 2a, S. sonnei, and S. flexneri 3a to produce inactivated whole cells expressing a full repertoire of Ipa proteins and lipopolysaccharide (LPS). The inactivation conditions selected were treatment with 0.2% formalin (S. flexneri 2a and 3a) or 0.6% formalin (S. sonnei) for 48 h at 25°C. Vaccine formulations prepared under different inactivation conditions, in different doses (10E5, 10E7, and 10E9 cells), and with or without the inclusion of double-mutant heat-labile toxin (dmLT) were evaluated in mice. Two intranasal immunizations with ≥10E7 inactivated whole cells resulted in high levels of anti-Invaplex and moderate levels of LPS-specific IgG and IgA in serum and in lung and intestinal wash samples. Addition of dmLT to the vaccine formulations did not significantly enhance humoral immunogenicity. Minimal humoral responses for IpaB, IpaC, or IpaD were detected after immunization with inactivated whole Shigella cells regardless of the vaccine inactivation conditions. In guinea pigs, monovalent formulations of S. flexneri 2a of 3a or S. sonnei consisting of 10E8, 10E9, or 10E10 cells were protective in a keratoconjunctivitis assay. A trivalent formulation provided protection against all three serotypes (S. flexneri 2a, P = 0.018; S. flexneri 3a, P = 0.04; S. sonnei, P < 0.0001). The inactivated Shigella whole-cell vaccine approach incorporates an uncomplicated manufacturing process that is compatible with multivalency and the future development of a broadly protective Shigella vaccine.

Response of the somatotropic axis to alterations in feed intake of channel catfish (Ictaluruspunctatus).

To better understand the effects of reduced feeding frequency on the GH-IGF-I axis, channel catfish (Ictaluruspunctatus), were either fed (Fed control, commercial diet fed daily), fed every other day (FEOD, commercial diet fed every other day), or not fed (Unfed, no feed). Pituitary GH mRNA increased whereas hepatic growth hormone receptor (GHR), IGF-I mRNA, and plasma IGF-I decreased in the FEOD and Unfed fish (P<0.05). In another study, fish were either continually fed (Fed) or fasted and then re-fed (Restricted) to examine the physiological regulation of somatostatin-14 (SS-14) and SS-22 mRNA. Fasting increased (P<0.05) levels of SS-14 mRNA in the hypothalamus and pancreatic islets (Brockmann bodies) at d 30 while re-feeding decreased SS-14 mRNA to control values in all tissues examined by d 45. Fasting had no effect on levels of SS-22 mRNA in the pancreatic islets whereas SS-22 mRNA was not detected in the stomach or hypothalamus. The results demonstrate that feeding every other day has similar negative impacts on components of the GH-IGF-I axis as fasting. The observed increase in SS-14 mRNA in the hypothalamus and pancreatic islets suggests a role for SS-14 in modulating the GH-IGF-I axis in channel catfish.

Risk factors for antibiotic-resistant E. coli in children in a rural area.

We surveyed antimicrobial susceptibility in faecal Escherichia coli in primary schoolchildren in rural Tamil Nadu, India. Resistance profiles of E. coli samples from local water sources were also obtained. We investigated sociodemographic characteristics as risk factors for resistance and local paediatric prescription patterns. In 119 stool samples, carriage of resistance to 1 antibiotic was 63% and multiple drug resistance was 32%. Resistance outcomes were associated with school of attendance, having a sibling attend the same school, younger age, and less crowded households. Eight of nine water samples were resistant to > or =1 antibiotic. Recent history of medication use was not associated with resistance carriage. Resistance patterns may have been influenced by local paediatric prescription patterns and veterinary antibiotic use. Frequent, low-cost surveillance of commensal resistance can guide development of locally appropriate treatment guidelines. School-based hygiene programmes should be considered as means of limiting the spread of antibiotic resistance.

Safety and immunogenicity of an oral, inactivated, whole-cell vaccine for Shigella sonnei: preclinical studies and a Phase I trial.

Orally delivered, inactivated whole-cell vaccines are safe methods of inducing local and systemic immunity. To increase surface proteins associated with adherence and invasion, Shigella sonnei were grown in BHI broth containing deoxycholate. A whole-cell vaccine (SsWC) was then produced by formalin inactivation. In pre-clinical studies, the SsWC vaccine was immunogenic and protected against S. sonnei-induced keratoconjunctivitis in the guinea pig model. In a randomized, double-blind, placebo-controlled, Phase I study, 10 evaluable subjects received either three doses of SsWC on Days 0, 14, and 28 (N = 3); five doses of SsWC on Days 0, 2, 4, 6, and 28 (N = 4); or placebo (N = 3). Each dose contained 2.0 x 10(10) inactivated cells. Serum and fecal antibodies against SsWC, LPS, and IpaC were measured by ELISA. A > or = 4-fold increase in titer was considered significant. Both SsWC dosing regimens were well tolerated. No fever or severe gastrointestinal symptoms were noted by any of the vaccinated subjects. Antibody responses were similar in the two dosing groups. Serum IgG or IgA responses to SsWC were seen in six of seven vaccinees (86%), to LPS in four of seven (57%), and to IpaC in five of seven (61%). Fecal IgA responses to these three antigens developed in five of five, three of five, and three of five subjects, respectively. Among the seven vaccinees, geometric mean rises in serum IgA levels to all three immunogens were significant; IgG increases trended toward significance (paired one-tailed t-test). We conclude that SsWC was immunogenic and protective in animal studies and well tolerated and immunogenic in a Phase I trial.

Comparison of the antibody in lymphocyte supernatant (ALS) and ELISPOT assays for detection of mucosal immune responses to antigens of enterotoxigenic Escherichia coli in challenged and vaccinated volunteers.

In the present study we compared the ELISPOT and antibody in lymphocyte supernatants (ALS) assays as surrogate measures of mucosal immunity. In separate studies, 20 inpatient volunteers received oral doses of 6 x 10(8) or 4 x 10(9)cfu of ETEC strain E24377A (LT+, ST+, CS1+, CS3+) and 20 subjects received 1 (n = 9) or 2 (n = 11) oral doses of the attenuated ETEC vaccine, PTL-003 expressing CFA/II (CS1+ and CS3+) (2 x 10(9)cfu/dose). Peripheral blood mononuclear cells (PBMCs) from all subjects were assayed for anti-colonization factor or toxin-specific IgA antibody responses using the ALS and ELISPOT procedures. ALS responses were measured using a standard ELISA, as well as by time-resolved fluorescence (TRF). Following challenge with E24377A, significant anti-CS3, CS1 and LT ALS responses were detected in the lymphocyte supernatants of 75-95% of the subjects. A similar proportion (75%) of subjects mounted an ALS response to CFA/II antigen after vaccination with the PTL-003 vaccine. Inter-assay comparisons between ALS and ELISPOT methods also revealed a high degree of correlation in both immunization groups. ALS sensitivity versus the ELISPOT assay for LT, CS3 and CS1-specific responses following challenge were 95%, 94% and 78%, respectively and 83% for the ALS response to CFA/II antigen after vaccination with PTL-003. Correlation coefficients for the LT and CS3 antigens were 0.94 (p<0.001) and 0.82 (p<0.001), respectively after challenge and 0.78 (p<0.001) after vaccination. The association between ALS and ELISPOT for the CS1 antigen was however, significant only when ALS supernatants were tested by TRF (r = 0.91, p<0.001). These results demonstrate the value and flexibility of the ALS assay as an alternative to ELISPOT for the measurement of mucosal immune responses to ETEC antigens, particularly when the complexities of ELISPOT may make it impractical to perform.

Prevention of disease in ferrets fed an inactivated whole cell Campylobacter jejuni vaccine.

Ferrets were used to demonstrate the potential of a killed whole cell vaccine prepared from Campylobacter jejuni to protect against disease. C. jejuni strain 81-176 was grown in BHI broth, formalin-fixed, and resuspended in PBS to a concentration of 10(10) cells per ml. This vaccine (CWC) or live organisms were delivered orally with a nasogastric tube into anesthetized animals treated to reduce gastric acidity and intestinal motility. When 5x10(10) CFU of the vaccine strain (Lior serotype 5) or one of two other serotypes, CGL-7 (Lior 4) or BT44 (Lior 9), was used to challenge the ferrets, all of the animals developed a mucoid diarrhea. If the animals had been challenged with 5x10(9) CFU of the homologous strain 1 month before challenge with 10(10) CFU, 80-100% protection against disease was seen. This protection was also obtained after an initial exposure to the 81-176 strain followed by challenge with either of the heterologous strains. CWC was used to see if protection demonstrated with the live organisms could be produced with the non-living preparation. When 10(9) cells of CWC was given as two doses 7 days apart with or without 25mug of a coadministered mucosal adjuvant, LT(R192G), only 40-60% of the animals were protected. If the regimen was changed to four doses given 48h apart, 80% of the animals were free of diarrhea after subsequent challenge. Increasing the number of cells in the four dose regimen to 10(10) cells did not improve protection. Animals given four doses of 10(10) cells combined with LT(R192G) were subsequently challenged with 10(10) cells of the homologous strain or the heterologous strain CGL-7. The CWC protected against both strains. Serum IgG antibody titers determined by ELISA showed little increase following the CWC four dose vaccination regimen, compared to animals given one dose of the live organism. On subsequent challenge, however, both CWC vaccinated and live-challenged ferrets showed comparable antibody titer increases above those obtained following the initial challenge or vaccination. Western blots were used to show that the immunodominant antigen in vaccinated animals was a 45kDa protein, while in ferrets challenged with live organisms the immunodominant antigen was a 62kDa protein. These data show that the CWC can be used to protect against disease caused by Campylobacter. They also show that protection and serum IgG responses do not depend upon the use of the mucosal adjuvant and that cross protection among some of the major serotypes of Campylobacter responsible for human disease is possible.

Pre-exposure anti-Campylobacter jejuni immunoglobulin a levels associated with reduced risk of Campylobacter diarrhea in adults traveling to Thailand.

Diarrhea history questionnaires were administered to 369 U.S. military volunteers before and after deployment to Thailand. Additionally, blood samples obtained from a subset of 221 volunteers 1-3 weeks previously and 3-4 weeks after their deployment were tested by enzyme-linked immunosorbent assay for immunoglobulin A to Campylobacter jejuni. Stool samples from personnel (including volunteers) contracting diarrhea in Thailand were cultured for enteric pathogens. Overall, 35.2% (130 of 369) of questionnaire respondents reported one or more diarrhea episodes during their trip. Volunteers with pretravel anti-C. jejuni reciprocal titers < or = 450 were 1.6 times as likely to have had diarrhea during their stay in Thailand compared with those with pretravel titers > 450 (39.7% versus 25.3%; P = 0.05). The symptomatic seroconversion, or attributable Campylobacter diarrhea attack rate, for the 1-month exercise was 12.7% (28 of 221). The symptomatic seroconversion rate in nonimmune (titer < or = 450) volunteers was 17.1%, whereas that in immune volunteers was only 4.0% (P = 0.002). Campylobacter jejuni or C. coli were recovered from 32.9% (56 of 170) of stool samples cultured and were the most commonly identified enteropathogens. Campylobacter diarrhea was associated with elevated temperatures, fecal red cells, and fecal white blood cells. The results of this study show that Campylobacter continues to represent a significant health threat to Western travelers to Thailand, but many of these travelers have preexisting Campylobacter immunity that protects them from clinically significant Campylobacter enteritis.

Campylobacter jejuni enteritis.

We report the development of Campylobacter jejuni enteritis in a patient with preexisting humoral and cellular immune recognition of C. jejuni antigens. This is one of few studies in which the immunologic status of a person with regard to C. jejuni before and after C. jejuni infection is directly compared, and it is the only study of which we are aware that includes measurements of cellular immunity. The findings may be important to Campylobacter vaccine development efforts.

Early diagnosis of scrub typhus with a rapid flow assay using recombinant major outer membrane protein antigen (r56) of Orientia tsutsugamushi.

The variable 56-kDa major outer membrane protein of Orientia tsutsugamushi is the immunodominant antigen in human scrub typhus infections. We developed a rapid immunochromatographic flow assay (RFA) for the detection of immunoglobulin M (IgM) and IgG antibodies to O. tsutsugamushi. The RFA employs a truncated recombinant 56-kDa protein from the Karp strain as the antigen. The performance of the RFA was evaluated with a panel of 321 sera (serial bleedings of 85 individuals suspected of scrub typhus) which were collected in the Pescadore Islands, Taiwan, from 1976 to 1977. Among these 85 individuals, IgM tests were negative for 7 cases by both RFA and indirect fluorescence assay (IFA) using Karp whole-cell antigen. In 29 cases specific responses were detected by the RFA earlier than by IFA, 44 cases had the same detection time, and 5 cases were detected earlier by IFA than by RFA. For IgG responses, 4 individuals were negative with both methods, 37 cases exhibited earlier detection by RFA than IFA, 42 cases were detected at the same time, and 2 cases were detected earlier by IFA than by RFA. The sensitivities of RFA detection of antibody in sera from confirmed cases were 74 and 86% for IgM and IgG, respectively. When IgM and IgG results were combined, the sensitivity was 89%. A panel of 78 individual sera collected from patients with no evidence of scrub typhus was used to evaluate the specificity of the RFA. The specificities of the RFA were 99% for IgM and 97% for IgG. The sensitivities of IFA were 53 and 73% for IgM and IgG, respectively, and were 78% when the results of IgM and IgG were combined. The RFA test was significantly better than the IFA test for the early detection of antibody to scrub typhus in primary infections, while both tests were equally sensitive with reinfected individuals.

Campylobacter jejuni cytolethal distending toxin mediates release of interleukin-8 from intestinal epithelial cells.

Live cells of Campylobacter jejuni and Campylobacter coli can induce release of interleukin-8 (IL-8) from INT407 cells. Additionally, membrane fractions of C. jejuni 81-176, but not membrane fractions of C. coli strains, can also induce release of IL-8. Membrane preparations from 81-176 mutants defective in any of the three membrane-associated protein subunits of cytolethal distending toxin (CDT) were unable to induce IL-8. The presence of the three cdt genes on a shuttle plasmid in trans restored both CDT activity and the ability to release IL-8 to membrane fractions. However, CDT mutations did not affect the ability of 81-176 to induce IL-8 during adherence to or invasion of INT407 cells. When C. jejuni cdt genes were transferred on a shuttle plasmid into a C. coli strain lacking CDT, membrane preparations became positive in both CDT and IL-8 assays. Growth of C. jejuni in physiological levels of sodium deoxycholate released all three CDT proteins, as well as CDT activity and IL-8 activity, from membranes into supernatants. Antibodies against recombinant forms of each of the three CDT subunit proteins neutralized both CDT activity and the activity responsible for IL-8 release. The data suggest that C. jejuni can induce IL-8 release from INT407 cells by two independent mechanisms, one of which requires adherence and/or invasion and the second of which requires CDT.

Evaluation of a truncated recombinant flagellin subunit vaccine against Campylobacter jejuni.

A recombinant protein comprising the maltose-binding protein (MBP) of Escherichia coli fused to amino acids 5 to 337 of the FlaA flagellin of Campylobacter coli VC167 was evaluated for immunogenicity and protective efficacy against challenge by a heterologous strain of campylobacter, Campylobacter jejuni 81-176, in two murine models. The sequence of the flaA gene of strain 81-176 revealed a predicted protein which was 98.1% similar to that of VC167 FlaA over the region expressed in the fusion protein. Mice were immunized intranasally with two doses of 3 to 50 microgram of MBP-FlaA, given 8 days apart, with or without 5 microgram of the mutant E. coli heat-labile enterotoxin (LT(R192G)) as a mucosal adjuvant. The full range of MBP-FlaA doses were effective in eliciting antigen-specific serum immunoglobulin G (IgG) responses, and these responses were enhanced by adjuvant use, except in the highest dosing group. Stimulation of FlaA-specific intestinal secretory IgA (sIgA) responses required immunization with higher doses of MBP-FlaA (>/=25 microgram) or coadministration of lower doses with the adjuvant. When vaccinated mice were challenged intranasally 26 days after immunization, the best protection was seen in animals given 50 microgram of MBP-FlaA plus LT(R192G). The protective efficacies of this dose against disease symptoms and intestinal colonization were 81.1 and 84%, respectively. When mice which had been immunized with 50 microgram of MBP-FlaA plus LT(R192G) intranasally were challenged orally with 8 x 10(10), 8 x 10(9), or 8 x 10(8) cells of strain 81-176, the protective efficacies against intestinal colonization at 7 days postinfection were 71.4, 71.4, and 100%, respectively.

Epidemiology of enterotoxigenic Escherichia coli diarrhea in a pediatric cohort in a periurban area of lower Egypt.

Enterotoxigenic Escherichia coli (ETEC) are diverse pathogens that express heat-labile (LT) and/or heat-stable (ST) enterotoxins, yet little is known about whether epidemiologic patterns of pediatric ETEC diarrhea vary by the expressed ETEC toxin phenotype. In total, 242 Egyptian children aged <3 years were prospectively followed in 1993-1995. ETEC episodes were detected during twice-weekly home visits, and asymptomatic ETEC excretion was identified from monthly cross-sectional surveys. ETEC episodes were 0.6 per child-year. ST-only ETEC was 2.6 times (P<.001) more common in warmer than cooler months, while LT-only ETEC showed no seasonal variation. Ownership of a household sanitary latrine, but not breast-feeding, was associated with a lower risk of both enterotoxin phenotypes. Coexpression of a colonization factor by LT- or ST-only ETEC strengthened the association with diarrhea. These findings indicate that the epidemiologic patterns of LT-only and ST-only ETEC are not identical and that disease interventions should include improved household sanitation.

Campylobacter jejuni-stimulated secretion of interleukin-8 by INT407 cells.

Incubation of INT407 cells with various clinical isolates of Campylobacter jejuni resulted in secretion of interleukin-8 (IL-8) at levels ranging from 96 to 554 pg/ml at 24 h. The strains which produced the highest levels of IL-8 secretion were 81-176 and BT44. Induction of IL-8 secretion required live cells of 81-176 and was dependent on de novo protein synthesis. Site-specific mutants of 81-176, which were previously shown to be defective in adherence and invasion, resulted in reduced levels of secretion of IL-8, and cheY mutants of strains 81-176 and 749, which are hyperadherent and hyperinvasive, resulted in higher levels of IL-8 secretion. Another mutant of 81-176, which adheres at about 43% of the wild-type levels but is noninvasive, also showed marked reduction in IL-8 levels, suggesting that invasion is necessary for high levels of IL-8 secretion. When gentamicin was added to INT407 cells at 2 h after infection with 81-176, IL-8 secretion 22 h later was equivalent to that of controls without gentamicin, suggesting that the events which trigger induction and release of IL-8 occur early in the interactions of bacteria and eukaryotic cells.

Mutation in the peb1A locus of Campylobacter jejuni reduces interactions with epithelial cells and intestinal colonization of mice.

Campylobacter jejuni is one of the leading causes of bacterial diarrhea throughout the world. We previously found that PEB1 is a homolog of cluster 3 binding proteins of bacterial ABC transporters and that a C. jejuni adhesin, cell-binding factor 1 (CBF1), if not identical to, contains PEB1. A single protein migrating at approximately 27 to 28 kDa was recognized by anti-CBF1 and anti-PEB1. To determine the role that the operon encoding PEB1 plays in C. jejuni adherence, peb1A, the gene encoding PEB1, was disrupted in strain 81-176 by insertion of a kanamycin resistance gene through homologous recombination. Inactivation of this operon completely abolished expression of CBF1, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. In comparison to the wild-type strain, the mutant strain showed 50- to 100-fold less adherence to and 15-fold less invasion of epithelial cells in culture. Mouse challenge studies showed that the rate and duration of intestinal colonization by the mutant were significantly lower and shorter than with the wild-type strain. In summary, PEB1 is identical to a previously identified cell-binding factor, CBF1, in C. jejuni, and the peb1A locus plays an important role in epithelial cell interactions and in intestinal colonization in a mouse model.

Standardization of measurement of immunoglobulin-secreting cells in human peripheral circulation.

A sensitive, and at times the most sensitive, measurement of human vaccine immunogenicity is enumeration of antibody-secreting cells (ASC) in peripheral blood. However, this assay, which is inherently capable of measurement of the absolute number of antigen-specific ASC, is not standardized. Thus, quantitative comparison of results between laboratories is not currently possible. To address this issue, isotype-specific ASC were enumerated from paired fresh and cryopreserved mononuclear cell (MNC) preparations from healthy adult volunteers resident in either the United States (US group) or Egypt (EG group). Analysis of fresh cells from US volunteers revealed mean numbers of ASC per 10(6) MNC of 617, 7,738, and 868 for immunoglobulin M (IgM), IgG, and IgA, respectively, whereas EG volunteers had 2,086, 7,580, and 1,677 ASC/10(6) MNC for the respective isotypes. Cryopreservation resulted in a slight reduction in group mean IgM, IgG, and IgA ASC (maximum reduction in group mean, 14%), but in no instance were results obtained with cryopreserved cells significantly lower than those obtained with fresh cells. To determine if cryopreservation affected the number of bacterial antigen-specific ASC detected, cells from a group of US adult volunteers who received a single oral dose of a mutated Escherichia coli heat-labile enterotoxin (LT(R192G)) were tested. There was no significant difference (P > 0.05) in the number of antigen-specific IgA or IgG ASC detected between fresh and cryopreserved MNC. The results support the views that ASC assays can be standardized to yield quantitative results and that the methodology can be changed to make the test more practical.

Murine intranasal challenge model for the study of Campylobacter pathogenesis and immunity.

Campylobacter jejuni infection of mice initiated by intranasal administration was investigated as a potential model for studies of pathogenesis and immunity. By using a standard challenge (5 x 10(9) CFU), C. jejuni 81-176 was more virulent for BALB/c (72% mortality) than for C3H/Hej (50%), CBA/CAJ (30%), or C58/J (0%). Intranasal challenge of BALB/c was used to compare the relative virulence of three reference strains; C.jejuni 81-176 was more virulent (killing 83% of challenged mice) than C. jejuni HC (0%) or C. coli VC-167 (0%). The course of intranasally initiated C. jejuni 81-176 infection in BALB/c was determined. C. jejuni was recovered from the lungs, intestinal tract, liver, and spleen at 4 h after challenge, the first interval evaluated. After this initial interval, three distinct patterns of infection were recognized: (i) a progressive decline in number of C. jejuni CFU (stomach, blood, lungs), (ii) decline followed by a second peak in the number of organisms recovered at 2 or 3 days postchallenge (intestine, liver, mesenteric lymph nodes), and (iii) persistence of approximately the same number of C.jejuni CFU during the course of the experiment (spleen). Intranasally induced infection initiated with a sublethal number of bacteria or intranasal immunization with killed Campylobacter preparations resulted in both the generation of Campylobacter antigen-specific immune responses and an acquired resistance to homologous rechallenge. The model was used to evaluate the relative virulence of nine low-in vitro-passage (no more than five passages) isolates of C. jejuni species from patients with diarrhea. The patient isolates were differentially virulent for mice; one killed all exposed mice, three were avirulent (no deaths) and the remainder showed an intermediate virulence, killing 17 to 33%. Mouse virulence of Campylobacter strains showed a trend toward isolates originating from individuals with watery diarrhea; however, no association was found between mouse virulence and other signs or symptoms. There were no observed relationships between mouse virulence and bacterial Lior serotype or Fla polymorphic group. Intranasal challenge of BALB/c with C. jejuni is a useful model for the study of infection and vaccination-acquired immunity to this agent.

Serum antibody to lipopolysaccharide antigens of Shigella species among U.S. military personnel deployed to Saudi Arabia and Kuwait during Operations Desert Shield and Desert Storm.

During Operations Desert Shield and Desert Storm, U.S. troops were at high risk of diarrheal disease due to Shigella spp., particularly Shigella sonnei. In order to better understand the serologic response to Shigella infection, 830 male U.S. combat troops were evaluated before and after the deployment to Saudi Arabia and Kuwait for immunoglobulin A (IgA) and IgG anti-Shigella lipopolysaccharide (LPS) (antibody to S. sonnei form I and Shigella flexneri serotypes 1a, 2a, and 3a) in serum. Just before deployment, 10.3% of the subjects were seropositive for IgA and 18.3% were positive for IgG anti-Shigella LPS. IgA and IgG anti-LPS antibody levels in serum prior to deployment were significantly associated with nonwhite race and ethnicity, birth outside the United States, and antibody to hepatitis A virus and Helicobacter pylori. During the deployment, which lasted for a mean of 131 days, 60% of the subjects reported at least one episode of diarrhea and 15% reported an episode of diarrhea with feverishness; also, 5.5% of the subjects exhibited IgA seroconversion to Shigella LPS and 14.0% exhibited IgG seroconversion. A significant association between the development of diarrheal symptoms and either positive predeployment anti-LPS antibody or seroconversion was not found. These data indicate that in this population of U.S. Desert Storm troops who were at high risk of Shigella infection, there was no apparent relation between IgA or IgG anti-Shigella LPS in serum and diarrheal disease.

Immunogenicity and protective efficacy of a prototype Campylobacter killed whole-cell vaccine in mice.

The immunogenicity and efficacy of an experimental inactivated Campylobacter jejuni whole-cell (CWC) vaccine were evaluated in mice. Mice were orally immunized in a three-dose primary series (48-h intervals) at doses of 10(5), 10(7), or 10(9) CWC vaccine particles alone or in combination with 25 micrograms of a mucosal adjuvant, the heat-labile enterotoxin of Escherichia coli (LT). The comparative immunogenicities of both formulations were assessed on the basis of the generation of antigen-specific antibodies in serum and intestinal secretions, and efficacy was determined by measuring the degrees of protection afforded against intestinal colonization and systemic dissemination of challenge organisms. Campylobacter-specific intestinal immunoglobulin (Ig) A responses were dependent on the use of LT, whereas IgA and IgG responses in serum were not. Colonization resistance was induced over a broad range of vaccine doses when LT was included. However, only the highest dose of CWC alone gave comparable levels of protection. Both formulations provided equivalent protection against systemic spread of challenge organisms. These results indicate that both whole-cell vaccine formulations deserve further evaluation as candidate vaccines and also highlight the potential value of mucosal adjuvants, like LT, in enteric vaccine development.