Antigenic response to CT-P13 and infliximab originator in inflammatory bowel disease patients shows similar epitope recognition.

AIM: To test the cross-immunogenicity of anti-CT-P13 IBD patients' sera to CT-P13/infliximab originator and the comparative antigenicity evoked by CT-P13/infliximab originator sera. METHODS: Sera of patients with IBD with measurable anti-CT-P13 antibodies were tested for their cross-reactivity to 5 batches of infliximab originator and CT-P13. Anti-drug antibody positive sera from treated patients were used to compare antigenic epitopes. RESULTS: All 42 anti-CT-P13 and 37 anti-infliximab originator IBD sera were cross-reactive with infliximab originator and CT-P13 respectively. Concentration of anti-drug antibodies against infliximab originator or CT-P13 were strongly correlated both for IgG1 and IgG4 (P < 0.001). Anti-CT-P13 sera of patients with IBD (n = 32) exerted similar functional inhibition on CT-P13 or infliximab originator TNF binding capacity and showed reduced binding to CT-P13 in the presence of five different batches of CT-P13 and infliximab originator. Anti-CT-P13 and anti-infliximab originator IBD sera selectively enriched phage-peptides from the VH (CDR1 and CDR3) and VL domains (CDR2 and CDR3) of infliximab. Sera reactivity detected major infliximab epitopes in these regions of infliximab in 60%-79% of patients, and no significant differences were identified between CT-P13 and infliximab originator immunogenic sera. Minor epitopes were localised in framework regions of infliximab with reduced antibody reactivity shown, in 30%-50% of patients. Monoclonal antibodies derived from naïve individuals and ADA-positive IBD patients treated with CT-P13 provided comparable epitope specificity to five different batches of CT-P13 and infliximab originator. CONCLUSIONS: These results strongly support a similar antigenic profile for infliximab originator and CT-P13, and point toward a safe switching between the two drugs in anti-drug antibody negative patients.

Safety, efficacy and pharmacokinetics of vedolizumab in patients with simultaneous exposure to an anti-tumour necrosis factor.

BACKGROUND: Data on combination-biologic treatment in (IBD) are still scant. AIM: To explore outcomes of patients co-exposed to anti-TNF and vedolizumab. METHODS: Patients starting vedolizumab having measurable anti-TNF levels after recently stopping adalimumab/infliximab ('VDZ-aTNF' group), were compared with control vedolizumab patients in a retrospective 1:2 matched case-control study. RESULTS: Seventy-five patients were included (25 VDZ-aTNF, 50 VDZ). Adverse events were experienced by 9/25 VDZ-aTNF compared to 13/50 VDZ patients (P = 0.4, follow-up 14 weeks in all). Week 14 clinical remission was attained in 10/25 (40%) of VDZ-aTNF patients versus 23/50 (46%) of VDZ patients (OR = 0.8, 95% CI 0.3-2.1, P = 0.6) and clinical response in 19/25 (76%) versus 39/50 (78%) respectively (OR = 0.9, 95% CI 0.3-2.7, P = 0.8). Corticosteroid-free remission and corticosteroid-free response were experienced by 30% and 54%, respectively, of the entire cohort, and were similar between the two groups. Vedolizumab drug concentrations at week 2, 6 and 14 were similar among VDZ-aTNF and VDZ patients (P > 0.5). Multi-variable analysis showed independent association of some vedolizumab drug-levels time-points with baseline albumin and weight, but not with anti-TNF co-exposure. In a prospective study of a separate cohort of patients starting infliximab (n = 12), the percentage of α4ß7+ memory T cells, slightly but nonsignificantly increased throughout weeks 0, 2 to 14 (26 ± 2.3%, 27.8 ± 2.9%, 29.5 ± 2.6% respectively, P = 0.06). CONCLUSIONS: Vedolizumab/anti-TNF co-exposure did not generate new safety signals during 14-weeks induction, nor did it reduce efficacy or alter vedolizumab pharmacokinetics. These observations may aid the design of future co-biologics trials and also suggest that a deliberate waiting-interval between anti-TNF cessation and subsequent vedolizumab initiation may not be warranted.

Early drug and anti-infliximab antibody levels for prediction of primary nonresponse to infliximab therapy.

BACKGROUND: Primary nonresponse, defined as lack of clinical benefit during the induction phase, occurs in up to 30% of IBD patients treated with infliximab. The mechanisms underlying primary nonresponse have not yet been clearly defined. AIM: To evaluate the association of early (week 2 and week 6) induction infliximab and anti-infliximab antibody levels with primary nonresponse. METHODS: A retrospective observational case-control study of inflammatory bowel disease patients treated with infliximab and followed at Sheba Medical Center between 2009 and 2016 was performed. Pre-infusion infliximab and antibodies to infliximab (ATI) levels were measured by our previously described drug-tolerant ELISA assay. RESULTS: Thirty-five primary nonresponders have been identified and matched with 105 primary responders (1:3 ratios). Both week 2 and week 6 infliximab levels were significantly lower among primary nonresponders compared to responders (week 2, 6: median level 7.2, 2.2 µg/mL vs 13.5, 9.5 µg/mL, P = .0019, P < .0001 respectively). Antibodies to infliximab appeared more frequently (either week 2 or 6, 68% vs 28% prevalence, P = .0004) and at higher levels in nonresponders compared to responders (week 2, 6: median ATI 7.3, 10.8 µg/mL-eq vs 3.8, 4.4 µg/mL-eq, P = .005, P = .008 respectively). Moreover, week 2 infliximab levels <6.8 µg/mL (AUC = 0.68, P = .002, sensitivity 50%, specificity 86%) and antibodies to infliximab levels >4.3 µg/mL-eq (AUC = 0.78, P = .0004, sensitivity 77%, specificity 71%) were predictive of primary nonresponse. Among the other clinical and demographic variables, higher baseline ulcerative colitis clinical score, infliximab monotherapy, prior adalimumab therapy and previous Crohn's disease-related surgeries were also associated with an increased risk of primary nonresponse. CONCLUSIONS: Infliximab levels below 6.8 µg/mL and antibodies to infliximab levels above 4.3 µg/mL-eq before the second infusion are associated with primary nonresponse, especially among Crohn's disease patients.

Addition of an immunomodulator can reverse antibody formation and loss of response in patients treated with adalimumab.

BACKGROUND: Anti-adalimumab antibodies (AAA) are associated with loss of clinical response (LOR). Addition of an immunomodulator has been shown to reverse immunogenicity and regain response with infliximab monotherapy. Similar data on adalimumab are lacking. AIM: To study the impact of immunomodulator addition on the emergence of AAA and LOR among adalimumab therapy patients. METHODS: The databases of three tertiary medical centres were reviewed to identify patients who developed AAA during adalimumab monotherapy with resultant LOR, and received an immunomodulator as a salvage combination therapy. All sera were prospectively analysed using previously described ELISA assays. Clinical response was determined using appropriate clinical scores. Elimination of AAA, designated as 'sero-reversal', elevation of drug levels and regained clinical response were the sought outcomes. RESULTS: Twenty-three patients (21 Crohn's disease, and 2 ulcerative colitis) developed AAA with subsequent LOR and were thereafter prescribed an immunomodulator as salvage therapy (thiopurine n = 14, methotrexate n = 9). Eleven patients (48%) underwent sero-reversal with gradual elimination of AAA, increase in drug trough levels and restoration of clinical response (median time to sero-reversal 5 months). In 12 patients (52%), immunogenicity and loss of response could not be reversed. There was no difference between responders and nonresponders in the type of immunomodulators used or baseline clinical characteristics. CONCLUSIONS: In almost half of inflammatory bowel disease patients developing anti-adalimumab antibodies and loss of response, established immunogenicity of adalimumab can be gradually reversed by the addition of immunomodulator therapy with restoration of a clinico-biological response. However, these observations need to be confirmed with larger studies.

Induction infliximab levels among patients with acute severe ulcerative colitis compared with patients with moderately severe ulcerative colitis.

BACKGROUND: Infliximab is effective as salvage therapy for patients with steroid refractory acute severe ulcerative colitis (UC). Although current data suggest that the pharmacokinetics of infliximab are influenced by inflammatory burden in patients with acute severe UC, data comparing infliximab trough levels in patients with acute severe UC vs. moderately severe UC are scarce. AIM: To compare infliximab trough and anti-infliximab antibody levels at a standard fixed time-point during induction between patients with acute severe and moderately severe UC. METHODS: A multi-centre retrospective study comparing infliximab drug and antibody levels 14 days after the first infusion in hospitalised acute severe UC versus out-patients with moderately severe UC was performed. RESULTS: Sixteen acute severe UC patients, hospitalised between 2010-2015 and refractory to intravenous corticosteroids, were treated with infliximab 5 mg/kg salvage therapy. They were compared to 16 moderately severe UC out-patient controls. Mean infliximab trough levels at day 14 were significantly lower in patients with acute severe UC compared to moderately severe UC (7.15 ± 5.3 vs. 14.4 ± 11.2 µg/mL, P = 0.007). Seven patients (three acute severe and four moderate severe UC) were primary nonresponders to infliximab induction therapy. Infliximab level at day 14 did not differ between responders and nonresponders (9.8 ± 9 vs. 12.1 ± 10.6 µg/mL, respectively, P = N.S.). However, week 2 median antibody-to-infliximab levels were numerically higher among primary nonresponders (3.4 ± 5.7 vs. 1.2 ± 4 µg/mL-eq, respectively, P = 0.06). CONCLUSIONS: Infliximab trough levels at day 14 were lower in patients with acute severe UC compared to moderately severe UC, possibly due to a higher inflammatory burden and/or increased drug clearance. However, drug levels at day 14 were not lower among nonresponders compared with responders. Controlled trials are warranted to examine whether an a-priori-intensified infliximab induction protocol will lead to an improved outcome in acute severe UC.

The decline of anti-drug antibody titres after discontinuation of anti-TNFs: implications for predicting re-induction outcome in IBD.

BACKGROUND: Anti-drug antibodies can be elicited by infliximab and adalimumab, but the rate of their decay after therapy is stopped is unknown. AIM: To investigate the decline of anti-drug antibody titre after anti-TNF cessation, and to evaluate the clinical utility of anti-drug antibody measurement before anti-TNF re-induction. METHODS: Inflammatory bowel disease (IBD) patients who stopped anti-TNF therapy and had measurable anti-drug antibodies were prospectively followed up by serial blood measurements of antibodies levels. The clinical outcome of a second cohort of patients who received re-induction by infliximab or adalimumab after a drug holiday >4 months was determined vis-à-vis their anti-drug antibodies status before re-induction. RESULTS: The first cohort included 22 patients with anti-drug antibodies who were prospectively followed up after cessation of anti-TNF. Sixteen had antibodies-to-infliximab (ATI) and six had antibodies-to-adalimumab (ATA). ATI titres declined within 12 months to below detection levels in 13/16 infliximab-treated patients, whereas ATA titres became undetectable in only 2/6 adalimumab-treated patients (P = 0.04). The second cohort comprised 27 patients who resumed anti-TNFs (24 infliximab, 3 adalimumab). Of these, 3/5 patients with measurable anti-drug antibodies before re-induction experienced severe hypersensitivity reaction and/or nonresponse mandating drug-discontinuation, compared to 11/22 patients who were re-induced without measurable anti-drug antibodies (OR = 1.5, 95% CI 0.2-11, P = 0.7). CONCLUSIONS: Antibodies to infliximab titres decline to undetectable levels within one year of cessation of infliximab in the majority of patients, whereas antibodies to adalimumab seem to persist longer after adalimumab discontinuation. Measuring antibodies to infliximab prior to infliximab re-induction is probably of little clinical utility, especially if more than a 12-month drug-holiday has elapsed.

Molecular analysis of noroviruses involved in acute gastroenteritis outbreaks in military units in Israel, 1999-2004.

The study presented here was conducted to determine the genetic properties of noroviruses (NoVs) identified between 1999 and 2004 in army recruits with acute gastroenteritis. Partial sequence analysis of the RNA-dependent RNA polymerase gene revealed the presence of two major sub-genogroups, all of which were related to genogroup II of NoV. Serological analysis using recombinant antigens confirmed this observation. Local strains associated with a 1999 outbreak were closely related to GII-6 strains, while those identified later were very closely related to GII-4 strains. GII-4 strains were also associated with an outbreak in civilian nursing homes in Israel in 2002 and samples from this outbreak were included in this study for comparison. This is the first report describing the molecular properties of NoV strains associated with diarrhea-related morbidity in Israel.

An outbreak of pertussis among young Israeli soldiers.

In winter 2001, an outbreak of pertussis involving an estimated 75 people occurred among soldiers serving in an infantry regiment of the Israeli Defense Forces (IDF). Nasopharyngeal swabs were obtained from patients and contacts for culture and PCR. Serum samples were obtained and assayed by ELISA for the presence of IgA, IgM and IgG antibodies to a lysate antigen of Bordetella pertussis. The calculated attack rate was 21% based on clinical signs alone (cough lasting 30 days or longer) and 9.5% based on clinical signs with laboratory confirmation (by PCR, IgA or IgM). A high carriage rate was observed; 20% of the asymptomatic and previously symptomatic subjects were PCR-positive for B. pertussis. These findings emphasize the importance of B. pertussis as a causative agent of epidemic respiratory infections in young adults and reveal the occurrence of a significant proportion of pertussis transient carriers during an outbreak of the disease.

Prevalence of the genes for shigella enterotoxins 1 and 2 among clinical isolates of shigella in Israel.

Two enterotoxins, shigella enterotoxin 1 (SHET1) and shigella enterotoxin 2 (SHET2) have been recently characterized and are believed to play a role in the clinical manifestation of shigellosis. One hundred and twenty-one isolates of Shigella spp. of 13 different serotypes and variants and 10 isolates of enteroinvasive Escherichia coli (EIEC) isolated in Israel, were examined by polymerase chain reaction for the presence of SHET1 and SHET2 genes. SHET1 was only prevalent among isolates of S. flexneri 2a while SHET2 was found in all the serotypes that were tested except for several isolates of S. flexneri 1b that lost their virulence plasmid during storage. In addition, we found that the S. flexneri 2a vaccine strain T-32 Istrati contains the gene encoding for SHET1 but not that encoding for SHET2, suggesting that the latter is located within a large deletion occurring in the 140 Mda plasmid of this S. flexneri 2a non-invasive vaccine strain.

Retrospective analysis of the first clonal outbreak of nalidixic acid-resistant Shigella sonnei shigellosis in Israel.

Reported here is a retrospective molecular analysis of the isolates recovered from the first outbreak of nalidixic acid (NA)-resistant Shigella sonnei shigellosis to occur in Israel. The outbreak affected 94 children. In the retrospective analysis, a total of 13 NA-resistant isolates and five NA-susceptible isolates recovered during the outbreak period were examined. Restriction fragment length polymorphism profiles obtained by digestion with BamHI, PvuI, HinfI or SmaI yielded identical profiles for all 18 isolates. All NA-resistant strains had an identical plasmid profile, but this profile differed from that displayed by the susceptible strains. In all of the NA-resistant strains a 304 bp fragment in the gyrA gene coding for a region associated with NA resistance was sequenced and showed a single point mutation, Ser83-->Phe. In this outbreak, the isolates of NA-resistant Shigella sonnei belonged to a single clone and NA resistance was associated with a point mutation in the gyrA gene.

Prospective cohort studies of shigellosis during military field training.

Epidemiological and clinical features of shigellosis occurring among cohorts of Israeli recruits followed-up for 3-6 months during the summer field training of years 1993-1997 were studied. The incidence rate of culture-proven shigellosis was the highest (78 cases per 1,000 recruits) in 1996 and the lowest (13 cases per 1,000 recruits) in 1995. Shigella sonnei (152 isolates) and Shigella flexneri (151 isolates) were the most common species. Fifty percent of the patients with shigellosis had fever (>37.5 degrees C), compared to only 18% of the subjects with other diarrheal diseases (P < 0.001). The duration of illness was longer among subjects with shigellosis than among those with other diarrheal diseases (P < 0.001). Illness due to Shigella flexneri was more severe than illness caused by Shigella sonnei.

A waterborne outbreak of gastroenteritis in the Golan Heights due to enterotoxigenic Escherichia coli.

BACKGROUND: Over a period of 4 days between May 18-21, 1998, a multifocal outbreak of diarrhea, involving 175 Israel Defence Force soldiers and at least 54 civilians, occurred in the Golan Heights. PATIENTS AND METHODS: Stool samples from 40 affected soldiers were collected for microbiological testing. In addition, a rapid PCR technique was employed for the direct detection of the heat-labile (LT) and heat-stable toxin (ST) genes of enterotoxigenic Escherichia coli (ETEC) in stool samples. RESULTS: All 40 stool specimens taken from patients with diarrhea was negative by culture. However, ETEC was detected in 16 stool specimens using the rapid PCR method. The epidemiological investigation found no association between the food items consumed prior to the onset of the outbreak and the attack rate of diarrhea. A review of the water distribution system revealed that all affected military posts and civilian communities were supplied by a common water pipeline. Water sampled from various points along the distribution system showed inadequate chlorination and high concentrations of E. coli. CONCLUSION: This report suggests that the involvement of ETEC in the etiology of waterborne diarrheal outbreaks may be underestimated, probably due to the difficulties involved in the laboratory identification of this enteropathogen. Adoption of our rapid method for the identification of ETEC, which is applicable to routine diagnostic laboratories, facilitates pathogen detection within hours, and allows early intervention in cases of widespread diarrheal epidemics.

[Development of molecular tests for rapid detection of enteropathogens].

Amplification of specific DNA sequences by polymerase chain reaction (PCR), enables rapid, sensitive and direct, specific identification of pathogens at very low concentrations in clinical samples. Studies in recent years have reported identification of several enteropathogens directly from stool samples by PCR. The amplification process includes the use of primers complementary to the DNA sequences specific to the pathogen, thus relying on the pathogen's genotype, rather than its phenotype on which identification by the methods of classical microbiology were based. We have developed PCR protocols for the differential identification of enteropathogens resembling the normal flora (enterotoxigenic E. coli (ETEC), E. coli O-157), Shigella spp, and the detection of enteropathogens that can not be grown on classic growth media (Norwalk virus). The amplification process is inhibited by several substrates present in fecal material (phenol, hemoglobin), limiting DNA extraction by phenol. The protocols we have developed for direct detection of Shigella spp and ETEC in stools circumvent inhibition of PCR by the use of a 4-hour pre-enrichment step in brain-heart infusion broth. Rapid and accurate identification of enteropathogens is important for prompt and focused intervention to stop the chain of transmission in outbreaks of gastroenteritis in military and civilian populations.

Antibiotic resistance pattern of enterotoxigenic Escherichia coli isolated from infants and young adults in Israel.

The aim of this study was to describe antibiotic resistance rates of enterotoxigenic Escherichia coli in Israel in order to facilitate the empirical choice of antibiotic treatment or prophylaxis for traveler's diarrhea and infantile diarrhea in our region. A total of 281 enterotoxigenic Escherichia coli isolates were tested: 144 from Bedouin infants and 137 from Israeli soldiers. Antibiotic-resistant isolates were prevalent in both groups, but higher resistance rates were found in the pediatric group. Strains producing heat-labile toxin showed higher resistance rates than strains producing heat-stable toxin. The results obtained in Israel preclude the use of many commonly used antibiotics for the treatment of traveler's diarrhea. Quinolones, however, are still effective.

Detection of enterotoxigenic Escherichia coli in stool specimens by polymerase chain reaction.

A polymerase chain reaction (PCR) protocol for rapid (7 h) detection of enterotoxigenic Escherichia coli (ETEC) is described. This protocol has been validated on 57 stool samples from young children by comparing it with the colony hybridization technique. A good agreement was found between the two methods with Cohen's kappa statistics of 0.87 and 0.79 for the detection of the heat-stable toxin (ST) and heat-labile toxin (LT), respectively. Of 26 samples positive for LT and 15 samples positive for ST by colony hybridization, 21 (81%) and 15 (100%) were also found to be positive for LT and ST by PCR, respectively. Only one sample identified as LT-negative by colony hybridization was found to be positive by PCR. However, 3 of 42 samples of ST-negative by colony hybridization were detected as positive by PCR. A reconstruction experiment revealed that PCR could detect LT-producing and ST-producing ETEC at minimal concentrations of 2.5 x 10(3) cfu and 2.5 x 10(2) cfu per gram of feces, respectively. These data indicate the possible use of this method for rapid identification of ETEC-associated diarrhea in clinical and epidemiological settings.

Double-blind vaccine-controlled randomised efficacy trial of an investigational Shigella sonnei conjugate vaccine in young adults.

BACKGROUND: The aim of this double-blind randomised vaccine-controlled trial was to assess the efficacy of a conjugate vaccine composed of Shigella sonnei O-specific polysaccharide bound to Pseudomonas aeruginosa recombinant exoprotein A (S sonnei-rEPA) and of an oral, live-attenuated Escherichia coli/S flexneri 2a (EcSf2a-2) hybrid vaccine among military recruits in Israel at high risk of exposure to Shigella spp. We report here our preliminary findings on the efficacy of S sonnei-rEPA; we have not documented sufficient cases to assess the efficacy of EcSf2a-2. METHODS: Between April, 1993, and August, 1994, male Israeli Military recruits aged 18-22 years were asked to take part in our study. We enrolled 1446 soldiers from seven separate field sites (groups A-G). Soldiers were randomly allocated one injection of S sonnei-rEPA and four doses of oral placebo (n = 576), four oral doses of EcSf2a-2 and one injection of saline placebo (n = 580), or one injection of meningococcal tetravalent control vaccine and four doses of oral placebo (n = 290). Because there were no cases of S flexneri 2a, the EcSf2a-2 and meningococcal vaccines were the control group. We defined S sonnei shigellosis as diarrhoea with a positive faecal culture for S sonnei. Each group of soldiers was followed up for 2.5-7.0 months. The primary endpoint was protective efficacy of S sonnei-rEPA against S sonnei shigellosis. FINDINGS: Cases of culture-proven S sonnei shigellosis occurred in four groups of soldiers (groups A-D), which comprised 787 volunteers (312 received S sonnei-rEPA, 316 received EcSf2a-2, and 159 received meningococcal control vaccine). In groups A-C, cases of shigellosis occurred 70-155 days after vaccination, whereas in group D cases occurred after 1-17 days. In groups A-C, the attack rate of shigellosis was 2.2% in recipients of S sonnei-rEPA compared with 8.6% in controls (protective efficacy 74% [95% CI 28-100], p = 0.006). S sonnei-rEPA also showed significant protection against shigellosis in group D (43% [4-82], p = 0.039). Prevaccination and postvaccination ELISA measurements of antibody to S sonnei lipopolysaccharide among recipients of S sonnei-rEPA showed that the vaccinees who developed S sonnei shigellosis had significantly lower serum IgG and IgA responses to the homologous lipopolysaccharide than those who did not (p = < 0.05). INTERPRETATION: One injection of S sonnei-rEPA confers type-specific protection against S sonnei shigellosis. The high antibody concentration induced by the conjugate vaccine in volunteers who did not develop shigellosis suggests that there is an association between serum antibody titre and protection.

Encephalopathy associated with enteroinvasive Escherichia coli 0144:NM infection.

Central nervous system manifestations typically occur with Shigella gastroenteritis and also in enteric Salmonella and Campylobacter infections. To date no association between enteroinvasive Escherichia coli infection and neurologic symptoms has been described. Two children with diarrhea caused by E. coli 0144:NM had otherwise unexplained encephalopathy manifested by profound stupor in one child and by obtundation and meningismus in the other one. These cases of infection occurred in northern Israel during a period of an unusually high rate of enteric infection caused by this organism. None of the microbiologic properties studied were uniquely attributable to the encephalopathic cases. The two encephalopathic as well as all eight nonencephalopathic isolates studied possessed the 140-MDa invasive plasmid. All 10 isolates examined produced small amounts of cytotoxin by the HeLa cell assay, all were nonmotile, and all had identical antibiograms. Eight of 10 of the isolates had identical plasmid profiles, while 2 isolates (from nonencephalopathic patients) had slightly different plasmid profiles. This is the first report of encephalopathy associated with enteroinvasive E. coli.

Safety and immunogenicity of the oral E. coli K12-S. flexneri 2a vaccine (EcSf2a-2) among Israeli soldiers.

A double-blind placebo-controlled study was carried out on the safety and immunogenicity of the oral Shigella flexneri (EcSf2a-2) vaccine among Israeli soldiers. Sixty volunteers received the vaccine and 59 received placebo. Fifty-three were given the full vaccine regimen (four doses). Doses ranged between 4.1 x 10(8) and 1.1 x 10(9) c.f.u. Visits to the unit clinic for mild gastrointestinal symptoms were common after the first dose in vaccinees (13%) as compared with placebo recipients (5%), but the difference was not significant, p = 0.12. Similarly, there was no difference between the groups for either gastrointestinal or non-gastrointestinal complaints reported by questionnaire. The vaccine strain was excreted by 69% and 67% of the vaccinees one day after receiving the second and the fourth doses, respectively. As judged by antibiotic susceptibility, phage typing and restriction fragment length polymorphism (RFLP), the vaccine strain emerged as genetically stable after replication in human gut and shedding. There was neither bacteriological nor serological evidence of transmission of the vaccine from vaccinees to placebo recipients. Eighteen of 26 (69.2%) and 11 of 30 (36.7%) vaccinees had significant IgA secreting cell responses 7 and 21 days after the first dose, respectively. Significant IgA or IgG serum antibody response to S. flexneri 2a LPS was detected in 30% of the vaccinees. These results support further evaluation of EcSf2a-2 vaccine protective efficacy in field studies.

Epidemic spread of Shigella sonnei shigellosis and evidence for development of immunity among children attending day-care centers in a communal settlement (Kibbutz).

An investigation of two Shigella sonnei shigellosis outbreaks that occurred in a communal settlement indicated that the transmission of the pathogen was restricted to day-care classes and secondary infection of family members was minimal. Development of serotype-specific immunity following S. sonnei infection was observed among infected children.