'We need to share our stories': the lives of Pakistanis with intellectual disability and their guardians

INTRODUCTION

The experiences of Pakistanis with intellectual disabilities (IDs) and their family members have been underexplored empirically.

METHOD

The present study sought to address this gap by understanding the lives of five Special Olympics Pakistan athletes and their guardians through PhotoVoice.

FINDINGS

Through thematic analysis, we present the primary theme concerning Pakistan's cultural context that provides an empirical exploration of cultural beliefs about intellectual disability, cultural expectations and support received by people with intellectual disabilities and their guardians.

DISCUSSION

We discuss implications for research and practice.

Bangladesh moves from being a low-prevalence nation for HIV to one with a concentrated epidemic in injecting drug users

Bangladesh has been conducting annual serological surveillance for HIV and syphilis since 1998 among most at-risk populations including sex workers, males having sex with males, injecting drug users (IDUs) and heroin smokers. During the seventh round conducted between January and June 2006, 10,368 people were sampled and the overall HIV prevalence was 0.9%. The highest HIV rate was recorded in male IDUs from the capital city Dhaka (7%), and the rates have risen significantly over the rounds (P < 0.001). In Dhaka, most of the HIV-positive IDUs (10.5%) were localized in one neighbourhood, while in the remaining neighbourhoods 1% were positive (P < 0.001). In all other groups, HIV prevalence was <1%. Active syphilis rates were highest in female IDUs (9.9%) followed by female street-based sex workers (8.6%). However, rates in female sex workers in Dhaka declined significantly over the years (P < 0.001). Bangladesh has to act urgently to prevent escalation of the epidemic.

Zinc supplementation in the management of shigellosis in malnourished children in Bangladesh

OBJECTIVE

To assess the impact of zinc supplementation on clinical recovery, weight gain and subsequent growth and morbidity in moderately malnourished children with shigellosis.

DESIGN

A randomized, double-blind, controlled trial.

SETTING

Dhaka hospital of ICDDR,B: Centre for Health and Population Research, Dhaka, Bangladesh.

SUBJECTS

Fifty-six moderately malnourished children, aged 12-59 months with culture-proven shigellosis.

METHODS

Subjects were randomly allocated to receive zinc (20 mg/day elemental) in multivitamin syrup (intervention) or multivitamin syrup without zinc (control) in two equally divided doses daily for 2 weeks. All children received pivmecillinam in a dose of 15 mg/kg every 6 h for 5 days. After supplementation, children were followed in their respective homes every 2 weeks for 6 months.

RESULTS

Children receiving zinc recovered from acute illness significantly faster than the control children (P<0.05). The medians time (days) to recovery and disappearances of blood and mucous were significantly 50% shorter in the zinc-supplemented group compared to the control group. The mean body weight of zinc supplemented children increased significantly from 8.8 kg on admission to 9.2 kg (P<0.01) at recovery, which was not observed in the control children (from 9.3 to 9.6 kg; P=0.12). During the 6-month follow-up period, zinc-supplemented children had significantly fewer mean episodes of diarrhoea compared to the control children (2.2 vs 3.3; P=0.03).

CONCLUSION

Zinc supplementation significantly shortens the duration of acute shigellosis, promotes better weight gain during recovery and reduces diarrhoeal morbidity during the subsequent 6 months.

Safety and immunogenicity of tetravalent rhesus-based rotavirus vaccine in Bangladesh

BACKGROUND

Rotavirus is the most common cause of severe gastroenteritis among children worldwide.

OBJECTIVES

To compare the safety, immunogenicity and shedding patterns of rhesus rotavirus (RRV)-tetravalent vaccine vs. placebo among infants in rural Bangladesh.

METHODS

A double blinded, placebo-controlled trial was conducted in which infants (n = 120) were randomly assigned to receive three doses of either vaccine or placebo administered at approximately 6, 10 and 14 weeks of age together with routine immunizations. Data on possible adverse effects of vaccinations were collected daily for 7 days after each dose. Stool samples were collected after each dose, and serum samples were obtained before the first and after the third vaccination.

RESULTS

Fever (> or = 38 degrees C), as measured by study assistants, was noted more frequently among vaccinees (15%) than among placebo recipients (2%) during the 7 days after vaccination but was not reported more frequently by parents of vaccinees vs. placebo recipients. Overall 87% of vaccinees had an antibody response (measured by IgA or anti-RRV-neutralizing antibodies) after vaccination compared with 32% of placebo recipients. Rates of seroconversion were higher among subjects with lower levels of prevaccination antibodies and those who shed rotavirus after vaccination. Vaccine strain viruses were detected in stools from placebo vaccine recipients who had evidence of IgA seroconversion.

CONCLUSIONS

In this population RRV-tetravalent vaccine was comparably immunogenic and safe as in trials conducted in developed countries, where this vaccine has been proved effective in preventing severe rotavirus diarrhea. These data support continued evaluation of rotavirus vaccines in developing countries.

Immune modulation after measles vaccination of 6-9 months old Bangladeshi infants

Measles still causes high mortality in children younger than 1 year of age. Administration of high titre measles vaccines before 7 months of age led to increased overall mortality, raising questions as to the immunological effects of measles vaccine in young infants. We investigated the immune response to standard titre vaccines given to children in Bangladesh in a single dose at age 9 months, or two doses at 6 and 9 months. Of the children vaccinated at age 9 months, 95% serocoverted, compared with 70% at age 6 months. Delayed-type-hypersensitivity reactions to candida antigen were significantly reduced in both vaccine groups at 6 weeks post-vaccination, but responses to other recall antigens studied were not significantly different from controls. In both vaccine groups, peripheral blood lymphocytes isolated at 6 and 24 weeks after vaccination showed significantly higher expression of activation markers upon in vitro stimulation, and a sustained increase in IL-2 production. These findings suggest prolonged immune activation after measles vaccination at the same time as some reduction in delayed hypersensitivity responses. Further study of the clinical effects of these changes is warranted.

Immune response of Bangladeshi children with acute diarrhea who subsequently have persistent diarrhea

BACKGROUND

Because altered immune responses may be a risk factor for persistent diarrhea, various aspects of the immune response were examined to elucidate the underlying immune mechanisms that may be involved in the development of persistent diarrhea.

METHODS

Children (7-12 months of age) with watery diarrhea for 6 to 8 days from the Dhaka Hospital of the International Centre for Diarrheal Disease Research, Bangladesh (ICDDR,B), were enrolled. Children were classified as having acute diarrhea (AD) or persistent diarrhea (PD) if diarrhea resolved within 14 days or persisted for more than 14 days, respectively. Uninfected control children (n = 13), from the Nutrition Follow-Up Unit of ICDDR,B were also enrolled. Of the 123 children with diarrhea who were enrolled, 85 had AD and 38 had PD. Comparisons were performed for clinical features, nutritional status (weight for age, plasma transferrin, and serum albumin levels), and immune responses: neutrophil function; peripheral blood mononuclear cell function, delayed-type hypersensitivity (DTH) responses, plasma levels of immunoglobulins, tumor necrosis factor-alpha, and interferon-gamma. Univariate analyses were conducted to assess differences among the three groups of children and between children with AD and PD. Logistic regression was performed to determine risk factors for PD.

RESULTS

There were no differences in clinical features and nutritional status among the groups of children studied. More children in whom PD developed had a negative DTH response to tuberculin than those with AD (P = 0.021). Also, a negative DTH response to tuberculin was a significant risk factor for PD (odds ratio [OR] = 3.8, 95% confidence interval [CI] = 1.5-9.9).

CONCLUSIONS

Children with acute diarrhea with a negative DTH response to tuberculin are more likely to have development of persistent diarrhea.

Immune response of children who develop persistent diarrhea following rotavirus infection

A prospective study was conducted with Bangladeshi children with rotavirus (RV) diarrhea to assess whether nutritional and clinical parameters, RV serotypes, levels of interleukin-10 (IL-10), tumor necrosis factor alpha (TNF-alpha), and gamma interferon (IFN-gamma), and RV-specific antibody titers in plasma and stool were associated with the development of persistent diarrhea. Children with watery diarrhea for 6 to 8 days, selected from the Dhaka Hospital of the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B), were enrolled in the study and monitored until diarrhea improved. Children were classified as having acute diarrhea (AD) if diarrhea resolved within 14 days of onset and as having persistent diarrhea (PD) if diarrhea persisted for more than 14 days after onset. Uninfected, control children (n = 13) from the Nutrition Follow-Up Unit of ICDDR,B were also enrolled. Of the 149 children with diarrhea enrolled, 29 had diarrhea with RV alone, of which 19 had AD and 10 developed PD. Samples of stool and blood were collected from all children on enrollment. Stool samples were collected again from children when they developed PD. Of the 10 children who had an initial RV infection and then developed PD, only one had persistent RV infection. Plasma levels of IL-10 and TNF-alpha were higher in children with diarrhea compared to uninfected controls but were similar in children with AD and PD. Plasma IFN-gamma levels were higher in children who developed PD than in those with AD (P = 0.008) or uninfected controls (P = 0.001). In stools, the levels of TNF-alpha, the only cytokine detected, were similar in the three groups of children. RV-specific immunoglobulin G (IgG) titers in plasma were higher in uninfected children than in those with AD (P < 0.001) or PD (P = 0.024) but titers were similar in children with AD and PD. RV-specific IgA titers in plasma and stool were similar in the three groups of children. From all observed parameters, only elevated plasma IFN-gamma levels were associated with subsequent development of PD. However, a larger sample size is necessary to substantiate this observation.

Hepatitis B infection in Bangladeshi mothers and infants

In order to estimate the relative importance of perinatal transmission of hepatitis B in rural Bangladesh a cross-sectional study was carried out. Paired-serum samples of infants aged 2-8 months old, a group of new born, and their mothers were tested for hepatitis B markers using a commercial ELISA test kit. In total, 107 (32.4%) positive for HBcAg, 18 (5.4%) for HBsAg, and 4 (1.2%) for HbeAg. Of the infants, 35 (10.5%) positive for HBcAg, 1 (0.3%) for HBsAg, and none for HBeAg. Of the 18 HBsAg positive mothers, 4 (22%) were HBeAg positive. All 14 children of mothers who were HBeAg negative were negative for HBsAg. Only one out of four (25%) of children of HBeAg positive mothers were HBsAg carriers (8 months old), and in three children transmission did not occur (two 8 months, one 6 months old). This survey indicates that hepatitis B is prevalent in rural Bangladesh and that the perinatal transmission mode may be relatively low.

Antibodies to Shiga toxin in the serum of children with Shigella-associated haemolytic uraemic syndrome

Antibodies to Shiga toxin (Stx) were measured in the sera of 49 children with Shigella dysenteriae serotype 1 infection, of whom 17 had haemolytic uraemic syndrome (HUS) and 32 had no complications (uncomplicated shigellosis, UCS). Children with HUS had lower levels of total IgG and IgM and lower IgM titres to Stx than those with UCS. The number of children with neutralising antibodies was similar in the two groups. Of the children with HUS, 11 had HUS on enrolment and six developed HUS subsequent to enrolment. Antibody titres in children who subsequently developed HUS were compared with those in children with UCS to assess whether differences in antibody titres occurred before the development of HUS. IgA titres to Stx were found to be higher in children who subsequently developed HUS than in those with UCS. However, logistic regression analysis revealed that titres of Stx antibodies in the serum were not significant risk factors for the development of HUS. Thus, although the levels of Stx antibodies were different in children with HUS, and higher IgA titres to Stx were identifiable in children who subsequently developed HUS compared with those with UCS, the relevance of these findings in the development of HUS remains to be elucidated.

Astrovirus infection in association with acute, persistent and nosocomial diarrhea in Bangladesh

BACKGROUND

Diarrhea is an important public health concern in developing countries such as Bangladesh. Diarrhea in children that persists for 14 days or more occurs in 7% of patients in Bangladesh and frequently results in death. Astrovirus has been demonstrated as a cause of acute and nosocomial diarrhea and can be excreted for prolonged periods, yet its importance as a cause of diarrhea among children in a developing country like Bangladesh has not been investigated.

METHODS

We tested 629 stool specimens from patients with acute diarrhea, 153 from patients with persistent diarrhea, 175 specimens from 76 patients hospitalized for diarrhea who were sampled repeatedly to detect nosocomial infection and 428 from nonhospitalized healthy children (controls). All children enrolled in the study were <5 years of age. Astrovirus was detected by enzyme immunoassay and other enteropathogens were detected by standard techniques.

RESULTS

The detection of astrovirus increased significantly with the duration of diarrhea. Astrovirus was found in 23 (15%) specimens from patients with persistent diarrhea, 26 (4%) patients with acute diarrhea, but only 8 (2%) healthy controls. This trend remained when we limited our analysis to infants <12 months of age and to episodes in which astrovirus was the sole pathogen. Among patients with nosocomial diarrhea, 16% of postadmission specimens were positive for astrovirus when the admission specimen was negative.

CONCLUSION

The observation that astrovirus is detected more frequently with diarrhea of increasing duration suggests the need for further studies to determine whether astrovirus plays a causative role in persistent diarrhea or is a secondary agent.

Lipopolysaccharide-specific antibodies in plasma and stools of children with Shigella-associated leukemoid reaction and hemolytic-uremic syndrome

Antibody responses to the lipopolysaccharide (LPS) of shigellae were compared between children with uncomplicated and complicated Shigella dysenteriae 1 infection. One hundred fifteen children between 12 and 60 months of age with S. dysenteriae 1 infection were studied. Of these children, 42 had complications (leukemoid reaction and/or hemolytic-uremic syndrome [complicated shigellosis] and 73 had no complications (uncomplicated shigellosis). Antibodies to the LPS of S. dysenteriae 1 and Shigella flexneri Y were measured in plasma and stools, as were total immunoglobulin A (IgA) and IgG concentrations in plasma and the total IgA concentration in stool, on enrollment and 3 to 5 days later. In the plasma, the concentrations of homologous (IgG) and heterologous (IgA) LPS antibodies on enrollment were higher in children with complicated shigellosis than in those with uncomplicated shigellosis. In stool, the concentrations on enrollment were similar between the two groups of children. There was a rise in antibody concentrations in the plasma (homologous and heterologous) and stool (homologous) between the day of enrollment and 3 to 5 days later in children with uncomplicated shigellosis but not in those with complicated shigellosis. These findings suggest that systemic stimulation is more marked in children with complications, so that a subsequent rise in plasma antibody concentrations does not occur in these children. In contrast, the lack of a rise in stool antibody concentrations in children with complicated shigellosis is suggestive of a lower-level mucosal response. Because the duration of diarrhea before enrollment influenced the homologous antibody concentrations, children were further divided into three subgroups (short [3 to 5 days], medium [6 to 9 days], and long [> 9 days] diarrhea durations before enrollment). Comparisons of homologous antibody concentrations between the two groups of children following such subdivisions showed that in children with complicated shigellosis, antibody concentrations were higher in the plasma of children in the short diarrhea duration subgroup but lower in the stool children in the medium diarrhea duration subgroup. No differences in antibody concentrations were observed in children in the other diarrhea duration subgroups. Thus, complications in shigellosis are associated with an early and strong systemic stimulation without a concomitant stimulation of the mucosal antibody response.

Monoclonal antibodies to the enterotoxin of Bacteroides fragilis: production, characterization, and immunodiagnostic application

A monoclonal antibody, ICT11, specific for the toxin of enterotoxigenic Bacteroides fragilis (ETBF) neutralized the cytotoxic effect of the toxin on human colonic cell line HT-29/C1. In an evaluation using 115 diarrheal stool specimens and culture as the "gold standard," the assay showed a sensitivity of 85% and a specificity of 100%. An ICT11-based sandwich enzyme-linked immunosorbent assay showed a sensitivity of 100% and a specificity of 98% for direct detection of toxin from stool samples compared with those of culture. Thus, ICT11-based assays will be useful for screening for ETBF.

Production, characterization and immunodiagnostic application of a monoclonal antibody to Shiga toxin

A mouse monoclonal antibody (MAb ICT7) that is specific for Shiga toxin was produced. The MAb neutralises the cytotoxic effects of both purified Shiga toxin and culture extracts of Shigella dysenteriae type 1 in HeLa cells. Using MAb ICT7 and polyclonal rabbit antiserum, a sandwich ELISA was developed. This test detects Shiga toxin in both S. dysenteriae type 1 bacterial extracts and in stools of patients with S. dysenteriae type 1 infection. The ELISA also detects toxin in enterohaemorrhagic Escherichia coli (EHEC) strains positive for Shiga-like toxin I. The test could detect a minimum of 100 pg of purified Shiga toxin. Furthermore, the ELISA did not detect toxin in non-S. dysenteriae type 1 Shigella species or Shiga-like toxin II produced by EHEC strains.

Alterations in lymphocyte phenotype and function in children with shigellosis who develop complications

This study was designed to see whether alterations occur in peripheral blood mononuclear cell phenotype and function in children with Shigella dysenteriae 1 infection with complications (leukemoid reaction and/or hemolytic-uremic syndrome) and whether there are any alterations prior to the development of complications. The following groups of children (ages, 12 to 60 months) were compared: children without any infection (n = 51), children with uncomplicated shigellosis (n = 65), children admitted with complicated shigellosis (leukemoid reaction and/or hemolytic-uremic syndrome) (n = 29), and children with shigellosis who developed complications after enrollment (subsequently complicated shigellosis) (n = 12). Tests for the peripheral blood mononuclear cell phenotype (CD3, CD4, CD8, CD57 [corrected], CD20, and CD25), spontaneous proliferation, and the proliferative response to phytohemagglutinin, pokeweed mitogen, and the lipopolysaccharide of S. dysenteriae 1 were performed, as were skin tests for delayed-type hypersensitivity (DTH). Children who subsequently developed complications differed from other groups of children as follows: (i) the numbers of CD3+ and CD4+ cells were lower than in uninfected children (P < 0.05), (ii) the CD4/CD8 ratio was lower than in children with uncomplicated shigellosis (P < 0.05) and in uninfected children (P < 0.05), and (iii) the levels of spontaneous proliferation of peripheral blood mononuclear cells were higher and DTH responses were lower than those in children with uncomplicated shigellosis (P < 0.05 and P < 0.017, respectively). Children with complications differed by having (i) increased numbers of CD3- CD57- [corrected] CD20- cells (P < 0.05) compared with those in other groups of children and (ii) lower CD4/CD8 ratios (P < 0.05), higher levels of spontaneous proliferation (P < 0.05), and lower DTH responses (P = 0.005) than children with uncomplicated shigellosis. Three to five days after enrollment, the number of CD4+ cells increased in children who subsequently developed complications (P = 0.025), i.e., when they developed complications and at this time their CD4+ cell number was similar to that of other groups of children. Thus, lymphocyte phenotype and function are altered prior to the development of complications in children with shigellosis, and once complications develop, the pattern of alterations changes. Whether these alterations have a role in precipitating complications or whether they reflect early events underlying the development of complications remains to be elucidated.

Monoclonal antibodies specific for the bundle-forming pilus of enteropathogenic Escherichia coli

The bundle-forming pilus (BFP) produced by enteropathogenic Escherichia coli (EPEC) is associated with the presence of a large EPEC adherence factor plasmid and the formation of localized adherence clusters on tissue culture cells. Three mouse monoclonal antibodies (ICA2, ICA3, and ICA4) were produced against BFP purified from EPEC B171 (O111:NM). These monoclonal antibodies reacted in immunoblots with different epitopes of the 19.5-kDa bundlin subunit of BFP of heterologous EPEC. These reagents could serve as diagnostic tools for the identification of EPEC as well as for studying the role of BfpA in the interaction of EPEC with eukaryotic cells.

Comparison of the vibriocidal antibody response in cholera due to Vibrio cholerae O139 Bengal with the response in cholera due to Vibrio cholerae O1

Vibrio cholerae serogroup O139, now considered to be the second organism capable of causing epidemic severe dehydrating cholera, contains a capsular polysaccharide which makes it difficult for it to be used in the conventional vibriocidal antibody assay optimized for V. cholerae O1. After modification of the procedure, which involved the use of specific bacterial strains, a lower bacterial inoculum, and increased amounts of complement, the vibriocidal antibody responses to V. cholerae O139 were measured in acute- and convalescent-phase sera from 33 V. cholerae O139-infected and 18 V. cholerae O1-infected patients and in single serum samples from 20 healthy control subjects. The responses in these individuals to V. cholerae O1 strains were also determined. Significant elevations in the homologous antibody response were found only in the convalescent-phase sera from both groups of patients with cholera. These findings may explain the basis for the lack of heterologous protection between the two serogroups of V. cholerae. Healthy controls had higher background levels of vibriocidal antibody to V. cholerae O1 than to V. cholerae O139.

Peripheral blood neutrophil responses in children with shigellosis

Alterations in peripheral blood neutrophil function are known to occur in patients with colitis and may have a role in precipitating nonspecific tissue injury. It is not known whether neutrophil function is altered in patients with Shigella dysenteriae type 1 infection, during which there is extensive colitis and which may be associated with life-threatening complications in young children. Three aspects of peripheral blood neutrophil function, polarization, attachment to yeast particles, and locomotion, were therefore studied in 111 children with S. dysenteriae type 1 infection and 57 children without any infection. All children were aged 12 to 60 months. Of the children with S. dysenteriae type 1 infection, 42 had leukemoid reaction, hemolytic-uremic syndrome, or septicemia (complicated shigellosis), while the others did not (uncomplicated shigellosis). Polarization and locomotion in the absence of chemoattractants and in response to N-formylmethionyl-leucylphenylalanine (FMLP) and the lipopolysaccharide (LPS) of S. dysenteriae type 1 were determined. Attachment to unopsonized and opsonized yeast particles was also determined. Children with shigellosis (uncomplicated or complicated) had more polarized neutrophils with and without chemoattractants than uninfected children (P < 0.05). Children with complicated shigellosis had more polarized neutrophils with FMLP at 10(-7) and 10(-6) M (P < 0.05) and with LPS than children with uncomplicated shigellosis (P < 0.05). At 3 to 5 days after enrollment, the numbers of polarized neutrophils with 10(-8), 10(-6), and 10(-5) M FMLP declined in children with uncomplicated shigellosis but not in those with complicated shigellosis. Attachment to yeast particles was similar in all three groups of children. Locomotion was inhibited by LPS in children with shigellosis (P < 0.05), whether it was uncomplicated or complicated, compared with locomotion in uninfected children. Finally, neutrophil polarization in uninfected children was negatively influenced by nutritional status. Thus, poorly nourished uninfected children had more polarized neutrophils with FMLP at 10(-9) M (P < = 0.02) and 10(-5) M (P = 0.043) than their better-nourished counterparts. In summary, altered neutrophil responses are associated with both uncomplicated and complicated shigellosis.

Cytokines in the stools of children with complicated shigellosis

The pathogenesis of the systemic complications, leukemoid reaction and hemolytic uremic syndrome, associated with Shigella dysenteriae type 1 infection is not well understood. The excessive production of proinflammatory cytokines, including tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6), has been suggested as a possible factor. We measured IL-6 and TNF-alpha in stools of 56 children with S. dysenteriae 1 infection and 29 children without any apparent infection, all age 12 to 60 months. Sixteen children with S. dysenteriae 1 infection had leukemoid reaction or hemolytic uremic syndrome (complicated shigellosis), while the others did not (uncomplicated shigellosis). Stool IL-6 and TNF-alpha concentrations were higher in children with uncomplicated shigellosis than in children with complicated shigellosis (P = 0.009 and < 0.001, respectively) or in uninfected children (P < 0.001). It is concluded that complicated infection is not associated with higher concentrations of the proinflammatory cytokines IL-6 and TNF-alpha in stool.

Evaluation of the monoclonal antibody-based kit Bengal SMART for rapid detection of Vibrio cholerae O139 synonym Bengal in stool samples

A monoclonal antibody-based test, Bengal SMART, was developed for rapid detection of Vibrio cholerae O139 synonym Bengal directly from stool specimens. The test, which takes about 15 min to complete, was used to screen 189 diarrheal stool specimens. The results were compared with those of a monoclonal antibody-based coagglutination test (COAT) and the conventional culture methods used as the "gold standard" for detection of V. cholerae O139. The Bengal SMART test showed a sensitivity of 100% and a specificity of 97% in comparison with the gold standard. It also fared better than COAT, which had a sensitivity of 96% for rapid detection of V. cholerae O139 synonym Bengal. These results show that Bengal SMART is suitable for use in field settings for rapid diagnosis of cholera caused by V. cholerae O139.

Peripheral blood granulocytes and mononuclear cell responses in monkeys with experimental shigellosis

Changes in neutrophil response to N-formyl-methionyl-leucyl-phenylalanine (FMLP) and the phenotype of peripheral blood mononuclear cells were studied in monkeys after oral challenge with Shigellae. Monkeys were first challenged with S. dysenteriae 1 which caused shigellosis in some of the monkeys. After recovery, the monkeys were rechallenged with S. flexneri 2a. No difference in sensitivity was observed in the monkeys during shigellosis caused by either S. dysenteriae 1 or S. flexneri 2a. The optimal dose of FMLP for neutrophil polarization, a measure of early cell activation, in normal healthy monkeys was 10(-7) M when 67% of the neutrophils were polarized. Neutrophils from monkeys ill with shigellosis required higher doses of FMLP (10(-6) and 5 x 10(-7) M) for maximum polarization. As the monkeys recovered, a gradual decrease in the doses of FMLP for optimal neutrophil polarization was also observed. The percentage of CD2-positive T lymphocytes, the earliest marker for T lymphocytes in the peripheral blood, decreased when the monkeys developed shigellosis and returned to normal levels as the monkeys improved. However, there was no change in the percentage of CD20-positive peripheral blood B lymphocytes.

Development and evaluation of rapid monoclonal antibody-based coagglutination test for direct detection of Vibrio cholerae O139 synonym Bengal in stool samples

A monoclonal antibody-based coagglutination test directly detected Vibrio cholerae O139 synonym Bengal in 83 of 120 watery diarrheal stool specimens; on culture, 90 samples were positive. Thus, with 92% sensitivity, 100% specificity, and 100% positive and 95% negative predictive values, the coagglutination test is a useful rapid test for V. cholerae O139.

Diarrhea associated with Cyclospora Sp. in Bangladesh

A spherical acid-fast organism measuring approximately 10 microns in diameter (Cyclospora sp.) has recently been implicated in diarrheal diseases in many parts of the world. We detected this organism in the stools of six Bangladeshi patients with diarrhea. Four patients had chronic diarrhea and two had acute diarrhea at the time of presentation. This is the first report of infection with this organism in the indigenous population from this region.

Monoclonal antibodies specific for Shigella dysenteriae serotype 13. Production, characterization, and diagnostic application

Three mouse monoclonal antibodies (mAbs) (ICL3, ICL4, and ICL5) were produced that specifically recognized the lipopolysaccharide antigen of the newly recognized Shigella dysenteriae serotype-13 strain. All three mAbs reacted with all nine reference isolates of S. dysenteriae 13 in different tests. The mAbs also detected colonies of S. dysenteriae-13 isolates by direct slide agglutination test. The mAbs also reacted with the reference Escherichia coli 0150 strain and showed its close antigenic relationship with S. dysenteriae 13. Use of these mAbs in our clinical laboratory during an 8-month period detected three S. dysenteriae-13 isolates that were also detected by a polyclonal rabbit antiserum. It should now be possible to define the epidemiologic importance of S. dysenteriae serotype 13 in diarrhea by using these mAbs.

Production, characterization, and application of monoclonal antibodies to Vibrio cholerae O139 synonym Bengal

Mouse monoclonal antibodies (MAbs) were derived against acetone-treated whole cells of the newly recognized Vibrio cholerae O139 serogroup which is causing epidemics of cholera-like disease in India and Bangladesh. Four MAbs specifically recognized the lipopolysaccharide antigens of V. cholerae O139. MAbs ICL9 and ICL13 were of the immunoglobulin M (IgM) isotype, ICL11 was of the IgG3 isotype, and ICL12 was of the Ig2b isotype. A fifth MAb, ICL10, of the IgG2b isotype cross-reacted with V. cholerae O91. All five MAbs recognized V. cholerae O139 in an enzyme-linked immunosorbent assay, slide agglutination test, motility inhibition test, and indirect immunofluorescence test. During a 1-month evaluation of these MAbs in our clinical laboratory, all 86 cases diagnosed as V. cholerae O139 by a rabbit polyclonal antiserum were also detected by these MAbs, establishing their utility as highly sensitive and specific diagnostic reagents. With these MAbs, it should now be possible to screen for the V. cholerae O139 serogroup in epidemic and endemic diarrhea cases and in environmental and food samples.

Role of Shigella dysenteriae type 1 slime polysaccharide in resistance to serum killing and phagocytosis

Shigella dysenteriae type 1 produce a slime polysaccharide when cultivated in vivo in adult rabbit ileal loops or in vitro in casamino acid yeast extract broth medium which promotes hemagglutination of these bacteria. Seven strains of S. dysenteriae 1 grown in vitro and in vivo and possessing slime polysaccharides resisted killing by normal human serum as compared to bacteria grown under conditions which do not stimulate the production of capsular polysaccharide and did not resist serum killing (mean survival 72% for in vitro growth and 73% for in vivo growth conditions favoring capsule production vs < 2% for growth conditions which do not favor capsule production; P < 0.001 for both comparisons). Similar differences were observed when killing was assessed by phagocytosis (62-78% vs < 2%; P < 0.001). We conclude that capsular polysaccharide may be an additional virulence factor of S. dysenteriae 1.

A monoclonal antibody to Shigella dysenteriae serotype 13 cross-reacting with Shiga toxin

A monoclonal antibody (mAb ICT6) was produced against the newly described Shigella dysenteriae serotype type 13. The mAb was of IgM isotype and recognized purified Shiga toxin in ELISA and immunoblot. It also recognized periplasmic extract S. dysenteriae type 13 in immunoblot as did an affinity-purified polyclonal rabbit antiserum and a previously described monoclonal antibody to the B subunit of Shiga toxin. The mAb ICT6 did not neutralize the cytotoxic effects or S. dysenteriae type 13, Shiga toxin or periplasmic extracts of S. dysenteriae type 1 for HeLa cells.

Lymphocytes in the intestine: role and distribution

Once a pathogen penetrates the surface epithelium, the process of immune activation begins. The pathogen is transported across the intestinal epithelium by M cells and presented to the underlying lymphocytes in Peyer's patches by MHCII positive enterocytes. At the same time, intraepithelial lymphocytes are activated and secrete interferon tau which increases the ability of enterocytes to present antigen. Simultaneously, intraepithelial lymphocytes may also cytolyse pathogens. In Peyer's patches, T-lymphocytes in parafollicular areas interact with antigen presenting cells and antigenic peptides to become activated. B-lymphocytes in follicular areas are also initially activated by the interaction of antigen and their surface Ig. B-lymphocyte activation is enhanced by helper T-lymphocytes so that B-lymphocytes begin to proliferate in germinal centres. Most B-lymphocytes at this stage are surface IgA positive whether induced by T-switch cells or by isotype specific T-lymphocytes. At the same time activated T-suppressor cells and contrasuppressors regulate the immune response to maintain it at an optim level. All these lymphocytes then leave Peyer's patches via blood vessels to mesenteric lymph nodes and the spleen where further cellular activation occurs. Thereafter, activated lymphocytes return to the intestine either directly or via the peripheral circulation. Those that reach the intestine directly, differentiate into effector cells and enter the lamina propria. In the lamina propria, plasma cells and cytotoxic T-lymphocytes destroy pathogens by secreting specific Ig and by cytotoxicity respectively. Activated helper T-lymphocytes in the lamina propria probably help in local responses by acting on the few resting B-lymphocytes present there. T-suppressor lymphocytes enter the epithelium to become intraepithelial lymphocytes and regulate responses by suppressor and contrasuppressor activities. Intraepithelial lymphocytes are also cytotoxic for luminal pathogens. Activated lymphocytes which do not return to the intestine directly enter the thoracic duct and thereby the general circulation. In this way a local gut response is converted into a systemic one and memory lymphocytes are disseminated throughout the body. In addition, suppressor and contrasuppressor T-lymphocytes also become available for peripheral effects. Large number of these lymphocytes remain in circulation, while others return to the intestine to provide local protection. A schematic representation of thetraffic of lymphocytes is shown in Fig. 3.

Immortalization of Epstein-Barr virus-infected CD23-negative B lymphocytes by the addition of B cell growth factor

Epstein-Barr (EB) virus-immortalized B lymphocytes coexpress the EB viral latent gene products (EB viral nuclear antigens 1 to 6, the latent membrane protein and the terminal protein gene products) and the cellular activation antigen CD23. Immortalized B cells can be separated from those which are infected but not immortalized on the basis of CD23 expression as early as 2 days after in vitro infection. In the present report we have confirmed these data, but show that if left in culture for 7 days after infection before separation the CD23-negative cells show a donor-related ability to become CD23-positive and immortalize. CD23-negative cells separated 2 days after infection can be induced to immortalize by the addition of low Mr B cell growth factor but not by the addition of recombinant interleukin 1, 4 or soluble CD23. At 2 to 3 days after infection the EB viral nuclear antigens 1, 2 and the high Mr species 3, 4 and 6, as well as the latent membrane protein can be detected in the CD23-positive fraction. In contrast at this time only nuclear antigens 1 and 2 could be detected in the CD23-negative fraction. This difference in gene expression may account for the inability of the CD23-negative fraction to immortalize. In the light of these observations the mechanism of viral persistence in vivo is discussed.

Lymphocytes activated by the Epstein-Barr virus to produce immunoglobulin do not express CD23 or become immortalized

Epstein-Barr virus causes polyclonal activation and immortalization of a small percentage of peripheral blood B lymphocytes after in vitro infection. However, the susceptible B lymphocytes have not been identified. We have used the B lymphocyte activation antigen, CD23, as a marker for separating immortalized and non-immortalized Epstein-Barr virus-infected B lymphocytes and have identified the polyclonally-activated cells, using double staining for cytoplasmic immunoglobulin and viral antigens. The vast majority of cells expressing cytoplasmic immunoglobulin are negative for CD23 and for Epstein-Barr virus nuclear antigen, and are non-immortalized. Conversely, the CD23-positive, immortalized population are positive for Epstein-Barr virus nuclear antigen and negative for cytoplasmic immunoglobulin. These results define a diversity in the response of B lymphocytes to Epstein-Barr virus infection and suggest separate pathways for terminal differentiation and immortalization. This diversity may be important in determining the outcome of Epstein-Barr virus infection in humans.

Production and characterisation of a human monoclonal antibody to cytomegalovirus and its use in an early nuclear fluorescence assay

A human monoclonal antibody to cytomegalovirus (CMV) was produced by transforming peripheral blood mononuclear cells of a patient with recent CMV infection. It is directed against a late antigen located in the nucleus of CMV infected fibroblasts at 24-72 hours postinfection and immuneprecipitates 65K and 48K proteins from 35S-labelled CMV infected cells. Results of its use in an early nuclear fluorescence assay for rapid diagnosis are presented.

Immunohistological studies of lymphoproliferative lesions in a fatal case of Epstein-Barr virus infection

A fatal case of infectious mononucleosis occurred in a young adult. Abnormal serological features were noted in his mother, although there was no other family history suggesting an inherited defect of immune response to Epstein-Barr virus (EBV). The cellular infiltrate observed in tissues obtained at necropsy was analysed with a range of specific monoclonal and polyclonal antibodies. Polyclonal plasmacytoid B cell proliferation had occurred in many tissues. These cells were positive for EBV nuclear antigen, but viral particles were not seen on ultrastructural examination, and the virus was not isolated, suggesting a non-permissive infection.

Colcemid inhibits growth during early G1 in normal but not in tumorigenic lymphocytes

Mitogenically stimulated human and mouse lymphocytes enter the cell cycle (G0, G1A, G1B, S, G2+M) via a newly recognized subphase, G1'. This subphase precedes G1A and is distinct from G0. The G1' subphase is absent in immortalized and tumorigenic lymphoblastoid cell lines (LCLs) by cytofluorimetric criteria. Furthermore, colcemid inhibits transition through the G0/G1' as well as G2 phases in mitogen-stimulated lymphocytes and in LCLs. Tumorigenic LCLs are not sensitive to growth inhibition by colcemid during early G1. These observations suggest that a progressive series of changes have occurred during G0/G1' which lead to deregulation of growth control.