Atiqur Rahman

Antigen-Specific Memory B-Cell Responses to Vibrio cholerae O1 Infection in Bangladesh

ABSTRACT Cholera, caused by Vibrio cholerae, is a noninvasive dehydrating enteric disease with a high mortality rate if untreated. Infection with V. cholerae elicits long-term protection against subsequent disease in countries where the disease is endemic. Although the mechanism of this protective immunity is unknown, it has been hypothesized that a protective mucosal response to V. cholerae infection may be mediated by anamnestic responses of memory B cells in the gut-associated lymphoid tissue. To characterize memory B-cell responses to cholera, we enrolled a cohort of 39 hospitalized patients with culture-confirmed cholera and evaluated their immunologic responses at frequent intervals over the subsequent 1 year. Memory B cells to cholera antigens, including lipopolysaccharide (LPS), and the protein antigens cholera toxin B subunit (CTB) and toxin-coregulated pilus major subunit A (TcpA) were enumerated using a method of polyclonal stimulation of peripheral blood mononuclear cells followed by a standard enzyme-linked immunospot procedure. All patients demonstrated CTB, TcpA, and LPS-specific immunoglobulin G (IgG)and IgA memory responses by day 90. In addition, these memory B-cell responses persisted up to 1 year, substantially longer than other traditional immunologic markers of infection with V. cholerae. While the magnitude of the LPS-specific IgG memory B-cell response waned at 1 year, CTB- and TcpA-specific IgG memory B cells remained significantly elevated at 1 year after infection, suggesting that T-cell help may result in a more durable memory B-cell response to V. cholerae protein antigens. Such memory B cells could mediate anamnestic responses on reexposure to V. cholerae.

Chronic Arsenic Poisoning and Respiratory Effects in Bangladesh

Chronic Arsenic Poisoning and Respiratory Effects in Bangladesh: Abul Hasnat Milton, et al. Arsenic Cell, NGO Forum for Drinking Water Supply & Sanitation, Bangladesh—A large population in Bangladesh have been exposed to naturally occurring inorganic arsenic through their drinking water. A prevalence comparison study of respiratory disorders among subjects with and without arsenic exposure through drinking water was conducted in Bangladesh. Characteristic skin lesions, keratoses and pigmentation alteration, and the water arsenic level confirmed the arsenic exposure. Three villages were selected from health awareness campaign programs. Participants in these courtyard meetings who had suspected skin lesions, i.e., keratosis, hyperpigmentation and hypopigmentation, were examined by a well‐trained medical officer to confirm the diagnosis. Unexposed subjects were randomly selected from another village, where tubewells were not contaminated with arsenic. We interviewed and examined 218 individuals irrespective of age and sex from these villages. The arsenic level in their drinking water was measured and the mean arsenic level was 614μ/l(ranging from 136μg/l to 1,000μg/l). Information regarding respiratory system signs and symptoms was also collected. There were few smokers, and analyses were therefore confined to nonsmokers. The overall crude prevalence (or risk) among the exposed subjects for chronic cough, and chronic bronchitis, was three times the prevalence in the control population. Age was a slightly negative confounding factor. The crude prevalence ratios were noticeably increased for female participants compared to male participants. A possible explanation for this noticeably increased occurrence of respiratory signs and symptoms in women is related to the presence of weakness. These results add to the evidence that long‐term ingestion of arsenic can cause respiratory problems especially among females.

Natural Selection in a Bangladeshi Population from the Cholera-Endemic Ganges River Delta

Natural selection in a Bangladeshi population from the cholera-endemic Ganges River Delta has targeted genes associated with cholera resistance and an innate immunity pathway activated by Vibrio cholerae. Modern Lessons from an Ancient Disease A history of natural selection favoring resistance to an infectious disease should drive the emergence of underlying genetic variants that can be readily detected. In a new study, Karlsson et al. show this for cholera, an ancient, often fatal disease that likely exerted selection pressure on Bangladeshi populations living in the Ganges River Delta where cholera is endemic. The authors combine a selection scan with an association study of cholera susceptibility, and translate the resulting genetic discoveries into clinically relevant biology. They performed whole-genome scans of Bangladeshi families to identify 305 genomic regions of selection. These regions are highly enriched for potassium channel genes and genes in the NF-κB pathway, a master regulator of inflammation and immunity that is also involved in protecting the lining of the gut. They show, by comparing cholera-affected and healthy individuals, that top selected genes correlate with cholera susceptibility. These genes regulate an innate immune signaling pathway that is activated by Vibrio cholerae, the pathogen that causes cholera, and is repeatedly targeted by selection. This combined selection and association approach identifies genes not previously implicated in the cholera host response and highlights the role of innate immunity and intestinal homeostasis in disease pathogenesis. This approach of leveraging ancient history in genetic studies is applicable to many other ancient infectious diseases still circulating in the population today. As an ancient disease with high fatality, cholera has likely exerted strong selective pressure on affected human populations. We performed a genome-wide study of natural selection in a population from the Ganges River Delta, the historic geographic epicenter of cholera. We identified 305 candidate selected regions using the composite of multiple signals (CMS) method. The regions were enriched for potassium channel genes involved in cyclic adenosine monophosphate–mediated chloride secretion and for components of the innate immune system involved in nuclear factor κB (NF-κB) signaling. We demonstrate that a number of these strongly selected genes are associated with cholera susceptibility in two separate cohorts. We further identify repeated examples of selection and association in an NF-κB/inflammasome–dependent pathway that is activated in vitro by Vibrio cholerae. Our findings shed light on the genetic basis of cholera resistance in a population from the Ganges River Delta and present a promising approach for identifying genetic factors influencing susceptibility to infectious diseases.

Antibody-Secreting Cell Responses after Vibrio cholerae O1 Infection and Oral Cholera Vaccination in Adults in Bangladesh

ABSTRACT Infection with Vibrio cholerae and oral cholera vaccines (OCVs) induce transient circulating plasmablast responses that peak within approximately 7 days after infection or vaccination. We previously demonstrated that plasmablast responses strongly correlate with subsequent levels of V. cholerae-specific duodenal antibodies up to 6 months after V. cholerae infection. Hence, plasmablast responses provide an early window into the immunologic memory at the mucosal surface. In this study, we characterized plasmablast responses following V. cholerae infection using a flow cytometrically defined population and compared V. cholerae-specific responses in adult patients with V. cholerae O1 infection and vaccinees who received the OCV Dukoral (Crucell Vaccines Canada). Among flow cytometrically sorted populations of gut-homing plasmablasts, almost 50% of the cells recognized either cholera toxin B subunit (CtxB) or V. cholerae O1 lipopolysaccharide (LPS). Using a traditional enzyme-linked immunosorbent spot assay (ELISPOT), we found that infection with V. cholerae O1 and OCVs induce similar responses to the protein antigen CtxB, but responses to LPS were diminished after OCV compared to those after natural V. cholerae infection. A second dose of OCV on day 14 failed to boost circulating V. cholerae-specific plasmablast responses in Bangladeshi adults. Our results differ from those in studies from areas where cholera is not endemic, in which a second vaccination on day 14 significantly boosts plasmablast responses. Given these results, it is likely that the optimal boosting strategies for OCVs differ significantly between areas where V. cholerae infection is endemic and those where it is not.

Comparative Proteomic Analysis Reveals Activation of Mucosal Innate Immune Signaling Pathways during Cholera

ABSTRACT Vibrio cholerae O1 is a major cause of acute watery diarrhea in over 50 countries. Evidence suggests that V. cholerae O1 may activate inflammatory pathways, and a recent study of a Bangladeshi population showed that variants in innate immune genes play a role in mediating susceptibility to cholera. We analyzed human proteins present in the small intestine of patients infected with V. cholerae O1 to characterize the host response to this pathogen. We collected duodenal biopsy specimens from patients with acute cholera after stabilization and again 30 days after initial presentation. Peptides extracted from biopsy specimens were sequenced and quantified using label-free mass spectrometry and SEQUEST. Twenty-seven host proteins were differentially abundant between the acute and convalescent stages of infection; the majority of these have known roles in innate defense, cytokine production, and apoptosis. Immunostaining confirmed that two proteins, WARS and S100A8, were more abundant in lamina propria cells during the acute stage of cholera. Analysis of the differentially abundant proteins revealed the activation of key regulators of inflammation by the innate immune system, including Toll-like receptor 4, nuclear factor kappa-light-chain-enhancer of activated B cells, mitogen-activated protein kinases, and caspase-dependent inflammasomes. Interleukin-12β (IL-12β) was a regulator of several proteins that were activated during cholera, and we confirmed that IL-12β was produced by lymphocytes recovered from duodenal biopsy specimens of cholera patients. Our study shows that a broad inflammatory response is generated in the gut early after onset of cholera, which may be critical in the development of long-term mucosal immunity against V. cholerae O1.

Immune responses to O-specific polysaccharide and lipopolysaccharide of Vibrio cholerae O1 Ogawa in adult Bangladeshi recipients of an oral killed cholera vaccine and comparison to responses in patients with cholera.

Protective immunity to cholera is serogroup specific, and serogrouping is defined by the O-specific polysaccharide (OSP) of lipopolysaccharide (LPS). We characterized OSP-specific immune responses in adult recipients of an oral killed cholera vaccine (OCV WC-rBS) and compared these with responses in patients with cholera caused by Vibrio cholerae O1 Ogawa. Although vaccinees developed plasma immunoglobulin G (IgG), IgM, IgA antibody and antibody secreting cell (ASC, marker of mucosal response) to Ogawa OSP and LPS 7 days after vaccination, responses were significantly lower than that which occurred after cholera. Similarly, patients recovering from cholera had detectable IgA, IgM, and IgG memory B cell (MBC) responses against OSP and LPS on Day 30 and Day 90, whereas vaccinees only developed IgG responses to OSP 30 days after the second immunization. The markedly lower ASC and MBC responses to OSP and LPS observed among vaccinees might explain, in part, the lower protection of an OCV compared with natural infection.

Single-Cell Analysis of the Plasmablast Response to Vibrio cholerae Demonstrates Expansion of Cross-Reactive Memory B Cells

ABSTRACT We characterized the acute B cell response in adults with cholera by analyzing the repertoire, specificity, and functional characteristics of 138 monoclonal antibodies (MAbs) generated from single-cell-sorted plasmablasts. We found that the cholera-induced responses were characterized by high levels of somatic hypermutation and large clonal expansions. A majority of the expansions targeted cholera toxin (CT) or lipopolysaccharide (LPS). Using a novel proteomics approach, we were able to identify sialidase as another major antigen targeted by the antibody response to Vibrio cholerae infection. Antitoxin MAbs targeted both the A and B subunits, and most were also potent neutralizers of enterotoxigenic Escherichia coli heat-labile toxin. LPS-specific MAbs uniformly targeted the O-specific polysaccharide, with no detectable responses to either the core or the lipid moiety of LPS. Interestingly, the LPS-specific antibodies varied widely in serotype specificity and functional characteristics. One participant infected with the Ogawa serotype produced highly mutated LPS-specific antibodies that preferentially bound the previously circulating Inaba serotype. This demonstrates durable memory against a polysaccharide antigen presented at the mucosal surface and provides a mechanism for the long-term, partial heterotypic immunity seen following cholera. IMPORTANCE Cholera is a diarrheal disease that results in significant mortality. While oral cholera vaccines are beneficial, they do not achieve equivalent protection compared to infection with Vibrio cholerae. Although antibodies likely mediate protection, the mechanisms of immunity following cholera are poorly understood, and a detailed understanding of antibody responses to cholera is of significance for human health. In this study, we characterized the human response to cholera at the single-plasmablast, monoclonal antibody level. Although this approach has not been widely applied to the study of human bacterial infection, we were able to uncover the basis of cross-reactivity between different V. cholerae serotypes and the likely impact of prior enterotoxigenic Escherichia coli exposure on the response to cholera, as well as identify novel antigenic targets. In addition to improving our understanding of the repertoire and function of the antibody response to cholera in humans, this study has implications for future cholera vaccination efforts. Cholera is a diarrheal disease that results in significant mortality. While oral cholera vaccines are beneficial, they do not achieve equivalent protection compared to infection with Vibrio cholerae. Although antibodies likely mediate protection, the mechanisms of immunity following cholera are poorly understood, and a detailed understanding of antibody responses to cholera is of significance for human health. In this study, we characterized the human response to cholera at the single-plasmablast, monoclonal antibody level. Although this approach has not been widely applied to the study of human bacterial infection, we were able to uncover the basis of cross-reactivity between different V. cholerae serotypes and the likely impact of prior enterotoxigenic Escherichia coli exposure on the response to cholera, as well as identify novel antigenic targets. In addition to improving our understanding of the repertoire and function of the antibody response to cholera in humans, this study has implications for future cholera vaccination efforts.

Design and implementation of microprocessor based electronic voting system

In this paper, we described the design and hardware implementation of an electronic voting machine. The main aim of this project is not to design a power efficient perfect device but is to design a mother device that can be adoptable to any recent technologies. The design of the machine and its usage is as simple as an illiterate common people can easily use it. A vote casting procedure is also proposed to use the machine where we prescribed a new procedure called DEMO vote casting which is a testing mechanism to test the device before vote casting and also at the run time. The vote casting system is almost similar to traditional system, only ballot box will be replaced by the device. The machine uses voter ID to identify a valid voter and restrict multiple vote casting.

A novel approach to design a reversible shifter circuit using DNA

Traditional silicon computers are believed to consume more power compared to computing systems based on Deoxyribonucleic Acid (DNA). In addition, DNA-based logic gates are stable, reusable and also outperform the non-DNA based existing shifters. In this paper, a new approach for designing DNA-based reversible shifter circuit is proposed where any kind of shifting operations can be carried out. The proposed DNA-based reversible shifter circuit is comparatively faster due to parallelism and replication properties of DNA strands. It also requires less space because of the compactness of DNA strands.

Birth Practices Among the Rural Women: Facts & Reasons

Background: Pregnancy and childbirth related complications are the leading causes of maternal mortality and morbidity in Bangladesh. An estimate shows that about 28,000 mothers die in each year in Bangladesh due to obstetric complications. The aim of this study was to find out the birth practice among rural women in Bangladesh. Material and Methods: This descriptive cross sectional study was carried out among 1220 respondents by purposive sampling technique from 2 nd to 4 th January, 2017 in different villages of Dhamrai Upazila, Dhaka. Data were collected by a structured questionnaire duly pretested through face to face interview. Data were analyzed manually and by using computer. Results: Then study revealed that majority of the respondents 80% were Muslims by religion and about 26% respondents were found within the age 25-29 years with mean age 31±7.59 years. Most of them 86% were literate and only 14% were found illiterate. Among the respondents 75% were Housewives and 11%, 9%, 1% and 4% were involved in Service, Business, Agriculture and others occupation respectively. Moreover, 78% respondents monthly income were less than TK 3000. About 43% & 16% respondents were found to have 2 & 3 children respectively. In this study, about 73% received antenatal visit and among them 57% received 1 to 3 antenatal visits and 74% received TT immunizations. It was found that 69%, 54% and 59% received antenatal advices on healthy diet, personal hygiene, drug use respectively. Home delivery and Hospital delivery practice were found among 44% & 56% respondents respectively. The reasons for home delivery like Feeling comfortable, Family decision and Financial problem were found in 60%, 26% & 42% respondents respectively. The most common complications during last delivery were obstructed labor, found among 39% respondents. Conclusion: Still now women prefer home delivery. Major reasons for home delivery were Feeling comfortable, Family decisions and Financial problems. Delivery conduction by qualified doctors were found only among 47% women. Efforts needed to increase maternal health related knowledge and awareness towards birth practice to facilitate decision in minimizing complications and mortality. Anwer Khan Modern Medical College Journal Vol. 9, No. 1: Jan 2018, P 5-9