Exploring the role of environmental enteropathy in malnutrition, infant development and oral vaccine response

Factors associated with stunting in under-five children with environmental enteropathy in slum areas of Jimma town, Ethiopia

Introduction

Stunting is a major public health issue with a significant influence on the health and development of children in low-income countries, where it affects up to 32% of children. Nutritional intake is impacted by alterations in intestinal permeability and underlying chronic inflammation, which hinder children's normal linear growth. Environmental enteropathy is a poorly understood condition with chronic intestinal inflammation. The purpose of this study was to identify the magnitude of stunting, change in growth, and factors associated with stunting and change in height for the age Z-score of children with an elevated lactulose-to-mannitol ratio.

Methods

An observational follow-up study was conducted to follow children with an elevated lactulose-to-mannitol ratio for changes in their linear growth. A lactulose-mannitol test was performed to identify children with elevated lactulose-to-mannitol ratios, indicative of environmental enteropathy. After a 1-year follow-up, anthropometry was repeated to assess their linear growth. A multivariable logistic regression analysis was performed to identify the independent predictors for stunting in children with elevated lactulose-to-mannitol ratios. All tests were two-sided, and a p-value of <0.05 was considered significant.

Results

The prevalence of stunting in children with an elevated L:M at baseline and end line was found to be 72.4% (95% CI: 60.3, 84.5) and 78.4% (95% CI: 66.7, 90.2), respectively. In a multivariate analysis, a low dietary diversity score (<4 food groups), presence of flies and insects in the toilet area, poor handwashing practices during a critical time, and MUAC z < -2 were significantly associated with stunting. Flies and insects in the toilet area and unsafe disposal of feces were significantly associated with changes in HAZ in children with elevated lactulose-to-mannitol ratios, an indicator of environmental enteropathy.

Conclusion

Most of the children with an elevated lactulose-to-mannitol ratio in the study population were stunted, and no significant change in their linear growth was observed after 1-year follow-up. Therefore, further investigation and urgent intervention are needed to prevent environmental enteropathy and stunting among under-five children in this community who are exposed to very poor sanitary conditions and other risk factors for malnutrition.

Environmental enteropathy and its association with water sanitation and hygiene in slum areas of Jimma Town Ethiopia

BACKGROUND

Environmental Enteropathy is an inflammatory condition of the gut that leads to intestinal barrier dysfunction. It is a common problem in resource-limited countries and results from exposure to larger quantities of fecal bacteria to poor personal hygiene and environmental sanitation. Due to poor intestinal permeability, there is a problem with absorption of nutrients, which in turn leads to growth faltering, poor cognitive development, and oral-vaccine failure. The aim of this study was to identify the children with an elevated lactulose to mannitol ratio (indicative of possible environmental enteropathy) and its association with water sanitation and hygiene in slum areas of Jimma Town so as to mitigate the problem of malnutrition in under-five children.

METHODS

A community-based cross-sectional study was carried out from January to April 2021. A Lactulose mannitol test was performed to determine the prevalence of elevated lactulose to mannitol ratio (possibly environmental enteropathy) in children aged 12 to 59 months. A pretested questionnaire was used to collect data on water sanitation and hygiene (WASH) indicators and sociodemographic characteristics. A multivariable logistic regression analysis was used to isolate independent predictors for possible environmental enteropathy. All tests were two-sided and statistical significance was declared at P<0.05.

RESULTS

The results of this study showed that 19.3% (95%CI: 14.8-23.7) of children had an increased lactulose to mannitol ratio (>0.15). On multivariable logistic regression analysis, the variables drinking water from unimproved water sources (AOR 3.741; 95%CI: 0.914-15.310,p = 0.048), unsafe coverage of water storage (AOR 0.363; 95%CI: 0.169-0.777, P = 0.009), public latrine utilization (AOR 0.139 95%CI: 0.024-0.816, P = 0.029),and hand washing less than 3 critical time of hand washing practices (AOR 4.369;95%CI: 1.411-13.524,P = 0.011) were significantly associated with an increased in lactulose mannitol ratio (possible indicative of intestinal permeability/environmental enteropathy).

CONCLUSION

This study showed that one fifth of under-five children in Jimma Town had an elevated lactulose to mannitol ratio (possibly environmental enteropathy). The WASH sectors and other governmental organizations should give emphasis to areas with poor water sanitation and hygiene to mitigate the problem of environmental enteropathy and related consequences like growth faltering, poor cognitive development, and oral-vaccine failure in the study area.

Essential Fatty Acid Deficiency Associates with Growth Faltering and Environmental Enteric Dysfunction in Children

Environmental enteric dysfunction (EED) is characterized by intestinal inflammation, malabsorption and growth-faltering in children with heightened exposure to gut pathogens. The aim of this study was to characterize serum non-esterified fatty acids (NEFA), in association with childhood undernutrition and EED, as potential biomarkers to predict growth outcomes. The study comprised a cohort of undernourished rural Pakistani infants (n = 365) and age-matched controls followed prospectively up to 24 months of age. Serum NEFA were quantified at ages 3–6 and 9 months and correlated with growth outcomes, serum bile acids and EED histopathological biomarkers. Serum NEFA correlated with linear growth-faltering and systemic and gut biomarkers of EED. Undernourished children exhibited essential fatty acid deficiency (EFAD), with low levels of linoleic acid and total n-6 polyunsaturated fatty acids, compensated by increased levels of oleic acid and increased elongase and desaturase activities. EFAD correlated with reduced anthropometric Z scores at 3–6 and 9 months of age. Serum NEFA also correlated with elevated BA and liver dysfunction. Essential fatty acid depletion and altered NEFA metabolism were highly prevalent and associated with acute and chronic growth-faltering in EED. The finding suggests that targeting early interventions to correct EFAD and promote FA absorption in children with EED may facilitate childhood growth in high-risk settings.

The prevalence of intestinal parasites, undernutrition and their associated risk factors among school-age children in Sekota Town, Northeast Ethiopia: A community-based cross-sectional study

Background and Aims

In developing countries, intestinal parasitic infections and malnutrition are among the most serious health issues affecting school-aged children. They have synergetic consequences. This study aimed to determine the prevalence of intestinal parasites, undernutrition, and their associated risk factors among school-age children.

Methods

A community-based cross-sectional study was conducted from April to June 2021 among school-age children in Sekota Town, Northeast Ethiopia. Households were selected using a systematic random sampling technique. Risk factor variables were collected using pretested questionnaires. Stool samples were collected from study participants and examined using a wet mount, formol-ether concentration, and modified acid-fast techniques. The height and weight of children were also measured using a meter and a standard calibrated balance, respectively. Data were analyzed using SPSS version 26.0 statistical software.

Results

The overall prevalence of intestinal parasites among school-age children was 44.3% (178/402). About seven species of intestinal parasites were identified. The predominant parasite identified was E. histolytica/dispar (11.2%), followed by H. nana (9.2%) and G. lamblia (6.7%). The well as a source of drinking water (adjusted odds ratio [AOR] = 7.93; 95% confidence interval [CI]: 4.38-14.36), habit of open-field defecation (AOR = 7.02; 95% CI: 13.05-12.06), and being undernourished (AOR = 5.67; 95% CI: 2.98-10.79) were independent predictors of intestinal parasitic infections. On the other hand, the overall prevalence of undernutrition was 46.3%. Undernutrition was significantly more likely in children with a dietary diversity score (DDS) of 3 (AOR = 3.73, 95% CI: 2.37-5.88), meal frequency of no more than three times per day (AOR = 2.00, 95% CI: 1.71-2.98), intestinal parasite infection (AOR = 5.25, 95% CI: 3.24-8.52), and no access to school-based feeding (AOR = 3.52, 95% CI: 2.17-7.96).

Conclusion

The prevalence of intestinal parasitic infections and undernutrition was high among school-age children in Sekota Town. The results imply the need for strengthening integrated strategies for the reduction of intestinal parasitic infections and undernutrition.

Ready-to-Use Therapeutic Foods Fail to Improve Vitamin A and Iron Status Meaningfully during Treatment for Severe Acute Malnutrition in 6-59-Month-old Cambodian Children

Severe acute malnutrition (SAM) remains a global health concern. Studies on the impact of ready-to-use therapeutic foods (RUTFs) on micronutrient status during SAM treatment are almost nonexistent. The objective was to investigate the impact of RUTFs on the iron and vitamin A status of 6-59-month-old children receiving SAM treatment. Biomarkers of vitamin A status (retinol-binding protein, RBP), iron status (ferritin and soluble transferrin receptor, sTfR), and inflammation (C-reactive protein, CRP, and alpha-1 acid glycoprotein, AGP) were collected at admission and discharge (week 8) during an RUTF effectiveness trial. Vitamin A deficiency was defined as RBP <0.70 µmol/L, low body iron as body iron (BI) <0 mg/kg and deficient iron stores as ferritin <12 µg/L. Data were available for 110 and 75 children at admission and discharge, respectively. There was no significant difference in haemoglobin, ferritin, sTfR, BI or RBP concentrations between admission and discharge. At discharge, BI was 0.2 mg/kg lower, and there was a tendency towards a slightly lower RBP concentration, but the prevalence of vitamin A deficiency was low at admission and discharge (6% and 3%, respectively). The small impact of both RUTFs on improving vitamin A and iron status during SAM treatment calls for further research on the bioavailability of micronutrients to enhance the effectiveness of SAM treatment on micronutrient status.

Infant Nutrition in Low- and Middle-Income Countries

The burden of infant malnutrition is greatest in low- and middle-income countries (LMICs). Infant malnutrition is defined based on distinct subcategories, among them stunting (low-height-for-age) and wasting (low-weight-for-height). Some experts are shifting more toward understanding the interplay between these overlapping phenotypes and other confounding factors such as maternal nutrition and environmental hygiene. Current guidelines emphasize appropriate breastfeeding and nutrition within the 1000 days from conception to a child's second birthday to optimize early development. Future research directed toward better biomarkers of malnutrition before acute clinical symptoms develop will help direct targeted efforts toward at-risk populations.

Astrocytes and Microglia in Stress-Induced Neuroinflammation: The African Perspective

Background: Africa is laden with a youthful population, vast mineral resources and rich fauna. However, decades of unfortunate historical, sociocultural and leadership challenges make the continent a hotspot for poverty, indoor and outdoor pollutants with attendant stress factors such as violence, malnutrition, infectious outbreaks and psychological perturbations. The burden of these stressors initiate neuroinflammatory responses but the pattern and mechanisms of glial activation in these scenarios are yet to be properly elucidated. Africa is therefore most vulnerable to neurological stressors when placed against a backdrop of demographics that favor explosive childbearing, a vast population of unemployed youths making up a projected 42% of global youth population by 2030, repressive sociocultural policies towards women, poor access to healthcare, malnutrition, rapid urbanization, climate change and pollution. Early life stress, whether physical or psychological, induces neuroinflammatory response in developing nervous system and consequently leads to the emergence of mental health problems during adulthood. Brain inflammatory response is driven largely by inflammatory mediators released by glial cells; namely astrocytes and microglia. These inflammatory mediators alter the developmental trajectory of fetal and neonatal brain and results in long-lasting maladaptive behaviors and cognitive deficits. This review seeks to highlight the patterns and mechanisms of stressors such as poverty, developmental stress, environmental pollutions as well as malnutrition stress on astrocytes and microglia in neuroinflammation within the African context.

Mechanisms of Kwashiorkor-Associated Immune Suppression: Insights From Human, Mouse, and Pig Studies

Malnutrition refers to inadequate energy and/or nutrient intake. Malnutrition exhibits a bidirectional relationship with infections whereby malnutrition increases risk of infections that further aggravates malnutrition. Severe malnutrition (SM) is the main cause of secondary immune deficiency and mortality among children in developing countries. SM can manifest as marasmus (non-edematous), observed most often (68.6% of all malnutrition cases), kwashiorkor (edematous), detected in 23.8% of cases, and marasmic kwashiorkor, identified in ~7.6% of SM cases. Marasmus and kwashiorkor occur due to calorie-energy and protein-calorie deficiency (PCD), respectively. Kwashiorkor and marasmic kwashiorkor present with reduced protein levels, protein catabolism rates, and altered levels of micronutrients leading to uncontrolled oxidative stress, exhaustion of anaerobic commensals, and proliferation of pathobionts. Due to these alterations, kwashiorkor children present with profoundly impaired immune function, compromised intestinal barrier, and secondary micronutrient deficiencies. Kwashiorkor-induced alterations contribute to growth stunting and reduced efficacy of oral vaccines. SM is treated with antibiotics and ready-to-use therapeutic foods with variable efficacy. Kwashiorkor has been extensively investigated in gnotobiotic (Gn) mice and piglet models to understand its multiple immediate and long-term effects on children health. Due to numerous physiological and immunological similarities between pigs and humans, pig represents a highly relevant model to study kwashiorkor pathophysiology and immunology. Here we summarize the impact of kwashiorkor on children's health, immunity, and gut functions and review the relevant findings from human and animal studies. We also discuss the reciprocal interactions between PCD and rotavirus-a highly prevalent enteric childhood pathogen due to which pathogenesis and immunity are affected by childhood SM.

Spatial variation and associated factors of deworming among children aged 24 to 59 months in Ethiopia: spatial and multilevel logistic analysis

Background

Intestinal parasitic infection is one of the neglected tropical diseases (NTD) which is mainly concentrated in developing countries. Gastrointestinal parasitic infections are diseases of poverty, which mainly affects children living in tropical and subtropical regions like Ethiopia. Deworming to children aged 24–59 months of age is one of the strategic initiatives to halt the global burden of intestinal parasitosis among under-five children. The information generated at local levels like hotspot areas (clusters with a high proportion of poor deworming uptake) that were identified in this study could help decision-makers to develop location-based interventional strategies.

Objective

This study was aimed to assess the spatial variation and factors associated with poor deworming uptake among children aged 24–59 months in Ethiopia using evidence from the 2016 Ethiopian Demographic Health Survey (EDHS).

Methods

To explore, create, visualize and edit the spatial information of poor uptake of deworming medication, ArcGIS version 10.8 software was used. The spatial pattern of poor deworming uptake was determined using global spatial autocorrelation. Purely spatial scan statistic was used to identify statistically significant hotspot areas using SaTScan™ version 9.7 software. Multilevel logistic regression analysis was fitted to identify factors associated with poor deworming uptake in Ethiopia. Variables with a p-value< 0.2 in the bivariable regression were considered for multivariable regression analysis. Adjusted odds ratio with a 95% confidence interval (CI) and p-value < 0.05 were used to declare the statistical significance of each factor.

Results

The spatial pattern of poor deworming uptake in Ethiopia was non-random, i.e. clustered. The most likely cluster was found concentrated in most parts of Somali and East Oromia. Variables like being born from an uneducated mother ((Adjusted Odds Ratio (AOR) = 1.65; 95% CI: 1.16–2.36)), being born from an unemployed mother (AOR = 1. 1.43; 95% CI: 1.19–1.74), being delivered at home (AOR = 1.60 95% CI: 1.27, 2.02), diarrhea in the last 2 weeks (AOR = 0.68, 95%CI: 0.51, 0.90), and region of residency were the significant variables associated with poor deworming medication uptake among children aged to 24 to 59 months in Ethiopia.

Conclusion

The spatial pattern of poor deworming uptake was non-random in Ethiopia. Variables like educational status, employment, distance, place of delivery, diarrhea and region of living were found associated with poor deworming uptake. Tailoring interventional programs based on identified clusters is recommended to minimize this unfavorable deworming uptake.

Modulation of immune responses to vaccination by the microbiota: implications and potential mechanisms

The need for highly effective vaccines that induce robust and long-lasting immunity has never been more apparent. However, for reasons that are still poorly understood, immune responses to vaccination are highly variable between different individuals and different populations. Furthermore, vaccine immunogenicity is frequently suboptimal in the very populations who are at most risk from infectious disease, including infants, the elderly, and those living in low-income and middle-income countries. Although many factors have the potential to influence vaccine immunogenicity and therefore vaccine effectiveness, increasing evidence from clinical studies and animal models now suggests that the composition and function of the gut microbiota are crucial factors modulating immune responses to vaccination. In this Review, we synthesize this evidence, discuss the immunological mechanisms that potentially mediate these effects and consider the potential of microbiota-targeted interventions to optimize vaccine effectiveness.

Oral nanomedicine for modulating immunity, intestinal barrier functions, and gut microbiome

The gastrointestinal tract (GIT) affects not only local diseases in the GIT but also various systemic diseases. Factors that can affect the health and disease of both GIT and the human body include 1) the mucosal immune system composed of the gut-associated lymphoid tissues and the lamina propria, 2) the intestinal barrier composed of mucus and intestinal epithelium, and 3) the gut microbiota. Selective delivery of drugs, including antigens, immune-modulators, intestinal barrier enhancers, and gut-microbiome manipulators, has shown promising results for oral vaccines, immune tolerance, treatment of inflammatory bowel diseases, and other systemic diseases, including cancer. However, physicochemical and biological barriers of the GIT present significant challenges for successful translation. With the advances of novel nanomaterials, oral nanomedicine has emerged as an attractive option to not only overcome these barriers but also to selectively deliver drugs to the target sites in GIT. In this review, we discuss the GIT factors and physicochemical and biological barriers in the GIT. Furthermore, we present the recent progress of oral nanomedicine for oral vaccines, immune tolerance, and anti-inflammation therapies. We also discuss recent advances in oral nanomedicine designed to fortify the intestinal barrier functions and modulate the gut microbiota and microbial metabolites. Finally, we opine about the future directions of oral nano-immunotherapy.

Diversity and dynamism of IgA-microbiota interactions

IgA mediates microbial homeostasis at the intestinal mucosa. Within the gut, IgA acts in a context-dependent manner to both prevent and promote bacterial colonization and to influence bacterial gene expression, thus providing exquisite control of the microbiota. IgA-microbiota interactions are highly diverse across individuals and populations, yet the factors driving this variation remain poorly understood. In this Review, we summarize evidence for the host, bacterial and environmental factors that influence IgA-microbiota interactions. Recent advances have helped to clarify the antigenic specificity and immune selection of intestinal IgA and have highlighted the importance of microbial glycan recognition. Furthermore, emerging evidence suggests that diet and nutrition play an important role in shaping IgA recognition of the microbiota. IgA-microbiota interactions are disrupted during both overnutrition and undernutrition and may be altered dynamically in response to diet, with potential implications for host health. We situate this research in the context of outstanding questions and future directions in order to better understand the fascinating paradigm of IgA-microbiota homeostasis.

Deworming Coverage and its Predictors among Ethiopian Children Aged 24 to 59 Months: Further Analysis of EDHS 2016 Data Set

Intestinal parasitic infections are the major public health problem globally, mostly in developing countries. World Health Organization recommends deworming to all at-risk people living in endemic areas as a prevention or intervention strategy. Therefore this study aimed to assess the deworming coverage and its predictors among Ethiopian children aged 24-59 months. The study analyzed retrospectively cross-sectional data on a weighted sample of 5,948 children aged 24-59 months nested within 645 clusters after extracting from the Ethiopian Demographic health survey. Bivariable and multivariable logistic regression was employed to assess the association of variables. Predictors at p-value < 0.25 were entered into the multivariable logistic regression model, and statistical significance was declared at P-value < 0.05. In this study, the prevalence of maternal reported deworming supplements among children aged 24-59 months was 15.1%. Predictive variables significantly associated with deworming supplementation include maternal media exposure, maternal control of household healthcare decisions, institutional healthcare delivery, and child vitamin-A supplementation. Having history of a diarrheal disease, maternal and paternal education, and family size were also statistically significant predictors of deworming supplements. Therefore, deworming supplementation among children is low. Maternal education and employment, paternal education, family size, decision-making process, maternal media exposure, place of delivery, vitamin-A supplementation, and a having history of diarrhea were predictors of deworming supplements. Multifaceted interventions aimed at those predictors should be given emphasis.

Thermostable, Dissolvable Buccal Film Rotavirus Vaccine Is Highly Effective in Neonatal Gnotobiotic Pig Challenge Model

Difficulties related to storage and transport of currently available live oral rotavirus vaccines can have detrimental consequences on the efficacy of the vaccines. Thus, there is a great need for thermostable vaccines that can eliminate the necessity for cold chain storage or reconstitution before administration. In this study, we developed a dissolvable oral polymeric film comprised of a live attenuated thermostable tetravalent rhesus-human reassortant rotavirus vaccine (RRV-TV) powder and antacid (CaCO₃). Immunogenicity and protective efficacy of the vaccine after buccal delivery was evaluated in the gnotobiotic pig model of human rotavirus (HRV) infection and diarrhea. Two doses of the vaccine were highly immunogenic and conferred strong protection against virus shedding and diarrhea upon challenge with a high dose of a virulent G1 HRV in gnotobiotic pigs. Those pigs vaccinated with the preserved film vaccine had significantly delayed onset of diarrhea; reduced duration and area under the curve of diarrhea; delayed onset of fecal virus shedding; and reduced duration and peak of fecal virus shedding titers compared to pigs in both the placebo and the reconstituted liquid oral RRV-TV vaccine groups. Associated with the strong protection, high titers of serum virus neutralization antibodies against each of the four RRV-TV mono-reassortants and G1 HRV-specific serum IgA and IgG antibodies, as well as intestinal IgA antibodies, were induced by the preserved film vaccine. These results demonstrated the effectiveness of our thermostable buccal film rotavirus vaccine and warrant further investigation into the promise of the novel technology in addressing drawbacks of the current live oral HRV vaccines.

An assessment of potential biomarkers of environment enteropathy and its association with age and microbial infections among children in Bangladesh

Interventional studies targeting environment enteropathy (EE) are impeded by the lack of appropriate, validated, non-invasive biomarkers of EE. Thus, we aimed to validate the association of potential biomarkers for EE with enteric infections and nutritional status in a longitudinal birth cohort study. We measured endotoxin core antibody (EndoCab) and soluble CD14 (sCD14) in serum, and myeloperoxidase (MPO) in feces using commercially available enzyme-linked immunosorbent assay (ELISA) kits. We found that levels of serum EndoCab and sCD14 increase with the cumulative incidence of enteric infections. We observed a significant correlation between the fecal MPO level in the children at 24 months of age with the total number of bacterial and viral infections, the total number of parasitic infections, and the total number of diarrheal episodes and diarrheal duration. We observed that the levels of serum EndoCab, sCD14, and fecal MPO at 3 months of age were significantly associated with whether children were malnourished at 18 months of age or not. Biomarkers such as fecal MPO, serum EndoCab and sCD14 in children at an early age may be useful as a measure of cumulative burden of preceding enteric infections, which are predictive of subsequent malnutrition status and may be useful non-invasive biomarkers for EE.

Strategies for Enhancement of Live-Attenuated Salmonella-Based Carrier Vaccine Immunogenicity

The use of live-attenuated bacterial vaccines as carriers for the mucosal delivery of foreign antigens to stimulate the mucosal immune system was first proposed over three decades ago. This novel strategy aimed to induce immunity against at least two distinct pathogens using a single bivalent carrier vaccine. It was first tested using a live-attenuated Salmonella enterica serovar Typhi strain in clinical trials in 1984, with excellent humoral immune responses against the carrier strain but only modest responses elicited against the foreign antigen. Since then, clinical trials with additional Salmonella-based carrier vaccines have been conducted. As with the original trial, only modest foreign antigen-specific immunity was achieved in most cases, despite the incorporation of incremental improvements in antigen expression technologies and carrier design over the years. In this review, we will attempt to deconstruct carrier vaccine immunogenicity in humans by examining the basis of bacterial immunity in the human gastrointestinal tract and how the gut detects and responds to pathogens versus benign commensal organisms. Carrier vaccine design will then be explored to determine the feasibility of retaining as many characteristics of a pathogen as possible to elicit robust carrier and foreign antigen-specific immunity, while avoiding over-stimulation of unacceptably reactogenic inflammatory responses.

Intestinal lysozyme releases Nod2 ligand(s) to promote the intestinal mucosal adjuvant activity of cholera toxin

Commensal bacteria boost serum IgG production in response to oral immunization with antigen and cholera toxin (CT) in a manner that depends on Nod2 (nucleotide-binding oligomerization domain-containing protein 2). In this study, we examined the role of intestinal lysozyme (Lyz1) in adjuvant activity of CT. We found that Lyz1 released Nod2 ligand(s) from bacteria. Lyz1 deficiency reduced the level of circulating Nod2 ligand in mice. Lyz1 deficiency also reduced the production of IgG and T-cellspecific cytokines after oral immunization in mice. Supplementing Lyz1-deficient mice with MDP restored IgG production. Furthermore, overexpression of Lyz1 in intestinal epithelium boosted the antigen-specific IgG response induced by CT. Collectively, our results indicate that Lyz1 plays an important role in mediating the immune regulatory effect of commensal bacteria through the release of Nod2 ligand(s).

Meningococcal vaccines and protein-energy undernutrition in children in the African meningitis belt

BACKGROUND

Vaccines to prevent meningococcal meningitis in the African meningitis belt include PsACWY, a polysaccharide-only vaccine; and PsA-TT, a polysaccharide-protein conjugate vaccine. Protein-energy undernutrition, a condition where children do not receive enough macro- or micronutrients, is related to increased risk of infectious diseases and poor immune function. Reduced immune function could affect vaccine immunogenicity. We investigated connections between protein-energy undernutrition and vaccine immunogenicity and antibody waning to PsACWY and PsA-TT in children in the African meningitis belt.

METHODS

This is a secondary analysis of data collected as part of four clinical trials testing the safety and efficacy of PsA-TT in children in Mali, Ghana, and Senegal. We identified whether anthropometric growth indices (low height-for-age, weight-for-height, or weight-for-age Z-score categories) were related to reduced vaccine-elicited antibody (measured with rabbit complement) from pre- to 1 month post-vaccination, in linear regression models. We also identified whether these growth indices were related to increased waning for vaccine-elicited antibody over time, in linear regression models.

RESULTS

A total of 697 children were included in our analysis, of which 350 (50.2%) were female; the mean (SD) age was 1.0 (1.1) years, and 578 (83.0%) received PsA-TT. In linear regression models, no consistent statistical relationship was seen between pre-vaccination anthropometric Z-score categories and vaccine immunogenicity, or decline in antibody over time, for either vaccine, although children with low weight-for-height had a greater decline in antibody from 1 to 6 months post-vaccination.

CONCLUSIONS

Our analysis did not find protein-energy undernutrition to be associated with immunogenicity or waning of PsACWY- or PsA-TT-elicited antibody in children living in the African meningitis belt. Future studies should consider measuring antibody titers at additional time points post-vaccination, and for longer periods of time, to determine if the rate of antibody waning over a period of several years is associated with protein-energy undernutrition.

Pattern, predictors and clustering of handwashing practices in India

Background

Research on handwashing continues to draw researchers' interest owing to its public health importance and significance in the reduction of infectious diseases. The aims of this study are to: (1) understand the pattern and predictors of handwashing using soap/detergent and water; and (2) assess the spatial clustering of handwashing through soap/detergent and water at the district level in India.

Methods

Data of households where the place for handwashing was observed by the research investigators (n = 582,064), gathered through the National Family Health Survey-4 (2015-2016), were used for this analysis. The availability of soap/detergent and water at the usual place of handwashing was assumed to be used for handwashing. Binary logistic regression was carried out to examine the adjusted effect of socioeconomic characteristics on the use of soap/detergent and water for handwashing. The univariate local indicator of spatial association (LISA) cluster map and Moran's I statistics were applied for assessing spatial autocorrelations at the district level. Analyses were carried out with IBM-SPSS Software.

Results

Two-fifths of Indian households do not use both soap/detergent and water for handwashing. Households using both the cleansing elements vary considerably by socioeconomic characteristics- worse for the socioeconomically disadvantaged groups. There is spatial clustering in the use of soap/detergent and water for handwashing: lower in a cluster of districts in eastern India.

Conclusion

Results suggest the need to generate awareness, particularly among the socioeconomically weaker populations, about advantages of hand hygiene, which will reduce the prevalence of infectious diseases like COVID-19 and be helpful to achieve many Sustainable Development Goals.

Safety and Ethics in Endoscopic Studies in Children: Evidence From the BEECH Study in Zambia

BACKGROUND

Environmental enteropathy is an example of a poorly-understood intestinal disorder affecting millions of children worldwide, characterized by malabsorption and stunting. Although there is increasing interest in non-invasive means of assessing intestinal structure and function, the potential value of intestinal biopsy for histology, immunostaining, RNA sequencing and epigenetic work means that endoscopic biopsy remains extremely valuable. We here report our experience in the BEECH (Biomarkers of Environmental Enteropathy in CHildren) study of stunting in Zambia, in the belief that it may help address the knowledge gap regarding the safety of endoscopic biopsy in vulnerable young children.

METHODS

We report our experience of safety in 119 children undergoing endoscopic biopsy in the BEECH study in Lusaka Children's Hospital, Lusaka, and discuss ethical considerations in this light.

RESULTS

Upper gastrointestinal endoscopy was performed on children with stunting (length-for-age z score -2 or less) not responsive to nutritional interventions. Conscious sedation was provided by anaesthetists. Of 119 children, 5 (4%) developed transient desaturation, but no serious adverse events were experienced; no clinical, demographic or anaesthetic characteristics were identified as predictive of desaturation. Two children derived clinically useful information from the endoscopy, one life-saving. Of 105 lactase tests, 59 (54%) showed hypolactasia.

DISCUSSION

Children with stunting underwent endoscopy safely, and some derived clinical benefit. Safety and the possibility of clinical benefit are usually felt to be preconditions for the ethical justification for endoscopy for research in children, and we believe that these conditions were met in this study.

Impact of Microbiota: A Paradigm for Evolving Herd Immunity against Viral Diseases

Herd immunity is the most critical and essential prophylactic intervention that delivers protection against infectious diseases at both the individual and community level. This process of natural vaccination is immensely pertinent to the current context of a pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection around the globe. The conventional idea of herd immunity is based on efficient transmission of pathogens and developing natural immunity within a population. This is entirely encouraging while fighting against any disease in pandemic circumstances. A spatial community is occupied by people having variable resistance capacity against a pathogen. Protection efficacy against once very common diseases like smallpox, poliovirus or measles has been possible only because of either natural vaccination through contagious infections or expanded immunization programs among communities. This has led to achieving herd immunity in some cohorts. The microbiome plays an essential role in developing the body’s immune cells for the emerging competent vaccination process, ensuring herd immunity. Frequency of interaction among microbiota, metabolic nutrients and individual immunity preserve the degree of vaccine effectiveness against several pathogens. Microbiome symbiosis regulates pathogen transmissibility and the success of vaccination among different age groups. Imbalance of nutrients perturbs microbiota and abrogates immunity. Thus, a particular population can become vulnerable to the infection. Intestinal dysbiosis leads to environmental enteropathy (EE). As a consequence, the generation of herd immunity can either be delayed or not start in a particular cohort. Moreover, disparities of the protective response of many vaccines in developing countries outside of developed countries are due to inconsistencies of healthy microbiota among the individuals. We suggested that pan-India poliovirus vaccination program, capable of inducing herd immunity among communities for the last 30 years, may also influence the inception of natural course of heterologous immunity against SARS-CoV-2 infection. Nonetheless, this anamnestic recall is somewhat counterintuitive, as antibody generation against original antigens of SARS-CoV-2 will be subdued due to original antigenic sin.

Soil-transmitted helminth infections and nutritional status of school children in government elementary schools in Jimma Town, Southwestern Ethiopia

Introduction

Soil-transmitted helminth infections and malnutrition are major health problems of school-age children in developing countries. Malnutrition and soil-transmitted helminth infections often co-exist with synergetic consequences.

Objective

The aim of this study was to determine the prevalence and intensity of soil-transmitted helminths and its association with nutritional status of school-age children.

Methods

School-based cross-sectional study was carried out from April to May 2014 among 404 elementary school-age children in Jimma Town, Southwest Ethiopia. Data on background characteristics were collected using structured interviewer administered questionnaire. Anthropometric measurements were taken according to World Health Organization standard. Fresh single stool sample was collected from each study participant and examined using direct wet mount and McMaster techniques. Anthropometric indices were generated using WHO AnthroPlus software. Multivariable logistic regression models were fitted to isolate independent predictors of intestinal parasitic infection and nutritional status using STATA-MP software. All tests were two-sided and P < 0.05 was used to declare statistical significance.

Results

The overall prevalence of intestinal parasites and soil-transmitted helminths were 68.6% (n = 277) and 55.0% (n = 222), respectively. A total of eight species of intestinal parasites were identified in this study, Trichuris trichiura being the most common parasite identified followed by Ascaris lumbricoides. Study participants who had a habit of open defecation were two times more likely to be infected with soil-transmitted helminths (adjusted odds ratio = 1.9, 95% confidence interval: 1.0-3.4). The overall prevalence of stunting and thinness were 21.0% (n = 85) and 6.9% (n = 28), respectively. The odds of stunting was significantly high (adjusted odds ratio = 4.0, 95% confidence interval: 1.7-9.7) among children who had fathers working as daily labourers and children with personal dietary diversity score of ⩽3 (adjusted odds ratio = 3.5, 95% confidence interval: 1.5-8.0). T. trichiura infection (adjusted odds ratio = 9.4, 95% confidence interval: 2.0-44.8) was identified as an independent predictor of stunting among school-age children.

Conclusion

Both the prevalence of soil-transmitted helminths and stunting are high among school-age children in Jimma Town. Although there was no statistically significant association between the STHs, in general, T. trichiura was reported as predictor of stunting. The results imply the need for strengthening strategies for reduction of parasitic infection to curb the pervasively high prevalence of stunting.

Local Perceptions, Cultural Beliefs, Practices and Changing Perspectives of Handling Infant Feces: A Case Study in a Rural Geita District, North-Western Tanzania

We report on the management of infant feces in a rural village in Geita region, Tanzania. Findings discussed here emerged incidentally from a qualitative study aimed at investigating vulnerability and resilience to health challenges in rural settings. Data was gathered through semi-structured focus group discussions (FDGs) with women (n = 4; 32 participants), men (n = 2; 16 participants), and community leaders (n = 1; 8 participants). All FDGs were audio recorded, transcribed verbatim and thematically analyzed using Atlas.ti. Respondents reported feces of a child under the age of six months were considered pure compared to those of older children. Infant feces were seen as transitioning to harmful at the point when the child began to eat solid food, resulting in their stool visually changing in appearance. Caregivers reportedly used soft implements to handle infant feces due to the belief that tools with hard surfaces would physically harm the child. Infant feces were disposed in environments around the house due to the belief that disposal in latrines would prevent developmental milestones and result in other perceived negative health outcomes for the child. Changing views expressed by participants suggest a window of opportunity to implement evidence-based and culturally relevant interventions to encourage the safe disposal of infant feces.

Commensal Bacteria Modulate Immunoglobulin A Binding in Response to Host Nutrition

Immunoglobulin (Ig) A controls host-microbial homeostasis in the gut. IgA recognition of beneficial bacteria is decreased in acutely undernourished children, but the factors driving these changes in IgA targeting are unknown. Child undernutrition is a global health challenge that is exacerbated by poor sanitation and intestinal inflammation. To understand how nutrition impacts immune-microbe interactions, we used a mouse model of undernutrition with or without fecal-oral exposure and assessed IgA-bacterial targeting from weaning to adulthood. In contrast to healthy control mice, undernourished mice fail to develop IgA recognition of intestinal Lactobacillus. Glycan-mediated interactions between Lactobacillus and host antibodies are lost in undernourished mice due to rapid bacterial adaptation. Lactobacillus adaptations occur in direct response to nutritional pressure, independently of host IgA, and are associated with reduced mucosal colonization and with bacterial mutations in carbohydrate processing genes. Together these data indicate that diet-driven bacterial adaptations shape IgA recognition in the gut.

Environmental enteric dysfunction and child stunting

In 2017, an estimated 1 in every 4 (23%) children aged < 5 years were stunted worldwide. With slow progress in stunting reduction in many regions and the realization that a large proportion of stunting is not due to insufficient diet or diarrhea alone, it remains that other factors must explain continued growth faltering. Environmental enteric dysfunction (EED), a subclinical state of intestinal inflammation, can occur in infants across the developing world and is proposed as an immediate causal factor connecting poor sanitation and stunting. A result of chronic pathogen exposure, EED presents multiple causal pathways, and as such the scope and sensitivity of traditional water, sanitation, and hygiene (WASH) interventions have possibly been unsubstantial. Although the definite pathogenesis of EED and the mechanism by which stunting occurs are yet to be defined, this paper reviews the existing literature surrounding the proposed pathology and transmission of EED in infants and considerations for nutrition and WASH interventions to improve linear growth worldwide.

Immune responses to O-specific polysaccharide (OSP) in North American adults infected with Vibrio cholerae O1 Inaba

Background

Antibodies targeting O-specific polysaccharide (OSP) of Vibrio cholerae may protect against cholera; however, little is known about this immune response in infected immunologically naïve humans.

Methodology

We measured serum anti-OSP antibodies in adult North American volunteers experimentally infected with V. cholerae O1 Inaba El Tor N16961. We also measured vibriocidal and anti-cholera toxin B subunit (CtxB) antibodies and compared responses to those in matched cholera patients in Dhaka, Bangladesh, an area endemic for cholera.

Principal findings

We found prominent anti-OSP antibody responses following initial cholera infection: these responses were largely IgM and IgA, and highest to infecting serotype with significant cross-serotype reactivity. The anti-OSP responses peaked 10 days after infection and remained elevated over baseline for ≥ 6 months, correlated with vibriocidal responses, and may have been blunted in blood group O individuals (IgA anti-OSP). We found significant differences in immune responses between naïve and endemic zone cohorts, presumably reflecting previous exposure in the latter.

Conclusions

Our results define immune responses to O-specific polysaccharide in immunologically naive humans with cholera, find that they are largely IgM and IgA, may be blunted in blood group O individuals, and differ in a number of significant ways from responses in previously humans. These differences may explain in part varying degrees of protective efficacy afforded by cholera vaccination between these two populations.

Trial registration number

ClinicalTrials.gov NCT01895855.

Cholera is an acute, secretory diarrheal disease caused by Vibrio cholerae O1. There is a growing body of evidence that immune responses targetting the O-specific polysaccharide (OSP) of V. cholerae are associated with protecton against cholera. Despite this, little is known about immune responses targeting OSP in immunologically naive individals. Cholera affects populations in severely resource-limited areas. To address this, we assessed anti-OSP immune responses in North American volunteers experimentally infected with wild type V. cholerae O1 El Tor Inaba strain N16961. We found that antibody responses were largely IgM and IgA, cross-reacted to both Inaba and Ogawa serotypes, and correlated with vibriocidal responses. We found no association of responses to severity of disease, but did find that blood group O individuals mounted lower IgA fold-changes to OSP than did non-blood group O individuals. Individuals with blood group O are at particular risk for severe cholera, and are less well protected against cholera following oral vaccination. We also compared anti-OSP responses in previously unexposed individuals to responses in matched endemic zone patients, and found a number of significant differences. Such differences may explain in part the varying degrees of protective efficacy afforded by cholera vaccination between these two populations.

Parenterally Administered P24-VP8* Nanoparticle Vaccine Conferred Strong Protection against Rotavirus Diarrhea and Virus Shedding in Gnotobiotic Pigs

Current live rotavirus vaccines are costly with increased risk of intussusception due to vaccine replication in the gut of vaccinated children. New vaccines with improved safety and cost-effectiveness are needed. In this study, we assessed the immunogenicity and protective efficacy of a novel P24-VP8* nanoparticle vaccine using the gnotobiotic (Gn) pig model of human rotavirus infection and disease. Three doses of P24-VP8* (200 μg/dose) intramuscular vaccine with Al(OH)₃ adjuvant (600 μg) conferred significant protection against infection and diarrhea after challenge with virulent Wa strain rotavirus. This was indicated by the significant reduction in the mean duration of diarrhea, virus shedding in feces, and significantly lower fecal cumulative consistency scores in post-challenge day (PCD) 1-7 among vaccinated pigs compared to the mock immunized controls. The P24-VP8* vaccine was highly immunogenic in Gn pigs. It induced strong VP8*-specific serum IgG and Wa-specific virus-neutralizing antibody responses from post-inoculation day 21 to PCD 7, but did not induce serum or intestinal IgA antibody responses or a strong effector T cell response, which are consistent with the immunization route, the adjuvant used, and the nature of the non-replicating vaccine. The findings are highly translatable and thus will facilitate clinical trials of the P24-VP8* nanoparticle vaccine.

Pathobiome driven gut inflammation in Pakistani children with Environmental Enteric Dysfunction

Environmental Enteric Dysfunction (EED) is an acquired small intestinal inflammatory condition underlying high rates of stunting in children <5 years of age in low- and middle-income countries. Children with EED are known to have repeated exposures to enteropathogens and environmental toxins that leads to malabsorptive syndrome. We aimed to characterize association of linear growth faltering with enteropathogen burden and subsequent changes in EED biomarkers. In a longitudinal birth cohort (n = 272), monthly anthropometric measurements (Length for Age Z score- LAZ) of asymptomatic children were obtained up to 18 months. Biological samples were collected at 6 and 9 months for the assessment of biomarkers. A customized TaqMan array card was used to target 40 enteropathogens in fecal samples. Linear regression was applied to study the effect of specific enteropathogen infection on change in linear growth (ΔLAZ). Presence of any pathogen in fecal sample correlated with serum flagellin IgA (6 mo, r = 0.19, p = 0.002), fecal Reg 1b (6 mo, r = 0.16, p = 0.01; 9mo, r = 0.16, p = 0.008) and serum Reg 1b (6 mo, r = 0.26, p<0.0001; 9 mo, r = 0.15, p = 0.008). At 6 months, presence of Campylobacter [β (SE) 7751.2 (2608.5), p = 0.003] and ETEC LT [β (SE) 7089.2 (3015.04), p = 0.019] was associated with increase in MPO. Giardia was associated with increase in Reg1b [β (SE) 72.189 (26.394), p = 0.006] and anti-flic IgA[β (SE) 0.054 (0.021), p = 0.0091]. Multiple enteropathogen infections in early life negatively correlated with ΔLAZ, and simultaneous changes in gut inflammatory and permeability markers. A combination vaccine targeting enteropathogens in early life could help in the prevention of future stunting.

How the gut microbiome regulates host immune responses to viral vaccines

The co-evolution of the microbiota and immune system has forged a mutually beneficial relationship. This relationship allows the host to maintain the balance between active immunity to pathogens and vaccines and tolerance to self-antigens and food antigens. In children living in low-income and middle-income countries, undernourishment and repetitive gastrointestinal infections are associated with the failure of oral vaccines. Intestinal dysbiosis associated with these environmental influences, as well as some host-related factors, compromises immune responses and negatively impacts vaccine efficacy. To understand how immune responses to viral vaccines can be optimally modulated, mechanistic studies of the relationship between the microbiome, host genetics, viral infections and the development and function of the immune system are needed. We discuss the potential role of the microbiome in modulating vaccine responses in the context of a growing understanding of the relationship between the gastrointestinal microbiota, host related factors (including histo-blood group antigens) and resident immune cell populations.

Role of the Microbiota in the Modulation of Vaccine Immune Responses

The human immune system and the microbiota co-evolve, and their balanced relationship is based on crosstalk between the two systems through the course of life. This tight association and the overall composition and richness of the microbiota play an important role in the modulation of host immunity and may impact the immune response to vaccination. The availability of innovative technologies, such as next-generation sequencing (NGS) and correlated bioinformatics tools, allows a deeper investigation of the crosstalk between the microbiota and human immune responses. This review discusses the current knowledge on the influence of the microbiota on the immune response to vaccination and novel tools to deeply analyze the impact of the microbiome on vaccine responses.

Vaccine development for enteric bacterial pathogens: Where do we stand?

Gut infections triggered by pathogenic bacteria lead to most frequently occurring diarrhea in humans accounting for million deaths annually. Currently, only a few licensed vaccines are available against these pathogens for mostly travelers moving to diarrheal endemic areas. Besides commercialized vaccines, there are many formulations that are either under clinical or pre-clinical stages of development and despite several efforts to improve safety, immunogenicity and efficacy, none of them can confer long-term protective immunity, for which repeated booster doses are always recommended. Further in many countries, financial, social and political constraints have jeopardized vaccine development program against these pathogens that enforce us to gather knowledge on safety, tolerability, immunogenicity and protective efficacy regarding the same. In this review, we analyze safety and efficacy issues of vaccines against five major gut bacteria causing enteric infections. The article also simultaneously describes several barriers for vaccine development and further discusses possible strategies to enhance immunogenicity and efficacy.

Effects of improved drinking water quality on early childhood growth in rural Uttar Pradesh, India: A propensity-score analysis

Context

Recent randomised controlled trials in Bangladesh and Kenya concluded that household water treatment, alone or in combination with upgraded sanitation and handwashing, did not reduce linear growth faltering or improve other child growth outcomes. Whether these results are applicable in areas with distinct constellations of water, sanitation and hygiene (WaSH) risks is unknown. Analysis of observational data offers an efficient means to assess the external validity of trial findings. We studied whether a water quality intervention could improve child growth in a rural Indian setting with higher levels of circulating pathogens than the original trial sites.

Methods

We analysed a cross-sectional dataset including a microbiological measure of household water quality. All households accessed water from an improved source. We applied propensity score methods to emulate a randomised trial investigating the hypothesis that receipt of drinking water meeting Sustainable Development Goal (SDG) 6.1 quality standards for absence of faecal contamination leads to improved growth. Growth outcomes (stunting, underweight, wasting, and their corresponding Z-scores) were assessed in children 12–23 months of age. For each outcome, we estimated the mean and 95% confidence interval of the absolute risk difference between treatment groups.

Findings

Of 1088 households, 442 (40.62%) received drinking water meeting SDG 6.1 standards. The adjusted risk of child underweight was 7.4% (1.3% to 13.4%) lower among those drinking water satisfying SDG 6.1 norms than among controls. Evidence concerning the relationship of drinking water meeting SDG 6.1 norms to length-for-age and weight-for-age was inconclusive, and there was no apparent relationship with stunting or wasting.

Conclusions

In contexts characterised by high pathogen transmission, water quality improvements have the potential to reduce the proportion of underweight children, but are unlikely to impact stunting or wasting. Further research is required to assess how these modelled benefits can best be achieved in real world settings.

Urbanization in Sub-Saharan Africa: Declining Rates of Chronic and Recurrent Infection and Their Possible Role in the Origins of Non-communicable Diseases

BACKGROUND

Non-communicable diseases (NCDs), such as atherosclerosis and cancers, are a leading cause of death worldwide. An important, yet poorly explained epidemiological feature of NCDs is their low incidence in under developed areas of low-income countries and rising rates in urban areas.

METHODS

With the goal of better understanding how urbanization increases the incidence of NCDs, we provide an overview of the urbanization process in sub-Saharan Africa, discuss gene expression differences between rural and urban populations, and review the current NCD determinant model. We conclude by identifying research priorities.

RESULTS

Declining rates of chronic and recurrent infection are the hallmark of urbanization in sub-Saharan Africa. Gene profiling studies show urbanization results in complex molecular changes, with almost one-third of the peripheral blood leukocyte transcriptome altered. The current NCD determinant model could be improved by including a possible effect from declining rates of infection and expanding the spectrum of diseases that increase with urbanization.

CONCLUSIONS

Urbanization in sub-Saharan Africa provides a unique opportunity to investigate the mechanism by which the environment influences disease epidemiology. Research priorities include: (1) studies to define the relationship between infection and risk factors for NCDs, (2) explaining the observed differences in the inflammatory response between rural and urban populations, and (3) identification of animal models that simulate the biological changes that occurs with urbanization. A better understanding of the biological changes that occur with urbanization could lead to new prevention and treatment strategies for some of the most common surgical diseases in high-income countries.

Pathophysiology of environmental enteric dysfunction and its impact on oral vaccine efficacy

Environmental enteric dysfunction (EED) refers to a subclinical disorder of intestinal function common in tropical countries and in settings of poverty and economic disadvantage. The enteropathy that underlies this syndrome is characterized by mucosal inflammation and villus blunting mediated by T cell activation. Epithelial cell disruption and microbial translocation drive systemic inflammation. EED in young children is associated geographically with growth failure, malnutrition, and greatly impaired responses to oral vaccines, notably rotavirus and poliovirus vaccines. In this review, we describe the pathophysiology of EED and examine the evidence linking EED and oral vaccine failure. This evidence is far from conclusive. Although our understanding of EED is still sketchy, there is limited evidence of disturbed innate immunity, B cell disturbances including aggregation into lymphoid follicles, and autoantibody generation. Pathways of T cell activation and the possibility of dendritic cell anergy, which could help explain oral vaccine failure, require further work.

Identifying the etiology and pathophysiology underlying stunting and environmental enteropathy: study protocol of the AFRIBIOTA project

BACKGROUND

Globally one out of four children under 5 years is affected by linear growth delay (stunting). This syndrome has severe long-term sequelae including increased risk of illness and mortality and delayed psychomotor development. Stunting is a syndrome that is linked to poor nutrition and repeated infections. To date, the treatment of stunted children is challenging as the underlying etiology and pathophysiological mechanisms remain elusive. We hypothesize that pediatric environmental enteropathy (PEE), a chronic inflammation of the small intestine, plays a major role in the pathophysiology of stunting, failure of nutritional interventions and diminished response to oral vaccines, potentially via changes in the composition of the pro- and eukaryotic intestinal communities. The main objective of AFRIBIOTA is to describe the intestinal dysbiosis observed in the context of stunting and to link it to PEE. Secondary objectives include the identification of the broader socio-economic environment and biological and environmental risk factors for stunting and PEE as well as the testing of a set of easy-to-use candidate biomarkers for PEE. We also assess host outcomes including mucosal and systemic immunity and psychomotor development. This article describes the rationale and study protocol of the AFRIBIOTA project.

METHODS

AFRIBIOTA is a case-control study for stunting recruiting children in Bangui, Central African Republic and in Antananarivo, Madagascar. In each country, 460 children aged 2-5 years with no overt signs of gastrointestinal disease are recruited (260 with no growth delay, 100 moderately stunted and 100 severely stunted). We compare the intestinal microbiota composition (gastric and small intestinal aspirates; feces), the mucosal and systemic immune status and the psychomotor development of children with stunting and/or PEE compared to non-stunted controls. We also perform anthropological and epidemiological investigations of the children's broader living conditions and assess risk factors using a standardized questionnaire.

DISCUSSION

To date, the pathophysiology and risk factors of stunting and PEE have been insufficiently investigated. AFRIBIOTA will add new insights into the pathophysiology underlying stunting and PEE and in doing so will enable implementation of new biomarkers and design of evidence-based treatment strategies for these two syndromes.

Exploring the relationship between environmental enteric dysfunction and oral vaccine responses

Oral vaccines significantly underperform in low-income countries. One possible contributory factor is environmental enteric dysfunction (EED), a subclinical disorder of small intestinal structure and function among children living in poverty. Here, we review studies describing oral vaccine responses and EED. We identified eight studies evaluating EED and oral vaccine responses. There was substantial heterogeneity in study design and few consistent trends emerged. Four studies reported a negative association between EED and oral vaccine responses; two showed no significant association; and two described a positive correlation. Current evidence is therefore insufficient to determine whether EED contributes to oral vaccine underperformance. We identify roadblocks in the field and future research needs, including carefully designed studies those can investigate this hypothesis further.

Role of maternal health and infant inflammation in nutritional and neurodevelopmental outcomes of two-year-old Bangladeshi children

BACKGROUND

Previous studies have shown maternal, inflammatory, and socioeconomic variables to be associated with growth and neurodevelopment in children from low-income countries. However, these outcomes are multifactorial and work describing which predictors most strongly influence them is lacking.

METHODOLOGY/PRINCIPAL FINDINGS

We conducted a longitudinal study of Bangladeshi children from birth to two years to assess oral vaccine efficacy. Variables pertaining to maternal and perinatal health, socioeconomic status, early childhood enteric and systemic inflammation, and anthropometry were collected. Bayley-III neurodevelopmental assessment was conducted at two years. As a secondary analysis, we employed hierarchical cluster and random forests techniques to identify and rank which variables predicted growth and neurodevelopment. Cluster analysis demonstrated three distinct groups of predictors. Mother's weight and length-for-age Z score (LAZ) at enrollment were the strongest predictors of LAZ at two years. Cognitive score on Bayley-III was strongly predicted by weight-for-age (WAZ) at enrollment, income, and LAZ at enrollment. Top predictors of language included Rotavirus vaccination, plasma IL 5, sCD14, TNFα, mother's weight, and male gender. Motor function was best predicted by fecal calprotectin, WAZ at enrollment, fecal neopterin, and plasma CRP index. The strongest predictors for social-emotional score included plasma sCD14, income, WAZ at enrollment, and LAZ at enrollment. Based on the random forests' predictions, the estimated percentage of variation explained was 35.4% for LAZ at two years, 34.3% for ΔLAZ, 42.7% for cognitive score, 28.1% for language, 40.8% for motor, and 37.9% for social-emotional score.

CONCLUSIONS/SIGNIFICANCE

Birth anthropometry and maternal weight were strong predictors of growth while enteric and systemic inflammation had stronger associations with neurodevelopment. Birth anthropometry was a powerful predictor for all outcomes. These data suggest that further study of stunting in low-income settings should include variables relating to maternal and prenatal health, while investigations focusing on neurodevelopmental outcomes should additionally target causes of systemic and enteric inflammation.

High SMAD7 and p-SMAD2,3 expression is associated with environmental enteropathy in children

Enteropathies such as Crohn's disease are associated with enteric inflammation characterized by impaired TGF-β signaling, decreased expression of phosphorylated (p)-SMAD2,3 and increased expression of SMAD7 (an inhibitor of SMAD3 phosphorylation). Environmental enteropathy (EE) is an acquired inflammatory disease of the small intestine (SI), which is associated with linear growth disruption, cognitive deficits, and reduced oral vaccine responsiveness in children <5 y in resource-poor countries. We aimed to characterize EE inflammatory pathways by determining SMAD7 and p-SMAD2,3 levels (using Western blotting) in EE duodenal biopsies (N = 19 children, 7 from Pakistan, 12 from Zambia) and comparing these with healthy controls (Ctl) and celiac disease (CD) patients from Italy. Densitometric analysis of immunoblots showed that EE SI biopsies expressed higher levels of both SMAD7 (mean±SD in arbitrary units [a.u.], Ctl = 0.47±0.20 a.u., EE = 1.13±0.25 a.u., p-value = 0.03) and p-SMAD2,3 (mean±SD, Ctl = 0.38±0.14 a.u., EE = 0.60±0.10 a.u., p-value = 0.03). Immunohistochemistry showed that, in EE, SMAD7 is expressed in both the epithelium and in mononuclear cells of the lamina propria (LP). In contrast, p-SMAD3 in EE is expressed much more prominently in epithelial cells than in the LP. The high SMAD7 immunoreactivity and lack of p-SMAD3 expression in the LP suggests defective TGF-β signaling in the LP in EE similar to a previously reported SMAD7-mediated inflammatory pathway in refractory CD and Crohn's disease. However, Western blot densitometry showed elevated p-SMAD2,3 levels in EE, possibly suggesting a different inflammatory pathway than Crohn's disease but more likely reflecting cumulative protein expression from across all compartments of the mucosa as opposed to the LP alone. Further studies are needed to substantiate these preliminary results and to illustrate the relationship between SMAD proteins, TGF-β signaling, and inflammatory cytokine production, all of which may be potential therapeutic targets.

Effect of innate antiviral glycoproteins in breast milk on seroconversion to rotavirus vaccine (Rotarix) in children in Lusaka, Zambia

Introduction

Rotavirus vaccines have been introduced into national immunization programmes to mitigate morbidity and mortality associated rotavirus diarrhoea. Lower vaccine effectiveness has however been noted in low-middle income countries, but little is known about the role of maternal components found in breast milk. This study assessed the effect of lactoferrin, lactadherin, and tenascin-c on rotavirus vaccine seroconversion.

Methods

This was a retrospective cohort study of 128 infants who had been fully immunized with Rotarix™. Serum samples were collected from the infant at baseline and one month after second rotavirus vaccine dose. Breast milk samples were collected from mothers at baseline. Standard ELISA was used to determine titres of rotavirus-specific immunologlobulin G and A in breast milk and serum as well as concentrations of lactoferrin, lactadherin, and tenascin-c. Poisson regression model with robust standard error was used to estimate the effect of breast milk components on seroconversion. The components were modelled on log base 2 so that the effect would be interpreted as a doubling of the concentration.

Results

In a multivariable analysis adjusting for maternal age, maternal HIV status, seropositivity at baseline, sex, age of child at vaccination as well as breast milk IgA and IgG, we found evidence of independent effect of LA (Adjusted IRR = 0.95; 95% CI = 0.91–0.99; P = 0.019) on seroconversion while there was no evidence for TNC (Adjusted IRR = 1.00; 95% CI = 0.85–1.17; P = 0.967) and LF (Adjusted RR = 1.01; 95% CI = 0.96–1.05); P = 0.802). We explored the joint effects of the three components but we found no evidence (Adjusted RR = 0.95; 95% CI = 0.81; P = 0.535).

Conclusion

High breast milk concentrations of lactadherin might play a role in infant’s failure to seroconvert to rotavirus vaccines. Further research to understand this observed association is an important consideration.

Enteropathogens and Gut Inflammation in Asymptomatic Infants and Children in Different Environments in Southern India

Children in poor environmental conditions are exposed early and often to enteric pathogens, but within developing countries, heterogeneity in enteropathogen exposure in different settings and communities is rarely addressed. We tested fecal samples from healthy infants and children from two different environments in the same Indian town for gut enteropathogens and biomarkers of gut inflammation. A significantly higher proportion of infants and children from a poor semi-urban neighborhood (93%) had one or more enteropathogens than those from a medical college campus (71.7%). Infants and children from the poor neighborhood had an average of 3.3 (95% confidence interval [CI]: 2.9-3.7) enteropathogens compared with an average of 1.4 (95% CI: 1.0-1.7) enteropathogens in campus infants/children. Viral and bacterial infections, including enteroviruses, adenoviruses, Campylobacter spp., and diarrhegenic Escherichia coli were more common and fecal biomarkers of inflammation were higher in the poor neighborhood. The findings demonstrate significant difference in the asymptomatic carriage of gut enteropathogens and gut inflammatory biomarkers in infants and children from two different environments within the same town in south India.

Sanitation facilities, hygienic conditions, and prevalence of acute diarrhea among under-five children in slums of Addis Ababa, Ethiopia: Baseline survey of a longitudinal study

BACKGROUND

In developing countries, children under the age of five years who live in slums are highly vulnerable to diarrhea. However, there is a paucity of information on the relationship between sanitation facilities and hygienic conditions to acute diarrhea among under-five children in slum areas of Addis Ababa, Ethiopia. Therefore, this study examines the sanitation facilities and hygienic conditions in the slums of Addis Ababa and identifies the main factors significantly associated with acute diarrhea among children aged 0-50 months in those slums.

METHODS

A community-based cross-sectional household survey was carried out between September and November 2014, that then served as the baseline survey of a longitudinal study. For this survey, 697 children aged 0-50 months were recruited from two slum districts in Addis Ababa. A pre-tested structured questionnaire and an observational checklist were used for data collection. Multivariable logistic regression analysis was used to identify sanitation facilities and hygiene-related factors that were significantly associated with acute diarrhea by controlling potential confounding effects of selected socio-demographic factors. Adjusted odds ratio (AOR) with corresponding 95% confidence interval (CI) was used to quantify the strength of association.

MAIN FINDINGS

The prevalence of acute diarrhea among children aged 0-50 months in the study area was 11.9% and 94.6% of the sanitation facilities were unimproved. Sharing of a sanitation facility by six or more households (AOR = 4.7; 95% CI: 2.4-9.4), proximity of sanitation facilities within 15 meters of homes (AOR = 6.6; 95% CI: 2.5-17.0), presence of feces (AOR = 3.9; 95% CI: 1.5-10.3) and flies (AOR = 2.5; 95% CI: 1.3-5.0) on the floor of and/or around sanitation facilities, and presence of uncollected garbage inside house compounds (AOR = 3.2; 95% CI: 1.2-8.4) were significantly associated with acute diarrhea.

CONCLUSION

This study reveals the slum environment to be high risk for diarrhea due to close proximity of sanitation facilities to homes, sharing of sanitation facilities, and poor hygiene of the sanitation facilities and housing compounds. We recommend the development of a comprehensive diarrheal disease prevention program that focuses on improving the cleanliness of the sanitation facilities and housing compounds. Increasing the number of improved sanitation facilities at an appropriate distance from houses is also essential in order to reduce the number of households that share one latrine.

The Burden of Enteropathy and "Subclinical" Infections

Environmental enteropathy is a chronic condition of the small intestine associated with increased intestinal permeability, mucosal inflammation, malabsorption, and systemic inflammation. It is commonly accompanied by enteric infections and is misleadingly considered a subclinical disease. Potential effects of enteric infections and enteropathy on vaccine responses, child growth, cognitive development, and even later life obesity, diabetes, and metabolic syndrome are increasingly being recognized. Herein, we review the evolving challenges to defining environmental enteropathy and enteric infections, current evidence for the magnitude and determinants of its burden, new assessment tools, and relevant interventions.

A methodologic framework for modeling and assessing biomarkers of environmental enteropathy as predictors of growth in infants: an example from a Peruvian birth cohort

Background: Environmental enteropathy (EE) impairs the gut's absorptive capacity and immune function and causes decelerations in statural growth that manifest gradually over time.Objective: To illustrate an approach for assessing emerging biomarkers of EE, we separately assessed the associations between 3 such markers and subsequent nutritional status.Design: Stool samples were routinely collected between January 2010 and November 2014 from a cohort of 303 Peruvian infants and analyzed for concentrations of the biomarkers α-1-antitrypsin (AAT), myeloperoxidase, and neopterin. For each marker, a mixed-effects linear regression model was fitted for length-for-age z scores (LAZs) obtained from anthropometric assessments that incorporated covariate predictors, polynomial terms for age, and product interaction terms to test associations over varying lag lengths. The biomarkers' contribution to the models was assessed with the use of the likelihood ratio test and partial R² statistics.Results: Test statistics for the combined inclusion of the 4-model terms that involved the biomarker were highly statistically significant for AAT (28.71; P < 0.0001) and myeloperoxidase (62.79; P < 0.0001) over a 3-mo lag and moderately so for neopterin (13.97; P = 0.0074). AAT and myeloperoxidase seemed to interact strongly with age, with the magnitude and direction of the effect varying considerably over the first 3 y of life. The largest proportion of the variance explained by any biomarker (2.8%) and the largest difference in LAZ predicted between the 5th and 95th percentile (0.25) was by myeloperoxidase over a 2-mo lag.Conclusions: Of the 3 fecal biomarkers studied, 2 that related to intestinal function-AAT and myeloperoxidase-were associated with small but highly statistically significant differences in future statural growth trajectories in infants in this cohort, lending further evidence to the EE hypothesis that increased gut permeability and inflammation adversely affects subsequent nutritional status. This association exhibited a complex interaction with age. This trial was registered at clinicaltrials.gov as NCT02441426.

Neurodevelopment: The Impact of Nutrition and Inflammation During Early to Middle Childhood in Low-Resource Settings

The early to middle childhood years are a critical period for child neurodevelopment. Nutritional deficiencies, infection, and inflammation are major contributors to impaired child neurodevelopment in these years, particularly in low-resource settings. This review identifies global research priorities relating to nutrition, infection, and inflammation in early to middle childhood neurodevelopment. The research priority areas identified include: (1) assessment of how nutrition, infection, or inflammation in the preconception, prenatal, and infancy periods (or interventions in these periods) affect function in early to middle childhood; (2) assessment of whether effects of nutritional interventions vary by poverty or inflammation; (3) determination of the feasibility of preschool- and school-based integrated nutritional interventions; (4) improved assessment of the epidemiology of infection- and inflammation-related neurodevelopmental impairment (NDI); (5) identification of mechanisms through which infection causes NDI; (6) identification of noninfectious causes of inflammation-related NDI and interventions for causes already identified (eg, environmental factors); and (7) studies on the effects of interactions between nutritional, infectious, and inflammatory factors on neurodevelopment in early to middle childhood. Areas of emerging importance that require additional study include the effects of maternal Zika virus infection, childhood environmental enteropathy, and alterations in the child's microbiome on neurodevelopment in early to middle childhood. Research in these key areas will be critical to the development of interventions to optimize the neurodevelopmental potential of children worldwide in the early to middle childhood years.

Application of penalized linear regression methods to the selection of environmental enteropathy biomarkers

BACKGROUND

Environmental Enteropathy (EE) is a subclinical condition caused by constant fecal-oral contamination and resulting in blunting of intestinal villi and intestinal inflammation. Of primary interest in the clinical research is to evaluate the association between non-invasive EE biomarkers and malnutrition in a cohort of Bangladeshi children. The challenges are that the number of biomarkers/covariates is relatively large, and some of them are highly correlated.

METHODS

Many variable selection methods are available in the literature, but which are most appropriate for EE biomarker selection remains unclear. In this study, different variable selection approaches were applied and the performance of these methods was assessed numerically through simulation studies, assuming the correlations among covariates were similar to those in the Bangladesh cohort. The suggested methods from simulations were applied to the Bangladesh cohort to select the most relevant biomarkers for the growth response, and bootstrapping methods were used to evaluate the consistency of selection results.

RESULTS

Through simulation studies, SCAD (Smoothly Clipped Absolute Deviation), Adaptive LASSO (Least Absolute Shrinkage and Selection Operator) and MCP (Minimax Concave Penalty) are the suggested variable selection methods, compared to traditional stepwise regression method. In the Bangladesh data, predictors such as mother weight, height-for-age z-score (HAZ) at week 18, and inflammation markers (Myeloperoxidase (MPO) at week 12 and soluable CD14 at week 18) are informative biomarkers associated with children's growth.

CONCLUSIONS

Penalized linear regression methods are plausible alternatives to traditional variable selection methods, and the suggested methods are applicable to other biomedical studies. The selected early-stage biomarkers offer a potential explanation for the burden of malnutrition problems in low-income countries, allow early identification of infants at risk, and suggest pathways for intervention.

TRIAL REGISTRATION

This study was retrospectively registered with ClinicalTrials.gov, number NCT01375647, on June 3, 2011.

Contribution of Maternal Immunity to Decreased Rotavirus Vaccine Performance in Low- and Middle-Income Countries

The role of maternal immunity, received by infants either transplacentally or orally from breast milk, in rotavirus vaccine (RV) performance is evaluated here. Breastfeeding withholding has no effect on vaccine responses, but higher levels of transplacental rotavirus-specific IgG antibody contribute to reduced vaccine seroconversion. The gaps in knowledge on the factors associated with low RV efficacy in low- and middle-income countries (LMIC) remain, and further research is needed to shed more light on these issues.

Modeling human enteric dysbiosis and rotavirus immunity in gnotobiotic pigs

Background

Rotavirus vaccines have poor efficacy in infants from low- and middle-income countries. Gut microbiota is thought to influence the immune response to oral vaccines. Thus, we developed a gnotobiotic (Gn) pig model of enteric dysbiosis to study the effects of human gut microbiota (HGM) on immune responses to rotavirus vaccination, and the effects of rotavirus challenge on the HGM by colonizing Gn pigs with healthy HGM (HHGM) or unhealthy HGM (UHGM). The UHGM was from a Nicaraguan infant with a high enteropathy score (ES) and no seroconversion following administration of oral rotavirus vaccine, while the converse was characteristic of the HHGM. Pigs were vaccinated, a subset was challenged, and immune responses and gut microbiota were evaluated.

Results

Significantly more rotavirus-specific IFN-γ producing T cells were in the ileum, spleen, and blood of HHGM than those in UHGM pigs after three vaccine doses, suggesting HHGM induces stronger cell-mediated immunity than UHGM. There were significant correlations between multiple Operational Taxonomic Units (OTUs) and frequencies of IFN-γ producing T cells at the time of challenge. There were significant positive correlations between Collinsella and CD8+ T cells in blood and ileum, as well as CD4+ T cells in blood, whereas significant negative correlations between Clostridium and Anaerococcus, and ileal CD8+ and CD4+ T cells. Differences in alpha diversity and relative abundances of OTUs were detected between the groups both before and after rotavirus challenge.

Conclusion

Alterations in microbiome diversity and composition along with correlations between certain microbial taxa and T cell responses warrant further investigation into the role of the gut microbiota and certain microbial species on enteric immunity. Our results support the use of HGM transplanted Gn pigs as a model of human dysbiosis during enteric infection, and oral vaccine responses.

Electronic supplementary material

The online version of this article (doi:10.1186/s13099-016-0136-y) contains supplementary material, which is available to authorized users.