Validation of the Micronutrient and Environmental Enteric Dysfunction Assessment Tool and evaluation of biomarker risk factors for growth faltering and vaccine failure in young Malian children

Dietary aflatoxins exposure, environmental enteropathy, and their relation with childhood stunting

Childhood stunting is a global phenomenon affecting more than 149 million children under the age of 5 worldwide. Exposure to aflatoxins (AFs) in utero, during breastfeeding, and consumption of contaminated food affect the gut microbiome, resulting in intestinal dysfunction and potentially contributing to stunting. This review explores the potential relationship between AF exposure, environmental enteropathy and childhood stunting. AFs bind to DNA, disrupt protein synthesis and elicit environmental enteropathy (EE). An EE alters the structure of intestinal epithelial cells, impairs nutrient uptake and leads to malabsorption. This article proposes possible intervention strategies for researchers and policymakers to reduce AF exposure, EE and childhood stunting, such as exposure reduction, the implementation of good agricultural practices, dietary diversification and improving environmental water sanitation and hygiene.

The 2022 Vaccines Against Shigella and Enterotoxigenic Escherichia coli (VASE) Conference: Summary of breakout workshops

The global public health nonprofit organization PATH hosted the third Vaccines Against Shigella and Enterotoxigenic Escherichia coli (VASE) Conference in Washington, DC, from November 29 to December 1, 2022. This international gathering focused on cutting-edge research related to the development of vaccines against neglected diarrheal pathogens including Shigella, enterotoxigenic Escherichia coli (ETEC), Campylobacter, and non-typhoidal Salmonella. In addition to the conference's plenary content, the agenda featured ten breakout workshops on topics of importance to the enteric vaccine field. This unique aspect of VASE Conferences allows focused groups of attendees to engage in in-depth discussions on subjects of interest to the enteric vaccine development community. In 2022, the workshops covered a range of topics. Two focused on the public health value of enteric vaccines, with one examining how to translate evidence into policy and the other on the value proposition of potential combination vaccines against bacterial enteric pathogens. Two more workshops explored new tools for the development and evaluation of vaccines, with the first on integrating antigen/antibody technologies for mucosal vaccine and immunoprophylactic development, and the second on adjuvants specifically for Shigella vaccines for children in low- and middle-income countries. Another pair of workshops covered the status of vaccines against two emerging enteric pathogens, Campylobacter and invasive non-typhoidal Salmonella. The remaining four workshops examined the assessment of vaccine impact on acute and long-term morbidity. These included discussions on the nature and severity of intestinal inflammation; cellular immunity and immunological memory in ETEC and Shigella infections; clinical and microbiologic endpoints for Shigella vaccine efficacy studies in children; and intricacies of protective immunity to enteric pathogens. This article provides a brief summary of the presentations and discussions at each workshop in order to share these sessions with the broader enteric vaccine field.

Assessment of the role of gut health in childhood stunting in a multisite, longitudinal study in India, Indonesia and Senegal: a UKRI GCRF Action Against Stunting Hub protocol

INTRODUCTION

Childhood stunting has a complex aetiology, with poor gut health being an important contributor. This study will assess inter-relationships between maternal and infant gut health indices and infant linear growth. Inter-relationships between gut health indices, systemic inflammation and growth hormones in early childhood will also be assessed.

METHODS AND ANALYSIS

A longitudinal observational study of cohorts of 600 newborns and their mothers in India, Indonesia and Senegal will be conducted. Women will be recruited during pregnancy and their children followed up to age 24 months. Stool, urine and blood samples will be collected from the women and children for assessments of helminthic and protozoal parasites, bacterial pathogens, faecal microbiota taxa, biomarkers of environmental enteric dysfunction, systemic inflammation and growth hormones. Child anthropometric measurements will be collected at birth and at ages 3, 6, 9, 12, 18 and 24 months. The gut health indices will be integrated with cohort data from other Action Against Stunting Hub (AASH) workstreams for interdisciplinary analyses of childhood stunting and the development of a new typology of stunting.

DISCUSSION

This study will advance scientific understanding of the role of gut health in childhood stunting and will contribute to a broader knowledge of the complex aetiology of this condition as part of the interdisciplinary AASH research to reduce the global burden of childhood stunting.

ETHICS AND DISSEMINATION

This study has been approved by the relevant Ethics Committees in Senegal, India, and Indonesia and LSHTM. The results will be submitted for publication in peer-reviewed journals.

Association of biomarkers of enteric dysfunction, systemic inflammation, and growth hormone resistance with seroconversion to oral rotavirus vaccine: A lasso for inference approach

BACKGROUND

Rotavirus gastroenteritis remains a leading cause of morbidity and mortality despite the introduction of vaccines. Research shows there are several factors contributing to the reduced efficacy of rotavirus vaccines in low- and middle-income settings. Proposed factors include environmental enteric dysfunction (EED), malnutrition, and immune dysfunction. This study aimed to assess the effect of these factors on vaccine responses using a machine learning lasso approach.

METHODS

Serum samples from two rotavirus clinical trials (CVIA 066 n = 99 and CVIA 061 n = 124) were assessed for 11 analytes using the novel Micronutrient and EED Assessment Tool (MEEDAT) multiplex ELISA. Immune responses to oral rotavirus vaccines (Rotarix, Rotavac, and Rotavac 5D) as well as a parenteral rotavirus vaccine (trivalent P2-VP8) were also measured and machine learning using the lasso approach was then applied to investigate any associations between immune responses and environmental enteric dysfunction, systemic inflammation, and growth hormone resistance biomarkers.

RESULTS

Both oral and parenteral rotavirus vaccine responses were negatively associated with retinol binding protein 4 (RBP4), albeit only weakly for oral vaccines. The parenteral vaccine responses were positively associated with thyroglobulin (Tg) and histidine-rich protein 2 (HRP2) for all three serotypes (P8, P6 and P4), whilst intestinal fatty acid binding protein (I-FABP) was negatively associated with P6 and P4, but not P8, and soluble transferrin receptor (sTfR) was positively associated with P6 only.

CONCLUSION

MEEDAT successfully measured biomarkers of growth, systemic inflammation, and EED in infants undergoing vaccination, with RBP4 being the only analyte associated with both oral and parenteral rotavirus vaccine responses. Tg and HRP2 were associated with responses to all three serotypes in the parenteral vaccine, while I-FABP and sTfR results indicated possible strain specific immune responses to parenteral immunization.

Vaccine value profile for enterotoxigenic Escherichia coli (ETEC)

Enterotoxigenic Escherichia coli (ETEC) is one of the leading bacterial causes of diarrhoea, especially among children in low-resource settings, and travellers and military personnel from high-income countries. WHO's primary strategic goal for ETEC vaccine development is to develop a safe, effective, and affordable ETEC vaccine that reduces mortality and morbidity due to moderate-to-severe diarrhoeal disease in infants and children under 5 years of age in LMICs, as well as the long-term negative health impact on infant physical and cognitive development resulting from infection with this enteric pathogen. An effective ETEC vaccine will also likely reduce the need for antibiotic treatment and help limit the further emergence of antimicrobial resistance bacterial pathogens. The lead ETEC vaccine candidate, ETVAX, has shown field efficacy in travellers and has moved into field efficacy testing in LMIC infants and children. A Phase 3 efficacy study in LMIC infants is projected to start in 2024 and plans for a Phase 3 trial in travellers are under discussion with the U.S. FDA. Licensing for both travel and LMIC indications is projected to be feasible in the next 5-8 years. Given increasing recognition of its negative impact on child health and development in LMICs and predominance as the leading etiology of travellers' diarrhoea (TD), a standalone vaccine for ETEC is more cost-effective than vaccines targeting other TD pathogens, and a viable commercial market also exists. In contrast, combination of an ETEC vaccine with other vaccines for childhood pathogens in LMICs would maximize protection in a more cost-effective manner than a series of stand-alone vaccines. This 'Vaccine Value Profile' (VVP) for ETEC is intended to provide a high-level, holistic assessment of available data to inform the potential public health, economic and societal value of pipeline vaccines and vaccine-like products. This VVP was developed by a working group of subject matter experts from academia, non-profit organizations, public private partnerships, and multi-lateral organizations. All contributors have extensive expertise on various elements of the ETEC VVP and collectively aimed to identify current research and knowledge gaps. The VVP was developed using only existing and publicly available information.

Association of Circulating Biomarkers with Growth and Cognitive Development in Rural Tanzania: A Secondary Analysis of the Early Life Interventions in Childhood Growth and Development In Tanzania (ELICIT) Study

BACKGROUND

Children in low-resource areas experience nutritional and infection challenges delaying growth and cognitive development.

OBJECTIVE

Our goal was to assess for associations of circulating biomarkers related to nutrition and inflammation, with growth and developmental outcomes among children in a birth cohort in a resource-poor area in rural Tanzania.

METHODS

We assessed data from 1120 children participating in the Early Life Interventions for Childhood Growth and Development in Tanzania (ELICIT) study. At age 12 and 18 months participants had blood tests performed for hemoglobin, collagen-X, insulin-like growth factor-1 (IGF-1), fibroblast growth-factor-21 (FGF21), thyroglobulin, ferritin, soluble transferrin receptor (sTFR), retinol binding protein-4 (RBP4), C-reactive protein (CRP), alpha(1)-acid glycoprotein (AGP), and CD14. At 18 months, participants had anthropometry measured and converted to z-scores for length-for-age (LAZ), weight-for-age (WAZ) and head-circumference-for-age (HCZ) and had the Malawi Developmental Assessment Tool (MDAT) performed to evaluate cognitive development. We performed linear regression assessing biomarkers (predictor variable) on anthropometry and MDAT scores (dependent variables), adjusted for sex, socioeconomic status and baseline values.

RESULTS

There was a high degree of intra-factor correlation between 12 and 18 months, and inter-factor correlation between biomarkers. IGF-1 and sTFR were positively- and FGF21 and ferritin negatively-associated with LAZ 18 months, while collagen-X and CD14 were additionally associated with recent linear growth. Only markers predominantly related to nutrition were consistently linked with WAZ at 18 months, while RBP4 and AGP were additionally associated with recent change in WAZ. IGF-1 was positively- and thyroglobulin, RBP4 and CD14 negatively linked to MDAT scores. IGF-1 was the only factor linked to both 18-month LAZ and MDAT.

CONCLUSIONS

Individual biomarkers were consistently linked to growth and cognitive outcomes, providing support for relationships between nutrition and inflammation in early child development. Further research is needed to assess overlaps in how biomarker-related processes interact with both growth and learning.

Assessing environmental enteric dysfunction via multiplex assay and its relation to growth and development among HIV-exposed uninfected Tanzanian infants

BACKGROUND

Environmental enteric dysfunction (EED) may contribute to poor growth and development in young children. While validated EED biomarkers are currently lacking, multiplex assays are able to capture multiple domains of the condition. The purpose of this exploratory study was to examine the relationship between biomarkers of EED and subsequent growth and development among Tanzanian HIV-exposed uninfected (HEU) infants.

METHODOLOGY

We enrolled 467 infants of mothers living with HIV who had participated in a trial of vitamin D3 supplementation during pregnancy. Infant serum samples collected at 6 weeks (n = 365) and 6 months (n = 266) were analyzed for anti-flagellin and anti-lipopolysaccharide (LPS) IgA and IgG via ELISA as well as the 11-plex Micronutrient and EED Assessment Tool (MEEDAT), which incorporates two biomarkers of EED [intestinal fatty acid-binding protein (I-FABP) and soluble CD14 (sCD14)]. Outcomes were 12-month growth [length-for-age z-score (LAZ), weight-for-length z-score (WLZ), and weight-for-age z-score (WAZ)] and development [Caregiver Reported Early Development Instruments (CREDI) z-scores] and were assessed using linear regression.

FINDINGS

In primary analyses, higher quartiles of 6-month anti-LPS IgG concentrations were significantly associated with lower LAZ at 12 months (ptrend = 0.040). In secondary analyses, higher log2-transformed 6-week anti-flagellin IgA and 6-month anti-LPS IgA concentrations were significantly associated with lower LAZ at 12 months. No associations were observed between I-FABP or sCD14 and infant growth. However, higher log2-transformed 6-week sCD14 concentrations were significantly associated with lower overall CREDI z-scores, while higher log2-transformed 6-month I-FABP concentrations were significantly associated with higher overall CREDI z-scores.

CONCLUSIONS

Unlike anti-flagellin and anti-LPS Igs, MEEDAT's biomarkers of EED (I-FABP and sCD14) were not associated with subsequent linear growth among HEU infants in Tanzania. The relationship between EED and infant development warrants further study.

Gut biomolecules (I-FABP, TFF3 and lipocalin-2) are associated with linear growth and biomarkers of environmental enteric dysfunction (EED) in Bangladeshi children

In the current world, a major challenge to diagnose environmental enteric dysfunction (EED) is the lack of validated non-invasive biomarkers. Intestine derived molecules, including intestinal fatty acid binding protein (I-FABP), trefoil factor-3 (TFF3), lactoferrin, lipocalin-2 (LCN2), and mucin-2, have been reported as indicators of intestinal inflammation and gut health. Therefore, we aimed to investigate the levels of these bio-molecules as biomarkers of EED among under-2 children in Bangladesh. A total of 140 children were recruited in a case-control design. All the biomarkers were measured by ELISA. Spearman's rank correlation was performed to see the correlation between the biomarkers and the EED score. Moreover, multivariable linear regression was performed to investigate the association of biomarkers with length-for-age z-score (LAZ). TFF3 correlates positively with myeloperoxidase (r = 0.26, p < 0.05) and EED score (r = 0.17, p < 0.05). Likewise, LCN2 correlates positively with myeloperoxidase (r = 0.37, p < 0.05), neopterin (r = 0.33, p < 0.05) and EED score (r = 0.31, p < 0.05). Moreover, multivariable linear regression revealed a negative association of I-FABP with LAZ of the study participants. Our results imply that TFF3 and LCN2 might be promising biomarkers to diagnose intestinal inflammation and EED, while I-FABP is negatively associated with linear growth of Bangladeshi children.

Association of Anti-Rotavirus IgA Seroconversion with Growth, Environmental Enteric Dysfunction and Enteropathogens in Rural Pakistani Infants

BACKGROUND

The underperformance of oral vaccines in children of low- and middle-income countries is partly attributable to underlying environmental enteric dysfunction (EED).

METHODOLOGY

We conducted a longitudinal, community-based study to evaluate the association of oral rotavirus vaccine (Rotarix®) seroconversion with growth anthropometrics, EED biomarkers and intestinal enteropathogens in Pakistani infants. Children were enrolled between three to six months of their age based on their nutritional status. We measured serum anti-rotavirus immunoglobulin A (IgA) at enrollment and nine months of age with EED biomarkers and intestinal enteropathogens.

RESULTS

A total of 391 infants received two doses of rotavirus (RV) vaccine. 331/391 provided paired blood samples. Of these 331 children, 45% seroconverted at 9 months of age, 35% did not seroconvert and 20% were seropositive at baseline. Non-seroconverted children were more likely to be stunted, wasted and underweight at enrollment. In univariate analysis, insulin-like growth factor (IGF) concentration at 6 months were higher in seroconverters, median (25th, 75th percentile): 26.3 (16.5, 43.5) ng/ml vs. 22.5 (13.6, 36.3) ng/ml for non-seroconverters, p-value = 0.024. At nine months, fecal myeloperoxidase (MPO) concentrations were significantly lower in seroconverters, 3050(1250, 7587) ng/ml vs. 4623.3 (2189, 11650) ng/ml in non-seroconverted children, p-value = 0.017. In multivariable logistic regression analysis, alpha-1 acid glycoprotein (AGP) and IGF-1 concentrations were positively associated with seroconversion at six months. The presence of sapovirus and rotavirus in fecal samples at the time of rotavirus administration, was associated with non-seroconversion and seroconversion, respectively.

CONCLUSION

We detected high baseline RV seropositivity and impaired RV vaccine immunogenicity in this high-risk group of children. Healthy growth, serum IGF-1 and AGP, and fecal shedding of rotavirus were positively associated with RV IgA seroconversion following immunization, whereas the presence of sapovirus was more common in non-seroconverters.

TRIAL REGISTRATION

Clinical Trials ID: NCT03588013.

Shigella-Controlled Human Infection Models: Current and Future Perspectives

Shigella-controlled human infection models (CHIMs) are an invaluable tool utilized by the vaccine community to combat one of the leading global causes of infectious diarrhea, which affects infants, children and adults regardless of socioeconomic status. The impact of shigellosis disproportionately affects children in low- and middle-income countries (LMICs) resulting in cognitive and physical stunting, perpetuating a cycle that must be halted. Shigella-CHIMs not only facilitate the early evaluation of enteric countermeasures and up-selection of the most promising products but also provide insight into mechanisms of infection and immunity that are not possible utilizing animal models or in vitro systems. The greater understanding of shigellosis obtained in CHIMs builds and empowers the development of new generation solutions to global health issues which are unattainable in the conventional laboratory and clinical settings. Therefore, refining, mining and expansion of safe and reproducible infection models hold the potential to create effective means to end diarrheal disease and associated co-morbidities associated with Shigella infection.

A multicenter analytical performance evaluation of a multiplexed immunoarray for the simultaneous measurement of biomarkers of micronutrient deficiency, inflammation and malarial antigenemia

A lack of comparative data across laboratories is often a barrier to the uptake and adoption of new technologies. Furthermore, data generated by different immunoassay methods may be incomparable due to a lack of harmonization. In this multicenter study, we describe validation experiments conducted in a single lab and cross-lab comparisons of assay results to assess the performance characteristics of the Q-plex™ 7-plex Human Micronutrient Array (7-plex), an immunoassay that simultaneously quantifies seven biomarkers associated with micronutrient (MN) deficiencies, inflammation and malarial antigenemia using plasma or serum; alpha-1-acid glycoprotein, C-reactive protein, ferritin, histidine-rich protein 2, retinol binding protein 4, soluble transferrin receptor, and thyroglobulin. Validations included repeated testing (n = 20 separately prepared experiments on 10 assay plates) in a single lab to assess precision and linearity. Seven independent laboratories tested 76 identical heparin plasma samples collected from a cohort of pregnant women in Niger using the same 7-plex assay to assess differences in results across laboratories. In the analytical validation experiments, intra- and inter-assay coefficients of variation were acceptable at <6% and <15% respectively and assay linearity was 96% to 99% with the exception of ferritin, which had marginal performance in some tests. Cross-laboratory comparisons showed generally good agreement between laboratories in all analyte results for the panel of 76 plasma specimens, with Lin's concordance correlation coefficient values averaging ≥0.8 for all analytes. Excluding plates that would fail routine quality control (QC) standards, the inter-assay variation was acceptable for all analytes except sTfR, which had an average inter-assay coefficient of variation of ≥20%. This initial cross-laboratory study demonstrates that the 7-plex test protocol can be implemented by users with some experience in immunoassay methods, but familiarity with the multiplexed protocol was not essential.