Toll-Like Receptors and Mannose Binding Lectin Gene Polymorphisms Associated with Cryptosporidial Diarrhea in Children in Southern India.

Farzana Begum Liakath,Honorine Ward,Gagandeep Kang,Chanduni Syed,Sitara S R Ajjampur,Prasanna Samuel Premkumar,Savitha Varatharajan

doi:10.4269/ajtmh.20-0617

Abstract

ABSTRACT.In low-resource settings, Cryptosporidium spp. is a common cause of diarrheal disease in children under the age of 3 years. In addition to diarrhea, these children also experience subclinical episodes that have been shown to affect growth and cognitive function. In this study, we screened polymorphisms in the promoter and exon1 regions of the mannose binding lectin 2 (MBL2) gene, as well as single nucleotide polymorphisms (SNPs) described in toll-like receptors (TLR) TLR1, TLR2, TLR4, and TLR9 and TIR domain-containing adaptor protein (TIRAP) genes among children with cryptosporidial diarrhea (cases) and children who only experienced asymptomatic (subclinical) cryptosporidiosis (controls). Among the polymorphisms screened, the variant allele B at codon 54 (rs1800450) of the MBL2 gene was associated with susceptibility to cryptosporidial diarrhea (odds ratio [OR] = 2.2, 95% confidence interval [CI] 1.1–4.5). When plasma MBL levels were compared, 72% of cases were found to be deficient compared with 32% among controls (OR = 5.09). Among TLR polymorphisms screened, multivariate analysis showed that heterozygous genotypes of TLR4 896A/G (rs4986790, OR = 0.33, 95% CI: 0.11–0.98) and TIRAP 539 C/T (rs8177374, OR = 0.19, 95% CI: 0.06–0.64) SNPs were associated with protection from cryptosporidial diarrhea. Although not statistically significant, these findings suggest that polymorphisms of MBL2 and TLR genes influence susceptibility to symptomatic cryptosporidial diarrhea even in settings with high exposure levels. Further studies to validate these findings in a larger cohort and to understand the role of these polymorphisms in mediating innate and adaptive immune responses to cryptosporidial infection are necessary.

Highlights

Diarrhea is the second leading cause of morbidity and mortality in children under the age of 5 years in low- to middleincome countries.[1]
Among toll-like receptors (TLR) polymorphisms screened, multivariate analysis showed that heterozygous genotypes of TLR4 896A/G and TIR domain-containing adaptor protein (TIRAP) 539 C/T single nucleotide polymorphisms (SNPs) were associated with protection from cryptosporidial diarrhea
These findings suggest that polymorphisms of mannose binding lectin 2 (MBL2) and TLR genes influence susceptibility to symptomatic cryptosporidial diarrhea even in settings with high exposure levels

Summary

Introduction

Diarrhea is the second leading cause of morbidity and mortality in children under the age of 5 years in low- to middleincome countries.[1] The Global Enteric Multi-Center Study and Malnutrition and Enteric Diseases studies as well as the Global Burden of Diseases estimates have identified Cryptosporidium spp. as one of the commonest causes of diarrhea in children under 5 years of age in low- to middle-income countries.[2,3,4] Cryptosporidium-associated diarrhea alone accounts for more than 48,000 deaths and more than 4.2 million disability-adjusted life years lost per year.[3] Children in countries such as Bangladesh, Peru, Malawi, Israel, and India experience multiple episodes of subclinical or asymptomatic cryptosporidial infections that have been associated with malnutrition, stunting, and cognitive deficits.[5,6] Birth cohort studies have shown that children in low-resource settings such as urban slums in the Indian subcontinent are exposed to Cryptosporidium spp. by age 3 years (97% in Vellore, Tamil Nadu, and 77% in Mirpur, Bangladesh), experiencing either diarrheal or subclinical episodes.[7,8] The heterogeneity in symptoms and why some children tend to experience overt diarrhea and others only subclinical infections in the same living conditions remain largely unknown. Multiple infections (both symptomatic and subclinical) tend to cluster, with children with more than two or three episodes having an increased likelihood of being reinfected, suggesting a genetic predisposition to infection.[7]

Methods

Results

Conclusion