Influence of human leukocyte antigen class II alleles on susceptibility to Entamoeba histolytica infection in Bangladeshi children.

BACKGROUND The association of antibody responses with both innate and acquired immunity to amebiasis indicate that CD4+ T cells play a role in protection against Entamoeba histolytica infection. To test this hypothesis, we compared the genotype frequencies of human leukocyte antigen (HLA) class II alleles in a cohort of Bangladeshi children intensively monitored for E. histolytica infection for a 3-year period. METHODS Using logistic regression, we calculated the odds of disease by genotype and by haplotype. RESULTS The DQB1*0601 heterozygous and homozygous genotypes were found in 55% of E. histolytica-negative children but in only 34% of E. histolytica-positive children (overall odds ratio, 2.39; 95% confidence interval [CI], 1.26-4.54). Children who were heterozygous for the DQB1*0601/DRB1*1501 haplotype were 10.1 times (95% CI, 2.02-50.6) more likely to be both E. histolytica negative and serum anti-lectin immunoglobulin G negative at baseline. Other DQB1 and DRB1 alleles (DQB1*0202, DQB1*0301, and DRB1*0701) were not associated with any of the clinical outcomes related to amebiasis. CONCLUSION A potential protective association was observed with the HLA class II allele DQB1*0601 and the heterozygous haplotype DQB1*0601/DRB1*1501. This association may explain why amebiasis does not occur in some children who are exposed to the parasite and implicates HLA class II-restricted immune responses in protection against E. histolytica infection.