Antigen-Specific Memory B-cell Responses to Enterotoxigenic Escherichia coli Infection in Bangladeshi Adults

Background:multiple infections with diverse enterotoxigenic e. coli (etec) strains lead to broad spectrum protection against etec diarrhea. however,the precise mechanism of protection against etec infection is still unknown. therefore,memory b cell responses and affinity maturation of antibodies to the specific etec antigens might be important to understand the mechanism of protection.methodology:in this study,we investigated the heat labile toxin b subunit (ltb) and colonization factor antigens (cfa/i and cs6) specific iga and igg memory b cell responses in bangladeshi adults (n = 52) who were infected with etec. we also investigated the avidity of iga and igg antibodies that developed after infection to these antigens.principal findings:patients infected with etec expressing lt or lt+heat stable toxin (st) and cfa/i group or cs6 colonization factors developed ltb,cfa/i or cs6 specific memory b cell responses at day 30 after infection. similarly,these patients developed high avidity iga and igg antibodies to ltb,cfa/i or cs6 at day 7 that remained significantly elevated at day 30 when compared to the avidity of these specific antibodies at the acute stage of infection (day 2). the memory b cell responses,antibody avidity and other immune responses to cfa/i not only developed in patients infected with etec expressing cfa/i but also in those infected with etec expressing cfa/i cross-reacting epitopes. we also detected a significant positive correlation of ltb,cfa/i and cs6 specific memory b cell responses with the corresponding increase in antibody avidity.conclusion:this study demonstrates that natural infection with etec induces memory b cells and high avidity antibodies to ltb and colonization factor cfa/i and cs6 antigens that could mediate anamnestic responses on re-exposure to etec and may help in understanding the requirements to design an effective vaccination strategies. © 2014 alam et al.