Immune Responses to Helicobacter pylori Infection in Bangladeshi Children during Their First Two Years of Life and the Association between Maternal Antibodies and Onset of Infection

Background. A birth cohort of 238 children in Bangladesh was monitored during the initial 2 years of life to analyze immune responses against Helicobacter pylori in relation to infection and spontaneous eradication and to evaluate a possible association between maternal antibodies and protection against early onset of infection. Methods. H. pylori infection was determined by a stool antigen test and serologic testing. Immune responses were analyzed in depth in 50 children. Results and conclusions. Of the stool antigen-positive children, 90% developed >= 4-fold increased antibody levels against H. pylori in serum immunoglobulin (Ig) A, 73% developed increases in serum IgG levels, and 81% developed increases in stool IgA/total IgA levels after, as compared with before, the onset of infection. Good agreement between different immune responses was observed after 6 months of age. Before that time, transplacentally derived IgG and breast milk IgA antibodies interfered with the children's serum IgG and stool IgA responses. Children infected during the first year of life had significantly lower preinfection serum IgG titers than those infected during the second year of life. Infants infected during the first month of life were fed breast milk that contained levels of H. pylori IgA antibodies that were significantly lower than the levels in breast milk fed to infants infected at 6 months of age. Children who experienced spontaneous eradication of infection developed significantly higher serum IgA antibody levels after infection than did children with continuous infection.