Role of coproantibody in clinical protection of children during reinfection with rotavirus.

Rotavirus is the major cause of severe, dehydrating infantile gastroenteritis. Infection is limited to the gut, but the relative roles of serum and secretory copro-immunoglobulin A (IgA) in protection are unclear. Specific copro-IgA is predictive of duodenal antirotaviral IgA and correlates with virus-neutralizing coproantibody. Copro-IgA conversion is a more sensitive marker of rotavirus reinfection than seroconversion. We measured rotavirus reinfections by copro-IgA conversion prospectively in 35 children recruited at a time of severe rotavirus illness. The children were followed up longitudinally for 14 to 31 months to determine whether high coproantibody levels correlated with clinical protection against rotavirus disease. Ninety-four percent of the children experienced reinfection, and 38% developed persistent elevations in specific copro-IgA termed plateaus. Plateau children had a higher mean annual rate of rotavirus infection and a lower ratio of symptomatic to total number of rotavirus reinfections than did nonplateau children. The annual rates of rotavirus infection and disease were significantly higher outside the plateau than inside it in children experiencing antirotavirus copro-IgA plateaus. Frequent rotavirus infection of children appears to stimulate production of a specific copro-IgA plateau which correlates with protection against an excess of infection and symptomatic disease.