IgA is Important for Clearance and Critical for Protection from Rotavirus Infection

Based on a lack of severe phenotype in human IgA deficiency syndromes, the role of IgA in controlling respiratory and gastrointestinal (GI) infections has not been clearly defined. C57BL/6 and BALB/c mice lacking IgA (IgA(−/−)) were developed and used to address this question. When exposed to a common GI virus, rotavirus, IgA(−/−) mice exhibited a substantial and significant delay in clearance of the initial infection compared to wild type mice. IgA(−/−) mice excreted rotavirus in stool up to three weeks after the initial exposure compared to ten days observed in wild type mice. Importantly, IgA(−/−) mice failed to develop protective immunity against multiple repeat exposures to the virus. All IgA(−/−) mice excreted virus in the stool upon re-exposure to rotavirus while wild type mice were completely protected against re-infection. These findings clearly indicate a critical role for IgA in the establishment of immunity against a GI viral pathogen.