Immunologic Methods and Correlates of Protection

Studies of natural rotavirus (RV) infection in children have shown that protection against subsequent RV disease occurs (1 ). Assessment of humoral immune responses has included study of the importance of circulating vs intestinal antibodies (Abs), serotype-specific vs group-specific Abs, and RV-specific immunoglobulins IgA, IgM, and IgG (1 ). Following natural RV infection, RV-specific IgM, followed by IgA and IgG, appear in serum and duodenal fluid or stool of young children (2 ). Protection against subsequent RV infection is predicted by the quantity of virus-specific IgA in the feces and serum (3 , 4 ). In addition, virus-specific antibody-secreting cells (ASC) of the IgA, IgM, and IgG isotypes have been detected in the blood of infants following RV infection (5 ), although correlation between the presence of ASCs and protection against subsequent disease has not been studied. Serum neutralizing antibodies (nAbs) occur after natural RV infection in children, and are serotype-specific (4 ,6 ). Overall, protection against subsequent RV infection is correlated with higher titers of nAb (4 ). Protection against infection has been correlated with homotypic nAb to the G1 serotype (4 ); however, other studies suggest that protection is not dependent on serotype-specific nAb (7 ).