Rotavirus Nonstructural Protein NSP4 Induces Heterotypic Antibody Responses during Natural Infection in Children

Seroconversion of immunoglobulin A (IgA) and immunoglobulin G (IgG) (> or =4-fold rise) to rotavirus nonstructural protein 4 (NSP4) was determined, by use of enzyme-linked immunosorbent assay with fusion proteins glutathione S-transferase (GST)-NSP4 from strains SA11 (A), 116E (B), and RRV (C), in 40 children with acute rotavirus gastroenteritis and in 30 with the same disease due to other pathogens. The IgG seroconversion rates in the rotavirus group were 67.5%, 70%, and 60% when recombinant (r) NSP4A, -B, and -C, respectively, were used as antigen in the assay, and, for rotavirus-uninfected children, rates were 10%, 13%, and 7%. IgA seroconversion occurred in 57%, 70%, and 50%, respectively, of children with rotavirus gastroenteritis; in rotavirus-uninfected children, 1 child each seroconverted to the different rNSP4s. Among 9 children infected with strain NSP4A, 7, 6, and 5 children showed IgG seroconversion, and, among 18 infected with NSP4A, -B, and -C, 16, 17, and 15, respectively, showed IgG seroconversion. Between NSP4A-infected and NSP4B-infected children, IgA responses were similar to IgG responses. In conclusion, significant NSP4-specific antibody response occurs in natural rotavirus infection, and the antibody response appears to be broad and heterotypic in nature.