CLASSIFICATION OF ROTAVIRUS VP4 AND VP7 SEROTYPES

Rotaviruses, members of the Reoviridae family, are major etiologic age nts of acute nonbacterial gastroenteritis of the young in a wide varie ty of mammalian and avian species, including humans. The need for effe ctive immunoprophylaxis against rotaviral gastroenteritis has stimulat ed interest in the biochemical, molecular, genetic, and clinical aspec ts of these agents with the aim of developing safe and effective vacci nes. Because neutralizing antibodies appear to play an important role in protection against many viral diseases, rotavirus antigens that ind uce neutralizing antibodies have played a central role in research and development of a rotavirus vaccine. The VP7 glycoprotein and VP4 spik e protein that constitute the outer capsid of a complete rotavirus par ticle have been shown to be independent neutralization antigens. Since type specificity of the outer capsid proteins of a rotavirus appears to play an important role in protection against disease in experimenta l animal models, continued efforts have been made for classification a nd typing of neutralization specificities on the VP7 or VP4 capsid pro tein. Based on a criterion of >20-fold differences between the homolog ous and heterologous reciprocal neutralizing antibody titers, fourteen VP7 (G) serotypes have been established. Studies are underway to char acterize and classify the VP4 (P) serotypes among the strains that exh ibit the fourteen different G serotypes. Attempts to classify the VP4 serotypes based on the same criterion (i.e., >20-fold antibody differe nces) that is applied to classification of VP7 serotypes are in progre ss. This standard of >20-fold antibody differences can be applied with hyperimmune serum raised to a reassortant possessing the VP4 encoding gene (and an unrelated VP7 encoding gene). Genotypes can provide lead s towards classification but the serotype of a strain should be based on neutralization.