Isolation And Serotypic Characterization Of Rotaviruses

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Abstract

In this project we determine the antigenic relationships based on VP4 and VP7 neutralization specificities of various rotavirus strains derived from humans and animals. The elucidation of the neutralization specificities of rotaviruses is important in order to achieve a more comprehensive understanding of rotavirus epidemiology and for formulation of an effective strategy for vaccination. Of 5 globally important VP7 (G) serotypes (G1-4 and 9) of rotaviruses, G9 continues to attract considerable attention because of its unique natural history. Serotype G9 rotavirus was isolated from a child with diarrhea first in the US in 1983 and subsequently in Japan in 1985. Curiously, soon after their detection, G9 rotaviruses were not detected for about a decade in both countries and then reemerged in both countries in the mid-1990s. Unexpectedly, however, such reemerged G9 strains were distinct genetically and molecularly from those isolated in the 1980s. Thus, the origin of the reemerged G9 viruses remains an enigma. Sequence analysis has demonstrated that the G9 rotavirusVP7 gene belongs to one of at least three phylogenetic lineages: lineage 1 (strains isolated in the 1980s in the US and Japan), lineage 2 (strains first isolated in 1986 and exclusively in India thus far) and lineage 3 (strains that emerged/reemerged in the mid-1990s). Currently, lineage 3 G9 viruses are the most frequently detected G9 strains globally. We characterized a porcine rotavirus (A2 strain) isolated in the US. The A2 strain was found to bear serotype G9 and P9 specificities as well as NSP4 [B] and subgroup I characteristics. By VP7-specific neutralization, the porcine G9 strain was more closely related to lineage 3 viruses than to lineage 1 or 2 viruses. Furthermore, by sequence analysis, the A2 VP7 was shown to belong to lineage 3 G9. These findings raise intriguing questions regarding possible explanations for the emergence of variations among the G9 strains. In addition, we have established a PCR-ELISA methodology to G and P genotype human rotaviruses.