Rapid serotyping of human rotavirus strains by solid-phase immune electron microscopy

Abstract

Nine cell culture-adapted, as well as 30 clinical, human rotavirus (HRV) strains from fecal extracts of children with primary HRV infection were typed by rapid solid-phase immune electron microscopy with protein A and absorbed DS-1 (HRV serotype 2), Wa (serotype 1) and VA70 (assumed serotype 3) rabbit immune sera. As a reference typing test for cell culture-adapted strains, the neutralization assay was used, whereas for noncultivatable strains typing was done for comparison, indirectly, based upon the differential neutralization reactivity of convalescent-phase serum samples from patients with primary HRV infection vs. the 3 reference HRV serotypes. Typing results by solid-phase immune electron microscopy for all strains examined were in complete agreement with those obtained by the neutralization assay, both on cell culture-adapted strains with the 3 reference rabbit antisera and on 3 reference HRV strains with human convalescent-phase serum samples. Since adaptation to growth in cell cultures of clinical HRV strains from stool specimens is a time-consuming procedure and is often unsuccessful, solid-phase immune electron microscopy is preferred over the neutralizing assay, giving results in .apprx. 16 h and also allowing typing of HRV strains from stool specimens low in virus particles. HRV strains reacting differently from the three reference serotypes may be easily selected by solid-phase immune electron microscopy for further characterization, as was the case for 1 strain in this study.