Isolation and characterization of a new simian rotavirus, YK-1.

BACKGROUND: To effectively analyze the requirements for protection to rotavirus infection, a reliable animal model that reasonably mimics infection and disease in humans is needed. A requirement for an effective animal model is the availability of appropriate rotavirus stocks for challenge. RESULTS: A new simian rotavirus, designated YK-1, was isolated from a 2-year-old immunodeficient pigtailed macaque with chronic diarrhea. YK-1 was distinguishable by electropherotype from the other simian rotavirus strains, SA11 and RRV. One variant of YK-1, clone 311, which was isolated after adaptation and plaque purification in cell cultures, displayed an unusual RNA electropherotype with an abnormally migrating gene 11 segment. Sequence analysis demonstrated a genetic rearrangement that involved a partial duplication of the gene 11 ORF encoding NSP5. YK-1 was identified as a Group A rotavirus belonging to subgroup 1. To further characterize the YK-1 strain, the genes encoding VP4, VP7, and NSP4 were sequenced. Analysis of VP4 and VP7 gene fragments suggests that this strain is a G3P3 rotavirus and is closely related to the simian rotavirus strain RRV. Serotype analysis also identified YK-1 as a G3 rotavirus. The NSP4 genotype of YK-1 is C, the same genotype as RRV. CONCLUSION: This newly isolated rotavirus, YK-1, is being used to establish a nonhuman primate model for studying the infectivity, immunity, and pathogenesis of rotavirus and for evaluating candidate rotavirus vaccines.

Molecular characterization of human rotavirus vaccine strain CDC-9 during sequential passages in Vero cells.

We have developed several candidate human rotavirus vaccine strains with common serotypes via adaptation in Vero cells, adhering to the Good Laboratory Practice (GLP) guidelines. We sequenced the entire genome of a G1P[8] strain CDC-9 in original stool and passaged materials from Vero cells and examined its genetic relatedness to the prototype human rotavirus KU and other strains. With the exception of VP3 gene which was closely related to that of strain DS-1, the culture-adapted CDC-9 strain shared moderate to high nt (range 83.4%-95.1%) and deduced aa (range 81.3%-97.9%) sequence identities with the KU and other G1P[8] strains. Alignments of the deduced aa sequences of 11 gene segments of the wild-type and culture-adapted CDC-9 showed complete sequence identity in genes encoding NSP2, NSP3, NSP4, VP1, VP2, VP3 and VP7, a single aa change in genes coding for NSP1, NSP5 and VP6 and several scattered aa changes in the VP4 gene during the passage in Vero cells. Two of the VP4 aa substitutions (385 and 388) are within sites associated with neutralization resistant mutants selected by cross-reactive monoclonal antibodies. Although some sequence changes were evident, we do not know if these changes contribute to the possible attenuation of this strain. Further testing of this vaccine strain in clinical trials is justified.