Analysis of RNAs and Proteins of Rotaviruses With Rearranged Genomes: A Study of Molecular Variability

Genome heterogeneity among cocirculating human rotaviruses (hrv) has been described in different parts of the world and in this project was exemplified by a small collection of 100 specimens collected from infected children in Britain between 1975 and 1983. Pedley et al. (1984) described protracted hrv infections and virus shedding in children who suffered from severe combined immunodeficiency (SCID). The viruses isolated from the children showed abnormal genomes carrying extra bands of dsRNA which were found to have arisen by rearrangement of normal RNA segments to covalently linked concatemers. Rotaviruses with similar genomes were obtained after serial passage in-vitro at high m.o.i.: Hundley et al. (1985) isolated mutants D, A4, B4 and B5 of bovine rotavirus (brv) whose genomes had lost RNA segment 5 and instead carried additional RNA bands A-H. The main part of the project was to further characterise these mutants. The additional RNA bands migrated between genomic segments 1 and 7, and were not integral multiples c segment 5 length. Further characterisation by RNase T1 oligonucleotide mapping (Follett and Desselberger, 1983b) showed that band A of brv mutant D (Hundley et al., 1985) and band E of brv mutant A4 (this thesis) consisted of segment 5-related sequences. The brv mutants D, A4, B4 and B5 were not replication-defective as they could be passaged through multiple rounds of plaque-to-plaque purification without requiring parent virus (standard brv). Reduction in the degree of genome transcription and replication, plaque formation, suppression of host cell protein synthesis and development of CPE was observed in cells infected with the brv mutants A4, B4 and B5 when compared to standard brv. However, brv mutant D was similar to standard brv in all these parameters. Standard brv and the brv mutants grew to different titres at 3