Ea. Palombo et al., INTRA-SEASON AND INTER-SEASON GENETIC-VARIABILITY IN THE VP7 GENE OF SEROTYPE-1 (MONOTYPE-1A) ROTAVIRUS CLINICAL ISOLATES, Archives of virology, 130(1-2), 1993, pp. 57-69
Nucleotide sequence variation was detected in the VP 7 gene of serotyp
e 1 (monotype 1 a) rotavirus isolates collected from children admitted
to hospital in Melbourne with acute diarrhoea in 1990 and 199 1. Two
co-circulating electropherotypes were detected during the 1991 winter
epidemic. Using chemical cleavage of mismatches in heteroduplexes, the
genes encoding VP 7 were found to be genetically stable within each e
lectropherotype during the study period, although differences between
the two types were apparent. Direct nucleotide sequencing confirmed th
is finding. The two electropherotypes exhibited four nucleotide differ
ences in the VP 7 gene, only one of which resulted in a substitution i
n the deduced amino acid sequence. The degree of variation was more pr
onounced between the 1991 isolates and those from the previous winter,
with approximately 3% nucleotide sequence diversity between isolates
from both winters. The regions encoding the neutralization epitopes of
VP7 were conserved among all isolates. Comparison to the local protot
ype monotype 1 a strain, RV 4 (isolated from a child admitted to hospi
tal in Melbourne in 1981), implies that the 1990 and 1991 isolates hav
e diverged independently. This suggests that genetically distinct stra
ins emerge from a pool of related viruses to predominate in any given
year.