Ahmad Nazaktabar - Amol University of special modern technologies

Background and Aim:Picobirnavirus (PBV) is a bi-segmented dsRNA-virus living in the alimentary tract of human and various animal species as an opportunist enteropathogen. Because of high mutation rate, this virus is known as a quasi-species. In this study, the effect of nucleotide mutations on the structure of the RdRp gene of PBV was investigated wondering more detail of the biology of this high mutable virus in bovine population.Methods:PBV was detected in 5 of 485 samples collected from under 2 months old diarrheic calves from 14 provinces of Iran using PAGE assay. Positive samples were submitted to RT-PCR to detect the RdRp gene of PBV. Sequencing of one of PCR amplicons revealed distinctive overlapping peaks investigated to find the effect of nucleotide mutations in the sequence of deduced amino acids by Expresso tool.Results:43 nucleotides residues were mutated among 153 nucleotides (28%). 25 point mutations were silent. As well, no mutations were seen in the nucleotides encoding 19 amino acid residues (including D--S-D residues of motif A). Mutations of codons encoding 9 amino acid residues may lead to change their amino acids, according to probability rules. In one residue, each of its three coding letters were mutated, a deleterious mutation was probable because of forming the TAG stop codon.Conclusion:These results reveal that PBV lives as quasi-species in the intestine of bovine similar to swine as other reported and confirmed that despite the high mutation rate of the nucleotide sequence (28%), the amino acid sequence of its RdRp gene highly conserved.

Picobirnavirus, Structural analysis, RdRp, calves, Iran