Evaluation of lentiviral genetic mutations

Abstract

The small ruminant lentiviruses (SRLV) have the potential to change genetically and switch from an host to another. In this paper, we studied genetic evaluation that accompanied infestation and adaptation of SRLVs in hybrids. Three blood samples, one year apart, were taken from Hybrids living in two sites in French Alps. Antibodies to SRLV were sought in serum using a commercial ELISA to p28 antigen, and ficoll-isolated monocytes were cultured in macrophage differentiation medium to detect active viral infection. DNA extracted from non-cultured monocytes was amplified by PCR and Nested PCR. Amplicons were sequenced and analysed. The Nested PCR technique specifically amplified a 513 nucleotide fragment of the gag gene including the 3' portion. The sequences alignments shows two types of genetic mutations: deletion and replacement. The sequences obtained from the samples taken in first year showed a diversity comparable to that observed in the reference virus. After one year of cohabitation, the sequences of the virus showed very important genetic mutations including a deletion of 6 nucleotides. Finally, after 3 years of cohabitation, the virus sequences included more genetic mutations. The percentages of discrepancies between the proviral sequences obtained and that of reference virus were on average from 6.1 to 8.8% in nucleotides. Compared with proviral sequences obtained in first year, the average percentages of divergence was 2.6% in nucleotides in second year and 2.9% in third year. The average of the internal divergence percentages was 0.56 - 2.79%. These differences were also shown by the phylogenetic tree.