The genetic properties accompanied of "quasi-species" crossing of Small Ruminant LentiViruses (SRLVs)

Abstract

The env gene of Small Ruminant LentiViruses (SRLV) encodes a polypeptide precursor which after glycosylation is cleaved to give the two glycoproteins of the viral envelope: the transmembrane protein (TM) and the surface protein (SU). The passage and adaptation of SRLVs in new hosts is always accompanied by genetic mutations in the SU region of the env gene that determines the tropism of the virus by recognition of the cellular receptor. We studied the genetic properties of SRLVs accompanied of the "quasi-species" in Capra ibex. 16 Blood samples of Capra ibex were tested for presence of specific antibodies against SRLVs using a commercially available ELISA. Peripheral blood mononuclear cells (PBMC) isolated on Ficoll gradient were cultured in macrophage differentiation medium to obtain monocyte-derived macrophage (MDM) monolayers for virus isolation. DNAs from non cultured PBMC were used as templates for PCR and Nested PCR amplification of proviral genome. Nested PCR products (108 nt) were cloned and sequenced. Sequences were analysed using ClustalW software. The alignments of the SU region sequences show three important types of genetic mutations: deletion, addition and replacement nucleotides. We present data showing that the sequences of C. ibex SRLV isolates are closer to the prototypic CAEV-Co isolate. This might indicate a recent "quasi-species" infection of SRLV in C. ibex.