Molecular investigation and phylogenetic analysis of Jaagsiekte sheep retrovirus in naturally ovine pulmonary adenocarcinoma infected small ruminants in Andhra Pradesh, India

Ovine pulmonary adenocarcinoma (OPA) is a neoplastic contagious chronic disease infecting sheep and goats. Jaagsiekte sheep retrovirus (JSRV) is an aetiological agent causing OPA in small ruminants. JSRV was first isolated and whole genome sequenced in South Africa. The OPA clinical manifestation shows overproduction of lung fluid, dyspnoea and pyrexia with cough resembling pneumonia. Pathologically infected lung tissue shows greyish white, moist, enlarged, heavy and oedematous characteristics. The total RNA from OPA infected sheep and goat samples were isolated by Trizol method and converted to cDNA using poly dTP primers. The JSRV U3 gene region was amplified by PCR. The PCR products were resolved in 2% Agarose gel, sequenced by Sanger method. The sequence analysis and phylogenetic studies were performed using Mega 6 software. The genetic analysis revealed that most of the presently isolated sequences showed homology with UK strain (AF105220) whereas one sequence (SVU01) obtained from infected goat sample showed homology with South African strain (M80216). The genetic analysis discloses that presently sequenced JSRV U3 gene sequences have genetically deviated from the previously reported U3 gene sequences. The SVU01 gene sequence revealed 97% homology to SA Strain (M80216), 93% homology with UK strain (AF105220) and 91% homology with GVM05 strain (AB915881). The remaining three gene sequences (SVU02, SVU03 and SVU04) isolated from sheep showed 97% homology to UK strain (AF105220). Further phylogenetics analysis revealed SVU02 and SVU03 closely cluster together along with GVM05 genotype, SVU04 clustered with UK strain (AF105220) whereas SVU01 branched separately clustering with SA strain (M80216) respectively.