Isolation and molecular characterization of GP5 glycoprotein gene of Betaarterivirus suid 2 from Mizoram, India.

Porcine reproductive and respiratory syndrome (PRRS) is a serious swine disease causing great economic impact worldwide. The emergence of highly pathogenic strains in Asian countries is associated with large scale mortality in all age groups of pigs besides the classical presentation of severe respiratory distress, pneumonia, and a series of reproductive disorders in sows, like late-term abortion, premature farrowing, and an increased number of stillborn piglets. The present study was designed with the aim of isolation and characterization of the Betaarterivirus suid 2 from outbreaks in Mizoram in primary porcine alveolar macrophage and subsequently characterized the GP5 gene sequence of the isolate in terms of phylogenetic analysis and deduce amino acid sequence comparison. Virus propagation was performed in the porcine alveolar macrophage (PAM) primary cell culture and confirmed by immunoperoxidase test, FAT, and nested RT-PCR. The full-length GP5 gene (603nt) was amplified from the isolate and subsequently cloned and sequenced (MN928985). Phylogenetic analysis and sequence comparison of the present isolate was found to have similarity 98.7-98.8% with Myanmar HP-PRRS strains, 98-98.5% with Vietnam strains, 98.2-98.3% with China strains, indicating a close lineage with highly pathogenic PRRS strains. In deduced amino acid sequence analysis, one mutation was found in the primary neutralizing epitope (PNE) at position 39L → I39 and one more mutation was also found in the decoy epitope (DCE) at position 30 N → D30. The amino acid at this position is an N-linked glycosylation site, and mutation of the N-linked glycosylation is an immune escaped strategy adopted by this virus causing a persistent infection in the natural host.