Genetic Features of The M Gene of The “Blue Ear” Causing Virus in Vietnam and Comparative Analysis with The Strains of Chinese and Global Origin

Abstract

The entire M (membrane) gene of 525 bp of a porcine reproductive and respiratory syndrome virus  isolate collected from a pig in Quang Nam province (Vietnam), designated as TXMT1(VN) was obtained and completely sequenced. The nucleotide, amino acid of the M sequence of TXMT1 was used to analyze for identity/homology between this isolate and a number of Chinese (isolated during 2006-2008) and global strains. The TXMT1 (Vietnam) was identified as a strain of porcine reproductive and respiratory syndrome virus (PRRSV), type II (North America sublineage), having very high rate of identity for nucleotide (99-100%) and homology for amino acid (99-100%) to the Chinese, low rate (94% nucleotide; 96% amino acid) to VR2332; and lower rate (69% nucleotide; 79% amino acid) to  Lelystad strain of PRRSV. The TXMT1 has only 2-3 nucleotides different from the Chinese, whilst 28 nucleotides to the classical VR2332 (type II, North America sublineage) and many to the strains of the European sublineage (type I). The variation of V(valine)/I(isoleucine) at the position 24 in the polypeptide M is a characteristic marker between the TXMT1 and the other PRRSV of North American and European sublineages. Characterization of the M gene revealed that the TXMT1 has high rate of gentics variation, probably belongs to the same origin as the PRRSV in China, suggesting that this highly virulent agent may be transmitted from China