Porcine Respiratory and Reproductive Syndrome Virus (PRRSV): Infection of Piglets |Biomedgrid

The porcine respiratory and reproduction syndrome virus (PRRSV) forms small, enveloped particles (50-65 nm in diameter), which contain a relatively large (approximately 15 kb long) single strand RNA genome. More precisely, the viral RNA (vRNA) is a positive-sense, single-stranded molecule with a terminal cap at its 5´-end and a poly-A repeat at the 3´sd-end. The vRNA is copied as whole by means of a full-length complementary (negative sense) intermediate strand. The resulting minus sense subgenomic (sg) RNA is then used as template for the synthesis of the additional vRNAs. The enzyme involved is the RNA-dependent RNA polymerase (RdRp), also termed non-structural protein 9 (nsp9), encoded by the virus. The vRNA contains 2 long open reading frames (namely ORF1a and ORF1b); all the 14 non-structural proteins (nsps) are formed by cleavage of 2 large polyproteins, the coding sequence of which streches nearly over 75% of the total genome length [1]. The ORF1b sequence encodes 7 structural proteins (M, N and E) out of which 4 are glycoproteins, namely GP2a, GP3, GP4, GP5. Based on the structure of vRNA decribed above, PRRSV has been classified into family Arteriviridae, along with equine arteriitis virus and/ or the lactate dehydrogenase elevating virus of mice. Based on the described structure of vRNA, the PRRSV has been classified into family Arteriviridae, along with equine arteriitis virus and/or lactate dehydrogenase elevating virus of mice.