| Porcine reproductive and respiratory syndrome virus (PRRSV) is the causative agent of PRRS. It caused highly contagious disease in swine characterized by reproductive disorder in sows and gilts, respiratory diseases and death in piglets, resulting in great economic losses to pig industry. The full-length genome of PRRSV 08HuN strain was sequenced in this article. Comparison with the other three highly pathogenic PRRSV variants revealed 14 point mutations of amine acid and 42 silent mutations in the genome of 08HuN strain, providing useful information on the virulence of highly pathogenic PRRSV strains.In the analysis of silent mutations, we found that there is a codon preference for low-frequency codons to high-frequency codons in the 08HuN strain. To our knowledge, this is the first proposal at home and abroad that silent mutations maybe a contributing factor to the virulence difference of PRRSV virus.The findings also enrich the theory of PRRSV genetic variation. The establishment of full-length cDNA clone of PRRSV 08HuN strain by utilizing reverse genetic manipulation technology. Nonsynonymous mutational sites within full-length cDNA clone were corrected by enzyme digestion and splice. The successful construction of full-length cDNA clone provided fundamental materials for establishment of infectious clone of 08HuN strain and further research on virulence factor and pathogenesis in molecular level of 08HuN strain.According to the sequencing results of six fragments of the genome of porcine reproductive and respiratory syndrome virus (PRRSV) 08HuN strain,fragment A, E and F all contained correct clone molecules which meet the requirements of further clone, while several nonsynonymous mutational sites within the fragment B, C and D were corrected by enzyme digestion and splice.The correct clone of fragment A, D and the recombinant corrected clone of fragment B, C and D were all subcloned in pVAXl vector. The correct clone of fragment F was subcloned in ppoly2/sfinot vector. PRRSV 08HuN strain full-length cDNA molecule was obtained by enzyme digestion and splice in order using the restriction enzyme cutting sites located in the overlapping region of six fragments. |
