RESUMEN
Six recombinant plasmids covering cDNA of porcine reproductive and respiratory syndrome virus BJ-4 were sequenced, respectively, and 23 point mutations were reverted with site-directed mutagenesis kit. The full-length cDNA clone pWSK-DCBA was assembled and re-sequenced. The capped viral genomic RNA was transcribed in vitro, mixed with liposome and transfected into MARC-145 cells, and an infectious virus (designated rV68) was rescued. The rescued virus was able to induce CPE typical of PRRSV on MARC-145 and stably propagated in vitro . Growth kinetics curve of the rV68 exhibited a delayed replication in MARC-145 cell, namely its peak titer time was 12h later than that of parental virus. However, there was no significant difference between the peak titers of the rescued and parental virus (P > 0.05). These results suggest that the full-length cDNA clone pWSK-DCBA of PRRSV BJ-4 is infectious, which provide a basis for further study on molecular pathogenicity and immunity, as well as developing novel vaccine of PRRSV.