Tylvalosin tartrate inhibits the replication stage of the porcine reproductive and respiratory syndrome virus life cycle.

The aetiological agent of porcine reproductive and respiratory syndrome, a deadly disease that affects pigs and seriously jeopardises the global swine industry, is a porcine reproductive and respiratory syndrome virus (PRRSV). Tylvalosin tartrate, which is a macrolide antibiotic, is the active ingredient in Aivlosin. In recent years, tylvalosin tartrate has widely been used to control porcine reproductive and respiratory syndrome in swine herds in China. However, whether tylvalosin tartrate has exerts anti-PRRSV effects remains controversial. In the present study, tylvalosin tartrate exhibited no effect on PRRSV susceptibility but suppressed the replication of PRRSV and the activity of infecting Marc-145 cells. Next, the relationship between the replication cycle of PRRSV and the activity of tylvalosin tartrate was further assessed. Tylvalosin tartrate did not affect the attachment and release stages of PRRSV or act during the internalisation stage of the virus in HuN4; however, contrasting effects were noted for strains CH-1a and SDVD-HN21. Tylvalosin tartrate acted on the replication stage of PRRSV and was not strain-specific in the replication stage of the PRRSV life cycle. The study findings provide an initial clarification of the inhibitory effects of tylvalosin tartrate on PRRSV, providing new insights into the treatment of PRRS.