Inhibitory effects of recombinant porcine interferon-α on high- and low-virulence porcine reproductive and respiratory syndrome viruses

The inhibitory effects of recombinant porcine interferon alpha (rPoIFN-α) on the propagation of low-virulence PRRSV (lvPRRSV) in MARC-145 cells, and on the progress and severity of high virulence PRRSV (hvPRRSV)-induced infections in pigs, were determined. Pre-treatment of MARC-145 cells with increasing concentrations of rPoIFN-α prior to infection with lvPRRSV decreased the observed cytopathic effects (CPEs) in a concentration-dependent manner. Viral propagation and antibody response were temporarily delayed in swine treated with rPoIFN-α either at the same time as the hvPRRSV challenge was administered or post-challenge. Exposure of challenged animals to rPoIFN-α after the onset of disease symptoms alleviated associated hyperthermia. Variations in lymphocyte subsets indicated that rPoIFN-α treatment might alleviate damage to the immune system or enhance propagation of host cytotoxic T-lymphocytes when the treatment was applied simultaneously with the virus or 1 dpc, respectively.