Porcine Reproductive and Respiratory Syndrome Virus Modulates the Switch of Macrophage Polarization from M1 to M2 by Upregulating MoDC-Released sCD83

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV), the most economically important infectious disease of pigs, elicits poor innate and adaptive immune responses. Soluble CD83 (sCD83), a secretion from various immune cell populations, especially MoDCs, is involved in negatively regulating the immune response. We speculate sCD83 may be a critical factor in the process of PRRSV-coordinated macrophage polarization. In this study, we found that PAMs co-cultured with PRRSV-infected MoDCs inhibited the M1 macrophage while enhancing the M2 macrophage. This was accompanied by a decrease in the pro-inflammatory cytokine TNF-α and iNOS and an increase in the anti-inflammatory cytokine IL-10 and Arg1. Meanwhile, sCD83 incubation causes the same specific effects lead to a switch in macrophage from M1 to M2. Neutralization of sCD83 removes the inhibitory effects of PRRSV on PAMs. Using reverse genetics, we generated recombinant PRRSVs with mutations in N protein, nsp1α, and nsp10 (knockout sCD83-concerned key amino acid site). Four mutant viruses lost the suppression of M1 macrophage markers, in contrast to the restriction of the upregulation of M2 macrophage markers. These findings suggest that PRRSV modulates the switch of macrophage polarization from M1 to M2 by upregulating the MoDC-induced secretion of CD83, providing new insights into the mechanism by which PRRSV regulates host immunity.

Highly pathogenic PRRSV upregulates IL-13 production through nonstructural protein 9–mediated inhibition of N6-methyladenosine demethylase FTO

“…It causes reproductive disorders and breathing difficulties in pigs, generating huge economic loss to the swine industry ( 2 ). The PRRSV genome contains 11 ORFs, encoding eight structural proteins and 16 nonstructural proteins (nsp), each possessing diverse functions in various steps of infection, replication, virulence, and virus–host interactions ( 3 , 4 , 5 , 6 , 7 , 8 ). Immunosuppression after PRRSV infection may contribute to inefficient innate and acquired immune responses, modulating the expression and release of inflammatory and/or anti-inflammatory factors, upregulating immunosuppressive cytokines expression, and allowing the viruses to rapidly reproduce and cause disease ( 9 , 10 , 11 , 12 ).…”