Porcine CD74 is involved in the inflammatory response activated by nuclear factor kappa B during porcine circovirus type 2 (PCV-2) infection

Human CD74 induces a signalling cascade that results in the activation of nuclear factor kappa B (NF-kappa B); however, porcine CD74 has not been widely studied. In this study, we show that porcine CD74 is mainly expressed in cells of the macrophage lineage and can be induced by lipopolysaccharide (LPS), polyinosinic acid-polycytidylic acid [Poly(I:C)], and infection with porcine circovirus type 2 (PCV2) in vitro. In addition, we confirmed that porcine CD74 can activate NF-kappa B by promoting I kappa B alpha degradation and nuclear translocation of p65. Furthermore, the transcription of NF-kappa B-regulated genes [Interleukin-6 (IL-6), Interleukin-8 (IL-8), and COX-2] was upregulated in response to the overexpression of porcine CD74. In general, porcine CD74 significantly enhanced the inflammatory response by regulating the NF-kappa B signalling pathway during PCV2 infection, which suggests that porcine CD74 may be implicated in the pathogenesis of PCV2 infection.