Activation of activating Fc gamma receptors down-regulates the levels of interferon β, interferon γ and interferon λ1 in porcine alveolar macrophages during PRRSV infection

Porcine activating Fc gamma receptors (Fc gamma RI and Fc gamma RIII) have been cloned and characterized for many years. However, their roles in interferon (IFN) antiviral immune response to porcine reproductive and respiratory syndrome virus (PRRSV) infection have not yet been investigated extensively. In this study, PRRSV infection assay showed that PRRSV increased significantly the transcription of IFN-beta, IFN-gamma and IFN-lambda 1 in porcine alveolar macrophages (PAMs) in early infection and decreased significantly the transcription of IFN-beta, IFN-gamma and IFN-lambda 1 in PAMs in late infection. Activation assay showed that specific activation of Fc gamma RI or Fc gamma RIII in PAMs decreased significantly the transcription of IFN-beta, IFN-gamma and IFN-lambda 1 and increased significantly the transcription of transforming growth factor beta 1 (TGF-beta 1). PRRSV infection assay mediated by Fc gamma RI and Fc gamma RIII showed that specific activation of Fc gamma RI or Fc gamma RIII in PAMs during PRRSV infection decreased significantly the transcription of IFN-beta, IFN-gamma and IFN-lambda 1, but increased significantly the transcription of TGF-beta 1 and enhanced significantly viral replication. In conclusion, our studies suggested that activating Fc gamma R signaling inhibited the transcriptional levels of IFN-beta, IFN-gamma and IFN-lambda 1 in PAMs in response to PRRSV infection.