Investigation On The Role Of The Immunoproteasome In Pathogenesis During HP-PRRSV Infection

Porcine reproductive and respiratory syndrome(PRRS),commonly known as blue ear disease is caused by porcine reproductive and respiratory syndrome virus(PRRSV),is a highly contagious disease with histopathological changes characterized by interstitial pneumonia and thymus atrophy.The infection of highly pathogenic porcine reproductive and respiratory syndrome virus(HP-PRRSV)on pigs causes severe pathological damage by inducing immunosuppression.However,the mechanism for inducing immunosuppression by HP-PRRSV is still unclear.Several studies found that,HP-PRRSV evaded CTLs responses by its Nsp1? and Nsp4 interacted with both chains of SLA-I HC and ?2M,respectively.The elimination of infected cells by CTLs occurs through interactions between TCRs and pathogen-derived antigenic peptide-MHC I complexes.However,it remains to be determined whether the immunoproteasome(i-proteasomes)complex,which is an important component of the antigen delivery pathway by mediating peptide production,is also affected by viral infection.I-proteasome,which is one of specified constitutive proteasome,could be induced under inflammatory conditions such as IFN-? or TNF-? stimulation.Studies have also confirmed that the lung is a vulnerable site for PRRSV,which induces chronic inflammation that is characterized by interstitial pneumonia lesions and high expression of the inflammatory cytokines IFN-?and TNF-?.Therefore,in this study,we investigated how i-proteasome was induced within the lung during HP-PRRSV infection,and after induction,what roles of i-proteasome play in HP-PRRSV induced immunosuppression?First,RNA sequence was applied in this study to determine the expression patterns of i-proteasomes in AMs with IFN-?/LPS stimulation.Results revealed that the expression of LMP2,LMP7 and MECL-1 was markedly increased in IFN-?/LPS-stimulated AMs.Based on the evolutionary analysis of these genes sequences,we found that,conservation of the beta types of these genes suggested their role in peptide bond hydrolysis,and induction of the beta types of these genes with Poly I:C stimulation suggested their role in antiviral immune response,both of which contribute to immune responses and inflammation.Third,we systematically analyzed the expression of i-proteasome in vivo in the porcine lung under normal and inflammatory conditions.AMs were shown to readily express low levels of i-proteasome subunits,while i-proteasome expression could also be detected in other lung parenchymal cells including alveolar type ? and ? cells and bronchial epithelial cells during inflammatory conditions.In vitro assays confirmed that i-proteasome expression is markedly increased in IFN-y-stimulated AMs.And HP-PRRSV infection promoted i-proteasome expression in AMs during the early stage of infection,and this was independent of IFN-?;expression was attenuated during the later stage of infection.This suggests that HP-PRRSV can interfere with antigen presentation by affecting the production of i-proteasome.Finally,in vitro primary AMs with both PRRSV infection and IFN-? stimulation demonstrated that HP-PRRSV regulated IFN-?-mediated expression of i-proteasome at mRNA and protein levels via affecting the expression of JAK/STAT in the IFN-? signaling pathway and genes involved in the regulation of the JAK/STAT pathway during HP-PRRSV infection.In conclusion,data obtained in this study facilitate better understanding of the role of i-proteasomes in respiratory diseases in pigs and provide insight into the role of i-proteasome in HP-PRRSV-induced immunosuppression,which will be a valuable reference for the development of therapeutic agents for antiviral adaptive immune responses against intracellular pathogen infection.