The Relationship Between Macrophage Polarization And Classical Swine Fever Virus Infectivity

Classical swine fever(CSF)remains one of the most important viral diseases of swine and has a significant impact on the pig industry worldwide.The classical swine fever virus(CSFV),is etiological agent of CSF,and mononuclear cells and alveolar macrophages are the main cell types targeted by CSFV.Macrophages can be activated upon microenvironment alteration and cytokines stimulation and polarized into M1(classically activated macrophages)or M2(alternatively activated macrophages).However,the association between macrophage polarization and viral infection in pigs is still unclear.The aim of this experiment was to study the relationship between macrophage polarization and viral replication in pigs,which were the effect of the infection of CSFV on macrophage polarization and the effect of polarized macrophages on the replication of CSFV.Here,we isolated porcine alveolar macrophage(PAM)from porcine alveolar lavage fluid.The purity of isolated PAM can be achieved up to 90%,which was confirmed by indirect immunofluorescence assay(IFA).Subsequently,we established PAM polarization model.In this model,the resting state macrophages can be polarized into M1 or M2 subtypes by lipopolysaccharide(LPS)plus gamma interferon(IFN-γ)or interleukin-4(IL-4)stimulation,respectively.This model was proved effective by immunoblot assay with antibodies against IL-1 beta and Arg-1,Griess assay for Nitric Oxide levels and Arginase activity assay in vitro.Moreover,we found that polarization-related mRNA levels were up-regulated upon infection of CSFV Shimen strain and the mRNA level of M1 was higher than that of M2 subtype,indicating that CSFV infection can induce the M1 polarization of macrophage.More importantly,by using IFA with a monoclonal antibody against the CSFV E2 antigen,we found that LPS plus IFN-γ-induced M1 polarization of PAM inhibits CSFV replication at 24 to 72 hours postinfection.In summary,this study provides not only an important clue for studying the host immunity response toward CSFV,but also theoretical basis for new strategies for control,prevention and treatment of CSF based on macrophage polarization subtype.