Intestinal Epithelial Cells-Mediated Innate Immunity Inhibits HIV Infection

At present,sexual transmission has become the main way to spread HIV.Among them,the HIV infection rate of men who have sex with men(MSIM)increased year by year,and this group has become a high-risk population of HIV infection.Among MSM population,intestinal mucosa becomes one of the main portal HIV invading the host.As a rich source of activated or resting CD4+ T lymphocytes and macrophages in the lamina propria,gastrointestinal(GI)tract is also a major target site for HIV infection.After HIV infection,the intestinal immune system is rapidly damaged,causing rapid depletion of CD4+ T lymphocytes and the release of inflammatory factors from macrophages,diminished physiological functions of macrophages,microbial and its metabolic products translocation,and generalized chronic immune activation.Intestinal epithelial cells(IECs)are the most abundant cell types in the gut tissue and exert their barrier function through tight junctions.Importantly,IECs express pattern recognition receptors(PRRs),initiate innate immune responses and play an important role in the antiviral activity.The aim of this study is to investigate the innate immune mechanism of IECs involved in anti-HIV infection/replication.1.TLR3 signaling of IECs induces IFNsAs an important PRR,TLR3 can effectively monitor virus infection and replication.TLR3 recognizes double-stranded RNA(dsRNA)and initiates innate immune responses.In this study,we used dsRNA analogue(Poly I:C)to specifically activate TLR3 signaling pathway of IECs to study its induction and regulation of Interferon(IFN).The results show that IECs express TLR3,TLR7,TLR8 and TLR9 associated with HIV recognition.Only TLR3 activation significantly induced the expression of IFN-P and IFN-?,respectively,using agonists of the respective receptors,and the TLR3-mediated IFN-induced expression was dose and time dependent.Its molecular mechanism is upregulation of Interferon regulatory factor 3(IRF3)and IRF7,activation of downstream signaling pathways,regulation of type ? and type ? IFN expression.2.IECs-isolated exosomes carry the antiviral ISGs and miRNAsOur results show that activation of the TLR3 signaling pathway of IECs can induce a variety of antiviral factors,including Interferon stimulating genes(ISGs):ISG15,ISG56,OAS-1,MxA,MxB,GBP5 and Viperin And anti-HIV-related microRNAs(miRNA-17,miRNA-20,miRNA-28,miRNA-29a,miRNA-29b,miRNA-29c and miRNA-125b).These antiviral factors can be wrapped in exosomes secreted by IECs and mediated antiviral activity.3.TLR3 signaling of IECs inhibits HIV infection of macrophagesIntestinal mucosa lamina propria is rich in macrophages,HIV is an important target cell.Since macrophages in the gut express high levels of CCR5 and show high susceptibility to HIV,we used macrophages as a model of HIV in vitro infection and conducted antiviral experimental studies.Experimental results show that,TLR3 activated IECs culture supernatant can significantly inhibit HIV replication in macrophages.Studies on its mechanism show that neutralizing antibodies against IFN-P and IFN-? receptors counteract the SN-mediated anti-HIV effect;treatment of macrophages with SN can induce macrophage production more ISGs and HIV-specific restriction factors including ISG15,ISG56,MxA,MxB,OAS-1,OAS-2,Tetherin,A3F,A3G and GBP5.In addition,exosomes secreted by IECs that contain multiple antiviral agents are upregulated by macrophages and are also involved in SN-mediated anti-HIV effects.4.TLR3 signaling of IECs induces CC chemokinesTLR3-activated IECs express CC chemokines(MIP-1?,MIP-1? and RANTES)that are the CCR5 natural ligands and competitively bind to the HIV co-receptor CCR5 and reduce the infectivity of HIV on macrophages.The results showed that pretreatment of macrophages with IECs SN activated by TLR3 significantly reduced the expression of strong-stop DNA in the first round of replication of macrophages,indicating that CC chemokines expressed by TLR3-activated IECs could inhibit HIV replication of macrophages at the entry level.