Search

Abstract Background West Nile virus (WNV) is a rapidly spreading mosquito-borne virus accounted for neuroinvasive diseases. An insight into WNV-host factors interaction is necessary for development of therapeutic approaches against WNV infection. CD11b has key biological functions and been identified as a therapeutic target for several human diseases. The purpose of this study was to determine whether CD11b was implicated in WNV infection. Methods SH-SY5Y cells with and without MEK1/2 inhibitor U0126 or AKT inhibitor MK-2206 treatment were infected with WNV. CD11b mRNA levels were assessed by real-time PCR. WNV replication and expression of stress (ATF6 and CHOP), pro-inflammatory (TNF-α), and antiviral (IFN-α, IFN-β, and IFN-γ) factors were evaluated in WNV-infected SH-SY5Y cells with CD11b siRNA transfection. Cell viability was determined by MTS assay. Results CD11b mRNA expression was remarkably up-regulated by WNV in a time-dependent manner. U0126 but not MK-2206 treatment reduced the CD11b induction by WNV. CD11b knockdown significantly decreased WNV replication and protected the infected cells. CD11b knockdown markedly increased TNF-α, IFN-α, IFN-β, and IFN-γ mRNA expression induced by WNV. ATF6 mRNA expression was reduced upon CD11b knockdown following WNV infection. Conclusion These results demonstrate that CD11b is involved in maintaining WNV replication and modulating inflammatory as well as antiviral immune response, highlighting the potential of CD11b as a target for therapeutics for WNV infection.

Abstract T lymphopenia, occurring in the early phase of sepsis in response to systemic inflammation, is commonly associated with morbidity and mortality of septic infections. We have previously shown that a sufficient number of T cells is required to constrain Toll-like receptors (TLRs) mediated hyperinflammation. However, the underlying mechanisms remains unsolved. Herein, we unveil that CD4+ T cells engage with MHC II of macrophages to downregulate TLR pro-inflammatory signaling. We show further that the direct contact between CD4 molecule of CD4+ T cells or the ectodomain of CD4 (soluble CD4, sCD4), and MHC II of resident macrophages is necessary and sufficient to prevent TLR4 overactivation in LPS and cecal ligation puncture (CLP) sepsis. sCD4 serum concentrations increase after the onset of LPS sepsis, suggesting its compensatory inhibitive effects on hyperinflammation. sCD4 engagement enables the cytoplasmic domain of MHC II to recruit and activate STING and SHP2, which inhibits IRAK1/Erk and TRAF6/NF-κB activation required for TLR4 inflammation. Furthermore, sCD4 subverts pro-inflammatory plasma membrane anchorage of TLR4 by disruption of MHC II-TLR4 raft domains that promotes MHC II endocytosis. Finally, sCD4/MHCII reversal signaling specifically interferes with TLR4 but not TNFR hyperinflammation, and independent of the inhibitive signaling of CD40 ligand of CD4+ cells on macrophages. Therefore, a sufficient amount of soluble CD4 protein can prevent excessive inflammatory activation of macrophages via alternation of MHC II-TLR signaling complex, that might benefit for a new paradigm of preventive treatment of sepsis.

Tick-borne encephalitis virus (TBEV) belonging to arboviruses is a major member of zoonotic pathogens. TBEV infection causes severe human encephalitis without specific antiviral drugs. Due to its use of antiviral drug against a wide range of viruses, we investigated antiviral effect of ribavirin against TBEV in susceptible human cell lines A549 and SH-SY5Y. Ribavirin displayed minor cytotoxicity on multiple cell lines. Ribavirin obviously impaired TBEV replication and protected the infected cells from cytopathic effect. Importantly, ribavirin markedly inhibited TBEV propagation, as evidenced by impairment of TBEV production and viral RNA replication. Treatment with ribavirin (co-treatment and post-treatment) led to a dose-dependent reduction in TBEV titers as well as the viral RNA levels. Antiviral protein myxovirus resistance A mRNA expression was significantly up-regulated and signal transducer and activator of transcription 3 was activated in TBEV-infected A549 cells upon the ribavirin treatment. Induction of inflammatory cytokine tumor necrosis factor alpha by TBEV was decreased in A549 cells with the treatment of ribavirin, whereas interleukin 1 beta release appeared to be unaffected. These results suggest that ribavirin might represent a promising safe and effective antiviral drug against TBEV.