H5N1 avian influenza virus without 80–84 amino acid deletion at the NS1 protein hijacks the innate immune system of dendritic cells for an enhanced mammalian pathogenicity

Abstract

NS gene is generally considered to be related to the virulence of highly pathogenic avian influenza virus (AIV). In recent years, the strains with five amino acids added to the 80-84 positions of the NS1 protein have become prevalent in H5N1 subtype AIVs isolated from mammals. However, the pathogenicity and mechanism of this pattern in mammals remain unclear. In this study, H5N1 subtype AIVs without 80-84 amino acids of the NS1 protein (rNS Δ5aa ) and a mutant virus (rNS 5aa-R ) with no deletion of 80-84 amino acids of the NS1 protein were used to determine the pathogenicity in mice. Our results showed that rNS 5aa-R possessed an enhanced pathogenicity compared with rNS Δ5aa in vivo and in vitro, which was accompanied by high expression of IL-6, MX1 and CXCL10 in murine lungs. Furthermore, we found that rNS 5aa-R increased the infection ability to dendritic cells (DCs). Besides, rNS 5aa-R enhanced the expression of phenotypic markers (CD80, CD86, CD40 and MHCII), activation marker CD69, inflammatory cytokines (IL-6, TNF-α and IL-10) and antagonized interferon (IFN-α) of DCs, in comparison to rNS Δ5aa . Moreover, rNS 5aa-R induced DCs to quickly migrate into nearby cervical lymph nodes by highly upregulating CCR7, and CD86 showed a high expression on the migrated DCs. We also found that rNS 5aa-Rinfected DCs significantly promoted the allogeneic CD4 + T-cell proliferation. These findings suggested that rNS 5aa-R strongly induced the innate immune response compared with the rNS Δ5aa , which is conducive to activate a wide immune response, resulting in a strong cytokine storm and causing an enhanced pathogenicity of H5N1 subtype AIVs in mammals.

139D in NS1 Contributes to the Virulence of H5N6 Influenza Virus in Mice

“…In addition, NS1 aids the shutdown of the host cellular machinery, promotes viral-only gene expression, and increases the infected cell survivability by activating PI3K and regulating the apoptotic response (37)(38)(39)(40)(41). It has been reported that the deletion of 80-84 amino acids in NS1 increases the pathogenic ability of H5N1 by hijacking the innate immune system of dendritic cells in vivo (42). Our study revealed that both JX and XGD had five amino acid deletions in NS1.…”

Emergence and Characterization of a Novel Reassortant Canine Influenza Virus Isolated from Cats

“…Of note, despite the limitation of current report that only one isolate was identified so far, the fact that the human NS gene was included in this reassortant is significant. The NS gene had been shown to play a significant role in the virulence [37,38] by modulating cytokines [39], specifically as an antagonist to alpha-interferon. Whether this novel virus, FIV-HWT-2017, has increased virulence by interfering the host immune response remains to be determined.…”

PA‐X protein assists H9N2 subtype avian influenza virus in escaping immune response of mucosal dendritic cells

“…DCs were infected with viruses at a dose of 0.5 MOI for 48 h, and the supernatant was aliquoted and stored at −70°C. Cytokines including IL‐6, TNF‐α, and IL‐10 in the supernatant of DCs were detected by ELISA kit (Multisciences, Hangzhou, China) according to the instructions (S. Chen et al., 2021).…”