Dual R108K and G189D Mutations in the NS1 Protein of A/H1N1 Influenza Virus Counteract Host Innate Immune Responses

Abstract

Influenza A viruses (IAV) modulate host antiviral responses to promote growth and pathogenicity. Here, we examined the multifunctional IAV nonstructural protein 1 (NS1) of influenza A virus to better understand factors that contribute to viral replication efficiency or pathogenicity. In 2009, a pandemic H1N1 IAV (A/California/07/2009 pH1N1) emerged in the human population from swine. Seasonal variants of this virus are still circulating in humans. Here, we compared the sequence of a seasonal variant of this H1N1 influenza virus (A/Urumqi/XJ49/2018(H1N1), first isolated in 2018) with the pandemic strain A/California/07/2009. The 2018 virus harbored amino acid mutations (I123V and N205S) in important functional sites; however, 108R and 189G were highly conserved between A/California/07/2009 and the 2018 variant. To better understand interactions between influenza viruses and the human innate immune system, we generated and rescued seasonal 2009 H1N1 IAV mutants expressing an NS1 protein harboring a dual mutation (R108K/G189D) at these conserved residues and then analyzed its biological characteristics. We found that the mutated NS1 protein exhibited systematic and selective inhibition of cytokine responses via a mechanism that may not involve binding to cleavage and polyadenylation specificity factor 30 (CPSF30). These results highlight the complexity underlying host–influenza NS1 protein interactions.

Human genes with codon usage bias similar to that of the nonstructural protein 1 gene of influenza A viruses are conjointly involved in the infectious pathogenesis of influenza A viruses

“…However, (Gao et al 2013 ; Koopmans et al 2004 ; Marinova-Petkova et al 2017 ; Meineke et al 2019 ; Skowronski et al 2006 ; Song and Qin 2020 ; Terebuh et al 2018 ; Tong et al 2018 ; Tweed et al 2004 ; Um et al 2021 ; Westenius et al 2018 ) current management of human influenza A is limited to vaccines and antiviral treatments targeting viral proteins (Uyeki et al 2019 ). Due to their rapid mutation capacity, IAVs have a strong evasion mechanism to the host immune system (Chang et al 2020 ; Huang et al 2021 ; Li et al 2012 ; Peacock et al 2017 ; Peng et al 2014 ; Sitaras et al 2014 ), thus reducing the effectiveness of antivirals targeting viral proteins. To counteract these problems, the development of drugs targeting the virus-host interactions that promote IAV infection and replication is necessary.…”

Virus versus host: influenza A virus circumvents the immune responses

“…This characteristic mutation can target antiviral drugs and attenuate vaccine development. In addition, the double mutation (R108K/G189D) in the NS1 protein suggested a systematic and selective inhibition of cytokine responses to counteract the innate immune response ( Huang et al, 2021 ). At the same time, the conserved FTEE motif (aa150-153) of NS1 can subvert the RIG-I, TLR3, and TLR7 pathways in combination with TRAF3 E3 ubiquitin ligase to produce type I IFN ( Lin et al, 2021 ).…”