key: cord-0891531-721zftd1
authors: Rathnasinghe, Raveen; Salvatore, Mirella; Zheng, Hongyong; Jangra, Sonia; Kehrer, Thomas; Mena, Ignacio; Schotsaert, Michael; Muster, Thomas; Palese, Peter; García-Sastre, Adolfo
title: Prophylactic protection against respiratory viruses conferred by a prototype live attenuated influenza virus vaccine.
date: 2021-08-13
journal: Res Sq
DOI: 10.21203/rs.3.rs-668116/v1
sha: 7f75a743c494a6c48f7e06abb406ae20a21e512b
doc_id: 891531
cord_uid: 721zftd1

The influenza A non-structural protein 1 (NS1) is known for its ability to hinder the synthesis of type I interferon (IFN) during viral infection. Influenza viruses lacking NS1 (ΔNS1) are under clinical development as live attenuated human influenza virus vaccines and induce potent influenza virus-specific humoral and cellular adaptive immune responses. Attenuation of ΔNS1 influenza viruses is due to their high IFN inducing properties, that limit their replication in vivo. This study demonstrates that pre-treatment with a ΔNS1 virus results in an immediate antiviral state which prevents subsequent replication of homologous and heterologous viruses, preventing disease from virus respiratory pathogens, including SARS-CoV-2. Our studies suggest that ΔNS1 influenza viruses could be used for the prophylaxis of influenza, SARS-CoV-2 and other hum an respiratory viral infections, and that an influenza virus vaccine based on ΔNS1 live attenuated viruses would confer broad protection against influenza virus infection from the moment of administration, first by non-specific innate immune induction, followed by specific adaptive immunity.

The influenza A non-structural protein 1 (NS1) is known for its ability to hinder the sy ere intranasally administered to A2G mice 24 hours prior to hvPR8 challenge. As sho 156 wn in Figure 2D , the ED50 of the ΔNS1 virus which conferred protection in A2G mice 157 against hvPR8-induced death was approximately 10 3 PFU. ΔNS1 mediated protection from hvPR8 is Mx1-mediated. 168 As the Mx1 protein is one of the most potent IFN inducible gene products with anti-inf luenza virus activity in mice, it is quite possible that the ΔNS1-mediated protection se 170 en in A2G mice is Mx1-mediated. To test this hypothesis, we compared the antiviral a 171 ctivity of ΔNS1 in A2G mice and in C57BL/6 mice. C57BL/6 mice harbour a non-funct 172 ional Mx1 gene due to a known deletion 26 and were used as a back-cross genetic pla ble for a 10-fold reduction in the NA protein levels as well as a one-log reduction in vi 206 ral titers within a multicycle growth curve 30 . The latter D2 strain has also been shown 207 to be highly attenuated in mice with a LD50 of more than 10 6 PFU upon intranasal ad 208 ministration 31 . Identical doses (2.5x10 5 PFU) of D2 or ΔNS1 viruses were intranasally 209 administered to A2G mice four hours prior to challenge with 5x10 6 PFU of hvPR8. Alt 210 hough a prolonged survival was seen in one of the animals who received D2, pre-tre 211 atment with D2 was ineffective in protecting A2G mice from hvPR98 virus-induced di 212 sease and death ( Figure 4 ). 214 Given the fact, that the antiviral effects against hvPR8 mediated by ΔNS1 viral are fa 215 cilitated by an IFN mediated mechanism (Mx1 gene induction), we speculated that Δ 216 NS1 treatment should protect mice from infections by other IFN sensitive viruses. Se 217 ndai virus was used in this study due to its pneumotropic nature and sensitivity to IFN in Mx1 deficient mice 32, 33 . As seen in Figure Figure 6C ).

The NS1 protein of the influenza A virus has been shown to possess IFN antagonist 245 activity whereby it is able to dampen the host innate immune response to provide a fa 246 vourable environment for the virus to replicate. It has been demonstrated to be highly 

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Medicine and lic 636 ensed to Vivaldi Biosciences concerning the use of NS1 deficient viruses as human v 637 accines and to BI Vetmedica on the use of NS1 deficient viruses as veterinarian vacc 638 ines. The García-Sastre Laboratory has received research support from Pfizer

ImmunityBio and Nanocomposix; and A.G.-S. has co 641 nsulting agreements for the following companies involving cash and/or stock: Vivaldi 642

The rest of the authors h 643 ave no conflicts to declare. and were used for RT-PCR reactions using Mx1 specific primers

Sex matched 6 we 695 eks old groups C57BL/6-A2G-Mx1 mice or C57BL/6-wild-type mice were either intran 696 asally pre-treated with PR8-ΔNS1 (5x10 6 PFU; n=5 per group), sterile PBS (n=5) 12 h 697 ours before a lethal challenge of hvPR8

Survival of C57Bl/6-A2G-M 699 x1 mice. (D). Morbidity of C57Bl/6-wild-type mice

The authors acknowledge members of AG-S and PP laboratories for their critical disc 424 ussions. Technical assistance for the study was provided by Louis Ngyenvu and Rich

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