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United States Department of Agriculture

Agricultural Research Service

Research Project: Novel Strategies for Generating Live-Attenuated Vaccine Viruses and Investigating Human-to-Pig Interspecies Transmission of Influenza a Virus Project Number: 3625-32000-108-19
Project Type: Specific Cooperative Agreement

Start Date: Sep 10, 2013
End Date: Sep 30, 2015

Objective:
Objective 1: The goal of this project is to prepare a multivalent live-attenuated infuenza vaccine (LAIV) against multiple antigenic/genetic clusters of swine influenza A virus and to test whether a strategy aimed at enhancing mucosal responses, particularly IgA, contribute to enhance protection against influenza in pigs. Objective 2: The goal of this project is to better understand the constellation of genes and/or molecular determinants of host range of human influenza A viruses in pigs.

Approach:
Objective 1: The project represents a natural continuation of the cooperation between NADC and UMCP that has resulted in the generation of a LAIV platform against swine influenza A virus (IAV). Specifically for this project we have selected a set of H1 and H3 antigens in order to produce a multivalent LAIV carrying the relevant contemporary surface antigens. The multivalent vaccine will be used in future vaccine-challenge studies in pigs against contemporary swine IAV. In addition, the LAIV will receive an additional live influenza component carrying a rearranged genome following the strategy recently described. In this case a rearranged virus (rFlu) will be produced carrying a segment 8 encoding a truncated NS1 gene and the IgA inducing peptide gene (IGIP). We hypothesize that a rFlu carrying the IGIP gene will lead to enhancement of mucosal neutralizing responses in pigs. We will demonstrate that such responses are more broadly neutralizing than using just the multivalent component alone or portions of it. Generation of the multivalent LAIV will follow the methods recently described using the PCR-based reverse genetics method. Viruses will be utilized in pig studies at NADC. Objective 2: We hypothesize since the late 1990’s that human IAV strains have evolved to be more prone to transmit to pigs and properties of swine IAV have evolved to be more prone to reassort and accept genes from human IAV. A key component of this process is reassortment and the constellation of genes that make such reassortant successful in pigs. Previous studies investigating reassortment have used several methods: blunt force, arbitrary genome selection, or co-infections. Typically, a blunt force approach uses mice to test each possible combination one at a time. This is not a cost efficient option for any system other than the mouse model and reveals nothing about competition and population dynamics. Other studies have arbitrarily selected a reassortant genome allowing only a partial view of what is possible. Finally, some studies have selected for viruses in co-infected cell cultures, which lacks the selective pressure of an in vivo system. We have recently developed a 15-plasmid transfection based inoculation (TBI) system to quickly and efficiently mimic a reassortment event between an H9N2 and pH1N1 in ferrets. This system allows us to test all possible reassortant viruses in animal models, under in vivo selective pressure. We propose to extend this system in pigs and determine constellation of human/swine influenza virus reassortants that are compatible with transmission pigs. We will then analyze adaptation mutations that are associated with reassortants shown to be infectious and transmissible in pigs.

Last Modified: 7/28/2014
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