CategorySwine Health - General Disease
Date Full Report Received10/13/2017
Date Abstract Report Received10/13/2017
InvestigationInstitution: NADC, USDA-ARS
Primary Investigator: Amy Vincent
Co-Investigators: Phil Gauger
Funded ByNational Pork Board
Influenza A virus (IAV) is a highly diverse and contagious swine pathogen that causes financial losses to the US swine industry through decreased production, increased vaccine and treatment costs, and often leads to elevated mortality rates due to an increase in secondary bacterial pneumonia. Additionally, IAV in swine (IAV-S) is a zoonotic pathogen with public health concerns. Therefore, veterinarians and pork producers have a major stake in finding alternative methods that can be implemented to reduce the negative impact of IAV in their herds and decrease the diverse ecology of influenza viruses circulating in swine. Whole inactivated virus vaccines (WIV) played an important role in the prevention and control of IAV-S in previous years. However, repeated failures of current WIV products and the overall lack of efficacious IAV vaccines have become extremely frustrating for producers, and the choices are limited in the types of vaccines currently licensed for use in swine, although custom made WIV vaccines are available. A major cause of vaccine failure on farms is presumed to be the diversity of strains that co-circulate in swine. Not only are there multiple subtypes and lineages of IAV co-circulating, but each lineage is prone to rapid mutation and evolution, which creates mismatches to strains used in the vaccines. Although protection against infection with identical or very similar IAV are adequate under ideal conditions, WIV vaccines do not prevent infection with mismatched, antigenically diverse strains of IAV. The goal of our proposal was to evaluate novel vaccination protocols to improve cross-protection induced by WIV vaccines by alternating the administration of relevant IAV antigens from the H1 subtype (heterologous prime-boost), in comparison to giving multiple viruses together in one vaccine. A similar strategy was reported to be effective against H3 subtype viruses in Europe. We selected 3 commonly identified H1 IAV, viruses 1, 2, and 3, and tested 6 different vaccination scenarios, with vaccines containing either one or two viruses. However, the heterologous prime-boost strategy was not successful for the H1 viruses evaluated in our study. In fact, all groups vaccinated with only WIV exhibited greater respiratory disease than the unvaccinated challenge control pigs and were not protected from infection. The only group included in our study that had protection from disease and infection were the pigs that were infected with the live mismatched Virus 1, allowed to recover, vaccinated with a WIV with the mismatched Virus 2, followed by challenge with Virus 3. These results demonstrate the extreme difficulty in controlling H1 viruses from the U.S. with WIV and the potential advantage for modified live virus vaccines against IAV in swine.