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Title: Oral fluids as a live-animal sample for evaluating cross-reactivity and cross-protection following intranasal influenza A virus vaccination in pigs

Author
item Hughes, Holly
item Vincent, Amy
item Brockmeier, Susan
item GAUGER, PHILLIP - Iowa State University
item PENA, LINDOMAR - University Of Maryland
item SANTOS, JEFFERSON - University Of Maryland
item Braucher, Douglas
item PEREZ, DANIEL - University Of Maryland
item Loving, Crystal

Submitted to: Clinical and Vaccine Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2015
Publication Date: 10/1/2015
Citation: Hughes, H.R., Vincent, A.L., Brockmeier, S.L., Gauger, P.C., Pena, L., Santos, J., Braucher, D.R., Perez, D.R., Loving, C.L. 2015. Oral fluids as a live-animal sample source for evaluating cross-reactivity and cross-protection following intranasal influenza A virus vaccination in pigs. Clinical and Vaccine Immunology. 22(10):1109-1120.

Interpretive Summary: In North American swine herd populations there are numerous different influenza A viruses (IAV) currently circulating, making vaccine development difficult due to the inability to formulate a vaccine that provides protection against multiple IAV. Live-attenuated influenza virus (LAIV) vaccines provide better protection against multiple IAV than commercially available vaccines, making LAIV a candidate for a next-generation swine IAV vaccine. However, there is no standardized laboratory test to predict protection from different IAV following LAIV vaccination. IAV-specific antibody in blood has been the gold standard correlate of protection following IAV vaccination. LAIV vaccines are administered in the nose and do not induce high levels of antibody in the blood; however, antibody can be measured in nasal secretions and saliva. We evaluated the use of saliva and nasal secretions as a live-animal sample source to predict broad protection from multiple IAV following LAIV vaccination or live-virus exposure in pigs and compared these to traditional laboratory tests using blood. Both live-virus exposure and LAIV vaccination provided broad protection from two different IAV. IAV-specific antibody was detected in nasal secretions and saliva samples. Antibody in saliva from pigs exposed to live-virus was associated with broad protection from different IAV; however, saliva from LAIV vaccinated pigs did not associate with protection due to lower amounts of antibody. These data suggest that saliva from pigs exposed to live virus could be used to assess protection from IAV and guide the industry in making vaccine strain selection decisions.

Technical Abstract: In North American swine there are numerous antigenically distinct influenza A virus (IAV) H1 subtypes currently circulating, making vaccine development difficult due to the inability to formulate a vaccine that provides broad cross-protection. Live-attenuated influenza virus (LAIV) vaccines provide better cross-protection than current vaccines making LAIV a candidate for a next-generation swine IAV vaccine. However, there is no standardized assay to predict cross-protection following LAIV vaccination, and cross-protection data is somewhat limited. Hemagglutination-inhibiting (HI) antibody in serum has been the gold standard correlate of protection following IAV vaccination. LAIV vaccination does not induce a robust serum HI antibody titer; however, a local mucosal antibody response is elicited. Here, we evaluated the use of oral fluids (OF) and nasal wash (NW) as a live-animal sample source in an ELISA to predict cross-protection following LAIV vaccination or live-virus exposure in pigs, compared to traditional serology. Both live-virus exposure and LAIV vaccination provided heterologous protection, though protection was greatest against more antigenically related virus. IAV-specific IgA was detected in NW and OF samples and was cross-reactive against IAV from each H1 phylogenetic cluster. Endpoint titers of cross-reactive IgA in OF from pigs exposed to live-virus was associated with heterologous protection; however, this association was not observed using OF from LAIV vaccinated pigs due lower immunogenicity of the LAIV vaccine. These data suggest that OF from pigs exposed to wild-type IAV, with surface genes that match the LAIV seed strain, could be used in an ELISA to assess protective efficacy of swine LAIV vaccines.