Demonstrated heterologous (cross-protective) cellular immune response against the 2009 A/H1N1 pandemic virus in pigs vaccinated with a human-like delta-cluster H1N1 virus. Humoral (serum antibody) and cellular (activated immune cells from whole blood) immune responses to inactivated swine influenza virus (SIV) vaccine were evaluated and compared by ARS scientists at the National Animal Disease Center in Ames, Iowa and their collaborators at Iowa State University as part of a Specific Cooperative Agreement. Pigs vaccinated with an inactivated (killed) SIV vaccine were shown to have strong cell mediated immune responses against the same virus and lower but significant cross-protective responses to the 2009 pandemic virus, especially in the lymphocytes involved with immune memory (e.g., CD4+CD8+ T cell subset). This is significant as the swine virus contained a distinctly different hemagglutinin (H1) protein molecule compared to the pandemic H1N1 virus. A standard antibody test detected humoral antibody responses only to the swine virus. In contrast, the cross-reactive cellular responses to the pandemic virus detected by flow cytometry suggested that the cellular assay was more sensitive and that the cellular immune system potentially responds to a wider range of virus molecules than what is detected by the standard antibody assay. This cellular immunity measurement research tool may provide a better method for predicting cross protection against newly emerging viruses in the absence of antibodies recognizing a novel emerging virus.
Demonstrated modifications in the influenza virus polymerase complex (the virus replication machinery) of a swine-like triple reassortant influenza virus that generated a series of attenuated or modified live vaccines against the 2009 pandemic H1N1. The development of effective pandemic virus vaccines for use in multiple species would minimize the impact of future flu pandemics. ARS scientists at the National Animal Disease Center in Ames, Iowa, and collaborators at the University of Maryland as part of a Specific Cooperative Agreement, generated and tested the safety and the efficacy of a modified-live H1N1 vaccine in both mice and pigs. Vaccination of pigs with the modified-live H1N1 vaccine candidate resulted in sterilizing immunity following experimental challenge with the 2009 H1N1 pandemic virus. This research highlights the potential of modified-live vaccines for humans and livestock. These results can be used by regulatory agencies and scientists developing improved influenza vaccines for swine.