Class specific antibody response to influenza A H1N1 infection in swine.

Early detection of swine influenza A outbreaks is essential to understand the true cause and effect relationship that exists between this disease and other serious respiratory or herd health problems. Enzyme-linked immunosorbent assays (ELISAs) for the early detection of H1N1 subtype specific serum IgM, IgG and secretory IgA were compared to direct virus detection in in embryonated eggs. Elevated levels of H1 hemagglutinin (HA) specific IgM and IgG were detected as early as 3 days post experimental infection with a field strain of swine influenza A (H1N1). Influenza specific IgA in nasal mucous samples was detected on day 4 post infection (PI). This compared favorably with egg inoculation methods which detected virus 2-4 days PI. Identification of elevated H1 HA specific IgM in test herds could signify a recent influenza outbreak. Alternatively, ELISA analysis of nasal mucous samples for H1 HA specific IgA could provide a noninvasive method of obtaining similar information on the influenza specific immune status of the herd.