Influenza A virus, typically encountered more frequently than types B and C, and associated with the majority of serious epidemics, can be further subdivided into strains or subtypes based on antigenic differences in the external hemagglutinin proteins (H1-H16) and neuraminidase proteins (N1-N9).
An open reading frame or ORF is a portion of an organism’s genome which contains a sequence of bases that could potentially encode a protein. In a gene, ORFs are located between the start-code sequence (initiation codon) and the stop-code sequence (termination codon).
Historically, human influenza virus infections have been associated with H1N1, H2N2, and H3N2 subtypes of influenza A, although a recent (1997) and significant outbreak in Hong Kong was identified as an H5N1 subtype. This outbreak was not only significant because it resulted in 18 human infections and 6 deaths, but it also represented the first known demonstration of avian influenza virus transmission to humans.
Influenza A was divided into strains or subtypes based on antigenic differences in the external hemagglutinin proteins (H1-H16) and neuraminidase proteins (N1-N9)
Depending upon the serological requirements or research interest (natural infection, vaccine monitoring, or DIVA [Differentiation of Infected from Vaccinated Animals]), it may be useful to monitor the development of influenza A NP-specific antibody in a variety of species. Several laboratories have developed a highly sensitive and specific enzyme-linked immunosorbent assay (ELISA) for the detection of influenza A NP-specific antibodies in serum from human and veterinary sources. Because the assay utilizes “inhibition of binding” technology, it may be used with serum from any species, and therefore does not require species-specific conjugates. The assay can be completed in less than 1.5 hr., contains only one wash step, and incorporates proprietary diluents that are designed to prevent the development of nonspecific signal derived from sample matrix and/or the nonspecific adsorption of reactive test components. The result is an assay that is both highly sensitive and specific.