CD has developed a highly sensitive and specific enzyme immunoassay for the detection of Influenza A nucleoprotein antigen in complex sample matrices derived from both human and veterinary sources. The assay can be completed in less than 1.5 hr. and contains only one wash step. In addition, the test kit incorporates proprietary diluents that are designed to prevent the development of nonspecific signal derived from complex sample matrix effects and/or the nonspecific adsorption of reactive test components which result in improvements in both sensitivity and specificity. The test kit is available in a standard photometric detection format or in a chemiluminescent detection format for enhanced sensitvity. The kit has been tested against a wide variety of influenza A subtypes for sensitivity and potentially interfering viruses and bacteria for specificity.
Influenza viruses can be divided into three classes, A, B, and C, largely based upon conserved antigenic differences in the internal nucleoprotein. 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).
A variety of wild waterfowl appear to be the predominant natural reservoir for Influenza A viruses and subtypes representing most of the hemagglutinin and neuraminidase combinations can be found circulating in these birds. 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.
While influenza A subtype identification is extremely important (vaccine production, epidemiology), the rapid and accurate differentiation of influenza A from influenza B and C and other respiratory agents in humans and animals is also important (treatment and biosecurity).