Development of an immunochromatographic assay specifically detecting pandemic H1N1 (2009) influenza virus.

The pandemic caused by a new type of influenza virus, pandemic H1N1 (2009) influenza virus A (AH1pdm), has had a major worldwide impact. Since hemagglutinin (HA) genes are among the most specific genes in the influenza virus genome, AH1pdm can be definitively diagnosed by viral gene analysis targeting the HA genes. This type of analysis, however, cannot be easily performed in clinical settings. While commercially available rapid diagnosis kits (RDKs) based on immunochromatography can be used to detect nucleoproteins (NPs) of influenza A and B viruses in clinical samples, there are no such kits that are specific for AH1pdm. We show here that an RDK using a combination of monoclonal antibodies against NP can be used to specifically detect AH1pdm. The RDK recognized AH1pdm virus isolates but did not recognize seasonal H1N1 and H3N2 and influenza B viruses, indicating that the specificity of the RDK is 100%. A parallel comparison of RDK with a commercial influenza A/B virus kit revealed that both types of kits had equal sensitivities in detecting their respective viruses. Preliminary evaluation of clinical samples from 5 individuals with PCR-confirmed human AH1pdm infection showed that the RDK was positive for all samples, with the same detection intensity as that of a commercial influenza A/B virus kit. This RDK, together with a new vaccine and the stockpiling of anti-influenza drugs, will make aggressive measures to contain AH1pdm infections possible.