New Rapid Test For H5N1 Bird Flu Presented To ICEID

Preliminary research from the Department of Respiratory Disease Research at the Naval Health Research Center (NHRC) suggests that a rapid antigen assay test developed by Arbor Vita Corporation (AVC) shows promise as a useful diagnostic for the detection of the avian influenza virus in humans. Researchers from NHRC reported their findings last week at the 2008 International Conference on Emerging Infectious Diseases (ICEID) in Atlanta, Georgia.

Bird Flu Detection

The AVC test differs from other rapid-antigen assays in that it detects the NS1 protein, as opposed to the nucleoprotein (NP). Antigen capture is mediated through a PDZ protein, which binds the C-terminal region of the NS1 protein. As the C-terminal region of the NS1 protein differs for each influenza sub-type, a PDZ protein with high affinity to NS1 protein of H5 strains was chosen for assay development.

The format of the developed assay is the familiar lateral-flow rapid antigen assay. However, the role of the 'capture' antibody is performed by a PDZ protein, which provides superior specificity and binding affinity. Lateral flow assays have several advantages that make them appealing for field deployment and far-forward mission use. These include: ease of use, time to results, cost, lack of cold-chain requirements and portability.

NHRC's archive of respiratory pathogens was used to evaluate the performance of the AVC avian influenza diagnostic against clinical samples. Two hundred samples from two years of surveillance were tested with the assay following procedures provided by AVC.

In addition, NHRC collaborated with Naval Medical Research Unit 3 (NAMRU3), located in Cairo, Egypt. NAMRU3, which is the WHO collaborating site for the African continent and Middle East region, has conducted surveillance for highly pathogenic avian influenza in wild and domestic birds, as well as human populations and has access to isolate H5N1 material. Twenty-eight different H5N1 isolates from avian and human sources were tested with the AVC assay. Results of the AVC assay were presented at ICEID that showed no false positives against the respiratory clinical panel. Of the 28 H5N1 cultures tested, 26 gave positive results on the assay (sensitivity = 93%).

The researchers concluded that the "PDZ based assay produced by AVC shows promise as a useful diagnostic in our vigilance against avian influenza. The sensitivity of the assay towards avian strains is robust and the format of the test favors easy deployment." NHRC and NAMRU3 will continue to collaborate to evaluate this assay against other grown strains (H7, H9 etc.) as well as in actual outbreak situations.