New Rapid Test for Influenza Subtypes H5, H7, H9

The "need for speed" in combating flu viruses with pandemic potential, is being addressed with a new reagent kit.

To enable a rapid vaccine response during a severe outbreak, there is a time-of-essence need for an assay with the sensitivity to track potency in dose-sparing and adjuvanted vaccines.

Rapid influenza diagnostic tests (RIDTs) are immunoassays that can identify the presence of influenza A and B viral nucleoprotein antigens in respiratory specimens, says the Centers for Disease Control and Prevention (CDC).

Most RIDTs can yield results in a clinically relevant time frame, which is approximately 15 minutes.

This new test kit is available for flu vaccines containing H5, H7, and H9 flu subtypes, which includes new H7 vaccines against the avian H7N9 virus.

According to the December 2017 Risk Assessment Summary by the World Health Organization (WHO), "Since 2013, a total of 1,565 laboratory-confirmed cases of human infection with avian influenza A(H7N9) viruses, including at least 612 deaths, have been reported to WHO."

In response to concerns over these deadly H7N9 flu viruses, in 2017 the U.S. government issued a call for new vaccines to be included in the Strategic National Stockpile for protection of the U.S. population in the event of an outbreak. 

Avian influenza viruses, especially A/H5N1 and A/H7N9 represent the latest threat for a lethal influenza pandemic, reports the CDC.

The panel of monoclonal antibodies that provide the test with virus subtype specificity was developed by scientists at the Center for Biologics Evaluation and Research (CBER) within the US Food and Drug Administration and licensed by InDevR in 2017.

The current gold standard method for flu vaccine potency determination, single radial immunodiffusion (SRID), falls short on all these counts.

Most importantly, it can take months to develop the reference reagents needed to perform the SRID assay, which, as demonstrated in the 2009 H1N1 pandemic can delay the delivery of flu vaccine.

In contrast, the VaxArray® Pandemic Hemagglutinin Potency product is ready for use "off the shelf.”

And, subject to regulatory approval for lot release testing, could be implemented immediately for dose-sparing and/or adjuvanted vaccines if a new, responsive H5, H7 or H9 flu virus emerges as a threat.

The reference standards for laboratory confirmation of influenza virus infection in respiratory specimens are reverse transcription-polymerase chain reaction (RT-PCR) or viral culture.

However, RIDTs have limited sensitivity to detect influenza viruses in respiratory specimens compared to RT-PCR or viral culture and negative RIDT test results should be interpreted with caution given the potential for false negative results, especially during peak influenza activity in a community.

Most RIDTs do not include rapid molecular assays that have higher sensitivity to detect influenza viruses in respiratory specimens compared to RIDTs.

Some RIDTs distinguish between influenza A or B viruses while others do not.

RIDTs that provide results on the type of influenza virus (e.g., influenza A or B virus), do not provide information on influenza A virus subtype [e.g., A(H1N1)pdm09 versus A(H3N2)] or specific virus strain information (e.g., a degree of similarity to vaccine strains).

RIDTs cannot distinguish between seasonal influenza A virus infection and novel influenza A virus infection, due to infection with avian or variant influenza A viruses.

This work was sponsored as part of the Department of Health and Human Services' inter-agency Influenza Vaccine Improvement Initiative. Specifically, product development was supported by a Small Business Innovation Research grant R44AI102318 through the National Institute of Allergy and Infectious Diseases, which is part of the National Institutes of Health (NIH).

For more information about InDevr and products, please visit www.indevr.com or call 303-402-9100. The content of this press release is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

In the United States, a number of RIDTs are commercially available.