Resistance to neuraminidase inhibitors may be masked in influenza A H7N9, and lab testing for resistance may not always detect when the virus is resistant, according to study data published in mBio.
Researchers from the University of Hong Kong evaluated the A/Shanghai/1/2013 virus that was isolated from the first confirmed case of H7N9. They found that the neuraminidase R292K mutation confers resistance to oseltamivir (Tamiflu, Genentech), zanamivir (Relenza, GlaxoSmithKline) and peramivir (BioCryst). However, the mutation may be masked by functioning wild-type enzymes.
Although the initial enzyme test results found that the H7N9 strain was sensitive to the treatment, the researchers found that the isolate actually comprised two distinct types of the virus. Approximately 35% of the viruses actually carried the mutation conferring resistance to neuraminidase inhibitors. The remaining 65% did not.
“If H7N9 does acquire human-to-human transmissibility, we would be in big trouble because oseltamivir is what we have to treat it until we have a vaccine,” study researcher Robert Webster, PhD, of St. Jude Children’s Research Hospital, said in a press release. “Resistant strains of H7N9 can flourish in patients treated with oseltamivir or zanamivir, inadvertently leading to the spread of resistant infections.”
Disclosure: The researchers report no relevant financial disclosures.