Detection of Oseltamivir-and Zanamivir-Resistant Influenza A (H12N3) Virus from Wild Mallards in Sweden

• Resistance to neuraminidase inhibitors (NAIs) is a growing problem in battle against influenza A virus. However, little is known about the resistance of viruses isolated from dabbling ducks, the natural reservoir of the virus. To date, no low-pathogenic avian influenza (LPAI) virus that is resistant to NAIs has been detected. The aim of this study is to investigate mallard isolates of influenza A virus previously identified to carry oseltamivir carboxylate (OC)- or zanamivir (ZA)-related resistance mutations. In this work, 22 viruses belonging to the N1, N3, N6 and N9 subtypes were analyzed using a colorimetric NA inhibition assay. The R118K mutation was the most recurrent, as it was observed in all subtypes except for N6. IC50 values confirmed the differences in sensitivity to OC or ZA observed in the N1 and N2 groups of NAs. Furthermore, both negative controls (NC) in the N6 and one NC in the N9 subtype were less sensitive to ZA than were genotypically related mutants of the respective subtypes. One H12N3 strain (80087 isolate) was cross-resistant, with an IC50 of >104 nM. This virus carried D151K and R156K mutations that were not associated with NAI resistance. Analyses of the 3D structure of NA indicated that the NAI-resistant phenotype that retained NA catalytic activity was likely to be due to the D151K mutation. However, the residues occupying positions 149, 150 (part of the 150 loop) and 153 may have contributed to this resistance. Other possible factors included the presence of the 150 cavity, the nature of the substrate (anchored or unanchored) and the interaction of the ligand with the active site. These results demonstrate that NAI-resistant viruses exist in LPAI and highlight the importance of monitoring influenza A viruses in wild birds, as these viruses can be transmitted to humans and can thus become part of a human-adapted influenza virus with pandemic potential.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Mikrobiologi inom det medicinska området (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Microbiology in the medical area (hsv//eng)

Keyword

influenza

mallards

oseltamivir

zanamivir

aniviral

resistance

Virology

Virologi

Zoonotic Ecology

Zoonotisk ekologi

Publication and Content Type

vet (subject category)

ovr (subject category)