Impact of influenza A virus neuraminidase mutations on the stability, activity, and sensibility of the neuraminidase to neuraminidase inhibitors.
BACKGROUND
The influenza neuraminidase plays a critical role in the spread of the influenza A and B viruses. Through the cleavage of terminal sialic acid from glycoconjugates, it facilitates the elution of progeny virions from infected cells and prevents their self-aggregation.


OBJECTIVE
Our objective was to study the impact of mutations at framework sites not under direct selective pressure in the neuraminidase active site.


METHODS
In the A/Moscow/10/99 (H3N2) virus background, viruses containing mutations in NA framework residues (E119D, R156K, W178L, S179A, D198N, I222L, E227G, H274Y, E277G, N294D, and E425G) were constructed by reverse genetics. After several passages on MDCK cells, fluorimetric assays were conducted to assess the neuraminidase activity and sensibility to the neuraminidase inhibitors (IC50).


RESULTS
Among the viruses detectable through the phenotypic tests, R156K, I222L, H274Y, N294D and E425G viruses presented a NA activity between 70% and 100% of the A/Moscow/10/99 wild type one. The D198N and the E119D mutations decreased seriously in NA activity compared to the wild-type (>10-fold). The I222L mutation reduced susceptibility to oseltamivir (18-fold).


CONCLUSIONS
With the exception of one mutation, framework mutations on N2 background do not induce resistance. Nevertheless they tend to decrease slowly the sensitivity to one or the other inhibitors.
Virologie et Pathologie Humaine, CNRS FRE 3011, Université Lyon1, 7 Rue Guillaume Paradin, 69372 Lyon Cedex 08, France.
Mathilde
M
Richard
Claire
C
Deléage
Mendy
M
Barthélémy
Yi Pu
YP
Lin
Alan
A
Hay
Bruno
B
Lina
Olivier
O
Ferraris
D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D001665:Binding Sites; D002460:Cell Line; D004285:Dogs; D024882:Drug Resistance, Viral / Q000235:genetics*; D053122:Influenza A Virus, H3N2 Subtype / Q000187:drug effects* / Q000235:genetics; D020128:Inhibitory Concentration 50; D008826:Microbial Sensitivity Tests; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D009439:Neuraminidase / Q000037:antagonists & inhibitors* / Q000235:genetics*; D053139:Oseltamivir / Q000494:pharmacology*; D014764:Viral Proteins / Q000037:antagonists & inhibitors / Q000235:genetics
D000998:Antiviral Agents; D014764:Viral Proteins; D053139:Oseltamivir; D009439:Neuraminidase