[Source: Antimicrobial Agents and Chemotherapy, full page: (LINK). Abstract, edited.]
Evaluation of recombinant 2009 pandemic influenza A/H1N1 viruses harbouring zanamivir-resistance mutations in mice and ferrets.
Andrés Pizzorno 1, Yacine Abed 1, Chantal Rhéaume 1, Xavier Bouhy 1 and Guy Boivin 1,#
Author Affiliations: 1Research Center in Infectious Diseases of the CHUQ-CHUL and Laval University, Québec City, Québec, Canada
Recombinant influenza A(H1N1)pdm09 wild-type (WT) and zanamivir-resistant E119G and Q136K neuraminidase mutants were generated for determining their enzymatic and replicative properties in vitro, as well as their infectivity and transmissibility in mice and ferrets. Viral titers of recombinant E119G and Q136K mutants were significantly lower compared to those of the WT in the first 36 h post-inoculation (p.i.) in vitro. The E119G and Q136K mutations were both associated with a significant reduction of total neuraminidase (NA) activity at the cell surface of 293T cells, with relative total NA activities of 14% (P<0.01) and 20% (P<0.01), respectively, compared with the WT. The E119G mutation significantly reduced the affinity (8-fold increase in Km) but not the Vmax. The Q136K mutation increased the affinity (5-fold decrease in Km) with a reduction in Vmax (8% Vmax ratio vs the WT). In mice, infection with the E119G and Q136K mutants resulted in lung viral titers that were significantly lower compared to WT on days 3 p.i. (3.4±0.8 ×106 and 2.1±0.4 ×107 PFU/ml, respectively, vs 8.8±1.1 ×107, P<0.05) and 6 p.i. (3.0±0.5 ×105 and 8.6±1.4 ×105 PFU/ml, respectively, vs 5.8±0.3 ×107, P<0.01). In experimentally-infected ferrets, the E119G mutation rapidly reverted to WT in donor and contact animals. The Q136K mutation was maintained in ferrets although nasal wash viral titers from the Q136K contact group were significantly lower compared to WT on days 3-5 p.i. Our results demonstrate that zanamivir-resistance E119G and Q136K mutations compromise viral fitness and transmissibility in A(H1N1)pdm09 viruses.
#Corresponding author: Guy Boivin, MD, CHUL, room RC-709, 2705 blvd Laurier, Sainte-Foy,, Québec, Canada G1V 4G2, Tel: (418) 654-2705, Fax: (418) 654-2715, E-mail: Guy.Boivin@crchul.ulaval.ca
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