Replicative Fitness of Seasonal Influenza A Viruses With Decreased Susceptibility to Baloxavir.

Chesnokov, Anton; Patel, Mira C; Mishin, Vasiliy P; De La Cruz, Juan A; Lollis, Lori; Nguyen, Ha T; Dugan, Vivien; Wentworth, David E et al. · J Infect Dis · 2020

basic_science · Level V

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Abstract

Susceptibility of influenza A viruses to baloxavir can be affected by changes at amino acid residue 38 in the polymerase acidic (PA) protein. Information on replicative fitness of PA-I38-substituted viruses remains sparse. We demonstrated that substitutions I38L/M/S/T not only had a differential effect on baloxavir susceptibility (9- to 116-fold) but also on in vitro replicative fitness. Although I38L conferred undiminished growth, other substitutions led to mild attenuation. In a ferret model, control viruses outcompeted those carrying I38M or I38T substitutions, although their advantage was limited. These findings offer insights into the attributes of baloxavir-resistant viruses needed for informed risk assessment.

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