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Volume 25, Number 10—October 2019

Susceptibility of Influenza A, B, C, and D Viruses to Baloxavir1

Vasiliy P. Mishin, Mira C. Patel, Anton Chesnokov, Juan De La Cruz, Ha T. Nguyen, Lori Lollis, Erin Hodges, Yunho Jang, John Barnes, Timothy Uyeki, Charles T. Davis, David E. Wentworth, and Larisa V. GubarevaComments to Author 
Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (V.P. Mishin, M.C. Patel, A. Chesnokov, J. De La Cruz, H.T. Nguyen, L. Lollis, E. Hodges, Y. Jang, J. Barnes, T. Uyeki, C.T. Davis, D.E. Wentworth, L.V. Gubareva); Battelle Memorial Institute, Atlanta (M.C. Patel, J. De La Cruz, H.T. Nguyen, L. Lollis)

Main Article

Table 2

Baloxavir susceptibility of zoonotic and animal influenza A viruses in MDCK-SIAT1 cells*

Virus subtype FRA
No. viruses tested EC50, nmol/L, mean ± SD† No. viruses tested EC50, nmol/L, mean ± SD†
Avian origin
H5N6‡ 3 0.31 ± 0.19
H6N1 1 0.12 1 0.48
H7N9 19 0.48 ± 0.32 9 1.44 ± 1.08
H9N2§ 1 0.18 1 0.53

Swine origin
H1N1¶ 3 0.72 ± 0.27
H1N1v 3 0.51 ± 0.12
H1N2v 9 1.19 ± 0.36

0.86 ± 0.50
Reference viruses#
A/Illinois/08/2018 (H1N1)pdm09 PA-I38 2.12 1.75 ± 0.59
A/Illinois/37/2018 (H1N1)pdm09 PA-I38L
14.96 (7-fold)** 13.09 ± 3.56 (8-fold)**

*Both assays were conducted by using MDCK-SIAT1 cells. Details on viruses tested are in the Appendix. According to World Health Organization nomenclature, the swine-origin influenza viruses isolated from humans are named variant viruses (e.g., A[H1N1]v). EC50, 50% effective concentration; FRA, focus reduction assay; HINT, high-content imaging neutralization test; –, not tested.
†Mean ± SD or average of 2 test results.
‡One of 3 viruses was isolated from chicken (Appendix Table 1).
§Virus was isolated from chicken (Appendix Table 1).
¶All 3 viruses were isolated from swine (Appendix Table 2).
#A pair of seasonal influenza A(H1N1)pdm09 viruses were included in each test as reference viruses (12).
**Fold change to EC50 of virus carrying PA-I38L compared with sequence-matched control virus carrying PA-I38.

Main Article

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Main Article

1Preliminary results from this study were presented at the 6th International Society for Influenza and Other Respiratory Virus Diseases Antiviral Group Conference; November 13–15, 2018; Rockville, Maryland, USA.

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