Skip directly to site content Skip directly to page options Skip directly to A-Z link Skip directly to A-Z link Skip directly to A-Z link
Volume 27, Number 7—July 2021
Dispatch

Cluster of Oseltamivir-Resistant and Hemagglutinin Antigenically Drifted Influenza A(H1N1)pdm09 Viruses, Texas, USA, January 2020

Teena Mohan1, Ha T. Nguyen1, Krista Kniss, Vasiliy P. Mishin, Angiezel A. Merced-Morales, Jennifer Laplante, Kirsten St. George, Patricia Blevins, Anton Chesnokov, Juan A. De La Cruz, Rebecca Kondor, David E. Wentworth, and Larisa V. GubarevaComments to Author 
Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (T. Mohan, H.T. Nguyen, K. Kniss, V.P. Mishin, A.A. Merced-Morales, A. Chesnokov, J.A. De La Cruz, R. Kondor, D.E. Wentworth, L.V. Gubareva); General Dynamics Information Technology, Atlanta (T. Mohan, H.T. Nguyen); New York State Department of Health, Albany, New York, USA (J. Laplante, K. St. George); San Antonio Metropolitan Health District, San Antonio, Texas, USA (P. Blevins)

Main Article

Table 2

Antigenicity of influenza A(H1N1)pdm09 viruses representing distinct HA genetic groups, United States, 2019–2020*

Virus HA subclade
6B.1A		 Ferret antiserum, titers (fold)
HINT assay
 HI assay
ID/07 HI/70 WI/588 ID/07 HI/70 WI/588
Reference
A/Idaho/07/2018 3 28,421 (1) 23,464 (3) 543 (250) 2,560 (1) 2,560 (1) 160 (16)
A/Hawaii/70/2019 5A-187A, 189E 15,132 (2) 69,032 (1) 238 (570) 1,280 (2) 2,560 (1) 160 (16)
A/Wisconsin/588/2019
 5A-156K
 592 (48)
 552 (125)
 135,765 (1)
 80 (32)
 80 (32)
 2,560 (1)
Test
n = 2 5B 60,007 (2) 83,978 (1) 3,402 (40) 2,560 (1) 5,120 (1) Not tested
n = 7 7 37,410 (1) 35,135 (2) 784 (173) 2,560 (1) 2,560 (1) 80 (32)
n = 22 5A-187A, 189E 24,863 (1) 88,411 (1) 222 (612) 1,280 (2) 2,560 (1) 80 (32)
n = 21 5A-156K 399 (71) 190 (363) 207,958 (1) 320 (8) 320 (8) 5,120 (1)

*The antigenicity of MDCK-grown influenza A(H1N1)pdm09 viruses, representing different HA genetic groups, was tested by the HINT and HI assays, using postinfection ferret antiserum, generated from the influenza A(H1N1)pdm09 vaccine candidate viruses for the Northern Hemisphere during 2019–2020 (A/Idaho/07/2019; ID/07) and 2020–21 (A/Hawaii/70/2019; HI/70), and the Southern Hemisphere for the 2021 (A/Wisconsin/588/2019; WI/588) seasons. In the HINT assay, the neutralization titers were determined by calculating the antiserum dilution factor needed to reduce the infected cell population by 50% (average titers are shown) and the HI titers were expressed as the reciprocal of the highest serum dilution that inhibit the hemagglutination of 4 HA units of virus (median titers are shown). Italics indicate homologous titers; boldface indicates fold changes determined by comparing HINT or HI titers to the respective homologous titers. HA, hemagglutinin; HI, hemagglutination inhibition; HINT, high-content imaging-based neutralization test.

Main Article

1These authors contributed equally to this article.

Page created: May 03, 2021
Page updated: June 17, 2021
Page reviewed: June 17, 2021
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.
file_external