New Coronavirus News from 17 May 2022

Characterization of the SARS-CoV-2 B.1.621 (Mu) variant [Science TRANSLATIONAL MEDICINE, 17 May 2022]

Authored by PETER J. HALFMANN , -MAKOTO KURODA, TAMMY ARMBRUST, JAMES THEILER , 84ARIANE BALARAMGAGE, K. MORENO H5318MOLLY, A. ACCOLA, 171KIYOKO IWATSUKI-HORIMOTO, 0XRICCARDO VALDEZ, EMILY STONEMAN , KATARINA BRAUN, SEIYA YAMAYOSHI, ELIZABETH SOMSEN, JOHN J. BACZENAS, KEIKO MITAMURA, MASAO HAGIHARA, EISUKE ADACHI, MICHIKO KOGA, MATTHEW MCLAUGHLIN, WILLIAM REHRAUER, MASAKI IMAI, SHINYA YAMAMOTO, TAKEYA TSUTSUMI, MAKOTO SAITO, THOMAS C. FRIEDRICH , SHELBY L. O’CONNOR, , DAVID H. O’CONNOR, AUBREE GORDON, BETTE KORBER, AND YOSHIHIRO KAWAOKA , FEWER Authors Info & Affiliations
AND YOSHIHIRO KAWAOKA

Abstract
The SARS-CoV-2 B.1.621 (Mu) variant emerged in January 2021 and was categorized as a variant of interest by the World Health Organization in August 2021. This designation prompted us to study the sensitivity of this variant to antibody neutralization. In a live virus neutralization assay with serum samples from individuals vaccinated with the Pfizer/BioNTech or Moderna mRNA vaccines, we measured neutralization antibody titers against B.1.621, an early isolate (spike 614D), and a variant of concern (B.1.351, beta variant). We observed reduced neutralizing antibody titers against the B.1.621 variant (3.4 to 7-fold reduction, depending on the serum sample and time after the second vaccination) compared to the early isolate and a similar reduction when compared to B.1.351. Likewise, convalescent serum from hamsters previously infected with an early isolate neutralized B.1.621 to a lower degree.

Despite this antibody titer reduction, hamsters could not be efficiently re-challenged with the B.1.621 variant, suggesting the immune response to the first infection is adequate to provide protection against a subsequent infection with the B.1.621 variant.