A delicate balance between antibody evasion and ACE2 affinity for Omicron BA.2.75
Jiandong Huo, Aiste Dijokaite-Guraliuc, Chang Liu, Daming Zhou, Helen M. Ginn, Raksha Das, Piyada Supasa, Muneeswaran Selvaraj, Rungtiwa Nutalai, Aekkachai Tuekprakhon, Helen M. E. Duyvesteyn, Alexander J. Mentzer, Donal Skelly, Thomas Ritter, Ali Amini, Sagida Bibi, Sandra Adele, Síle A. Johnson, Neil G. Paterson, Mark A. Williams, David R. Hall, Megan Plowright, Tom Newman, Hailey Hornsby, Thushan I. de Silva, Nigel Temperton, Paul Klenerman, Eleanor Barnes, Susanna Dunachie, Andrew J. Pollard, Teresa Lambe, Philip Goulder, Elizabeth E. Fry, Juthathip Mongkolsapaya, Jingshan Ren, David I. Stuart, Gavin Screaton
Abstract
Variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have caused successive global waves of infection. These variants, with multiple mutations in the spike protein, are thought to facilitate escape from natural and vaccine-induced immunity and often increase in affinity for ACE2. The latest variant to cause concern is BA.2.75, identified in India where it is now the dominant strain, with evidence of wider dissemination. BA.2.75 is derived from BA.2 and contains four additional mutations in the receptor-binding domain (RBD). Here, we perform an antigenic and biophysical characterization of BA.2.75, revealing an interesting balance between humoral evasion and ACE2 receptor affinity. ACE2 affinity for BA.2.75 is increased 9-fold compared with BA.2; there is also evidence of escape of BA.2.75 from immune serum, particularly that induced by Delta infection, which may explain the rapid spread in India, where where there is a high background of Delta infection. ACE2 affinity appears to be prioritized over greater escape.