ABSTRACT
The emergence of novel Omicron lineages, such as BA.5, may impact the therapeutic efficacy of anti-SARS-CoV-2 neutralizing monoclonal antibodies (mAbs). Here, we evaluated the neutralization and ADCC activity of 6 therapeutic mAbs against Delta, BA.2, BA.4 and BA.5 isolates. The Omicron sub-variants escaped most of the antibodies but remained sensitive to Bebtelovimab and Cilgavimab. Consistent with their shared spike sequence, BA.4 and BA.5 displayed identical neutralization profiles. Sotrovimab was the most efficient at eliciting ADCC. We also analyzed 121 sera from 40 immunocompromised individuals up to 6 months after infusion of 1200 mg of Ronapreve (Imdevimab + Casirivimab), and 300 or 600 mg of Evusheld (Cilgavimab + Tixagevimab). Sera from Ronapreve-treated individuals did not neutralize Omicron subvariants. Evusheld-treated individuals neutralized BA.2 and BA.5, but titers were reduced by 41- and 130-fold, respectively, compared to Delta. A longitudinal evaluation of sera from Evusheld-treated patients revealed a slow decay of mAb levels and neutralization. The decline was more rapid against BA.5. Our data shed light on the antiviral activities of therapeutic mAbs and the duration of effectiveness of Evusheld pre-exposure prophylaxis.
ABSTRACT
Since early 2022, Omicron BA.1 has been eclipsed by BA.2, which was in turn outcompeted by BA.5, that displays enhanced antibody escape properties. Here, we evaluated the duration of the neutralizing antibody (Nab) response, up to 16 months after Pfizer BNT162b2 vaccination, in individuals with or without BA.1/BA.2 breakthrough infection. We measured neutralization of the ancestral D614G lineage, Delta and Omicron BA.1, BA.2, BA.5 variants in 291 sera and 35 nasal swabs from 27 individuals. Upon vaccination, serum Nab titers were reduced by 10, 15 and 25 fold for BA.1, BA.2 and BA.5, respectively, compared with D614G. The duration of neutralization was markedly shortened, from an estimated period of 11.5 months post-boost with D614G to 5.5 months with BA.5. After breakthrough, we observed a sharp increase of Nabs against Omicron subvariants, followed by a plateau and a slow decline after 4 or 5 months. In nasal swabs, infection, but not vaccination, triggered a strong IgA response and a detectable Omicron neutralizing activity. Thus, BA.5 spread is partly due to abbreviated vaccine efficacy, particularly in individuals who were not infected with previous Omicron variants.