Broad-Spectrum Heavily Mutated Monoclonal Antibody Isolated from COVID-19 Convalescent Vaccinee with Capacity to Neutralize SARS-CoV2 Variants Ranging from B.1 to BQ.1.1 (preprint)

The increasing prevalence of the highly antibody-evasive Omicron sublineages increases the risk of breakthrough infections and leaves high-risk and vulnerable immunocompromised individuals with no effective options for prophylactic or therapeutic antibody treatments. Here, we report a heavily mutated anti-RBD monoclonal antibody, Acovimab, directed against a site in the receptor-binding motif (RBM) region of the CoV2 receptor-binding domain (RBD), that possesses very broad and highly potent neutralizing activity against CoV2 variants, including many Omicron variants. This antibody is derived from the IGHV1-58*01 germline sequence and possesses a relatively high level of mutation (15.5% of the VH aa sequence), which is unusual for anti-RBD antibodies. Neutralizing activity was very potent (IC50s range of 1-9 ng/ml) for early Omicron subvariants that possess an unmutated F486 residue and is retained but less potent (IC50s of 200-650 ng/ml) for more resistant Omicron subvariants which contain the F486V mutation (BA4/5, BA4.6, and BQ1.1), but is lost for the later ultra-resistant variants that contain F486S (XBB) or F486P (XBB.1.5) mutations. Based on these specificities, it is predicted that Acovimab by itself should protect against CoV2 infections other than those caused by the XBB/XBB.1.5 family. Acovimab also shows strong synergy in neutralization when combined with Sotrovimab, which neutralizes all Omicron variants, including XBB.1.5. Plasma from subjects with hybrid immunity (induced by vaccination + infection) possessed low levels of XBB.1.5 RBM-targeting plasma-neutralizing antibodies, and these also neutralized synergistically when combined with Sotrovimab. These results suggest potentially novel immunotherapeutic options for treating most of the CoV2 variants responsible for current infections.

Prior SARS-CoV2 infection in vaccinated solid organ transplant recipients induces potent neutralization responses against variants, including Omicron (preprint)

Factors affecting functional antibody responses in solid organ transplant recipients (SOTRs) to current SARS-CoV2 vaccines are not well understood. Here, we measured vaccine-induced neutralizing activities against the D614G-CoV2 baseline virus and eight variants, including Omicron, in a panel of CoV2 infected- (n=13) and uninfected- (n=63) vaccinated kidney and heart transplant recipients. In the CoV2 uninfected-vaccinated subset, only 19% and 35% of two and three-dose vaccinated recipients respectively possessed minimally protective neutralizing plasma antibody titers (IC50>1:50) against D614G. In contrast, all of the CoV2 infected-vaccinated SOTRs who received two vaccine doses possessed titers exceeding minimal protection; 12/13 exhibiting strong protection (IC50>1:600) against D614G with minimal increases provided by a third dose. Omicron was the most resistant variant: only 10% of CoV2 uninfected-vaccinated SOTRs reached the minimally protective neutralization titer, while 76% of CoV2 infected-vaccinated SOTRs exceeded this value. These results indicate that prior infection and vaccination can induce highly protective antibody responses in many SOTRs, and identify important factors (shorter time since transplantation, prednisone administration, and African American ethnicity) that limit these responses. Overall, these results suggest factors to consider in establishing optimum COVID-19 vaccination strategies in these cohorts.