Increased Antibody Avidity and Cross-Neutralization of Severe Acute Respiratory Syndrome Coronavirus 2 Variants by Hyperimmunized Transchromosomic Bovine-Derived Human Immunoglobulins for Treatment of Coronavirus Disease 2019

Polyclonal human antibodies were derived from transchromosomic bovines hyperimmunized with SARS-CoV-2 spike. These high-affinity antibodies, which are being evaluated in clinical trials, demonstrated broad cross-neutralization activity against emerging SARS-CoV-2 variants and can be used for treatment of COVID-19. Passive antibody immunotherapeutics directed against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are promising countermeasures for protection and treatment of coronavirus disease 2019 (COVID-19). SARS-CoV-2 variants of concern (VOCs) and variants of interest (VOIs) can impact the clinical efficacy of immunotherapeutics. A fully human polyclonal antibody immunotherapeutic purified from plasma of transchromosomic (Tc) bovines hyperimmunized with SARS-CoV-2 WA-1 spike (SAB-185) is being assessed for efficacy in a phase 2/3 clinical trial when different circulating SARS-CoV-2 variants predominated. We evaluated antibody binding, avidity maturation, and SARS-CoV-2 VOCs/VOIs virus-neutralizing capacity of convalescent plasma compared with different lots of SAB-185 and individual Tc bovine sera sequentially obtained after each vaccination against Alpha, Epsilon, Iota, Gamma, Beta, Kappa, and Delta variants. In contrast to convalescent plasma, sera and SAB-185 derived from hyperimmunized Tc bovines demonstrated higher antibody avidity and more potent cross-neutralizing activity of VOCs/VOIs. Thus, SAB-185 is a potential promising therapeutic candidate for the treatment of patients infected with SARS-CoV-2 variants.