Murine antibody 4B1D3 exhibits broad cross-reactivity and neutralizing activity against SARS-CoV-2 variants.

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), identified in late 2019, spurred a global pandemic, prompting an unprecedented international mobilization in vaccination and public health strategies. Although the pandemic is now under greater control, the worldwide dissemination of variants of concern (VOCs) has led to resistance and decreased vaccine efficacy, highlighting the urgent need for broad-spectrum therapeutic and preventive solutions. In this study, we employed hybridoma technology to generate monoclonal antibodies (mAbs) from mice immunized with the SARS-CoV-2 Wuhan Spike protein trimer. We selected clones producing anti-Spike receptor-binding domain (RBD) mAbs and characterized a panel of four mAbs to assess their potential as antiviral agents and their utility as tools in research and diagnostics. Our results showed that all mAbs recognized the SARS-CoV-2 Wuhan strain in infected cells through immunofluorescence assay. Moreover, the binding profiles of these mAbs against the RBD protein from various SARS-CoV-2 variants revealed distinct reactivity and loss of binding as VOCs emerged. However, one mAb, named 4B1D3, showed the most promising features, exhibiting broad binding and neutralizing capacity across all tested SARS-CoV-2 variants, including Omicron BA.2, BA.4/5 and XBB.1.5 sublineages. Furthermore, a single prophylactic dose of the 4B1D3 mAb provided protection to K18-hACE2 mice against a lethal challenge with SARS-CoV-2 Wuhan strain. In conclusion, these mAbs represent valuable tools for research and diagnostics and have significant potential for the development of new therapeutic strategies against SARS-CoV-2 variants.