A class II MHC-targeted vaccine elicits immunity against SARS-CoV-2 and its variants

Abstract

Significance Vaccines remain the best hope of curtailing SARS-CoV-2 transmission, morbidity, and mortality. Currently available vaccines require cold storage and sophisticated manufacturing capacity, complicating their distribution, especially in less developed countries. We report a protein-based SARS-CoV-2 vaccine that directly and specifically targets antigen-presenting cells. It consists of the SARS-CoV-2 Spike receptor-binding domain (Spike RBD ) fused to a nanobody that recognizes class II major histocompatibility complex antigens (VHH MHCII ). Our vaccine elicits robust humoral (high-titer binding and neutralizing antibodies) and cellular immunity against SARS-CoV-2 and its variants in both young and aged mice. VHH MHCII -Spike RBD is stable for at least 7 d at room temperature and can be lyophilized without loss of efficacy, desirable attributes for logistical reasons.