SARS-CoV-2 peptide vaccine elicits T-cell responses in mice but does not protect against infection or disease

There is significant interest in T-cell mediated immunity against SARS-CoV-2. Both vaccination and infection have been observed to elicit durable T-cell responses against the virus. The classical role of CD4+ T-cell responses in coordinating humoral immunity is well understood but it is less clear to what degree, if any, T-cell responses play a direct protective role against infection In this study we vaccinated BALB/c mice with peptides derived from the SARS-CoV-2 proteome designed to either elicit T-cell responses or B-cell responses against linear epitopes. These peptides were administered in combination with either of two adjuvants, poly(I:C) and the STING agonist BI-1387466. Both adjuvants consistently elicited responses against the same peptides, preferentially from the group selected for predicted T-cell immunogenicity. The magnitude of T-cell responses was, however, significantly higher with BI-1387466 compared with poly(I:C). Neither adjuvant group, however, provided any protection against infection with the murine adapted virus SARS-CoV-2-MA10 or from disease following infection. ### Competing Interest Statement The authors have declared no competing interest.