An intranasal self-amplifying RNA SARS-CoV-2 vaccine produces durable respiratory and systemic immunity
While mRNA vaccines have been effective in combating SARS-CoV-2, waning of vaccine-induced antibody responses and lack of vaccine-induced respiratory tract immunity contribute to ongoing infection and transmission. In this work, we compare and contrast intranasal (i.n.) and intramuscular (i.m.) administration of a SARS-CoV-2 self-amplifying RNA (saRNA) vaccine delivered by a nanostructured lipid carrier (NLC). Both i.m. and i.n. vaccines induce potent systemic serum neutralizing antibodies, bone marrow-resident IgG-secreting cells, and splenic T cell responses. The i.n. vaccine additionally induces robust respiratory mucosal immune responses, including SARS-CoV-2-reactive lung-resident memory and lung-homing T cell populations. As a booster following previous i.m. vaccination, the i.n. vaccine also elicits the development of mucosal virus-specific T cells. Both the i.m. and i.n. administered vaccines durably protect hamsters from infection-associated morbidity upon viral challenge, significantly reducing viral loads and preventing challenged hamsters from transmitting virus to naive cagemates. This saRNA-NLC vaccines potent systemic immunogenicity, and additional mucosal immunogenicity when delivered i.n., may be key for combating SARS-CoV-2 and other respiratory pathogens.