Investigation of the SARS-CoV-2 post-vaccination antibody response in Canadian farmed mink

Currently, SARS-CoV-2 have been detected in farmed mink in 13 different countries. Due to the high susceptibility and transmissibility among mink, great concerns of mink serving as a reservoir to generate novel variants with unknown virulence and antigenic properties arose. These concerns have consequently resulted in entire mink productions being culled and banned. This study investigates the post-vaccination antibody response in the Canadian farmed mink vaccinated with a commercial Index spike protein-based vaccine, approved for use in cats, and compares the antibody response to that observed post infection in Danish farmed mink. Blood samples were obtained from 50 mink at the Canadian Centre for Fur Animal Research (CCFAR), Dalhousie University (Truro, Canada). The sera were initially analyzed for antibodies by enzyme-linked immunosorbent assay (ELISA), and selected sera was subsequently tested in a virus neutralization tests. The levels of neutralizing antibodies were evaluated for an ancestral D614G strain and a recent circulating SARS-CoV-2 variant of concern (Omicron BA.4). The results revealed that the vaccine induced a strong antibody response in mink by reaching antibody titer levels of up to 1:12800 in the ELISA. Moreover, high levels of neutralizing antibodies were obtained, and despite the great level of genetic differences between the ancestral and Omicron BA.4 strains, the vaccinated mink showed high levels of cross-reacting neutralizing antibodies. Interestingly, the antibody levels towards SARS-CoV-2 in the Canadian vaccinated mink were significantly higher than observed in recently SARS-CoV-2 infected Danish mink and equal to anamnestic responses following re-infection. In conclusion, the vaccine used in the Canadian farmed mink was able to induce a strong and broad-reacting antibody response in mink, which could limit the spread of SARS-CoV-2 in farmed mink and thereby reduce the risk of mink serving as a SARS-CoV-2 reservoir for human infections.