Protection of mice from lethal coronavirus MHV-A59 infection by monoclonal affinity-purified spike glycoprotein

Numerous studies have provided indirect evidence that the spike glycoprotein of coronaviruses (E2 or S) bears determinants for pathogenesis and the induction of protective immunity. In order to directly evaluate its immunogenicity, the E2 glycoprotein of the murine hepatitis virus, strain A59, was purified by immunoaffinity chromatography. High titers of neutralizing and fusion inhibiting antibodies were induced in mice vaccinated with purified E2/S in Freund's adjuvant, which were protected from an intracerebral challenge with 10 LD50 of MHV-A59. This study provides a direct demonstration of the importance of the coronavirus spike glycoprotein in the induction of a protective immune response.