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Evaluation of the mRNA-1273 Vaccine against SARS-CoV-2 in Nonhuman Primates
Kizzmekia S Corbett1, Barbara Flynn1, Kathryn E Foulds1
1From the Vaccine Research Center (K.S.C., B. Flynn, K.E.F., J.R.F., S.B.-B., A.P.W., B. Flach, S. O'Connell, A.T.N., N.D., M.M.D., N.N.N., G.S.A., D.R.F., E.L., N.A.D.-R., B.C.L., M.K.L., S. O'Dell, S.D.S., E.P., L.A.C., C.Y., J.-P.M.T., W.S., Y.Z., O.M.A., L.W., A.P., E.S.Y., K.L., T.Z., I.-T.T., A.W., I.G., L.N., R.A.G., R.J.L., J.I.M., W.-P.K., K.M.M., T.J.R., J.E.L., M.R.G., P.D.K., J.R.M., A.M., N.J.S., M.R., R.A.S., B.S.G.), the Infectious Disease Pathogenesis Section (K.W.B., M.M., B.M.N., M.G.L.), and the Biostatistics Research Branch, Division of Clinical Research (M.C.N.), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, and Bioqual (H.A., L.P., A.V.R., S.B., J.G., T.P.-T., A.S., T.-A.C., A. Cook, A.D., K.S., I.N.M.) and the Public Health Service Commissioned Corps (M.R.G.), Rockville - both in Maryland; the Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill (D.R.M., R.S.B.); Moderna, Cambridge, MA (D.K.E., G.S.-J., S.H., A. Carfi); and the Institute for Biomedical Sciences, George Washington University, Washington, DC (E.P.).
Background:
Vaccines to prevent coronavirus disease 2019 (Covid-19) are urgently needed. The effect of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines on viral replication in both upper and lower airways is important to evaluate in nonhuman primates.
Methods:
Nonhuman primates received 10 or 100 μg of mRNA-1273, a vaccine encoding the prefusion-stabilized spike protein of SARS-CoV-2, or no vaccine. Antibody and T-cell responses were assessed before upper- and lower-airway challenge with SARS-CoV-2. Active viral replication and viral genomes in bronchoalveolar-lavage (BAL) fluid and nasal swab specimens were assessed by polymerase chain reaction, and histopathological analysis and viral quantification were performed on lung-tissue specimens.
Results:
The mRNA-1273 vaccine candidate induced antibody levels exceeding those in human convalescent-phase serum, with live-virus reciprocal 50% inhibitory dilution (ID50) geometric mean titers of 501 in the 10-μg dose group and 3481 in the 100-μg dose group. Vaccination induced type 1 helper T-cell (Th1)-biased CD4 T-cell responses and low or undetectable Th2 or CD8 T-cell responses. Viral replication was not detectable in BAL fluid by day 2 after challenge in seven of eight animals in both vaccinated groups. No viral replication was detectable in the nose of any of the eight animals in the 100-μg dose group by day 2 after challenge, and limited inflammation or detectable viral genome or antigen was noted in lungs of animals in either vaccine group.
Conclusions:
Vaccination of nonhuman primates with mRNA-1273 induced robust SARS-CoV-2 neutralizing activity, rapid protection in the upper and lower airways, and no pathologic changes in the lung. (Funded by the National Institutes of Health and others.).
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