Preclinical studies of a receptor-binding domain (RBD) vaccine derived from the Gamma SARS-CoV-2 variant adjuvanted with Alum showed it to be more immunogenic than an ancestral RBD vaccine, inducing broader neutralizing antibodies. The Gamma RBD induced a higher proportion of specific B cells and plasmablasts, along with antigen-specific T cell responses. It conferred protection against ancestral and Omicron BA.5 SARS-CoV-2 challenge in mice and performed better as a heterologous booster than homologous boosters in mice previously immunized with different vaccine platforms. The adjuvanted Gamma RBD vaccine is a promising broad-spectrum vaccine candidate.

Lorena M. Coria, Juan Manuel Rodriguez, Agostina Demaria, Laura A. Bruno, Mayra Rios Medrano, Celeste Pueblas Castro, Eliana F. Castro, Sabrina A. Del Priore, Andres C. Hernando Insúa, Ingrid G. Kaufmann, Lucas M. Saposnik, William B. Stone, Linael Prado, Ulises S. Notaro, Ayelen N. Amweg, Pablo U. Díaz, Martin Avra, Hugo Ortega, Ana Ceballos, Valeria Krum, Francisco M. Zurvar, Johanna E. Sidabra, Ignacio Drehé, Jonathan A. Baque, Mariana Li Causi, Analia V. De Nichilo, Cristian J. Payes, Teresa Southard, Julio C. Vega, Albert J. Auguste, Diego E. Álvarez, Juan M. Flo, Karina A. Pasquevich, Juliana Cassataro