Article
作者: Sin, Laura ; López-Bravo, María ; Álvarez, Enrique ; Meyerhans, Andreas ; Esteban, Ignasi ; Borrajo, Mireya L. ; Perdiguero, Beatriz ; Plana, Montserrat ; Marcos-Villar, Laura ; Lou, Gustavo ; García, Felipe ; Sisteré-Oró, Marta ; Zamora, Carmen ; Cuesta, Belén ; López-Bigas, Núria ; Esteban, Mariano ; Franceschini, Lorenzo ; Alonso, María J. ; Casasnovas, José M. ; Gelpí, Josep L. ; Astorgano, David ; Thielemans, Kris ; Gómez, Carmen Elena ; Sorzano, Carlos Óscar S. ; Sánchez-Cordón, Pedro J. ; Anthiya, Shubaash ; García-Arriaza, Juan
Despite the high efficiency of current SARS-CoV-2 mRNA vaccines in reducing COVID-19 morbidity and mortality, waning immunity and the emergence of resistant variants underscore the need for novel vaccination strategies. This study explores a heterologous mRNA/Modified Vaccinia virus Ankara (MVA) prime/boost regimen employing a trimeric form of the receptor binding domain (RBD) of the SARS-CoV-2 spike (S) protein compared to a homologous MVA/MVA regimen. In C57BL/6 mice, the RBD was delivered during priming via an mRNA vector encapsulated in nanoemulsions (NE) or lipid nanoparticles (LNP), followed by a booster with a replication-deficient MVA-based recombinant virus (MVA-RBD). This heterologous mRNA/MVA regimen elicited strong anti-RBD binding and neutralizing antibodies (BAbs and NAbs) against both the ancestral SARS-CoV-2 strain and different variants of concern (VoCs). Additionally, this protocol induced robust and polyfunctional RBD-specific CD4 and CD8 T cell responses, particularly in animals primed with mLNP-RBD. In K18-hACE2 transgenic mice, the LNP-RBD/MVA combination provided complete protection from morbidity and mortality following a live SARS-CoV-2 challenge compared with the partial protection observed with mNE-RBD/MVA or MVA/MVA regimens. Although the mNE-RBD/MVA regimen only protects half of the animals, it was able to induce antibodies with Fc-mediated effector functions besides NAbs. Moreover, viral replication and viral load in the respiratory tract were markedly reduced and decreased pro-inflammatory cytokine levels were observed. These results support the efficacy of heterologous mRNA/MVA vaccine combinations over homologous MVA/MVA regimen, using alternative nanocarriers that circumvent intellectual property restrictions of current mRNA vaccine formulations.