Optimized Adenoviral Vector That Enhances the Assembly of FMDV O1 Virus-Like Particles in situ Increases Its Potential as Vaccine for Serotype O Viruses

BIDART, JUAN E.; ZAMORANO, PATRICIA; ZIRALDO, MICAELA; TRIBULATTI, MARÍA V.; D?ANTUONO, ALEJANDRA L.; PRATO, CECILIA A.; MATTION, NORA

Frontiers in Microbiology

Frontiers

Año: 2020 vol. 11 p. 1 - 19

Although replication-defective human adenovirus type 5 (Ad5) vectors that expressin situ the capsid-encoding region of foot-and-mouth disease virus (FMDV) have beenproven to be effective as vaccines in relevant species for several viral strains, thesame result was not consistently achieved for the O1/Campos/Brazil/58 strain. In thepresent study, an optimization of the Ad5 system was explored and was proven toenhance the expression of FMDV capsid proteins and their association into virus-likeparticles (VLPs). Particularly, we engineered a novel Ad5 vector (Ad5[PVP2]OP) whichharbors the foreign transcription unit in a leftward orientation relative to the Ad5 genome,and drives the expression of the FMDV sequences from an optimized cytomegalovirus(CMV) enhancer-promoter as well. The Ad5[PVP2]OP vaccine candidate also containsthe amino acid substitutions S93F/Y98F in the VP2 protein coding sequence, predictedto stabilize FMD virus particles. Cells infected with the optimized vector showedan 14-fold increase in protein expression as compared to cells infected with anunmodified Ad5 vector tested in previous works. Furthermore, amino acid substitutionsin VP2 protein allowed the assembly of FMDV O1/Campos/Brazil/58 VLPs. Evaluationof several serological parameters in inoculated mice with the optimized Ad5[PVP2]OPcandidate revealed an enhanced vaccine performance, characterized by significanthigher titers of neutralizing antibodies, as compared to our previous unmodified Ad5vector. Moreover, 94% of the mice vaccinated with the Ad5[PVP2]OP candidate wereprotected from homologous challenge. These results indicate that both the optimizedprotein expression and the stabilization of the in situ generated VLPs improved theperformance of Ad5-vectored vaccines against the FMDV O1/Campos/Brazil/58 strainand open optimistic expectations to be tested in target animals.