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

Micaela Ziraldo,Patricia Zamorano,Juan E Bidart,Nora Mattion,Cecilia A Prato,María V Tribulatti,Alejandra L D’Antuono

doi:10.3389/fmicb.2020.591019

Abstract

Although replication-defective human adenovirus type 5 (Ad5) vectors that express in situ the capsid-encoding region of foot-and-mouth disease virus (FMDV) have been proven to be effective as vaccines in relevant species for several viral strains, the same result was not consistently achieved for the O1/Campos/Brazil/58 strain. In the present study, an optimization of the Ad5 system was explored and was proven to enhance the expression of FMDV capsid proteins and their association into virus-like particles (VLPs). Particularly, we engineered a novel Ad5 vector (Ad5[PVP2]OP) which harbors 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 contains the amino acid substitutions S93F/Y98F in the VP2 protein coding sequence, predicted to stabilize FMD virus particles. Cells infected with the optimized vector showed an ∼14-fold increase in protein expression as compared to cells infected with an unmodified Ad5 vector tested in previous works. Furthermore, amino acid substitutions in VP2 protein allowed the assembly of FMDV O1/Campos/Brazil/58 VLPs. Evaluation of several serological parameters in inoculated mice with the optimized Ad5[PVP2]OP candidate revealed an enhanced vaccine performance, characterized by significant higher titers of neutralizing antibodies, as compared to our previous unmodified Ad5 vector. Moreover, 94% of the mice vaccinated with the Ad5[PVP2]OP candidate were protected from homologous challenge. These results indicate that both the optimized protein expression and the stabilization of the in situ generated VLPs improved the performance of Ad5-vectored vaccines against the FMDV O1/Campos/Brazil/58 strain and open optimistic expectations to be tested in target animals.

Highlights

Included in the A list of infectious diseases of animals of the Office International des Épizooties (OIE), foot-and-mouth disease (FMD) is one of the most contagious animal illnesses that affects several species of wild and domestic cloven-hoofed ruminants (Knight-Jones et al, 2016, 2017)
We found that ultracentrifugation in sucrose gradients of lysates derived from non-permissive Madin–Darby bovine kidney (MDBK) cells infected with adenovirus type 5 (Ad5)[PVP2]OP showed a sedimentation pattern consistent with the generation of 75S FMD virus (FMDV) subunits (Supplementary Figure S1)
Recombinant adenovirus vectors have demonstrated promising capabilities as vaccine candidates for several FMDV strains (Grubman et al, 2009), it has been more difficult to achieve the same results with some strains of serotype O, for the epidemiologically relevant O1/Campos/Brazil/58 strain (Caron et al, 2005; D’Antuono et al, 2010; Moraes et al, 2011; Romanutti et al, 2013; Medina et al, 2015)

Summary

INTRODUCTION

Included in the A list of infectious diseases of animals of the Office International des Épizooties (OIE), foot-and-mouth disease (FMD) is one of the most contagious animal illnesses that affects several species of wild and domestic cloven-hoofed ruminants (Knight-Jones et al, 2016, 2017). In FMD endemic regions, disease control is mainly achieved by regular vaccination (Knight-Jones and Rushton, 2013; Naranjo and Cosivi, 2013) In this regard, the currently employed vaccines are reliant on the use of highly purified, highly concentrated, inactivated FMDV antigen (Grubman and Baxt, 2004). The currently employed vaccines are reliant on the use of highly purified, highly concentrated, inactivated FMDV antigen (Grubman and Baxt, 2004) Despite their effectiveness, these vaccine formulations have several drawbacks, including the difficulty to differentiate infected from vaccinated animals, the need for expensive high-containment Biosafety Level 4-OIE (BSL4-OIE) manufacturing facilities, and the generation of large amounts of infectious virus required for vaccine production. Our results showed an enhanced vaccine performance, as demonstrated by the higher total and neutralizing antibody responses and an improved protection upon homologous challenge in a mouse model

MATERIALS AND METHODS

DISCUSSION

Findings

ETHICS STATEMENT