Development of chimeric protein for vaccine against foot and mouth disease virus

Abstract

Foot and Mouth Disease Virus (FMDV), causes the economically devastating foot and mouth disease (FMD) in cloven-hoofed domestic and wild animals. The global predominance of various FMDV serotypes with rapidly evolving VP1 capsid proteins necessitates the development of long-term preventive measures to counter newly emerged novel lineages and sub-lineages, as well as vaccine escape mutants, in FMD-endemic regions. Chimeric protein-based vaccination candidates, which comprise many continuous and discontinuous epitopes from circulating FMDV strains, provide a single immunogen platform for mitigating rapidly developing pandemic and endemic FMDV strains. Recent reports on the emergence of evolutionarily significant lineages and sub-lineages of FMDV serotypes that are dominantly circulating in Bangladesh and neighboring Asian countries strongly support the development of a multivalent platform consisting of protective epitopes from a variety of phylogenetically proponent strains. The purpose of this study was to characterize the diversity of the VP1 capsid protein of FMDV serotypes O and A, which are currently dominant and endemic, and to identify a unique epitope combination for generating chimeric protein vaccine candidates against FMDV. Following phylogenetic study of the VP1 capsid protein sequences, two serotype-specific chimeric proteins, B1 and B3, were constructed. They contain several B- and T-cell epitopes from FMDV serotypes O and A, respectively, in addition to the universal T-cell epitopes PADRE and Invasin. Following codon optimization, expression in a heterologous prokaryotic system, purification, and in-vitro characterization, the recombinant proteins were evaluated for antiFMDV

immunogenicity using several dosages of B1 and B3 in guinea pig models. The serological assays with anti-B1 and anti-B3 GP serum demonstrated that the higher (100 µg and 50 µg, respectively) dosages of both antigens created a considerable protective immunogenicity in experimental animals. The SN50 titer of anti-B1 sera (100 µg/dose) demonstrated anti-FMDV protection against multiple virus strains, demonstrating immunogenic efficacy against circulating serotype-O strains and a recently emerging sublineage.

Anti-FMDV immunogenicity was determined in a virus neutralization test using anti-B3 sera against multiple Serotype-A strains, with the exception of BAN/GA/Sa-197/2013, which possesses an inactivated vaccine escape mutation due to amino acid substitutions and distortion in the B-C and G-H loops of the VP1 sequence. The B1 vaccine candidate showed significant immune potency against evolutionarily diverse strains of serotype-O, whereas B3 immunogen should be further modified by epitope reselection, inclusion of BC loop, optimization of expression condition and antigen load to enhance immunogenic stability and develop more potent vaccine candidate for FMDV serotype A. The immunoprotective efficacy of the recombinant proteins should also be evaluated further using live virus challenge methods in guinea pig and cattle, along with homologous and heterologous virus strains recovered from diverse FMD endemic areas in this south Asian region. This is the first report on novel designs for FMDV vaccine candidates that incorporate distinct epitopes from the most recent sub-lineages of dominant serotypes exhibiting enhanced anti-FMDV immunopotency.