Development of recombinant proteins for vaccine candidates against serotypes O and A of Foot-and-Mouth Disease virus in Bangladesh.

Frequent vaccine failure leading to recurrent outbreaks of Foot-and-Mouth Disease (FMD) in livestock populations necessitates the development of a customizable vaccine platform comprising potential antigenic determinants of circulating lineages of FMD viruses. Artificially designed, chimaeric protein-based recombinant vaccines are novel approaches to combat the phylogenetically diverse FMD Virus (FMDV) strains. Among seven recognized serotypes, only serotypes O and A are dominantly circulating in Bangladesh and neighbouring countries of Asia, where transboundary transmission, recurrent outbreaks and emergence of novel lineages of FMDV are highly prevalent. The objective of this study was to develop multi-epitope recombinant proteins, procuring immunogenicity against circulating diverse genotypes of FMDV serotypes O and A. Two chimaeric proteins, named B1 (41.0 kDa) and B3 (39.3 kDa), have been designed to incorporate potential B-cell and T-cell epitopes selected from multiple FMDV strains, including previously reported and newly emerged sub-lineages. After expression, characterization and immunization of guinea pigs with a considerable antigen load of B1 and B3 followed by serological assays revealed the significant protective immunogenicity, developed from the higher (100 µg) doses of both antigens, against most of the currently prevalent serotype O and A strains of FMDV. The efficient expression, antigenic stability, and multivalent immunogenic potency of the chimaeric proteins strongly indicate their credibility as novel vaccine candidates for existing serotypes O and A of FMDV in Bangladesh and surrounding territories.

Sequence variability in the structural protein-encoding region of foot-and-mouth disease virus serotype A and O of Ethiopian isolates.

A total of 13 serotype O and 5 serotype A FMD Ethiopian isolates and some isolates from other countries (six for serotype A and four for serotype O) were sequenced on the structural protein (P1) coding region. The deduced amino acid sequences were aligned and investigated in an attempt to determine the amino acid variation. Differences were observed at 115 (15.6%) and 119 (16.1%) amino acid positions for serotype O and serotype A, respectively. The variation in the derived amino acid sequences is the highest in VP1, while VP4 was highly conserved in both serotypes A and O. In all isolates, hypervariable regions were located at regions corresponding to the highly immunogenic sites, the G-H loop (133-158) and the C-terminus (194-213) of the VP1 gene. The RGD cell attachment site within the G-H loop of the gene was conserved in all isolates. The study revealed the presence of significant amino acid variation at VP2 and VP3 in addition to known VP1 coding region. Hence, determination of amino acid sequence of the whole P1 region provides more information on antigenic variability of FMD virus and could be used in vaccine strain selection in parallel with serological vaccine matching assays.