Development of baculovirus-derived bovine parvovirus VP2based chimeric virus-like particles co-displaying SAT2 FMDV VP1 B- and T-cell epitopes and evaluation of humoral and cellular immune responses in BALB/c mice.

BACKGROUND: Recent outbreaks of foot-and-mouth disease virus (FMDV) indicate that the Southern African Territories 2 (SAT2) serotype has rapidly spread to the Middle East, West Asia, and regions bordering Russian. The spread of this strain poses a considerable global threat to the livestock industry, particularly in countries previously free of this serotype. Although less studied, co-infection with FMDV and bovine parvovirus (BPV) can also result in substantial economic losses in the cattle industry. Therefore, developing a safe and cost-effective dual-target vaccine platform is critical to addressing these challenges. Our previous findings demonstrated that BPV VP2 virus-like particles (VLPs) are highly physicochemically stable. In the present study, we developed a potential chimeric virus-like particle (cVLP) vaccine candidate designed to provide protection against both SAT2 FMDV and BPV infections. This dual-target vaccine is novel, as no such vaccine currently exists.

METHOD: In this study, neutralizing B-cell (135-174 aa) and T-cell epitopes (200-213 aa, 66-80 aa, and 21-40 aa) from SAT2 FMDV VP1 (viral protein 1; PAT/1/2012, GenBank: JX014256) were identified and inserted into selected sites (395-396 aa, 391-392 aa, 274-275 aa, and 271-272 aa) of BPV VP2 (viral protein 2; GenBank: ABC69731) sequences, which were expressed using the baculovirus expression system. We generated a panel of B-derived cVLP candidates: the T-cell epitope-deficient variant (BT0), and variants carrying one, two, or three T-cell epitopes (BT1, BT2, BT3), respectively. Immunogenicity assessments in BALB/c mice demonstrated robust humoral and cellular immune responses, evaluated via ELISA, Elispot, intracellular cytokine staining (ICS), and a VSV-SAT2-VP1 pseudovirus neutralization assay.

RESULTS: Our results indicate that displaying more SAT2 FMDV VP1 T-cell epitopes on the surface of BPV-cVLPs enhances both humoral and cellular immune responses. BT3-cVLPs exhibited strong neutralizing potential in pseudo-type neutralization assays, highlighting their promising efficacy in preventing FMDV and BPV co-infections. This innovative bivalent vaccine platform may be suitable for endemic regions and as a strategic reserve for SAT2 FMDVfree countries.