Novel recombinant bovine papular stomatitis virus expressing foot and mouth disease virus-like particles elicits protective levels of neutralizing antibodies in cattle

Foot-and-mouth disease (FMD) remains a major burden in endemic regions, where inactivated vaccines are constrained by cost, short duration of immunity, cold-chain dependence, and high-containment manufacturing. Here, we engineered a recombinant bovine papular stomatitis virus (rBPSV) expressing the FMDV A24 Cruzeiro capsid precursor P1-2A together with an attenuated 3C protease (3C ^{pro L127P} ). Infection of ovine fetal turbinate (OFTu) cells resulted in robust capsid protein expression and assembly of abundant 25-30 nm icosahedral virus-like particles (VLPs). Intramuscular immunization of two BPSV-seropositive calves with rBPSV (10 ⁷ TCID ₅₀ on days 0, 21 and 35) induced strong anti-FMDV humoral responses. By day 28, liquid-phase blocking ELISA (LPBE) titers exceeded laboratory defined protective threshold (≥1.9 log ₁₀ ), and homologous neutralizing titers against A24 Cruzeiro surpassed the threshold associated with protection (≥1.36 log ₁₀ ). Intra-serotypic cross-neutralization was observed against A/Argentina/2001, whereas no neutralization was detected against heterologous serotype O ₁ Campos. Pre-existing anti-BPSV antibodies did not prevent induction of neutralizing responses. These findings establish first proof-of-concept that BPSV can serve as a cattle-adapted vector platform for delivery of FMDV VLPs and other heterologous antigens.