Increased antigenic broadness in the adaptive humoral immunity elicited by different Foot and Mouth Disease vaccine regimes against heterologous viral strains

MIRAGLIA, M. CRUZ; BARRIOS-BENITO, MELANI; GALDO-NOVO, SABRINA; TAFFAREL, ANA; BUCAFUSCO, DANILO; CAPOZZO, ALEJANDRA VICTORIA; BORCA, M. V.; PEREZ-FILGUEIRA, DANIEL MARIANO

Kruger Park

Simposio; IVIS 2023 - 13th International veterinary immunology symposium; 2023

Foot-and-mouth disease (FMD) is one of the WOAH notifiable diseases due to its potential for rapid spread among domestic and wildlife biungulates, with severe economic impacts. Its etiological agent, the FMD virus (FMDV) is a small non-enveloped positive-stranded RNA virus with high antigenic variability in its capsid proteins. FMDV vaccines may prevent clinical FMD after infection with homologous strains, however its protective ability is usually modest against heterologous strains. This study analysed if increased heterologous virus neutralization may be achieved among serotype O FMDV strains, when immunization is performed using heterotypic FMDV isolates, particularly after revaccination, increasing of the antigenic payload or including additional FMDV strains in the vaccine formulation. Naïve cattle were immunized with a set of seven FMDV vaccines with different strain composition and antigenic payload. Each experimental group (n=3) received three immunizations at 0, 28 and 56 days post-primary vaccination to test the effect of revaccination and serum samples were taken at different time-points up to 70 days after initial vaccination. Immune sera were tested by a virus-neutralizing test (VNT) against six serotype O FMDV strains from the same topotype as the vaccinal strain (O1/Campos) and from other topotypes from South-East Asia. After the second revaccination, the heterologous neutralizing capacity was improved particularly in vaccines containing the O1/Campos strain, as monovalent (high payload), bivalent o trivalent formulations against most of FMDV strains tested. High payload O1/Campos monovalent vaccines reached significant neutralizing titres against heterologous strains faster than lower payload formulations. Interestingly, two strains isolated during the outbreak (O Ecu 46/10 and O Ecu 56/10) presented very different responses, indicating that even subtle differences in capsid proteins, may impact in the ability of the immune sera to neutralize the infective FMDV.