Foot and Mouth disease vaccines induce primary immune responses in calves with preexisting maternal immunity

BUCAFUSCO, DANILO; DI GIACOMO, SEBASTIÁN; LAVORIA, MARIA; PEGA, JUAN FRANCO; PÉREZ FILGUEIRA, MARIANO; CAPOZZO, ALEJANDRA

Jerez de la Frontera

Congreso; Appliance of science in the progressive control of FMD; 2012

The European Commission for the control of Foot-and-Mouth disease (EuFMD)

Maternal immunity has been associated with a diminished response of calves to vaccination. The aim of this study was to evaluate the immunogenicity of the current inactivated oil-based Argentinean FMD vaccine in calves with or without maternally-derived antibodies (MdAb). Materials and methods Thirteen calves with high MdAb and twelve without measurable FMDV-antibodies were vaccinated twice (day 0 and 35) with a commercial tetravalent vaccine. Animals were bled at the beginning of the study and at 7, 21, 35 and 55 days post vaccination (dpv). Sera were assessed for specific antibodies against O1 Campos strain by liquid phase blocking ELISA (LpBELISA), avidity ELISA and FMDV-specific IgM ELISA. Results All calves (12/12) without MdAb elicited specific antibodies after the first vaccination, surpassing at 21 dpv a LpBELISA titer of 2.1, that correspond to 75% expectative of protection (EPP-75). Calves with MdAb had LpBELISA titers over 2.9 at day 0, and titers were maintained over protective levels along the study. Avidity maturation profiles were different between both groups. Calves without MdAb reached high IgG-avidity levels at 35 dpv, after one vaccine dose; while two-vaccinations were required to achieve similar avidity levels in calves with MdAb. Both groups induced similar anti FMDV-IgM profile, showing that acquired immunity was equally initiated despite the presence of MdAb at the time of vaccination. Discussion Calves with high levels of MdAb immunized with an inactivated oil-adjuvanted vaccine maintained LpBELISA titers over 2.1 (EPP 75) even when MdAb had decayed. These animals elicited a primary IgM response of the same magnitude and kinetics than those without MdAb. Avidity profiles should be further explored, together with IgG-isotype responses to establish the influence of cell-mediated immunity transferred by colostrum. Vaccination of calves with MdAb allows closing the window of vulnerability created by the natural decay of maternal antibodies.