NEUTRALIZING IMMUNE RESPONSE IN WEANING PIGS AFTER VACCINATION WITH FOOD AND MOUTH DISEASE VACCINE

Abstract

PD₅₀ of Foot-and-mouth disease (FMD) vaccine is a dose-determining index of vaccine antigen that protects 50% of vaccinated animals against a challenge with virulent FMD virus. FMD vaccines classified into standard potency FMD vaccine (>3PD₅₀) and higher potency vaccine>6PD₅₀). The FMD >6PD50 vaccine, in addition to its ability to induce a faster, stronger and longer lasting immune response than the FMD >3PD50 vaccine, can also enhance the protective effect against FMDV strains of different topotypes. The study aimed to compare the immune response in pigs to 2 types of Foot-and-mouth disease vaccines >3PD50 and >6PD50, based on neutralizing antibody titers, to clarify the difference in the protective efficacy of the two vaccines to the foot-and-mouth disease virus strains isolated in Vietnam, serving the use of vaccines in the prevention of Foot-and-mouth disease. The results showed that there is a difference in immunogenicity between the two FMD vaccines, >6PD₅₀ and >3PD₅₀. Pigs vaccinated with FMD >6PD₅₀ had a positive rate and neutralizing antibody titer against FMD virus strains belonging to the topotype O/ME-SA/PanAsia, O/SEA/Mya 98 and O/ME-SA/Ind 2001e, isolates in Vietnam, were statistically significantly higher than pigs vaccinated with FMD 3PD₅₀ (P<0.05). FMD vaccine with a high PD₅₀ value (>6PD₅₀) can induce high neutralizing immunity, overcoming the differences in the topology of FMD virus field and vaccine strains. The result of the study could be used for vaccination to control FMD.