Requirements for improved vaccines against foot-and-mouth disease epidemics

Abstract

Inactivated foot-and-mouth disease (FMD) vaccines are currently used worldwide. With the emergence of various FMD virus serotypes and subtypes, vaccines must become more suitable for field-based uses under the current circumstances in terms of the fast and proper selection of vaccine strains, an extended vaccine development period for new viruses, protecting against the risk of virus leakage during vaccine manufacture, counteracting the delayed onset of immune response, counteracting shorter durations of immunity, and the accurate serological differentiation of infected and vaccinated animals and multiple vaccination. The quality of vaccines should then be improved to effectively control FMD outbreaks and minimize the problems that can arise among livestock after vaccinations. Vaccine improvement should be based on using attenuated virus strains with high levels of safety. Moreover, when vaccines are urgently required for newly spread field strains, the seed viruses for new vaccines should be developed for only a short period. Improved vaccines should offer superior immunization to all susceptible animals including cattle and swine. In addition, they should have highly protective effects without persistent infection. In this way, if vaccines are developed using new methods such as reverse genetics or vector vaccine technology, in which live viruses can be easily made by replacing specific protective antigens, even a single vaccination is likely to generate highly protective effects with an extended duration of immunity, and the safety and stability of the vaccines will be assured. We therefore reviewed the current FMD vaccines and their adjuvants, and evaluated if they provide superior immunization to all susceptible animals including cattle and swine.

Keywords: Development; Foot-and-mouth disease; Improvement; Vaccine.

Fig. 1

Antibody levels against the foot-and-mouth disease (FMD) virus O type in susceptible animals after FMD vaccination in the field without maternal-derived antibody during the 2010 to 2011 epidemic in Korea. (A) Antibody levels determined by enzyme-linked immunosorbent assay to viral structural proteins (SP-ELISA) after the first vaccination (or second vaccination). The second vaccination in case of pigs (tested 30-50 animals per week) were vaccinated 4 weeks after first vaccination. (B) Virus neutralizing (VN) reciprocal titers using the field strain (O/Andong/KOR/2010) two weeks after the second vaccination.

Fig. 2

Diminishment of the foot-and-mouth disease outbreaks after vaccination during the 2010 to 2011 epidemic in Korea. The arrows show the onset of vaccination.