There are seven viral serotypes of foot-and-mouth disease virus (FMDV): A, O, C, Asia 1, and Southern African Territories 1, 2, and 3 (SAT 1–3). Unlike serotype O FMDV vaccine strains, vaccine strains of serotype A FMDV do not provide broad-range cross-reactivity in serological matching tests with field isolates. Therefore, the topotype/lineage vaccine strain circulating in many countries and a highly immunogenic strain might be advantageous to control serotype A FMDV. We developed a new vaccine strain, A/SKR/Yeoncheon/2017 (A-1), which belongs to the A/ASIA/Sea-97 lineage that frequently occurs in Asian countries. Using virus plaque purification, we selected a vaccine virus with high antigen productivity and the lowest numbers of P1 mutations among cell-adapted virus populations. The A/SKR/Yeoncheon/2017 (A-1) vaccine strain has a single amino acid mutation, VP2 E82K, in the P1 region, and it is perfectly adapted to suspension culture. The A/SKR/Yeoncheon/2017 (A-1) experimental vaccine conferred high immunogenicity in pigs. The vaccine strain was serologically matched with various field isolates in two-dimensional virus neutralization tests using bovine serum. Vaccinated mice were protected against an A/MAY/97 virus that was serologically mismatched with the vaccine strain. Thus, A/SKR/Yeoncheon/2017 (A-1) might be a promising vaccine candidate for protection against the emerging FMDV serotype A in Asia.
Vaccination is one of the most effective ways of controlling and preventing foot-and-mouth disease (FMD) outbreaks. The effective prevention of this disease requires the use of high-quality vaccines to meet the criteria that enable customers to use them simply. The administration of FMD vaccines containing oil-based adjuvants in pigs can induce the formation of granuloma in the muscle of the vaccinated, which makes these vaccines a less preferable option. Therefore, it is important to establish an FMD vaccine and vaccine delivery tool that offers better immunity and safer application. This study compared the immune responses of intramuscular and needleless intradermal vaccination in pigs. When the same amount of an FMD virus (FMDV) antigen was administered to pigs, both the intradermally and intramuscularly vaccinated groups were protected completely against a challenge of the homologous FMDV, but the intramuscularly vaccinated group showed an overall higher level of neutralizing antibodies. Importantly, the formation of granuloma in muscle could be excluded in the intradermally vaccinated group. Of the oil-based adjuvants selected in this study, ISA 207 was effective in eliciting immunogenicity in intradermal vaccination. In conclusion, a new vaccine formula can be chosen for the delivery of intradermal route to exclude the possibility of local reactions in the muscle and generate protective immunity against an FMDV challenge.
Early inhibition of foot-and-mouth disease (FMD) virus (FMDV) replication in pigs is highly desirable as FMDV transmission and shedding rates are higher in pigs than in cattle. However, commercial FMD vaccines require at least 4 to 7 days postvaccination (dpv) for protection, and animals are vulnerable to heterologous viruses before acquiring high antibody levels after the second vaccination.
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