Immunogenicity and Protection against Foot-and-Mouth Disease Virus in Swine Intradermally Vaccinated with a Bivalent Vaccine of Foot-and-Mouth Disease Virus Type O and A

Abstract

Following the worst outbreak of foot-and-mouth disease (FMD), a highly contagious disease in cloven-hoofed animals caused by the FMD virus, from November 2010-April 2011, the Korean government enforced a mandatory vaccination policy. A bivalent (FMD type O and A; O + A) vaccine has been recently implemented. Although the FMD outbreak was suppressed by vaccination, the intramuscular (IM) injection presents side effects. Therefore, improving FMD vaccine quality is necessary. Here, we investigated the side effects and immune efficacy of the O + A bivalent vaccine using two different routes of administration: intradermal (ID) and IM. To compare the immune efficacy of the two inoculation routes, virus neutralization titers and structural protein (antigen) levels were measured. The protective efficacy of ID vaccines was confirmed using two viruses (FMDV O/AS/SKR/2019 and A/GP/SKR/2018) isolated in the Republic of Korea. Serological analysis revealed that both animals administered by ID and IM injections exhibited equal immune efficacy. A virus challenge test in the target animal (swine) revealed no (or extremely low) clinical symptoms. Swine in the ID injected group exhibited no side effects. In conclusion, we suggest that the ID route of vaccination is an effective alternative to the existing IM route, which is associated with more frequent side effects.

Keywords: foot-and-mouth disease; intradermal vaccination; type A; type O.

Figure 1

Neutralizing antibodies against various FMDV strains induced in intradermally vaccinated swine. The test vaccine was administered to swine at 15 µg O PA-2 + A22 Iraq antigen, ISA207 (oil-based emulsion, 50%, W/O/W), 10% Al(OH)3, and 1% Saponin. (a) Viral Neutralization (VN) titers against FMDV O strains; (b) VN titers against FMDV A strains.

Figure 2

Comparison of serological response after vaccination of guinea pigs with ID and IM vaccine. The test vaccine was administered to guinea pigs at one-tenth dose of O PA-2 + A22 Iraq antigen for pig use, ISA207 (oil-based emulsion, 50%, W/O/W), 10% Al(OH)3, and 1% Saponin. The negative control group was administered the test without vaccine. The IM group was inoculated with 0.2 mL/dose of vaccine and ID group was inoculated with 0.05 mL/dose of vaccine. Serum sampled from guinea pigs at 0, 7, 14, 21, 28, and 35 dpv was analyzed via SP antibody ELISA and VN assay. (a) Percentage inhibition (PI) value of FMDV type O SP ELISA in individuals (The dashed lines are positive value.). (b) VN titers against the FMDV O PA 2 strain. (c) Percentage inhibition (PI) value of FMDV type A SP ELISA in individuals (The dashed lines are positive value.). (d) VN titers against FMDV A22 Iraq strain. The dotted lines in SP-ELISA results indicate 50% inhibition, the positive threshold in the test. The dotted lines in VN test show 1.65 log VN titers. IM: intramuscular injection; ID: intradermal injection; the datasheets are the mean ± SEM; statistical analyses were performed using two-way ANOVA; ns; *, p < 0.05; **, p < 0.01; ***, p < 0.001; and ****, p < 0.0001.

Figure 3

Comparison of serological response after vaccination of swine with IM and ID vaccine. The test vaccine was administered to swine at 15 µg O PA-2 + A22 Iraq antigen, ISA207 (oil-based emulsion, 50%, W/O/W), 10% Al(OH)3, and 1% Saponin. A negative control group was administered the test without vaccine. The IM group was inoculated with 0.2 mL/dose of vaccine and ID group was inoculated with 0.5 mL/dose of vaccine. Serum sampled from swine at 0, 7, 14, 21, 28, and 35 dpv was analyzed via SP ELISA and VN test. (a) Percentage inhibition (PI) value of FMDV type O SP ELISA in individuals. (b) VN titers against O-PA2 strain. (c) Percentage inhibition (PI) value of FMDV type A SP ELISA in individuals. (d) VN titers against A22 Iraq strain. IM: intramuscular injection; ID: intradermal injection; the datasheets are the mean ± SEM; statistical analyses were performed using two-way ANOVA; *, p < 0.05; **, p < 0.01; ***, p < 0.001; and ****, p < 0.0001.

Figure 4

Clinical scores and FMDV RNA levels in swine immunized and VN titer after contact infection with donor swine inoculated with the O/AS/SKR/2019 strain. After vaccination, the swine were challenged with the O/AS/SKR/2019 strain. FMDV RNA levels in nasal swabs were measured by qRT-PCR from 0 to 7 days after challenge. Serum samples from the swine at 0, 7, 14, and 21 dpv, and 0, 3, 5, and 7 dpc were analyzed via VN assay. (a) Percentage inhibition (PI) value of FMDV type O SP ELISA in individuals. (b) Percentage inhibition (PI) value of FMDV type A SP ELISA in individuals. (c) VN titers against O/AS/SKR/2019 strain. (d) The clinical scores and FMDV RNA levels in negative group. (e) The clinical scores and FMDV RNA levels in contact infection group. (f) The clinical scores and FMD virus RNA levels in ID vaccination group. ID: intradermal injection; the datasheets are the mean ± SEM; statistical analyses were performed using two-way ANOVA; *, p < 0.05; **, p < 0.01; ***, p < 0.001; and ****, p < 0.0001.

Figure 5

Clinical scores and FMDV RNA levels in swine immunized and VN titer after contact infection with donor swine inoculated with the A/GP/SKR/2018 strain. After vaccination, the swine were challenged with the A/GP/SKR/2018 strain. FMD virus RNA levels in nasal swabs were measured by qRT-PCR from 0 to 7 days after challenge. Serum samples from the swine at 0, 7, 14, and 21 dpv, and 0, 3, 5, and 7 dpc were analyzed via VN test. (a) Percentage inhibition (PI) value of type O SP ELISA in individuals. (b) Percentage inhibition (PI) value of type A SP ELISA in individuals. (c) VN titers against O/SA/SKR/2019 strain. (d) The clinical scores and FMD virus RNA levels in negative group. (e) The clinical scores and FMD virus RNA levels in contact infection group. (f) The clinical scores and FMD virus RNA levels in ID vaccination group. ID: intradermal injection; the datasheets are the mean ± SEM; statistical analyses were performed using two-way ANOVA; *, p < 0.05; **, p < 0.01; ***, p < 0.001; and ****, p < 0.0001.

Figure 6

Pathologic lesion of an injection site following administration of the ID and IM bivalent vaccine (O PA-2 + A22 Iraq). After vaccination of five swine with ID and IM bivalent vaccine, the pathologic lesion of injection sites was checked. (a) The ID vaccination group; (b) The IM vaccination group (The marked red boxes are the part of the side effects.).