Enhanced Effects of ISA 207 Adjuvant via Intradermal Route in Foot-and-Mouth Disease Vaccine for Pigs

Abstract

In South Korea, a mandatory nation-wide foot-and-mouth disease (FMD) vaccination policy is in place. However, a major side effect of the current method of intramuscular (IM) administration of oil-adjuvanted FMD vaccines is the formation of granulomas in the muscles of pigs. To address this issue, we assessed the possible application of intradermal (ID) vaccination. Initially, we compared the serological immune response in specific pathogen-free pigs inoculated with FMD vaccines formulated with eight different adjuvants, administered twice at the neck site using a syringe with a needle via the ID route. Among the formulations (water-in-oil-in-water (W/O/W), oil-in-water (O/W), and polymer nanomaterials), ISA 207 of W/O/W was the most effective in inducing immunogenicity followed by ISA 201 of W/O/W. ISA 207 was further tested in formulations of different antigen doses (12 or 1.2 μg) delivered via both IM and ID routes. All four treatments successfully protected the pigs against FMD virus challenges. To assess the feasibility of the field application of the vaccines with ISA 207, we conducted ID vaccination of conventional pigs using a needle-free device, resulting in the detection of significant levels of neutralizing antibodies. ISA 207 was shown to be superior to ISA 201 in inducing immunogenicity via the ID route. In conclusion, ISA 207 could be a suitable adjuvant for ID vaccination in terms of vaccine efficacy for FMD, allowing for alternate use of ID vaccination and subsequent reduction in the incidences of granuloma formation in the field.

Keywords: adjuvant; foot-and-mouth disease; intradermal route; protection; vaccine.

Figure 1

Comparison of SP antibodies (PI values) across nine groups using different adjuvant categories (Exp 1). (a) Comparison among the four groups, including the W/O/W formulation groups (G2, ISA 206; G3, ISA 201; G4, ISA 207) and G1 (no adjuvant). (b) Comparison among the three groups, including the O/W formulation groups (G5, Emulsigen-D; G6, Emulsigen-D with Al(OH)₃) and G1 (no adjuvant). (c) Comparison among the three groups, including the polymer nanomaterials groups (G7, Al(OH)₃; G8, IMS1313; G9, GEL 01) and G1 (no adjuvant). (d) Comparison of PI values at 8 wpv among three categories, including no adjuvant group. PI values ≥ 50% (dotted line) were considered positive for FMDV type A SP antibodies. SP; structure protein, PI; percentage inhibition, W/O/W, water-in-oil-in-water emulsion vaccines; O/W, oil-in-water emulsion vaccines; wpv, weeks post-vaccination; the datasheets are the mean ± SEM; statistical analyses were performed using one-way ANOVA; * p < 0.05.

Figure 2

Neutralizing antibody titers of SPF mini pigs at 8 weeks post-vaccination (Exp 1). (a) VN titers against the A/Iraq/24/64 strain by each group: G1, (no adjuvant), G2 (ISA 206), G3 (ISA 201), G4 (ISA 207), G5 (Emulsigen-D), G6 (Emulsigen-D with Al(OH)₃), G7 (Al(OH)₃), G8 (IMS1313), G9 (Gel). (b) VN titers against A/Iraq/24/64 strain in each category. W/O/W adjuvant (G2, ISA 206; G3, ISA 201; G4, ISA 207), O/W adjuvant (G5, Emulsigen-D; G6, Emulsigen-D with Al(OH)₃), polymer nanomaterials (G7, Al(OH)₃; G8, IMS1313; G9, GEL 01). (b) VN titers against the A/Iraq/24/64 strain categorized by adjuvant types. VN titers ≥ 1.65 log₁₀ (dotted line) are considered positive for FMDV antibodies. G, group; ID, intradermal; SPF, specific pathogen-free; W/O/W/, water-in-oil-in-water emulsion vaccines; O/W, oil-in-water emulsion vaccines; wpv, weeks post-vaccination; the datasheets are the mean ± SEM; statistical analyses were performed using one-way ANOVA; * p < 0.05; ** p < 0.01.

Figure 3

Virus excretion and clinical scores in SPF mini pigs immunized and challenged with the homologous virus (A/Iraq/24/64) (Exp 2). Nasal swabs and serum samples were collected from 0 to 10 and 13 and 16 dpc. Additionally, serum was collected at 0, 1, 2, and 3 wpv. The figure illustrates the virus excretion levels and clinical scores recorded throughout the experiment. C, challenge test group; ID, intradermal; IM, intramuscular; SPF, specific pathogen-free; dpc, days post-challenge; wpv, weeks post-vaccination.

Figure 4

SP antibody (PI) and neutralizing antibody (VN titer) of SPF mini pigs in six challenge test groups vaccinated and bled at 0, 7, 14, 21, and 28 dpv and 0–16 dpc (Exp 2). (a–e) SP antibody responses in SPF mini pig sera collected at 0, 7, 14, 21, and 28 dpv and 0–16 days dpc. (f) VN titers (log10) of serotype A/Iraq/24/64 at 4 wpv. (g,h) Comparison of vaccine injection sites sacrificed at 16 dpc. The IM injection site exhibited nodular lesions in the neck muscle, whereas the ID injection site showed redness and small swelling on the skin. PI values ≥ 50% (dotted line) were considered positive for FMDV type A SP antibodies. VN titers ≥ 1.65 log₁₀ (dotted line) were considered positive. C, challenge test group; ID, intradermal; IM, intramuscular; SPF, specific pathogen-free; SP, structure protein; PI, percentage inhibition; wpv, weeks post-vaccination; dpc, days post-challenge; the datasheets are the mean ± SEM; statistical analyses were performed using one-way ANOVA; * p < 0.05; *** p < 0.001; and **** p < 0.0001.

Figure 5

SP antibody response and neutralizing antibody response in domestic pigs’ sera at 0–8 wpv. The graphs illustrate the SP ELISA PI values and VN titers for each farm pig group (F1, ISA 207/ID/12 μg; F2, ISA 201/ID/12 μg; F3, ISA 207 adjuvant/ID/no antigen). (a) SP ELISA antibody level as measured by PI values ≥ 50% (dotted line) are considered positive for FMDV type A SP antibodies. (b) VN titers (log10) for the serotype A/Iraq/24/64 antibody values ≥ 1.65 log10 (dotted line) are considered positive for FMDV antibodies. F, farm pig group; ID, intradermal; SP, structure protein; PI, percentage inhibition; wpv, weeks post-vaccination; the datasheets are the mean ± SEM; statistical analyses were performed using one-way ANOVA; * p < 0.05; *** p < 0.001.