Serological Conversion through a Second Exposure to Inactivated Foot-and-Mouth Disease Virus Expressing the JC Epitope on the Viral Surface

Figures

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  Figure 1. Characteristics of the TWN-R and TWN-JC. Schematic diagram of the TWN-R and TWN-JC genomes (A,B). TWN-JC is a novel vaccine candidate that has a JC epitope inserted into the TWN-R strain. TWN-R, which has the TWN P1 genome and O1manisa backbone, and TWN-JC, which has the VP1 140–160 linear B-cell epitope of the JC strain inserted into the VP1 GH loop region of TWN-R. Comparison of viral replication between TWN-R and TWN-JC in vitro. Three types of cells (ZZ-R 127, LFBK, and BHK-21) were infected at multiplicity of infection (MOI) of 0.01, and virus growth was measured at 0, 2, 4, 8, 12, 18, and 24 h post-infection (C). Transmission electron microscope (TEM) imaging of TWN-R (D) and TWN-JC (E).

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  Figure 2. Protection against serotype O topotype viruses mediated by vaccination with TWN-R or TWN-JC in mice. Mice were vaccinated with TWN-R or TWN-JC at 1/10, 1/40, 1/160, or 1/640 of the dose used in pigs and challenged with three virus topotypes (ME-SA, SEA, and Cathay) at 7 dpv (A). The survival rate (B) and body weight (C) of the mice were measured for a further 7 days post-challenge.

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  Figure 3. Immunogenicity of the recombinant virus in guinea pigs. Guinea pigs (n = 5) were vaccinated with 7.5 µg of inactivated antigen mixed with ISA 206, aluminum hydroxide gel adjuvant, and saponin. Sera were collected at 0, 14, 28, and 42 dpv, and the animals were boosted at 21 dpv. Schematic diagram of the experimental strategy (A), Structure Protein (SP) ELISA results generated using serum from guinea pigs vaccinated with TWN-R or TWN-JC (B), and the homologous (C) and heterologous neutralizing antibody titers against TWN (D), JC (E), VIT (F), and BE (G) in guinea pigs vaccinated with TWN-R or TWN-JC. A percent inhibition (PI) value > 50 was considered the cutoff for a positive reaction (blue dotted line). VN titers (log10) > 1.65 were regarded as positive (red dotted line). p values of p < 0.05 (*) and p < 0.01 (**).

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  Figure 4. Immunogenicity of the recombinant virus in pigs. Pigs (n = 5) were vaccinated with 15 µg of inactivated antigen mixed with ISA 206, aluminum hydroxide gel adjuvant, and saponin. Sera were collected at 0, 7, 14, 21, 28, 42, and 56 dpv, and the animals were boosted at 28 dpv. Schematic diagram of the experimental strategy (A), Structure protein (SP) ELISA results generated using serum from pigs vaccinated with TWN-R or TWN-JC (B), and the homologous (C) and heterologous neutralizing antibody titers against TWN (D), JC (E), VIT (F), and BE (G) in pigs vaccinated with TWN-R or TWN-JC. A PI value > 50 was considered the cutoff for a positive reaction (blue dotted line). VN titers (log10) > 1.65 were regarded as positive (red dotted line). p values of p < 0.05 (*).

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  Figure 5. Comparison of specific serological changes associated with the different topotypes in guinea pigs (n = 5) and pigs (n = 5). The fold change associated with the different topotypes were compared using the prime (14 dpv) and boost (42 dpv) serum samples obtained from the guinea pigs (A,C,E,G) and the prime (28 dpv) and boost (56 dpv) serum samples obtained from the pigs (B,D,F,H). The fold change of the boost VN titer was normalized to prime VN titer. p values of p < 0.05 (*) and p < 0.01 (**).

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  Figure 6. Cytokine secretion in pigs (n = 5) vaccinated with TWN-R or TWN-JC. The serum levels of IFNγ (A), IL-12B (B), IL-2 (C), IL-7 (D), and IL-15 (E) were detected post-vaccination using an ELISA. The 7, 28, and 56 dpv serum samples obtained from pigs immunized with TWN-R or TWN-JC were tested and normalized to serum before vaccination. p values of p < 0.05 (*).