Isa 206 vg adjuvant

The experimental vaccines were prepared with the FMDV O/Boeun/SKR/2017 strain via: (i) PEG-precipitation; and (ii) heparin affinity chromatography. For the first group, the FMDV culture supernatant was treated with 7.5% (w/v) PEG 6000 (Sigma-Aldrich), stirred overnight at 4 °C, and centrifuged at 10,000× g for 30 min. After the supernatant was removed, the pellet was resuspended in Tris-KCl buffer (20 mM Tris-HCl, 300 mM KCl, pH 7.6) and adjusted to a concentration of 15 μg/mL. For the second group, the heparin column eluted antigens were concentrated to 15 μg/mL using a 10-kDa cutoff Centricon Plus-70 centrifugal unit (Merck Millipore). Saponin (Sigma-Aldrich) and aluminum hydroxide gel (General Chemical, Parsippany, NJ, USA) were added to these two kinds of antigens, and the ISA 206 VG adjuvant (Seppic, Paris, France) pre-warmed at 30 °C was then added in a ratio of 1:1. After the mixtures were incubated at 20 °C for 1 h in a water bath with blocked light, they were stored at 4 °C until use.

The antigens for type O and A, as described in Section 2.7, were mixed with 1% saponin (Sigma-Aldrich) and 10% aluminum hydroxide gel (General Chemical, NJ, USA) to prepare a bivalent vaccine. The ISA 206 VG adjuvant (Seppic, Paris, France) pre-warmed at 30 °C was then added at a ratio of 1:1, resulting in 1 mL/dose or 2 mL/dose including 15 µg of the types O and A. After the mixtures were incubated at 20 °C for 1 h in a water bath without light exposure, they were stored at 4 °C until use. A total of 10 guinea pigs weighing 230–250 g was divided into two groups. Animals in the first group (n = 5) were inoculated intramuscularly at a volume of 1/10 of 1 mL/dose, and those in the other group (n =5) were inoculated intramuscularly at a volume of 1/10 of 2 mL/dose. Blood samples of each guinea pig were collected at 0, 7, 14, 21, 28, 56, and 84 days post-vaccination (dpv). VN titers with sera at 28 dpv were investigated against homologous and heterologous viruses using several topotypes of viruses. For serotype O viruses, O/Gimje/SKR/2016 and O/Jincheon/SKR/2014 belong to the SEA topotypes. The two ME-SA topotypes of the viruses were O/Anseong/SKR/2019 and O/VIT/2013. Cathay’s topotypes of the viruses were Taiwan 97. For serotype A viruses, the A/ Pocheon/SKR/2010, A/Gimpo/SKR/2018 (SEA-97), A22 Iraq (A22), and A/Nepal/12/2017 (G-VII) belong to Asia topotypes (Figure S1).