To date, many kinds of classical swine fever (CSF) vaccines have been developed to protect against this disease. However, the efficacy of these vaccines to protect the pig against field CSF strains needs to be considered, based on circulating strains of classical swine fever virus (CSFV). Materials and Methods: Recombinant E2-CSFV protein produced by baculovirus/insect cell system was analyzed by western blots and immunoperoxidase monolayer assay. The effect of CSFV-E2 subunit vaccines was evaluated in experimental pigs with three genotypes of CSFV challenge. Anti-E2 specific and neutralizing antibodies in experimental pigs were analyzed by blocking enzyme-linked immunosorbent assay and neutralization peroxidize-linked assay. Results: The data showed that CSFV VN91-E2 subunit vaccine provided clinical protection in pigs against three different genotypes of CSFV without noticeable clinical signs, symptoms, and mortality. In addition, no CSFV was isolated from the spleen of the vaccinated pigs. However, the unvaccinated pigs exhibited high clinical scores and the successful virus isolation from spleen. These results showed that the E2-specific and neutralizing antibodies induced by VN91-E2 antigen appeared at day 24 after first boost and a significant increase was observed at day 28 (p<0.01). This response reached a peak at day 35 and continued until day 63 when compared to controls. Importantly, VN91-E2 induced E2-specific and neutralizing antibodies protected experimental pigs against high virulence of CSFVs circulating in Vietnam, including genotype 1.1, 2.1, and 2.2. Conclusion: These findings also suggested that CSFV VN91-E2 subunit vaccine could be a promising vaccine candidate for the control and prevention of CSFV in Vietnam.

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African swine fever (ASF) is currently considered the serious contagious disease of the swine in-dustry worldwide. The feed and feed ingredients have been recognized as a potential risk factor for Af-rican swine fever virus (ASFV) transmission. No commercial vaccines and effective drugs against ASFV are available to date. This study aimed to examine the antimicrobial SALTEC™ 512, a formal-dehyde-based additive, at an application rate of 1.0; 2.0; and 3.0 kg/t feed against ASFV in complete swine feed. The effect of SALTEC™ 512 was evaluated by a contaminated ASFV feed assay. Our study reveals that SALTEC™ 512 inactivated ASF/VN/Pig/Hue/1270 strain in complete swine feed at an inclusion rate of 1.0 kg/t feed on Day 1 post inoculation. The most effective action was noticed at an inclusion level of 3.0 kg/t feed on Day 7 post inoculation. The antiviral activity of SALTEC™ 512 against ASF/VN/Pig/Hue/1270 was dose and time-dependent. Overall, SALTEC™ 512 may be a po-tential additive to reduce the risk of ASFV transmission via feed contamination.