Inhibition of African swine fever virus replication by β-glucan

Background: African swine fever (ASF) is one of the most important diseases in pigs because of its effects on all ages and breeds. To date, the commercial vaccines and drugs for prevention of ASF are lacking in the market and the survival of ASFV in various environmental, farm and or feed matrices has allowed the virus to remain, and it may cause new outbreaks in the pig population. Besides biosecurity and animal husbandry management practices, the improvement of the host immune responses is critical to control, manage and prevent ASF.
Aim: In this study, we investigated the protective role of β-glucan against ASFV infection using a porcine alveolar macrophage (PAM) model. 
Methods: The effects of β-glucan on cell proliferation were evaluated by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The potential effects of β-glucan against a field ASFV strain isolated in Vietnam, were further examined by real-time PCR and hemadsorption assays. The IFN-α and IL-6 protein production induced by β-glucan was determined using a sandwich enzyme-linked immunosorbent assay (ELISA).
Results: Our results demonstrated that the β-glucan additive possessed an immune stimulus factor against ASFV. Specifically, protection of PAMs against ASFV infection in vitro was observed at 12 h (p < 0.05) at the tested doses (30 and 50 µg/ml) as induced by incubation with β-glucan for 2 h. These effects remained until 24 h after post-infection. Additionally, at high dose (50 µg/ml), pre-treatment with the β-glucan statistically increased the expression levels of IFNα and IL-6 when compared to un-treated groups or only ASFV infection. 
Conclusion: Together, these findings indicated that the β-glucan may protect the host against ASFV infection via the multiple cellular immune mechanisms.