β-Glucan enhancement of T cell IFNγ response in swine

β-Glucan has been shown to enhance anti-tumor and anti-infection functions in animals. Pigs at 4 months of age were infected with porcine reproductive and respiratory syndrome virus (PRRSV), and peripheral blood monocytes (PBMC) were isolated for the detection of interferon γ (IFNγ)-producing cells. We found that soluble high molecular weight β-glucan could increase IFNγ-producing cell frequency in a dose-dependent manner in the enzyme-linked immunospot assay (ELISPOT) in the absence of antigenic restimulation. A concentration as low as 1.6 μg/ml gave a significant increase and a similarly high enhancement was achieved at concentrations from 3.2 to 100 μg/ml. In PRRSV-specific IFNγ ELISPOT, soluble β-glucan elicited increased PRRSV-specific responses at concentrations from 3.2 to 50 μg/ml, but not at 100 μg/ml, whereas insoluble β-glucan had no effect. Soluble β-glucan augmented the porcine cellular immune response in an antigen-independent fashion, whereas insoluble β-glucan had no activity. This finding suggests that soluble β-glucan may enhance innate antiviral immunity against PRRSV.