Abstract

Beta-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 gamma (IFNgamma)-producing cells. We found that soluble high molecular weight beta-glucan could increase IFNgamma-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 microg/ml gave a significant increase and a similarly high enhancement was achieved at concentrations from 3.2 to 100 microg/ml. In PRRSV-specific IFNgamma ELISPOT, soluble beta-glucan elicited increased PRRSV-specific responses at concentrations from 3.2 to 50 microg/ml, but not at 100 microg/ml, whereas insoluble beta-glucan had no effect. Soluble beta-glucan augmented the porcine cellular immune response in an antigen-independent fashion, whereas insoluble beta-glucan had no activity. This finding suggests that soluble beta-glucan may enhance innate antiviral immunity against PRRSV.