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