DESCRIPTION (APPLICANT'S ABSTRACT): Glucans are natural product polymers of glucose, which are produced by fungi, certain bacteria and plants. Glucans have demonstrated the ability to stimulate immunity and increase resistance to infectious challenge following systemic administration, i.e., N, IP, IM or SQ. As natural products, glucans are found as fiber in the normal diet. Additionally, glucans have been identified as components of Chinese, Japanese and Indian traditional medicines. Recently, several dietary supplements have appeared on the market which are reported to contain glucan. The manufacturers have inferred from the scientific literature that dietary supplementation with glucans will have beneficial effects comparable to those observed with systemic administration. The development of a dietary supplement which could increase immunocompetence and enhance resistance to common infections would be of significant benefit to human health. However, the evidence that dietary supplementation with glucans will enhance immunity is limited and controversial and there is no evidence that these supplements will increase resistance to common infectious diseases. The objectives of this R21 exploratory research program are to determine whether dietary supplementationwith glucan will modulate immune function and, more importantly, whether oral glucans will increase resistance to common infectious diseases. There are two specific aims. First, we will characterize the local and systemic immunomodulation associated with dietary supplementation of glucan. Second, we will determine whether oral administration of (1--3)-(3-D-glucans will enhance resistance to challenge with the respiratory pathogens, Streptococcus neumoniae or murine adapted influenza A/PR8/34 HIM virus. At the successful conclusion of this research e will have established what, if any, effect dietary supplementation with glucan has on modulating immunocompetence arid whether oral glucans will increase resistance to infectious diseases.