The protective role played by the innate immune system during early stages of infection suggests that compounds which stimulate innate responses could be used as antimicrobial or antiviral agents. In this study, we demonstrate that the Toll-like receptor-2 agonist Pam2Cys, when administered intranasally, triggers a cascade of inflammatory and innate immune signals, acting as an immunostimulant by attracting neutrophils and macrophages and inducing secretion of IL-2, IL-6, IL-10, IFN-γ, MCP-1 and TNF-α. These changes provide increased resistance against influenza A virus challenge and also reduce the potential for transmission of infection. Pam2Cys treatment also reduced weight loss and lethality associated with virulent influenza virus infection in a Toll-like receptor-2-dependent manner. Treatment did not affect the animals' ability to generate an adaptive immune response, measured by the induction of functional influenza A virus-specific CD8(+) T cells following exposure to virus. Because this compound demonstrates efficacy against distinct strains of influenza, it could be a candidate for development as an agent against influenza and possibly other respiratory pathogens.