Influenza virus infection causes contagious respiratory illness in humans and animals, and significant morbidity and mortality worldwide. Humans fail to make a universally protective memory immune response to influenza A, as Hemagglutinin and Neuraminidase, the two immune-dominant influenza A virus-encoded epitopes, undergo antigenic shift and drift, resulting in influenza A strains to which even previously infected humans are susceptible to. In the absence of a universal influenza A vaccine, prophylactic or therapeutic agent, influenza A will remain a significant threat to human health. To generate such agents, we developed a panel of Matrix Protein 2 extracellular (M2e)-specific monoclonal antibodies (MAbs). The extracellular domain of the M2-ion channel is an ideal antigenic target for a universal therapeutic agent: It is 99% conserved across influenza A serotypes, has a low mutation rate, and is essential for viral entry and replication. However, less than 20% of infected individuals generate M2e-specific antibodies in response to influenza A infection, perhaps due to M2e's small size and rarity. Thus, we seek to accomplish our long-term goal, to develop a universal prophylactic or therapeutic agent to prevent or treat influenza A infection and associated pathologies, by provision of M2e-specific MAbs, an essential component of a protective influenza A-specific immune response currently lacking in most humans. To achieve this goal, we generated seven monoclonal antibodies specific to M2e, two of which completely protect, and three of which partially protect highly influenza A virus susceptible Balb/c mice from lethal challenge. Based on these considerations, it is our central hypothesis that a cocktail of M2e-specific MAbs can prevent or ameliorate influenza A infection and associated pathology. As antibodies can mediate a variety of complementary effector functions that contribute to host protection, we hypothesize that a combination of M2e-specific MAbs capable of interference with M2-ion channel activity, elicitation of ADCC, phagocytosis and complement activation will be most effective at reducing influenza A virus replication and associated pathology, while preventing immune escape. We expect to test our central hypothesis and to achieve the objective of this application by pursuing the following three specific aims: Aim 1: to identify biological effects of MAb binding on M2e-function and viral replication in vitro; Aim 2: to develop protective and therapeutic MAb treatment regimens in vivo; and Aim 3: to dissect the individual contributions of M2e-specific MAb-dependent cytotoxicity, phagocytosis and complement activation to host protection from influenza A virus infection. To achieve our aims, we have assembled and expert team of collaborating scientists: Dr. Beeton, an expert in the ion channel function; Dr. Tompkins, an expert in animal models of human and zoonotic influenza infection, vaccination, and therapeutics, with specified M2...