Project Summary Giardia lamblia, a protozoan CDC category B priority pathogen, is an important cause of diarrheal disease with hundreds of millions of annual cases worldwide. In the United States, G. lamblia is one of the two most common causes of outbreaks of parasitic disease, with prevalence rates of 1-7%. Symptomatic giardiasis is characterized by diarrhea, epigastric pain, nausea, vomiting, malabsorption and malnutrition, especially in children. Long-term sequelae are common and can persist despite apparently successful treatment. Importantly, infection can be initiated by ingestion of fewer than ten cysts, demonstrating that G. lamblia is highly contagious and a credible threat to the safety of public water supplies and health. Trophozoites, the disease-causing forms of the parasite, colonize the lumen of the small intestine and attach to the epithelium. Infection is typically self-limiting, indicating that effective immune defenses exist. Despite the clinical importance of G. lamblia, no preventive medical strategies are available. Prior preclinical studies have shown that immunization with individual surface antigens can confer partial protection against G. lamblia infection in mice and gerbils, but protection is not as effective as prior infection with the parasite, suggesting that single antigens may not be sufficient to induce optimal protection. Multi-antigen immunizations can be done with live pathogen vaccines, but the necessary attenuation has not been achieved for G. lamblia and may not be possible due to the predictably compromised ability to colonize the intestine. As an alternative, we propose a nanoparticle-based vaccine, constructed from the membranes of G. lamblia strains, which enables effective multi-antigen mucosal immunization without concerns about adverse effects due to live microbe exposure. The resulting nanoparticle vaccines offer several distinct advantages: i) delivery of multi-antigenic material present on the pathogen surface, ii) stability and homogeneous sizing for effective transport in vivo and efficient uptake into antigen-presenting cells, and iii) tunable immunological biasing by loading the core with suitable adjuvants for controlled release. Therefore, our overall objective is to develop G. lamblia membrane- coated nanoparticles as a novel mucosal vaccination strategy against giardiasis. We will systematically fabricate different nanovaccine formulations with native pathogen membranes and test them for immunogenicity and protective capacity in relevant animal models of giardiasis. This project brings new ideas and approaches from the field of nanotechnology to the prevention of giardiasis, a highly contagious and clinically important but largely neglected diarrheal disease. Importantly, our innovative strategy overcomes the challenges associated with identifying single protective antigens or with using non-native, chemically modified forms of the target pathogen, thereby greatly improving induction of ...