Cryptococcus neoformans and C. gattii cause life threatening cryptococcal meningoencephalitis, the most common fungal infection of the central nervous system in the world today. The 12-month mortality rate for individuals with cryptococcal meningoencephalitis is 60% even with the current antifungal treatment. Developing vaccines against cryptococcosis to treat high risk patients remains one of the most urgent and challenging goals to combat this devastating fungal infection. So far, inactivated whole cell vaccines and recombinant protein subunit vaccines are being investigated in preclinical studies. Both inactivated whole cell vaccines or protein subunit vaccines have issues (e.g., safety, technical, cost, and efficacy concerns) and none have made it to clinical trials yet. The emerging and clinically proven vaccine technology based on delivering stabilized mRNAs encoding immunogens packaged in lipid nanoparticles (LNPs) has not been developed for any bacterial or fungal infections. Here we will investigate this technology to develop vaccines against cryptococcal infections. Our research group has experience with liposomes and nucleic acids, and have been working with together on dectin-decorated liposomes for targeted antifungal drug delivery for years. The targeted antifungal delivery with dectin-decorated liposomes has shown great promise in both in vitro and animal models. We have also experience with vaccination against Cryptococcus infection using inactivated cryptococcal mutants. Capitalizing on these experiences, our goal is to produce a highly effective mRNA LNP vaccine for cryptococcosis. We have incorporated several new strategies into our novel mRNA vaccine design. For example, encoded immunogens to be tested are selected based on prior demonstrated efficacy of recombinant proteins to be protective immunogens, high in vivo transcript abundance, extracellular localization, and their roles in fungal pathogenesis. Because each extracellular protein will be produced from an mRNA in the host cell, it will be glycated, and hence, more closely resemble proteins produced by the fungus C. neoformans as compared to recombinant proteins produced by E. coli. To meet our goal, we propose to accomplish the following two specific aims: (i) Construct LNPs carrying the mRNAs encoding distinct candidate C. neoformans protein immunogens. (ii) Test the immunogenicity and durable host protection provided by each mRNA nanoparticle vaccine and a combinatorial vaccine in mouse models of cryptococcosis. Completion of this proposal will likely provide a successful platform for mRNA vaccine against cryptococcosis and in the future other fungal diseases. The exploratory nature of the proposed work and the potential impact it could have on our ability to fight this and other deadly fungal pathogens make this application perfectly fit for the R21 mechanism.