Cryptococcus neoformans is a major pathogen in immunocompetant as well as immunocompromised patients including those with AIDS in both the developed as well as the developing world. Our long-term objective of our translational work is to provide novel diagnostics and thereapeutics as well as to understand the pathophysiology of fungal infections in human patients with an emphasis on C. neoformans. 1) Cryptococcosis in previously normal patients. Cryptococcus neoformans causes approximately 1-3000 cases of meningitis per year in non-HIV populations in the U.S. and have an attributable mortality of approximately 30%. We have currently recruited approximately 90 patients with both meningoencephalitis and pulmonary disease. The protocol uses the latest in immunological and genetic methods and is divided in two parts: 1) to characterize and apply novel therapeutics to the acute disease to improve outcomes and 2) identify genetic and immunological risk factors involved in susceptibility to the disease. Since the immunology of brain infections requires both specialized understanding and methodology, collaborations with the neuroimmunological diseases unit of NINDS have facilitated this work. These studies have identified novel biomarkers of disease severity including sCD26/T-cell ratios and neurofilament light chain 1 (NFL1) that can be used to track and guide therapy both in infectious diseases such as cryptococcal meningitis as well as inflammatory diseases such as multiple sclerosis. In addition, we have used immunophenotyping of cerebrospinal fluid of patients in the NIH clinical center to identify a new neuroinflammatory disorder of cryptococcal meningitis that explains much of the mortality of the disease and has led to new approaches that have markedly reduced the mortality and morbidity of the disease. 2) Regulation of autophagy by MTOR: Autophagy is a pro-survival mechanism in fungi such as cryptococcus whereby the cell recycles nutrients that are then used to facilitate growth and renewal during starvation. Autophagy has also been adapted by higher organisms such as humans to process molecules such as inflammatory cytokines that help to fight disease but can also cause autoimmune syndromes. The target of the drug, rapamycin (TOR) is a sensor of cellular stress in cryptococcus and is key to the transduction of so-called danger signals in the immune system of humans whereby the host senses invading pathogens and augments the inflammatory response. In our studies, we identified a novel regulatory pathway whereby TOR in Cryptococcus regulates autophagy to increase its ability to respond to the host immune system and survive in the nutrient-restricted environment of the brain. In addition, in collaboration with G. Azul of LCID, we extended this new regulatory system to mammalian immunity to characterize some of the autoinflammatory phenomenon in a newly described cohort of patients with gain-of-function mutations in a gene, PIK3CD that conveys TOR overactivity, leading to lymphoproliferation and autoimmunity. In addition, novel biomarkers developed during this research will allow functionally-driven therapeutic monitoring of these and other patients with TOR-related diseases as they are treated with drugs such as rapamycin.
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