Cryptococcus neoformans is an encapsulated budding yeast that causes a life-threatening illness in immunocompromised individuals, such as patients with AIDS, organ transplant recipients, and those treated with immunosuppressive therapies. Although the infection starts in the lung, cryptococcosis commonly presents as meningoencephalitis, which is one of the most common infections of the central nervous system and the leading cause of death in HIV-infected individuals. Hematogenous dissemination of C. neoformans from the lung to the brain is believed to be the most critical step in the progression of cryptococcal meningoencephalitis. How it happens, however, remains poorly understood because of the technical challenge of in vivo studies. C. neoformans is a facultative intracellular pathogen that can survive in phagocytes. Our preliminary study has provided direct evidence that C. neoformans is engulfed in the lung and subsequently disseminate to the blood within phagocytes. As neutrophils are the most abundant phagocytes in the bloodstream and have been shown to be recruited to the infected lung for phagocytosis of the yeast cells, we have developed a novel in vivo phagocytosis model to study the migration of neutrophils containing ingested C. neoformans using intravital microscopy. Based on our preliminary data showing that considerable numbers of neutrophils containing C. neoformans roll/crawl and adhere to brain vasculature after infection, we hypothesize that neutrophils mediate brain dissemination of C. neoformans by nonlytic exocytosis of the fungus and direct cell-to-cell spread of the intracellular fungus from adherent infected neutrophils to endothelial cells in the brain vasculature. We will test the hypothesis in vitro as well as in vivo by addressing the following aims using intravital microscopy and other advanced approaches: (1) Investigate migration of neutrophils harboring ingested C. neoformans from the lung to the brain vasculature; (2) Characterize nonlytic exocytosis of C. neoformans by neutrophils and the BBB crossing of the yeast cells via a direct cell-to-cell spread from adherent infected neutrophils to endothelial cells in the brain vasculature. The proposed studies will provide unique insights into brain dissemination of C. neoformans, facilitating the development of novel prevention and therapeutic strategies.
Cryptococcus neoformans is a pathogenic fungus that causes fatal meningoencephalitis worldwide. Dissemination of the organism from the infected lung to the brain is a critical step leading to meningoencephalitis. Understanding the mechanism(s) involved in brain dissemination of this organism is fundamental to our knowledge of the pathogenesis of this disease. The knowledge gained from this proposed studies will be helpful in the development of novel strategies for prevention and treatment of cryptococcal meningoencephalitis. Therefore, the proposed research is relevant to the part of NIH's mission that pertains to developing fundamental knowledge that will help to reduce human illness.
| Diago-Navarro, Elizabeth; Calatayud-Baselga, Isabel; Sun, Donglei et al. (2017) Antibody-Based Immunotherapy To Treat and Prevent Infection with Hypervirulent Klebsiella pneumoniae. Clin Vaccine Immunol 24: |
| Sun, Donglei; Zhang, Mingshun; Liu, Gongguan et al. (2016) Intravascular clearance of disseminating Cryptococcus neoformans in the brain can be improved by enhancing neutrophil recruitment in mice. Eur J Immunol 46:1704-14 |
| Sun, Donglei; Shi, Meiqing (2016) Neutrophil swarming toward Cryptococcus neoformans is mediated by complement and leukotriene B4. Biochem Biophys Res Commun 477:945-951 |
| Sun, Donglei; Zhang, Mingshun; Liu, Gongguan et al. (2016) Real-Time Imaging of Interactions of Neutrophils with Cryptococcus neoformans Demonstrates a Crucial Role of Complement C5a-C5aR Signaling. Infect Immun 84:216-29 |
