Mecanismos de resposta imune à infecção por Cryptococcus gattii e sua evasão do sistema imunológico do hospedeiro

Abstract

Cryptococcosis is a fungal infection caused by species of the genus Cryptococcus. It is acquired through inhalation of basidiospores or dehydrated yeast. Besides being associated with cell conditions of immunodepression caused by C. neoformans, it can cause primary disease in healthy host, by the fungus of the same genus, C. gattii. The disease begins in the alveolar spaces of the lung by the confrontation of yeasts with macrophages and can disseminate to other tissues, especially the CNS. For development in the adverse conditions of the human host, the cells yeasts of the genus Cryptococcus exhibit virulence factors necessary for their survival, as components of the capsule, the cell wall, the thermotolerance, and enzymes and ions production. Currently, the resistance of C. gattii to drugs available on the market is increasing, resulting in the need to deeply know of the mechanisms by which fungi can evade from the host's immune system, so this work aims to conduct a study on the mechanisms of host immune response against the C. gattii yeasts and their strategies used for infection and evasion from the human immune system. The defense mechanisms against fungi are numerous, ranging from those present from birth, to the most sophisticated, being acquired during infection. Some evidence shows that the main mechanisms still are essential answers to control this fungus, through the activation of phagocytic cells and T and B lymphocytes by cytokines that mediate the immune system. Although humoral immunity has been poorly studied in the past decades, studies show that antibodies have important functions during cryptococcal infection. Relevant results were also obtained in studies of virulence factors of C. gattii, mainly related to urease. However, more research should be required to investigate each stage of infection by C. gattii, thus enabling the choice of the most appropriate therapy strategies for construction and vaccines against this pathogen.