Cryptococcal Interactions with the Host Immune System

Opportunistic pathogens have become of increasing medical importance over the last decade due to the AIDS pandemic. Cryptococcosis is not only the fourth most common fatal infectious disease in sub-Saharan Africa, but Cryptococcus is also an emerging pathogen of immunocompetent individuals. The interaction between Cryptococcus and the host's immune system is a major determinant for the outcome of disease. Despite initial infection in early childhood with C. neoformans and frequent exposure to C. neoformans within the environment, immunocompetent individuals are generally able to contain the fungus or maintain the yeast in a latent state. However, immune deficiencies lead to disseminating infections that are uniformly fatal without rapid clinical intervention. This review will discuss the innate and the adaptive immune response to Cryptococcus and cryptococcal strategies to evade the host's defense mechanisms. It will also address the importance of these strategies in pathogenesis and the potential of immunotherapy in cryptococcosis treatment.