PAMPs and Host Immune Response in Cryptococcal Infection

Cryptococcus spp. are yeast-type opportunistic fungal pathogens with thick polysaccharide capsules that infect the lungs via airborne routes and frequently cause fatal meningoencephalitis. The cellular immune mechanism plays a central role in controlling cryptococcal infection and is critically regulated by Th1-Th2 immune balance. Pathogens that have invaded the host are recognized by innate immune cells,and appropriate immune responses are initiated. Pathogen-associated molecular patterns (PAMPs) are recognized by macrophages and dendritic cells via pattern recognition receptors (PRRs),which trigger the inflammatory responses as the first line of host defense. Some PRRs,such as Toll-like receptors (TLRs),NOD-like receptors (NLRs),and C-type lectin receptors (CLRs),are involved in the recognition of cryptococcal components,such as glucuronoxylomannan (GXM),mannoproteins (MPs),and nucleic acids. However,some cryptococcal cell components suppress the host immune response. This review will highlight the cryptococcal components involved in host immune responses. Future research is expected to promote the understanding of the mechanism of host immune response to Cryptococcus,which will lead to the development of new vaccines and therapies for cryptococcal infection.