Immune defence to invasive fungal infections: A comprehensive review

The fungal infections are relatively common in humans that can range from common, mild superficial infections to life-threatening invasive infections. Most of the pathogenic fungi are opportunistic that cause disease under immunocompromised conditions such as HIV infection, cancer, chemotherapy, transplantation and immune suppressive drug users. Efficient detection and treatment of high-risk population remain the highest priority to avert most of the deaths. Majority of invasive infections are caused by Candida, Aspergillus and Cryptococcus species. Lack of effective vaccines, standardised diagnostic tools, efficient antifungal drugs and the emergence of drug-resistant species/strains pose a global threat to control Invasive fungal infections (IFI). A better understanding of the host immune response is one of the major approaches to developing new or improved antifungal strategies to control the IFIs. In this review, we have discussed pathogenesis of medically important fungi, fungal interaction with the host through pattern recognition receptors (PRRs) and the interplay of innate and adaptive immune cells in shaping host immunity to IFI. Further, we emphasized the role of memory cells by offering long-term protection in secondary or subsequent infections. Moreover, we depicted the role of unconventional innate-like immune cells in anti-fungal immunity. We also summarize the available information on the current vaccine strategies, genetic susceptibility to fungal infections, recent co-infections studies and the emergence of drug-resistance, a growing trend throughout the world. Finally, we emphasized the steps to be taken for the control of IFIs.