New research has identified two genetic mutations that may put individuals at increased risk for fungal infections. The research focused on patients with severe fungal infections (primarily of the genus Candida), but the findings may also have implications for patients who have more common mild infections. The research is published in two studies that appear together in the October 29, 2009 issue of The New England Journal of Medicine. The two independent research teams, one led by Prof. Mihai Netea (Radboud University Nijmegen Medical Centre, The Netherlands) and one led by Prof. Bodo Grimbacher (University College London, Royal Free Campus Hampstead, United Kingdom) discovered that mutations in two proteins involved in the pathway responsible for recognition of fungal beta-glucans substantially impaired the immune system’s ability to control fungi. Dr. Netea’s team discovered the relationship with mutations in the protein Dectin-1, and Dr. Grimbacher’s team identified the relationship with mutations in the CARD9 protein. The new results show that the mechanisms to protect against fungal infections have been largely conserved by evolution between mice and humans, which is not necessarily the case for other microbes. After sensing the presence of Candida by specialised recognition proteins such as Dectin-1, immune cells send signals from their surface to the inside, where CARD9 acts as an adaptor molecule that integrates those signals. CARD9 then initiates several molecular response mechanisms of the innate and adaptive immune system to protect us from those microorganisms. If Dectin-1 or CARD9 are mutated or missing, our immune system struggles to control Candida and may allow local or even systemic infections to develop.
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