Abstract Cryptococcus neoformans is one of the leading causes of invasive fungal infection in humans worldwide. C. neoformans uses macrophages as a proliferative niche to increase infective burden and avoid immune surveillance. However, the specific mechanisms by which C. neoformans manipulates host immunity to promote its growth during infection remain ill-defined. Here we demonstrate that eicosanoid lipid mediators manipulated and/or produced by C. neoformans play a key role in regulating pathogenesis. C. neoformans is known to secrete several eicosanoids that are highly similar to those found in vertebrate hosts. Using eicosanoid deficient cryptococcal mutants Δplb1 and Δlac1 , we demonstrate that prostaglandin E 2 is required by C. neoformans for proliferation within macrophages and in vivo during infection. Genetic and pharmacological disruption of host PGE 2 synthesis is not required for promotion of cryptococcal growth by eicosanoid production. We find that PGE 2 must be dehydrogenated into 15-keto-PGE 2 to promote fungal growth, a finding that implicated the host nuclear receptor PPAR- γ . C. neoformans infection of macrophages activates host PPAR- γ and its inhibition is sufficient to abrogate the effect of 15-keto-PGE 2 in promoting fungal growth during infection. Thus, we describe the first mechanism of reliance on pathogen-derived eicosanoids in fungal pathogenesis and the specific role of 15-keto-PGE 2 and host PPAR- γ in cryptococcosis. Author Summary Cryptococcus neoformans is an opportunistic fungal pathogen that is responsible for significant numbers of deaths in the immunocompromised population worldwide. Here we address whether eicosanoids produced by C. neoformans manipulate host innate immune cells during infection. Cryptococcus neoformans produces several eicosanoids that are notable for their similarity to vertebrate eicosanoids, it is therefore possible that fungal-derived eicosanoids may provoke physiological effects in the host. Using a combination of in vitro and in vivo infection models we identify a specific eicosanoid species - prostaglandin E 2 – that is required by C. neoformans for growth during infection. We subsequently show that prostaglandin E 2 must be converted to 15-keto-prostaglandin E 2 within the host before it has these effects. Furthermore, we find that prostaglandin E 2 /15-keto-prostaglandin E 2 mediated virulence is via activation of host PPAR- γ – an intracellular eicosanoid receptor known to interact with 15-keto-PGE 2 .

15-keto-prostaglandin E<sub>2</sub>activates host peroxisome proliferator-activated receptor gamma (PPAR-γ) to promote<i>Cryptococcus neoformans</i>growth during infection

15-keto-prostaglandin E2activates host peroxisome proliferator-activated receptor gamma (PPAR-γ) to promoteCryptococcus neoformansgrowth during infection