CRYPTOCOCCUS NEOFORMANS CAPSULAR POLYSACCHARIDE GXM AND GXMGal MODULATES ARGINASE AND iNOS EXPRESSION IN DH82 CANINE MACROPHAGES

Canine cryptococcosis is a systemic disease caused Cryptococcus. Infection originates in the respiratory tract, with the potential to disseminate to the central nervous system.The primary virulence factor is the polysaccharide capsule, composed of glucuronoxylomannan (GXM) and glucuronoxylomannogalactan (GXMGal). Macrophages play a fundamental role in antifungal defense. Inducible nitric oxide synthase (iNOS) is characteristic of macrophages with a pro-inflammatory profile-M1, whereas arginase is associated with a regulatory and tissue-repair profile-M2. Our group has previously reported that C. neoformans is capable of immunomodulating the antifungal response of canine macrophages-DH82, favoring its own survival. Little is known about the classical polarization of canine macrophages by GXM and GXMGal in the context of cryptococcosis. This study aims to elucidate the mechanisms by C. neoformans to immunomodulate the polarization of DH82 in vitro. DH82 (2 x 10⁵) were cultured in DMEM medium (5% FBS) at 37°C and 5% CO₂ and stimulated with LPS (500 ng/mL) and IFN-γ (20 ng/mL), IL-4 (20 ng/mL), GXM/GXMGal (100 µM), C. neoformans yeast (strain B3501/CAP67) (MOI 3:1). Arginase and iNOS expression were evaluated via flow cytometry and immunofluorescence. Nitrite concentration was determined using the Griess test. The results demonstrate that arginase levels increased in cells treated with GXM and B3501 yeast, whereas NO expression was reduced compared to the GXMGal-treated. DH82 cells treated with GXMGal showed increased iNOS expression. We conclude that arginase and iNOS production in DH82 can be immunomodulated by the polysaccharides GXM and GXMGal. This modulation may facilitate the establishment, survival, and dissemination of the fungus within the host. Thus, this study contributes to a better understanding of the interactions between Cryptococcus and canine macrophages, providing insights for the development of therapeutic and infection control.