Silencing of OCH1 unveils the role of Sporothrix schenckii N-linked glycans during the host–fungus interaction

Nancy E Lozoya-Pérez,1 Sergio Casas-Flores,2 José Roberto Fogaça de Almeida,3 José A Martínez-Álvarez,1 Luz A López-Ramírez,1 Grasielle Pereira Jannuzzi,3 Elías Trujillo-Esquivel,1 Eine Estrada-Mata,1 Sandro R Almeida,3 Bernardo Franco,1 Leila M Lopes-Bezerra,3,4 Héctor M Mora-Montes1 1Department of Biology, Division of Exact and Natural Sciences, Universidad de Guanajuato, Guanajuato, Mexico; 2Division of Molecular Biology, IPICYT, San Luis Potosí, Mexico; 3Laboratory of Clinical Mycology, Faculty of Pharmacy, Universidade de São Paulo, São Paulo, Brazil; 4Laboratory of Cellular Mycology and Proteomics, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil Background: Sporothrix schenckii is a neglected fungal pathogen for the human being and other mammals. In several fungal systems, Och1 is a Golgi α1,6-mannosyltransferase with a key function in the synthesis of N-linked glycans; which are important elements during the host-fungus interplay. The role of OCH1 in fungal virulence seems to be species-specific, being an essential component for Candida albicans virulence and dispensable during the interaction of Aspergillus fumigatus with the host. Methods: Here, we silenced S. schenckii OCH1 and characterized the phenotype of the mutant strains. Results: The mutant strains did not show defects in the cell or colony morphology, the growth rate or the ability to undergo dimorphism; but the cell wall changed in both composition and exposure of inner components at the surface. When interacting with human monocytes, the silenced strains had a reduced ability to stimulate TNFα and IL-6 but stimulated higher levels of IL-10. The interaction with human macrophages was also altered, with reduced numbers of silenced cells phagocytosed. These strains showed virulence attenuation in both Galleria mellonella and in the mouse model of sporotrichosis. Nonetheless, the cytokine levels in infected organs did not vary significantly when compared with the wild-type strain. Conclusion: Our data demonstrate that OCH1 silencing affects different aspects of the S. schenckii-host interaction. Keywords: cell wall, protein glycosylation, sporotrichosis, gene silencing, host–fungus interplay, mannosyltransferase