Objectives: In the present work a model based on human monocytes-derived macrophages (hMac) was used to study the host primary response to the yeast parasitic phase of the two major Sporothrix species with epidemiologic importance in Brazil. These species, S. schenckii and S. brasiliensis, are currently associated to human and feline sporotrichosis and, to the zoonotic transmission to humans and other animals in endemic areas of Rio de Janeiro State.

Methodology: Human peripheral blood monocytes cells were obtained from healthy volunteers after written consent. Once differentiated, human monocyte-derived macrophages (hMac) were infected with both S. schenckii and S. brasiliensis yeast cells, cultivated for 4 or 10 days. Aiming to evaluate the pathogen phagocytosis rate by hMac, microscopy and FACS assays were performed. ELISA tests were used for hMac cytokine secretion analysis and LDH assays were performed to evaluate pathogen mediated cytotoxicity. Nevertheless, antibodies against specific PRRs were used for functional analysis. 

Results: We hereby show that hMac exhibited a distinct ability to uptake S. schenckii and S. brasiliensis. The cell wall structure and composition is distinct for these two species. The hMac cytokine profile was also dissimilar as both species could induce TNF-α secretion but only S. brasiliensis had the capacity to induce a significant secretion of an anti-inflammatory cytokine, IL-10. Furthermore, in a previous work, we showed that aging and/or nutritional stress modify the cell wall architecture. Accordingly, the recognition of each species by hMAc is also impaired by the yeast cell growth condition. Besides, an important modulation of the Sporothrix uptake was observed when the interaction assay was performed in the presence of heat inactivated human serum. Nevertheless, hMac cytotoxicity mediated by S. brasiliensis was dependent on the pathogen phagocytosis. Finally, data with antibodies against specific receptors suggest that a new receptor is involved in S. brasiliensis uptake. This receptor is currently being characterized.

Conclusion: Our results clearly show that a thermo-labile serum factor is important to hMac recognition, uptake, cytotoxicity and cytokine response to Sporothrix spp. These results infer the participation of a new receptor, not yet described as involved in Sporothrix uptake. To our knowledge, this is the first report to describe the interaction of primary cell culture human macrophages with the parasitic phase of S. schenckii and S. brasiliensis.

Acknowledgements 
This work was supported by Fundação Carlos Chagas de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) and CNPq.

A new receptor is involved in the uptake of Sporothrix spp. by human macrophages