A Novel In Vitro Host−Pathogen Model for <i>Felis catus</i> and <i>Sporothrix</i> Zoonotic Species Investigation

Hyperendemic zoonotic sporotrichosis, attributed to Sporothrix brasiliensis, presents a significant public health challenge in Brazil. Cats exhibit severe symptoms and high fungal loads, though their susceptibility is unclear. Sporothrix schenckii can also cause feline disease, primarily seen in Asia. This study is the first to report an in vitro model for examining cat immune cell responses to S. brasiliensis or S. schenckii. We investigated the phagocytic activity of blood cells (FMdP) from healthy domestic cats, challenged with yeast cells of S. brasiliensis and S. schenckii. The survival of these yeasts within cat phagocytes and their cytotoxic effect on host cells were monitored. Both fungal species developed and replicated within feline phagocytes while S. brasiliensis phagocytic index (PI) was higher (p < 0.0001). Interspecies analyses showed that S. schenckii required a higher multiplicity of infection to be more cytotoxic than S. brasiliensis (p ≤ 0.01). The present report brings relevant information to understand S. brasiliensis host adaptation and, ultimately, cat susceptibility to sporotrichosis. This pioneering study on the feline's innate immune response provides new insights for future complex studies such as those involving fungal ligand recognition by cat cell receptors.