Background
Sporotrichosis is an increasing threat for humans, affecting mainly skin and subcutaneous tissues but that can cause disseminated infection in immunocompromised patients.
Sporothrix schenckii, Sporothrix brasiliensis
, and
Sporothrix globosa
are the main etiological agents of this mycosis, and each species show different virulence levels. The gold standard to assess fungal virulence is the mouse model that is expensive and time-consuming. Thus, invertebrate models have been reported as an alternative for the evaluation of fungal virulence. Here, we assessed whether
Tenebrio molitor
larvae could be a new alternative to study
Sporothrix
spp. virulence.
Methods
T. molitor
larvae were inoculated with different doses of
S. schenckii, S. brasiliensis
, and
S. globosa
, and animal mortality, cytotoxicity, and immunological parameters were analyzed, including the ability to stimulate immunological priming.
Results
Mortality curves demonstrated that yeast-like cells were the best fungal morphology to kill larvae and showed a similar ranking in virulence than that reported in other animal models, ie, being
S. brasiliensis
and
S. globosa
the species with the highest and lowest virulence, respectively. The usefulness of this model was validated with the analysis of several
S. schenckii
strains with different virulence degrees, and changes in cytotoxicity, humoral and cellular immunological parameters. Low-virulence strains stimulated low levels of cytotoxicity, phenoloxidase activity, and hemocyte countings, and these immunological cells poorly uptake fungi. Moreover, using recombinant Gp70 from
S. schenckii
immunological priming was stimulated in larvae and this protected against a lethal dose of fungal cells from any of the three species under study.
Conclusion
The study demonstrated that
T. molitor
larvae are an appropriate alternative invertebrate model to analyze the virulence of
S. schenckii, S. brasiliensis
, and
S. globosa
. Additionally, hemocyte levels, phenoloxidase activity, cytotoxicity, uptake by hemocytes, and immunological priming are biological parameters that can be used to study the
Sporothrix–T. molitor
interaction.