Abstract
BACKGROUND: Paracoccidioidomycosis is a systemic mycosis caused by the dimorphic fungus Paracoccidioides brasiliensis and related species, which are endemic to Latin America. Oral manifestations are highly relevant for diagnosis, representing the primary anatomical site biopsied for confirmation. OBJECTIVE: To investigate whether the virulence of P. brasiliensis influences the levels of circulating antigen in susceptible (B10.A) and resistant (A/Sn) murine models at multiple post-infection time points. The presence of oral lesions and their correlation with antigenemia were also assessed. METHODOLOGY: One-week-old female B10.A and A/Sn mice were inoculated with the P. brasiliensis lineages Pb18 or Pb265, whereas controls received sterile saline. At four, eight, 12, and 16 post-inoculation weeks, sera were collected via sub-axillary plexus incision under anesthesia. Circulating antigen levels were quantified using competitive ELISA. Specific antibody titers were determined by indirect non-competitive ELISA and P. brasiliensis antigens. Intergroup comparisons were performed using two-way ANOVA, followed by multiple comparisons. Oral cavities were visually examined by three independent evaluators to find mulberry stomatitis. Prevalence was expressed as the percentage of affected animals. RESULTS: Significant differences in the circulating antigen levels were detected between susceptible mice infected with Pb18 and Pb265 and between susceptible and resistant mice infected with Pb18 16 weeks after inoculation. The highest levels of antibodies were found when both B10.A and A/Sn mice were infected with Pb18. During infection, no mice showed mulberry-like lesions in the oral cavity. CONCLUSION: The virulence of the infecting P. brasiliensis strain, although not specifically linked to the gp43 antigen, plays a critical role in antigenemia. Despite absent oral lesions-an inherent limitation of this murine model-this study provides relevant insights into the relationship between fungal virulence and circulating antigen levels.