Antigenic Similarity Between Different Paracoccidioides Species in a Murine Model of Paracoccidioidomycosis Reveals High IgG Avidity for the 70 kDa Antigen

Since the new taxonomic proposal for differentiating Paracoccidioides species, many questions have emerged regarding its relevance beyond molecular analysis. Geographical distribution, pathogenesis, morphology, and virulence are still under debate to confirm the diverse genotypic profile of these species. In this study, we evaluated the serological differences of mice experimentally infected with Paracoccidioides brasiliensis sensu stricto, Paracoccidioides restrepiensis, Paracoccidioides americana, Paracoccidioides venezuelensis, and Paracoccidioides lutzii. The serological differences between the Paracoccidioides spp. were evaluated by ELISA, Western blot, and avidity Western blot using cell-free antigens (CFA) of the heterologous and homologous Paracoccidioides isolates used for the experimental infection. As expected, all Paracoccidioides spp. isolates shared several antigens that were recognized by mouse antibodies in both ELISA and Western blot. While ELISA results revealed differences in antigen recognition among isolates, these differences were not consistent at the species level. The number of bands identified in the immunoblotting varied among the isolates, with certain antigens, such as those from Pb01, a P. lutzii isolate, being less recognized across groups. We also observed overall differences in IgG avidity toward the CFA antigens. Notably, higher avidity was observed for the ~ 70 kDa antigen when compared to other antigens such as 79, 64, 54 and 43 kDa, the latter being gp43, the most studied and widely used glycoprotein for paracoccidioidomycosis immunodiagnosis.