The conventional treatment for the most prevalent mycosis in Latin America,
paracoccidioidomycosis (PCM), involves long periods of
therapy that results in side effects and a high frequency of relapses. The search for a new, alternative treatment is necessary. Pb40 is an antigenic
protein from P. brasiliensis fraction F0. This fraction has already been shown to have significant protective activity when used as a PCM
vaccine in experimental models. The complete
cDNA sequence corresponding to Pb40 was cloned into a pET-21a plasmid, expressed in E. coli with a his-tag and purified by affinity chromatography. The predicted
protein sequence exhibited nearly 100% homology to a fragment of the hypothetical EF-hand domain containing
protein of P. brasiliensis. Immunization with this
recombinant protein was used together with
chemotherapy in an attempt to improve PCM treatment. The combined
drug/rPb40 treatment exhibited long-lasting control of PCM in the liver and spleen and largely preserved the tissue structures of these organs. Despite the lack of a reduction in CFUs in the group that received the combined treatment, there was a significant reduction in the size of the lesions in the lungs after 70 days of
infection. At the same time, the
IL-10 levels were higher in the treated mice than in the infected-only mice. Moreover, significant levels of rPb40-specific
IgG antibodies were detected in the sera of immunized mice. Thus, the treatment protocol consisting of rPb40 immunization in addition to
fluconazole chemotherapy showed an additive protective effect after intratracheal challenge, preventing fungal dissemination to other sites of
infection and preventing relapses. These results provide new prospects for PCM
immunotherapy.