Poly(lactic acid-glycolic acid) nanoparticles markedly improve immunological protection provided by peptide P10 against murine paracoccidioidomycosis

Background and purpose: The present study reports on the preparation and testing of a sustained delivery system for the immunomodulatory peptide P10 aimed at reducing the in vivo degradation of the peptide and the amount required to elicit a protective immune response against paracoccidioidomycosis. Experimental approach: BALB/c mice were infected with the yeast Paracoccidioides brasiliensis to mimic the chronic form of paracoccidioidomycosis. The animals were treated daily with sulfamethoxazole/trimethoprim alone or combined with peptide P10, either emulsified in Freund's adjuvant or entrapped in poly(lactic acid-glycolic acid) (PLGA) nanoparticles at different concentrations (1 μg, 5 μg, 10 μg, 20 μg or 40 μg·50 μL ^-1). Therapeutic efficacy was assessed as fungal burden in tissues and the immune response by quantitative determination of cytokines. Key results: Animals given combined chemotherapy and P10 nanotherapy presented a marked reduction of fungal load in the lungs, compared with the non-treated animals. After 30 days of treatment, P10 entrapped within PLGA (1 μg·50 μL ^-1) was more effective than 'free' P10 emulsified in Freund's adjuvant (20 μg·50 μL ^-1), as an adjuvant to chemotherapy. After treatment for 90 days, the higher doses of P10 entrapped within PLGA (5 or 10 μg·50 μL ^-1) were most effective. Treatment with P10 emulsified in Freund's adjuvant (20 μg·50 μL ^-1) or P10 entrapped within PLGA (1 μg·50 μL ^-1) were accompanied by high levels of interferon-gamma in lung. Conclusions and implications: Combination of sulfamethoxazole/trimethoprim with the P10 peptide entrapped within PLGA demonstrated increased therapeutic efficacy against paracoccidioidomycosis. P10 incorporation into PLGA nanoparticles dramatically reduced the peptide amount necessary to elicit a protective effect.