Inhibition of the PD-1 immune checkpoint receptor in adjunctive therapy to antifungals in murine pulmonary paracoccidioidomycosis

• Grant number: 23/17308-0
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Effective date (Start): May 01, 2024
• Effective date (End): April 30, 2025
• Field of knowledge: Biological Sciences - Immunology - Applied Immunology
• Principal Investigator: Flávio Vieira Loures
• Grantee: Nycolas Willian Preite
• Host Institution: Instituto de Ciência e Tecnologia (ICT). Universidade Federal de São Paulo (UNIFESP). Campus São José dos Campos. São José dos Campos , SP, Brazil

Abstract

In paracoccidioidomycosis (PCM), the most prevalent systemic mycosis in Latin America, previous studies have revealed that host immunity is strongly regulated by various suppressive mechanisms mediated by plasmacytoid dendritic cells, the enzyme 2,3 indoleamine dioxygenase (IDO-1), regulatory T cells (Treg), well as negative co-stimulatory molecules such as CTLA-4 and PD-1. Monoclonal antibody immunotherapy has emerged as an effective therapeutic approach in the treatment of some types of cancer and immune disorders. In addition to use in these areas, monoclonal antibodies have also shown potential in combating infectious diseases, enhancing the efficacy of existing antimicrobial drugs. In the context of fungal infections, monoclonal antibody immunotherapy has been explored as a promising strategy. Studies have shown that immune checkpoint inhibitors, such as those targeting the PD-1 or CTLA-4 receptor, can modify the course of these diseases, promoting a more effective immune response and reducing the severity of the infection. In a previous study, we were able to demonstrate that blocking CTLA-4 and PD-1 with specific antibodies reduced the fungal burden of affected organs, improved lung lesions, and increased the survival of treated animals by strengthening protective immune responses. Interestingly, treatment with anti-PD-1 resulted in better control of the immune response when compared to treatment with anti-CTLA-4, as there was less cellular influx to the lungs. This work aims to establish an immunotherapeutic process in PCM involving the inhibition of PD-1 molecules in association or not with three different antifungals in order to reverse the characteristic immunosuppression of this chronic infection and promote the cure of hosts. For this purpose, C57BL/6 mice will be inoculated with 1x106 P. brasiliensis yeasts, after 6 weeks the animals will be treated with anti-PD-1 in combination or not with amphotericin B, fluconazole or itraconazole. After two weeks of treatment, the animals will be evaluated for the course of the disease by UFC, histopathology, and morbidity curves. Additionally, ELISA and flow cytometry will be performed to verify the immune response resulting from the use of this new immunotherapeutic process. In an additional protocol, the animals will also be evaluated three weeks after the end of the treatments. In this way, we intend to develop a protocol that aims to interrupt the course of the disease by controlling fungal growth associated with the restoration of the immune response which, together, may result in significant improvement or even cure of this chronic infection.