EVALUATION OF C5aR1 INHIBITORS (AVACOPAN AND PMX53) IN THE PATHOLOGICAL CHANGES CAUSED BY LEPTOSPIROSIS ASSOCIATED PULMONARY HEMORRAGIC SYNDROME

• Grant number: 25/01659-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: April 01, 2025
• End date: March 31, 2026
• Field of knowledge: Biological Sciences - Immunology - Immunochemistry
• Principal Investigator: Lourdes Isaac
• Grantee: Natália dos Santos Ramirez
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Leptospirosis is a bacterial disease caused by spirochetes of Leptospira genus. Can be transmitted in direct or indirect way to humans and rodents are the principal vector. The infection from these bacteria establishes a systemic infection. The vast majority of infected people are asymptomatic or have mild symptoms, and approximately 5 to 10% of those infected show more severe clinical symptoms, developing Weil's Syndrome. Among these cases, there are cases of Leptospirosis Pulmonary Hemorrhagic Syndrome (LPHS), when more severe symptoms are observed, including hemorrhage in the pulmonary epithelial tissue and commonly, the evolution to death. Leptospira infection occurs because pathogenic strains have mechanisms to evade the host's immune system, for example, through the Complement System (CS). The CS performs various immunological functions, including the formation of the MAC (Membrane Attack Complex), the generation of opsonins and anaphylotoxins. An anaphylotoxin generated by the activation of the Complement System is the C5a fragment, an inflammatory mediator with a potent ability to recruit mast cells, eosinophils and other immune system cells that liberate inflammatory mediators. This anaphylotoxin works by interacting with its receptors, the focus of this project being C5aR1. Male and female C3H/HeJ mice (deficient in the TLR-4 receptor, which makes them more susceptible to leptospires) will be infected with Leptospira interrogans Copenhageni Fiocruz L1-130 and treated with Avacopan (CCX168) and PMX53, selectives inhibitors of C5aR1. These animals will be monitored daily for survival and weight loss, considering parameters that indicate the progression of the infection to a more serious condition. Subsequently, samples from these animals will be collected and analyzed. Bronchial-alveolar lavage (BAL) will be collected for analysis of C5a concentration by ELISA. The bacterial load in the lung will be quantified by qPCR of the organ, in order to analyze whether Avacopan does not interfere with bacterial growth. Finally, this project aims to evaluate the survival and onset of leptospiral infection in mice, analyzing signs of the establishment of the disease and immunological parameters through a series of experiments.