PARTICIPATION OF THE COMPLEMENT SYSTEM IN THE ETIOPATHOGENESIS OF EXPERIMENTAL PULMONARY HEMORRHAGIC SYNDROME ASSOCIATED WITH LEPTOSPIROSIS

• Grant number: 23/14227-9
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: April 01, 2024
• End date: November 30, 2026
• Field of knowledge: Biological Sciences - Immunology - Cellular Immunology
• Principal Investigator: Lourdes Isaac
• Grantee: Lara Rodrigues da Silva
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Leptospirosis is an emerging and neglected disease caused by pathogenic spirochete bacteria of the genus Leptospira. This infection can be acquired either directly or indirectly. The direct form consists of contact between damaged mucous membranes or skin and the urine of animals contaminated with this pathogen. Meanwhile, the indirect form occurs when the individual comes into contact with contaminated water, soil or vegetation. The acute clinical symptoms of leptospirosis are usually common to many other acute febrile illnesses, which makes it difficult to diagnose. In addition, this infection can develop into a late stage known as Weil's Syndrome, in 5 to 10% of reported cases. Some patients develop Leptospirosis-Associated Severe Pulmonary Hemorrhagic Syndrome (LPHS). These patients die on average 72 hours after the onset of symptoms, the etiopathogenesis of which is still unknown. Among the possible origins of this condition, we highlight the possible involvement of the Complement System, since its uncontrolled activation in the lung can lead to an exacerbated immune response, with a large release of cytokines and anaphylotoxins, which can affect the permeability of lung tissue, causing lesions and local hemorrhage. However, the role of this system in LPHS still needs to be better investigated.The aim of this study is to evaluate the possible involvement of the Complement System in LPHS in a murine model. To this end, we intend to determine the deposition of Complement System proteins, such as C3c, Factor B, MASP-2, C1q and the C5b-9 complex, as well as C5aR1, in the lungs of male and female C3H/HeJ mice infected with L. interrogans serovar Copenhageni Fiocruz L1-130 by immunohistochemistry. To measure the presence of Leptospira antigens by immunohistochemistry and quantify the bacterial load by qPCR in the lung, kidney and liver. Evaluate the presence of the inflammatory cytokines IL-6, TNF-±, IL-1² and IL-18 by ELISA in the bronchoalveolar lavage (BAL) of infected animals. To determine the presence of C5a, C3a and the SC5b-9 complex of the Complement System in the BAL and serum of mice infected with Fiocruz L1-130 by ELISA in an attempt to understand the systemic and local presence of these anaphylotoxins in relation to SC activation and the progression of LPHS. Finally, to evaluate the use of the C5aR inhibitor in mice infected with L. interrogans Fiocruz L1-130 as a potential therapeutic target in the prognosis of LPHS.