Participation of immunoglobulin-like (Ig-like) domain of the protein LIC_11903 of Leptospira interrogans in the host components interactions

• Grant number: 25/02545-1
• Support Opportunities: Scholarships in Brazil - Master
• Start date: November 01, 2025
• End date: May 31, 2027
• Field of knowledge: Biological Sciences - Microbiology - Applied Microbiology
• Principal Investigator: Ana Lucia Tabet Oller do Nascimento
• Grantee: Ana Bárbara Nunes
• Host Institution: Instituto Butantan. São Paulo , SP, Brazil
• Associated research grant: 19/17488-2 - Advancing the understanding of pathogenesis and virulence of Leptospira interrogans through proteomics, structural, mutagenesis and immunological analyses, AP.TEM

Abstract

Leptospirosis is a widespread zoonosis with high prevalence, especially in tropical regions. This disease is caused by the pathogenic bacterium Leptospira interrogans and can manifest with a wide range of symptoms, from mild fever to severe complications such as kidney failure and hemorrhages. Leptospira displays a variety of surface proteins that may contribute to the infection process. Typically, proteins containing specific domains are associated with particular functions. For example, proteins with the Ig-like domain from E. coli are found on the bacterial surface and are involved in bacterial adhesion and invasion processes. Thus, the main objective of this project is to evaluate the role of the Immunoglobulin-like (Ig-like) domain of the LIC_11903 protein in interactions with host components. To achieve this, recombinant plasmids containing the full-length LIC_11903 sequence, as well as a portion corresponding to the Ig-like domain and another unrelated to the domain, will be used for expression in different E. coli strains. After expression, protein solubility will be assessed to ensure that the protein is in its correct and functional form. Recombinant proteins will be purified using metal affinity chromatography, and their structures will be analyzed by circular dichroism (CD) spectroscopy. The immunogenicity of the protein and its fragments will be evaluated after mouse immunization through ELISA and Western blot assays. The reactivity of the protein and its fragments with sera from leptospirosis-positive patients will be assessed by ELISA. Finally, the interaction of the proteins with different extracellular matrix (ECM) components, human serum, and complement system molecules will be evaluated by ELISA. The adhesion activity of the protein and its fragments to cultured cells will also be analyzed. Understanding the involvement of Ig-like domains in interactions with host molecules will contribute to elucidating the pathogenic mechanisms of Leptospira, which may aid in identifying promising candidates for the development of effective leptospirosis vaccines. (AU)