Analysis of the interactions of Streptococcus sanguinis with endothelial cells and neutrophils from human peripheral blood

• Grant number: 25/08566-0
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: July 01, 2025
• End date: December 31, 2027
• Field of knowledge: Health Sciences - Dentistry
• Principal Investigator: Renata de Oliveira Mattos Graner
• Grantee: Eduardo Martinelli Franco
• Host Institution: Faculdade de Odontologia de Piracicaba (FOP). Universidade Estadual de Campinas (UNICAMP). Piracicaba , SP, Brazil
• Associated research grant: 24/14159-6 - Analysis of the interactions of Streptococcus sanguinis with endothelial cells and neutrophils from human peripheral blood., AP.R

Abstract

Streptococcus sanguinis is an abundant commensal species of the oral cavity with a high capacity to initiate dental biofilms. By mechanisms still poorly understood, S. sanguinis is also a common opportunistic pathogen of cardiovascular diseases, including infective endocarditis and atherosclerotic diseases. Previous studies of our research group indicate three genes consistently associated with phenotypes of complement evasion and invasion of endothelial cells, the nox, swan and ssa_0094 genes. Interestingly, the proteins encoded by these three genes contain binding domains to glycoproteins abundant in serum and/or in the extracellular matrix (ECM). The aim of this project is to investigate the mechanisms of serum-dependent interaction of S. sanguinis with endothelial cells and peripheral blood neutrophils (PMNs), mediated by nox, swan and ssa_0094. For this purpose, the wild-type strain SK36 and its knock-out mutants of nox (SKnox), swan (SKswan) and ssa_0094 (SK0094) will be analyzed. The binding profiles of these strains to seven glycoproteins abundant in serum and/or ECM (fibrinogen, plasminogen, fibronectin, elastin, collagen type I, vitronectin and laminin) will be determined and compared through fluorimetric assays. Invasiveness in primary human coronary artery endothelial cells (HCAEC) mediated by integrins or receptors to these glycoproteins will be then investigated using pretreatment of HCAEC with a panel of blocking antibodies specific to the respective integrins or receptors [¿5¿1, ¿v¿3, -¿5, ¿v, ¿1, ¿3, CD11c/CD18 (CR4) and CD35 (CR1)]. The same strains will be also compared for their ability to induce NETosis by PMN in the presence of serum glycoproteins in ex vivo assays with peripheral blood. The interaction of these strains with PMN isolated from blood will be further compared under different conditions [presence of human serum, heat-inactivated serum and serum-free (PBS)], through qualitative analyses by scanning electron microscopy (SEM) and quantitative analyses using light microscopy. Furthermore, the involvement of receptors for serum proteins of the complement system (CR1 and CR3) in the activation of NETosis in PMNs exposed to S. sanguinis will be evaluated using PMN pretreated with antibodies blocking these receptors. The results of this project may reveal mechanisms by which S. sanguinis interacts with human endothelial cells and PMNs to invade or manipulate the functions of these cells. (AU)