Amyloid Fibrils Produced by Streptococcus sanguinis Contribute to Biofilm Formation and Immune Evasion

Author(s)

Franco, Eduardo M. ; Alves, Livia A. ; Naveed, Hassan ; Freitas, Victor A. A. ; Bastos, Debora C. ; Mattos-Graner, Renata O.

• Document type: Journal article
• Source: INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES; v. 24, n. 21, p. 22-pg., 2023-11-01.

Abstract

Bacterial surface proteins assembled into amyloids contribute to biofilm formation and host immune evasion. Streptococcus sanguinis, a pioneer colonizer of teeth commonly involved in cardiovascular infections, expresses about thirty-three proteins anchored to the cell wall by sortase A. Here, we characterized the production of amyloid in S. sanguinis strains differing in biofilm and immune evasion phenotypes and investigated the role of sortase A in amyloidogenesis. Amyloid was identified in biofilms formed by nine strains, using Congo red (CR) staining and cross-polarized light microscopy. Additionally, EGCG, an amyloid inhibitor, impaired biofilm maturation in a strain-specific fashion. The amounts of amyloid-like components quantified in culture fluids of nine strains using thioflavin T and fluorimetry negatively correlated with bacterial binding to complement-activating proteins (SAP, C1q), C3b deposition and rates of opsonophagocytosis in PMNs, implying amyloid production in immune evasion. The deletion of the sortase A gene (srtA) in strain SK36 compromised amyloid production and sucrose-independent biofilm maturation. The srtA mutant further showed increased susceptibility to C3b deposition and altered interactions with PMNs as well as reduced persistence in human blood. These findings highlight the contribution of amyloids to biofilm formation and host immune evasion in S. sanguinis strains, further indicating the participation of sortase A substrates in amyloidogenesis. (AU)

• FAPESP's process: 17/19899-4 - Identification of factors modulating the susceptibility of Streptococcus sanguinis to complement immunity
• Grantee: Lívia Araújo Alves
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 18/02054-4 - Identification of factors modulating the susceptibility of Streptococcus sanguinis to complement immunity
• Grantee: Renata de Oliveira Mattos Graner
• Support Opportunities: Regular Research Grants
• FAPESP's process: 18/12248-0 - The role of exopolysaccharides and extracellular DNA in Streptococcus sanguinis evasion to complement system
• Grantee: Victor Aragão Abreu de Freitas
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 23/02087-8 - Isolation and characterization of Streptococcus spp. from patients with bacterial endocarditis
• Grantee: Lívia Araújo Alves
• Support Opportunities: Regular Research Grants
• FAPESP's process: 21/13074-9 - Identification of genes of Streptococcus sanguinis involved in its capacity to invade, persist and functionally affect human endothelial cells
• Grantee: Renata de Oliveira Mattos Graner
• Support Opportunities: Regular Research Grants