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Evaluation of the susceptibility of oral streptococcus ssp. to the marking by the complement system

Grant number: 13/07098-6
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): August 01, 2013
Effective date (End): July 31, 2015
Field of knowledge:Health Sciences - Dentistry
Principal researcher:Renata de Oliveira Mattos Graner
Grantee:Thaís Rodrigues de Carli
Home Institution: Faculdade de Odontologia de Piracicaba (FOP). Universidade Estadual de Campinas (UNICAMP). Piracicaba , SP, Brazil


Bacteria of the human microbiota are in balance with their host; however, under specific conditions, they are able to overcome the host immune defenses and cause infection. The oral cavity represents one of the human body sites with the biggest and most diverse microbiota, and the oral tissues are intimately connected to the blood stream. The virulence potential of its several microorganisms is partly determined by its capability of resisting to defense components of the host. There is evidence that the predominant species of Streptococcus in the oral cavity can cause systemic diseases in both healthy and immunodeficient subjects, once reaching the bloodstream. Species of Streptococcus express cell wall proteins which are involved in evasion of innate immunity components, such as the complement system, which has an essential role in opsonization and inflammatory responses to microorganisms in blood and tissues.However, little is known about the mechanisms of bacterial evasion of immune system among oral streptococcal species. Recently, we showed that the oral species Streptococcus mutans is able to escape from phagocytosis by neutrophils in human blood, if two of its genetic transcription regulatory systems are inactivated, the Two-Component System VicRK and CovR. (Negrini et al., 2012). VicRK and CovR regulate the expression of several genes which encode proteins involved in cell wall biogenesis (Stipp et al., 2013) and our hypothesis is that some of these genes are involved in the evasion from opsonization by the complement system. Cell wall biogenesis proteins have been characterized by our research group in strains of oral species of Streptococcus isolated from blood and oral cavity, which include Streptococcus mitis, Streptococcus oralis, Streptococcus gordonii e Streptococcus sanguini, isolated by Dr. Mogens Kilian's research group from the University of Aarthus, Denmark (Proc. 2009/50547-0). Our working hypothesis is that strains with high ability to evade the complement system are more capable of infecting and surviving in the bloodstream and, therefore, cause infection. The aim of this project is to compare the efficiency of complement C3 opsonization in strains isolated from human blood and oral cavity in the major species of oral streptococci, Streptococcus mitis, Streptococcus oralis, Streptococcu gordonii and Streptococcus sanguinis.

Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
ALVES, LIVIA A.; DE CARLI, THAIS R.; HARTH-CHU, ERIKA N.; MARIANO, FLAVIA S.; HOFLING, JOSE F.; STIPP, RAFAEL N.; MATTOS-GRANER, RENATA O. Oral streptococci show diversity in resistance to complement immunity. Journal of Medical Microbiology, v. 68, n. 4, p. 600-608, APR 2019. Web of Science Citations: 2.

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