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Quantitative character of fibrinogen uptake by M+ and M- variants of Streptococcus pyogenes
J Havlícek1, J Pokorný, H Havlícková
1Institute of Hygiene and Epidemiology, Prague, Czechoslovakia.
Abstract:
Fibrinogen was labelled with 125Iodine by mild chemical oxidation and its binding to Streptococcus pyogenes was subjected to quantitative analysis, inhibition and desorption studies. Fibrinogen was bound both by virulent and avirulent (M protein-positive and M protein-negative) matched strains of several serotypes. In all pairs of strains fibrinogen uptake was much higher by the M-positive variants. The ratio of bound fibrinogen to total fibrinogen was highly dependent both on the concentration of fibrinogen and the concentration of cocci. Equilibrium binding studies showed that the binding was a multifactorial process. Probably not only receptor fibrinogen interactions but also interactions between bound and unbound fibrinogen molecules took place. The uptake of fibrinogen was highly depressed in avirulent strains and practically uninfluenced in virulent strains by the presence of albumin or immunoglobulin. The bond between fibrinogen and streptococci is therefore different in virulent and avirulent variants. The fibrinogen receptors on the cell surface are specific.
Insights
Streptococcus pyogenes M protein-positive strains bind significantly more fibrinogen than M protein-negative strains. This specific binding interaction differs between virulent and avirulent bacterial variants.
Area of Science:
- Microbiology
- Biochemistry
- Immunology
Background:
- Streptococcus pyogenes is a significant human pathogen.
- Bacterial surface proteins play crucial roles in host-pathogen interactions.
- Fibrinogen is a key plasma protein involved in coagulation and host defense.
Purpose of the Study:
- To quantitatively analyze the binding of radiolabeled fibrinogen to Streptococcus pyogenes.
- To investigate the specificity and characteristics of fibrinogen-streptococci interactions.
- To compare fibrinogen binding between virulent and avirulent strains, particularly those expressing M protein.
Main Methods:
- Fibrinogen was labeled with Iodine-125 using mild chemical oxidation.
- Quantitative analysis, inhibition, and desorption studies were performed to assess binding.
- Binding was studied in relation to fibrinogen and bacterial concentrations.
- The influence of albumin and immunoglobulin on fibrinogen uptake was evaluated.
Main Results:
- Fibrinogen bound to both virulent and avirulent Streptococcus pyogenes strains, irrespective of M protein expression.
- M protein-positive variants exhibited significantly higher fibrinogen uptake compared to M protein-negative variants.
- Fibrinogen binding was dependent on both fibrinogen and bacterial concentrations, suggesting a multifactorial process.
- Uptake was notably reduced in avirulent strains when albumin or immunoglobulin was present, unlike in virulent strains.
Conclusions:
- Streptococcus pyogenes possesses specific fibrinogen receptors on its cell surface.
- The interaction between fibrinogen and streptococci differs between virulent and avirulent strains.
- M protein expression is associated with enhanced fibrinogen binding in Streptococcus pyogenes.
- These findings highlight a potential mechanism in streptococcal virulence and host interaction.