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Updated: Sep 20, 2026
Invasion of Human Cells by a Bacterial Pathogen
Published on: March 21, 2011
[Interaction of group A streptococci with a culture of HEp-2 cells]
Abstract:
An initial stage of the interaction of the virulent (matt) and avirulent (glossy) strains of group A streptococcus with the human epithelial tissue (Hep-2) was studied. M+ and M- variants of three strains of group A streptococcus belonging to serological types 2 and 4 possessed different biological activity against the Hep-2 epithelial cells in the monolayer. M+-variant actively affected the great majority of the cells of the monolayer, multiplied of their surface and formed microcolonies. M--variant affected only an insignificant number of cells and failed to multiply on them. In difference from M+-streptococci, the activity of M+-variants is explained by their capacity to adhere to the surface of the animal cells irreversibly. This process started immediately and terminated by 1 1/2 hours of the microbial incubation in vitro with the Hep-2 monolayer. Trypsin treatment of M+-streptococci sharply diminished their capacity to adhesion, this apparently being the result of M-protein digestion. The data presented point to the important role played by M-protein in the phenomenon of the streptococci adhesion to the epithelial cells.
Insights
Group A Streptococcus M+ variants exhibit strong adhesion to human epithelial cells, forming microcolonies. M- variants show limited interaction, highlighting M-protein
Area of Science:
- Microbiology
- Cell Biology
- Immunology
Background:
- Group A Streptococcus (GAS) is a significant human pathogen.
- The interaction between GAS and host epithelial cells is crucial for infection.
- M-protein is a key virulence factor in GAS.
Purpose of the Study:
- To investigate the initial interaction stages between GAS and human epithelial cells (Hep-2).
- To compare the biological activity of M+ (virulent) and M- (avirulent) GAS variants on Hep-2 cells.
- To elucidate the role of M-protein in GAS adhesion to epithelial cells.
Main Methods:
- In vitro incubation of M+ and M- variants of GAS (serotypes 2 and 4) with Hep-2 cell monolayers.
- Microscopic observation of bacterial interaction, multiplication, and microcolony formation.
- Assessment of bacterial adhesion capacity using trypsin treatment of M+ GAS.
Main Results:
- M+ GAS variants actively adhered to, multiplied on, and formed microcolonies on Hep-2 cells.
- M- GAS variants showed significantly less interaction and failed to multiply.
- Adhesion of M+ GAS was irreversible, occurring within 1.5 hours.
- Trypsin treatment of M+ GAS reduced adhesion, indicating M-protein's role.
Conclusions:
- M-protein is critical for the irreversible adhesion of Group A Streptococcus to human epithelial cells.
- M+ GAS variants demonstrate superior adherence and colonization capabilities compared to M- variants.
- The findings underscore M-protein's importance in the initial stages of streptococcal epithelial cell interaction.
