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Identification of a Cytopathogenic Toxin from Sneathia amnii
Gabriella L Gentile1, Amy Sanford Rupert1, Lizette I Carrasco1
1Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, Virginia, USA.
Abstract:
Sneathia amnii is a poorly characterized emerging pathogen that has been implicated in amnionitis and urethritis. We found that S. amnii damages fetal membranes, and we identified and purified a cytotoxic exotoxin that lyses human red blood cells and damages cells from fetal membranes. The gene appears to be cotranscribed with a second gene that encodes a protein with identity to two-partner system transporters, suggesting that it is the "A," or secreted component of a type Vb system. The toxin is 1,881 amino acids with a molecular weight of approximately 200 kDa. It binds to red blood cell membranes and forms pores with a diameter of 2.0 to 3.0 nm, resulting in osmolysis. Because it appears to be the "A" or passenger component of a two-partner system, we propose to name this novel cytotoxin/hemolysin CptA for cytopathogenic toxin component A.IMPORTANCESneathia amnii is a very poorly characterized emerging pathogen that can affect pregnancy outcome and cause urethritis and other infections. To date, nothing is known about its virulence factors or pathogenesis. We have identified and isolated a cytotoxin, named CptA for cytopathogenic toxin, component A, that is produced by S. amnii CptA is capable of permeabilizing chorionic trophoblasts and lysing human red blood cells and, thus, may play a role in virulence. Except for small domains conserved among two-partner secretion system passenger proteins, the cytotoxin exhibits little amino acid sequence homology to known toxins. In this study, we demonstrate the pore-forming activity of this novel toxin.
Insights
Researchers identified a novel toxin, CptA, from the emerging pathogen Sneathia amnii. This cytopathogenic toxin component A lyses red blood cells and damages fetal membranes, potentially explaining S. amnii's role in infections.
Area of Science:
- Microbiology
- Pathogenesis
- Molecular Biology
Background:
- Sneathia amnii is an emerging pathogen linked to amnionitis and urethritis.
- Its virulence factors and pathogenic mechanisms remain largely unknown.
Purpose of the Study:
- To identify and characterize virulence factors of Sneathia amnii.
- To investigate the role of a novel cytotoxic exotoxin in S. amnii pathogenesis.
Main Methods:
- Identification and purification of a cytotoxic exotoxin from S. amnii.
- Characterization of the toxin's effects on human red blood cells and fetal membrane cells.
- Analysis of the toxin's gene and protein structure, including its relation to two-partner secretion systems.
Main Results:
- A novel cytotoxic exotoxin, CptA (cytopathogenic toxin component A), was identified and purified.
- CptA lyses human red blood cells by forming pores (2.0-3.0 nm diameter), causing osmolysis.
- CptA damages cells from fetal membranes and chorionic trophoblasts, suggesting a role in virulence.
Conclusions:
- CptA is a novel pore-forming cytotoxin produced by Sneathia amnii.
- This toxin likely contributes to S. amnii pathogenesis, particularly in pregnancy-related infections.
- CptA represents a potential therapeutic target for S. amnii infections.
