Cytopathogenic toxin, CptA, of 1991 aas and an N-terminal signal TMS. Sneathia amnii is a poorly characterized emerging pathogen that has been implicated in amnionitis and urethritis. Gentile et al. 2020 found that S. amnii damages fetal membranes, and they identified and purified the cytotoxic exotoxin, CptA, that lyses human red blood cells and damages cells from fetal membranes. It binds to red blood cell membranes and forms pores with a diameter of 2.0-3.0 nanometers, resulting in osmolysis.  There is an association between Sneathia vaginalis and preterm birth (O'Brien et al. 2023). The Gram-negative anaerobe produces a large exotoxin, the cytopathogenic toxin A (CptA), that forms pores in human epithelial cells and red blood cells. In silico analysis predicts that a large amino-terminal region of the protein is globular and separated from the carboxy-terminal tandem repeats by a disordered region. O'Brien et al. 2023 found that a recombinant protein consisting of the predicted structured amino-terminal portion of CptA and devoid of the repeat region was sufficient to permeabilize epithelial cells and red blood cells. The repeat region was capable of binding to epithelial cells but did not permeabilize them or lyse red blood cells. CptA is the only S. vaginalis virulence factor that has been examined mechanistically (O'Brien et al. 2023).