A study by Hooven et al1 found that retrocyclin (RC-101) possibly works against bacterial vaginosis biofilms and toxin activity in vitro (in a lab), but does not have a significant impact on planktonic bacteria. 

What is retrocyclin?

Retrocyclin is a type of peptide molecule, also known as defensins. Retrocyclin broadly defends against bacteria and viruses, but the human retrocyclin gene does not work very well for complicated reasons we won’t go into. Retrocyclin doesn’t have any significan’t effects on lactobacilli, the normal flora in the vaginal tract, and is non-toxic to human cells.

An STI vaccine?

Several studies have shown that retrocyclin prevents HIV and herpes (HSV) infections, and a retrocyclin product is in development for sexually transmitted infection (STI) prevention, like a vaccine.

The study

The study aimed to see if retrocyclin could be useful in treating and preventing bacterial vaginosis (BV). Gardnerella vaginalis was used and its biofilm was grown on agar, and the planktonic bacteria was grown on a meat broth.

The results

  • RC-101 halted the G. vaginalis toxin-related death of cells (cytolysis).
  • RC-101 inhibited the formation of new G. vaginalis biofilms in a dose-dependent manner.
  • Pre-existing biofilms were not disrupted.
  • RC-101 did not significantly impact G. vaginalis growth in the meat broth, meaning it does not kill or maim planktonic, free-floating bacteria.
  • The researchers are not sure why these effects were seen.

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  1.  Retrocyclin inhibits Gardnerella vaginalis biofilm formation and toxin activityThomas A. HoovenTara M. RandisSaul R. HymesRyan Rampersaud and Adam J. Ratner

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