Direct Inoculation and Human Transferrin Supplementation Increases the Survivability of Neisseria gonorrhoeae in the Upper Reproductive Tract of Estrogen‐Treated Female BALB/c Mice
Authors: Prudhomme Ian A. , Pilligua‐Lucas Michelle , Jerse Ann E. 
Published: June 2021

Objective

This study intended to investigate methods of increasing Neisseria gonorrhoeae (Gonococcus; Gc) survivability in the upper reproductive tract (URT) of female mice with the aim of establishing a previously undescribed murine model of Gc URT infections ‐ also known as pelvic inflammatory disease (PID) ‐ in women. Such a model would allow for further investigations into the natural history and pathogenesis of ascending Gc infections.

Methods

Two main experimental arms were used in this study: 1. Gc‐infected mice treated with estrogen alone vs estrogen and human transferrin (hTF) and 2. Gc‐infected mice treated with long‐acting progesterone (Medroxyprogesterone) alone vs progesterone and hTF. Appropriate uninfected, negative controls were used in all experiments. All mice were pre‐treated with antibiotics to suppress commensal flora and then given either estrogen or progesterone prior to inoculation, according to their study groups. Diestrous or anestrous stage BALB/c mice were then inoculated with Neisseria gonorrhoeae (strain FA1090) using a novel, trans‐cervical catheterization technique and the appropriate groups were treated with hTF up to 5 days post‐inoculation. Daily vaginal swabs were taken for polymorphonuclear white blood cell (PMN WBC) enumeration and quantitative Gc cultures up to day 5. In addition, part of each study group was sacrificed at days 3 and 5 post‐inoculation for Gc quantitative cultures of endometrial scrapings. Lastly, whole URTs from a portion of each group were fixed and stained for WBCs and Gc on days 3 and 5 post‐inoculation.

Results

Direct inoculation via trans‐cervical catheter proved successful in introducing and establishing Gc infection in the URT of all groups of estrogen‐treated mice for at least five days as determined by culture of endometrial scrapings and Gc‐specific IHC staining at day 5 post‐inoculation. Mice treated with progesterone showed no infection at any time point by either culture of daily vaginal swabs or of endometrial scrapings. Higher numbers of Gc were recovered from vaginal swabs (p<.05) and endometrial tissue on day 3 and 5 post‐inoculation from mice treated with estrogen and hTF compared to those treated with estrogen alone (comparisons made by geometric mean of Gc colonies recovered on each day).

Conclusions and Future Directions

This project established a novel method of direct, trans‐cervical inoculation of Gc into the female mouse URT thereby creating a usable model of Gc URT infection (PID) in women for further study. Future projects will utilize this model to better understand the natural history of Gc infections and to investigate potential methods for treating these infections. Currently, this laboratory is investigating host immune responses by measuring serum antibodies and vaginal chemokines/cytokines using this model. In addition, GFP‐labeled FA1090 strain Gc have been created and will be used for better visualization of Gc in histologic samples, which in turn could be used to track Gc movement through the mouse URT, as well as cellular responses to infection using sequentially fixed tissue samples.

Support or Funding Information

The Uniformed Services University of the Health Sciences and NIH/NIAID grant # R01 AI42053.