Targeting Deficiencies in the TLR5 Mediated Vaginal Response to Treat Female Recurrent Urinary Tract Infection

Abstract

The identification of the host defence peptides as target effectors in the innate defence of the uro-genital tract creates new translational possibilities for immunomodulatory therapies, specifically vaginal therapies to treat women suffering from rUTI, particularly those carrying the TLR5_C1174T SNP. Urinary tract infections (UTIs) are a microbial disease reported worldwide. Women are particularly susceptible with many suffering debilitating recurrent (r) infections. Treatment is by antibiotics, but such therapy is linked to antibiotic resistance and re-infection. This study explored the innate protective mechanisms of the urogenital tract with the aim of boosting such defences therapeutically. Modelling UTIs in vitro, human vaginal and bladder epithelial cells were challenged with uropathogenic Escherichia coli (CFT073) and microbial PAMPs including flagellin, LPS and peptidoglycan. Flagellin functioning via the TLR5/NFκB pathway was identified as the key UPEC virulence factor causing a significant increase (P < 0.05) in the production of the host-defence peptide (HDP), BD2. BD2-depleted urine samples from bladder infected mice supported increased UPEC growth, strengthening the significance of the HDPs in protecting the urogenital tissues from infection. Clinically, vaginal-douche BD2 concentrations were reduced (p < 0.05) in women suffering rUTIs, compared to age-matched healthy controls with concentrations further decreased (p < 0.05) in a TLR5392Stop SNP rUTI subgroup. Topical vaginal estrogen treatment increased (p < 0.001) BD2 concentrations in all women, including those carrying the SNP. These data identify therapeutic and antibiotic sparing roles for vaginal immunomodulatory agents that specifically target HDP induction, facilitate bacterial killing and disrupt the UPEC infection cycle.

High molecular weight hyaluronic acid: a two‐pronged protectant against infection of the urogenital tract?

“…The transcription factor NFκB is a key signalling molecule functioning in the innate response of the urogenital cells to flagellin11 and the response to HA 33. The signalling responses of VK2 E6/E7 and RT4 cells are comparable in their NFκB response to flagellin11; therefore, to further explore the signalling mechanisms underpinning the HA/flagellin effects, urothelial cells stably engineered to contain an NFκB reporter were used.…”

“…The signalling responses of VK2 E6/E7 and RT4 cells are comparable in their NFκB response to flagellin11; therefore, to further explore the signalling mechanisms underpinning the HA/flagellin effects, urothelial cells stably engineered to contain an NFκB reporter were used. These cells were incubated with flagellin (F), HMWT HA, HA/flagellin (HAF), heat‐killed UPEC (TPA4935) (B) and HA/B, and NFκB signalling measured from one to 24 h following challenge (Figure 5).…”

“…Such observations may have reflected the responses of the cells to reduced TLR5 numbers including the recycling of endocytosed TLR5 receptors to the cell membrane, the unregulated release of BD2 from intracellular cell granules or other negative feedback mechanisms functioning to increase the synthesis and storage of BD2. As BD2 is a key effector in defending the urogenital tract11 and the enhanced responses appeared independent of NFκB signalling, further investigation of this response is required.…”

“…Additionally, Toll‐like receptors (TLRs) located in the lower urogenital tissues respond to microbe‐associated molecular patterns, specifically flagellin, and trigger the release of host defence peptides as well as inflammatory molecules that function to clear potential UTIs 7, 8. The importance of the TLRs in defence of the urinary tract (UT) is emphasised by studies where individuals carrying the TLR5_C1174T (R392STOP) and TLR2_G2285A (R753Q) SNP genotypes link to an increased risk of infection 9, 10, 11…”

“…Again, however, clinical treatments involve an invasive catheterisation procedure. More acceptable therapeutically is a vaginal topical agent applied by the rUTI patient that functions as a barrier and prevents uropathogens from colonising the vagina, and ascending via the urethra to the bladder 11. To explore the potential of HA as a topical treatment for rUTI, this study used RT4 bladder and VK2E6/E7 vaginal cells to model the urogenital tract in vitro .…”