Slight Pro-Inflammatory Immunomodulation Properties of Dendritic Cells byGardnerella vaginalis: The “Invisible Man” of Bacterial Vaginosis?

Abstract

Bacterial vaginosis (BV), the most common genital infection in reproductive-aged women, is associated with increased risk of sexually transmitted infections. Its etiology remains unclear, especially the role of Gardnerella (G.) vaginalis, an anaerobic bacterium characteristic of the BV-alteration of the vaginal ecosystem. In the genital mucosa, dendritic cells (DCs) sense bacteria of the microenvironment via receptors and then orchestrate the immune response by induction of different T cell subtypes. We investigated the interactions between G. vaginalis and human monocyte-derived DCs using a wide range of bacterial concentrations (multiplicity of infection from 0.01 to 100), and the effects of this pathogen on PHA-induced lymphocyte proliferation. As observed by electron microscopy and cytometry, G. vaginalis reduced the internalization ability of DCs by forming extracellular clusters and induced neither DC maturation, nor DC secretion of cytokines, except at the highest dose with a very early DC maturation state. The same profile was observed on lymphocytes with significant increases of proliferation and cytokine secretion only at the highest bacterial concentration. Our findings indicate that G. vaginalis possesses slight immune-stimulating activities against DCs and T cells, reflecting thus a defective inflammatory response and giving rise to the atypical, non- or low-grade, inflammatory clinical disease profile.

Immunopathology of Recurrent Vulvovaginal Infections: New Aspects and Research Directions

“…On the other hand, DCs maturation has been shown to be induced by lavage samples from women with BV leading to DC-surface expression of CD83 and CD86 markers, reduced internalization ability, improved antigen presentation to T cells, thereby modulating T cell responses (91). The same profile of activation and maturation of DCs and T cells has been reported recently but found to occur only at the highest G. vaginalis concentration (92). No heightened neutrophils levels and maturation of DCs only at high bacterial concentration depicts the uncharacteristic and poor inflammatory response without any localized inflammatory symptoms, perhaps the reason why BV is not called bacterial vaginitis.…”

In vivo microbiome and associated immune markers: New insights into the pathogenesis of vaginal dysbiosis

“…This event, together with the poor T cell-stimulating activity of G . vaginalis 29 , which was predominant in the intermediate group, may explain the absence or weakness of clinical symptoms 11 . Moreover, B .…”

Encrustations on ureteral stents from patients without urinary tract infection reveal distinct urotypes and a low bacterial load

“…Many microbiome profiles were dominated by bacteria known to be prevalent in women with bacterial vaginosis, such as Mobiluncus [45], Prevotella [46] or G. vaginalis and A. vaginae [15, 18, 47] but are also found in asymptomatic patients [48]. Similarly, many samples contained significant relative amounts of Enterobacterales , which are commonly recognized as uropathogens, with E. coli being detected by standard cultivation methods in clinical diagnostic laboratories in the great majority of uncomplicated UTIs.…”