Leukocyte Lysis and Cytokine Induction by the Human Sexually Transmitted Parasite Trichomonas vaginalis

Abstract

Trichomonas vaginalis (Tv) is an extracellular protozoan parasite that causes the most common non-viral sexually transmitted infection: trichomoniasis. While acute symptoms in women may include vaginitis, infections are often asymptomatic, but can persist and are associated with medical complications including increased HIV susceptibility, infertility, pre-term labor, and higher incidence of cervical cancer. Heightened inflammation resulting from Tv infection could account for these complications. Effective cellular immune responses to Tv have not been characterized, and re-infection is common, suggesting a dysfunctional adaptive immune response. Using primary human leukocyte components, we have established an in vitro co-culture system to assess the interaction between Tv and the cells of the human immune system. We determined that in vitro, Tv is able to lyse T-cells and B-cells, showing a preference for B-cells. We also found that Tv lysis of lymphocytes was mediated by contact-dependent and soluble factors. Tv lysis of monocytes is far less efficient, and almost entirely contact-dependent. Interestingly, a common symbiont of Tv, Mycoplasma hominis, did not affect cytolytic activity of the parasite, but had a major impact on cytokine responses. M. hominis enabled more diverse inflammatory cytokine secretion in response to Tv and, of the cytokines tested, Tv strains cleared of M. hominis induced only IL-8 secretion from monocytes. The quality of the adaptive immune response to Tv is therefore likely influenced by Tv symbionts, commensals, and concomitant infections, and may be further complicated by direct parasite lysis of effector immune cells.

Humoral and T cell–mediated immune response against trichomoniasis

“…T. vaginalis such as B cells and approximately 50% of T. vaginalis‐ related leukotoxic activity against B cells was mediated by soluble factors, suggesting that the parasite may kill B cells without direct contact. T. vaginalis‐ related killing of B cells can also be mediated through a cell contact‐dependent manner . These findings indicate that B cells are the more vulnerable of leucocytes to killing by T. vaginalis .…”

“…T. vaginalis-related killing of B cells can also be mediated through a cell contact-dependent manner. 57 These findings indicate that B cells are the more vulnerable of leucocytes to killing by T. vaginalis. Phagocytosis of human PBMC by T. vaginalis has also been observed.…”

“…These findings indicate that B cells are the more vulnerable of leucocytes to killing by T. vaginalis . Phagocytosis of human PBMC by T. vaginalis has also been observed . The blocking of immune evasion mechanisms used by the parasite may lead to rapid parasite elimination.…”

“…Phagocytosis of human PBMC by T. vaginalis has also been observed. 57,58 The blocking of immune evasion mechanisms used by the parasite may lead to rapid parasite elimination.…”

Levels of IL-1β and IL-8 in Iraqi women with Bacterial vaginosis and Trichomoniasis

“…IL-8 is low or absent under normal conditions but highly inducible by a wide range of extra cellular stimuli, such as the proinflammatory cytokine IL-1 [8]. The present research aim to isolate and identify the microbiological causes of the main infections of genital tract and investigate the levels of proinflammatory cytokines IL-8 and IL-1β in vaginal fluid of women with genital tract infections compared with healthy control.…”