Neutrophil interactions with the sexually transmitted parasite Trichomonas vaginalis: implications for immunity and pathogenesis

Abstract

Trichomoniasis is the third most common sexually transmitted infection in humans and is caused by the protozoan parasite, Trichomonas vaginalis ( Tv ). Pathogenic outcomes are more common in women and generally include mild vaginitis or cervicitis. However, more serious effects associated with trichomoniasis include adverse reproductive outcomes. Like other infectious agents, pathogenesis from Tv infection is predicted to be the result of both parasite and host factors. At the site of infection, neutrophils are the most abundant immune cells present and probably play key roles in both parasite clearance and inflammatory pathology. Here, we discuss the evidence that neutrophils home to the site of Tv infection, kill the parasite, and that in some circumstances, parasites possibly evade neutrophil-directed killing. In vitro , the parasite is killed by neutrophils using a novel antimicrobial mechanism called trogocytosis, which probably involves both innate and adaptive immunity. While mechanisms of evasion are mostly conjecture at present, the persistence of Tv infections in patients argues strongly for their existence. Additionally, many strains of Tv harbour microbial symbionts Mycoplasma hominis or Trichomonasvirus , which are both predicted to impact neutrophil responses against the parasite. Novel research tools, especially animal models, will help to reveal the true outcomes of many factors involved in neutrophil- Tv interactions during trichomoniasis.

The Role of Small Extracellular Vesicles in Viral-Protozoan Symbiosis: Lessons From Trichomonasvirus in an Isogenic Host Parasite Model

“…have been implicated in immunomodulation, most of them showing upregulation of cytokines, while some, e.g., EV from Leishmania spp., causing downregulation of IL-8 and TNF-a in monocytes, but these phenomena were not investigated in the context of symbiont viruses (Szempruch et al, 2016). Our finding of suppressed IL-8 by sEVs from the TVV+TV infection may have clinical significance for the extracellular parasite adaptation since IL-8 is involved in the recruitment of neutrophils (Shaio et al, 1995)the immune cells primarily responsible for clearance of TV parasites (Mercer et al, 2018;Bhakta et al, 2020).…”

Clinical Effect of Metronidazole Vaginal Effervescent Tablet Combined with Flavescentis Sophora Suppository in the Treatment of Trichomonas Vaginitis

“…Severe cases can lead to precancerous lesions and also greatly interfere with the normal life and the life and health of patients [ 7 , 8 ]. Trichomonas vaginalis , a flagellate, will interfere with normal vaginal glycogen and destroy the immune defense system of the vagina itself, resulting in low vaginal immune function, and the vagina will be subsequently infected by a variety of bacteria; it can easily cause recurrence without radical treatment [ 9 ]. In pregnant women, at the same time, Trichomonas vaginalis may hinder the vagina's lactic acid secretion which affects the survival rate of the sperm in the vagina, causing infertility symptoms; therefore, seeking a safe, highly effective, and radical treatment for improving the prognosis of patients with trichomonas vaginitis and improving the quality of life is of great significance [ 10 ].…”

High Presence of NETotic Cells and Neutrophil Extracellular Traps in Vaginal Discharges of Women with Vaginitis: An Exploratory Study

“…Polymorphonuclear neutrophil (PMN) recruitment and tissue infiltration to sites of infection represent the first line of defense within the host innate immune system against invasive agents [ 9 ]. In vitro studies have reported variable concentrations of PMN during vaginal infections with CA [ 10 ], BV [ 11 ], and TV [ 12 ].…”