Trichomonas vaginalis virulence factors: an integrative overview

Abstract

The elusive nature of Trichomonas vaginalis, the most common, non-viral, sexually transmitted pathogen has hampered our knowledge of its significance for human health for over 150 years. The combination of epidemiology, molecular cell biology, immunology and more recently genomics and other allied omics data, are all contributing at shedding new light onto what is increasingly recognised as a significant human pathogen leading to important health sequelae due to multifaceted interactions with its human host, the human microbiota, bacterial pathogens and viruses. The integrations of these various data are contributing in important ways to refining our understanding of the parasite pathobiology and virulent factors. Indeed, it is increasingly recognised that to rationalise the development of effective prophylactic and therapeutic treatments for human pathogens it is important to integrate the broadest possible spectrum of human-microbial-parasite-virus interactions in relation to qualitative and quantitative variations in the human innate and adaptive defence responses. This short review aims at providing an integrative overview of T vaginalis virulent factors by taking into account the importance of the human-microbiota-parasite-virus interplay in human health. It also highlights selected cellular characteristics of the parasite often overlooked in the biological and medical literature.

Keywords: ADHERENCE; HIV; PARASITOLOGY; TRICHOMONAS; VAGINAL MICROBIOLOGY.

Figure 1

Various cellular forms of Trichomonas vaginalis (TV). The TV trophozoite is characterised with four anterior and a fifth recurrent flagella. Upon contact with human tissue, TV can rapidly differentiate into an amoeboid form. In vitro trophozoites can differentiate into pseudocysts upon exposure to cold. Pseudocysts are spherical cells without visible flagella (they are internalised), they can divide and redifferentiate into trophozoites. It is not known if amoeboid form can differentiate into pseudocysts (?). Trophozoites are also known to form large cellular aggregates, in a process called swarming. Such groups of cells are thought to have stronger binding and cytotoxicity properties towards human tissues, and could also represent a form of defensive reaction to the host immune responses..

Figure 2

Interactions between Trichomonas vaginalis (TV), viruses, microbiota and the human host and their impact on human health. The diagram illustrates a TV-infected pregnant woman and her partner in the global context of human–microbe interactions. TV infections can affect the health status of both the adults and the embryo (eg, preterm birth and HIV transmission in utero). Rather then single/linear human–pathogen interactions, it is the complex network of interactions between viruses-bacteria-eukaryotes and the human host that should be considered when investigating disease conditions.