Trichomonas vaginalis: lifestyle, cellular biology, and molecular mechanisms of pathogenesis

ANGELICA M. RIESTRA; NATALIA DE MIGUEL; DANIELE DESSI; AUGUSTO SIMOES-BARBOSA ; FRANCES MERCER

Lifecycles of Pathogenic Protists in Humans

Springer Nature

Año: 2021;

Trichomonas vaginalis is a unicellular, flagellated, microaerophilic protozoan that colonizes the human urogenital tract extracellularly. It causes trichomoniasis, a highly prevalent sexually-transmitted infection (STI) [1-3]. With a global prevalence approaching 400 million [4] and annual new infections globally reported to be 156 million [4], trichomoniasis is the third-most common sexually transmitted infection, exceeded only by HPV (Human Papilloma Virus) and HSV-2 (genital herpes). Discovered in 1836, T. vaginalis was historically considered to be a member of the commensal vaginal microbiome, however its pathogenic properties began to be appreciated about a century later. Still, the symptoms of T. vaginalis infection range from none, to moderate, to severe, putatively due to variation in (1) human immune responses, (2) indigenous vaginal microbes, and (3) the inherent virulence of the strain, including whether the strains harbor any microbial symbionts [5]. In this chapter, we will give a brief description of disease outcomes of T. vaginalis infection, and then discuss the current understanding of the parasite biology and pathogenic mechanisms. Of note, T. vaginalis pathobiology occurs in the presence of the vaginal microbiota, and often with at least one of several parasite symbionts, which we will also discuss to give a more holistic picture. Throughout, we will highlight both noteworthy historical, as well as exciting recent research that has shaped our understanding of T. vaginalis, and point out where technological advances have enabled a deeper understanding of the parasite. We close with a discussion of treatment strategies that T. vaginalis research has informed, and future perspectives for research avenues that will both aid in improved management of trichomoniasis, and develop a more complete understanding of the life of this fascinating organism.