Inducing Immune Protection Against Trichomonas vaginalis: A Novel Vaccine Approach to Prevent HIV Transmission

Human immunodeficiency virus (HIV) infection is a pandemic that affects all parts of the globe. Current treatments fail to cure disease and for this reason there is significant interest in producing a vaccine to prevent HIV transmission, but clinical trials have proved disappointing. For this reason it is important to consider alternative measures to control incidence and prevalence of the disease. Trichomonas vaginalis is a highly prevalent and under-diagnosed sexually transmitted infection that facilitates transmission of and susceptibility to HIV infection (McClelland et al., 2007; Mavedzenge et al., 2010). Although current treatment is effective the disease is still poorly controlled and there are concerns about increasing levels of drug resistance (Upcroft & Upcroft, 2001). Efforts to research disease mechanisms and immune response with consideration to a rational vaccine design approach should be investigated as a potential method to reduce global incidence of T. vaginalis infection. A reliable murine model of T. vaginalis infection has been established with symptoms in female mice mimicking those seen in women (from vaginitis/vulvitis and discharge to asymptomatic but culture-positive for infection). Using this model it has been shown that vaccinating mice (by injection of trichomonad cells with adjuvant) protects the animals from subsequent vaginal infection (Abraham et al., 1996). By studying immune responses in mice, factors that are critical for immunological protection can be elucidated to create a “blueprint” for an effective human vaccine. Herein we provide an overview of the current understanding of T. vaginalis infection and epidemiology, methods of diagnosis and treatment, and implications of animal models for understanding disease mechanisms . We discuss how and why current T. vaginalis treatment protocols fail to control infection incidence with consideration as to how a T. vaginalis vaccine could overcome these obstacles and reduce disease burden. The association between T. vaginalis and HIV is examined and the potential for reducing HIV infection rates by lowering T. vaginalis incidence is elucidated. A vaccine against T. vaginalis would provide long term protection that could be more successful than treatment in controlling the spread of this very common disease. As T. vaginalis infection is a clear risk factor for HIV acquisition, it is our belief that this approach would also be effective in ameliorating HIV incidence and prevalence, especially in areas such as South and Southeast Asia and sub-Saharan Africa where HIV and T. vaginalis are endemic (United Nations, 2009; World Health Organization, 2001).