Phototherapy-Based Treatment for Sexually Transmitted Infections—Shining Light into Unexplored Territory

Abstract

New therapeutic strategies are urgently needed to overcome drawbacks in the treatment of some infections, particularly sexually transmitted infections (STI). STIs are easily spread by the transmission of various bacteria, viruses, and parasites with some of the infections being incurable or even lethal, leading to a serious impact on reproductive health worldwide. Phototherapy (PT) is a major therapeutic approach based on the controlled administration of light in the visible, near infrared, or UV spectrum, with or without the application of an external photosensitizer. Despite the fact that PT has not been explored to its full potential in the control of STIs, it has already demonstrated good clinical response rates and lower recurrence rates in genital infections. For instance, increasing evidence has demonstrated that 5-aminolevulinic acid photodynamic therapy (5-ALA-PDT) is effective in the treatment of condyloma acuminatum (CA), by eliminating the causative latent human papillomavirus (HPV) infection, and also in the antiviral treatment of recurrent genital herpes simplex virus (HSV) infections. The clinical application of PDT is a new treatment for oral fungal infection caused by Candida albicans in adult acquired immune deficiency syndrome (AIDS) patients, with human immunodeficiency virus (HIV), and could also be used for genital fungal infections. Another antimicrobial PT strategy, water-filtered infrared A combined with visible light irradiation, has been shown to be effective against genital Chlamydia trachomatis bacterial infection, and an optical nano-genosensor has been designed for the diagnosis of trichomoniasis, a parasitic Trichomonas vaginalis infection. This review aims to summarize the published evidence for the effectiveness of PT in the treatment of STIs, and for the suppression of STI-related pathogens of various types.