1 Department of Clinical Medicine, Department of Clinical Medicine, Faculty of Health and Medical Sciences, Københavns Universitet2 unknown3 Graduate School of Health and Medical Sciences, Faculty of Health and Medical Sciences, Københavns Universitet4 Graduate School of Health and Medical Sciences, Faculty of Health and Medical Sciences, Københavns Universitet5 Department of Clinical Medicine, Department of Clinical Medicine, Faculty of Health and Medical Sciences, Københavns Universitet
BACKGROUND: Treponema pallidum, the causative agent of syphilis, elicits a vigorous immune response in the infected host. This study sought to describe the impact of syphilis infection on hepatitis C virus (HCV) RNA levels in patients with HIV and chronic HCV infection. METHODS: Patients with chronic HIV/HCV and syphilis co-infection were identified by their treating physicians from 1 October 2010 to 31 December 2013. Stored plasma samples obtained before, during, and after syphilis infection were analysed for interleukin (IL)-2, IL-4, IL-6, IL-8, IL-10, tumour necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), and IFN-γ-inducible protein 10 kDa (IP-10). RESULTS: Undetectable HCV RNA at the time of early latent syphilis infection was observed in 2 patients with HIV and chronic HCV infection. After treatment of the syphilis infection, HCV RNA levels increased again in patient 1, whereas patient 2 initiated HCV therapy and remained HCV RNA-negative. Available plasma samples obtained before and after the episode with undetectable HCV RNA were phylogenetically identical, making the possibility of spontaneous clearance and HCV reinfection less likely. The IL-10, TNF-α, and IP-10 levels increased at the time of syphilis diagnosis in patient 1 and decreased again after treatment of the syphilis infection. CONCLUSIONS: We propose that T. pallidum-induced cytokine secretion resulted in an immune response hindering HCV replication during syphilis infection. We suggest that HIV/HCV-co-infected patients with unexpected undetectable HCV RNA are tested for syphilis infection and that the serological tests include both non-treponemal and treponemal tests to avoid false-positive results caused by HCV.
Scandinavian Journal of Infectious Diseases, 2014, Vol 46, Issue 9, p. 617-623