Undetectable hepatitis C virus RNA during syphilis infection in two HIV/HCV-co-infected patients

Abstract

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.

Keywords::

• HCV
• HIV
• syphilis

Acknowledgements

The authors would like to thank Dr Claus Bohn Christiansen from the Department of Clinical Microbiology at Rigshospitalet for performing the HCV RNA analyses and Microbiological Diagnostics and Virology at Statens Serum Institut for performing the serological syphilis testing.

Declaration of interest: The study did not receive any financial support. However, TK has received research funding and fees for board membership, consultancy and lectures from Gilead, Viiv, Bristol-Myers Squibb, Merck Sharp & Dohme, Abbott, GlaxoSmithKline, Roche, Boehringer Ingelheim, and Janssen. JG has received research funding from Gilead, Viiv, Bristol-Myers Squibb, Merck Sharp & Dohme, Abbott, GlaxoSmithKline, Roche, Boehringer Ingelheim, Janssen and Sanofi-Pasteur. KS, AK, and HK report no conflicts of interest.