title: 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.
authors.affiliation: From the Department of Infectious Diseases, Copenhagen University Hospital , Rigshospitalet, Copenhagen , Denmark.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Salado-Rasmussen
authors.forename: Andreas
authors.initials: A
authors.lastname: Knudsen
authors.forename: Henrik Bygum
authors.initials: HB
authors.lastname: Krarup
authors.forename: Terese Lea
authors.initials: TL
authors.lastname: Katzenstein
authors.forename: Jan
authors.initials: J
authors.lastname: Gerstoft
mesh_terms: D000328:Adult; D016207:Cytokines / Q000097:blood; D015658:HIV Infections / Q000150:complications*; D016174:Hepacivirus / Q000302:isolation & purification*; D019698:Hepatitis C, Chronic / Q000150:complications* / Q000821:virology*; D006801:Humans; D008297:Male; D012367:RNA, Viral / Q000097:blood*; D013587:Syphilis / Q000150:complications* / Q000276:immunology*; D014210:Treponema pallidum / Q000276:immunology
chemical_list: D016207:Cytokines; D012367:RNA, Viral
keywords: HCV; HIV; syphilis