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Keywords:

  • B lymphocytes;
  • hepatitis C virus;
  • patients;
  • immunoglobulins

Abstract

To clarify whether some of the functions of B lymphocytes could be affected during hepatitis C virus (HCV) infection, phenotypic characteristics of B lymphocytes from HCV-infected patients and their capacity to differentiate into immunoglobulins (Ig)-secreting cells were studied. B lymphocytes differentiation was investigated for patients untreated and non-responders (n = 9), treated and non-responders (n = 6), responders (n = 6), long-term responders (n = 9) to therapy and seronegative controls (n = 14) following in vitro stimulation with S. aureus strain Cowan I mitogen. HCV sequences in purified B lymphocytes were detected by RT-PCR. It was found that HCV-patients harbor a similar mean percentage of B cells and a normal level of naïve B cells (% IgM+/IgD+ cells = 79.7 ± 15.4 for untreated non-responders, 57.1 ± 22.9 for treated non-responders, 44.3 ± 29.1 for responders, 75.7 ± 16 for long-term responders) as compared with controls. It was also found that peripheral blood mononuclear cells (PBMCs) of patients or controls produced similar amounts of IgG, A, and M in vitro. A total of 57% of untreated non-responders versus 17% of treated non-responders were able to produce HCV-specific antibodies. Interestingly, B lymphocytes from PBMCs able to secrete anti-HCV antibodies contained HCV positive strand RNA, although no systematic detection of the negative strand was found. These data suggest that signaling through the B cell receptor (BCR) in B lymphocytes of HCV-infected patients appears normal whatever their response to therapy. The capacity to secrete HCV-specific IgG seemed to be linked to the presence of positive strand RNA rather than virus replication. J. Med. Virol. 72:566–574, 2004. © 2004 Wiley-Liss, Inc.