Diminished frequency of hepatitis C virus specific interferon γ secreting CD4+ T cells in human immunodeficiency virus hepatitis C virus coinfected patients

Background: Human immunodeficiency virus/hepatitis C virus (HIV/HCV) coinfection is a common and complex clinical problem in which loss of immunological control of HCV occurs, with increased HCV viral load and more aggressive liver disease. Cellular immune responses, particularly secretion of interferon c (IFN-gamma) appear to be important in the control of HCV, and a detectable HCV specific CD4 response is associated with clearance of the virus. HCV specific CD8+ T cell responses, weak in chronic HCV infection, have been shown to be further impaired in HIV coinfection and this CD8+ T cell deficiency is related to the decline in CD4 T cell count. Aims: To compare the CD4 T cell response to HCV in HIV/HCV coinfected and HCV monoinfected individuals and to determine the relationship of responses with declining CD4 count. Patients: The study subjects were a cohort of 68 HCV monoinfected and 67 HCV/HIV coinfected haemophiliac children and adolescents (the Hemophilia Growth and Development Study) who were followed for a seven year period. Methods: We analysed IFN-gamma secreting CD4+ responses to HCV proteins and peptides and HIV p24 antigen using an ELISpot assay. Results: We found a significant decrease in HCV specific responses among those who were HIV coinfected (10/67 v 36/68; p < 0.0001) both in numbers of responders and frequency of specific cells. This did not appear to be closely related to CD4 count. Conclusions: The reduction in HCV specific CD4 T cells in coinfection provide a cellular mechanism for the loss of control of HCV in coinfected individuals, even in those with relatively preserved CD4+ T cell counts and CD4+ T cell responses to HIV.