Transcription profiling of Hepatitis C – specific natural CD25pos cells

We reported previously that a proportion of natural CD25+ cells isolated from the PBMC of HCV patients can further upregulate CD25 expression in response to HCV peptides stimulation in vitro, and proposed that virus-specific regulatory T cells (Treg) were primed and expanded during the disease. Here we describe epigenetic analysis of the FOXP3 locus in HCV-responsive natural CD25+ cells and show that these cells are not activated conventional T cells expressing FOXP3, but hard-wired Treg with a stable FOXP3 phenotype and function. Of ~46,000 genes analyzed in genome wide transcription profiling, about 1% were differentially expressed between HCV-responsive Treg, HCV-non-responsive natural CD25+ cells and conventional T cells. Expression profiles, including cell death, activation, proliferation and transcriptional regulation, suggest a survival advantage of HCV-responsive Treg over the other cell populations. Since no Treg-specific activation marker is known, we tested 97 NS3-derived peptides for their ability to elicit CD25 response (assuming it is a surrogate marker), accompanied by high resolution HLA typing of the patients. Some reactive peptides overlapped with previously described T cell epitopes. Our data offers new insights into HCV immune evasion and tolerance and highlights the non-self specific nature of Treg during infection. We analysed 6 patients, 3 different cell fractions in each patient, thus there are 18 RNA samples in total. Illumina Sentrix Human-6 Expression BeadChip-v2.0 was used for the hybridization. The microarray experiments were performed commercially by the Australia Genome Research Facility.