Introduction We have identified a group of high risk injection drug users who share needles, syringes and other injecting paraphernalia over a long period of time yet who remain uninfected by hepatitis C virus (HCV). These individuals appear to be resistant to HCV infection and we have termed them exposed uninfected (EU). Defining factors that may prevent HCV infection in these cohorts could give valuable insight into the mechanisms of natural resistance to HCV.
Method Individuals at high risk of recurrent exposure to HCV infection from long term IDU were recruited in Plymouth and if HCV antibody and HCV RNA negative were termed exposed uninfected (EU). We have compared the transcriptional profiles of intravenous drug users (IDU) with 3 different outcomes following HCV exposure – chronic hepatitis C infection (CHCV; n = 6), spontaneously resolution of HCV (SR; HCV Ab positive but HCV RNA negative, n = 6) and exposed but uninfected (EU; n = 6). Agilent single channel microarray was performed on RNA isolated from peripheral blood mononuclear cells and the results were analysed on Ingenuity Pathway Analysis software (Qiagen). The identified targets were subsequently validated at a protein level.
Results 1465 genes between the EU and CHCV group, 4377 between the CHCV and SR group and 4510 between the SR and EU group were significantly up or down regulated. Of the differentially regulated genes, the association with resistance to HCV was strongest for IL27 and CXCL7 which were significantly upregulated in EU (IL27 log fold change EU vs SR: 1.943, p = 1.72E-04 and CXCL7 log fold change EU vs CHCV 2.359, p = 6.04E-03) relative to the other 2 groups. At a protein level, the median IL27 serum level in the EU group (n = 13), detected by sandwich ELISA, was significantly higher (p = 0.008) compared to CHCV (n = 14), healthy control (HC; n = 8) and SR (n = 14) groups. The CD28 mediated T-helper cell signalling pathway was significantly upregulated in SR (ratio 0.348, p = 2.77E-05) relative to the 2 other groups.
Conclusion Significant differences in gene expression were found in injection drug users with different outcomes from exposure to HCV infection. EU and SR exhibit differences related to innate and adaptive immunity compared to CHCV that likely contribute to natural resistance and spontaneous clearance of HCV.
Disclosure of interest None Declared.