Circulating interleukin-6 levels correlate with residual HIV viraemia and markers of immune dysfunction in treatment-controlled HIV-infected patients.

BACKGROUND: Antiretroviral therapy (ART)-controlled HIV-infected patients have elevated levels of systemic inflammatory markers, C-reactive protein (CRP) and interleukin (IL)-6, which correlate with increased cardiovascular risk and/or mortality. Persistent low-level viral replication could be involved in this inflammatory state. We evaluated whether residual viral load (VL) correlated with the level of systemic inflammatory/immune markers in ART-controlled HIV-infected patients.
METHODS: We evaluated 122 antiretroviral-controlled patients with VL 1-500 copies/ml for circulating levels of high-sensitivity (hs)CRP, hsIL-6, IL-8, soluble (s)CD14 and soluble tumour necrosis factor (TNF) receptors, sTNFR1 and sTNFR2.
RESULTS: The patients were 80.3% men, the median age was 47 years, the median CD4(+) T-cell count was 519 cells/mm(3), the median nadir CD4(+) T-cell count was 180 cells/mm(3), the median VL was 28 copies/ml and the median body mass index was 23.3 kg/m(2). The median (range) values for IL-6, CRP, IL-8, sCD14, sTNFR1 and sTNFR2 were 0.685 pg/ml (0.15-5.46), 1.8 mg/l (0.2-9.7), 10.0 pg/ml (1.6-71.1), 1,174 ng/ml (214-3,145), 1,112 pg/ml (583-5,834) and 2,412 pg/ml (1,142-7,688), respectively. IL-6 values correlated positively with HIV VL (rho=0.217, P=0.017). The VL threshold value for significantly increased IL-6 was 31 copies/ml (P=0.023). IL-6 values correlated with markers of immune dysfunction: the CD4/CD8 ratio (rho=-0.248, P=0.011), CD4 nadir level (rho=-0.186, P=0.04) and nadir CD4/CD8 ratio (rho=-0.257, P=0.008). They negatively correlated with markers of immune activation sCD14 (rho=-0.236, P=0.011) and IL-8 (rho=-0.290, P=0.002). We found no correlation between VL and CRP or other markers of inflammation/immune dysfunction including sTNFR1, sTNFR2, sCD14 and IL-8.
CONCLUSIONS: We report here that low-range IL-6 levels correlated with low-range VL and inversely with sCD14 and IL-8. Our findings suggest that maintaining VL<30 copies/ml in HIV-infected patients might therefore reduce IL-6.