Plasma interleukin-27 (IL-27) levels are not modulated in patients with chronic HIV-1 infection

Abstract

Objective: IL-27 is an immunomodulatory cytokine with potent anti-HIV properties in PBMCs, CD4+ T cells, macrophages and immature dendritic cells. Previous smaller studies have suggested that HIV-1 infection may alter IL-27 and influence HIV-1 pathogenesis. The aim of this study was to examine the relationship between plasma IL-27 levels in a well-characterised cohort of HIV-1 infected patients.

Methods: Patients were stratified into four groups based on HIV-1 viral load and matched according to age, gender and those receiving antiretroviral treatment. IL-27 levels and C-reactive protein (CRP) were measured using electrochemiluminescence assays. D-dimer and CD4+ T cell counts were measured using an Enzyme Linked Fluorescence Assay and FACS, respectively. sCD14 and sCD163 were measured using ELISA. HIV-1 viral load was measured by bDNA or qRT-PCR assays.

Results: Plasma IL-27 levels were measured in 505 patients (462 HIV+, 43 controls). The mean level (±SEM) of IL-27 in controls was 2990.7±682.1 pg/ml, in the <50 copies/ml group it was 2008.0±274.8 pg/ml, in the 51-10,000 copies group it was 1468.7±172.3 pg/ml, in the 10,001-100,000 copies/ml group it was 1237.9±127.3 pg/ml and in the >100,000 copies/ml group it was 1590.1±223.7 pg/ml. No statistically significant difference in IL-27 levels between groups were seen. There were no correlations noted between IL-27 and HIV-1 viral load or CD4+ T cell counts. There was a small correlation noted between D-dimer and IL-27 (Spearman r = 0.09, p = 0.03) and sCD163 and IL-27 (Spearman r = 0.12, p = 0.005). No correlation was observed between IL-27 and CRP or sCD14 levels.

Conclusions: This is the largest study examining the levels of plasma IL-27 in HIV-1 infection. While IL-27 levels are not significantly altered in HIV-1 infection compared to uninfected controls there may be a small association between IL-27 and D-dimer levels and IL-27 and sCD163 levels.

Figure 1. Measurement of plasma IL-27 levels in HIV-1 infected patients and controls.

In Panel A, IL-27 levels were measured in plasma from HIV-1 negative controls and also in HIV-1 infected patients divided into 4 groups based on viral load (<50 copies/ml, 51–10,000 copies/ml, 10,001–100,000 copies/ml and >100,000 copies/ml). There were no statistically different differences in plasma IL-27 levels between groups (using non parametric Mann Whitney t statistic). HIV-1 positive patients who were on ART were excluded from the analysis (Panel B) and IL-27 levels were compared between groups which came to the same conclusion. There was no correlation noted between IL-27 levels and viral load (Panel C), nor between IL-27 levels and CD4+ T cell counts (Panel D). Inflammatory markers (D-dimer and CRP) were measured in a subset of patients, which revealed a small correlation between IL-27 and D-dimer (Panel E) but no correlation between CRP and IL-27 levels (Panel F).

Figure 2. Correlation of D-dimer and CRP with plasma IL-27 levels.

In Panel A, D-dimer levels were plotted for each group of patients (stratified by viral load). There was a statistically significant trend towards increasing D-dimer levels with rising levels of HIV-1 viral load. D-dimer was then correlated with IL-27 levels and a Spearman r showed no statistically significant correlation (Panel B). In Panel C, CRP levels were plotted for each group of patients and there was a trend towards increasing levels with rising HIV-1 viral loads. When IL-27 was plotted against CRP (Panel D), there was no significant correlation noted between these two parameters.

Figure 3. Correlation of sCD14 and sCD163 with plasma IL-27 levels.

Plasma sCD14 levels, like the other markers of immune activation, were elevated in HIV-1 viremic patients compared to healthy controls (Panel A). Levels of sCD14 and plasma IL-27 levels were plotted (Panel B) but no correlation was observed. Plasma sCD163 levels were elevated in HIV-1 viremic patients compared to healthy controls (Panel C), with a trend towards higher levels of sCD14 with higher HIV-1 viral loads. Levels of sCD163 and plasma IL-27 levels were plotted (Panel B) and, unlike the other markers measured, there was a significant Spearman r noted (Spearman r = 0.12, p = 0.005) (Panel D).