IL-27 is formed by the association of a cytokine subunit, p28, with the soluble cytokine receptor EBV-induced gene 3 (EBI3). The IL-27R comprises gp130 and WSX-1. The marked difference between EBI3−/− and WSX-1−/− mice suggests that p28 has functions independent of EBI3. We have identified an alternative secreted complex formed by p28 and the soluble cytokine receptor cytokine-like factor 1 (CLF). Like IL-27, p28/CLF is produced by dendritic cells and is biologically active on human NK cells, increasing IL-12- and IL-2-induced IFN-γ production and activation marker expression. Experiments with Ba/F3 transfectants indicate that p28/CLF activates cells expressing IL-6Rα in addition to the IL-27R subunits. When tested on CD4 and CD8 T cells, p28/CLF induces IL-6Rα-dependent STAT1 and STAT3 phosphorylation. Furthermore, p28/CLF inhibits CD4 T cell proliferation and induces IL-17 and IL-10 secretion. These results indicate that p28/CLF may participate in the regulation of NK and T cell functions by dendritic cells. The p28/CLF complex engages IL-6R and may therefore be useful for therapeutic applications targeting cells expressing this receptor. Blocking IL-6R using humanized mAbs such as tocilizumab has been shown to be beneficial in pathologies like rheumatoid arthritis and juvenile idiopathic arthritis. The identification of a new IL-6R ligand is therefore important for a complete understanding of the mechanism of action of this emerging class of immunosuppressors.

Stopping long-term nucleos(t)ide analogue therapy increases hepatitis B virus (HBV) surface antigen (HBsAg) loss rates in HBV e antigen (HBeAg)-negative patients. Viral rebound may induce immune responses facilitating functional cure. We analyzed which factors are associated with timing of virological relapse in 220 Asian HBeAg-negative patients from the prospective ABX203 vaccine study. Unexpectedly, only the type of antiviral therapy was significantly associated with early virological relapse, defined as an HBV DNA load of >2000 IU/mL until week 12, and relapse occurred earlier in patients treated with tenofovir versus those treated with entecavir (median time, 6 vs 24 weeks; P < .0001). This should be considered for future trials and monitoring of patients after treatment discontinuation.

We have assessed the immune-regulatory and adjuvant activities of a synthetic glycolipid, ABX196, a novel analog of the parental compound α-GalCer. As expected, ABX196 demonstrated a measurable and significant adjuvant effect in mice and monkeys with no appreciable toxicity at the doses used to promote immune responses. We performed a phase I/II dose escalation study of ABX196 in healthy volunteers, with the objectives to evaluate its safety profile, as well as its ability to be utilized as an adjuvant in the context of a prophylactic vaccine against hepatitis B. ABX196 was administered at three doses: 0.2, 0.4, and 2.0µg, in fourty-four subjects. In all individuals injected with ABX196, peripheral blood NKT cells displayed hallmarks of activation, and 45% of them had measurable circulating IFN-γ 24 hours after the first administration. More importantly, the addition of ABX196 to the very poorly immunogenic HBs antigen resulted in protective anti-HBs antibody responses in a majority of patients, demonstrating the adjuvant properties of ABX196 in human. Further analysis of the cohort of subjects receiving ABX196 with HBs antigen also indicates that a single injection appears sufficient to provide protection. A limited set of adverse events linked to the systemic delivery of ABX196 and access to the liver, is discussed in the context of formulation and the need to limit transport of ABX196 to secondary lymphoid tissues for maximal efficacy (Eudra-CT 2012-001566-15).