The administration route is decisive for the ability of the vaccine adjuvant CAF09 to induce antigen-specific CD8+ T-cell responses:the immunological consequences of the biodistribution profile

A prerequisite for vaccine-mediated induction of CD8+ T-cell responses is the targeting of dendritic cell (DC) subsets specifically capable of cross-presenting antigen epitopes to CD8+ T cells. Administration of a number of cationic adjuvants via the intraperitoneal (i.p.) route has been shown to result in strong CD8+ T-cell responses, whereas immunization via e.g. the intramuscular (i.m.) or subcutaneous (s.c.) routes often stimulate weak CD8+ T-cell responses. The hypothesis for this is that self-drainage of the adjuvant/antigen to the lymphoid organs, which takes place upon i.p. immunization, is required for the subsequent activation of cross-presenting lymphoid organ-resident CD8α+ DCs. In contrast, s.c. or i.m. immunization usually results in the formation of a depot at the site of injection (SOI), which hinders the self-drainage and targeting of the vaccine to cross-presenting CD8α+ DCs. We investigated this hypothesis by correlating the biodistribution pattern and the adjuvanticity of the strong CD8+ T-cell inducing liposomal cationic adjuvant formulation 09 (CAF09), which is composed of dimethyldioctadecylammonium bromide/monomycoloyl glycerol liposomes with polyinosinic:polycytidylic acid electrostatically adsorbed to the surface. Biodistribution studies with radiolabeled CAF09 and a surface-adsorbed model antigen [ovalbumin (OVA)] showed that a significantly larger fraction of the vaccine dose localized in the draining lymph nodes (dLNs) and the spleen 6 h after i.p. immunization, as compared to after i.m. immunization. Studies with fluorescently labelled OVA + CAF09 demonstrated a preferential association of OVA + CAF09 to DCs/monocytes, as compared to macrophages and B cells, following i.p. immunization. Administration of OVA + CAF09 via the i.p. route did also result in DC activation, whereas no DC activation could be measured within the same period with unadjuvanted OVA and OVA + CAF09 administered via the s.c. or i.m. routes. In the dLNs, the highest level of activated, cross-presenting CD8α+ DCs was detected at 24 h post immunization, whereas an influx of activated, migrating and cross-presenting CD103+ DCs to the dLNs could be measured after 48 h. This suggests that the CD8α+ DCs are activated by self-draining OVA + CAF09 in the lymphoid organs, whereas the CD103+ DCs are stimulated by the OVA + CAF09 at the SOI. These results support the hypothesis that the self-drainage of OVA + CAF09 to the draining LNs is required for the activation of CD8α+ DCs, while the migratory CD103+ DCs may play a role in sustaining the subsequent induction of strong CD8+ T-cell responses.

Hydroxylases regulate intestinal fibrosis through the suppression of ERK mediated TGF-β1 signaling

Fibrosis is a complication of chronic inflammatory disorders such as inflammatory bowel disease (IBD), a condition which has limited therapeutic options and often requires surgical intervention. Pharmacologic inhibition of oxygen-sensing prolyl hydroxylases (PHD), which confer oxygen-sensitivity upon the hypoxia inducible factor (HIF) pathway, has recently been shown to have therapeutic potential in colitis, although the mechanisms involved remain unclear. Here, we investigated the impact of hydroxylase inhibition on inflammation-driven fibrosis in a murine colitis model. Mice exposed to dextran sodium sulfate followed by period of recovery developed intestinal fibrosis characterized by alterations in the pattern of collagen deposition and infiltration of activated fibroblasts. Treatment with the hydroxylase inhibitor dimethyloxalylglycine (DMOG) ameliorated fibrosis. TGF-β1 is a key regulator of fibrosis which acts through the activation of fibroblasts. Hydroxylase inhibition reduced TGF-β1-induced expression of fibrotic markers in cultured fibroblasts suggesting a direct role for hydroxylases in TGF-β1 signalling. This was at least in part due to inhibition of non-canonical activation of extracellular signal-regulated kinase (ERK) signalling. In summary, pharmacologic hydroxylase inhibition ameliorates intestinal fibrosis, through suppression of TGF-β1-dependent ERK activation in fibroblasts. We hypothesize that in addition to previously reported immunosupressive effects, hydroxylase inhibitors independently suppress pro-fibrotic pathways