Intestinal Epithelial Cell-Specific Deletion of PLD2 Alleviates DSS-Induced Colitis by Regulating Occludin

Ulcerative colitis is a multi-factorial disease involving a dysregulated immune response. Disruptions to the intestinal epithelial barrier and translocation of bacteria, resulting in inflammation, are common in colitis. The mechanisms underlying epithelial barrier dysfunction or regulation of tight junction proteins during disease progression of colitis have not been clearly elucidated. Increase in phospholipase D (PLD) activity is associated with disease severity in colitis animal models. However, the role of PLD2 in the maintenance of intestinal barrier integrity remains elusive. We have generated intestinal specific Pld2 knockout mice (Pld2 IEC-KO) to investigate the mechanism of intestinal epithelial PLD2 in colitis. We show that the knockout of Pld2 confers protection against dextran sodium sulphate (DSS)-induced colitis in mice. Treatment with DSS induced the expression of PLD2 and downregulated occludin in colon epithelial cells. PLD2 was shown to mediate phosphorylation of occludin and induce its proteasomal degradation in a c-Src kinase-dependent pathway. Additionally, we have shown that treatment with an inhibitor of PLD2 can rescue mice from DSS-induced colitis. To our knowledge, this is the first report showing that PLD2 is pivotal in the regulation of the integrity of epithelial tight junctions and occludin turn over, thereby implicating it in the pathogenesis of colitis

Phase I/II trial of a dendritic cell vaccine transfected with DNA encoding melan A and gp100 for patients with metastatic melanoma

This trial tested a dendritic cell (DC) therapeutic cancer vaccine in which antigen is loaded using a novel non-viral transfection method enabling the uptake of plasmid DNA condensed with a cationic peptide. Proof of principle required the demonstration of diverse T lymphocyte responses following vaccination, including multiple reactivities restricted through both major histocompatibility complex (MHC) class I and II. Patients with advanced melanoma were offered four cycles of vaccination with autologous DC expressing melan A and gp100. Disease response was measured using Response Evaluation Criteria in Solid Tumours. Circulating MHC class I- and II-restricted responses were measured against peptide and whole antigen targets using interferon-γ ELIspot and enzyme-linked immunosorbent assay assays, respectively. Responses were analyzed across the trial population and presented descriptively for some individuals. Twenty-five patients received at least one cycle. Vaccination was well tolerated. Three patients had reduction in disease volume. Across the trial population, vaccination resulted in an expansion of effector responses to both antigens, to the human leukocyte antigen A2-restricted modified epitope, melan A ELAGIGILTV, and to a panel of MHC class I- and II-restricted epitopes. Vaccination with mature DC non-virally transfected with DNA encoding antigen had biological effect causing tumour regression and inducing diverse T lymphocyte responses