Insulin is a major target for the autoimmune-mediated destruction of pancreatic β cells during the pathogenesis of type I diabetes. A plasmid DNA vaccine encoding mouse proinsulin II reduced the incidence of diabetes in a mouse model of type I diabetes when administered to hyperglycemic (therapeutic mode) or normoglycemic (prophylactic mode) NOD mice. Therapeutic administration of proinsulin DNA was accompanied by a rapid decrease in the number of insulin-specific IFN-γ-producing T cells, whereas prophylactic treatment was accompanied by enhanced IFN-γ-secreting cells and a decrease in insulin autoantibodies. Adoptive transfer experiments demonstrated that the protection was not mediated by induction of CD25+/CD4+ T regulatory cells. The efficacy of the DNA vaccine was enhanced by increasing the level of expression of the encoded Ag, more frequent dosing, increasing dose level, and localization of the protein product to the intracellular compartment. The efficacy data presented in this study demonstrate that Ag-specific plasmid DNA therapy is a viable strategy for preventing progression of type I diabetes and defines critical parameters of the dosing regime that influences tolerance induction.

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In patients dying from asthma, extensive mucous plugging occurs in the airways, associated with goblet cell hyperplasia. In this study, we examined the hypothesis that platelet-activating factor (PAF) induces goblet cell hyperplasia and mucin gene expression. After instilling PAF into the airways of guinea pigs and rats, we stained airway goblet cells with Alcian blue/periodic acid-Schiff and determined the number of goblet cells and percentage of stained area within the epithelium. In guinea pigs, one instillation of PAF (10(-)5 M, 100 microl) increased the goblet cell-stained area time-dependently, beginning at 24 h, maximum at 72 h. PAF also caused tracheal recruitment of eosinophils by 24 h, maximum at 48 h. In rats, which have few goblet cells in airways, PAF (3 instillations, 10(-)5 M, 200 microl) caused striking goblet cell hyperplasia, greatest in peripheral airways. Tumor necrosis factor alpha (TNFalpha) alone had no significant effect on goblet cells, but together with PAF, it caused exaggerated goblet cell hyperplasia. In rat tracheas studied by in situ hybridization, PAF induced mucin MUC5 gene expression in epithelial cells that stained for mucosubstances. In summary, PAF induces goblet cell hyperplasia and TNFalpha potentiates this effect.

Mucus hypersecretion is a common characteristic of asthma. Acute severe asthma is often associated with neutrophilic infiltration into airways. Neutrophils contain elastase, a potent secretagogue in airways. Therefore, we hypothesized that instillation of ovalbumin in sensitized guinea pigs causes goblet cell secretion by releasing elastase from recruited neutrophils. When we instilled ovalbumin into the trachea of ovalbumin-sensitized guinea pigs, early recruitment of neutrophils identified by 3,3'- diaminobenzidine staining, and goblet cell degranulation measured with a semiautomatic computer-based imaging system occurred. The Leumedin NPC 15669 (a drug that inhibits leukocyte recruitment) and an antibody to intercellular adhesion molecule-1 (ICAM-1) both prevented neutrophil recruitment and goblet cell degranulation, implicating leukocytes in the response. Using immunofluorescence we showed that the leukocytes recruited early after antigen challenge were CD-16-positive, implicating neutrophils. Pretreatment with the selective neutrophil elastase inhibitor ICI 200,355 also prevented ovalbumin-induced goblet cell degranulation, implicating elastase. We conclude that ovalbumin-induced goblet cell degranulation is due to neutrophil recruitment and elastase release.