The Effects of Tumstatin on Vascularity, Airway Inflammation and Lung Function in an Experimental Sheep Model of Chronic Asthma.

Tumstatin, a protein fragment of the alpha-3 chain of Collagen IV, is known to be significantly reduced in the airways of asthmatics. Further, there is evidence that suggests a link between the relatively low level of tumstatin and the induction of angiogenesis and inflammation in allergic airway disease. Here, we show that the intra-segmental administration of tumstatin can impede the development of vascular remodelling and allergic inflammatory responses that are induced in a segmental challenge model of experimental asthma in sheep. In particular, the administration of tumstatin to lung segments chronically exposed to house dust mite (HDM) resulted in a significant reduction of airway small blood vessels in the diameter range 10(+)-20 µm compared to controls. In tumstatin treated lung segments after HDM challenge, the number of eosinophils was significantly reduced in parenchymal and airway wall tissues, as well as in the bronchoalveolar lavage fluid. The expression of VEGF in airway smooth muscle was also significantly reduced in tumstatin-treated segments compared to control saline-treated segments. Allergic lung function responses were not attenuated by tumstatin administration in this model. The data are consistent with the concept that tumstatin can act to suppress vascular remodelling and inflammation in allergic airway disease.

Activation of protease-activated receptors (PARs)-1 and -2 promotes alpha-smooth muscle actin expression and release of cytokines from human lung fibroblasts.

Previous studies have shown that protease-activated receptors (PARs) play an important role in various physiological processes. In the present investigation, we determined the expression of PARs on human lung fibroblasts (HLF-1) and whether they were involved in cellular differentiation and pro-inflammatory cytokine and prostaglandin (PGE2) secretion. PAR-1, PAR-2, PAR-3, and PAR-4 were detected in fibroblasts using RT-PCR, immunocytochemistry, and flow cytometry. Increased expression of PAR-4, but not other PARs, was observed in fibroblasts stimulated with phorbol myristate acetate. The archetypical activators of PARs, namely, thrombin and trypsin, as well as PAR-1 and PAR-2 agonist peptides, stimulated transient increases in intracellular Ca(2+), and promoted increased α-smooth muscle actin expression. The proteolytic and peptidic PAR activators also stimulated the release of IL-6 and IL-8, as well as PGE2, with a rank order of potency of PAR-1 > PAR-2. The combined stimulation of PAR-1 and PAR-2 resulted in an additive release of both IL-6 and IL-8. In contrast, PAR-3 and PAR-4 agonist peptides, as well as all the PAR control peptides examined, were inactive. These results suggest an important role for PARs associated with fibroblasts in the modulation of inflammation and remodeling in the airway.

ISCOMATRIX™ adjuvant reduces mucosal tolerance for effective pulmonary vaccination against influenza.

While most pathogens infect via mucosal surfaces, most current vaccines are delivered by injection. This situation remains despite awareness of the potential benefits of mucosal delivery for inducing protection against mucosa-infecting pathogens. A major obstacle to the development of such vaccines is the paucity of safe and effective adjuvants that induce mucosal responses in non-rodents. Previously we demonstrated in sheep the potency of pulmonary-delivered influenza ISCOMATRIX™ vaccine, which induces both mucosal and systemic immunity, even with low antigen doses. In the current study, lung pre-exposure to influenza antigen alone significantly reduced the immune response to subsequent pulmonary-delivered influenza ISCOMATRIX™ vaccine. A single dose of influenza antigen, delivered to the lung without exogenous adjuvant, upregulated IL-10 expression in bronchoalveolar lavage cells and FOXP3 expression in lung tissue, suggestive of induction of a regulatory T cell (Treg) response. However, this effect was inhibited by addition of ISCOMATRIX™ adjuvant. Moreover, effective pulmonary immunization with influenza ISCOMATRIX™ vaccine was associated with a depletion of Treg markers within lung tissues. Lung exposure to influenza antigen induced a localized mucosal tolerance that reduced the efficacy of subsequent influenza ISCOMATRIX™ vaccination. An important role of ISCOMATRIX™ adjuvant in pulmonary vaccination appears to be the depletion of Treg in lung tissues. Pulmonary vaccination remains capable of inducing a strong immune response against mucosal pathogens, but likely requires an adjuvant to overcome mucosal tolerance. ISCOMATRIX™ appears to have considerable potential as a mucosal adjuvant for use in humans, a major unmet need in mucosal vaccine development.