Background: Incidences of chronic rejection, bronchiolitis obliterans syndrome (BOS), remain a major challenge to lung transplantation and development of allo- and auto-immunity has been proposed as a mechanism for the development of BOS. In this study, using a murine model of anti-MHC induced obliterative airway disease (OAD) we examined early events following administration of MHC class I antibodies (Abs).

Methods: Using a murine OAD model induced by anti-MHC class I, we determined molecular signatures arising from MHC-I cross-linking. MHC-I Ab treated lungs were analyzed by gene-chip assay at 4, 28, 52 and 76 h post cross-linking and compared with that of control Abs. Further, profile of lung leukocytes was evaluated by flow cytometry to fractionate T cell, B cell, natural killer cell, macrophage, neutrophil and eosinophil populations. Target validation was performed by quantitative PCR and five candidate genes were chosen to study further in lentivirus based in vivo knockdown approach for their role in OAD.

Results: Analysis of the OAD lung transcriptome indicated significant up-regulation of 14 genes as early as 4 h post administration of MHC-I Abs. Of those, expression of five most prominent genes including Zinc finger and BTB domain containing 7A (Zbtb7a), metallothionein 1 (Mt1), lysosomal-associated protein transmembrane 5 (Laptm5), bradykinin receptor beta 1 (Bdkrb1) and PDZ domain containing 2 (Pdzd2) were validated. Mice receiving intratracheal small interfering RNA (siRNA) based lentivirus had significant reduction in target gene expression and were evaluated in Ab mediated OAD development. Our preliminary finding is that downregulation of Zbtb7a significantly decreased lung tropic CD4 T cells that coincided with lower Ka1Tubulin and Collagen V specific auto-Abs, and IL-17 and IFN-γ secreting T cells. Additionally, there was a marked decrease in OAD lesion in the siRNA-Zbtb7a mice indicating its role in pathogenesis. The siRNA-Mt1 mice also demonstrated a reduction in OAD pathology and exhibited a higher percentage of regulatory T cells.

Conclusion: Using a murine model of anti-MHC- I induced OAD, we have identified 14 genes that are up-regulated preceding development of OAD. We also demonstrated that selective knockdown of Zbtb7a and Mt1 conferred resistance to Ab induced OAD respectively by limiting spread of CD4 T cells and eliciting regulatory T cells.

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