Update on Bronchiolitis Obliterans Syndrome in Lung Transplantation

α1-Antitrypsin attenuates acute rejection of orthotopic murine lung allografts

Background

α1-Antitrypsin (AAT) is an acute phase glycoprotein, a multifunctional protein with proteinase inhibitory, anti-inflammatory and cytoprotective properties. Both preclinical and clinical experiences show that the therapy with plasma purified AAT is beneficial for a broad spectrum of inflammatory conditions. The potential effects of AAT therapy have recently been highlighted in lung transplantation (LuTx) as well.

Methods

We used a murine fully mismatched orthotopic single LuTx model (BALB/CJ as donors and C57BL/6 as recipients). Human AAT preparations (5 mg, n = 10) or vehicle (n = 5) were injected to the recipients subcutaneously prior to and intraperitoneally immediately after the LuTx. No immune suppressive drugs were administered. Three days after the transplantation, the mice were sacrificed, and biological samples were assessed.

Results

Histological analysis revealed significantly more severe acute rejection in the transplanted lungs of controls than in AAT treated mice (p < 0.05). The proportion of neutrophil granulocytes, B cells and the total T helper cell populations did not differ between two groups. There was no significant difference in serum CXCL1 (KC) levels. However, when compared to controls, human AAT was detectable in the serum of mice treated with AAT and these mice had a higher serum anti-elastase activity, and significantly lower proportion of Th1 and Th17 among all Th cells. Cleaved caspase-3-positive cells were scarce but significantly less abundant in allografts from recipients treated with AAT as compared to those treated with vehicle.

Conclusion

Therapy with AAT suppresses the acute rejection after LuTx in a mouse model. The beneficial effects seem to involve anti-protease and immunomodulatory activities of AAT.

Incidence and risk factors for respiratory tract bacterial colonization and infection in lung transplant recipients

To evaluate incidence of and risk factors for respiratory bacterial colonization and infections within 30 days from lung transplantation (LT). We retrospectively analyzed microbiological and clinical data from 94 patients transplanted for indications other than cystic fibrosis, focusing on the occurrence of bacterial respiratory colonization or infection during 1 month of follow-up after LT. Thirty-three percent of patients developed lower respiratory bacterial colonization. Bilateral LT and chronic heart diseases were independently associated to a higher risk of overall bacterial colonization. Peptic diseases conferred a higher risk of multi-drug resistant (MDR) colonization, while longer duration of aerosol prophylaxis was associated with a lower risk. Overall, 35% of lung recipients developed bacterial pneumonia. COPD (when compared to idiopathic pulmonary fibrosis, IPF) and higher BMI were associated to a lower risk of bacterial infection. A higher risk of MDR infection was observed in IPF and in patients with pre-transplant colonization and infections. The risk of post-LT respiratory infections could be stratified by considering several factors (indication for LT, type of LT, presence of certain comorbidities, and microbiologic assessment before LT). A wider use of early nebulized therapies could be useful to prevent MDR colonization, thus potentially lowering infectious risk.