Commentary: Genetic modulation in lung transplantation: Epic odyssey of vector transduction and transgene expression

Central MessageThe field of lung transplantation embarks on an epic odyssey to explore the feasibility of using the adeno-associated viral vector for improving short- and long-term outcome through genetic donor lung modulation.See Article page e38. The field of lung transplantation embarks on an epic odyssey to explore the feasibility of using the adeno-associated viral vector for improving short- and long-term outcome through genetic donor lung modulation. See Article page e38. Genetic lung modulation is a novel strategy to overcome the challenges that hamper further improvement of lung transplantation (LTx) outcome. We congratulate the authors for embarking on this odyssey in search of an efficient delivery vector and route. Previously, in the field of LTx, adeno- and lentiviral vectors have been investigated.1Oishi H. Juvet S.C. Martinu T. Sato M. Medin J.A. Liu M. et al.A novel combined ex vivo and in vivo lentiviral interleukin-10 gene delivery strategy at the time of transplantation decreases chronic lung allograft rejection in mice.J Thorac Cardiovasc Surg. 2018; 156: 1305-1315Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar,2Okada Y. Zuo X.J. Toyoda M. Marchevsky A. Matloff J.M. Oishi H. et al.Adenovirus mediated IL-10 gene transfer to the airway of the rat lung for prevention of lung allograft rejection.Transpl Immunol. 2006; 16: 95-98Crossref PubMed Scopus (15) Google Scholar However, the adeno-associated viral (AAV) vector is characterized by lower pathogenicity, lower risk for genomic integration, stable transgene expression, and existing clinical applications.3Domenger C. Grimm D. Next-generation AAV vectors-do not judge a virus (only) by its cover.Hum Mol Genet. 2019; 28: R3-R14Crossref PubMed Scopus (73) Google Scholar Kesseli and colleagues4Kesseli S.J. Krischak M.K. Gao Q. Gonzalez T. Zhang M. Halpern S.E. et al.Adeno-associated virus mediates gene transduction after static cold storage treatment in rodent lung transplantation.J Thorac Cardiovasc Surg. 2023; 166: e38-e49Abstract Full Text Full Text PDF Scopus (1) Google Scholar from Duke University assessed for the first time in a syngeneic rat model of orthotopic left LTx the potential to genetically target the donor lung ex vivo with AAV. A low/high dose (8e10/4e11copies) of AAV9 was delivered ex vivo in the bronchus or pulmonary artery, before 60 minutes of static cold storage. Reporter gene expression was assessed with immunohistochemistry after 2 weeks (green fluorescent protein, mCherry) and in vivo or tissue luminescence (Luciferase) up to 2 months after delivery. Bronchial delivery resulted in epithelial expression. Arterial instillation did not result in clear endothelial expression but led to off-target expression in liver and heart.4Kesseli S.J. Krischak M.K. Gao Q. Gonzalez T. Zhang M. Halpern S.E. et al.Adeno-associated virus mediates gene transduction after static cold storage treatment in rodent lung transplantation.J Thorac Cardiovasc Surg. 2023; 166: e38-e49Abstract Full Text Full Text PDF Scopus (1) Google Scholar Viral vector transduction in LTx remains uncharted territory. Every step of this odyssey undertaken by the transgene and its vector, from delivery up to the target cell, requires our detailed understanding. Many challenges lie ahead. Regarding the vector, targeting a specific cell requires a vector with a well-considered cell tropism and delivery route. A wide range of AAV serotypes and capsid variants targeting various cell types is available.3Domenger C. Grimm D. Next-generation AAV vectors-do not judge a virus (only) by its cover.Hum Mol Genet. 2019; 28: R3-R14Crossref PubMed Scopus (73) Google Scholar,5Zinn E. Vandenberghe L.H. Adeno-associated virus: fit to serve.Curr Opin Virol. 2014; 8: 90-97Crossref PubMed Scopus (80) Google Scholar Due to the rate-limiting second-strand synthesis, transgene expression after AAV delivery with a single-stranded genome typically begins after 1 to 2 days, reaching maximal expression at 2 to 4 weeks.6Zincarelli C. Soltys S. Rengo G. Rabinowitz J.E. Analysis of AAV serotypes 1-9 mediated gene expression and tropism in mice after systemic injection.Mol Ther. 2008; 16: 1073-1080Abstract Full Text Full Text PDF PubMed Scopus (951) Google Scholar,7Ding W. Yan Z. Zak R. Saavedra M. Rodman D.M. Engelhardt J.F. Second-strand genome conversion of adeno-associated virus type 2 (AAV-2) and AAV-5 is not rate limiting following apical infection of polarized human airway epithelia.J Virol. 2003; 77: 7361-7366Crossref PubMed Scopus (65) Google Scholar Synthetic vectors like lipid nanoparticles are a nonviral alternative. Their advantage is that they are even less immunogenic and can be loaded with mRNA, enabling more rapid expression kinetics.8Lokugamage M.P. Vanover D. Beyersdorf J. Hatit M.Z.C. Rotolo L. Echeverri E.S. et al.Optimization of lipid nanoparticles for the delivery of nebulized therapeutic mRNA to the lungs.Nat Biomed Eng. 2021; 5: 1059-1068Crossref PubMed Scopus (85) Google Scholar,9Sheridan C. Gene therapy finds its niche.Nat Biotechnol. 2011; 29: 121-128Crossref PubMed Scopus (245) Google Scholar Through bronchial delivery, the vector is directly exposed to the large surface area of bronchiolar and alveolar epithelium. Arterial instillation theoretically favors endothelial transduction but may potentially result in more systemic spread and subsequent off-target effects. In addition, reliably determining the cells that are transduced is pivotal to determine vector tropism. We encourage the use of multiplex fluorescent immunohistochemical labeling to colocalize reporter genes and cell type markers. Delivery during static cold storage is technically less demanding, but ex vivo lung perfusion (EVLP) might provide a beneficial effect on the efficiency of vector cell-entry and transgene expression. EVLP allows ex vivo delivery of the vector while cell metabolism is maintained. Delivery through the perfusate might provide a prolonged and more intricate contact with the target cells. Rodent models will allow further investigation of vector delivery during EVLP.10Hasenauer A. Bédat B. Parapanov R. Lugrin J. Debonneville A. Abdelnour-Berchtold E. et al.Effects of cold or warm ischemia and ex-vivo lung perfusion on the release of damage associated molecular patterns and inflammatory cytokines in experimental lung transplantation.J Heart Lung Transplant. 2021; 40: 905-916Abstract Full Text Full Text PDF PubMed Scopus (9) Google Scholar Gene therapy is already pushing the therapeutic boundaries for many diseases.3Domenger C. Grimm D. Next-generation AAV vectors-do not judge a virus (only) by its cover.Hum Mol Genet. 2019; 28: R3-R14Crossref PubMed Scopus (73) Google Scholar Also, the LTx research community should set sail toward clinical implementation of genetic modulation for improvement of LTx outcomes. Preparing for the challenges ahead, by learning from gene therapy applied in other medical fields, will be key to reach the safe harbor of Ithaka, as depicted in the poem by C. P. Cavafy (Figure 1). Adeno-associated virus mediates gene transduction after static cold storage treatment in rodent lung transplantationThe Journal of Thoracic and Cardiovascular SurgeryVol. 166Issue 1PreviewAdeno-associated virus is a clinically used gene therapy vector but has not been studied in lung transplantation. We sought to determine the efficacy of adeno-associated virus delivery during static cold storage via the airway versus the pulmonary artery before lung transplantation in a rodent model. Full-Text PDF