Dixita Viswanath

Introduction.  Wiskott-Aldrich syndrome (WAS) is a severe primary immunodeficiency caused by a mutation in WAS-protein (WASp) which regulates actin polymerization and cytoskeleton reorganization in cytotoxic hematopoietic immune cells¹.WAS presents in early infancy and often progresses to autoimmune disorders suggesting a critical role of WASp in immune tolerance¹. Specifically, dendritic cells (DC), which begin the immune cascade by presenting potentially harmful antigens to T cells, are functionally impaired in WAS patients^2,3. Current treatment is often symptomatic and not curative; thus, a gene therapy approach is crucial to restore immune cell activation and function^1,4,5,7. Studies have found the use of lentiviral vectors (LV), a major tool for gene delivery in mammalian cells, can stably integrate corrections to WASp in all hematopoietic lineages with no evidence of insertional mutagenesis¹. Additionally, LV in a murine model has been shown to improve DC antigen phagocytosis and presentation^2,3. Currently, LV therapy has been shown to be clinically safe in in vivo studies and is currently used to treat other primary immunodeficiencies with high specificity and efficacy^6,7. Methods. Using a murine model transduced with LV, in vivo and in vitro DC function were tested by comparing antigen uptake, DC migration and antigen presentation in LV-treated and control WASp^– cells^2,3. Developing a self-inactivating (SIN) LV with an internal promotor for WASp is crucial to preventing insertional mutagenesis⁷. To test the preclinical safety, transduced CD34+ cells were transplanted into immunodeficient mice and distribution within hematopoietic tissues were compared⁶. Results/Conclusions. WASp^– DCs with LV transduction showed more efficient antigen uptake and presentation when compared to untreated WASp^– DCs^2,3. Additionally, treated DCs migrate with more specificity and efficacy to draining lymph nodes; thus, these cells can both reach T cell areas and stably interact with T cells². This demonstrates that WASp^– DCs can be improved to near-baseline functionality with LV treatment³. A SIN lentiviral vector had the highest efficacy in murine and non-human primate models, resulting in superior immune cell reconstitution with higher level WASp expression to stably restore immune cell deficiencies while minimizing potential mutagenesis⁷. This vector positively improves lymphocyte function and WASp expression in platelets and thus would be a prime treatment candidate for WAS patients⁷. LV transduction is efficient at gene modification for specifically altered sites without evidence of toxicity, indicating vectors are evenly biodistributed⁶. While LV transduction is an effective treatment for WAS, potential new targeted therapies including the CRISPR-CAS9 model, could be used for gene modification with higher specificity and efficacy⁴.

1. Aiuti, Alessandro, Luca Biasco, Samantha Scaramuzza, Francesca Ferrua, Maria Pia Cicalese, Cristina Baricordi, Francesca Dionisio, et al. “Lentiviral Hematopoietic Stem Cell Gene Therapy in Patients with Wiskott-Aldrich Syndrome.” Science (New York, N.Y.) 341, no. 6148 (August 23, 2013): 1233151. doi:10.1126/science.1233151.
2. Catucci, M., Prete, F., Bosticardo, M., Castiello, M.C., Draghici, E., Locci, M., Roncarolo, M.G., Aiuti, A., Benvenuti, F., and Villa, A. (2012). Dendritic cell functional improvement in a preclinical model of lentiviral-mediated gene therapy for Wiskott–Aldrich syndrome. Gene Ther 19, 1150–1158.
3. Catucci, Marco, Ivan Zanoni, Elena Draghici, Marita Bosticardo, Maria C. Castiello, Massimo Venturini, Daniela Cesana, et al. “Wiskott-Aldrich Syndrome Protein Deficiency in Natural Killer and Dendritic Cells Affects Antitumor Immunity.” European Journal of Immunology 44, no. 4 (April 2014): 1039–45. doi:10.1002/eji.201343935.
4. Kohn, Donald B., and Caroline Y. Kuo. “New Frontiers in the Therapy of Primary Immunodeficiency: From Gene Addition to Gene Editing.” The Journal of Allergy and Clinical Immunology 139, no. 3 (March 2017): 726–32. doi:10.1016/j.jaci.2017.01.007.
5. Sauer, Aisha V., Biagio Di Lorenzo, Nicola Carriglio, and Alessandro Aiuti. “Progress in Gene Therapy for Primary Immunodeficiencies Using Lentiviral Vectors.” Current Opinion in Allergy and Clinical Immunology 14, no. 6 (December 2014): 527–34. doi:10.1097/ACI.0000000000000114.
6. Scaramuzza, S., Biasco, L., Ripamonti, A., Castiello, M.C., Loperfido, M., Draghici, E., Hernandez, R.J., Benedicenti, F., Radrizzani, M., Salomoni, M., et al. (2013). Preclinical Safety and Efficacy of Human CD34+ Cells Transduced With Lentiviral Vector for the Treatment of Wiskott-Aldrich Syndrome. Molecular Therapy 21, 175–184.
7. Singh, S., Khan, I., Khim, S., Seymour, B., Sommer, K., Wielgosz, M., Norgaard, Z., Kiem, H.-P., Adair, J., Liggitt, D., et al. (2017). Safe and Effective Gene Therapy for Murine Wiskott-Aldrich Syndrome Using an Insulated Lentiviral Vector. Molecular Therapy – Methods & Clinical Development 4, 1–16.