In vitro culture during retroviral transduction improves thymic repopulation and output after TBI and autologous PBPC transplantation in rhesus macaques

¹ Immunology Laboratory, Vaccine Research Center, National Institute of Allergy and Infectious Disease, National Institutes of Health/Department of Health and Human Services, Bethesda, Maryland
² Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health/Department of Health and Human Services, Bethesda, Maryland
³ Human Immunology Section, Vaccine Research Center, National Institute of Allergy and Infectious Disease, National Institutes of Health/Department of Health and Human Services, Bethesda, Maryland
⁴ Hematopathology Section, National Cancer Institute, National Institutes of Health/Department of Health and Human Services, Bethesda, Maryland
⁵ Division of Biostatistics, University of Minnesota, Minneapolis, Minnesota

^* To whom correspondence should be addressed. E-mail: dunbarc{at}nhlbi.nih.gov.

	Abstract

Immunodeficiency after peripheral blood progenitor cell (PBPC) transplantation may be influenced by graft composition, underlying disease and/or pre-treatment. These factors are difficult to study independently in humans. Ex vivo culture and genetic manipulation of PBPC grafts may also affect immune reconstitution, with relevance to gene therapy applications. We directly compared the effects of three clinically-relevant autologous graft compositions on immune reconstitution after myeloblative total body irradiation in rhesus macaques, the first time these studies have been performed in a large animal model with direct clinical relevance. Animals received CD34⁺ cell dose-matched grafts of either peripheral blood mononuclear cells, purified CD34⁺ PBPC or purified CD34⁺ PBPC expanded in vitro and retrovirally-transduced. We evaluated the reconstitution of T, B, NK, dendritic cells and monocytes in blood and lymph nodes for up to a year post-transplantation. Animals receiving selected-transduced CD34⁺ cells had the fastest recovery of T-cell numbers, along with the highest TREC levels, the fewest proliferating Ki-67⁺ T-cells in the blood, and the best-preserved thymic architecture. Selected-transduced CD34⁺ cells may therefore repopulate the thymus more efficiently and promote a higher output of naïve T-cells. These results have implications for the design of gene therapy trials as well as the use of expanded PBPC for improved T-cell immune reconstitution after transplantation.

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