In vivo kinetics of transduced cells in peripheral T cell-directed gene therapy: Role of CD8(+) cells in improved immunological function in an adenosine deaminase (ADA)-SCID patient

We previously reported successful peripheral T cell-directed gene therapy i n a boy with adenosine deaminase (ADA)-SCID. In the present study, to bette r understand the reconstitutive effect of this gene therapy on his immunolo gical system, we investigated the in vivo kinetics and functional subsets o f T cells in PBL. Apparent immunological improvements were obtained after i nfusion of transduced cells at more than 4 x 10(8) cells/kg/therapy/3 mo, F requency of ADAcDNA-integrated cells in PBL, ADA activity in PBL and clinic al improvement showed good correlation, even though CD8(+) cells gradually became predominant in PBL. On the basis that polyethylene glycol (PEG)-ADA was maintained at the same dosage as before gene therapy, we consider that his immunological improvement resulted from the gene therapy itself. Most C D3(+) cells in PBL after gene therapy expressed TCR alpha beta. Analysis of TCR repertoire based on TCR V region usage revealed no expansion of limite d clones in his PBL. The T cell subset cells CD8(+)CDw60(+) and CD8(+)CD27( +)CD45RA(-). which are reported to provide substantial help to B cells, wer e maintained throughout the gene therapy. Furthermore, his reconstituted pe ripheral T cells helped normal B cells to produce substantial IgG in vitro. Expression of both Th1- and Th2-type cytokine genes was induced in his rec onstituted T cells at the same comparably high level as in normal subjects. Collectively, these results provide evidence of persistent and distinct fu nctions of transduced cells in this patient's PBL after gene therapy.