CD40-targeted adenoviral GM-CSF gene transfer enhances and prolongs the maturation of human CML-derived dendritic cells upon cytokine deprivation

Abstract

Vaccination with autologous leukaemia-derived dendritic cells (DC) presents an adjuvant treatment option for chronic myeloid leukaemia (CML). Here, we show that high-efficiency CD40-targeted adenoviral gene transfer of GM-CSF to CML-derived DC induces long-lived maturation in the absence of exogenous cytokines and may thus ensure protracted stimulation of CML-specific T cells upon vaccination. It has become clear from clinical observations that chronic myeloid leukaemia (CML) is amenable to T-cell-mediated immune surveillance (Kolb et al, 1995). An immunotherapeutic approach may therefore provide a valuable adjuvant treatment option, especially in minimal residual disease settings.Leukaemic dendritic cells (DC), capable of eliciting T-cell responses against CML targets (Choudhury et al, 1997;Eibl et al, 1997), are easily generated, carry all possible tumour antigens, and can be used for autologous vaccination (Ossenkoppele et al, 2003). Although it is still unclear how long DC should maintain their mature phenotype and survive in vivo in order to generate an effective antitumour T-cell response, it is generally accepted that a stable mature DC phenotype is required to prevent reversion to a possibly tolerogenic immature precursor state subsequent to adoptive transfer. In this light, introduction of the gene encoding granulocyte/macrophage-colony stimulating factor (GM-CSF) into CML-DC may be an attractive approach to both enhance and prolong antigen presentation and thus promote antileukaemic responses (Thomas et al, 1998). Recombinant adenoviruses (Ad) are attractive tools for gene transfer to DC, since they have been reported to enhance the immunostimulatory capacity of DC (Morelli et al, 2000). In addition, we previously reported that retargeting Ad to CD40 on monocyte-derived DC (MoDC) through a bispecific immunoconjugate could further increase DC maturation and simultaneously enhance gene transfer (Tillman et al, 1999). Here, we report on the utility of CD40-retargeted Ad to transduce CML-DC very efficiently, thereby reducing the viral dose needed for the desired level of transgene expression and simultaneously inducing phenotypic maturation as well as enhanced functional activity of the CML-DC. Moreover, we show that the introduction of GM-CSF into CML-DC by means of CD40-targeted Ad can significantly prolong the stability of the mature CML-DC phenotype. MATERIALS AND METHODSAfter informed consent, heparinised blood samples were collected from patients with chronic-phase CML at diagnosis or during treatment with hydroxyurea and/or IFN-a. PBMC were isolated and CML-DC generated, phenotypically characterised, and tested for leukaemic origin by bcr-abl FISH, as previously described (Ossenkoppele et al, 2003).Replication-deficient recombinant Ad-5 vectors and bispecific Ad-targeting antibody conjugates were constructed, produced, purified, and used for CML-DC infection as previously reported (Tillman et al, 1999). The expression of green fluorescent protein (GFP) and DC differentiation and maturation markers w...

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