Maturation of dendritic cells infected by recombinant adenovirus can be delayed without impact on transgene expression

Adenovirus-mediated gene transfer to dendritic cells is highly efficient an d often used, but the relationship among cell maturation, viral infection a nd expression of a transferred gene remains unclear. To study this relation ship, we introduced a recombinant replication-defective adenovirus encoding the gene for green fluorescent protein to normal human immature myeloid de ndritic cells. We induced maturation by the addition of TNF-alpha, IL-1 bet a, IL-6 and prostaglandin E-2 to the medium and assessed cell maturity by t he levels of the secreted p40 subunit of IL-12 and of membrane-bound CD83. We quantified the efficiency of gene expression by GFP fluorescence and ana lyzed the data by a mixed-model analysis of variance; the model explained m ore than 97% of the effects. CD83 expression and p40 secretion depended sol ely on incubation time and maturation medium. The cells cultured in the abs ence of maturation medium remained immature and maintained the ability to r espond to the later addition of the maturation irrespective of adenovirus i nfection and transferred gene expression. This expression was independent o f cell maturation. In comparison with mature cells, the transferred gene wa s expressed in immature dendritic cells with a lag compatible with the less effective initial step (infection and/or gene transfer) in the absence of the maturation medium rather than less effective later GFP synthesis. Expre ssion of CD83 and p40 were unaffected by adenovirus infection and transferr ed gene expression. Thus, immature dendritic cells infected with recombinan t adenoviruses can be matured when desired after transferred gene expressio n.