Modification of a fiber protein in an adenovirus vector improves in vitro gene transfer efficiency to the mouse microglial cell line

In microglia, it is difficult to introduce exogenous genes of interest even by recombinant adenovirus vectors (Ad) which can infect with high efficiency only to the cells expressing coxackievirus and adenovirus receptors (CAR). We found a lack of CAR expression in primary cultured murine microglia (PCMG) and its immortalized cell line MG5 by reverse transcription-polymerase chain reaction. In order to improve the efficiency of gene transfer, we generated a novel Ad (Ad-RGD) by an incorporation of the Arg-Gly-Asp motif (RGD) containing peptide in the HI loop of the viral fiber knob domain, which enables the virus to contact target cells through αV integrins which are known to be ubiquitously expressed on the surface of mammalian cells. Ad-RGD showed a remarkable improvement (13-18-fold) in the delivery of Escherichia coli LacZ gene in MG5 cells and a moderate increase in PCMG cells under the treatment with granulocyte-macrophage colony stimulating factor. These results suggest that Ad-RGD may be a potent tool for the delivery of genes to microglia activated by optimum stimulation, and thus analyzing the function of microglia with utilization of MG5 and PCMG cells.