Interaction of systemically delivered adenovirus vectors with Kupffer cells in mouse liver.

When adenovirus (Ad) vectors are injected intravenously they are rapidly taken up by Kupffer cells (KCs) in the liver. This results in massive KC necrosis within minutes, followed by a more gradual disappearance of KCs from the liver. It is not known how KCs recognize Ad, or why Ad kills KCs. We used a variety of mutated and fiber-pseudotyped Ad vectors to evaluate how capsid proteins influence Ad uptake by KCs and to define the viral proteins that are involved in the destruction of KCs. We found that depletion of KCs from the liver was partially dependent on interactions between Ad and integrins, but was independent of the coxsackievirus and Ad receptor. The Ad5 fiber shaft was proven to be a particularly important contributory factor, because vectors with the shorter Ad35 shaft were not as effective at depleting KCs. In contrast, the fiber head played no discernible role. Variations in the ability of Ad vectors to deplete KCs could not be explained by differences in the amount of Ad that reached KCs, because all mutant Ads were accumulated by KCs at similar levels. Interestingly, we found that the Ad mutant ts1 did not cause KC death; this virus is known to bind and enter cells normally, but the capsid is unable to disassemble or lyse membranes. We conclude that Ad vectors kill KCs at a postbinding step and that this cell death can be mitigated if downstream events in viral entry are blocked.