Most viruses exploit a variety of host cellular proteins as primary cellular attachment receptors in the context of successful execution of infection. Furthermore, many viral agents have evolved precise mechanisms to subvert host immune recognition to achieve persistence. Herein we present data indicating that adenovirus (Ad) serotype 3 utilizes CD80 (B7.1) and CD86 (B7.2) as cellular attachment receptors. CD80 and CD86 are co-stimulatory molecules that are present on mature dendritic cells and B lymphocytes and are involved in stimulating T-lymphocyte activation. To our knowledge, this is one of the first demonstrations of a virus utilizing immunologic accessory molecules as a primary means of cellular entry. This finding suggests a mechanism whereby viral exploitation of these proteins as receptors may achieve both goals of cellular entry and evading the immune system.

Adenovirus (Ad)-mediated transduction of dendritic cells (DC) is inefficient because of the lack of the primary Ad receptor, CAR. DC infection with Ad targeted to the CD40 results in increased gene transfer. The current report describes further development of the CD40-targeting approach using an adapter molecule that bridges the fiber of the Ad5 to CD40 on mouse DC. The adapter molecule, CFm40L, consists of CAR fused to mouse CD40 ligand via a trimerization motif. A stable cell line that secretes CFm40L at high levels was generated. Gene transfer to mouse bone marrow-derived DC (mBMDC) using CFm40L-targeted Ad was over 4 orders of magnitude more efficient than that for the untargeted Ad5. Gene transfer was achieved to over 70% of the mBMDC compared to undetectable transduction using untargeted Ad5. In addition to dramatically enhanced gene transfer, the CFm40L-targeted Ad5 induced phenotypical maturation and upregulated IL-12 expression. Most importantly, the CFm40L-targeted Ad5 elicited specific immune response against a model antigen in vivo. The results of this study demonstrate that Ad-mediated gene transfer to DC can be significantly enhanced using nonnative transduction pathways, such the CD40 pathway, which may have important applications in genetic vaccination for cancer and infectious diseases.

Alternate serotypes of adenovirus (Ad), including Ads of species B, are being explored to circumvent the disadvantages of Ad serotype 5 gene delivery vectors. Whereas the majority of human Ads utilize the Coxsackievirus and adenovirus receptor (CAR), none of the Ad species B use CAR. Ad species B is further divided into two subspecies, B1 and B2, and utilizes at least two classes of receptors: common Ad species B receptors and B2 specific receptors. CD46 has been implicated as a B2-specific receptor. Ad serotype 3 (Ad3), a member of B1, utilizes CD80 and CD86 as cellular attachment receptors. The receptor-interacting Ad fiber-knob domain is highly homologous among species B Ads. We hypothesized that other members of Ad species B may utilize CD80 and CD86 as cellular attachment receptors. All tested species B members showed specific binding to cells expressing CD80 and CD86, and the Ad fiber-knob domain from both B1 and B2 Ad efficiently blocked CD80-and CD86-mediated infection of Ad3 vectors. Members of both B1 and B2 demonstrated CD80-and CD86-specific infection of CHO cells expressing CD80 and CD86. Therefore, all of the members of Ad species B utilize CD80 and CD86 for infection of cells.

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The capacity of dendritic cells (DCs) to migrate from peripheral organs to lymph nodes (LNs) is important in the initiation of a T cell-mediated immune response. The ATP-binding cassette (ABC) transporters P-glycoprotein (P-gp; ABCB1) and the multidrug resistance protein 1 (MRP1; ABCC1) have been shown to play a role in both human and murine DC migration. Here we show that a more recently discovered family member, MRP4 (ABCC4), is expressed on both epidermal and dermal human skin DCs and contributes to the migratory capacity of DCs. Pharmacological inhibition of MRP4 activity or downregulation through RNAi in DCs resulted in reduced migration of DCs from human skin explants and of in vitro generated Langerhans cells. The responsible MRP4 substrate remains to be identified as exogenous addition of MRP4's known substrates prostaglandin E 2 , leukotriene B 4 and D 4 , or cyclic nucleotides (all previously implicated in DC migration) could not restore migration. This notwithstanding, our data show that MRP4 is an important protein, significantly contributing to human DC migration toward the draining lymph nodes, and therefore relevant for the initiation of an immune response and a possible target for immunotherapy. IntroductionThe ATP-binding cassette (ABC) transporters were initially identified by their roles in clinical multidrug resistance (MDR) against a broad range of functionally and structurally unrelated anticancer agents. 1 Over the past 10 years, it has become apparent that several of the ABC transporters transport not only cytostatic agents but also inflammatory mediators such as platelet activating factor, 2 leukotrienes, 3 or prostaglandins. 4 Unraveling the specific roles of ABC transporters in the functioning of the immune system may therefore reveal new links for future immunotherapeutic approaches.Dendritic cells (DCs) are key initiators of the immune response, sampling their surroundings for foreign antigens. 5 They are also seen as a promising tool for targeted immunotherapeutic strategies. 6 We have shown that dendritic cell differentiation is impaired when the transporter activity of Multidrug Resistance Protein 1 (MRP1; ABCC1) is inhibited. 7 Randolph and coworkers previously reported that both P-glycoprotein (P-gp; ABCB1) and MRP1 are required for optimal DC migration. 8,9 The ABC transporter MRP4 (ABCC4) [10][11][12] is an organic anion transporter and has been described to transport prostaglandins such as PGA 2 , PGE 1 , and PGE 2 . 4 Because PGE 2 is believed to be crucial for DC migration, [13][14][15] we explored the role of this ABC transporter in DC migration. Moreover, a recent study showed that MRP4, like MRP1, can transport leukotrienes (eg, LTB 4 and LTC 4 ). 16 Thus, when expressed on DCs, MRP4 could have contributed to the original observations made for the role of MRP1 in DC migration, 9 because the used antagonist MK-571 can inhibit both transporters. In this manuscript we show that MRP4 is abundantly expressed in epidermal human skin DCs and at lower levels in dermal human ski...