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.

No abstract

Members of the extended Fc receptor-like (FCRL) family in humans and mice are preferentially expressed by B cells and possess tyrosine-based immunoregulatory function. Although the majority of these proteins repress B cell receptor-mediated activation, there is emerging evidence for their bifunctionality and capacity to counter-regulate adaptive and innate signaling pathways. In light of these findings, the recent discovery of ligands for several of these molecules has begun to reveal exciting potential for them in normal lymphocyte biology and is launching a new phase of FCRL investigation. Importantly, these fundamental developments are also setting the stage for defining their altered roles in the pathogenesis of a growing number of immune-mediated diseases. Here we review recent advances in the FCRL field and highlight the significance of these intriguing receptors in normal and perturbed immunobiology.

Receptors for the Fc portion (FCR) of Ig have been extensively characterized and are known to regulate humoral responses, but members of the closely related FCR-like (FCRL) family have not been found to bind Ig and to date no ligand has been identified for any FCRL. Using a cell-based GFP reporter system and a recombinant Fc chimeric protein, we show that human FCRL6, a receptor selectively expressed by cytotoxic T and NK cells, directly binds HLA-DR, a major histocompatibility complex (MHC) class II molecule. Given the similarity among constant regions of Ig and MHC molecules, these findings suggest that representatives of the FCR and FCRL multigene families may have independently evolved to engage two ancestral elements fundamental to adaptive immunity. This discovery may offer new insight into the interaction between cytotoxic lymphocytes and antigen presenting cells and may have important implications for better understanding HLA disease susceptibility and pathogenesis.

B-1a cells produce "natural" antibodies (Abs) to neutralize pathogens and clear neo self-antigens, but the fundamental selection mechanisms that shape their polyreactive repertoires are poorly understood. Here, we identified a B cell progenitor subset defined by Fc receptor-like 6 (FCRL6) expression, harboring innate-like defense, migration, and differentiation properties conducive for natural Ab generation. Compared to FCRL6 − pro B cells, the repressed mitotic, DNA damage repair, and signaling activity of FCRL6 + progenitors, yielded V H repertoires with biased distal Ighv segment accessibility, constrained diversity, and hydrophobic and charged CDR-H3 sequences. Beyond nascent autoreactivity, V H 11 productivity, which predominates phosphatidylcholine-specific B-1a B cell receptors (BCRs), was higher for FCRL6 + cells as was pre-BCR formation, which was required for Myc induction and V H 11, but not V H 12, B-1a development. Thus, FCRL6 revealed unexpected heterogeneity in the developmental origins, regulation, and selection of natural Abs at the pre-BCR checkpoint with implications for autoimmunity and lymphoproliferative disorders.