Abstract
4242
Dendritic cells (DC) play a central role in presenting antigens and activating immune responses. Adenoviral (AdV) vectors have been used as a method for targeting DC to stimulate transgene-sepcific vaccine responses. However, DC lack high affinity CAR receptors and integrin receptors [ανβ3 and ανβ5, binds to Arg-Gly-Asp (RGD) sequence] primarily mediate their transduction. In the present study we evaluated the expression of alpha v (αν) integrin (CD51) on mouse bone marrow derived DC (BM-DC) to determine whether expression of this integrin identifies a distinct DC subset with unique antigen presenting activity. 20-25% of CD11c+ BM-DC expressed αν integrin receptor (αν+ DC) when stained by specific antibody. These αν+ DC also expressed high level of β3 integrins, whereas αν- DC expressed low level of β3 integrins. The MHC class I, MHC class II and co-stimulatory molecules (B7.1, B7.2) were expressed equally on both the DC subsets. Transduction of BM-DC by a first generation AdV (AdV-GFP) revealed that αν+DC are preferentially transduced by AdV (Mean Fluorescent Intensity (MFI): 74) whereas αν- DC are not (MFI 19). An AdV vector that was designed to express an RGD sequence in the fiber knob (RGD-AdV-GFP) produced even better transduction of αν+ DC (MFI: 794) and partial transduction of αν- DC (MFI: 133). Transduction of BM-DC by AdV was shown to be RGD-dependent by using exogenous RGD peptide as a specific inhibitor. In order to assess these two different DC subsets for their antigen presenting activity, BM-DC were transduced with AdV expressing ova-albumin (AdV-OVA) and sorted into either αν+ DC or αν-DC by flow cytometry. DC were then cultured with OVA specific OT-I T cells in vitro and proliferation measured as an indicator of antigen-presenting efficiency. The αν+ DC subset was 2-3 fold more efficient in OVA-specific antigen presentation than αν- DC. Transduction of these DC subsets by AdV produced minor changes in MHC class I, Class II and costimulatory molecules. These DC subsets were also evaluated for their ability to stimulate allogenic T cell responses. Control αν+ DC, prior to transduction, induced lower allostimulatory activity than αv- DC. When BM-DC were transduced with AdV, the αν+DC remained weak stimulators whereas the allostimulatory activity of αν- DC increased by 3 fold. This study indicates that BM-derived DC can be classified into two subsets on the basis of their αν integrin expression (αν+ DC and αν- DC); which differ markedly in their transduction by AdV, presentation of transgene antigen, and allostimulatory capacity.
- American Association for Cancer Research