Selection of an Antibody Library Identifies a Pathway to Induce Immunity by Targeting CD36 on Steady-State CD8α+ Dendritic Cells

Abstract

Improvement of the strategy to target tumor Ags to dendritic cells (DCs) for immunotherapy requires the identification of the most appropriate ligand/receptor pairing. We screened a library of Ab fragments on mouse DCs to isolate new potential Abs capable of inducing protective immune responses. The screening identified a high-affinity Ab against CD36, a multi-ligand scavenger receptor primarily expressed by the CD8α+ subset of conventional DCs. The Ab variable regions were genetically linked to the model Ag OVA and tested in Ag presentation assays in vitro and in vivo. Anti-CD36-OVA was capable of delivering exogenous Ags to the MHC class I and MHC class II processing pathways. In vivo, immunization with anti-CD36-OVA induced robust activation of naive CD4+ and CD8+ Ag-specific T lymphocytes and the differentiation of primed CD8+ T cells into long-term effector CTLs. Vaccination with anti-CD36-OVA elicited humoral and cell-mediated protection from the growth of an Ag-specific tumor. Notably, the relative efficacy of targeting CD11c/CD8α+ via CD36 or DEC205 was qualitatively different. Anti-DEC205-OVA was more efficient than anti-CD36-OVA in inducing early events of naive CD8+ T cell activation. In contrast, long-term persistence of effector CTLs was stronger following immunization with anti-CD36-OVA and did not require the addition of exogenous maturation stimuli. The results identify CD36 as a novel potential target for immunotherapy and indicate that the outcome of the immune responses vary by targeting different receptors on CD8α+ DCs.

Targeted Antigen Delivery to DEC-205+Dendritic Cells for Tolerogenic Vaccination

“…Notably, and in striking contrast to anti-DEC-205 DC targeting [37], anti-CD36 mAb-mediated DC targeting in vivo elicits profound Ag-specific CD4 + and CD8 + T cell responses, regardless of whether DCs had been deliberately activated by coadministration of anti-CD40 mAbs [92]. Interestingly, some surface molecules (CD40, MHC-II, TLR2, and FcγRII/III) failed to mediate appreciable MHC presentation of targeted Ag and activation of Ag-specific T cells in vivo [90].…”

Expression of Wiskott-Aldrich Syndrome Protein in Dendritic Cells Regulates Synapse Formation and Activation of Naive CD8+ T Cells

“…Mice were injected with a recombinant anti-DEC205 Ab fused to OVA (␣DEC205-OVA) in the presence of anti-CD40 Ab (␣CD40). Immunization with ␣DEC205-OVA leads to cross-presentation of the MHC class I epitope of OVA mainly by CD8 ϩ LN-resident DCs and the adjuvant ␣CD40 is required to expand long term memory CD8 ϩ T cells (7,23,25). A control irrelevant Ab coupled to OVA does not induce T cell activation (23).…”

“…Immunization with ␣DEC205-OVA leads to cross-presentation of the MHC class I epitope of OVA mainly by CD8 ϩ LN-resident DCs and the adjuvant ␣CD40 is required to expand long term memory CD8 ϩ T cells (7,23,25). A control irrelevant Ab coupled to OVA does not induce T cell activation (23). To exclude interference by defective activation of T cells, we analyzed responses of OVA-specific TCR transgenic T cells (OT-I) that are of WT origin.…”

“…To target DCs in vivo, we generated a recombinant anti-DEC OVA fusion as described in Ref. 23. The peptides corresponding to residues of 257-264 of OVA were synthesized on solid phase (Fmoc/t-Bu chemistry).…”

Targeted Delivery of Tumor Antigens to Activated Dendritic Cells via CD11c Molecules Induces Potent Antitumor Immunity in Mice

“…Briefly, splenocytes harvested from vaccinated mice were restimulated in the presence or absence of HER2 63-71 peptide (TYLPTNASL; 10 Ag/mL) for 6 h. During the final 4 h of incubation, 10 Ag/mL brefeldin A (Sigma) were added. After surface staining with anti-CD8, cells were permeabilized and stained for intracellular IFN-g as described previously (16). Cr-release assays were done as described previously (37).…”