Targeting antigen to lymph node lymphatic endothelial cells under steady-state to promote archiving and memory

Abstract

Lymphatic endothelial cells (LECs) have been shown to archive antigen (Ag), i.e. retain Ag in its native form, for weeks after exposure. We have developed a polymeric platform that promotes targeting of Ag to lymph node (LN)-resident LECs by exploiting the sugar-binding scavenger receptors expressed by LECs, leading to longer Ag retention over 2 weeks. This targeting results in enhanced Ag archiving in LECs, even in the absence of an adjuvant or other inflammatory stimuli previously shown to be necessary for Ag archiving in LECs. 2 weeks after subcutaneous (s.c.) delivery of unmodified OVA, we observed substantial proliferation and activation of adoptively transferred OVA-specific CD8+ T cells. Immunization and subsequent Ag archiving with our targeting polymer conjugated to OVA (without adjuvant) led to reduced CD8+ T cell proliferation but higher differentiation into a central memory phenotype, both by surface receptors as well as the ratio of EOMES vs. T-bet on activated T cells. We measured MHCI-mediated presentation of OVA (SIINFEKL presented on the H-2kb molecule) on LN-LECs vs. DCs over two weeks following s.c. injection and found that Ag presentation by LECs was comparable to DCs. This demonstrates that LECs are able to cross-present archived Ag directly to CD8+ T cells, with potential implications in the prolonged maintenance of memory CD8+ T cells and design of a more effective vaccine platform.