A Remote Secondary Binding Pocket Promotes Heteromultivalent Targeting of DC-SIGN.

Robert Wawrzinek,Jessica Schulze,Dirk Hauck,Oliver Schwardt,Christoph Rademacher,Maria Bräutigam,Mareike Rentzsch,Lennart Schnirch,Felix F Fuchsberger,Gary Domeniconi,Oliver Seitz,Gunnar Bachem,Beat Ernst,Alexander Titz,Peter H Seeberger,Hengxi Zhang,Mónica Guberman,Eike‐Christian Wamhoff ,Carlos P Modenutti ,Jonathan Lefèbre ,Marcelo A Martí

doi:10.1021/jacs.1c07235

Abstract

Dendritic cells (DC) are antigen-presenting cells coordinating the interplay of the innate and the adaptive immune response. The endocytic C-type lectin receptors DC-SIGN and Langerin display expression profiles restricted to distinct DC subtypes and have emerged as prime targets for next-generation immunotherapies and anti-infectives. Using heteromultivalent liposomes copresenting mannosides bearing aromatic aglycones with natural glycan ligands, we serendipitously discovered striking cooperativity effects for DC-SIGN+ but not for Langerin+ cell lines. Mechanistic investigations combining NMR spectroscopy with molecular docking and molecular dynamics simulations led to the identification of a secondary binding pocket for the glycomimetics. This pocket, located remotely of DC-SIGN’s carbohydrate bindings site, can be leveraged by heteromultivalent avidity enhancement. We further present preliminary evidence that the aglycone allosterically activates glycan recognition and thereby contributes to DC-SIGN-specific cell targeting. Our findings have important implications for both translational and basic glycoscience, showcasing heteromultivalent targeting of DCs to improve specificity and supporting potential allosteric regulation of DC-SIGN and CLRs in general.

Highlights

Dendritic cells (DCs) constitute an integral part of the immune system, both in self- and in pathogen recognition
These characteristics render DCs attractive targets for antigen-specific immunotherapies, either to combat cancer or to develop prophylactic vaccines against viral and bacterial infections.[1−6] A hallmark of DCs is the expression of several classes of endocytic receptors, including scavenger and chemokine receptors as well as C-type lectin receptors (CLRs).[7−9] The latter are a class of pattern recognition receptors and of particular biomedical interest, as they display highly restricted expression profiles and promote antigen cross-presentation
Langerin (CD207) and DC-SIGN (CD209) represent two well-studied CLRs. The former is predominantly found on Langerhans cells, the major DC subset residing in the epidermis.[10−12] As one of the first immune receptors to encounter pathogens entering the body via the skin, Langerin has been subject to targeting attempts employing either antibodies or glycomimetics.[4,13−17] Found on both dermal DCs and macrophages, DC-SIGN shows a much broader expression profile.[18,19]

Summary

Introduction

Dendritic cells (DCs) constitute an integral part of the immune system, both in self- and in pathogen recognition. Working at the interface of innate and adaptive immunity, they can internalize viruses or bacteria and process exogenous antigens which they eventually present to CD4+ and CD8+ T cells. These characteristics render DCs attractive targets for antigen-specific immunotherapies, either to combat cancer or to develop prophylactic vaccines against viral and bacterial infections.[1−6] A hallmark of DCs is the expression of several classes of endocytic receptors, including scavenger and chemokine receptors as well as C-type lectin receptors (CLRs).[7−9] The latter are a class of pattern recognition receptors and of particular biomedical interest, as they display highly restricted expression profiles and promote antigen cross-presentation. The former is predominantly found on Langerhans cells, the major DC subset residing in the epidermis.[10−12] As one of the first immune receptors to encounter pathogens entering the body via the skin, Langerin has been subject to targeting attempts employing either antibodies or glycomimetics.[4,13−17] Found on both dermal DCs and macrophages, DC-SIGN shows a much broader expression profile.[18,19] It has been targeted, for instance, to develop cancer vaccines and antivirals, most prominently against HIV, which is known to hijack DC-SIGN to subsequently infect T cells.[18,20−22]

Objectives

Results

Conclusion