Esser-Kahn Group



Study of Innate Immune Activation

Our lab is tackling fundamental questions about immunology and immune activation that will help guide efforts in vaccine development and drug delivery design. Some of these questions include: How many ligands are required to bind receptors to activate a cell’s immune repertoire? To what extent does receptor clustering inform an immune cell’s activated phenotype? How does stimulating a single immune cell affect a surrounding bulk population of cells? Using state-of-the-art technologies such as ImageStream, lattice light sheet microscopy, and FluidFM, we assay receptor-ligand interactions and cellular activation to elucidate mechanistic details regarding the immune response to stimulation. Through our studies, we hope to uncover critical features of the immune response that vaccine adjuvants and other synthetic stimulants can take advantage of to mimic, optimize, and/or reprogram immune responses.

Counting Immune Agonists

How many molecules of an immunostimulatory agonist are required to activate an immune cell? Despite over a century of research into vaccines, this basic parameter has not been measured for any of the innate immune pathways. Using a combination of chemistry and existing instrumentation, we have recently developed a methodology to enable a first-of-its-kind quantification of the activation threshold for one of these innate pathways--Toll-Like Receptor 2/6 (TLR2/6). Using this new tool, we seek to answer fundamental biological questions and expand the methodology to other important pathways in immunology.

Single Cell vs Bulk Cell Stimulation

We are also studying the fundamentals of the innate immune response using Fluidic Force Microscopy (FluidFM). FluidFM technology allows for local chemical or mechanical stimulation of target cells with minimal disturbance of their environment and simultaneous monitoring with live-cell microscopy. Currently, we are studying the sensitivity of macrophages to TLR agonists in the context of their environment and neighboring cell behavior. Since TLR agonists activate macrophages and are also used as vaccine adjuvants, we want to better understand macrophage sensitivity to TLR agonists, the role of environmental factors on that sensitivity, and whether the response is individual or collective. Traditional experiments either isolate the cells or stimulate them collectively, but with the FluidFM, we can provide a localized stimulus to an otherwise undisturbed culture. This gives us to better control over the cell environment the temporal and spatial extent of the stimulus, allowing us to investigate questions that would otherwise be experimentally difficult. A better understanding of macrophage responses to TLR stimulation informs our understanding of how innate immune cells respond to the adjuvants in vaccines, and therefore how we can better design vaccines to elicit the desired immune response. 

Live Receptor Imaging

We are pioneering the study of live TLR dynamics via lattice light sheet microscopy.  Through this high speed imaging technique, we are able to directly quantify TLR dynamics in response to agonist stimulation.  These studies will help uncover key insights into the physical behavior of these receptors upon activation--including how different stimulant classes, molecular assemblies, and geometries inform different receptor responses.  We hope to use these findings to design vaccine adjuvants that promote strong protective responses by interacting optimally with innate immune receptor systems.  


Applied Study in Adjuvant Design

Nanoparticle Vaccines

Vaccines are one of the most effective methods for preventing diseases. In many vaccine formulations, adjuvants are needed to help activate the immune system against a specific antigen, though the inflammatory effect of adjuvants renders many of them unsafe for clinical use. To this end, many research studies have gone towards exploring various adjuvants or adjuvant-free nanoparticle systems to develop platforms with increased safety profiles. However, efforts to design non-inflammatory vaccines efficiently are hindered by the lack of insight into their mechanism of immune system activation and suppression of inflammation; in fact, many systems are still tested empirically. The goal of this project is to elucidate the mechanisms of non-inflammatory immunogenic vaccines. Using an in-vivo lung model, we are currently exploring an adjuvant-free nanofiber system that has been shown to activate dendritic cells in the lung and elicit Th17 cells responses with minimal inflammation. More specifically, this project aims to identify the signature profiles of dendritic cells after intranasal immunization at the single cell level, while tracking the migration of innate immune cells during the initial inflammatory response. Knowing which pathways are activated or suppressed in this system will help researchers rationally design new vaccines that can achieve similar low levels of inflammation.


Novel Adjuvant Discovery

Our mechanistic studies have led to our development of synthetic, linked Toll-Like Receptor (TLR) agonists as vaccine adjuvant candidates. These species, which consist of two or more TLR agonists covalently tethered together, have shown potential to stimulate unique, desirable immune responses as compared to the individual agonists in vitro and in animal models. Contact allergens are small molecules that also stimulate the immune system in a manner similar to TLR agonists. We are exploring the mechanism of action of contact allergens in an attempt to use them as potential vaccine adjuvants.


Immune Reprogramming

Biasing the immune signaling pathway towards adaptive responses and away from inflammatory responses can provide a means of successfully utilizing a large number of adjuvants in formulating vaccines. We have shown that by using an NFkB inhibitor called SN50, inflammatory responses could be decreased while increasing protection against a lethal influenza challenge in vivo. We are also developing inflammasome activators as vaccine adjuvants and in immune therapy to generate robust antigen specific CD4+ and CD8+ responses. We are also exploring the field of trained immunity to train innate immune cells to respond stronger and better to an immune evasion.