Stephen A. Ehrenzeller

The cytosolic RNA sensor RIG-I is a critical component of the innate immune response to RNA viruses, yet few tools exist to track RIG-I in vivo . Herein, we report the development of a RIG-I reporter mouse, termed RIG-I ^mScar , that enables fluorescence imaging and tractable immunoprecipitation of RIG-I in vivo . These mice revealed enrichment of RIG-I expression in circulatory, lymphoid, and mucosal tissues and broad expression across immune cell types. RIG-I itself is upregulated in response to IFN. To distinguish RIG-I sentinel cells, which are programmed to express RIG-I at steady state, from IFN-responder cells, we crossed RIG-I ^mScar mice with Mx1 ^GFP mice. Blocking IFNAR with a monoclonal antibody showed that basal RIG-I expression in immune cells was largely independent of type I IFN signaling, although Ly6C ^hi monocytes required IFNAR for RIG-I expression. To probe functional responses in vivo , we intranasally administered a RIG-I-specific agonist, SLR14. Mapping RIG-I expression across the lung identified alveolar macrophages as a critical RIG-I sensor cell population, and depletion of alveolar macrophages, but not neutrophils, slightly impaired lung IFN responses. Together, these findings support the use of the RIG-I ^mScar model to probe RIG-I dynamics in vivo and predict functional sensor cell populations across tissues.

Almost 1 million people in the United States suffer from multiple sclerosis (MS). Current therapies suppress protective immunity and are non-curative. Antigen-specific therapies can selectively suppress autoreactive cells, preserving protective immunity. B cell dysregulation, a major driver of MS, remains largely untargeted for antigen-specific tolerance. We hypothesize that targeting B cells with antigen-loaded microparticles will enhance therapeutic efficacy. Here, we demonstrate that antigen-loaded acetalated dextran microparticles (AMP) surface-associate with B cells and enhance IL-10 secretion and MHCII expression, promoting tolerogenic antigen presentation. Leveraging this property, we developed a therapy using myelin oligodendrocyte (MOG_35-55) peptide-loaded AMPs associated with B cells (MOG-AMP-B). Administering MOG-AMP-Bs in a late therapeutic model of multiple sclerosis resulted in unprecedented recovery, reducing central nervous system (CNS) inflammation, downregulating activated dendritic cells and macrophages, and increasing regulatory T- and B cells. MOG-AMP-Bs did not reduce the ability of animals to respond to a viral infection, representing a highly effective antigen-specific therapy for restoring immune balance in autoimmunity.

Genital herpes, caused by herpes simplex virus 2 (HSV-2), remains a prevalent sexually transmitted infection with no available vaccine. Effective local immunity, mediated in part by tissue-resident memory T cells (T _RM cells) and luminal antibodies, provides immediate viral control. Here, we developed bioactive enhanced adjuvant chemokine oligonucleotide nanoparticles (BEACONs) formed via electrostatic interactions between CpG oligodeoxynucleotides (CpG ODNs) and the chemokine CXCL9. This adjuvant enhances antigen-presenting cell engagement and innate immune signaling, promotes CD8 T cell recruitment, and reduces local neutrophilic inflammation relative to CpG ODNs. After intramuscular priming with HSV-2 glycoprotein-encoding messenger RNA–lipid nanoparticles, vaginal boosting with cognate recombinant glycoprotein and BEACONs improved protection against HSV-2 by increasing local CD8 T _RM cell populations and mucosal antibody responses. Vaccine-mediated protection required local delivery of both antigen and adjuvant and was reduced by CD8 T cell or B cell depletion. These findings support engineered mucosal adjuvants for vaccines targeting genital herpes and other sexually transmitted infections.

Mucosal surfaces are primary entry sites for many infectious pathogens, yet parenteral vaccination alone often fails to elicit effective mucosal immunity. Mucosally delivered vaccines offer a promising strategy for reinforcing frontline defences and inducing localized, pathogen-specific immune responses. Recent studies indicate that mucosal vaccines elicit tissue-resident memory T and B cells, along with robust local antibody secretion, to prevent infection and transmission. However, achieving sterilizing immunity at mucosal sites proves challenging owing to the complex immune environments consisting of epithelial barriers, varying mucus composition, pH differences and hormonal influences. In this Review, we outline how specialized immune-inductive and effector mechanisms across distinct mucosal compartments contribute to protective immunity and discuss emerging strategies to harness multilayered mucosal immunity to develop safe, effective vaccines that elicit durable protection.

Multiple sclerosis (MS) is a severe autoimmune disorder that wreaks havoc on the central nervous system, leading to a spectrum of motor and cognitive impairments. There is no cure, and current treatment strategies rely on broad immunosuppression, leaving patients vulnerable to infections. To address this problem, our approach aims to induce antigen-specific tolerance, a much-needed shift in MS therapy. We have engineered a tolerogenic therapy consisting of spray-dried particles made of a degradable biopolymer, acetalated dextran, and loaded with an antigenic peptide and tolerizing drug, rapamycin (Rapa). After initial characterization and optimization, particles were tested in a myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis model of MS. Representing the earliest possible time of diagnosis, mice were treated at symptom onset in an early therapeutic model, where particles containing MOG and particles containing Rapa+MOG evoked significant reductions in clinical score. Particles were then applied to a highly clinically relevant late therapeutic model during peak disease, where MOG particles and Rapa+MOG particles each elicited a dramatic therapeutic effect, reversing hind limb paralysis and restoring fully functional limbs. To confirm the antigen specificity of our therapy, we immunized mice against the influenza antigen hemagglutinin (HA) and treated them with MOG particles or Rapa+MOG particles. The particles did not suppress antibody responses against HA. Our findings underscore the potential of this particle-based therapy to reverse autoimmunity in disease-relevant models without compromising immune competence, setting it apart from existing treatments.