A research team at the Nano Life Science Institute (WPI-NanoLSI) and the Faculty of Medicine at Kanazawa University has developed a new class of engineered extracellular vesicles (EVs) capable of inducing antigen-specific regulatory T cells (Tregs), the immune cells that play a central role in suppressing excessive immune responses. The findings, now published in Drug Delivery, may pave the way for next-generation therapies for autoimmune and allergic diseases, where unwanted immune activation must be precisely controlled.

Autoimmune diseases arise when the immune system mistakenly attacks the body’s own tissues. Current treatments largely rely on broad immunosuppression using steroids or immunosuppressants, which reduce symptoms but also weaken protective immunity, leaving patients vulnerable to severe infections and other complications. A long-standing goal in immunology has been the development of therapies that suppress immune responses only toward disease-related antigens, a concept known as “antigen-specific immune tolerance.”

Regulatory T cells (Tregs) represent the body’s natural mechanism for maintaining immune tolerance, but inducing antigen-specific Tregs safely and efficiently in vivo has proven extremely difficult. To address this challenge, Shota Imai, Tomoyoshi Yamano and Rikinari Hanayama, and colleagues engineered “antigen-presenting extracellular vesicles” (AP-EVs-Treg) that display, on a single vesicle surface, peptide–MHC class II complexes (pMHCII) for antigen-specific T-cell recognition together with the two cytokines interleukin-2 (IL-2) and transforming growth factor-β (TGF-β), both of which are essential for Treg differentiation.

Strong induction of functional, antigen-specific Tregs in vitro

When AP-EVs were co-cultured with naïve CD4⁺ T cells from antigen-specific TCR-transgenic mice, they efficiently induced the differentiation and expansion of Foxp3⁺ Tregs. These induced Tregs expressed high levels of suppressive molecules such as CTLA-4, PD-L1, and LAG-3, and potently inhibited the proliferation of other T cells in a dose-dependent manner, demonstrating robust suppressive function.

Importantly, AP-EVs could be adapted to load different disease-related antigens, including MOG peptides associated with multiple sclerosis, enabling the induction of antigen-specific Tregs relevant to autoimmune pathology.

In vivo Treg induction enhanced by mTOR inhibition

In animal models, AP-EVs selectively activated antigen-specific CD4⁺ T cells based on their pMHCII specificity. However, Foxp3 induction required the co-administration of rapamycin, an mTOR inhibitor known to promote Treg differentiation. The combination of AP-EVs and rapamycin markedly increased the generation of antigen-specific Tregs in vivo, highlighting a synergistic mechanism and revealing a promising strategy for restoring immune tolerance in physiological environments.

A modular and clinically adaptable immune-tolerance platform

Unlike mRNA or nanoparticle-based tolerogenic systems, EVs are naturally derived, highly biocompatible, and capable of presenting multiple functional molecules simultaneously with low immunogenicity. The modularity of AP-EV design allows tuning of antigen specificity and immunoregulatory signals, opening the door to future applications such as autoimmune diseases and allergic diseases.

Background

Autoimmune diseases occur when immune cells mistakenly recognize self-derived molecules as threats. More than 80 autoimmune disorders have been identified, affecting hundreds of millions of people worldwide. Current immunosuppressive therapies are non-specific and rarely produce long-term remission.

Antigen-specific regulatory T cells (Tregs) represent a promising therapeutic approach because they can selectively suppress only the disease-relevant immune responses while preserving protective immunity. However, safely generating such Tregs within patients remains a major technological challenge.

Engineered extracellular vesicles (EVs) offer a unique platform due to their natural biocompatibility, low immunogenicity, and ability to display multiple functional molecules. The AP-EV system developed by the Kanazawa University research team is the first EV-based platform to simultaneously deliver pMHCII, IL-2, and TGF-β, the essential triad required for antigen-specific Treg induction.