A team from the Nano Life Science Institute (WPI-NanoLSI) and the Faculty of Medicine at Kanazawa University has developed engineered extracellular vesicles (EVs) that can induce antigen-specific regulatory T cells (Tregs). The research, published in Drug Delivery, addresses a key challenge in treating autoimmune and allergic diseases by aiming for more precise immune system control.
Autoimmune diseases occur when the immune system attacks the body's own tissues. Existing treatments often involve broad immunosuppression, which can reduce symptoms but also compromise the body's ability to fight infections. Scientists have long sought therapies that target only disease-related antigens, known as "antigen-specific immune tolerance."
Regulatory T cells are responsible for maintaining this tolerance. However, it has been difficult to safely and efficiently induce antigen-specific Tregs within living organisms. To address this issue, researchers Shota Imai, Tomoyoshi Yamano, Rikinari Hanayama, and their colleagues created "antigen-presenting extracellular vesicles" (AP-EVs-Treg). These vesicles present peptide–MHC class II complexes for antigen recognition along with interleukin-2 (IL-2) and transforming growth factor-β (TGF-β), both necessary for Treg differentiation.
According to the researchers: "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."
The technology is adaptable; AP-EVs can be loaded with different antigens relevant to various autoimmune diseases such as multiple sclerosis. In animal studies, AP-EVs selectively activated specific CD4⁺ T cells based on their pMHCII specificity. The induction of Foxp3 required rapamycin—a drug known to encourage Treg development—when used alongside AP-EVs.
"The combination of AP-EVs and rapamycin markedly increased the generation of antigen-specific Tregs in vivo," noted the researchers. They described this as a synergistic approach that could help restore immune tolerance under physiological conditions.
Unlike some other approaches using mRNA or nanoparticles, EVs are naturally derived and compatible with biological systems. Their modular design means they can be tailored for specific antigens or regulatory signals.
The new platform is notable because it is reportedly the first EV-based system capable of simultaneously delivering all three key components—pMHCII, IL-2, and TGF-β—required for inducing antigen-specific regulatory T cells.
Autoimmune disorders affect millions worldwide and current treatments do not typically offer long-term remission due to their lack of specificity. Targeting disease-relevant immune responses while preserving general immunity remains an important goal in developing safer therapies.
