IL-35 is produced by regulatory T cells, and this novel cytokine can downregulate Th17 cell development and inhibit autoimmune inflammation. In this work, an rIL-35, as a single-chain fusion between murine IL-12p35 and EBV-induced gene 3, was expressed in yeast. This rIL-35 inhibited OVA-specific cellular and Ab responses in OVA-challenged recipients of DO11.10 CD4+ T cells. Likewise, IL-35 inhibited clinical manifestation of collagen-induced arthritis or could cease further disease exacerbation upon initiation of IL-35 treatment. Exogenous IL-35 treatments suppressed Th1 and Th17 cells and promoted CD39 expression by CD4+ T cells. Sorted CD25−CD39+CD4+ T cells from IL-35–treated mice produced IL-10 and, upon adoptive transfer, were sufficiently potent to inhibit subsequent development of inflammation in mice with collagen-induced arthritis, whereas sorted CD25+CD39+ CD4+ T cells showed reduced potency. IL-35 treatments of IL-10−/− mice failed to induce protective CD39+CD4+ T cells, demonstrating the effector role of IL-10 by IL-35 immunosuppression.

Regulatory T (Treg) cells show promise for treating autoimmune diseases, but their induction to elevated potency has been problematic when the most optimally derived cells are from diseased animals. To circumvent reliance on autoantigen-reactive Treg cells, stimulation to myelin-independent Ags may offer a viable alternative while maintaining potency to treat experimental autoimmune encephalomyelitis (EAE). The experimental Salmonella vaccine expressing colonization factor Ag I possesses anti-inflammatory properties and, when applied therapeutically, reduces further development of EAE in SJL mice. To ascertain Treg cell dependency, a kinetic analysis was performed showing increased levels of FoxP3+CD25+CD4+ T cells. Inactivation of these Treg cells resulted in loss of protection. Adoptive transfer of the vaccine-induced Treg cells protected mice against EAE with greater potency than naive or Salmonella vector-induced Treg cells, and cytokine analysis revealed enhanced production of TGF-β, not IL-10. The development of these Treg cells in conjunction with immune deviation by Th2 cells optimally induced protective Treg cells when compared those induced in the absence of Th2 cells. These data show that Treg cells can be induced to high potency to non-disease-inducing Ags using a bacterial vaccine.

No abstract

Oral immunization with a Salmonella vaccine vector expressing enterotoxigenic E. coli colonization factor antigen I (CFA/I) can protect against collagen-induced arthritis (CIA) by dampening IL-17 and IFN-γ via enhanced IL-4, IL-10, and TGF-β. To identify the responsible regulatory CD4+ T cells making the host refractory to CIA, Salmonella-CFA/I induced CD39+CD4+ T cells with enhanced apyrase activity relative to Salmonella vector-immunized mice. Adoptive transfer of vaccine-induced CD39+CD4+ T cells into CIA mice conferred complete protection, while CD39−CD4+ T cells did not. Subsequent analysis of vaccinated FoxP3-GFP mice revealed the CD39+ T cells were composed of FoxP3-GFP− and FoxP3-GFP+ subpopulations. Although each adoptively transferred Salmonella-CFA/I-induced FoxP3− and FoxP3+CD39+CD4+ T cells could protect against CIA, each subset was not as efficacious as total CD39+CD4+ T cells, suggesting their interdependence for optimal protection. Cytokine analysis revealed FoxP3− CD39+CD4+ T cells produced TGF-β, and FoxP3+CD39+CD4+ T cells produced IL-10, showing a segregation of function. Moreover, donor FoxP3-GFP− CD4+ T cells converted to FoxP3-GFP+ CD39+CD4+ T cells in the recipients, showing plasticity of these regulatory T cells. TGF-β was found to be essential for protection since in vivo TGF-β neutralization reversed activation of cAMP-response element-binding protein (CREB) and reduced the development of CD39+CD4+ T cells. Thus, CD39 apyrase-expressing CD4+ T cells stimulated by Salmonella-CFA/I are composed of TGF-β-producing FoxP3− CD39+CD4+ T cells and support the stimulation of IL-10-producing FoxP3+ CD39+CD4+ T cells.