Gene therapy using an ortholog of human fragile X mental retardation protein partially rescues behavioral abnormalities and EEG activity.

Fragile X syndrome (FXS), a neurodevelopmental disorder with no known cure, is caused by a lack of expression of the fragile X mental retardation protein (FMRP). As a single-gene disorder, FXS is an excellent candidate for viral-vector-based gene therapy, although that is complicated by the existence of multiple isoforms of FMRP, whose individual cellular functions are unknown. We studied the effects of rat and mouse orthologs of human isoform 17, a major expressed isoform of FMRP. Injection of neonatal Fmr1 knockout rats and mice with adeno-associated viral vectors (AAV9 serotype) under the control of an MeCP2 mini-promoter resulted in widespread distribution of the FMRP transgenes throughout the telencephalon and diencephalon. Transgene expression occurred mainly in non-GABAergic neurons, with little expression in glia. Early postnatal treatment resulted in partial rescue of the Fmr1 KO rat phenotype, including improved social dominance in treated Fmr1 KO females and partial rescue of locomotor activity in males. Electro-encephalogram (EEG) recordings showed correction of abnormal slow-wave activity during the sleep-like state in male Fmr1 KO rats. These findings support the use of AAV-based gene therapy as a treatment for FXS and specifically demonstrate the potential therapeutic benefit of human FMRP isoform 17 orthologs.

PI3Kγ Deficient NOD-Mice Are Protected from Diabetes by Restoring the Balance of Regulatory to Effector-T-Cells.

With a steady increase in its incidence and lack of curative treatment, type 1 diabetes (T1D) has emerged as a major health problem worldwide. To design novel effective therapies, there is a pressing need to identify regulatory targets controlling the balance of autoreactive to regulatory-T-cells (Tregs). We previously showed that the inhibition of the γ-subunit of the Phosphoinositide-3-kinase (PI3K), significantly suppress autoimmune-diabetes. To further delineate the mechanisms and the selectivity of specific immune modulation by PI3Kγ-inhibition, we developed a new NOD mouse model of T1D lacking the γ-subunit of PI3K. Strikingly, the loss of PI3Kγ protected 92% of the NOD-mice from developing spontaneous diabetes. The NOD.PI3Kγ-/- mice are protected from insulitis secondary to a defect in CD4 and CD8 autoreactive-T-cells activation and survival. In addition, PI3Kγ-deficiency promoted Treg generation in-vitro and in-vivo. Furthermore, PI3Kγ-inhibitor (AS605240) inhibited proliferation and cytokine production of a human CD4+ T-cell clone specific for GAD555-567 peptide that was isolated from a patient with T1D. These studies demonstrate the key role of the PI3Kγ pathway in regulating autoimmune-diabetes and provide rationales for future devise of anti- PI3Kγ therapy in T1D.

The mechanisms of up-regulation of dendritic cell activity by oxidative stress.

Whereas DC have increasingly been recognized for their role in activating the inflammatory cascades during IRIs, the mechanisms by which oxidative stress enhances DC activation remain to be explored. We examined the role of oxidative stress on two important features of DC: T cell activation and trafficking. Bone marrow-derived OS-DC were compared with untreated DC. DC exposed to oxidative stress augmented allogeneic T cell proliferation and showed increased migration in a chemotaxis chamber. These results were confirmed by using hypoxanthine and xanthine oxidase as another inducer of oxidative stress. We used OT-II and OT-I mice to assess the effect of oxidative stress on DC activation of OVA-specific CD4(+) and CD8(+) T cells, respectively. Oxidative stress increased DC capacity to promote OVA-specific CD4(+) T cell activity, demonstrated by an increase in their proliferation and production of IFN-γ, IL-6, and IL-2 proinflammatory cytokines. Whereas oxidative stress increased the DC ability to stimulate IFN-γ production by OVA-specific CD8(+) T cells, cellular proliferation and cytotoxicity were not affected. Compared with untreated DC, oxidative stress significantly reduced the capacity of DC to generate T(regs), which were restored by using anti-IL-6. With regard to DC trafficking, whereas oxidative stress increased DC expression of p-Akt and p-NF-κB, targeting PI3Kγ and NF-κB pathways abrogated the observed increase in DC migration. Our data propose novel insights on the activation of DC by oxidative stress and provide rationales for targeted therapies, which can potentially attenuate IRI.

Interruption of dendritic cell-mediated TIM-4 signaling induces regulatory T cells and promotes skin allograft survival.

Dendritic cells (DCs) are the central architects of the immune response, inducing inflammatory or tolerogenic immunity, dependent on their activation status. As such, DCs are highly attractive therapeutic targets and may hold the potential to control detrimental immune responses. TIM-4, expressed on APCs, has complex functions in vivo, acting both as a costimulatory molecule and a phosphatidylserine receptor. The effect of TIM-4 costimulation on T cell activation remains unclear. In this study, we demonstrate that Ab blockade of DC-expressed TIM-4 leads to increased induction of induced regulatory T cells (iTregs) from naive CD4(+) T cells, both in vitro and in vivo. iTreg induction occurs through suppression of IL-4/STAT6/Gata3-induced Th2 differentiation. In addition, blockade of TIM-4 on previously activated DCs still leads to increased iTreg induction. iTregs induced under TIM-4 blockade have equivalent potency to control and, upon adoptive transfer, significantly prolong skin allograft survival in vivo. In RAG(-/-) recipients of skin allografts adoptively transferred with CD4(+) T cells, we show that TIM-4 blockade in vivo is associated with a 3-fold prolongation in allograft survival. Furthermore, in this mouse model of skin transplantation, increased induction of allospecific iTregs and a reduction in T effector responses were observed, with decreased Th1 and Th2 responses. This enhanced allograft survival and protolerogenic skewing of the alloresponse is critically dependent on conversion of naive CD4(+) to Tregs in vivo. Collectively, these studies identify blockade of DC-expressed TIM-4 as a novel strategy that holds the capacity to induce regulatory immunity in vivo.

Serine protease inhibitor 6 plays a critical role in protecting murine granzyme B-producing regulatory T cells.

Regulatory T cells (Tregs) play a pivotal role in the maintenance of immune tolerance and hold great promise as cell therapy for a variety of immune-mediated diseases. However, the cellular mechanisms that regulate Treg maintenance and homeostasis have yet to be fully explored. Although Tregs express granzyme-B (GrB) to suppress effector T cells via direct killing, the mechanisms by which they protect themselves from GrB-mediated self-inflicted damage are unknown. To our knowledge, we show for the first time that both induced Tregs and natural Tregs (nTregs) increase their intracellular expression of GrB and its endogenous inhibitor, serine protease inhibitor 6 (Spi6) upon activation. Subcellular fractionation and measurement of GrB activity in the cytoplasm of Tregs show that activated Spi6(-/-) Tregs had significantly higher cytoplasmic GrB activity. We observed an increase in GrB-mediated apoptosis in Spi6(-/-) nTregs and impaired suppression of alloreactive T cells in vitro. Spi6(-/-) Tregs were rescued from apoptosis by the addition of a GrB inhibitor (Z-AAD-CMK) in vitro. Furthermore, adoptive transfer experiments showed that Spi6(-/-) nTregs were less effective than wild type nTregs in suppressing graft-versus-host disease because of their impaired survival, as shown in our in vivo bioluminescence imaging. Finally, Spi6-deficient recipients rejected MHC class II-mismatch heart allografts at a much faster rate and showed a higher rate of apoptosis among Tregs, as compared with wild type recipients. To our knowledge, our data demonstrate, for the first time, a novel role for Spi6 in Treg homeostasis by protecting activated Tregs from GrB-mediated injury. These data could have significant clinical implications for Treg-based therapy in immune-mediated diseases.