Co-stimulatory requirements of effector T cells at inflammatory sites

Expression and function of the OX40/OX40L costimulatory pair during herpes stromal keratitis

Herpes stromal keratitis (HSK) is an immunopathological disease regulated by Th1 CD4 T cells, which require APC and costimulation within the infected cornea to mediate disease. Recent studies suggest the OX40:OX40 ligand (OX40L) interaction enhances effector cell cytokine secretion at inflammatory sites. OX40(+) cells were detected in HSV-1-infected mouse corneas as early as 3 days postinfection (dpi), prior to the onset of HSK, and their frequency increased through 15 dpi, when all mice exhibited severe HSK. OX40L(+) cells were first detected at 7 dpi, coincident with the initiation of HSK. It is interesting that the OX40L(+) cells did not coexpress MHC Class II or the dendritic cell (DC) marker CD11c. Our findings demonstrate rapid infiltration of activated (OX40(+)) CD4(+) T cells into HSV-1-infected corneas and expression of OX40L on MHC Class II-negative cells but surprisingly, not on MHC Class II(+) CD11c(+) DC, which are present in the infected corneas and required for HSK. Moreover, neither local nor systemic treatment of mice with a blocking antibody to OX40L or with a blocking fusion protein altered the course of HSK significantly, possibly as a result of a lack of OX40L expression on functional APC.

CD154 signaling regulates the Th1 response to herpes simplex virus-1 and inflammation in infected corneas

Approximately 7 days after HSV-1 corneal infection, BALB/c mice develop tissue-destructive inflammation in the cornea termed herpes stromal keratitis (HSK), as well as periocular skin lesions that are characterized by vesicles, edema, and fur loss. CD4(+) T cells and Th1 cytokines contribute to both the immunopathology in the cornea and the eradication of viral replication in the skin. We demonstrate that disruption of CD40/CD154 signaling does not impact the initial expansion of CD4(+) T cells in the draining lymph nodes, but dramatically reduces the persistence and Th1 polarization of these cells. Despite the reduced Th1 response, CD154(-/-) mice developed HSK and periocular skin disease with similar kinetics and severity (as assessed by clinical examination) as wild-type (WT) mice. However, when the composition of the inflammatory infiltrate was examined by flow cytometric analysis, CD154(-/-) mice exhibited significantly fewer CD4(+) and CD8(+) T cells and neutrophils than WT mice at the peak of HSK. Moreover, CD4(+) T cells from infected corneas of CD154(-/-) mice produced significantly less IFN-gamma than those of WT mice when stimulated with viral Ags in vitro. The IFN-gamma production of cells from infected corneas of WT mice was not affected by addition of anti-CD154 mAb to the stimulation cultures. This suggests that CD154 signaling is required at the inductive phase, but not at the effector phase, of the Th1 response within the infected cornea. We conclude that local disruption of CD40/CD154 signaling is not likely to be a useful therapy for HSK.

The distribution of antigen in lymphoid tissues following its injection into the anterior chamber of the rat eye

Injection of Ag into the anterior chamber (AC) of the eye induces deviant immune responses. It has been proposed that Ag internalized by ocular APCs is presented in a tolerogenic fashion in the spleen. However, the nature and distribution of the Ag-bearing cells in the lymphoid organs remain unclear. Fluorescent-labeled Ag (dextran, BSA) injected into the AC of Lewis rats was detected in the subcapsular sinus of the right submandibular lymph nodes (LNs) and cervical LNs, the marginal zone of the spleen, and the medulla of the mesenteric LNs. In the spleen, Ag-bearing cells were CD1(+), CD11b(+), ED1(+), ED2(low), ED3(+), CD86(low), OX6(+), CD11c(-), ED5(-) and in the LNs were CD4(+), CD8(+), CD80(+), and OX41(+) suggesting these were lymphoid organ resident macrophages. These Ag-bearing macrophages were located adjacent to CD4(+) cells, CD8(+) cells, and NK cells in the LNs and spleen and to marginal zone B cells in the spleen. No interaction with gamma delta T cells was observed. The data demonstrates that Ag derived from the AC of the eye is mainly internalized by resident macrophages in the LNs and spleen which are ideally placed to interact with cells involved in the induction of deviant ocular immune responses. The extensive distribution of Ag in LNs draining the upper airway and gastrointestinal tracts, together with the phenotype of Ag-bearing cells in the lymphoid organs, suggests that Ag leaves the eye predominantly in a soluble form and implies other mechanisms of tolerance may contribute to ocular-specific immune responses.

CTLA4Ig delivered by high-capacity adenoviral vector induces stable expression of dystrophin in mdx mouse muscle

Adenoviral (Ad) vector-mediated gene delivery of normal, full-length dystrophin to skeletal muscle provides a promising strategy for the treatment of Duchenne muscular dystrophy (DMD), an X-linked recessive, dystrophin-deficient muscle disease. Studies in animal models suggest that successful DMD gene therapy by Ad vector-mediated gene transfer would be precluded by cellular and humoral immune responses induced by vector capsid and transgene proteins. To address the immunity induced by Ad vector-mediated dystrophin gene delivery to dystrophic muscle, we developed high-capacity adenoviral (HC-Ad) vectors expressing mouse dystrophin driven by the muscle creatine kinase promoter (AdmDys) and mCTLA4Ig (AdmCTLA4Ig) individually, or together from one vector (AdmCTLA4Ig/mDys). We found stable expression of dystrophin protein in the tibialis anterior muscles of mdx mice, coinjected with AdmCTLA4Ig and AdmDys, or injected alone with AdmCTLA4Ig/mDys, whereas the expression of dystrophin protein in the control group coinjected with AdmDys and an empty vector decreased by at least 50% between 2 and 8 weeks after administration. Additionally, we observed reductions in Ad vector-induced Th1 and Th2 cytokines, Ad vector-specific cytotoxic T lymphocyte activation and neutralizing anti-Ad antibodies in both experimental groups that received a mCTLA4Ig-expressing vector as compared to the control group. This study demonstrates that the coexpression of mCTLA4Ig and dystrophin in skeletal muscle provided by HC-Ad vector-mediated gene transfer can provide stable expression of dystrophin in immunocompetent, adult mdx mouse muscle and applies a potentially powerful strategy to overcome adaptive immunity induced by Ad vector-mediated dystrophin gene delivery toward the ultimate goal of treatment for DMD.

Blocking 4-1BB/4-1BB ligand interactions prevents herpetic stromal keratitis

Herpetic stromal keratitis (HSK) is a chronic inflammatory process in corneal stroma that results from recurrent HSV type 1 infection. We used the murine model of HSK to demonstrate the importance of the interaction between an inducible T cell costimulatory receptor, 4-1BB, and its ligand, 4-1BB ligand (4-1BBL), in the development of this disease. In BALB/c mice, HSK ordinarily induced by infection with the RE strain of herpes was prevented by blocking 4-1BB/4-1BBL interaction, either by deleting 4-1BB (in mutant 4-1BB(-/-) mice) or by introducing mAbs against 4-1BBL. The majority of T cells infiltrating the infected corneas were 4-1BB(+) activated effector cells that expressed cell surface markers CD44, CD25, and/or CD62L, as well as chemokine receptors CCR1, CCR2, and CCR5, and a limited number of TCR Vbeta chains (Vbeta8.1/8.2, Vbeta8.3, Vbeta10b, and Vbeta5.1/5.2, in order of abundance). Analysis of cell surface phenotypes showed that the failure to develop HSK in the 4-1BB(-/-) mice was associated with a reduced expression of CD62L at the time of T cell migration into the corneal stroma.