Kaustuv Banerjee

Bystander Activation Involving T Lymphocytes in Herpetic Stromal Keratitis

Herpes simplex virus infection of mouse corneas can lead to the development of an immunopathological lesion, termed herpetic stromal keratitis (HSK). Such lesions also occur in TCR-transgenic mice backcrossed to SCID (TgSCID) that are unable to mount detectable HSV-specific immune responses. The present study demonstrates that lesion expression in such mice depends on continuous viral replication, whereas in immunocompetent mice, lesions occurred even if virus replication was terminated at 4 days after infection. The continuous replication in TgSCID mice was considered necessary to produce an activating stimulus to CD4+ T cells that invade the cornea. Lesions in TgSCID were resistant to control by cyclosporin A, but were inhibited by treatment with rapamycin. This result was interpreted to indicate that T cell activation involved a non-TCR-mediated cytokine-driven bystander mechanism. Bystander activation was also shown to play a role in HSK lesions in immunocompetent mice. Accordingly, in immunocompetent DO11.10 mice, lesions were dominated by KJ1.26+ OVA-specific CD4+ T cells that were unreactive with HSV. In addition, KJ1.26+ HSV nonimmune cells parked in ocularly infected BALB/c mice were demonstrable in HSK lesions. These results provide insight for the choice of new strategies to manage HSK, an important cause of human blindness.

CXCR2−/− Mice Show Enhanced Susceptibility to Herpetic Stromal Keratitis: A Role for IL-6-Induced Neovascularization

Ocular infection with HSV results in a blinding immunoinflammatory lesion known as herpetic stromal keratitis (HSK). Early preclinical events include inflammatory cell, mainly neutrophils, infiltration of the stroma, and neovascularization. To further evaluate the role of neutrophils in pathogenesis, HSV infection was compared in BALB/c and mice of the same background, but lacking CXCR2, the receptor for chemokines involved in neutrophil recruitment. Our results show clear differences in the outcome of ocular HSV infection in CXCR2−/− compared with control BALB/c mice. Thus, CXCR2−/− animals had minimal PMN influx during the first 7 days postinfection, and this correlated with a longer duration of virus infection in the eye compared with BALB/c mice. The CXCR2−/− mice were also more susceptible to HSV-induced lesions and developed HSK upon exposure to a dose of HSV that was minimally pathogenic to BALB/c mice. The basis for the greater HSK lesion susceptibility of CXCR2−/− mice was associated with an elevated IL-6 response, which appeared in turn to induce the angiogenic factor, vascular endothelial growth factor. Our results serve to further demonstrate the critical role of angiogenesis in the pathogenesis of ocular lesions.

Mice Transgenic for IL-1 Receptor Antagonist Protein Are Resistant to Herpetic Stromal Keratitis: Possible Role for IL-1 in Herpetic Stromal Keratitis Pathogenesis

Ocular infection with HSV may result in the blinding immunoinflammatory lesion stromal keratitis (SK). This represents a CD4+ T cell-mediated immunopathologic lesion in both humans and a mouse model. Early events in the pathogenesis that set the stage for SK are poorly understood. The present study evaluates the role of IL-1 using a transgenic mouse that overexpresses the IL-1 receptor antagonist (IL-1ra) protein. Such transgenic mice were markedly resistant to SK compared with IL-1ra−/− and C57BL/6 control animals. The resistance was shown to be the consequence of reduced expression of molecules such as IL-6, macrophage-inflammatory protein-2, and vascular endothelial growth factor, normally up-regulated directly or indirectly by IL-1. A critical event impaired in IL-1ra transgenic mice was vascular endothelial growth factor production with a consequent marked reduction in angiogenesis, an essential step in SK pathogenesis. Targeting IL-1 could prove to be a worthwhile therapeutic approach to control SK, an important cause of human blindness.

Herpetic eye disease: immunopathogenesis and therapeutic measures.

Infection of the cornea with herpes simplex virus (HSV) can result in a chronic disease called herpetic stromal keratitis (HSK). The disease represents one of the leading causes of infectious blindness in the Western world. Immune-mediated cellular damage is suspected in the pathogenesis of human HSK. The murine model has been pivotal in further establishing HSK as an immunopathological disease. This article reviews understanding of HSK, both in humans and in the mouse model, with an emphasis on possible future therapeutic strategies to counteract this blinding immunoinflammatory disease.

Elucidating the protective and pathologic T cell species in the virus‐induced corneal immunoinflammatory condition herpetic stromal keratitis

Herpetic stromal keratitis (HSK) results in postinfection with Herpes simplex virus type 1 (HSV‐1). The pathogenesis involves tissue damage by the host immune system, classifying HSK as an immunopathological disease. The crucial disease orchestrating cells is thought to be the T lymphocytes. The present study elucidates pathogenic and protective T cell subsets involved in the development of HSK using the gBT mice, which possess a monoclonal population of CD8+ T cells reactive to a HSV immunodominant epitope. Results show that HSV‐reactive CD8+ T cells enter infected corneas during the acute but not the chronic phase of the disease during which the predominant population is CD4+ T cells. Adoptive transfer experiments in T and B cell‐deficient recombination‐activating gene knockout mice revealed that HSV‐reactive CD8+ T cells are capable of ocular virs clearance, possibly through a combination of corneal and peripheral nervous system antiviral effects, but are not involved in lesion development. CD4+ T cells of the virus‐specific or nonspecific species emerged as the pathogenic T cells capable of precipitating disease. These observations have the potential to yield important treatment strategies by targeting specific cell types in HSK.

Herpetic stromal keratitis in the absence of viral antigen recognition

Herpetic stromal keratitis (HSK), resulting from ocular infection with herpes simplex virus (HSV), is thought to represent a T cell mediated immunopathologic lesion. Antigens recognized by the inflammatory T cells remain unresolved and non-TCR mediated activation of T cells (bystander activation) is considered as also involved. This report documents further evidence for the bystander activation mechanisms using three T cell transgenic RAG-/- mouse strains. Accordingly HSK occurred in PCC RAG-/-, P14 RAG-/-, and OT-1 RAG-/- mice. In none of the models could HSV specific T cell reactivity be demonstrated and animals were unprotected from lesion development by immunization prior to HSV ocular infection. The results support the role of bystander activation as a mechanism of T cell mediated immunopathology and show that CD8(+) as well as CD4(+) T cells can participate in HSK lesion development.

Counteracting corneal immunoinflammatory lesion with interleukin‐1 receptor antagonist protein

Herpetic stromal keratitis (HSK) is a T cell‐orchestrated, immunoinflammatory lesion that results from corneal Herpes simplex virus infection. Previous reports indicate an essential role for proinflammatory cytokine interleukin (IL)‐1 in HSK pathogenesis. The present study evaluates the efficacy of IL‐1 receptor antagonist (IL‐1 ra) protein in the management of HSK. Mice receiving IL‐1 ra had diminished disease severity. The administration of IL‐1 ra was shown to reduce the influx into the cornea of cells of the innate and adaptive immune response. In addition, the treatment diminished corneal vascular endothelial growth factor levels, resulting in reduced angiogenic response. Our results show the importance of targeting early proinflammatory molecules such as IL‐1 to counteract HSK and advocate IL‐1 ra as an effective agent to achieve this.

Role of Inflammatory Cytokine-Induced Cycloxygenase 2 in the Ocular Immunopathologic Disease Herpetic Stromal Keratitis

ABSTRACT Ocular infection with herpes simplex virus (HSV) results in a blinding immunoinflammatory stromal keratitis (SK) lesion. Early preclinical events include polymorphonuclear neutrophil (PMN) infiltration and neovascularization in the corneal stroma. We demonstrate here that HSV infection of the cornea results in the upregulation of the cycloxygenase 2 (COX-2) enzyme. Early after infection, COX-2 was produced from uninfected stromal fibroblasts as an indirect effect of virus infection. Subsequently, COX-2 may also be produced from other inflammatory cells that infiltrate the cornea. The induction of COX-2 is a critical event, since inhibition of COX-2 with a selective inhibitor was shown to reduce corneal angiogenesis and SK severity. The administration of a COX-2 inhibitor resulted in compromised PMN infiltration into the cornea, as well as diminished corneal vascular endothelial growth factor levels, likely accounting for the reduced angiogenic response. COX-2 stimulation by HSV infection represents a critical early event accessible for therapy and the control of SK severity.

Protective and pathological roles of virus-specific and bystander CD8+ T cells in herpetic stromal keratitis.

Herpetic stromal keratitis (HSK), resulting from corneal HSV-1 infection, represents a T cell-mediated immunopathologic lesion. In T cell transgenic mice on a SCID or RAG knockout background, the T cells mediating lesions are unreactive to viral Ags. In these bystander models, animals develop ocular lesions but are unable to control infection. Transfer of HSV-immune cells into a CD8+ T cell bystander model resulted in clearance of virus from eyes, animals survived, and lesions developed to greater severity. However, the adoptively transferred CD8+ T cells were not evident in lesions, although they were readily detectable in the lymphoid tissues as well as in the peripheral and CNS. Our results indicate that viral-induced tissue damage can be caused by bystander cells, but these fail to control infection. Immune CD8+ T cells trigger clearance of virus from the eye, but this appears to result by the T cells acting at sites distal to the cornea. A case is made that CD8+ T cell control is expressed in the trigeminal ganglion, serving to curtail a source of virus to the cornea.

In vivo rescue of defective memory CD8+ T cells by cognate helper T cells

The magnitude and efficacy of CD8+ T cell memory may notably regress, especially if immune induction occurs in the absence of adequate CD4+ help. This report demonstrates that this CD8+ memory malfunction could be remedied if a source of cognate antigen‐recognizing helper cells were provided during recall. The inability of adoptive transfer of memory SIINFEKL‐specific CD8 cells to reject tumors was overcome if recipients were primed for ovalbumin‐specific helper cell responses. Additionally, animals primed for a SIINFEKL‐specific memory response and incapable of rejecting the tumor could regain protective immunity if given helper cells. This pattern of CD8+ T cell functional rescue or reprogramming by helper cell transfer was replicated using a Herpes simplex virus antiviral immunity system. Our results could mean that therapeutic vaccine approaches could be designed to compensate situations that have defective CD8+ T cell function.