Nanohydroxyapatite Coating Attenuates Fibrotic and Immune Responses to Promote Keratoprosthesis Biointegration in Advanced Ocular Surface Disorders

Keratoprosthesis (KPro) implantation is frequently the only recourse for patients with severe corneal disease. However, problems arise due to inadequate biointegration of the KPro, particularly the PMMA optical cylinder, such as tissue detachment, tissue melting, or eye-threatening infection in the interface. Here, using the AuroKPro as a model prosthesis, a surface functionalization approach─coating the optical cylinder with nanohydroxyapatite (nHAp)─was trialed in rabbit eyes with and without a proceeding chemical injury. In chemically injured eyes, which simulated total limbal epithelial stem cell deficiency, clear benefits were conferred by the coating. The total modified Hackett-McDonald score and area of tissue apposition differences 12 weeks after implantation were 5.0 and 22.5%, respectively. Mechanical push-in tests revealed that 31.8% greater work was required to detach the tissues. These differences were less marked in uninjured eyes, which showed total score and tissue apposition differences of 2.5 and 11.5%, respectively, and a work difference of 23.5%. The improved biointegration could be contributed by the attenuated expression of fibronectin (p = 0.036), collagen 3A1 (p = 0.033), and α-smooth muscle actin (p = 0.045)─proteins typically upregulated during nonadherent fibrous capsule envelopment of bioinert material─adjacent to the optical cylinders. The coating also appeared to induce a less immunogenic milieu in the ocular surface tissue, evidenced by the markedly lower expression of tear proteins associated with immune and stimulus responses. Collectively, the level of these tear proteins in eyes with coated prostheses was 1.1 ± 13.0% of naïve eyes: substantially lower than with noncoated KPros (246.5 ± 79.3% of naïve, p = 0.038). Together, our results indicated that nHAp coating may reduce the risk of prosthesis failure in severely injured eyes, which are representative of the cohort of KPro patients.

IL-36γ Augments Ocular Angiogenesis by Promoting the Vascular Endothelial Growth Factor-Vascular Endothelial Growth Factor Receptor Axis

Prevention of inflammatory angiogenesis is critical for suppressing chronic inflammation and inhibiting inflammatory tissue damage. Angiogenesis is particularly detrimental to the cornea because pathologic growth of new blood vessels can lead to marked vision impairment and even loss of vision. The expression of proinflammatory cytokines by injured tissues exacerbates the inflammatory cascade, including angiogenesis. IL-36 cytokine, a subfamily of the IL-1 superfamily, consists of three proinflammatory agonists, IL-36α, IL-36β, and IL-36γ, and an IL-36 receptor antagonist (IL-36Ra). Data from the current study indicate that human vascular endothelial cells constitutively expressed the cognate IL-36 receptor. The current investigation, for the first time, characterized the direct contribution of IL-36γ to various angiogenic processes. IL-36γ up-regulated the expression of vascular endothelial growth factors (VEGFs) and their receptors VEGFR2 and VEGFR3 by human vascular endothelial cells, suggesting that IL-36γ mediates the VEGF-VEGFR signaling by endothelial cells. Moreover, by using a naturally occurring antagonist IL-36Ra in a murine model of inflammatory angiogenesis, this study demonstrated that blockade of endogenous IL-36γ signaling results in significant retardation of inflammatory angiogenesis. The current investigation on the proangiogenic function of IL-36γ provides novel evidence of the development of IL-36γ-targeting strategies to hamper inflammatory angiogenesis.

The cornea IV immunology, infection, neovascularization, and surgery chapter 1: Corneal immunology

PURPOSE

of Review: This review offers an informed and up-to-date insight on the immune profile of the cornea and the factors that govern the regulation of such a unique immune environment.

SUMMARY

The cornea is a unique tissue that performs the specialized task of allowing light to penetrate for visual interpretation. To accomplish this, the ocular surface requires a distinct immune environment that is achieved through unique structural, cellular and molecular factors. Not only must the cornea be able to fend off invasive infectious agents but also control the inflammatory response as to avoid collateral, and potentially blinding damage; particularly of post-mitotic cells such as the corneal endothelium. To combat infections, both innate and adaptive arms of the inflammatory immune response are at play in the cornea. Dendritic cells play a critical role in coordinating both these responses in order to fend off infections. On the other side of the spectrum, the ocular surface is also endowed with a variety of anatomic and physiologic components that aid in regulating the immune response to prevent excessive, potentially damaging, inflammation. This attenuation of the immune response is termed immune privilege. The balance between pro and anti-inflammatory reactions is key for preservation of the functional integrity of the cornea.

RECENT FINDINGS

The understanding of the molecular and cellular factors governing corneal immunology and its response to antigens is a growing field. Dendritic cells in the normal cornea play a crucial role in combating infections and coordinating the inflammatory arms of the immune response, particularly through coordination with T-helper cells. The role of neuropeptides is recently becoming more highlighted with different factors working on both sides of the inflammatory balance.

Ocular manifestations of autoimmune polyendocrinopathy syndrome type 1

PURPOSE OF REVIEW

The ocular manifestations in autoimmune polyendocrinopathy syndrome type 1 (APS1) are frequent and have a poor prognosis. The phenotype of these APS1-associated ocular features have been recently characterized in molecularly confirmed patients with APS1.

RECENT FINDINGS

Keratopathy and retinopathy can be severe manifestations of APS1. Heterogeneous corneal involvement can be observed, ranging from minimal superficial punctate staining to severe stromal scarring with deep corneal neovascularization. This phenotypic heterogeneity, observed even in patients with identical AIRE mutations, is suggestive of a poor genotype-phenotype correlation. Similarly, in patients with retinopathy, peripheral pigmentary changes are noted in all cases, yet with heterogeneous severity, ranging from isolated patchy atrophy of the retinal pigment epithelium to a retinitis pigmentosa-like fundus. Macular atrophy with vision loss is found in most cases. The severity of ophthalmic findings is uncorrelated to that of systemic manifestations. An autoimmune origin with specific autoantibodies directed against corneal and/or retinal autoantigens is the main mechanism believed to be responsible for the ocular manifestations of APS1.

SUMMARY

Progressive keratopathy and/or retinopathy can lead to severe visual loss and pain in patients with APS1. Although no treatment has shown efficacy regarding the APS1-associated ocular manifestations, ophthalmologic examinations are recommended in these patients.

[Clinical and immunological comparisons of therapeutic regimens for corneal infiltrates secondary to adenoviral keratoconjunctivitis]

The problem with post-adenoviral corneal infiltrates is that they cause a significant and persistent decrease in visual function, while corticosteroids in monotherapy bring only temporary improvement.

AIM

to perform a comparative evaluation of topical corticosteroids and 0.05% cyclosporine A efficacy in the treatment of post-adenoviral corneal infiltrates on the basis of clinical presentation and local cytokine status.

MATERIAL AND METHODS

The study involved two groups of patients after adenoviral keratoconjunctivitis: group 1 (25 patients, 45 eyes) were prescribed a diminishing regimen of corticosteroid eye drops for 12 weeks and corneal protectors; group 2 (24 patients, 42 eyes) received the same treatment as described above plus topical 0.05% cyclosporine A for 6 months. The follow-up period was from 6 to 12 months. Visual acuity measurements, biomicroscopy, and pneumatic tonometry were performed at months 1, 3, and 6. Local cytokine status was assessed by studying cytokine gene expression in cell culture from conjunctival scrapings and cytokines levels in the supernatant. The tests were done before the beginning of the treatment in both groups, at month 1 in group 1, at month 4 in group 2 (i.e. in a month after the cessation of dexamethasone) and also in a group of healthy volunteers (30 persons, 30 eyes).

RESULTS

Long-term combined anti-inflammatory therapy with corticosteroids and 0.05% cyclosporine A in patients with post-adenoviral corneal infiltrates has yielded positive clinical results, including a persistent increase in visual acuity and complete resolution of corneal opacities (92.8%). In addition, we revealed a correlation between local cytokine status changes and clinical results.

CONCLUSION

The proposed therapeutic regimen enabled complete suppression of residual interferon-α antiviral activity, an increase in interleukin-4 that regulates local humoral immunity, and a decrease (down to a complete suppression) in anti-inflammatory interleukin-2, which is responsible for activation of cell-mediated immunity, thus, resulting in resolution of the immune-mediated inflammation in the cornea.

2-O-Sulfated Domains in Syndecan-1 Heparan Sulfate Inhibit Neutrophil Cathelicidin and Promote Staphylococcus aureus Corneal Infection

Ablation of syndecan-1 in mice is a gain of function mutation that enables mice to significantly resist infection by several bacterial pathogens. Syndecan-1 shedding is induced by bacterial virulence factors, and inhibition of shedding attenuates bacterial virulence, whereas administration of purified syndecan-1 ectodomain enhances virulence, suggesting that bacteria subvert syndecan-1 ectodomains released by shedding for their pathogenesis. However, the pro-pathogenic functions of syndecan-1 ectodomain have yet to be clearly defined. Here, we examined how syndecan-1 ectodomain enhances Staphylococcus aureus virulence in injured mouse corneas. We found that syndecan-1 ectodomain promotes S. aureus corneal infection in an HS-dependent manner. Surprisingly, we found that this pro-pathogenic activity is dependent on 2-O-sulfated domains in HS, indicating that the effects of syndecan-1 ectodomain are structure-based. Our results also showed that purified syndecan-1 ectodomain and heparan compounds containing 2-O-sulfate motifs inhibit S. aureus killing by antimicrobial factors secreted by degranulated neutrophils, but does not affect intracellular phagocytic killing by neutrophils. Immunodepletion of antimicrobial factors with staphylocidal activities demonstrated that CRAMP, a cationic antimicrobial peptide, is primarily responsible for S. aureus killing among other factors secreted by degranulated neutrophils. Furthermore, we found that purified syndecan-1 ectodomain and heparan compounds containing 2-O-sulfate units potently and specifically inhibit S. aureus killing by synthetic CRAMP. These results provide compelling evidence that a specific subclass of sulfate groups, and not the overall charge of HS, permits syndecan-1 ectodomains to promote S. aureus corneal infection by inhibiting a key arm of neutrophil host defense.

Diversity of virulence phenotypes among type III secretion negative Pseudomonas aeruginosa clinical isolates

Pseudomonas aeruginosa is a frequent cause of acute infections. The primary virulence factor that has been linked to clinical disease is the type III secretion system, a molecular syringe that delivers effector proteins directly into host cells. Despite the importance of type III secretion in dictating clinical outcomes and promoting disease in animal models of infections, clinical isolates often do not express the type III secretion system in vitro. Here we screened 81 clinical P. aeruginosa isolates for secretion of type III secretion system substrates by western blot. Non-expressing strains were also subjected to a functional test assaying the ability to intoxicate epithelial cells in vitro, and to survive and cause disease in a murine model of corneal infection. 26 of 81 clinical isolates were found to be type III secretion negative by western blot. 17 of these 26 non-expressing strains were tested for their ability to cause epithelial cell rounding. Of these, three isolates caused epithelial cell rounding in a type III secretion system dependent manner, and one strain was cytotoxic in a T3SS-independent manner. Five T3SS-negative isolates were also tested for their ability to cause disease in a murine model of corneal infection. Of these isolates, two strains caused severe corneal disease in a T3SS-independent manner. Interestingly, one of these strains caused significant disease (inflammation) despite being cleared. Our data therefore show that P. aeruginosa clinical isolates can cause disease in a T3SS-independent manner, demonstrating the existence of novel modifiers of clinical disease.

The RodA hydrophobin on Aspergillus fumigatus spores masks dectin-1- and dectin-2-dependent responses and enhances fungal survival in vivo

Aspergillus and Fusarium species are important causes of fungal infections worldwide. Airborne spores (conidia) of these filamentous fungi express a surface protein that confers hydrophobicity (hydrophobin) and covers cell wall components that would otherwise induce a host immune cell response. Using a mutant Aspergillus fumigatus strain (ΔrodA) that does not express the RodA hydrophobin, and Aspergillus and Fusarium conidia from clinical isolates that were treated with hydrofluoric acid (which removes the A. fumigatus RodA protein), we observed increased surface exposure of β1,3-glucan and α-mannose on Aspergillus and Fusarium conidia. We also found that ΔrodA and hydrofluoric acid-treated conidia stimulate significantly higher NF-κB p65 nuclear translocation and cytokine production by macrophages from C57BL/6, but not from Dectin-1(-/-) or Dectin-2(-/-) mice. Using a murine model of A. fumigatus corneal infection, we showed that ΔrodA conidia induced significantly higher cytokine production, neutrophil infiltration, and more rapid fungal clearance from C57BL/6 corneas compared with the parent G10 strain, which was dependent on Dectin-1 and Dectin-2. Together, these findings identify the hydrophobin RodA as a virulence factor that masks Dectin-1 and Dectin-2 recognition of conidia, resulting in impaired neutrophil recruitment to the cornea and increased fungal survival and clinical disease.

Removal of the basement membrane enhances corneal wound healing

Recurrent corneal erosions are painful and put patients' vision at risk. Treatment typically begins with debridement of the area around the erosion site followed by more aggressive treatments. An in vivo mouse model has been developed that reproducibly induces recurrent epithelial erosions in wild-type mice spontaneously within two weeks after a single 1.5 mm corneal debridement wound created using a dulled-blade. This study was conducted to determine whether 1) inhibiting MMP9 function during healing after dulled-blade wounding impacts erosion development and 2) wounds made with a rotating-burr heal without erosions. Oral or topical inhibition of MMPs after dulled-blade wounding does not improve healing. Wounds made by rotating-burr heal with significantly fewer erosions than dulled-blade wounds. The localization of MMP9, β4 integrin and basement membrane proteins (LN332 and type VII collagen), immune cell influx, and reinnervation of the corneal nerves were compared after both wound types. Rotating-burr wounds remove the anterior basement membrane centrally but not at the periphery near the wound margin, induce more apoptosis of corneal stromal cells, and damage more stromal nerve fibers. Despite the fact that rotating-burr wounds do more damage to the cornea, fewer immune cells are recruited and significantly more wounds resolve completely.

HLA types in corneal diseases

Evaluation of the results of HLA typing of 187 patients grouped into herpetic keratitis (37), non-herpetic keratitis (43), keratoconus (42), endothelial dystrophy (23), stromal dystrophy (13), lues (5), and injuries (24), failed to show convincing deviations in any of the groups from a normal control series (2900 persons). Yet, as for the herpes group, a rise in B5 must strongly be suspected. The data are presented and possible implications are discussed.

Histopathologic and immunologic aspects of alphacor artificial corneal failure

PURPOSE

To describe the histopathologic and immunologic characteristics of late artificial corneal failure in a small series of patients who underwent AlphaCor implantation and to elucidate the mechanisms involved.

DESIGN

Clinicopathologic case series.

METHODS

Three patients were diagnosed with corneal melting during the late postoperative period and required the removal of the devices. The explanted devices embedded within the corneal tissues were examined by light microscopy, electron microscopy, and immunohistochemical studies.

RESULTS

Light microscopic examination of the specimens disclosed adequate biointegration with no foreign body response. Immunofluorescence studies of the skirt exhibited expression of inflammatory cytokines such as interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNF-alpha), and some interferon gamma (IFN-gamma). The keratocytes stained positively for Thy-1 and smooth muscle actin but negatively for CD34.

CONCLUSIONS

Although these findings confirm the occurrence of biointegration, myofibroblastic differentiation of the ingrowing keratocytes is a prominent feature.

Early pathological features of the cornea in toxic epidermal necrolysis

AIM

To describe the early pathological changes in the cornea during toxic epidermal necrolysis (TEN).

METHOD

Demonstration of histological features of sequential corneal samples taken during management of complications of TEN in a young adult.

RESULTS

Early vacuolation of basal keratinocytes and late infiltration of the cornea with CD 8 lymphocytes were observed. These changes are similar to those found in cutaneous TEN and may represent weakening of the stromal-epithelium interface with resultant recurrent erosion and chronic inflammation.

CONCLUSIONS

Similar changes were found in avascular corneal tissue to those previously described in skin. The initial insult may be traumatic. We propose that a cytokine-mediated response contributes to the initial insult, either in response to and/or by accelerating severe inflammation. This precedes a cytotoxic infiltration which may exacerbate episodes of recurrent erosion. This provides a new insight into the mechanism of disease in the cornea following TEN.

Praktikabilität des HLA-Matchings

The unpredictability of the expected time on the waiting list has been the main barrier towards broad acceptance of human leukocyte antigen (HLA) matching in clinical routine. An algorithm for predicting the expected time on the waiting list for a histocompatible graft was recently introduced. This algorithm allows for the balancing waiting time against improvement in prognosis on an individual basis. HLAMatchmaker is a new method for identifying HLA mismatches with minor immunogenicity. This method is a valuable tool for providing patients who have a rare HLA phenotype with a histocompatible graft. In summary, new methods are now available that make histocompatibility in penetrating keratoplasty possible in almost all cases.

Typisierung beim HLA-Matching

Matching of human leukocyte antigens of donors and recipients (HLA matching) plays a significant role in kidney, heart, lung, and stem cell transplantation. New data demonstrate that HLA matching also significantly prolongs the survival of corneal grafts. The reasons for the late recognition of the significance of HLA matching in corneal transplantation are on the one hand the immune privilege of the eye, which allows corneal transplantation under certain conditions without immunosuppressive therapy, and on the other hand highly erroneous serological typing. Recent molecular DNA typing is almost without errors, and the selection of grafts on the basis of results obtained using this method will improve the long-time survival of future corneal grafts. Today, there are several reasons arguing for the general practice of HLA matching in keratoplasty.

Matching von Minor-Transplantationsantigenen in der perforierenden Keratoplastik

Specific recognition of foreign tissue is a common feature in higher vertebrates. This capability has commonly been ascribed to the human leukocyte antigen (HLA) complex. Recent developments, however, point to an outstanding role of minor H antigens, especially in the context of corneal transplantation. It is likely that the matching of selected minor H antigens will further improve rejection free, clear graft survival following penetrating keratoplasty in the not so distant future.

Immunological Characteristics of Amniotic Epithelium

We review recent experimental evidence of the immunosuppressive and immunogenic potential of amniotic epithelial cells. Since cryopreserved amniotic membrane (AM) has been used in clinical applications, much research has focused on the beneficial effects of amniotic stromal matrix rather than on the function of viable amniotic cells. However, viable human amniotic epithelial cells (HAECs) have been shown to elicit beneficial effects on secretion of anti-inflammatory factors. Topical application of culture supernatant from HAECs leads to profound suppression of suture-induced neovascularization in cornea and fewer major histocompatibility complex (MHC) class II antigen-presenting cells (APCs) in inflamed cornea after thermal cautery. Furthermore, expression of interleukin (IL)-1beta mRNA was suppressed in cauterized cornea. These results suggest that HAECs are a source of soluble anti-inflammatory factors that suppress corneal inflammation. However, viable amniotic epithelial cells display antigenicity and immunogenicity as allografts. Fresh allogeneic amniotic epithelium (AE) expresses MHC class I antigens and sensitizes recipients when placed in the eye, although long-term memory of allo-specific delayed hypersensitivity (DH) was not acquired. Allogeneic AE was clearly vulnerable to acute immune rejection in specifically sensitized recipients and recipients of repeated AE transplantation. We therefore suggest that immunogenicity of AE should not be ignored, and use of AM from different donor placentas should be emphasized when repeated AM transplantation is required in patients clinically.

Matching of the minor histocompatibility antigen HLA-A1/H-Y may improve prognosis in corneal transplantation

BACKGROUND

Minor histocompatibility (H) antigens are peptides of allelic intracellular proteins that play an important role in human leukocyte antigen (HLA) matched transplantations. In an animal model of keratoplasty, minor H antigens have even been reported to exceed the immunogenicity of major H antigens (MHC). This investigation is to assess any benefit of matching the broadly expressed gender (H-Y) and HA-3 antigens in HLA-A1 donor positive human keratoplasty.

METHODS

A total of 229 HLA-A1 donor positive keratoplasties were analyzed. A Cox proportional hazards model and Kaplan-Meier analysis were applied to estimate the effect of H-Y or HA-3 mismatches on rejection-free graft survival.

RESULTS

Eighty-one cases were mismatched for H-Y (male donor to female recipient). A mean follow up of two years showed graft survival as high as 88% in the H-Y compatible group compared to only 77% in the H-Y mismatched group (P = 0.02). Eight out of 62 cases were mismatched for HA-3. No statistically significant influence of HA-3 matching on rejection-free graft survival was observed (85% vs. 73%, P=0.52).

CONCLUSION

HLA-A1/H-Y matching and matching for other broadly expressed minor H antigens may further improve prognosis in keratoplasty.

Changes Observed in Keratolimbal Allograft

OBJECTIVE

To study the incidence and clinical characteristics of presumed immunologic reactions in limbal grafts after keratolimbal allograft(KLAL).

METHODS

A total of 121 KLALs performed in consecutive 85 eyes of 78 patients with total limbal stem-cell deficiency were analyzed retrospectively. Mean follow-up period was 46.6 months. Three types of limbal graft changes classified as epithelial defects, acute edema, and vascular engorgement were analyzed as probable signs of immunologic rejection.

RESULTS

One or more changes in limbal grafts were observed after 16 KLALs (13.1%). All but 1 eye used systemic and local immunosuppression using corticosteroid and cyclosporine A, and most of the changes developed within 3 months postoperatively. All but 2 eyes developed epithelial breakdown in the central cornea, and 12 corneas underwent conjunctivalization. The rate of corneal epithelialization in eyes with limbal graft changes was significantly worse than those without the changes (P < 0.0001). Histologic examination in eyes with the limbal graft changes revealed high incidence of lymphocyte infiltration.

CONCLUSIONS

Presumed limbal graft rejection occurred in approximately 13% of cases after KLAL. Suppression of the immune reaction remains a key to success in KLAL.

Analysis of corneal inflammation induced by cauterisation in CCR2 and MCP-1 knockout mice

AIM

To elucidate the role of CCR2/MCP-1 in corneal inflammation.

METHODS

A cauterisation induced corneal inflammation model was used. The corneas were cauterised with silver nitrate in CCR2 knockout (KO) mice, MCP-1 KO mice, and control mice. Clinical signs such as corneal oedema and opacity were examined 96 hours after cauterisation and the phenotypes of the cells infiltrating the cornea were analysed by flow cytometry. Corneal inflammation in neutrophil depleted mice was also analysed.

RESULTS

After cauterisation both CCR2 KO and MCP-1 KO mice showed the same levels of corneal oedema and opacity as control mice. Flow cytometry revealed that in control mice most of the infiltrating cells were neutrophils and macrophages, whereas in both CCR2 KO mice and MCP-1 KO mice, the number of macrophages infiltrating the cornea were markedly reduced. However, prominent infiltrates of neutrophils were still observed in the cornea in CCR2 KO mice and MCP-1 KO mice. The depletion of neutrophils significantly reduced the oedema and opacity induced in the cornea by cauterisation.

CONCLUSION

The CCR2 and MCP-1 molecules are not essential for cauterisation induced corneal inflammation. Neutrophils, rather than migrated macrophages, are the final effector cells involved in inducing inflammation in this model.

Accelerated wound healing of alkali-burned corneas in MRL mice is associated with a reduced inflammatory signature

PURPOSE

The present study was conducted to investigate healing of alkali-burned corneas in MRL/MpJ (MRL) mice.

METHODS

Gross, clinical, and histologic criteria were used to compare healing of alkali-burned corneas in MRL and control C57BL/6J (B6) mice. Effects of neutrophil depletion of B6 mice and allogeneic reconstitution of B6 mice with MRL bone marrow on wound healing were evaluated. Gene expression patterns in normal and wounded corneas were surveyed with array-based quantitative real-time RT-PCR (AQPCR).

RESULTS

MRL mice showed accelerated reepithelialization and decreased corneal opacity compared with B6 mice after alkali wounding. Marked inflammatory cell infiltration and fibrosis were evident in the corneas and anterior chambers of B6 mice. MRL mice showed less severe lesions, except for stromal edema. Rapid reepithelialization and reduced keratitis/iritis were also observed in neutrophil-depleted B6 mice, but not in B6 mice reconstituted with MRL bone marrow. AQPCR showed transcriptional changes of fewer genes associated with inflammation and corneal tissue homeostasis in alkali-burned corneas from MRL mice. Increased expression of an anti-inflammatory gene, Socs1, and a gene associated with healing, Mmp1a, were evident in MRL corneas.

CONCLUSIONS

Alkali-burned corneas heal faster and more completely in MRL mice than in B6 mice, by means of rapid reepithelialization, reduced inflammation, and reduced fibrosis. Reduced inflammation, including decreased neutrophil infiltrates and the lack of a robust proinflammatory gene expression signature correlates with the rapid healing. However, the rapid-healing phenotype is not intrinsic to MRL hematopoietic progenitor cells.

Mucous membrane pemphigoid: an update

PURPOSE OF REVIEW

To review articles on mucous membrane pemphigoid, published between June 2004-May 2005.

RECENT FINDINGS

Decreased glycosylation of mucin was found in patients with ocular cicatricial pemphigoid. A unique antigen in oral mucous membrane pemphigoid has not yet been identified. Increased vascular cell adhesion molecule and intercellular adhesion molecule 1 expression was found in skin of patients affected by mucous membrane pemphigoid. Autoreactive T cells to an epitope of bullous pemphigoid antigen 180 kilodaltons were identified in the blood of some patients with mucous membrane pemphigoid. Circulating IgA against an antigen in mucous membrane pemphigoid was found in about 20% of patients, without prognostic significance. Enhanced sensitivity for direct immunofluorescence was reported if skin biopsy specimens were stored for 24 hours in saline. An enzyme-linked immunosorbent assay for detection of circulating autoantibodies against laminin-5 was developed. Sensitivity was higher than indirect immunofluorescence on salt-split skin and immunoblotting. Patients with younger onset (<60 years) of ocular cicatricial pemphigoid were found to have disease evolution similar to that of an older group (>70 years) but were visually impaired earlier in life. Intravenous immunoglobulin as treatment of ocular cicatricial pemphigoid was found to be superior to conventional immunosuppressants, with fewer side effects and better long-term outcome for halting disease activity. Intraoperative adjunction of mitomycin C during fornix reconstruction with amniotic membrane resulted in achieving a deeper fornix in 83% of patients with various cicatrizing conjunctivitis. Transplantation of cultured epithelial cells of oral mucosa in corneal limbal stem cell deficiency was successful in improving visual acuity and reestablishing corneal transparency in mid- to advanced ocular cicatricial pemphigoid.

SUMMARY

Further advances have been achieved in the field of mucous membrane pemphigoid.

[Clinical study on the endothelial immune rejection after penetrating keratoplasty]

OBJECTIVE

To study the relationship between the grafts transparency and the endothelial immune rejection at different periods after penetrating keratoplasty (PKP).

METHODS

A following-up was performed on patients received PKP in Shandong Eye Institute and Hospital between January 1994 and December 1998. A total of 648 cases (648 eyes) were involved in this study, including 444 males (444 eyes) and 204 females (204 eyes). The incidence of endothelial immune rejection and grafts opacification at the time point of 0.5, 1, 3, 6, 9, 12, 18, 24, 36 and 48 months postoperatively was collected. We made two curves to study the relationship between transparence of grafts and endothelial rejection. Relationship between the endothelial immune rejection and the types of corneal diseases before the operation was also analyzed.

RESULTS

There was a significant relationship between grafts opacification and the endothelial immune rejection (linear regression and simple correlation, P < 0.01). The rate of rejection decreased after 3 years postoperatively. Inflammatory background was an important factor for the occurrence of endothelial immune rejection and graft opacification.

CONCLUSIONS

After PKP, endothelial immune rejection is the critical factor for affecting the grafts transparency. Long-term follow-up of the patients is important for the maintaining of transparency of grafts and to obtain a successful result of the operation.

Involvement of CD8+ T-cells in exacerbation of corneal scarring in mice

PURPOSE

To determine the specific immune responses involved in the exacerbation of corneal scarring induced by HSV-1 in gK vaccinated mice.

MATERIALS AND METHODS

BALB/c mice were vaccinated with HSV-1 glycoprotein K (gK) and ocularly challenged with HSV-1. Infiltration into the cornea of T cells and macrophages was monitored by immunocytochemistry, and the effect of depletion of CD4+ T-cells, CD8+ T-cells, or macrophages on corneal scarring was determined.

RESULTS

Following ocular challenge, CD4+ and CD8+ T-cells and macrophages were more abundant in the corneas of gK-vaccinated mice than in the corneas of mock vaccinated mice. Depletion of CD8+ T-cells, but not of CD4+ T-cells or macrophages, reduced the severity of corneal scarring in gK-vaccinated mice.

CONCLUSIONS

We have shown that gK vaccination causes an overall increase in T cells and macrophages in the cornea after ocular HSV-1 challenge. The immunopathology induced by gK vaccination appears to be related to CD8+ T-cell activity, as depletion of these cells, but not other immune cells, reduced corneal scarring.

Interleukin-1alpha production in human corneal scars

We studied IL-1alpha level in corneal scars with/without neo-vascularization. A total of 27 patients underwent grafting for corneal scar. Recipients were grouped according to number of vascularized quadrants (0 to IV/IV): none (n = 12), one (n = 5), two (n = 4) and four (n = 6). Recipient corneas were collected during surgery and IL-1alpha measured by immunoassay. Controls were donor corneas unsuitable for transplantation. Graft rejection rate was calculated for each group. Mean IL-1alpha concentration in corneal scars was 6 +/- 3.93 pg/mm3; significantly higher as compared to controls (1.25 +/- 2.03 pg/mm3). IL-1alpha correlated well with amount of blood vessels, except in IV/IV scars: 5.17 +/- 3.65 pg/mm3 for 0/IV; 8.02 +/- 2.51 pg/mm3 for I/IV; 8.27 +/- 3.62 pg/mm3 for II/IV and 4.47 +/- 5.03 pg/mm3 for IV/IV corneal scars. Vascularization of corneal scar is associated with increased IL-1alpha level (in all but highly vascularized scars), indicating that IL-1alpha promotes early stages of vascularization. Graft rejection rate increases in patients with higher vascularization, independently of IL-1alpha level.

Immunotactoid keratopathy: a clinicopathologic case report and a review of reports of corneal involvement in systemic paraproteinemias

Corneal deposits in association with paraproteinemias have been well described in the ophthalmic literature. Recent reports in the renal literature have described immunotactoid deposition associated with glomerulopathy-organized microtubular deposits of IgGkappa that measured 32-50 nm in diameter on renal biopsies. We present a case of corneal immunotactoid deposition in the setting of chronic lymphocytic leukemia and review previous reports of corneal deposition in the setting of systemic paraproteinemia, highlighting the etiology, differential diagnosis, prognosis, and treatment of corneal involvement. We propose the use of the term immunotactoid keratopathy to describe corneal IgGkappa deposits appearing as tubular, electron-dense, crystalloid deposits with a central lucent core on electron microscopy and suggest that these patients undergo directed systemic workup to evaluate for potential etiologies of their systemic paraproteinemia. To illustrate the spectrum of paraprotein deposition in the cornea, and to emphasize the importance of ophthalmic evaluation in the setting of systemic paraproteinemias, we include a case of a 44-year-old man with immunoprotein corneal deposition who was subsequently diagnosed with multiple myeloma.

Erfolgreiche Therapie des IgA-Pemphigus vom subkorneal pustul�sen Typ

IgA pemphigus is a rare autoimmune intraepidermal blistering disease characterized by in vivo bound, and circulating IgA autoantibodies that target cell surface components (cadherins) of epidermal keratinocytes. The average age of onset is approximately 50 years. Histological hallmarks of IgA pemphigus are epidermal acantholysis, subcorneal or intraepidermal pustulosis, and neutrophilic infiltration. The main clinical characteristics are erythematous skin lesions with vesiculopustules, erosions, crusts and desquamation, favoring the trunk, groins, auxiliaries, and proximal extremities. The drug of choice for treating IgA pemphigus is diaminodiphenylsulfone. In this case study, we describe a patient who suffered from IgA pemphigus and responded well to diaminodiphenylsulfone.

Expression of HLA-G in human cornea, an immune-privileged tissue

Human leukocyte antigen (HLA)-G retains the capacity to modulate immune responses, favoring the establishment of tolerance in solid-tissue allotransplants. To better understand the mechanisms that promote corneal allograft survival, we investigated whether HLA-G was an immunoregulatory factor involved in corneal immunology. We therefore sought HLA-G expression in corneal tissues. Corneal transplantation consists in replacing the center of a diseased cornea with normal corneal tissue. Two corneal parts are not used in such surgery: diseased central corneal tissue and peripheral normal cornea. For this study, we used healthy corneas obtained from deceased donors and diseased corneas obtained from patients with pseudophakic bullous keratopathy or keratoconus who had undergone corneal transplantation. Immunohistochemical analysis carried out on the cryopreserved corneas showed a positive immunohistochemical staining with anti-HLA-G, anti-HLA-A, -B, and -C, and anti-HLA class I monoclonal antibodies. Staining was obtained for keratocytes, epithelial cells, and endothelial cells from both healthy and pathologic human corneas, revealing the presence of HLA class I proteins, including HLA-G. HLA-G transcripts were detected in normal cornea by reverse transcriptase-polymerase chain reaction with a classical pattern of alternative splicing. The detection of HLA-G protein in adult corneas leads to the conclusion that this protein may contribute to the maintenance of the privileged immune status of cornea.

CD8(+) T cells control corneal disease following ocular infection with herpes simplex virus type 1

The role that T cell subsets play in herpetic stromal keratitis (HSK) has been the subject of intense research efforts. While most studies implicate CD4(+) T cells as the principal cell type mediating primary corneal disease, recent reports using knockout mice have suggested that both CD4(+) and CD8(+) T cell subsets may play integral roles in modulating the disease. Furthermore, recent studies suggest that CD8(+) T cells are directly involved in maintaining virus latency in infected trigeminal ganglia. This work has addressed these discrepancies by infecting the corneas of mice lacking CD4(+) and CD8(+) T cells with herpes simplex virus type 1 (HSV-1) and monitoring both corneal disease and latent infection of trigeminal ganglia. Results indicated that mice lacking CD8(+) T cells had more severe corneal disease than either BALB/c or B6 parental strains. In contrast, mice lacking CD4(+) T cells had a milder disease than parental strains. When mice were evaluated for persistence of infectious virus, only transient differences were observed in periocular tissue and corneas. No significant differences were found in persistence of virus in trigeminal ganglia or virus reactivation from explanted ganglia. These data support the following conclusions. CD4(+) T cells are not required for resistance to infection with HSV-1 and probably mediate HSK. Mice lacking CD8(+) T cells do not display differences in viral loads or reactivation and thus CD8(+) T cells are not absolutely required to maintain latency. Finally, CD8(+) T cells probably play a protective role by regulating the immunopathological response that mediates HSK.

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.

Absence of tumour necrosis factor facilitates primary and recurrent herpes simplex virus-1 infections

Tumour necrosis factor (TNF) is an important cytokine in the innate immune response against various infections, including herpes simplex virus (HSV) infection. It has recently become a molecular target of anti-cytokine treatment in certain inflammatory diseases. TNF depletion resulted in a more rapid emergence of infectious HSV-1 in the explant cultures of latently infected trigeminal ganglia (TG), compared with controls. To further evaluate the importance of TNF in the host's defence responses against HSV-1, TNF-knockout mice were challenged via scarified cornea. These mice were more susceptible to primary acute corneal HSV-1 infection than controls, as manifested by an increased mortality rate and higher infectious virus titres in the eyes and TG, indicating that TNF is critical for defence during acute HSV infection. These results imply that the administration of anti-inflammatory TNF antagonists might facilitate the propagation of infectious HSV, resulting in an exacerbation of primary and recurrent acute lesions.

HSV-1 antigens and DNA in the corneal explant buttons of patients with non-herpetic or clinically atypical herpetic stromal keratitis

BACKGROUND

Little is known about the role of HSV-1 in keratitis not primarily attributed to herpetic origin. This study therefore aimed to prospectively evaluate the corneal explant buttons of patients with non-herpetic or clinically atypical herpetic stromal keratitis (experimental group: non-HSK) for the presence of HSV-1 antigens and DNA, and to compare the findings with those from individuals with typical herpetic stromal keratitis (positive control group: HSK) or non-inflammatory degenerative keratopathy (negative control group).

METHODS

Corneal buttons derived from 51 patients with HSK, from 72 with non-HSK and from 30 with degenerative keratopathy were prospectively collected and subjected to immunohistochemical analysis for HSV-1 antigens and to HSV-1 DNA amplification.

RESULTS

In corneal buttons derived from patients with non-HSK, viral antigens were detected immunohistochemically in 8/72 cases and DNA amplified in 16/72. Corresponding values for the HSK group were 16/51 and 11/51. Taking viral antigen and DNA findings together, HSV-1 was detected in 18/72 (25%) patients with non-HSK and in 19/51 (37%) with HSK (p=0.2), but in only 2/30 (6%) individuals with non-inflammatory degenerative keratopathy.

CONCLUSION

Since the detection frequencies for HSV-1 antigens and DNA were comparable in the HSK and non-HSK groups, Herpes may play an underestimated and as yet undefined role in non-herpetic and clinically atypical herpetic stromal keratitis, either as a primary trigger of the disease or as a secondary contributor to it. In this category of individuals, early anti-herpetic therapy should be considered if patients do not respond in the expected manner to treatment for non-herpetic stromal keratitis.

Corneal lymphangiogenesis: evidence, mechanisms, and implications for corneal transplant immunology

PURPOSE

The normal cornea is devoid of blood and lymphatic vessels but can become vascularized secondary to a variety of corneal diseases and surgical manipulations. Whereas corneal (hem)angiogenesis, i.e., the outgrowth of new blood vessels from preexisting limbal vessels, is obvious both clinically and histologically, proof of associated corneal lymphangiogenesis has long been hampered by invisibility and lack of specific markers. This has changed with the recent discovery of the lymphatic endothelial markers vascular endothelial growth factor receptor 3, LYVE-1 (a lymphatic endothelium-specific hyaluronan receptor), Prox 1, and Podoplanin.

METHODS

We herein summarize the current evidence for lymphangiogenesis in the cornea and describe its molecular markers and mediators. Furthermore, the pathophysiologic implications of corneal lymphangiogenesis for corneal transplant immunology are discussed.

RESULTS

Whereas corneal angiogenesis in vascularized high-risk beds provides a route of entry for immune effector cells to the graft, lymphangiogenesis enables the exit of antigen-presenting cells and antigenic material from the graft to regional lymph nodes, thus inducing alloimmunization and subsequent graft rejection.

CONCLUSIONS

Antilymphangiogenic strategies may improve transplant survival both in the high- and low-risk setting of corneal transplantation.

CD4(+) and CD8(+) cells are key participants in the development of recurrent herpetic stromal keratitis in mice

Ocular herpes simplex virus (HSV) infection results in an immune-mediated inflammation of the corneal stroma known as herpetic stromal keratitis (HSK). Recurrent HSK is a common cause of virus-induced corneal blindness in humans. The role of CD4(+) and CD8(+) T cell subsets in the disease pathogenesis is ill defined and varies with the virus strain and host genetic background. To examine the contribution of T cell subsets to corneal disease, we studied the development of recurrent HSK in CD4 or CD8 gene knockout (KO) mice ocularly infected with HSV-1 McKrae strain. Following UV-B induced viral reactivation, corneal opacity in latently infected BALB/c (HSV sensitive) CD4 and CD8 KO mice was reduced compared to infected BALB/c mice with normal genotype. In contrast, opacity in C57BL/6 (HSV resistant) CD4 and CD8 KO latent mice did not differ from genetically normal latent mice. Virus-induced corneal opacity was not demonstrable in C57BL/6 CD4/CD8 double KO mice. Increased viral shedding, measured by reactivation rate, days shedding or viral titers, occurred in CD4 KO mice of both strains. Our findings indicate that both CD4(+) and CD8(+) cells play a role in the immunopathogenesis of recurrent HSK, and their role is dependent upon the host genetic profile.

Serovar distribution of a DNA sequence involved in the antigenic relationship between Leptospira and equine cornea

BACKGROUND

Horses infected with Leptospira present several clinical disorders, one of them being recurrent uveitis. A common endpoint of equine recurrent uveitis is blindness. Serovar pomona has often been incriminated, although others have also been reported. An antigenic relationship between this bacterium and equine cornea has been described in previous studies. A leptospiral DNA fragment that encodes cross-reacting epitopes was previously cloned and expressed in Escherichia coli.

RESULTS

A region of that DNA fragment was subcloned and sequenced. Samples of leptospiral DNA from several sources were analysed by PCR with two primer pairs designed to amplify that region. Reference strains from serovars canicola, icterohaemorrhagiae, pomona, pyrogenes, wolffi, bataviae, sentot, hebdomadis and hardjo rendered products of the expected sizes with both pairs of primers. The specific DNA region was also amplified from isolates from Argentina belonging to serogroups Canicola and Pomona. Both L. biflexa serovar patoc and L. borgpetersenii serovar tarassovi rendered a negative result.

CONCLUSIONS

The DNA sequence related to the antigen mimicry with equine cornea was not exclusively found in serovar pomona as it was also detected in several strains of Leptospira belonging to different serovars. The results obtained with L. biflexa serovar patoc strain Patoc I and L. borgpetersenii serovar tarassovi strain Perepelicin suggest that this sequence is not present in these strains, which belong to different genomospecies than those which gave positive results. This is an interesting finding since L. biflexa comprises nonpathogenic strains and serovar tarassovi has not been associated clinically with equine uveitis.

MIP-1alpha regulates CD4+ T cell chemotaxis and indirectly enhances PMN persistence in Pseudomonas aeruginosa corneal infection

The role of macrophage inflammatory protein-1alpha (MIP-1alpha) in cell infiltration into Pseudomonas aeruginosa-infected cornea and subsequent disease was examined. Greater amounts of the chemokine (protein and mRNA) were found in the infected cornea of susceptible B6 ("cornea perforates") versus resistant BALB/c ("cornea heals") mice from 1 to 5 days postinfection. Treatment of BALB/c mice with recombinant (r) MIP-1alpha exacerbated disease and was associated with an increased number of neutrophils (PMNs) in the cornea. Treatment of BALB/c mice with rMIP-1alpha also induced recruitment of activated CD4+ T cells into the affected cornea, converting resistant to susceptible mice. Depleting CD4+ T cells in r-treated BALB/c mice significantly decreased PMNs in cornea tissue, suggesting that T cells regulate persistence of PMNs at this site. In B6 mice, administration of neutralizing MIP-1alpha polyclonal antibody also significantly reduced PMN numbers and pathology. Collectively, evidence is provided that MIP-1alpha directly contributed to CD4+ T cell recruitment and indirectly to PMN persistence in the infected cornea.

[Bee sting of the cornea - a case report]

BACKGROUND

Bee stings of the cornea are very rare, though its response can range from minimal inflammation to severe damage like lens dislocation, cataract formation, iris atrophy, ophthalmoplegia and optic neuropathy. We report on a patient with typical, severe findings.

PATIENT

A 42-year-old patient presented with an acute, corneal bee sting of the left eye, after he was stung only a few hours ago. The patient suffered from pain, blurred vision and epiphora. The left eye showed edema of the upper and lower eyelid, conjunctival hyperemia, chemosis, striate keratitis, a purulent infiltration of the cornea above the limbus at the 7 o'clock meridian and a massive hypopyon. Further examinations showed regular ophthalmological findings. Vision acuity was 1,0/0,4. Under therapy inflammation decreased quickly. One week after we could lokalize the stinger in the depth of the corneal infiltration and it was removed surgically. After one month the eye only showed a minimal infiltration of the cornea with fine neovascularisations. Visual acuity was 0,8.

CONCLUSION

Clinical reactions to bee stings of the cornea are caused by toxical and immunological effects of different components of the bee venom. These toxical and/or inflammatory reactions can lead to severe intraocular damage. Treatment of choice is the systemic and local application of steroids and antibiotics as well as local therapy with antihistamins.

Effects of exogenous interleukin-6 during Pseudomonas aeruginosa corneal infection

Lack of interleukin-6 (IL-6) during Pseudomonas aeruginosa corneal infection leads to more severe disease with changes in neutrophil recruitment. Exogenous IL-6 leads to increased efficiency of neutrophil recruitment and reduced bacterial loads in corneal infection in both IL-6 gene knockout and wild-type mice. This may be mediated by IL-6 increasing the production of corneal macrophage inflammatory protein 2 and intercellular cell adhesion molecule 1. We conclude that effective recruitment of neutrophils into the cornea is dependent on the production of IL-6 and that early augmentation of IL-6 may be protective in corneal infection.

Antiinflammatory effects of amniotic membrane transplantation in ocular surface disorders

PURPOSE

To determine whether the sequestration of inflammatory cells plays a role in the antiinflammatory effects of amniotic membrane transplantation to the ocular surface.

METHODS

Amniotic membrane grafts were prepared from placental tissue procured from mothers undergoing planned Cesarean sections. A detailed explanation was given to all donors, and a written consent was obtained before processing. Amniotic membrane tissue was dissected into 3- x 3-cm segments, rinsed in phosphate buffered saline, and stored in dimethyl sulfoxide solutions at -80 degrees C until use. In a clinical series, amniotic membrane patches of the ocular surface were performed in 20 eyes of 20 patients with persistent corneal epithelial defects, or as a prophylactic measure after corneal limbal transplantation. Amniotic membrane patches were harvested after a 1-week observation period and were subjected to histopathologic examinations by hematoxylin and eosin staining. Inflammatory cells trapped within the amniotic membrane were labeled by immunocytochemistry using anti-CD14, CD4, CD8, and CD20 antibodies. TUNEL (TdT-mediated dUTP nick end labeling) staining was done to observe cells undergoing apoptosis. The T cell line Molt 4 was co-cultured with amniotic membrane in vitro to observe adhesion of T cells to amniotic membrane.

RESULTS

Various degrees of inflammatory cell infiltration were observed in all clinical samples of amniotic membrane patches. Most of the inflammatory cells stained positively with anti-CD14 antibodies, indicating that these cells were of monocyte/macrophage lineage. Subsets of T cells included both CD4(+) and CD8(+) cells, whereas CD20(+) cells were sparse. TUNEL assays revealed that trapped inflammatory cells exhibited characteristics of cells undergoing apoptosis. Molt 4 invaded within amniotic membrane in an in vitro assay, which was not inhibited by blocking antibodies to beta1 and beta2 integrins.

CONCLUSION

Amniotic membrane attracts and traps inflammatory cells infiltrating the ocular surface, which may explain some of the antiinflammatory properties of the fetal tissue.

Immune-mediated corneal melting disease

Corneal melting disease is, as illustrated, a very severe problem for patients. Correct diagnosis and aggressive management is critical. Help from general physicians and rheumatologists as required is essential, given that the medications used have significant toxic effects.

The role of cytokines in corneal immunopathology

Cytokines play an important role in the pathogenesis of various corneal diseases and during corneal graft rejection. Furthermore, cytokines may also play a role in the maintenance of the integrity of the normal cornea. This review focuses on the effects of several cytokines in corneal immunopathology, including the type of the corneal immune response, angiogenesis, chemotaxis, apoptosis, wound healing, corneal disease, and transplantation. It may provide clues for the future treatment of corneal disease and corneal transplantation rejection.

B7/CD28 costimulation is critical in susceptibility to Pseudomonas aeruginosa corneal infection: a comparative study using monoclonal antibody blockade and CD28-deficient mice

Evidence suggests that Pseudomonas aeruginosa stromal keratitis and corneal perforation (susceptibility) is a CD4(+) T cell-regulated inflammatory response following experimental P. aeruginosa infection. This study examined the role of Langerhans cells (LC) and the B7/CD28 costimulatory pathway in P. aeruginosa-infected cornea and the contribution of costimulatory signaling by this pathway to disease pathology. After bacterial challenge, the number of LC infiltrating the central cornea was compared in susceptible C57BL/6 (B6) vs resistant (cornea heals) BALB/c mice. LC were more numerous at 1 and 6 days postinfection (p.i.), but were similar at 4 days p.i., in susceptible vs resistant mice. Mature, B7 positive-stained LC in the cornea and pseudomonas Ag-associated LC in draining cervical lymph nodes also were increased significantly p.i. in susceptible mice. To test the relevance of these data, B6 mice were treated systemically and subconjunctivally with neutralizing B7 (B7-1/B7-2) mAbs. Treatment decreased corneal disease severity and reduced significantly the number of B7-positive cells as well as the recruitment and activation of CD4(+) T cells in the cornea. IFN-gamma mRNA levels also were decreased significantly in the cornea and in draining cervical lymph nodes of mAb-treated mice. When CD28(-/-) animals were tested, they exhibited a less severe disease response (no corneal perforation) than wild-type B6 mice and had a significantly lower delayed-type hypersensitivity response to heat-killed pseudomonas Ag. These results support a critical role for B7/CD28 costimulation in susceptibility to P. aeruginosa ocular infection.

Autocrine action of IL-10 suppresses proinflammatory mediators and inflammation in the HSV-1-infected cornea

We investigated whether IL-10 produced endogenously would influence the development of HSV-1-induced acute corneal disease. Murine corneal epithelial cells and fibroblasts cultured in vitro expressed IL-10 mRNA and protein constitutively and also IL-10 receptors. Inclusion of IL-10 neutralizing antibody in the culture medium significantly (p<0.05) enhanced TNF-alpha-induced IL-6 and MIP-2 production by both corneal cell types. Endogenous IL-10 synthesis, which also occurred in vivo, was not modulated by Herpes virus infection or by depletion of neutrophils or natural killer cells. Antibody to IL-10 given locally at the time of HSV-1 intracorneal infection was associated with significantly (p<0.05) enhanced production of IL-6, MIP-2, and MIP-1alpha, increased neutrophil infiltration, and more extensive corneal disease. Similarly, mice with a disrupted IL-10 gene developed more severe corneal disease than wild-type controls. Collectively, these observations suggest that locally produced IL-10 can act in an autocrine/paracrine fashion to down-regulate the production of proinflammatory mediators and thus limit corneal inflammation.

Immune mechanisms in Onchocerca volvulus-mediated corneal disease (river blindness)

Infection with the parasitic nematode Onchocerca volvulus can lead to severe visual impairment and blindness. In an effort to characterize the molecular basis for the inflammatory response in the cornea, we have developed a murine model for O. volvulus-mediated keratitis in which parasite antigens are injected into the corneal stroma of sensitized mice. This model reproduces the two main clinical features of human disease, corneal opacification and neovascularization. Histological analysis of corneas from these mice reveals a biphasic recruitment of neutrophils and eosinophils to the central cornea, along with a small, but persistent number of CD3+ cells. In this review, we present evidence that production of antigen-specific T cell and antibody responses are essential for development of O. volvulus keratitis, and we propose a sequence of molecular and cellular events that lead to migration of inflammatory cells to the cornea and to loss of corneal clarity.

TNF-alpha production in the cornea in response to Pseudomonas aeruginosa challenge

Pseudomonas aeruginosa can cause ulcerative bacterial keratitis or contact lens-induced acute red eye (CLARE) in humans. The present study used a mouse model of ocular infection and inflammation to examine the relationship between TNF-alpha and inflammation in the cornea in response to challenge with either a strain of P. aeruginosa causing keratitis or a CLARE strain. Constitutive TNF-alpha mRNA was detected in the epithelium, mainly towards the periphery. After infection with the keratitis-inducing strain (6294), TNF-alpha expression was elevated four-fold by 24 h post-challenge. No detectable induction of TNF-alpha mRNA was seen with CLARE strain (Paer1) challenge at any time point. The TNF-alpha protein production detected by ELISA showed a corresponding pattern to the mRNA expression, which also correlated with pathological changes. These results suggest that invasive strains of P. aeruginosa create greater pathological changes as a result of elevated TNF-alpha production, which contributes to inflammation during keratitis in vivo.

[Clinical and immunological studies on transplantation of total cornea with circular lamellar sclera]

OBJECTIVE

To observe the clinical results of total cornea with circular lamellar sclera transplantation (CST) and study its immunological mechanisms by animal experiments.

METHODS

109 patients with corneal transplantation were retrospectively analyzed, and according to the methods of operation they were divided into groups to compare their rate of rejection and the time of occurrence of corneal neovascularization. The methods of grouping and operation in animal experiments were similar to that in the clinical practice.

RESULTS

The time of occurrence of neovascularization and rejection of CST were later than that in the total corneal transplantation (TCT), and the postoperative rate of rejection at 3 to 6 months was obviously increased in comparison with that in the partial penetrating keratoplasty (PKP).

CONCLUSION

CST is an important method for rebuilding ocular anterior segment, and the donor limbus is active in the immunological of rejection.

Early cytokine and chemokine gene expression during Pseudomonas aeruginosa corneal infection in mice

Using a multiprobe RNase protection assay, we examined cytokine and chemokine mRNAs that were expressed after corneal infection with Pseudomonas aeruginosa in mice. Cytokines that were upregulated included interleukin-1alpha (IL-1alpha) and -1beta, IL-1 receptor antagonist, IL-6, IL-11, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, macrophage colony-stimulating factor, stem cell factor, lymphotoxin beta, transforming growth factor beta1, and tumor necrosis factor alpha. Chemokine transcripts that were upregulated included Eotaxin; gamma-interferon-inducible protein 10; monocyte chemoattractant protein 1; macrophage inflammatory proteins 1alpha, 1beta, and 2; and RANTES. Peak expression of these cytokines and chemokines was observed between 1 and 3 days after infection. These responses returned to or approached baseline preinfection levels by 7 days after ocular challenge. Identification of the various cytokines and chemokines upregulated during corneal infection provides important information relevant to unraveling the pathogenesis induced by this bacterium and provides hope that specific molecules can be targeted for therapy.

The prevalence of positive hepatitis B, hepatitis C, and HIV serology in cornea donors prescreened by medical and social history in Ontario, Canada

PURPOSE

To determine the prevalence of hepatitis B (HBV), hepatitis C (HCV), and human immunodeficiency virus (HIV) in the serum of cornea donors who had been previously screened by social and medical history by the Eye Bank of Canada, Ontario Division.

METHOD

A retrospective examination of the donor records of the Eye Bank of Canada, Ontario Division, was conducted. A total of 3,228 records were examined covering the period from May 17, 1993 to May 31, 1996.

RESULTS

The prevalence of HBV was determined to be 0.25%, HCV, 0.93%; and HIV, 0.031%.

CONCLUSION

The data revealed that despite the use of medical and social history to prescreen, a small percentage of prescreened donors test serologically positive. A comparison of the prevalence of HBV, HCV, and HIV in the prescreened cornea donors to a similarly screened cohort of blood donors over a similar time period reveals a higher prevalence in all three diseases in the cohort of cornea donors. An examination of the demographic characteristics of the population as a whole versus the three groups with confirmed serology failed to show a significant difference between the seropositive and seronegative groups. This study confirms the value and necessity of serologic prescreening of cornea donors as is currently the standard of practice.

Corneal infection with herpes simplex virus type 1 leads to autoimmune responses in rats

Lewis rats were infected by corneal scarification with HSV type 1 type strain F virus. The animals showed symptoms of infection and inflammatory infiltrates of the eye but little mortality. After one month, immune responses to viral and autoantigens were examined. It was shown that lymph node cells proliferated to the myelin antigen, proteolipoprotein, and the HSV antigen, glycoprotein D, but showed depressed responses to antigens of the eye, specifically corneal and retinal antigens. Splenic cells showed small but significant responses to antigens of the eye, indicating immune deviation similar to that previously demonstrated in ACAID, where antigen had been injected into the anterior chamber of the eye.

Monoclonal corneal gammopathy: topographic considerations

Desposition of immunoglobulins in the cornea occasionally occurs in benign and malignant lymphoproliferative conditions. A 52-year-old woman with recently discovered monoclonal gammopathy of undetermined significance (MGUS) was referred to our hospital. Slit-lamp and ultrasound biomicroscopy revealed bilateral deposits within all corneal layers. The precipitates were organized in a circle, leaving a perilimbal zone and the axial cornea clear. Light microscopy of a biopsy disclosed confluent subepithelial deposits and defects in Bowman's layer. Immunoperoxidase reaction was positive only for IgG and IgG-kappa. Transmission electron microscopy confirmed the presence of extracellular rectangular and arcuate immunoglobulin crystalloids with a 10-nm periodicity but a non-crystalline defraction pattern. A review of the literature showed that the circumferential pattern of immunoglobulin deposition is associated with short-term visual symptoms and good visual acuity. The present report supports a hypothesis of immunoglobulin deposition via the limbal arcade and contradicts the "tear theory."