Keryn Anne Williams

Factors Predictive of Corneal Graft Survival: Report from the Australian Corneal Graft Registry

Risk factors for graft failure after penetrating keratoplasty were investigated in 961 patients from records collected prospectively by the Australian Corneal Graft Registry. The most common cause of graft failure was irreversible rejection. A multivariate proportional hazards regression analysis indicated that the key predictors of graft failure were: an indication for graft other than keratoconus or corneal dystrophy; a failed previous graft (ipsilateral eye); aphakia; inflammation at the time of graft; presence of an anterior chamber or iris-clip intraocular lens; graft size outside the range of 7.0 to 7.9 mm diameter; and corneal vascularization occurring in the postoperative period.

How successful is corneal transplantation? A report from the Australian Corneal Graft Register.

Corneal graft outcome was assessed within a large, prospectively collected database of 4499 records. Penetrating corneal graft survival was 91% at 1 year, 72% at 5 years and 69% at 7 years. The three most common indications for graft were keratoconus (30%), bullous keratopathy (25%) and failed previous graft (18%); the three most common causes of graft failure were rejection (34%), infection (18%) and glaucoma (9%). The vast majority of grafts were performed for improved visual acuity. About four-fifths of recipients achieved at least one line of better acuity on the Snellen chart post-operatively; of the remainder with unchanged or worse acuity, only 21% had failed grafts. Overall, 43% of recipients achieved a best corrected Snellen acuity of 6/12 or better, 52% achieved 6/18 or better, and 20% had acuitities of less than 6/60. Reasons for poor post-operative acuity (recorded as less than 6/60) included graft failure (41%) and co-morbidities in the grafted eye (43%). A number of risk factors for graft failure were examined: in most instances, there was little room for decision-making or expert intervention.

How effective is penetrating corneal transplantation? Factors influencing long-term outcome in multivariate analysis

Background. In a large patient cohort, we investigated long-term corneal graft outcome, risk factors for graft failure, and whether corneal graft survival had improved over time. Methods. Records of 10,952 full-thickness corneal grafts with associated archival follow-up were examined within a prospectively-maintained, national database of 13,831 records, with follow-up extending for up to 18 years. Kaplan-Meier survival analysis was used to indicate variables of interest for Cox proportional hazards regression analysis. A model clustered by individual patient to control for inter-eye or inter-graft dependence was constructed to identify variables best predicting penetrating corneal graft failure. Results. Probability of corneal graft survival was 0.86 at 1 year, 0.73 at 5 years, 0.62 at 10 years, and 0.55 at 15 years. Graft survival did not improve over a 15-year timeframe. Variables predicting graft failure in multivariate analysis included transplant centre, donor age, preoperative diagnosis, number of previous ipsilateral grafts, lens status, history of corneal neovascularisation, ocular inflammation or raised intraocular pressure in the grafted eye, requirement for anterior vitrectomy, graft size, early suture removal, postoperative events including graft neovascularisation, rise in intraocular pressure, and rejection episodes, type of treatment for raised intraocular pressure, and arrangements for recipient follow-up. A further 11 variables showing a significant influence on graft survival in univariate analysis were not included in the final Cox model. Conclusion. The long-term results of corneal transplantation are no better than for other forms of transplantation and have shown no measurable improvement over the past 15 years.

DISTRIBUTION AND QUANTITATION OF HLA-ABC AND DR (Ia) ANTIGENS ON HUMAN KIDNEY AND OTHER TISSUES

A quantitative estimation of the amounts of human Ia (HLA-DR) and HLA-ABC antigen on a variety of human tissues was performed. Monoclonal antibodies to species-common determinants of HLA-DR and HLA-ABC antigens were absorbed quantitatively with tissue homogenates and cell suspensions, and reassayed for residual activity in a radioimmunobinding assay. Kidney was found to carry 90% as much HLA-DR and 14% as much HLA-ABC antigen as spleen, while liver contained 19 and 9% as much, respectively. Small amounts of both antigens were found on heart; brain carried very little HLA-ABC and virtually no DR. Neither HLA-ABC nor DR was found on erythrocytes or reticulocytes. Of interest was our finding that a small subpopulation of thymocytes (10%) was HLA-DR positive. Platelets contained approximately 5% of the amount of HLA-ABC as spleen and undetectable quantities of HLA-DR, as expected. Chronic lymphatic leukemia (CLL) cells were found to carry 10% as much HLA-ABC and 33% as much DR antigen as spleen, while the values for bone marrow were 15 and 2%, respectively.

Prolongation of sheep corneal allograft survival by ex vivo transfer of the gene encoding interleukin-10.

Background. Modification of a donor cornea by gene therapy ex vivo has potential to modulate irreversible rejection, the major cause of corneal graft failure. Our aim was to transfer the gene encoding mammalian IL-10 to ovine donor corneas and to determine subsequent orthotopic corneal allograft survival in an outbred sheep model. Methods. The replicative capacity of ovine corneal endothelium was determined by autoradiography after deliberate injury. A replication-defective adenovirus was used to deliver the lacZ reporter gene to ovine corneas and transfected corneas were organ-cultured in vitro to allow transfection efficiency, duration of reporter gene expression, and toxicity attributable to the vector to be determined. A cDNA encoding full-length ovine IL-10 was cloned into an adenoviral vector that was used to transfect donor corneas ex vivo before transplantation. Orthotopic penetrating corneal transplantation was performed in outbred sheep. Results. Sheep corneal endothelium was found to be essentially amitotic. Transfection of >70% corneal endothelial cells was achieved with the viral vector and expression was maintained for 28 days in vitro. IL-10 mRNA was detectable in transfected, organ-cultured corneas for 21 days in vitro. Donor corneas transfected with cDNA encoding IL-10 showed significantly prolonged survival after penetrating keratoplasty (median 55 days, range 19 ⩾300 days) compared with control corneas (median 20.5 days, range 18–32 days, P =0.011). Conclusion. Local gene therapy-mediated expression of the immunomodulatory cytokine IL-10 has the potential to reduce the incidence of corneal graft rejection and to prolong corneal allograft survival.

LOCALIZATION OF HLA-ABC AND DR ANTIGENS IN HUMAN KIDNEY

Monoclonal antibodies to human monomorphic class I and class II major histocompatibility complex (MHC) determinants have been used with immunofluorescence and immunoperoxidase techniques, to localize these antigens in normal human kidneys. HLA-DR antigen was located in the glomeruli (probably on endothelium as well as in the mesangium) and within the cells of cortical and medullary tubules. Dendritic cells in the renal inter-stitium stained brightly for the DR antigen and could be distinguished from the staining of capillary endothelium. The vascular endothelium of large vessels stained less densely for the HLA-DR antigen than for HLA-ABC antigens. The glomeruli stained intensely for the HLA-ABC antigens and diffuse staining of HLA-ABC antigens was also noted within renal tubular cells.

Risk factors for human corneal graft failure within the Australian corneal graft registry.

Background. Our aims were to examine graft survival and visual outcome after full-thickness corneal transplantation. Methods. Records of 18,686 penetrating corneal grafts, 14,622 with archival follow-up from 1 to 22 years, were examined within a national database. Kaplan-Meier survival analysis indicated variables of interest for Cox proportional hazards regression analysis. A model clustered by patient to control intereye or intergraft dependence was constructed to identify variables best predicting penetrating corneal graft failure. Visual acuity in the grafted eye was measured by Snellen acuity. Results. Probability of corneal graft survival was 0.87, 0.73, 0.60, and 0.46 at 1, 5, 10, and 15 years, respectively. Reasons for graft failure included irreversible rejection (34%), corneal endothelial cell failure including cases of glaucoma (24%), and infection (14%). Variables predicting graft failure in multivariate analysis included transplant center, location and volume of surgeon’s case-load, graft era, indication for graft, number of previous ipsilateral grafts, lens status, corneal neovascularization at transplantation, a history of ocular inflammation or raised intraocular pressure, graft diameter, and postoperative events including graft neovascularization and rejection. Best-corrected Snellen acuity of 6/12 or better was achieved by 45%, and of less than 6/60 by 26%, of grafted eyes at last follow-up. Conclusions. The short-term survival of penetrating corneal transplants is excellent, but the eventual attrition rate appears inexorable and many factors that influence graft survival significantly are not amenable to change. Most penetrating grafts are performed for visual improvement, and excellent acuity will be achieved by approximately half of all grafts.

BASIC PATHOGENIC MECHANISMS OPERATING IN EXPERIMENTAL MODELS OF ACUTE ANTERIOR UVEITIS

Acute anterior uveitis is a recurrent inflammatory disease of the eye that occurs commonly, is distressing for the patient, and may have potentially blinding sequelae. The pathogenesis of the disease is poorly understood, and anti‐inflammatory treatment is consequently non‐specific and may be associated with significant complications. Animal models are a possible key to a better understanding of this disease. In one model, rats and mice develop a relatively short‐lived anterior uveal inflammation almost immediately after systemic injection of bacterial endotoxin. Accumulating evidence suggests that cytokine production by resident uveal macrophages initiates endotoxin‐induced uveitis which is characterized by an infiltration of neutrophils and mononuclear cells. A second model displays features in keeping with a delayed‐type hypersensitivity immune response. Experimental melanin‐induced uveitis is an acute recurrent uveitis with delayed onset but extended duration, observed when rats are immunized with bovine ocular melanin. Both animal models have clinical features in common with acute anterior uveitis, although experimental melanin‐induced uveitis appears to mimic the human disease more closely. Novel treatment options to target implicated inflammatory cells and molecules are currently under consideration.

Long-term Outcome after Corneal Transplantation: Visual Result and Patient Perception of Success

Snellen acuity, reading line, and keratometry were measured in a cohort of 60 patients at 2 or more years after penetrating keratoplasty was performed. Patients were asked to complete a questionnaire to elicit information on their perceptions of visual function and the success of the procedure. Using preferred correction, a Snellen acuity of 6/18 or better was achieved by 65%, and a reading line of N8 or better was achieved by 57% of index grafts. Thirty-eight percent had more than 5 diopters (D) of astigmatism in the graft. Approximately 75% of patients reported satisfaction with their graft (satisfaction being associated with better acuity in the grafted eye than the other eye), graft clarity, and a perceived improvement in lifestyle. Dissatisfaction appeared to be associated with graft failure and problems with contact lens wear. The findings have implications for patient selection for corneal transplantation and for the measurement of outcome.

Studies on the immunosuppressive properties of cyclosporin a in rats receiving renal allografts.

The immunosuppressive effects of cyclosporin A were tested in a DA (RT-1a) to Lewis (RT-11) rat renal allograft model, which represents a very strong histocompatibility barrier. Dose-response studies established that oral doses of 5 mg/kg/day or higher gave complete suppression of rejection, while oral doses of 2 mg/kg/day or lower were without effect. Intravenous administration of the drug approximately doubled its potency. Time studies showed that the period of administration was also critical, with a 7− or 14-day treatment course with 5 mg/kg/day orally giving prolonged graft survival, while a 4-day course was without effect. Large doses (up to 25 mg/kg/day orally) from day 4 after transplantation did not prolong graft survival, suggesting that cyclosporin A has no effect on an established rejection response. It was found that the lymphocytotoxin response to the graft was markedly suppressed by doses of cyclosporin A which maintained normal graft function, while lower doses had little or no effect on the lymphocytotoxin response. A cell-mediated immunity assay showed a substantial response, but one that was lower in amplitude from that of control animals. Histological study of 7th day allograft biopsies demonstrated essentially normal kidneys, except for a mild mononuclear cell infiltrate, at higher doses of cyclosporin. Lower doses of cyclosporin gave a picture of rejection no different from that seen in untreated controls. The LD50 of cyclosporin was found to lie between 50 and 100 mg/kg/day orally. Even the higher of these doses did not cause nephrotoxicity as determined biochemically and histologically.