Long-term outcome in corneal allotransplantation☆

As many patients with severe corneal disease are not even considered as candidates for a human graft due to their high risk of rejection, it is essential to find ways to reduce the chance of rejection. One of the options is proper matching of the cornea donor and recipient for the Human Leukocyte Antigens (HLA), a subject of much debate. Currently, patients receiving their first corneal allograft are hardly ever matched for HLA and even patients undergoing a regraft usually do not receive an HLA-matched graft. While anterior and posterior lamellar grafts are not immune to rejection, they are usually performed in low risk, non-vascularized cases. These are the cases in which the immune privilege due to the avascular status and active immune inhibition is still intact. Once broken due to infection, sensitization or trauma, rejection will occur. There is enough data to show that when proper DNA-based typing techniques are being used, even low risk perforating corneal transplantations benefit from matching for HLA Class I, and high risk cases from HLA Class I and probably Class II matching. Combining HLA class I and class II matching, or using the HLAMatchmaker could further improve the effect of HLA matching. However, new techniques could be applied to reduce the chance of rejection. Options are the local or systemic use of biologics, or gene therapy, aiming at preventing or suppressing immune responses. The goal of all these approaches should be to prevent a first rejection, as secondary grafts are usually at higher risk of complications including rejections than first grafts.

Corneal transplantation is one of the most common and successful transplant surgeries performed around the world. However, the high-risk corneal transplantation remains a high level of corneal graft failure. Gene transfer of immunomodulatory molecules is considered as one potential strategy in preventing allograft rejection. It is worthy evaluating the effects of the immunemodulating agent on corneal allograft rejection. The purpose of this paper is to investigate the effects and mechanisms of recombinant adeno-associated virus mediated transforming growth factor-beta1 (rAAV-TGF-beta1) on corneal allograft survival using a high-risk rat model after penetrating keratoplasty (PKP). The mean survival time (MST) of corneal grafts was observed and immuno-histochemical staining of TGF-beta1 and Ox-62 was performed in the study. The MST showed significant prolongation in the rAAV-TGF-beta1 group compared to the allograft group. The rejection index (RI) at day 10 revealed was significantly greater in the allograft group than that of the other two groups. Besides the increase of TGF-beta1, the expression of Ox-62 decreasing in rAAV-TGF-beta1 transplanted recipients was detected after transplantation. In short, treatment with rAAV-TGF-beta1 prolongs corneal allograft survival and inhibits the Ox-62 expression in grafts after high-risk PKP.

Herpes simplex virus-1 (HSV-1) infects the majority of the world's population. These infections are often asymptomatic, but ocular HSV-1 infections cause multiple pathologies with perhaps the most destructive being herpes stromal keratitis (HSK). HSK lesions, which are immunoinflammatory in nature, can recur throughout life and often cause progressive corneal scaring resulting in visual impairment. Current treatment involves broad local immunosuppression with topical steroids along with antiviral coverage. Unfortunately, the immunopathologic mechanisms defined in animal models of HSK have not yet translated into improved therapy. Herein, we review the clinical epidemiology and pathology of the disease and summarize the large amount of basic research regarding the immunopathology of HSK. We examine the role of the innate and adaptive immune system in the clearance of virus and the destruction of the normal corneal architecture that is typical of HSK. Our goal is to define current knowledge of the pathogenic mechanisms and recurrent nature of HSK and identify areas that require further study.