Adenoviras-mediated expression of human CD59 on xenogeneic endothelial cells: Protection against human complement-mediated lysis and induction of cellular activation by adenoviral transduction

Adenovirus-mediated expression of human CD55 or CD59 protects adult porcine islets from complement-mediated cell lysis by human serum

BACKGROUND

Protection against complement activation may reduce acute islet damage in pig-to-human islet xenotransplantation. Expression of the human complement regulatory proteins decay-accelerating factor (DAF, CD55) or CD59 was induced on intact adult porcine islets (APIs) by adenoviral transduction. The functional capacity of the transgenes was examined in vitro after exposure to fresh human serum.

METHODS

Intact APIs were transduced with adenoviral vectors Ad.hDAF or Ad.hCD59 or a control vector. After 3 days, the islets were trypsin dissociated to a single-cell suspension. A cytotoxicity assay was performed in which the islet cells were incubated with human complement active AB serum. Flow cytometry and immunohistochemistry were used to evaluate transgene expression.

RESULTS

APIs could be transduced to express hDAF or hCD59. Flow cytometry analysis of islet single cells revealed that only a fraction of the cells expressed the transgene; immunohistochemical staining of transduced islets demonstrated that mainly cells located in the periphery of the islets were expressing the protein. Cells from nontransduced islets or islets expressing the control protein were sensitive to lysis in human sera (66+/-4.0% and 73+/-3.7% cytotoxicity, respectively). Single cells from islets transduced with hDAF and hCD59 were partially protected from lysis. Islet cells expressing hCD59 were slightly less sensitive to lysis (33+/-3.3%) than cells expressing hDAF (45+/-3.5%).

CONCLUSIONS

These data show that intact pig islets can be transduced to express human regulators of complement activation on the surface and that pig islet cells expressing hDAF or hCD59 are less sensitive to complement-mediated lysis.

Development of Adenovirus Vectors Encoding Rat Complement Regulators for Use in Therapy in Rodent Models of Inflammatory Diseases

C activation has been implicated in the pathogenesis of numerous inflammatory human diseases and disease models. A therapy based on C inhibition might therefore be of benefit to reduce inflammation and ameliorate disease. C inhibition in vivo can be accomplished by the delivery of soluble recombinant C regulators either systemically or directly to a target site, but effects are transitory. We have developed a strategy for the efficient delivery of the membrane-bound rat C inhibitors, CD59, Crry, and decay-accelerating factor (DAF), using replication-deficient adenovirus vectors with the intention of treating rat models of disease in which C is implicated. The adenovirus recombinants(RAd), RAdCD59, RAdCrry, and RAdDAF, respectively, have been tested for expression and function of the transgene in vitro. Infection of human fetal foreskin fibroblasts resulted in high levels of expression of each of the rat inhibitors. The constructs were also tested for inhibition of rat C-mediated cell lysis and C3b deposition. In a cell lysis assay, each inhibited to varying degrees of efficiency in the order RAdCD59 = RAdDAF > RAdCrry. In a C3b deposition assay, RAdDAF caused a greater reduction in C3b deposition than RAdCrry and RAdCD59 was ineffective. These agents, individually or in combination, provide the tools for testing the effects of prolonged inhibition of C at a target site on the progress of experimental models of disease.