A self-immunomodulating myoblast cell line for erythropoietin delivery

The transplantation of genetically engineered cells faces limitations assoc iated with host immunity. Allogeneic cells are typically rejected in respon se to inherent histo-incompatibility. Even autologous cells can induce an i mmune response toward antigenic molecules expressed following transfer of f oreign genes. The goal of the present study was to investigate the ability of immunomodulating molecules coexpressed with biotherapeutic factors to ov ercome these limitations both in syngeneic and allogeneic cell transplantat ion. The C2C12 mouse myoblast cell line was engineered to express CTLA4lg, a soluble factor blocking T cell costimulation, in conjunction with erythro poietin (Epo), a reporter biotherapeutic protein. In syngeneic C3H mice, my oblasts expressing only mouse Epo were mostly rejected within 2 weeks, as i ndicated by the transient increase in host hematocrit. In allogeneic recipi ents, the same cells induced only a 1-week increase in the hematocrit refle cting an acute rejection process. CTLA4lg expression significantly extended the survival of mouse Epo-secreting myoblasts in approximately half of syn geneic hosts, whereas if led only to a 1-week improvement effect in allogen eic recipients. When combined with a transient anti-CD154 treatment, CTLA4l g expression prevented Epo-secreting C2C12 myoblasts from being rejected in allogeneic DBA/2J recipients for at least 1 month. In contrast, the same a nti-CD154 treatment alone induced only a I week improvement. These results demonstrate that CTLA4lg co-expression associated with a transient anti-CD1 54 treatment can prolong the delivery of recombinant proteins via transfer of ex vivo modified cells in allogeneic recipients.