DECREASED ALLOREACTIVITY TO HUMAN ISLETS SECRETING RECOMBINANT VIRAL INTERLEUKIN-10

The objective of this study was to analyze allogeneic lymphocyte proli ferative responses to cultured human pancreatic islets after gene tran sfer of viral interleukin (IL)-10 to the islets using replication-defe ctive adenoviral vector. Human islets, either whole or dispersed into single cells, were cocultured with adenovector containing an expressio n cassette encoding the viral IL-10 gene under control of an SV40 prom oter, this sequence replacing viral E1A and part of E1B early viral pr otein sequences. Subsequent production of recombinant protein by islet s was determined by ELISA, and was found dependent on the multiplicity of infection (or ratio of vector to target cells). Protein was secret ed by transfected islets at high levels 3-7 days after gene transfer. At high multiplicity of infection (100:1), islet viability was normal, but insulin secretion in response to glucose stimulation was blunted by 50%. Low-level recombinant viral IL-10 secretion by the islets was associated with increased allogeneic lymphocyte proliferation in mixed islet lymphocyte reactions. At protein levels in islet supernatant ab ove 5 ng/ml, lymphocyte proliferation was significantly reduced. This pattern of viral IL-10 effect on lymphocyte proliferation correlated w ell with mixed lymphocyte reaction assays using purified protein. We c onclude that transferred cytokine sequences are secreted by transfecte d islets as a function of the initial vector inoculum. The functional effect of the secreted cytokine viral IL-10 on allogeneic lymphocyte p roliferation is dose dependent. Low-level recombinant protein secretio n tended to augment lymphocyte proliferation whereas high-level secret ion significantly down-regulates this response.