One of the main deficiencies of in vivo gene transfer is the difficulty in achieving stable gene expression. Previous work in our laboratory has focused on the attenuation of immunologic responses to adenoviral vectors. Now we have also made considerable progress in the development of a novel integrating viral vector. Sequences from a retrovirus were incorporated into a replication-deficient adenoviral vector backbone. The resulting chimer was able to efficiently infect cells in vivo and in vitro. In addition, the vector demonstrated strong evidence of genomic integration and persistent gene expression. Such a vector would have broad applicability for in vivo gene transfer and gene therapy in a variety of dividing and quiescent cell types. We have continued the characterization of salivary acinar cell and ductal cell promoters. Using an in vitro model of salivary cell differentiation, we have studied the effects of various growth factors and other extracellular matrix components on the induction of salivary amylase. These experiments have allowed us to mimic the effects of Matrigel in a much simpler system and thereby begin to understand the pathways that lead to cytodifferentiation . Studies on the salivary antifungal proteins, histatins, have proceeded in several directions. Adenovirus-mediated expression of histatin 3 in rabbit submandibular saliva was achieved and the recombinant protein was found to be functional in vitro. Laboratory experiments with histatin 3 have revealed a specific binding site for the protein on the C. albicans membrane. Binding and translocation of histatin 3 was shown to be necessary for cell death to occur.
