TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Composition: (I) comprises genetically engineered cells, preferably stromal or parenchymal cells and a carrier composed of extracellular matrix proteins or polymerizable or cross-linking photopolymerizable hydrogel, preferably alginate. One of the gene product is a chimeric receptor whose over expression is controlled by constitutive regulatory elements. The target gene is a reporter gene, preferably a growth factor, hormone or cytokine and its expression indicates the need for medical attention. The expression of the target gene is capable of correcting, modifying or regulating the physiological conditions such as change in glucose, insulin or glucagon levels, to which the engineered cells responds. The target gene expression may have an antiviral, antibacterial, antimicrobial or anticancer effect. (I) further comprises a cell engineered to express a gene that results in reversible immortalization of the cell.Preparation: The genetically engineered cells are grown on a living stromal tissue prepared in vitro, comprising stromal cells and connective tissue proteins naturally secreted by the cells attached to and enveloping a framework of a biocompatible non-living material formed into a three-dimensional structure with interstitial spaces bridged by the stromal cells. ACTIVITY - Antiviral; antibacterial; antimicrobial; cytostatic; antiulcer. The antiviral activity of (I) in response to the presence of the virus was studied. Stromal cells co-transfected with pCI-CD4 construct, consisting of human CD4 cloned into the pCI mammalian expression vector and pHIVtat-ribozyme construct, consisting of an human immunodeficiency virus (HIV)-ribozyme cloned into an HIV-tat inducible vector were grown in three-dimensional cell culture system. The cells were encased in a biocompatible capsule and implanted in vivo. HIV binds to the constitutively expressed CD4 molecule on the encapsulated stromal cells, infects the cells and the expression of the HIV tat protein induces the expression of HIV-ribozyme which cleaves HIV RNA.    MECHANISM OF ACTION - (I) is a bioreactor for gene therapy.    ADMINISTRATION - The genetically engineered cells or tissues are administered locally or systemically as an implant or in injectable form. No dosage is suggested.