VIROFECTION - A NEW PROCEDURE TO ACHIEVE STABLE EXPRESSION OF GENES TRANSFERRED INTO EARLY EMBRYOS

A new procedure, virofection, designed to stabilize the expression of transfected DNA has been developed. It exploits the capacity of retrov iruses to integrate their genome into the chromosomes of host cells. T he co-transfection of two plasmids, one carrying the genome of a defec tive retrovirus vector, the other one encoding all the retroviral prot eins, results in a transient production of infectious virus particles. These particles can infect the neighboring cells and this leads to th e stable integration of the vector genome. This procedure is time-savi ng and appears to be quite efficient. When applied to chicken embryoni c fibroblasts cultured in vitro, it resulted in the stable expression of the lacZ gene in more than 30% of the cells, and did not induce chr onic viremia. Stable lacZ expression was also achieved in chicken embr yos in ovo. Virofection appears to be a promising and generally applic able method for implementing stable, safe and efficient gene transfer in vitro and in vivo.