ANTIRETROVIRAL EFFECT OF A GAG-RNASE HI FUSION GENE

We have previously shown that a molecule consisting of a fusion of a C a2+-dependent nuclease (from Staphylococcus aureus) to a retroviral co at protein specifies a potent antiviral specific for that retrovirus. Genes specifying such fusion proteins can be delivered to virus-suscep tible cells, providing an antiviral gene therapy aimed at limiting vir us spread. We report here the results of experiments to vary the nucle ase moiety of such fusion proteins. We found that one nuclease, Serrat ia marcescens nuclease, was extremely toxic to host cells and hence no t likely to be useful for therapeutic purposes. A second nuclease, Esc herichia coli RNase HI was found to be nontoxic and highly effective a gainst a murine leukemia virus when it was fused to the leukemia virus coat protein. The fusion protein was enzymatically active and stably expressed, without apparent toxicity to host cells. Reduction in infec tious virus output was as high as 97-99%. These studies provide a mode l system for the development of gene therapeutic agents aimed at comba ting retroviral infections in vivo.