On the contrary, defective (non-replicating, non-lytic) HSV vectors, engineered to express murine GM-CSF as in vivo cytokine gene transfer vehicles at tumor sites, showed efficacy for active cancer in situ immunotherapy and as systemic tumor vaccines, eliminating the toxicity associated with the systemic administration of recombinant cytokines [89,90]. The gene discussed is CSF2; the disease is neoplasm.