Engineering strategies aim at (a) preventing infection of the nervous system, e.g., by deleting the neurovirulence gene γ34.5/RL1 [13] (b) enhancing tumor-selectivity, e.g., by deleting the ribonucleotide reductase expressing gene ICP6 [14] and (c) increasing immunogenicity by adding genes to express immunostimulatory mediators, such as GM-CSF [15] and IL-12 [16,17] or counteract T-cell exhaustion by arming the HSV-genome with anti-CTLA-4 and anti-PD-1 targeting antibody sequences [18]. The gene discussed is CSF2; the disease is neoplasm.