Indirect means to elicit a beneficial effect via Treg mobilization in preclinical PD models have been attempted, for example, by Bacillus Calmette–Guérin (BCG) vaccination [17, 18, 26], by delivery of a vasoactive intestinal peptide receptor-2 (VIPR2) peptide agonist [27] and by granulocyte–macrophage colony stimulation factor (GM-CSF) administration [28, 29] that even conducted in a phase 1 clinical trial [30, 31]. The gene discussed is VIPR2; the disease is Parkinson disease.