Several preclinical models of stroke and traumatic brain injury from Drs. ST Carmichael, Alcino Silva, and Esty Shohami suggest that the FDA-approved CCR5 reversible co-receptor antagonist, Maraviroc, may lead to better motor outcomes when combined with training, presumably due to enhanced learning. Stroke induces CCR5 expression in neurons in the first month after onset in a mouse model (Carmichael). Knockdown of CCR5 in the motor cortex of adult mice improves recovery after stroke (Carmichael and Silva et al). Maraviroc also improves motor recovery in this model. An Israeli post stroke observational trial (TABASCO, Einor Ben Assayag, et al.) enabled a test of the effects of a naturally occurring loss of function mutation in CCR5 (CCR5 delta32). About 15% of the Ashkenazi Jewish population carries the deletion (CCR5 rs333 - 32). This group in TABASCO had better outcomes for walking speed and the Berg Balance Scale. A Washington University observational study that included some subjects with this deletion also looked positive for better outcomes, but was more equivocal, based on differences in stroke type. Neither gene association study has been published yet.