- Pre-Transplant Cohort: Availability of an appropriately matched (as determined by the transplant center) CCR5Δ32 cord blood unit (homozygous or heterozygous) and intention to proceed with transplantation. NOTE: Double cord transplants are allowed. If a double cord is used, at least one cord blood unit should be CCR5∆32 (homozygous or heterozygous).