Ex-vivo Primed Memory Donor Lymphocyte Infusion to Boost Anti-viral Immunity After T-cell Depleted HSCT

HSCT from an allogeneic donor is the standard therapy for high-risk hematopoietic malignancies and a wide range of severe non-malignant diseases of the blood and immune system. The possibility of performing HSCT was significantly limited by the availability of donors compatible with the MHC system. However, modern ex-vivo and in vivo technologies for depletion of T lymphocytes have made it possible to improve the outcomes of HSCT from partially compatible related (haploidentical) donors. In representative groups, it was shown that the success of HSCT from haploidentical donors is not inferior to standard procedures of HSCT from HLA-compatible unrelated donors. HSCT from haploidentical donors in children associated with the deficit of the adaptive immune response, which persists up to 6 months after HSCT and can be an increased risk of death of the patient from opportunistic infections. To solve this problem, the method of infusion of low doses of donor memory T lymphocytes was introduced. This technology is based on the possibility of adoptive transfer of memory immune response to key viral pathogens from donor to recipient. Such infusions have been shown to be safe and to accelerate the recovery of the pathogen-specific immune response. The expansion of virus-specific T lymphocytes in the recipient's body depends on exposure to the relevant antigen in vivo. Thus, in the absence of contact with the viral antigen, the adoptive transfer of memory T lymphocytes is not accompanied in vivo by the expansion of virus-specific lymphocytes and does not form a circulating pool of memory T lymphocytes, that can protect the patient from infections. Therefore the investigators assume that ex-vivo priming of donor memory lymphocytes with relevant antigens can provide optimal antigenic stimulation and may solve the problem of restoring immunological reactivity in the early stages after HSCT. Technically ex-vivo primed memory T lymphocytes will be generated by short incubation of CD45RA-depleted fraction of the graft (a product of T lymphocyte depletion) with a pool of GMP-quality peptides representing a number of key proteins of the viral pathogens. The following are proposed as targeted antigens: CMV pp65, EBV EBNA-1, EBV LMP12A, Adeno AdV5 Hexon, BKV LT, BKV VP1. An infusion of donor memory lymphocytes will be performed on the day +1 after transplantation. Parameters of the assessment will be safety and efficacy (immune response by day 60 and stability (responses by day 180).