To Collect Peripheral Blood and Bone Marrow Samples from Donors and Recipients of Blood and Marrow Transplants for Laboratory Research
In his ongoing studies of anti-leukemia immunity and CTL antigens, Dr. Molldrem has studied myeloid-restricted normal proteins that are highly expressed leukemia. Myeloid leukemias express a number of differentiation antigens associated with granule formation. He chose to study Pr3, a 26,000 dalton neutral serine protease that is stored in primary azurophil granules and is maximally expressed at the promyelocyte stage of myeloid differentiation. The human gene contains 5 exons, is localized on chromosome 19p and has recently been cloned. Pr3 is over expressed in a variety of myeloid leukemia cells including 75% of CML patients, approximately 50% of acute myeloid leukemia patients, and approximately 30% of the cases of myelodysplastic syndrome patients. Dr. Molldrem has found that PR1, a 9 aa peptide derived from Pr3 that binds to HLA_A2.1, can be used to elicit CTL in vitro from an HLA-A2.1+ normal donor. These PR1-specific CTL show preferential cytotoxicity toward allogeneic HLA-A2.1 myeloid leukemia cells over HLA-identical normal donor marrow. PR1 is therefore the first peptide antigen identified that can elicit specific CTL lysis of fresh human myeloid leukemia cells. More recently, he has identified PR1-specific CTL in the peripheral blood of CML patients using PR1/HLA-A2 tetramers, and detection of these CTL correlates with a cytogenetic response to either interferon or allogeneic BMT (p = 0.002), thus establishing PR1 as the first human leukemia-associated tumor antigen. By FAC sorting CML patients’ PR1-specific CTL to high purity, he showed that PR1-specific CTL could specifically lyse CML but not normal marrow cells, and that they were HLA-A2 restricted. Dr. Molldrem proposes to improve his methods to efficiently grow PR1-specific lymphocytes in the lab. He will also investigate a new laboratory method to isolate only the PR1-specific lymphocytes from peripheral blood using microbeads that are conjugated to the HLA-A2 molecule plus PR1 peptide. These PR1-spcific lymphocytes will then be expanded to high enough numbers to be transferred to patients with relapsed myeloid leukemia after allogeneic transplant in order to induce GVL without GVHD.