DONOR LEUKOCYTE INFUSION

• Introduction
• DLI for Relapse of Malignancy
• DLI for Infectious Complications
• Prophylactic DLI
• Disadvantages of DLI
• In vitro engineering of DLI
• Adoptive Immunotherapy using Donor T Cell Grafts
• Summary

An immunologic anti-tumor effect contributes to increased longterm survival after allogeneic stem cell transplantation for some malignancies. Evidence that this graft-vs-leukemia (GVL) effect is mediated by donor T cells includes: (a) increased recurrence of malignancy (CML and AML) in patients receiving T-cell depleted allogeneic grafts [1], (b) the probability of tumor relapse is negatively correlated with the degree of T cell-mediated graft versus host disease (GVHD) [2], and (c) animal studies have proven that alloreactive T cells induce GVL [3]. This review focuses on the therapeutic induction of GVL by donor leukocyte infusion (DLI) for the treatment of cancer relapse or infectious complications after allogeneic transplantation.

DLI for Relapse of Malignancy

DLI has been used successfully in the treatment of relapsed primary malignancy after allogeneic transplantation [4-7]. The best and most consistent results are observed with CML, suggesting that these tumor cells are more immunogenic than other types of leukemia cells [7]. In acute leukemia, DLI has been less effective, with only about 15% of patients achieving complete remission. There have been no reports of DLI-induced remission in either relapsed NHL or CLL. DLI-induced remission may take up to 3 months to occur; thus, relapse of more rapidly growing malignancies may not be amenable to current DLI protocols.

The clearest indication for DLI is relapsed CML after allogeneic transplantation. DLI is clearly contraindicated in patients experiencing severe GVHD. It is still controversial whether DLI should be used for relapsed AML or ALL, as the chance of remission is low and the risk of causing GVHD is quite high. However, an initial trial of DLI may be reasonable for relapsed acute leukemia given the paucity of other options. The timing and frequency of DLI are not well established and vary from institution to institution. Usually, if there is evidence of molecular, cytogenetic, or hematologic relapse of CML after allogeneic transplantation, the original donor undergoes leukapheresis for collection of peripheral blood mononuclear cells. A typical dose of cells for DLI is 108 donor T cells/Kg recipient body weight. This dose can be collected in 1 -2 apheresis procedures depending upon the donor's peripheral blood WBC.

Remission post-DLI generally occurs within 4 to 24 weeks and usually occurs faster for AML than CML. It is unclear why the time to remission is so long; it is likely that during this time interval, T cells necessary for the anti-leukemic response are homing to sites within the immune system (e.g. spleen and lymph nodes), responding to the relevant allo-antigens, and expanding in vivo until they reach a threshold level at which a clinical effect is detectable.

DLI for Infectious Complications

DLI has been highly successful for the treatment of post-transplant infectious complications, particularly those caused by Epstein-Barr Virus (EBV) and cytomegalovirus (CMV). EBV infection is controlled in the normal host by virus-specific T lymphocytes which lyse infected B cells. EBV lymphoproliferative disease (EBV-LPD) is one of the most dire complications after allogeneic transplantation. Both T cell depletion of the allogeneic graft (to prevent GVHD) and immunosuppressive drugs (to prevent or treat GVHD) can have the deleterious effect of permitting reactivation of latent donor B cell-derived EBV. The transfer of peripheral blood T cells from the donor (DLI) is a safe and effective way to reconstitute cellular immunity against EBV after allogeneic transplantation. The dose of T cells required for this effect is less than that required for treatment of recurrent CML because of the high frequency of EBV-specific T cells in donor blood (approximately 1 in 50,000 circulating peripheral blood T cells).

CMV infection after allogeneic transplantation occurs due to insufficient numbers of CMV-specific CD8+ T cells. CMV-related complications occur in 20-50% of T cell-depleted allogeneic transplants, usually within the first 1-2 months post-transplantation. The risk of CMV-related complications has decreased with the use of ganciclovir and foscarnet. In addition, the risk of CMV infection can be decreased by prophylactic DLI to restore cell-mediated immunity in the transplant recipient.

Prophylactic DLI

Animal studies suggest that delayed infusion of lymphocytes after establishment of the chimeric state is less likely to cause GVHD than infusion of lymphocytes simultaneous with stem cells. Clinical trials have found that prophylactic DLI after transplant decreases the risk of malignant recurrence. Therefore, one transplant regimen may be to infuse allogeneic stem cells depleted of T cells after high dose chemotherapy, and after a time delay of 6-8 weeks, administer DLI to prevent relapse and infectious complications. However, the high risk of inducing severe GVHD has opposed this strategy.

Disadvantages of DLI

Complications of DLI include acute and chronic GVHD and pancytopenia. Of patients who obtain complete remission of CML following DLI, approximately 80% develop grade II-IV GVHD. Patients who receive a lower dose of T cells (less than 107 T cells/Kg) have a lower incidence of GVHD (approximately 10%) [8] but also a lesser chance of remission. DLI dose has not predicted the induction of GVL vs. GVHD. Pancytopenia can occur from 1 to 5 months after DLI, often just prior to a beneficial clinical GVL response [9]. Pancytopenia may be due to depletion of host-derived normal hematopoietic cells from the marrow. In one study, only those patients with >10% host-derived CD34+ cells in their bone marrow prior to DLI experienced significant aplasia after DLI [10]. These data suggest that chimerism studies should be performed prior to DLI; those patients with a high percentage of host-derived hematopoiesis should perhaps receive both DLI (to induce GVL) and donor hematopoietic stem cells (to reduce or prevent the period of aplasia.

In vitro engineering of DLI

Due to the high morbidity and mortality associated with GVHD after DLI, novel methods are being developed to increase the chance of achieving GVL while decreasing the risk of GVHD. These include nonspecific in vitro stimulation of donor T cells with interleukin-2 to increase the GVL effect [5], and insertion of activatable "suicide" genes into donor leukocytes which, when activated, kill the donor leukocytes and abort GVHD. The latter approach has been effective in early clinical trials [11].

Adoptive Immunotherapy using Donor T Cell Grafts

The ideal treatment for tumor recurrence or viral infection after allogeneic stem cell transplantation would be to administer donor cells that are specifically targeted to tumor cells or virally infected cells, which do not harm normal host cells. Induction of antigen-specific T cell immunity without triggering GVHD has become feasible and is currently being tested for tumor-specific antigens, as well as for antigens expressed on cells infected by EBV or CMV.

Summary

DLI is highly successful in the treatment of post-transplant relapsed CML, as well as EBV- or CMV-related complications, including post-transplant lymphoproliferative disease. The major disadvantage to DLI is the occurrence of GVHD. In the future, antigen-specific "designer" leukocytes may be engineered and administered prophylactically to suppress tumor recurrence and infectious complications after allogeneic transplantation.

References

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2. Horowitz MM, Gale RP, Sandel PM, Goldman JM, Kersey J, Kolb H-J, Rimm AA, Ringden O, Rozman C, Speck B, Truitt RL, Zwaan FE, Bortin MM (1990) Graft-versus-leukemia reactions after bone marrow transplantation. Blood 75:555-62.

3. Truitt R, Johnson B (1995) Principles of graft-vs.-leukemia reactivity. Biol Blood Marrow Transplant 1:61-8.

4. Porter D, S. M, C. M, Ferra J, Antin J. (1994). Induction of graft-versus host disease as immunotherapy for relapsed chronic myeloid leukemia. N. Engl. J. Med. Vol 330 #2:100-06.

5. Slavin S, Naparstek E, Nagler A, Ackerstein A, Samuel S, Kapelushnik J, Brautbar C, Or R. (1996). Allogeneic cell therapy with donor peripheral blood cells and recombinant human interleukin-2 to treat leukemia relapse after allogeneic bone marrow transplantation. Blood 87:2195-204.

6. Mehta J, Powles R, Singhal S, Tait D, Swansbury J, Treleaven J. Cytokine-mediated immunotherapy with or without donor leukocytes for poor-risk acute myeloid leukemia relapsing after allogeneic bone marrow transplantation. Bone Marrow Transplantation 16(1):133-7, 1995

7. Kolb H, Mittermüller J, Clemm C, Holler E, Ledderose G, Brehm G, Heim M, Wilmanns W (1990) Donor leukocyte transfusions for treatment of recurrent chronic myelogenous leukemia in marrow transplant patients. Blood 76:2462-5.

8. Mackinnon S, Papadopoulos EB, Carabasi MH, Reich L, Collins NH, Boulad F, Castro-Malaspina H, Childs BH, Gillio AP, Kernan NA, Small TN, Young JW, O'Reilly RJ.(1995) Adoptive immunotherapy evaluating escalating doses of donor leukocytes for relapse of chronic myeloid leukemia after bone marrow transplantation: separation of graft-versus-leukemia responses from graft-versus-host-disease. Blood 86:1261-26.

9. Giralt S, Hester J, Huh Y, Hirsch-Ginsberg C, Rondon G, Seong D, Lee M, Gajewski J, Van Besien K, Khouri I, Mehra R, Przepiorka D, Korbling M, Talpaz M, Kantarjian H, Fischer H, Deisseroth A, Champlin R. (1995). CD8-depleted donor lymphocyte infusion as treatment for relapsed chronic myelogenous leukemia after allogeneic bone marrow transplantation. Blood 86:4337-43.

10. Keil F, Haas O, Fritsch G, Kalhs P, Lechner K, Mannhalter C, Reiter E, Niederwieser D, Hoecker P, Greinix H (1997) Donor leukocyte infusion for leukemic relapse after allogeneic marrow transplantation: lack of residual donor hematopoiesis predicts aplasia. Blood 89:3113-7.

11. Bonini C, Ferrari G, Verzeletti S, Servida P, Zappone E, Ruggieri L, Ponzoni M, Rossini S, Mavilio F, Traversari C, Bordignon C (1997) HSV-TK gene transfer into donor lymphocytes for control of allogeneic graft-versus-leukemia. Science 276:1719-24.

Diane S. Krause, MD, PhD