Intermediate dose thalidomide (200 mg daily) has comparable efficacy and less toxicity than higher doses in relapsed multiple myeloma.

Thalidomide at doses >200 mg has 100% grade 1-2 and 25% grade 3-4 toxicities requiring discontinuation. We report a retrospective study of relapsed myeloma patients treated with thalidomide 200 mg with no dose escalation. Thirty patients were identified; 43% of patients responded with paraprotein decline >75% -- 2 (6%), 50-75% -- 7 (23%), 25-50% -- 4 (14%) and 2 (6%) were stable. All five patients with 13q deletion responded. Only 54% reported grade 1-2 toxicities (none reporting > grade 2) with 5 (17%) discontinuing treatment due to toxicity. Thalidomide 200 mg daily with no dose escalation appears as effective and better tolerated than escalated doses for relapsed myeloma patients.

Adenovector engineered interleukin-2 expressing autologous plasma cell vaccination after high-dose chemotherapy for multiple myeloma--a phase 1 study.

Eight multiple myeloma patients participated in a phase I trial evaluating the feasibility and safety of subcutaneous vaccination with adenovirus engineered, autologous plasma cells after high-dose therapy. Plasma cells were concentrated from bone marrow harvests by negative selection and high gradient magnetic separation. The mean plasma cell yield was 2.61 x 10(8). Transgene expression measured 48 h after plasma cell infection with an IL-2 expressing adenovirus averaged 2.95 ng/ml/10(6) cells. Vaccine production was successful for 88% of patients. Two months after high-dose therapy, six patients received from one to five injections of 3.5-9.0 x 10(7) cells/vaccine. Vaccines were well tolerated with only minor systemic symptoms reported. Injection with tumor cells induced a local inflammatory response consisting predominantly of CD8+ and/or TIA-1+ T-lymphocytes. Myeloma specific anti-tumor responses, assessed by interferon-gamma (IFN-gamma) release and cytotoxic T cell killing of autologous tumor cells, were not enhanced after vaccination in one evaluable patient. Clinical response, manifested as a decrease in serum paraprotein, was not observed in the one patient who had measurable disease at the time of vaccination. These results demonstrate that the generation of adenovector modified plasma cell vaccines is technically feasible and can be safely administered post-transplant. Further studies of immunlogic and clinical efficacy are required.

Irreversible loss of donor blood leucocyte activation may explain a paucity of transfusion-associated graft-versus-host disease from stored blood.

Transfusion-associated graft-versus-host disease (TA-GVHD) is usually a fatal outcome of blood transfusion therapy, caused by viable leucocytes contained in the donor blood. Most cases of TA-GVHD occur when less than 4-d-old blood is transfused. We therefore examined the molecular changes that occur during storage that may account for the paucity of TA-GVHD following infusion of older blood. Leucocyte number and viability were essentially unchanged from freshly obtained blood, but the expression of cell-surface lymphocyte activation antigens (CD3, CD4, CD28, CD2, CD45) decreased rapidly within the first 24 h and continued to fall to less than 20% of original levels by d 9 of storage at 4 degrees C. The decrease in CD antigen expression directly correlated with a decreasing ability to induce activation of the T-lymphocyte cellular signal transduction pathway. As a result, cells became less responsive in a mixed lymphocyte culture (MLC) by d 3, with abrogation of the MLC responsiveness by d 5. Donor leucocytes stored for 4 d or less at 4 degrees C were able to partially re-express CD antigens and reconstitute their signalling pathway when placed at 37 degrees C. whereas those stored for more than 4 d were not. These irreversible changes result from a permanent downregulation of donor cell protein synthesis. These findings provide a mechanism to explain the paucity of TA-GVHD following transfusion of blood that is more than 4 d-old. Further study may show that aged blood provides additional assurances for the prevention of TA-GVHD; however, use of aged blood should not replace current protocols using irradiation.

Immunoregulatory activity of the T-cell receptor alpha chain demonstrated by retroviral gene transfer.

We have previously described an antigen-specific I-Ad-restricted T-cell hybridoma, A1.1, that constitutively releases an antigen-specific immunoregulatory activity into supernatants. Using retrovirally mediated gene transfer, we have found that transfer of the T-cell receptor alpha chain (TCR alpha) gene from A1.1 to a number of other T-cell hybridomas effectively transferred the ability to produce the activity. Gene transfer of the TCR beta chain (TCR beta), however, did not transfer this ability. The regulatory activity from cells expressing the A1.1 TCR alpha bound to and was eluted from an anti-TCR alpha monoclonal antibody and displayed fine antigenic specificity identical to that of supernatants from A1.1. The possibility that this activity represents a secreted form of the TCR alpha (as opposed to shed cell-surface TCR) was examined in BW1100 cells, lacking TCR alpha and TCR beta, which produced the antigen-specific activity after gene transfer of the A1.1 TCR alpha gene. The expression of the immunoregulatory activity in supernatants correlated with a direct antigen-binding activity as detected by ELISA, thus raising the possibility that antigen binding is relevant to the mechanism of action of the soluble TCR alpha. We discuss these observations and our earlier studies suggesting an immunoregulatory role for soluble TCR alpha.

The role of natural suppressor and natural killer activities in resistance to hemopoietic transplantation in unirradiated hosts.

We report here that bone marrow stem cell engraftment in unirradiated hosts correlates with levels of natural suppressor (NS) activity in the host at the time of transplantation. This is shown in the antibody-facilitated murine chimeras, in which conditioning consists of a single injection of anti-host MHC antibody, which results in long term hemopoietic engraftment in P----F1 and syngeneic donor-host combinations. The data establish that, in two independent situations, engraftment is reduced in hosts with elevated NS activity. Resistance to engraftment in antibody-conditioned adult hosts is increased by prior administration of CFA, which also increases NS activity. Likewise, neonatal animals, which are highly resistant to antibody-facilitated engraftment, exhibit a spontaneously-increased level of NS activity. This resistance declines with the ontogenic waning of splenic NS activity. Conversely, administration of facilitating antibody decreases host bone marrow NS activity, while anti-MHC antibodies that fail to facilitate engraftment do not reduce it. NK activity, on the other hand, correlates poorly with resistance or susceptibility to marrow engraftment in these situations. These results suggest that immunoregulatory functions associated with hemopoiesis may control engraftment of donor stem cells in unirradiated hosts.

Facilitation of syngeneic stem cell engraftment by anti-class I monoclonal antibody pretreatment of unirradiated recipients.

We have established a murine model of syngeneic bone marrow transplantation based on the use of monoclonal antibody as the sole conditioning regimen in unirradiated recipients. Administration of a single injection of monoclonal antibody directed against major histocompatibility complex-encoded class I determinants facilitated permanent hemopoietic stem cell engraftment without any apparent side-effects. Whereas untreated hosts exhibited a maximal chimerism of 15% at donor cell doses of up to 12 X 10(7) bone marrow cells, pretreatment by 2 mg of anti-class I antibody one week prior to transplantation of 3 X 10(7) syngeneic bone marrow cells resulted in a mean donor representation of about 80%. The antibody can be given up to four weeks prior to transplantation, and the degree of donor engraftment observed is a function of the dose of antibody administered. The fact that specific antibody enhanced engraftment in two strain combinations indicates that antibody is the active agent in facilitating engraftment and that facilitation is not strain-restricted. Anti-class I antibodies of the IgG2a, but not IgG1, isotype are effective in promoting engraftment. Although the isotype requirement suggests a role for antibody-mediated cytotoxicity in promoting stem cell engraftment, the extensive time-frame of facilitation suggests that other effects of the antibody may also be involved. The model of syngeneic bone marrow transplantation we describe here will be useful in studying the mechanisms regulating stem cell engraftment and may have potential clinical application as an approach to autologous marrow transplantation.