Immunological and clinical long-term effects of idiotype vaccination in multiple myeloma patients

Abstract

In spite of the promising results shown by new anti-myeloma agents, multiple myeloma (MM) remains incurable and additional therapy to overcome the inevitable disease recurrence is greatly needed. Immunotherapy is currently under evaluation as a novel alternative or complementary therapy in many cancer types. The idiotype (Id) protein is a unique myeloma specific antigen that may be targeted in therapeutic vaccination. This thesis presents and discusses results of ld vaccination in early stage MM patients and underscores the immunological and clinical effects of the vaccine.

In the first study we analyzed the time kinetics of cytokine genes expression (IL-2, IL-5, IFNgamma, GM-CSF and TNF-alpha) and granzyme B in healthy donors to be used as supplementary markers for antigen-specific I lymphocytes in subsequent studies. For most cytokines, the time for maximum accumulation seemed to be obtained after 4 to 8 h of activation. However, a sustained high level could be noticed for up to 24 h. Granzyme B gene expression showed a continuous gradual increase and late maximal accumulation (48-72 h). We concluded that cytokine genes expression would better be measured after 4-8 h of specific stimulation, but also up to 24 h of stimulation is acceptable. Granzyme B may preferentially be measured after 48 h of activation.

In the second study, Id-specific T cell responses were evaluated by multiple read-out systems in 18 patients vaccinated with the ld together with either interleukin (IL)- 12 alone or a combination of IL- 12 and granulocyte macrophage colony stimulating factor (GM-CSF). IL12 alone was noted to induce a Th1 polarized immune response, while the combination of IL12 and GM-CSF induced a significantly higher frequency of responding patients but with a Th2 profile.

In the third study Id-specific T cell responses were monitored simultaneously in peripheral blood and bone marrow of 10 patients. Id-specific responses we found to occur at a similar frequency of patients in both compartments. Comparison of the responses during active immunization with those at the late follow-up showed that the responses decreased significantly by time and shifted from a Th1 to a Th2 profile.

In the fourth study, 28 patients were immunized as indicated earlier over 110 weeks. Id-specific T cell responses were noted in 33% of patients in the IL- 12 group and 85% in the GM-CSF/IL 12 group (p - 0.003). Two third of the responsive patients subsequently lost their specific immunity while developing progressive disease. Median time to disease progression (TTP) was found to be significantly longer in immune responders compared to non-responders. Immune non-response was associated with an increase in the numbers of CD4+/CD25+ cells (Treg cells). Two patients in the IL-12 group had a clinical response (> 50% and > 25% reduction of their respective M-component concentrations).

In the last study patients were monitored for an Id-specific T cell response, and the presence of circulating myeloma B cells (CMC) by real time ASO-PCR during a median time of 46 weeks of maintained ld vaccination. Reduction and/or stable levels of CMC were observed in 6/11 patients. Three patients showed progressive increase in the number of CMC and in 2 patients CMC could not be detected. Patients (n=6) who showed a reduction and/or a stable CMC level mounted an Id-specific T cell response, while those with increasing numbers of CMC (n=3) failed to mount tumor specific T cell immunity (p<0.02).

Taken together, these results indicate that ld immunization in early stage MM patients can induce tumor-specific immune responses that may correlate with reduction of CMC as well as TTP, and clinical responses may also occur. Immune non-response may be associated with increased numbers of Treg cells and progressive disease. Adjuvant cytokines can be a versatile tool for manipulating and directing the anti-tumor immune response.