Natural and induced idiotype immunity in patients with multiple myeloma

Abstract

There is a great need for development of new treatment alternatives for patients with multiple myeloma (MM). The idiotype (Id) immunoglobulin (Ig) expressed by the myeloma B cell clone might be regarded as a tumor specific antigen and as such a target for immunotherapy. The aim of this thesis is to study natural and induced Id immunity in MM patients, using the Id as a vaccine in combination with different adjuvants and also to evaluate T cell immune functions in MM patients.

In the first study, 5 patients with indolent/plateau phase IgG myeloma were immunized intradermally with the autologous Id in combination with granulocyte-macrophage colony-stimulating factor (GMCSF) over a 14 week time interval. All patients developed MHC-restricted Id-specific T cell immunity and one patient developed clinical tumor regression (>50% reduction of the serum M-component level).

In the second study, interleukin (IL)-12 was added as an adjuvant in an attempt to enhance the therapeutic effect of vaccination against myeloma. Twenty-eight patients with stage I or early stage 11 IgG myeloma were included and received the autologous Id vaccine in combination with IL-12, or IL12 plus GM-CSF. Immunization was performed intracutaneously during an induction phase of 14 weeks and thereafter during a maintenance phase of 2 years. An Id-specific T cell response as defined by 3 independent criteria, developed in 4/15 patients in the IL-12 group and 11/13 in the IL-12/GMCSF group (p=0.003). Two patients in the IL12 group had a clinical response (>50% reduction and >25% reduction of their respective M-component concentration). The specific T cell response disappeared during continued vaccination in two third of the patients indicating onset of T cell dysfunction, frequently associated with progressive disease. This study confirms that GM-CSF is an important cytokine for induction of a specific T cell immunity, whereas the role of IL-12 in this setting is not clear.

In the third study, reduction/elimination of circulating clonal tumor B cells were analyzed during Id immunization with real-time, allele-specific oligonucleotide (ASO) polymerase chain reaction (PCR). Among 6 evaluable patients, 4 displayed 54-100% reduction of circulating clonal B cells during vaccination although no significant clinical improvements were noted.

In the fourth study, T cell epitopes within the myeloma Ig variable heavy (VH) chain were predicted. The nucleotide sequence of 5 MM patients' specific Ig VH region was determined and bioinformatics from two databases were used for peptide prediction in relation to the actual HLA haplotype. Several MHC class I and 11 T cell epitopes were identified. The majority of predicted peptides (70%) originated from the complementarity-determining region (CDR) 2-framework region (FR) 3-CDR3 part of the Ig VHregion, which may represent a "hot spot" of particular interest for construction of subunit vaccines.

In the last study, four-color flow cytometry was used to perform a detailed analysis of the surface bound molecules T cell receptor alpha-beta, CD28, CD152, CD154, signal transduction molecules CD3zeta, p56lck, p59fyn, ZAP-70, PI3-k and intracellular interferon-gamma, IL-4 and IL-2 within the CD4 and CD8 populations. Early and advanced stage MM patients were compared and 10 age-matched healthy individuals served as controls. The study demonstrated extensive abnormalities in T cell signaling in MM patients; this was particularly evident in patients with advanced disease. These findings may be of importance for further development of immune-based therapeutic approaches in MM.

MM may be an ideal tumor for immunotherapy as the tumor cell express the unique Id antigen. A deeper knowledge of the immunobiology of the disease and improved vaccine constructs are warranted before it may become part of the clinical therapeutic arsenal in patients with MM.