Vaccination strategies for lymphomas

The anaplastic lymphoma kinase is an effective oncoantigen for lymphoma vaccination

An ideal vaccination strategy against tumors relies on specific antigens that are required for tumor maintenance. For lymphoma, vaccination with subject-specific immunoglobulin idiotypes has had the most promising results. Here we show that DNA vaccination with plasmids encoding portions of the cytoplasmic domain of anaplastic lymphoma kinase (ALK), which has been translocated in different fusion proteins necessary for the growth of anaplastic large cell lymphoma (ALCL), protects mice from local and systemic lymphoma growth. The protection is potent and long lasting and elicits ALK-specific interferon-gamma responses and CD8+ T cell-mediated cytotoxicity. A combination of chemotherapy and vaccination significantly enhanced the survival of mice challenged with ALK+ lymphomas. These findings indicate that ALK represents an ideal tumor antigen for vaccination-based therapies of ALCL and possibly other ALK+ human tumors.

Prophylactic anti-tumor effects in a B cell lymphoma model with DNA vaccines delivered on polyethylenimine (PEI) functionalized PLGA microparticles

Idiotypic sequences, specific to the hypervariable regions of immunoglobulins expressed by malignant B cells offer a therapeutic target in B cell lymphoma. Efficient approaches have been described to clone a single chain fragment of the tumor immunoglobulin (Ig) comprising of heavy and light Ig chains (sFv) fused with proinflammatory chemokines. Tumor associated, poorly immunogenic self antigens encoded by plasmid DNA (pDNA) have been rendered immunogenic by chemokine fusion, thereby targeting to antigen presenting cells (APCs) which differentially express chemokine receptors. Here we present an injectable (parenteral) approach using synthetic polymer based cationic microparticle formulations for enhancing the potency of such chemokine/self antigen expressing plasmid construct. Branched and linear polyethyleneimine (PEI) were conjugated on poly (D, L lactide-co-glycolide) (PLGA) microparticles using carbodiimide chemistry followed by efficient loading of plasmid DNA. In addition to imparting significant buffering ability to these cationic microparticles, flow cytometry studies indicate that these DNA loaded microparticles significantly up regulate CD80 and MHC class II markers in phagocytic RAW264.7 cells, indicating intrinsic adjuvant effects. Intradermal injections in Balb/c mice with these formulations induced significant protection upon tumor challenge with 2.5 times the minimal lethal dose. Long term survival rates were significant (p < 0.05) in comparison with saline injected controls or blank microparticles. Further studies indicated that intramuscular delivery might provide better protection compared to intradermal injections and perform similar to gene gun mediated administration. We conclude, based on these promising in vivo results, that such surface-functionalized microparticles offer an attractive strategy to improve the potency of self antigen-based cancer DNA vaccines.

Therapeutic cancer vaccines

The immunological bases of current approaches to therapeutic cancer vaccination (or 'vacci-treatment') have been established for a decade or longer. The new developments lie mostly in the lessons learnt from clinical testing of these approaches. Three lessons are particularly worthy of note. First, recently completed randomized Phase 3 trials suggest that vacci-treatment with autologous dendritic cells expressing prostatic acid phosphatase (for prostate cancer) or with autologous tumor-derived heat shock protein (gp96)-peptide complexes show promise in enhancing survival of cancer patients. These two approaches are undergoing further randomized clinical testing. Second, immunological monitoring of many clinical trials has failed to identify a surrogate marker for clinical outcomes. Finally, an increasing volume of literature suggests that protective immunity to human cancers is elicited by the mutated antigenic repertoire unique to each cancer.

Anti-lymphoma effect of gammadelta T cells

During the last few years, our knowledge about the activation and control of non-major histocompatibility complex (MHC)-restricted innate effector lymphocytes (such as natural killer (NK) cells, NK T cells and gammadelta T cells) has advanced enormously and immunotherapeutic strategies based on these cell types receive more and more attention. Apart from NK cells, several lines of evidence indicate that T cells, which express an alternative T cell receptor (TCR) composed of a CD3-associated gammadelta heterodimer, also contribute to the innate immune defense against tumors. Human gammadelta T cells represent a small subset of T cells (1-10% of peripheral blood T cells) and differ from conventional MHC-restricted ass T cells in recognition of a unique set of antigens ("phosphoantigens") and the lack of requirement of classical antigen-presenting molecules. Besides their role in the innate immune response against pathogens based on the recognition of distinctive microbial metabolic products (metabolites of the non-mevalonate pathway of isoprenoid synthesis), Vgamma9Vdelta2 T cells that constitute the dominant fraction of gammadelta T cells in humans exert potent cytotoxic activity, especially against lymphoid malignancies, mediated by as yet only partially determined pathway(s) of tumor recognition. This article will review available evidence from pre-clinical and early clinical studies regarding the contribution of gammadelta T cells in the defense against lymphoid malignancies and highlights some important issues that need to be addressed in the future.