Anti-Inflammatory & Anti-Allergy Agents in Medicinal Chemistry (Formerly Current Medicinal Chemistry - Anti-Inflammatory and Anti-Allergy Agents) - Volume 6, Issue 2, 2007

There has been fluctuating interest in gene therapy since the first therapeutic gene was successful delivered. However, gene therapy still offers substantial potential in modern medicine, as evidenced by clinical realisation of therapeutic gene delivery in those areas in which pharmacological interventions are lacking or failing. The possibilities of therapies are rather broad ranging from inherited disorders to emerging or re-emerging diseases. From this perspective, two factors have played a crucial role: the identification of genes related to biological dysfunction and the development/isolation of new and promising gene delivery systems. Immunology is implicitly linked to gene therapy from many different aspects. Gene therapy can in fact be used to treat immunological/haematological disorders and to manipulate the immune system by enhancing or preventing inflammation and/or the immune response. On the other hand, gene therapy itself can stimulate the immune system either through the delivery vector or the transgene, leading to serious complications. This special focus issue on gene therapy for modulating immune/inflammatory responses is articulated in two main subtopics, describing respectively direct targeting of the immunological precursor/effector and indirect approaches to modify the inflammation/immune response. In the first part of this issue, Imai et al. examine the perspective of natural killer cell gene therapy and provides clues as to how it is possible to genetically modify these effectors by expressing chimeric receptors targeting cancer (specifically leukemic cells). The current status of gene therapy approaches for the treatment of rheumatoid arthritis is discussed by Vervoordeldonket and collaborators, who also point out the safety issues related to the clinical approach. In their review, Von Laer et al. describe the approaches aiming to reconstitute a functional immune system in AIDS patients and provide recent insights into the latest clinical trial. In the second subtopic, Carey et al. focus on the induction and re-establishment of tolerance by targeting B cells. Okada and Butterfield detail the efforts made in tumour vaccinology through manipulation of dendritic cells. In their paper Tschoeke and Oberholzer highlight how our current understanding of dendritic cell biology had provided new tools to modulate acute inflammation. Finally, our group describes strategies used to target endothelial cells in order to induce tolerance or stimulate the immune response and highlights some issues that can affect gene delivery to endothelium. We hope that the publication of comprehensive and critical reviews will provide a significant contribution to our understanding of how gene therapy can be used to modulate the immune response. A personal thank to Andrew George for his precious suggestions, Mark Gumbleton for providing some editorial tips and Saima Ghaffar for her support.

Natural killer (NK) cells have the capacity to recognize and kill a wide range of cancer cells. However, many cancer cells are resistant to NK cell cytotoxicity, mainly because they express molecules which inhibit NK cell activation. Previous studies have shown that enforced expression of chimeric receptors composed of single-chain variable domain of murine antibodies and human signaling molecules can redirect the specificity of T lymphocytes. The success of this approach depends on the identification of a suitable target molecule on cancer cells and on the ability of the receptor to deliver appropriate activation signals. We developed a method to express chimeric receptors in NK cells. Considerable NK cell expansion was obtained by co-culturing peripheral blood cells with the leukemia cell line K562 modified to express membrane bound-interleukin 15 and the ligand for the costimulatory molecule 4-1BB. Expanded NK cells were then transduced with anti-CD19 receptors which deliver activation signals through CD3ζ and 4-1BB. NK cells expressing these receptors became highly cytotoxic against NK-resistant CD19+ leukemic cells. We here review the methodologies for expanding and redirecting the specificity of NK cells, explain the rationale for NK-cell therapies of leukemia and lymphoma, describe potential targets for genetically-modified NK cells, and discuss future clinical applications of NK cell expansion and genetic modification in cancer therapy.

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterised by persistent joint swelling and progressive destruction of cartilage and bone. The primary manifestations are pain, swelling, and limited joint motility due to inflammation of the synovial membrane. In addition to conventional therapies, biologicals targeting cytokines and their receptors have proven useful as specific therapies for RA. Although these new biologicals have improved treatment to a certain extent and do provide proof of principle for targeted therapies, many patients continue to experience inflammation in one or more joints and repeated injections of the recombinant protein are needed for a long-term therapeutic effect. Gene therapy can provide stable, long-term expression of therapeutic proteins at the site of inflammation and thereby improve the treatment of RA and reduce costs related to the treatment with biologicals. Several gene therapy approaches have been developed and tested in animal models of arthritis. Currently a large number of ongoing studies are attempting to improve the efficacy and safety of vectors that are promising for gene therapeutic applications in humans. In addition, studies have been initiated to select new therapeutic candidate genes for the treatment of RA. After almost 20 years of preclinical research the first clinical trials in RA patients have been performed or are ongoing. This review describes the current status of the most promising vectors and therapeutic genes for gene therapy in RA.

Antiviral drug therapy can effectively suppress HIV replication, but emerging viral resistance and drug toxicity limit long-term therapeutic efficacy. In addition, regeneration of the T helper cell repertoire is often incomplete. The current major challenges in the treatment of HIV infection are therefore the reconstitution of cellular immunity, and especially of the HIV-specific immune response, and the suppression of virus replication in patients with HAART failure. Several gene therapeutic strategies for immune reconstitution of AIDS patients have been described. Preclinical and clinical studies have examined the safety and efficacy of two basic approaches: firstly, the transfer of autologous T cells armed with recombinant receptors that target HIV antigens to specifically increase antiviral immunity and, secondly, the transfer of genetically modified T cells or hematopoietic progenitor cells that express an antiviral gene. However, for both approaches, engraftment levels of gene-modified cells have not been sufficient to reconstitute cellular immunity and to effectively reduce the overall viral load in patients. Strategies to improve the technologies and procedures involved in gene therapeutic immune reconstitution of AIDS patients are discussed.

The ability of B cells to function as tolerogenic antigen presenting cells (APCs) in vitro and in vivo, makes them ideal targets for gene therapy strategies focused on the induction and re-establishment of tolerance. Current therapy methods employ retroviral vectors for infection of B cells or bone marrow cells and subsequent expression of the target antigen. Moreover, the efficacy of peptide-IgG fusion constructs which take advantage of the tolerogenic properties of IgG has been demonstrated. In this review, we discuss gene therapy approaches mediated by B cells and bone marrow cells for tolerance acquisition in various mouse models for autoimmune disease, hemophilia and transplantation. The results indicate that gene therapy strategies successfully reduce the incidence of disease, or delay disease onset in multiple mouse models for autoimmune disease and hemophilia. Additionally, gene therapy has proven effective in a mouse transplantation model. While these studies show great promise, the mechanisms involved in tolerance, including the role of regulatory T cells, will need to be more clearly defined before the transition to a clinical setting can occur.

Although animal studies have shown that tumor antigen (TA)-pulsed dendritic cell (DC)-based vaccines can mediate antitumor effects in vivo, human clinical trials utilizing this strategy have thus far had only modest success. In an effort to improve the efficacy of tumor vaccines, numerous investigators have explored the genetic engineering of DC to impart cytokine or TA-expression capability on DC. These efforts have focused on enhancing TA presentation and as well as subsequent T-cell activation and expansion. This chapter reviews recent progress in studies aimed to potentiate the efficacy of DC-based vaccines by genetic engineering of DCs with cDNAs encoding immuno-stimulatory cytokine-genes or TAs.

Acute inflammation and the innate immune response to tissue trauma mark a critical pathophysiological challenge within the clinical course of severely injured and critically ill patients. Among the most potent cellular components of the innate host defense system are dendritic cells (DC). This highly effective network of antigen-presenting cells (APC) carries the ability to initiate and amplify diverse immune responses in respect of an appropriate activation signal. Upon activation, DCs direct the immune response towards developing either a Th1 or Th2 response, thus determining the outcome of the inflammatory or infectious stimulus. Advances in the understanding of DC immunobiology have provided new concepts in the treatment of various inflammatory diseases. With gene therapy constantly evolving new methods of celltargeted manipulation of gene expression, DCs have proven to be an exciting new tool in functionally modulating the immune response. In this review we summarize the pivotal functions of DCs and highlight their promising potency of representing an effective immunotherapeutic tool in the treatment of acute inflammation.

Although endothelial cells are not immunological cells in sensu stricto, they play an important role in controlling inflammation/immune responses. The endothelium is involved in a wide range of pathologies, the most common being vascular diseases and cancer, and they also are central to transplant rejection. Genetic modification of endothelium allows different strategies for inducing tolerance, modulating inflammation, stimulating the immune response or inhibiting the formation of new blood vessels. In this context, the lack of effective and specific pharmacological interventions renders endothelial cells extremely attractive for gene therapy applications. Despite efforts made to genetically modify endothelial cells, the results obtained have suffered from the differences of the endothelium at the different anatomical sites. Several studies are currently being developed to specifically target endothelium using viral and non viral gene delivery approaches. We highlight here some strategies used for genetically manipulating endothelial cells with the aim of inducing tolerance to allograft, or enhancing immunity and/or inhibiting uncontrolled endothelial cell proliferation in tumours.