Immune and gene therapies for cancer and infectious diseases

Abstract: Annually more than 20 million deaths are globally caused because of infections or cancer. This accounts for 41.5% of annual deaths. New techniques are supposed to constitute our tools in the fight against these types of deaths. The new technologies of immune and gene therapies promise to revolutionize medicine in the next century. Active immune and gene therapies include both non-specific (such as cytokines and synthetic chemicals) and specific (i.e. vaccination) approaches. Cytokines when delivered by genetic approaches to tumors were reported to affect their capacity to present antigens and to act as targets for natural killer (NK) cells and cytotoxic T cells (CTL). In the first part of my thesis, I have studied the mechanism by which the cytokine interleukin- 10 (IL- 10) alters tumor cell sensitivity to NK and CTL mediated cytotoxicity and affects MHC class I antigen presentation in particular peptide transportation by the transporter associated with antigen presentation (TAP). The delivery of a gene in a suitable expression plasmid to cells in vivo allows the immune system to recognize its product leading to protective immunity against infectious agents or tumors, a process termed plasmid DNA (pDNA) vaccination. In the second part of my thesis I have studied pDNA vaccination and methods to improve this mode of immunization by cytokine genes and by tucaresol a Schiff forming drug. To this end, I have established two clinically relevant animal models. In one, a gene from the tumor associated Epsteine Bar virus (EBV) nuclear antigen 4 (EBNA-4) gene was used, while in the other, the mycobacterial heat-shock protein 65 (Mhsp65) was tested as a pDNA vaccine. In these two models I analyzed the cytokine genes interferon gamma (IFN-[gamma]) and granulocyte macrophage colony stimulating factor (GM-CSF) for their ability to enhance pDNA induced immune responses. In the same models I also tested the effect of the novel immune response modifying adjuvant, tucaresol. In this part of my thesis I have also established the possibility of using HER-2 based immunotherapy for the treatment of human tumors overexpressing this gene product. These studies have provided three candidate genes (EBNA-4, Mhsp65 and HER-2), Peptides, cytokines and adjuvant that could be used for vaccination or to treat patients against cancer and viral and bacterial diseases. pDNA or peptide vaccines based on these could lead to protection from a large range of diseases including tuberculosis, leprosy, typhoid fever, brucellosis, infectious mononucleosis, EBV associated tumors, carcinomas and melanoma. I have shown that cytokines and adjuvants could be used to efficiently enhance the immune response to pDNA vaccines resulting in full protection from tumor outgrowth. An insight into the mechanism by which IL-10 modulates the immune response was presented. I have been able to show how IL-10 affects the MHC-I antigen-processing pathway resulting in alteration of NK and CTL responses.