New Vaccine Approaches, DNA Vaccine Optimization

Our overall goal was to improve DNA and nucleic acid vaccination technologies so that these became rapid, safe, and effective vaccine platforms for AIDS, cancer and other diseases. DNA vaccination has distinct advantages, including that it provides a broad priming of the immune system that may result in a robust and effective immune response. The strong and effective cellular immunity achieved by optimized DNA is an important consideration for the expanding field of cancer vaccines.

Rapid advances in the efficiency of DNA vaccination made this approach very promising for the development of safe and effective vaccines with distinct advantages for many indications, including AIDS and cancer. Yet, further research and development was needed for the DNA vaccine field to fulfill this promise. Our goal was to further improve this technology and contribute to its translation to the clinic. We used molecular biology techniques and animal models to test new vectors, new technologies and new combinations for DNA vaccination. We successfully applied our increased understanding of gene expression regulation to the improvement of DNA vaccines. Previously, we showed that DNA vaccine expression in the tissues is a major limiting step for meaningful immunogenicity and we developed general methods for efficient plasmid expression. The methods (RNA or codon optimization to increase mRNA stability transport and expression) had applications in both DNA and viral vaccine vectors and also in gene therapy protocols. These patented technologies contributed to overcoming a critical barrier for clinical application of DNA vaccines. An additional advancement in DNA vaccines was the development of more efficient delivery methods such as in vivo DNA electroporation. These advancements formed the basis for the accelerated development of DNA vaccines for AIDS, other infectious diseases and also cancer. We  optimized the formulations and delivery of DNA vaccines using molecular adjuvants, liposomes, nanoparticle formulations and electroporation. A novel potential application for cancer is DNA-delivered immunotherapies, based on the development of efficient expression vectors for cytokines and other immunomodulators. We tested the hypothesis that DNA-delivered immunotherapies would be beneficial in cancer models.

We used different DNA vaccine delivery procedures to discover optimal methods of DNA vaccination. This work led us to the conclusion that both the form and the method of delivery of specific antigens strongly affect the produced immune response. We tested different adjuvants for their compatibility with DNA vaccine protocols and developed shortened protocols able to produce a strong humoral immune response. We compared the humoral and cellular immune responses obtained after DNA vaccination to other vaccine modalities. These studies were important in understanding the strengths and weaknesses of different vectors and protocols and provided guidance for further development of improved vaccine protocols.

A new type of DNA vaccine comprising conserved elements (CE) of HIV Gag protein was developed for a clinical trial on the basis of mouse and macaque immunogenicity. Inclusion of a CE immunogen provided a novel and effective strategy to broaden responses against highly diverse pathogens by avoiding decoy epitopes, while focusing responses to critical viral elements for which few escape pathways exist.

Cytokines and Immunomodulatory Molecules in Immunotherapy and Vaccines

The overall goal of this project was to study the gene expression and function of selected cytokines and other immunomodulatory molecules relevant for cancer and AIDS immunotherapy. This was important for the development of more efficient interventions to alleviate, delay or prevent disease through immunotherapy, gene therapy and DNA vaccine technologies. Such novel interventions require a more thorough understanding of all aspects of cellular processes. One study goal was to develop efficient expression vectors by identifying key elements and factors associated with the pathways of posttranscriptional control of gene expression used by many genes, including cytokines. The validity of this approach was demonstrated by the development of efficient vectors for the expression of important cytokines, especially interleukin-15 (IL-15) and interleukin-12 (IL-12).

In the case of IL-15, an understanding of the cellular mechanisms controlling expression led to methods of preparation and purification of the heterodimeric form of this cytokine and demonstrated that the heterodimer is the bioactive form circulating in human blood. This was recognized as an important development in our understanding of IL-15 function. Pharmacokinetic studies in animals showed that the heterodimeric IL-15 has favorable properties for clinical applications.

Rapid progress in the IL-15 clinical development project led to the production of a GMP lot of heterodimeric IL-15, which we named hetIL-15, for clinical trials. Our hypothesis was that IL-15 would activate natural killer cells and tumor-infiltrating T cells. As a result, hetIL-15 may find important applications in cancer immunotherapy.

This project complemented our efforts to improve DNA vaccines (see above) and DNA-delivered immunotherapies. An additional goal of this project was to explore the function of key cytokine genes to establish their role in normal homeostasis and disease processes.

Our collaborators included Genoveffa Franchini, Marjorie Robert-Guroff, David J. Venzon, Jay A. Berzofsky, Thomas Waldmann, Steven A. Rosenberg, and  Barbara K. Felber (NCI); Jeffrey D. Lifson and Elena N. Chertova (Leidos Biomedical Research, Inc./Frederick National Laboratory for Cancer Research); James I. Mullins (University of Washington); Georgia D. Tomaras and David C. Montefiori (Duke Human Vaccine Institute); Timothy Fouts (Profectus BioSciences); Niranjan Y. Sardesai (Inovio); George K. Lewis (Institute of Human Virology/University of Maryland); and David B. Weiner (University of Pennsylvania).