Geoffrey W. Stone, Ph.D.

Research Assistant Professor
Room 743, Batchelor Children's Research Institute
1580 NW 10th Avenue (R138)
Miami, FL 33136
Telephone: 305-243-2189
Email:gstone@med.miami.edu

Research Interests:

A fundamental challenge in modern immunology is the development of an effective and safe HIV vaccine.  The main focus of our laboratory is HIV vaccine development; both to prevent an initial infection (prophylactic vaccination) as well as enhancing the anti-HIV immune response in HIV-positive patients (therapeutic vaccination).  Our lab utilizes basic research in molecular biology, protein biochemistry, immunology, and viral pathology to develop innovative approaches to HIV vaccine development, including novel molecular adjuvants.  In addition, we are interested in the application of these new adjuvant technologies to related vaccines against cancer, malaria, and other infectious diseases.  By developing a ‘Bench to Bedside’ approach to HIV vaccinology, novel vaccine ideas from basic immunology studies will be tested at the University of Miami in collaboration with partners in GMP manufacture and HIV clinical trial development.

1. Clinical studies of therapeutic HIV vaccines utilizing ex vivo antigen-loaded dendritic cells

HIV infected patients display a strong cellular immune response to the virus, but this response is unable to effectively control viral load and maintain CD4+ T cell counts in the majority of individuals.  Our laboratory is exploring the use of mRNA transfected dendritic cells as a method to enhance CD4+ and CD8+ T cell responses in these patients, potentially leading to long term control of viremia and maintenance of CD4+ T cells.  This research follows the successful induction of anti-tumor immune responses in cancer patients treated with mRNA-transfected autologous dendritic cells in Phase I clinical studies.  This highly efficient vaccination protocol is able to induce potent CD4+ and CD8+ T cell responses against tumor antigens that were previously ignored by the immune system.  Similarly, in HIV vaccination the loading of monocyte derived dendritic cells with HIV antigen mRNA leads to an upregulation of IL-2 and Interferon gamma secretion by host T cells in vitro.  In collaboration with Dr. Eli Gilboa, our laboratory has begun pre-clinical work using HIV-positive patient samples to study in T cell responses after ex vivo loading of dendritic cells with mRNA encoding HIV-1 antigens, in preparation for a clinical trial of HIV therapeutic vaccines.  These studies will also explore the optimal formulation of antigen mRNA, mRNA transfection method, and dendritic cell maturation process which is likely to induce a T cell phenotype strong enough to control HIV viral load and pathology following vaccination.

2. Therapeutic vaccination against patient-specific HIV-1 viral quasispecies

Related to our work on HIV dendritic cell-based therapeutic vaccination, another challenge is to develop methods of HIV therapeutic vaccination that take into account the genetic instability of the HIV-1 virus.  In standard HIV vaccination protocols with a consensus antigen, the dominant epitopes targeted by a vaccine may not be present in a particular patient, or the resulting CTL immune pressure may induce viral variants to emerge that have lost this epitope.  To circumvent this problem, host dendritic cells will instead be loaded with mRNA derived from their own viral repertoire prior to vaccination, providing the patient with a proportional mix of their own particular viral quasispecies.   In ongoing pre-clinical studies, patient blood samples will be used to amplify HIV mRNA in vitro.  This mRNA mix will then be transfected into autologous dendritic cells to evaluate its effectiveness compared to consensus antigen. 

3. TNF Superfamily Ligands as Vaccine Adjuvants

Member of the TNF/TNFR superfamily are involved in the induction and regulation of cellular and humoral immune responses.  TNF superfamily ligands can induce the activation of a number of cell types including dendritic cells, B cells, and T cells. We are studying the use of CD40L and other members of the TNF Superfamily of ligands as immunostimulants and vaccine adjuvants.  Molecules of interest include CD40L, GITRL, OX40L, 4-1BBL, RANKL, CD70, BAFF, and LIGHT.  An important discovery has been the requirement by many TNF superfamily ligands for protein clustering to induce the optimal activation of the corresponding TNF superfamily receptor.   In order to induce clustering in a manner safe for vaccine development, we have fused the extracellular domains of TNF superfamily ligands with the body of spontaneously multimerizing proteins with trimeric arms, such as surfactant protein D (SP-D). The prototype of these molecules, SP-D-CD40L, shows special promise as a vaccine adjuvant and anti-tumor agent.  Current research is exploring the incorporation of these SP-D-TNF superfamily ligand fusion proteins into viral vector vaccines such as Ad5. By combining these molecular adjuvants with HIV-1 antigens we will determine the optimal adjuvant or combination of adjuvants able to induce potent long term immune responses in animal vaccine models.

Selected Publications

Stone, G. W., Barzee, S., Snarsky, V., Kee, K., Spina, C.A., Yu, X.-F., and Kornbluth, R.S. 2006. Multimeric Soluble CD40 Ligand and GITR Ligand as Adjuvants for Human Immunodeficiency Virus DNA Vaccines. J Virology 80(4):1762-1772.

Kornbluth, R.S. and Stone, G.W. 2006. Immunostimulatory combinations: Designing the next generation of vaccine adjuvants. J Leuk Biol. 80(5):1084-1102.

Stone, G. W., Barzee, S., Snarky, V., Spina, C.A., Lifson, J.D., Pillai, V.K., Amara, R.R., Villinger, F., and Kornbluth, R.S. 2006. Macaque Multimeric Soluble CD40 Ligand and GITR Ligand Constructs Are Immunostimulatory Molecules In Vitro.  Clin Vaccine Immunol. 13(11):1223-1230.

Kee, K., Truong, N.H., Snarsky, V., Barzee, B., Spina, C.A., Rhodes, J.D., Stone, G.W., and Kornbluth, R.S. Characterization of multimeric soluble forms of CD40L as stimulators of dendritic cells, macrophages, and B cells. In Preparation.

Stone, G.W., Barzee, S., Snarsky, V., Toppin, C., Tran, B., and Kornbluth, R.S.  Antitumor effects of local treatment with combinations of multimeric soluble CD40L DNA and TLR agonists.  In Preparation.