The development of a safe and effective vaccine against HIV-1 is critical for curtailing the spread of a primarily sexually transmitted disease that is now affecting more than 30 million persons worldwide. While a recent poxvirus-protein immunogen efficacy trial conferred modest protection from acquisition, the correlates of protection are unknown. In the SIV infection model in Rhesus macaques, up to 70% of animals, vaccinated with GM-CSF enhanced DNA priming, MVA boosted, then subjected to a heterologous (E660), multiple low dose rectal challenge, were protected from acquisition and a clear correlate of protection was E660 Env binding antibody avidity. The Emory Consortium for B-Cell Biology of Mucosal Immune Protection from SIV Challenge, using highly collaborative approaches, will define through advanced immunological and systems biology approaches the underlying mechanisms for enhanced antibody avidity and protection. The Consortium will incorporate four research projects and four science support cores, in addition to an Administrative core to achieve this goal. Project 1 will identify the mechanisms by which GM-CSF mediates enhanced protection from low dose SIV vaginal challenge, and will determine whether addition of an optimized protein boost further enhances protection. Project 2 will investigate the potential and underlying mechanism for TLR-4 and TLR-7 ligands, delivered in a novel synthetic nanoparticle formulation and recently shown to dramatically improve antibody responses to influenza HA, to enhance the quality of protective mucosal B-cell and T-cell responses to SIV VLPs. Project 3 will determine the effects of GM-CSF and nanoparticle delivered TLR ligand adjuvants on follicular T-cells and their function in molding the quality of the humoral immune response, while Project 4 will similarly investigate the potential for these adjuvanting approaches to activate a subset of IL-21 producing N{BH} neutrophils equipped with B cell helper function. The projects will be supported by an NHP Core, which will provide and maintain genetically characterized female macaques for the studies. Additional Cores will allow characterization of the antiviral antibody response at the level of single cells and mucosal secretions, and a B-cell biomarker core will develop unique reagents for defining the B-cell response in this rhesus model. The Administrative Core will ensure effective communication and collaboration between projects and Cores through database and repository management and will be responsible for maintaining timelines, fiscal responsibility, and dissemination of research results.
The Emory Consortium for B-Cell Biology of Mucosal Immune Protection from SIV Challenge will define and characterize the mechanistic basis for enhanced protection from acquisition of SIV infection, and will explore novel approaches to increase further the level of protection. Results from these studies will be directly applicable to HIV vaccine development in human subjects. Project 1: Immune Correlates for GM-CSF Mediated Enhancement of Vaccine Efficacy (Project Leader Rama Amara) Description as provided by applicant: The acquired immunodeficiency syndrome caused by HIV-1 is the leading cause of death in Africa and the fourth leading cause of death worldwide. The recent RV144 phase-3 trial (Thai trial) testing the efficacy of an AIDS vaccine consisting of a poxvirus vector (ALVAC) prime and protein boost demonstrated a modest efficacy where 25% of the vaccinated individuals were protected from HIV-1 infection. These results are highly encouraging;however the immune correlates for this protection are yet to be identified but suggest a role for non-neutralizing Ab in protection. Furthermore, the protection in the Thai trial appeared to be short lived (for the first six months) and there is a need for developing approaches that sustain immunological memory of vaccine elicited responses. Our ongoing studies in rhesus macaques demonstrated a similar protection from heterologous repetitive mucosal SIV challenges by a DNA prime and poxvirus (modified vaccinia Ankara) boost vaccine (DNA/MVA). In addition, co-delivery of granulocyte and macrophage colony stimulating factor (GM-CSF) DNA with our vaccine DNA significantly enhanced the protection mediated by the DNA/MVA vaccine from 25% to 70%. GM-CSF did not adjuvant the anti-viral CD8 T cell responses but enhanced the avidity of binding Ab specific to the Env and promoted generation of anti-viral IgA in rectal secretions. Importantly, the avidity of binding Ab against the challenge virus Env strongly correlated with enhanced protection against acquisition of SIV infection. These and results from other studies highlight an important role for other non-neutralizing activities of antibody in protection. The overall goals of this project are to identify the mechanisms of GM-CSF-mediated enhancement of protection against a mucosal SIV challenge and to test the effect of a protein boost for enhancing this protection against acquisition of heterologous repetitive intravaginal SIV challenges in rhesus macaques. In our specific aim 1, we will investigate the immune correlates for GM-CSF mediated enhanced protection. Here we will test the hypothesis that GM-CSF enhances the breadth, avidity, cytolytic activity and mucosal homing of anti-Env binding Ab in serum and mucosal secretions by modulating function of antigen presenting cells and T helper responses. In our specific aim 2, we will test whether addition of a protein boost, adjuvated with either alum or a combination of toll-like receptor ligands encapsulated in nanoparticles, to the GM-CSF-adjuvanted DNA/MVA vaccine will further enhance the longevity of protective immunity against acquisition of heterologous repetitive intravaginal SIV challenge.
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