Virtual Institute on Poverty Related Diseases



DESCRIPTION (provided by applicant): While results from the RV144 vaccine efficacy trial were encouraging, protection was modest and not sustained. An emerging picture of desirable characteristics of candidate HIV vaccines include one that induces a sustained response that includes broadly neutralizing antibodies (bnAbs), non- neutralizing antibodies including those that mediate ADCC as well as strong virus-specific memory T cells. Results from attenuated virus studies, CMV-vectored SIV/HIV vaccines and analysis of antibody maturation over time all suggest that ongoing viral antigen expression may be an essential component to drive a mature and broad response. Integrase defective lentiviral vectors (IDLV) engineered with safety features that prevent integration and replication result in prolonged antigen expression with robust and sustained T and B cell responses in mice and non-human primates (NHP). This Program Project Grant combines the unique features of IDLV with recent immunogen design strategies aimed at promoting maturation of an effective immune response over time and will be studied in the NHP model. IDLV will be engineered to express a series of Envelope immunogens based on the recently described CH505 transmitted/founder envelope and a series of subsequent variants derived from an individual that developed CD4-binding site bnAbs. An administrative core (Core A) will assure that the proposed scientific plan is effectively carried ot and an NHP core (Core B) which will oversee two NHP protocols and perform quantitative and qualitative T cell assays in support of two projects. Project 1 will develop and validate IDLV engineered to express the Env immunogens and will define the mechanisms that uniquely sustain antigen expression. In vitro and in vivo testing will determine vector and expression durability, integration state and ability to mobilize vector-based virus. Project 2 will determine he systemic and mucosal B cell responses including neutralization and ADCC (against bnAb-associated epitopes) and isolate and characterize monoclonal antibodies over time two vaccine arms. These studies will test the hypothesis that persistent expression of strategically chosen envelopes will lead to maturation and broadening to an effective immune response.

Anticipated Outcome

PUBLIC HEALTH RELEVANCE: There remains a need for an HIV vaccine that gives an effective and durable protection. This Program Project Grant combines a strategy of persistent antigen expression in an engineered non- integrating lentiviral vector (durable) with insertion of HIV envelope antigens with the goal of promoting the maturation of an effective and broad immune response. Project-001: Safety and Durability of Integrase Defective Lentiviral vector for an HIV Vaccine Project Leader (PL): Klotman, M. DESCRIPTION (provided by applicant): The overall goal of this HIVRAD application is to provide the scientific basis for the development of Integration- Defective Lentiviral Vectors (IDLV) with a strategic immunogen as an improved delivery system for HIV antigens that will lead to an effective HIV vaccine. The central hypothesis is that delivery of novel envelope immunogens via IDLV results in safe and sustained expression of the antigen in vivo, allowing induction of long-term antigen-specific response, including maturation of broadly neutralizing antibodies (bnAbs). Project 1 will focus on components by addressing safety (non-integrating and non-replicating), sustained antigen expression and the durability of the immune response. Preliminary data obtained following a single injection using a SIV-based IDLV in non-human primates (NHP) has demonstrated for the first time prolonged, high humoral and cellular responses, setting the stage for further evaluation of this promising antigen delivery system in NHP. Specific aim 1 will construct, produce and validate each batch of the IDLV vaccine preparation before in vivo immunization by determining antigen expression, non-integration in vitro and absence of replication competent lentivirus (RCL) in vitro. Specific aim 2 will focus on demonstrating the persistence and safety of IDLV in vivo in NHP. RNA and protein expression of HIV envelopes will be assessed over time following intramuscular delivery in NHP (protocol A, Core B). The in vivo safety of the vector will be assessed using sensitive assays to determine integration status and the absence of RCLs in vivo. Specific aim 3 will use the murine system to evaluate biodistribution, safety, persistence of antigen expression and presentation after intramuscular immunization with IDLV and to identify cells expressing the transgene in vivo. Analysis of innate and adaptive immune response both locally (at the site of injection) and systemically (spleens and LN) will be correlated with duration of antigen expression to understand the basis of IDLV-induced persistence of immune response. Information derived from this project will be integrated with antibody maturation analysis (project 2) to determine the full potential of an IDLV-based strategy for a HIV vaccine.