The recent RV144 clinical vaccine trial induced modest and transient protection in healthy individuals against HIV-1 infection, and is considered to be a marginal success. To improve the efficacy and duration of the antibody (Ab) response, better immunogens are required. We postulate that Abs induced by novel vaccine constructs will have higher specific activity, with stronger Ab titers and, within the total Ab response, a greater proportion of the Abs needed for protection. Such novel constructs, which could present viral epitopes in a context other than that of the whole envelope (Env), may also obviate the problems of the transient Ab response associated with whole Env. We and other have demonstrated that, by focusing the Ab response on V3, cross-clade neutralizing Abs are elicited which are detectable >1 year after immunization. Therefore, we now propose to extend the platform we previously developed for designing and developing V3-scaffold immunogens in order to create and test new epitope-scaffold protein immunogens that will focus the Ab response on two additional sites of vulnerability in Env: the V2 loop and the cluster of quaternary neutralizing epitopes (QNEs) composed of portions of V2 and V3. The HIVRAD will be composed of: Project 1: Vaccines to Induce Functional Abs Targeting the V2 Loop; Project 2: Rational Design of Immunogens Targeting the HIV-1 V2/V3 Quaternary Neutralizing Epitopes; Core A: Administrative Core; Core B: Protein Production Core; and, Core C: Animal Studies Core. The epitope-scaffold immunogens to be developed can be used individually or in combination, and will constitute powerful new tools for inducing broad and potent protective Abs. Many of the participants have worked together for >20 years to develop and characterize >100 human mAbs to HIV and other pathogens. Recently, the team has worked collaboratively and synergistically, preparing and analyzing >25 crystals of monoclonal Abs (mAbs) and mAb/epitope complexes, developing DNA Env primes and epitope-scaffold immunogens, and performing immunization experiments. Our experience places us in a strong position to extend our studies to epitopes that only recently have been recognized as important for protection from HIV infection. By the completion of the proposed Program, we plan to have identified epitope-targeting immunogens and immunization protocols that will generate Abs with protective anti-viral functions directed specifically toward the conserved regions of the V2 loop and the V2/V3 quaternary neutralizing epitopes of HIV-1 gp120.
Current data suggest an HIV vaccine will need to induce Abs with potent and broad anti-viral activities as well as cell mediated immunity. Vaccines made with whole envelope proteins have not yet achieved this goal; therefore, new immunogens are needed. In this Program Project Grant we will develop vaccine candidates that focus the immune response on portion of the virus that induce protective Abs. Project 1 - Vaccines to Induce Functional Antibodies Targeting the V2 Loop Project Leader: Susan Zolla-Pazner (Description as provided by applicant) The various forms of the HIV-1 envelope (Env) glycoproteins do not serve as ideal immunogens because they poorly induce Abs (Abs) with broad antiviral functions, and the Ab response lasts less than 6 months. To overcome these limitations, epitope-scaffold immunogens can be used to focus the Ab response on vulnerable sites on the Env; however, the design of HIV epitope-scaffold immunogens has been fraught with many failures. Nevertheless, epitope-scaffold vaccines candidates have been successfully developed against influenza and Neisseria, and we and others have succeeded in designing several V3-scaffold and V3 peptide immunogens with demonstrable antigenicity and immunogenicity, resulting in the induction of HIV-1 cross-clade neutralizing Abs. In this Project, we propose to focus the immune response on the V2 region of gpl20. Until recently, this region was virtually overlooked as a target for vaccine development, but its importance as a vaccine target has been recently supported by data showing that anti-V2 Abs can be highly cross-reactive, display neutralizing activity, capture virus particles, and block gp120/a4p7 interaction. Support for pursuing V2 as a promising antigen for vaccine design also comes from pilot studies with specimens from the RV144 clinical vaccine trial. For this Project, we will apply the platform we developed for generating V3-scaffold immunogens to the production of V2-scaffold immunogens to be used for boosting the Ab response after priming with DNA Env. For Aim 1.1, we will construct V2 inserts for scaffolded immunogens based on the fine specificity of human V2 polyclonal and monoclonal Abs (mAbs), and on bioinformatics and molecular modeling data. In Aim 1.2, we will assess the prevalence and function of anti-V2 Abs of different specificities and clarify how these differ relative to the infecting HIV clade. For Aim 1.3, we will select and characterize new human V2-specific mAbs derived from non-clade B-infected donors from Cameroon infected with the clades that induce the most broad and functional anti-V2 Abs. Finally, after selecting V2-scaffold proteins which, from the results of Aim 1.2 and 1.3, react wit the most broad, potent and multifunctional anti-V2 polyclonal and mAbs, we will, in Aim 1.4, test the immunogenicity of selected V2 scaffold boosting immunogens in rabbits and non-human primates after priming with Env DNA. The ultimate goal of this Project is to induce antl-V2 Abs in rabbits and non-human primates that display cross-clade antiviral activities that mediate protection. RELEVANCE: Novel concepts are needed to develop an effective HIV vaccine. This project's goal is to design new HIV epitope-scaffold vaccines that will focus the host immune response on vulnerable sites on the V2 loop of the virus envelope glycoprotein. The project will provide important data that will advance the development of a more effective HIV vaccine.
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