Transmission-blocking vaccine for HIV-1

精液中含有阳离子淀粉样纤维，来源于前列腺酸性磷酸酶(PAP)的蛋白水解性裂解片段，可有效捕获HIV-1颗粒。这些纤维被称为精液来源的病毒感染增强因子(SEVI)，可将HIV-1的传染性提高几个数量级。预计精液中的HIV-1病毒粒子将有效地与SEVI形成复合体，因此精液中传播的HIV-1可能对应于病毒-SEVI复合体。我们假设病毒-SEVI复合体将呈现不同于游离病毒粒子或传统重组抗原的新的抗原结构，并且病毒-SEVI复合体可以被靶向地开发出能够预防艾滋病毒通过精液传播的创新疫苗。通过靶向宿主蛋白和病毒之间的复合体，我们希望引发一种免疫反应，识别在精液中发现的HIV-1的真实形式，并潜在地绕过病毒抗原变异的问题。 提出了两个目标。在第一个目标中，我们将测试抗体是否可以阻断SEVI介导的HIV-1感染的增强。要做到这一点，我们将首先确定PAP残基，这是SEVI增强HIV-1传染性所必需的。这将通过测试产生淀粉样蛋白的PAP多肽的突变衍生物形成的纤维是否可以提高HIV-1感染的效率来实现。由于其他淀粉样原纤维(Aü)具有佐剂样的免疫刺激特性，我们还将测试这些突变的原纤维是否会诱导炎性细胞因子的产生。然后，我们将用SEVI或来自SEVI病毒结合表面的短线状肽免疫豚鼠，并测试所激发的抗体是否阻止SEVI介导的HIV-1感染性增强和/或SEVI介导的免疫激活。 在第二个目标中，我们将评估病毒-SEVI复合体或其模拟物是否可以诱导保护性的病毒中和抗体。为此，我们将组装SEVI和病毒颗粒之间的复合体，以及SEVI和寡聚体gp140(作为病毒-SEVI复合体的替代品)之间的复合体。然后，我们将使用竞争性抗体结合的ELISA法评估这些复合体的抗原性，并将结果与用游离gp140寡聚体或病毒颗粒获得的结果进行比较。在目标2B中，我们将用gp140-SEVI(或病毒-SEVI)复合体免疫豚鼠，并评估诱导的体液免疫反应(包括中和抗体)的强度和质量；结果将与单独接种gp140或SEVI的动物进行比较。最后，在目标2C中，我们将测试基于SEVI的疫苗是否对恒河猴具有免疫原性，以及它是否可以预防SIV的阴道传播。总的来说，这些研究将为我们提出的方法提供确凿的原则证明测试。

Semen contains cationic amyloid fibrils derived from proteolytic cleavage fragments of prostatic acid phosphatase (PAP) that efficiently capture HIV-1 particles. These fibrils have been termed semen-derived enhancer of viral infection (SEVI) and enhance HIV-1 infectivity by several orders of magnitude. It is expected HIV-1 virions in semen will efficiently form complexes with SEVI, and that the transmitted form of HIV-1 in semen may therefore correspond to virus-SEVI complexes. We hypothesize that virus-SEVI complexes will present novel antigenic structures, different from those present on free virions or conventional recombinant antigens, and that the virus-SEVI complex can be targeted to derive an innovative vaccine capable of protecting against HIV transmission via semen. By targeting the complex between a host protein and the virus, we expect to elicit an immune response that recognizes the authentic form of HIV-1, as it is found in semen, and – potentially – to circumvent the problem of viral antigenic variation. Two aims are proposed. In aim one, we will test whether antibodies can block SEVI-mediated enhancement of HIV-1 infection. To do this, we will first identify PAP residues essential for enhancement of HIV-1 infectivity by SEVI. This will be achieved by testing whether fibrils formed by mutated derivatives of the amyloidogenic PAP peptide can enhance the efficiency of HIV-1 infection. Since other amyloid fibrils (Aß) have adjuvant-like immunostimulatory properties, we will also test whether these mutated fibrils elicit the production of inflammatory cytokines. We will then immunize guinea pigs with SEVI, or with short linear peptides derived from the virus-binding surface of SEVI, and test whether the elicited antibodies prevent SEVImediated enhancement of HIV-1 infectivity and/or SEVI-mediated immune activation. In aim two, we will evaluate whether virus-SEVI complexes, or mimics thereof, can elicit protective, virusneutralizing antibodies. To do this, we will assemble complexes between SEVI and virus particles, and also between SEVI and oligomeric gp140 (as a surrogate for the virus-SEVI complex). We will then evaluate the antigenicity of these complexes using competitive antibody-binding ELISA assays and compare results to those obtained with free gp140 oligomers or virus particles. In Aim 2B, we will immunize guinea pigs with gp140-SEVI (or virus-SEVI) complexes and assess the strength and quality of the elicited humoral immune response (including neutralizing antibodies); results will be compared to animals receiving gp140 or SEVI alone. Finally, in Aim 2C, we will test whether a SEVI-based vaccine is immunogenic in rhesus macaques and whether it can protect against vaginal transmission of SIV. Collectively, these studies will provide a conclusive proof-of-principle test for our proposed approach.