Single Chain Complex Vaccines and Protective Immunity

描述(由申请者提供)：越来越多的人达成共识，认为艾滋病毒疫苗必须引起灭菌免疫，才能有效地对抗艾滋病毒大流行。这种疫苗的开发需要基于HIV包膜的免疫原能提高多种免疫模式，包括广泛中和抗体反应。为此，我们开发了gp120-CD4复合体的类似物，它在单个嵌合多肽中包含HIV(Bal)gp120和CD4D1D2序列。在最近的一项初步研究中，我们评估了包含恒河猴CD4序列的单链复合体(指定为rhFLSC)在恒河猴中的免疫原性。本研究表明：1)在四种疫苗接种的动物中，有三种产生了广泛的中和抗体。因此，当CD4部分相对于接种对象是自体的时，单链复合体能够引起广泛的中和抗体。2)外源R5SHV(SHIV(162P3))对直肠攻击具有非灭菌保护作用。具体地说，与单纯对照相比，与未接种的对照相比，四次注射300ug的重组人外周血细胞可促进急性血浆病毒血症的清除，并持续抑制血浆和组织的病毒血症。这种保护似乎与重组人外周血细胞免疫原提高的多种免疫模式有关。3)单独用可溶性CD_4免疫的对照组动物的挑战结果与未免疫的对照组没有差别。基于这些发现，我们得出结论，我们在rhFLSC免疫的猕猴中观察到的保护作用是由于交叉反应的抗包膜反应。因此，我们的假设是，通过改进的疫苗接种方案放大这些反应将导致对异种黏膜攻击的灭菌免疫。实现这种保护将代表着艾滋病毒亚单位疫苗开发的重要进展，特别是如果保护的免疫相关性也得到确立的话。我们的假设将在两个具体目标上得到检验。目标1将是给动物接种高剂量(300微克)的重组人肝干细胞，预计将提高反应，超过在初步研究中获得的反应。然后，接种疫苗的动物将接受R5 SHIV162P3的直肠挑战，以评估保护效果。目标2将表征动物的细胞和体液抗包膜反应，以确定保护的相关因素。

DESCRIPTION (provided by applicant): There is a growing consensus that an HIV vaccine must elicit sterilizing immunity in order to be effective against the HIV pandemic. The development of such a vaccine requires HIV envelope-based immunogens that raise multiple modes of immunity including broadly neutralizing antibody responses. Towards this end, we have developed analogues of the gp120-CD4 complex that contain HIV(BaL) gp120 and CD4 D1D2 sequences within a single chimeric polypeptide. In a recent pilot study, we evaluated the immunogenicity a single chain complex containing rhesus macaque CD4 sequences (designated rhFLSC) in rhesus macaques. This study showed that: 1) rhFLSC elicited broadly neutralizing antibodies in three of four vaccinated animals. Thus, a single chain complex is capable of eliciting broadly neutralizing antibodies when the CD4 moiety is autologous with respect to the vaccinated subject. 2) Vaccination with rhFLSC afforded nonsterilizing "protection" against rectal challenge with a heterologous R5 SHIV (SHIV(162P3)). Specifically, immune responses raised by four immunizations with 300 ug of rhFLSC mediated accelerated clearance of post-acute plasma viremia and sustained suppression of plasma and tissue viremia compared to naive controls. This protection appeared to be associated with multiple modes of immunity raised by the rhFLSC immunogen. 3) Challenge outcome in a control group of animals immunized with soluble CD4 alone was no different from the naive control group. Based on these findings, we conclude that the protection we observed in rhFLSC-immunized macaques was due to cross-reactive anti-envelope responses. Accordingly, our hypothesis is that the amplification of these responses by a modified vaccination protocol will lead to sterilizing immunity against heterologous mucosal challenge. The attainment of such protection would represent an important advance in the development of HIV subunit vaccines, particularly if immune correlates of the protection were also established. Our hypothesis will be tested in two Specific Aims. Aim 1 will be to vaccinate animals with high doses (>300 ug) of rhFLSC that are expected to boost responses above what were obtained in the pilot study. Vaccinated animals will then receive a rectal challenge with the R5 SHIV162P3 to assess protection. Aim 2 will be to characterize cellular and humoral anti-envelope responses in the animals in order to identify correlates of protection.