Single Chain Complex Vaccines and Protective Immunity

描述（由申请人提供）：越来越多的人认为，艾滋病毒疫苗必须产生灭菌性免疫，才能有效防治艾滋病毒大流行。研制这种疫苗需要基于艾滋病毒包膜的免疫原，这些免疫原可提高多种免疫模式，包括广泛中和的抗体反应。为此，我们开发了gp120-CD4复合物的类似物，在单个嵌合多肽中包含HIV(BaL) gp120和CD4 D1D2序列。在最近的一项初步研究中，我们评估了含有恒河猴CD4序列的单链复合物（称为rhFLSC）在恒河猴体内的免疫原性。本研究表明：1)rhFLSC在4只接种动物中有3只产生了广泛中和抗体。因此，当CD4片段相对于接种者是自体的时，单链复合物能够引发广泛中和的抗体。2)接种rhFLSC疫苗可对异源R5 SHIV（SHIV(162P3)）的直肠攻击提供非灭菌的“保护”。具体来说，与初始对照相比，300 ug rhFLSC四次免疫引起的免疫应答介导急性后血浆病毒血症的加速清除和血浆和组织病毒血症的持续抑制。这种保护似乎与rhFLSC免疫原引起的多种免疫模式有关。3)单独免疫可溶性CD4的对照组与未免疫对照组的攻毒结果无差异。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是由于交叉反应性抗包膜反应。因此，我们的假设是，通过改良的疫苗接种方案，这些反应的扩增将导致对异源粘膜攻击的灭菌免疫。实现这种保护将是研制艾滋病毒亚单位疫苗方面的一项重要进展，特别是如果还确定了这种保护的免疫相关因素。我们的假设将在两个具体目标中得到检验。目标1将是给动物接种高剂量（300微克）的rhFLSC疫苗，预计将提高应答，超过在试点研究中获得的应答。然后，接种疫苗的动物将接受R5 SHIV162P3的直肠攻击，以评估保护作用。目的2将是表征细胞和体液抗包膜反应的动物，以确定相关的保护。

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.