Do Early Maternal Antibodies Facilitate Oral Transmission of HIV in Infants?

描述（由申请人提供）：我们试图在母乳传播模型中研究婴儿恒河猴（RMs）口服暴露于R5 SHIV后病毒进入和早期粘膜扩散。这种母婴传播途径在发展中国家仍然存在问题。在其他参数中，牛奶传播的MTCT的风险与乳血清中的病毒载量有关。然而，尚不清楚传播的病毒粒子是否被母源抗体（Abs）覆盖，如果是，是否电离影响病毒粒子的感染性以及第一个有效感染的靶细胞的类型和/或数量。由于许多护理期HIV阳性妇女血清呈阳性，病毒粒子可能被活化。最近提出了抗体介导的增强HIV获取的可能性。Willey等人[2011]表明，近期感染HIV的个体的血清尚未对自身病毒产生抗体，在补体存在的情况下，体外HIV感染的毒性显著增强，高达350倍。IgG和IgM介导了这种作用。在新生儿RMs中使用SHIV挑战，我们已经产生了概念证明，口服病毒传播完全可以通过广泛中和的单克隆抗体（bnmab）被动免疫来预防。我们现在试图验证一种假设，即在扁桃体病毒应用于RM婴儿后，与非中和抗体（non- nab）偶联的病毒粒子将与携带fcr或携带补体受体（CR）的细胞相关。这反过来又与扁桃体和邻近口腔粘膜组织和淋巴结中大量的病毒+细胞有关。我们还假设婴儿RMs的非nab被动免疫会增加他们在口服SHIV暴露后对病毒血症的易感性。具体目标是：1。检查在HIV分支C阳性妇女的母乳和R5分支C SHIV（称为SHIV-C）感染rm的母乳中发现的病毒粒子的物理状态。我们将使用病毒粒子免疫复合物捕获试验来测试病毒粒子是否被Ab包被，以及这些病毒粒子是否在体外与fcr和携带cr的细胞结合。2. 通过扁桃体将婴儿RMs暴露于标准培养基中制备的荧光标记病毒或用非nab修饰的病毒后，鉴定和枚举第一个病毒靶细胞。这些研究将使用单周期病毒粒子进行标记，用绿色或红色荧光蛋白+/-与RM非nab偶联。3. 检测从早期感染R5 SHIV-C感染的RM（在形成nab之前）中分离的非中和IgG被动免疫RM婴儿是否会增加婴儿对口服R5 SHIV-C攻击的易感性。我们将使用终点滴定法来确定口服攻击的初生婴儿与在病毒攻击前被动免疫非中和IgG的婴儿的最小感染病毒剂量。这一建议意义重大，因为它侧重于口服传播和opsonized病毒的传播，鉴于大多数受感染的哺乳期妇女血清呈阳性，这是最可能参与母乳传播的艾滋病毒的形式。

DESCRIPTION (provided by applicant): We seek to study virus entry and early mucosal spread after orally exposing infant rhesus monkeys (RMs) to an R5 SHIV in a model of breast milk transmission. This route of mother-to-child transmission (MTCT) continues to be problematic in developing countries. The risks of milk-borne MTCT have been linked to viral loads in lactoserum, among other parameters. It is not known, however, whether transmitted virions are covered by maternal antibodies (Abs), and if so, whether opsonization influences virion infectivity as well as the types and/or numbers of the first productively infected target cels. Since many nursing HIV+ women are seropositive, virions are likely opsonized. The possibility of Ab-mediated enhancement of HIV acquisition was raised recently. Willey et al. [2011] showed that sera from individuals with recent HIV infection, who had not yet developed nAbs to autologous virus, rendered HIV infection in vitro significantly more virulent in the presence of complement - up to 350-fold. The effect was mediated by IgG and IgM. Using SHIV challenges in neonatal RMs, we have generated proof-of-concept that oral virus transmission is completely preventable by passive immunization with broadly neutralizing monoclonal antibodies (bnmAbs). We now seek to test the hypothesis that virions opsonized with non-neutralizing Abs (non-nAbs) will be associated with FcR-bearing or complement receptor (CR)-bearing cells after tonsilar virus application in RM infants. This in turn will be associated with a larger number of virus+ cells in the tonsils and adjacent oral mucosal tissues and lymph nodes. We also postulate that passive immunization with non-nAbs of infant RMs will increase their susceptibility to viremia after oral SHIV exposure. The Specific Aims are to: 1. Examine the physical status of virions found in breast milk of HIV clade C-positive women and in milk of R5 clade C SHIV (termed SHIV-C)-infected RMs. We will test whether virions are Ab coated using virion- immune complex capture assays and whether such virions bind to FcR-and CR-bearing cells ex vivo. 2. Identify and enumerate the first virus target cells after exposing infant RMs via the tonsils to fluorescently labeled virus prepared either in standard culture medium or opsonized with non-nAbs. These studies will be conducted with single-cycle virions labeled either with green or red fluorescent proteins +/- opsonization with RM non-nAbs. 3. Test whether passive immunization of RM infants with non-neutralizing IgG isolated from R5 SHIV-C- challenged RMs with early-stage infection (before developing nAbs) will increase the infants' susceptibility to oral R5 SHIV-C challenge. We will use endpoint titration to determine the minimal infectious virus dose in orally challenged naive infants versus infants passively immunized with non-neutralizing IgG prior to virus challenge. The proposal is significant due to its focus on oral transmission and spread of opsonized virus, the most likely form to be involved in milk-borne HIV transmission given that most infected, lactating women are seropositive.