IMMUNOGLOBULIN SUBCLASSES: ROLES IN ACTIVITY OF IGIV AND IN ADVERSE REACTIONS

我们已经证实，热灭活的流产布鲁氏菌与HIV-1MN的V3环肽结合后，可以在正常和CD4T细胞耗尽的小鼠的系统和粘膜表面诱导中和抗体和CTL。在缺乏CD4T细胞的小鼠中产生的抗体主要是IgG2a亚型。这些小鼠的血清在中和HIV-1方面比以IgG1为主的血清更有效。此外，该结合物还能诱导恒河猴中和抗体(全身和粘膜)和细胞反应。包括阴道在内的几个粘膜部位的分泌物显示出抗HIV中和活性。此前，我们已经证明，以布鲁氏菌形式的强Th1刺激可以将Th2反应切换到Th1反应，并抑制IgE诱导。这些研究是在成年小鼠身上进行的。抗IL-12抗体处理或IFNG KO小鼠不能逆转热致死流产布鲁氏菌(BA)对卵白蛋白明胶(OVA/明胶)诱导的Th2样反应的下调，提示Th1细胞因子的诱导并不是BA介导的抑制OVA/明胶Th2应答的唯一机制。进行了一项研究，以确定是否有另一种途径涉及共刺激分子表达的变化。B7.2，而不是B7.1，在BA诱导的小鼠非T细胞和T细胞上表达上调。令人惊讶的是，BA诱导小鼠CD4和CD8T细胞CD28表达下调，B7.2表达上调。CD28和B7.2对T细胞的作用在40~48h达到最大，且不依赖于IL-12和干扰素-g。根据这些结果，我们认为IL-12/IFNG非依赖性地抑制Th2细胞对OVA/明矾的反应的作用次于BA对T细胞表面共刺激分子表达的影响。我们认为CD28在激活后下调可抑制Th0向Th2细胞的分化。此外，T细胞表面CD28的表达减少和B7.2的表达增加有利于B7.2与T细胞表面CTLA-4的相互作用，这可能为发育中的Th2细胞提供了负面信号。小鼠IgG2a是补体固定同功型。为了研究人补体结合抗体是否具有更强的中和病毒的能力，从呼吸道合胞病毒(RSVIG)高滴度个体中获得了多克隆抗体。该产物通过蛋白A柱，纯化成IgG3，并富含IgG2、IgG1和IgG4。进一步的纯化将涉及免疫亲和柱。初步数据表明，人IgG1在中和RSV方面比IgG3更有效。

We have established that heat-killed Brucella abortus conjugated to a V3-loop peptide from HIV-1 MN can elicit neutralizing antibodies and CTL in normal and mice depleted of CD4+ T-cells, systemically and at mucosal surfaces. The antibodies elicited in mice lacking CD4+ T-cells were mainly of the IgG2a isotype. Sera from these mice were more efficient than sera containing predominantly IgG1 in neutralizing HIV-1. Furthermore this conjugate can induce neutralizing antibody (systemic and mucosal) and cellular responses in Rhesus macaques. Secretions from several mucosal sites including vagina exhibited ant-HIV neutralizing activity. Previously, we have shown that a strong Th1 stimulus, in the form of Brucella abortus, can switch Th2 to Th1 responses and inhibit IgE induction. These studies were performed in adult mice. Down-regulation of the Th2-like response induced by ovalbumin-alum (OVA/ALUM)by heat-killed Brucella abortus (BA) was not reversed by anti-IL-12 antibody treatment or in IFNg KO mice, suggesting that induction of Th1 cytokines was not the only mechanism involved in the BA-mediated inhibition of the Th2 response to OVA/ALUM. A study was performed to determine whether an alternative pathway involved alteration in expression of costimulatory molecules. B7.2, but not B7.1, was up-regulated on mouse non-T and T-cells following BA. Surprisingly, BA induced down-regulation of CD28 and up-regulation of B7.2 on murine CD4+ and CD8+ T cells. These effects on T-cells were maximal for CD28 and B7.2 at 40-48 h, and were not dependent on IL-12 or IFN-g. On the basis of these results we propose that the IL-12/IFNg- independent inhibition of Th2 responses to OVA/ALUM are secondary to the effects of BA on expression of costimulatory molecules on T cells. We suggest that down-regulation of CD28 following activation inhibits subsequent differentiation of Th0 into Th2 cells. In addition, decreased expression of CD28 and increased expression of B7.2 on T cells would favor B7.2 interaction with CTLA-4 on T cells and this could provide a negative signal to developing Th2 cells. Mouse IgG2a is a complement-fixing isotype. In order to study whether human complement-fixing antibodies are more potent in neutralizing virus, polyclonal antibody has been obtained from individuals with high titer against respiratory syncytia virus (RSVIG). This product was passed over protein A columns and purified into IgG3 and enriched for IgG2, IgG1 and IgG4. Further purifications will involve immunoaffinity columns. Preliminary data suggest that human IgG1 is more effective than IgG3 in neutralizing RSV.