Immunoglobulin subclasses: roles in activity of IGIV and in adverse reactions

我们已经证实，热杀死的流产布鲁氏菌与HIV-1 MN的V3环肽结合，可以在正常和CD4+ t细胞枯竭的小鼠中全身和粘膜表面引发中和抗体和CTL。在缺乏CD4+ t细胞的小鼠中引发的抗体主要是IgG2a同型。这些小鼠的血清比主要含有IgG1的血清更有效地中和HIV-1。此外，该偶联物还能诱导恒河猴的中和抗体（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表现出抗hiv中和活性。为了确定IgG亚类在中和HIV-1的能力上是否存在差异，将多克隆HIVIG传递到蛋白A柱上，并收集相应的部分，结果显示IgG1、IgG2和IgG3的纯度为> 89% （IgG4的含量不足以进行研究）。所有三个亚类都显示与所有主要HIV-1蛋白（IgG1 >IgG2 > IgG3）结合。相比之下，通过合胞抑制和无细胞病毒中和（IgG3 > IgG1 > IgG2）检测，IgG3比其他亚类在中和HIV-1的能力上更活跃。HIVIG及其亚型对病毒的中和能力也依赖于病毒株，因此嗜T细胞病毒（R4）比嗜巨噬细胞病毒（R5）更敏感。IgG3与IgG1和IgG2的不同之处在于其铰链区域更长且更灵活。为了检验这在中和病毒中是否重要，IgG部分将被木瓜蛋白酶消化成Fc和Fab片段，并检测Fab片段的活性。这些发现对hiv的生产和临床使用具有启示意义。此外，他们认为HIV-1疫苗应该诱导高滴度IgG3反应。

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. To determine whether IgG subclasses differ in their ability to neutralize HIV-1, polyclonal HIVIG was passed over protein A columns and the appropriate fractions collected and shown to be > 89% pure IgG1, IgG2 and IgG3 (IgG4 was not present in sufficient quantities for study). All three subclasses showed binding to all major HIV-1 proteins (IgG1 >IgG2 > IgG3). In contrast, IgG3 was more active than other subclasses in its ability to neutralize HIV-1 as assayed by syncytia inhibition and cell- free virus neutralization (IgG3 > IgG1 > IgG2). The ability of HIVIG and the subclasses to neutralize viruses also depended on the virus strain, so that T cell tropic (R4) were more susceptible than Macrophage tropic (R5) viruses. IgG3 differs from IgG1 and IgG2 by virtue of a longer and more flexible hinge region. To test whether this is important in neutralizing virus, the IgG fractions will be digested by papain into Fc and Fab fragments and the Fab fragments tested for activity. These findings have implications for manufacture and clinical use of HIVIG. Moreover they suggest that HIV-1 vaccines should induce high titer IgG3 responses.