Sirko D A, Ehrlich G D
Department of Pathology, School of Medicine, University of Pittsburgh, Pennsylvania 15261, USA.
Virology. 1996 Apr 1;218(1):238-42. doi: 10.1006/viro.1996.0184.
Certain antibody neutralization escape mutants of HIV-1 map outside of the antibody recognition epitope, thereby suggesting the presence of nonlinear conformational domains. In an effort to begin to define the interacting regions of the HIV envelope proteins, a neutralization-sensitive clone of HIV-1, HXB2/BH10Sal-Bam, was passaged in the presence of the V3-specific monoclonal antibody 0.5beta. DNA sequence analysis of the V3 domain of the breakthrough viral populations revealed one population that retained the parental V3 genotype. Quantitative DNA sequence analysis of this breakthrough population revealed the presence of mutational "hotspots" in several envelope domains that are noncontiguous with V3. Mutations were seen throughout gp41 and the C1, V1/V2, C2, and C5 domains of gp120. In contrast, other regions of gp120, C3, V4, C4, and V5 remained totally unchanged. Within V1, three residues within a 14-amino acid stretch experienced five substitutions and in C5 three residues within a 7-amino acid stretch experienced four substitutions. This finding, that certain residues clustered within particular domains (V1/V2, C5, and gp41) experienced multiple substitutions under a defined environmental stressor, suggests that the degree of adaptive plasticity exhibited by the HIV envelope is limited. Based on this observation it may be possible, using a set of antibodies to various envelope epitopes, to discern a set of rules which explain the interactions of the various envelope domains with each other and with their environment. The insight gained into the physiologic constraints that the envelope proteins are subject to may be useful in developing therapeutic and vaccination strategies.
某些HIV-1抗体中和逃逸突变体定位于抗体识别表位之外，从而提示存在非线性构象域。为了开始确定HIV包膜蛋白的相互作用区域，将一株HIV-1中和敏感克隆HXB2/BH10Sal-Bam在V3特异性单克隆抗体0.5β存在的情况下传代培养。对突破性病毒群体的V3结构域进行DNA序列分析，发现有一个群体保留了亲本V3基因型。对该突破性群体进行定量DNA序列分析，发现在几个与V3不相邻的包膜结构域中存在突变“热点”。在gp41以及gp120的C1、V1/V2、C2和C5结构域中均发现了突变。相比之下，gp120的其他区域，即C3、V4、C4和V5则完全没有变化。在V1中，一个14个氨基酸片段内的三个残基发生了五次替换，在C5中，一个7个氨基酸片段内的三个残基发生了四次替换。这一发现，即在特定环境应激源作用下，特定结构域（V1/V2、C5和gp41）内聚集的某些残基发生了多次替换，表明HIV包膜所表现出的适应性可塑性程度是有限的。基于这一观察结果，有可能利用一组针对各种包膜表位的抗体，识别出一套规则，用以解释各种包膜结构域之间以及它们与环境之间的相互作用。对包膜蛋白所受生理限制的深入了解可能有助于制定治疗和疫苗接种策略。
