Zhang Peng Fei, Bouma Peter, Park Eun Ju, Margolick Joseph B, Robinson James E, Zolla-Pazner Susan, Flora Michael N, Quinnan Gerald V
Department of Preventive Medicine and Biometrics, Biomedical Instrumentation Center, Uniformed Services University of the Health Sciences, Bethesda 20814, USA.
J Virol. 2002 Jan;76(2):644-55. doi: 10.1128/jvi.76.2.644-655.2002.
The human serum human immunodeficiency virus type 1 (HIV-1)-neutralizing serum 2 (HNS2) neutralizes many primary isolates of different clades of HIV-1, and virus expressing envelope from the same donor, clone R2, is neutralized cross-reactively by HIV-immune human sera. The basis for this cross-reactivity was investigated. It was found that a rare mutation in the proximal limb of variable region 3 (V3), 313-4 PM, caused virus pseudotyped with the R2 envelope to be highly sensitive to neutralization by monoclonal antibodies (MAbs) directed against conformation-sensitive epitopes at the tip of the V3 loop, such as 19b, and moderately sensitive to MAbs against CD4 binding site (CD4bs) and CD4-induced (CD4i) epitopes, soluble CD4 (sCD4), and HNS2. In addition, introduction of this sequence by mutagenesis caused enhanced sensitivity to neutralization by 19b, anti-CD4i MAb, and HNS2 in three other primary HIV-1 envelopes and by anti-CD4bs MAb and sCD4 in one of the three. The 313-4 PM sequence also conferred increased infectivity for CD4(+) CCR5(+) cells and the ability to infect CCR5(+) cells upon all of these four and two of these four HIV-1 envelopes, respectively. Neutralization of R2 by HNS2 was substantially inhibited by the cyclized R2 V3 35-mer synthetic peptide. Similarly, the peptide also had some lesser efficacy in blocking neutralization of R2 by other sera or of neutralization of other primary viruses by HNS2. Together, these results indicate that the unusual V3 mutation in the R2 clone accounts for its uncommon neutralization sensitivity phenotype and its capacity to mediate CD4-independent infection, both of which could relate to immunogenicity and the neutralizing activity of HNS2. This is also the first primary HIV-1 isolate envelope glycoprotein found to be competent for CD4-independent infection.
人血清人免疫缺陷病毒1型（HIV-1）中和血清2（HNS2）可中和多种不同HIV-1分支的原代分离株，且来自同一供体的克隆R2表达包膜的病毒可被HIV免疫的人血清交叉中和。对这种交叉反应性的基础进行了研究。结果发现，可变区3（V3）近端臂中的一个罕见突变，即313-4 PM，导致以R2包膜假型化的病毒对针对V3环顶端构象敏感表位的单克隆抗体（MAb）（如19b）高度敏感，对针对CD4结合位点（CD4bs）和CD4诱导（CD4i）表位的MAb、可溶性CD4（sCD4）和HNS2中度敏感。此外，通过诱变引入该序列会导致另外三种原代HIV-1包膜对19b、抗CD4i MAb和HNS2的中和敏感性增强，在这三种包膜中的一种中对抗CD4bs MAb和sCD4的中和敏感性增强。313-4 PM序列还分别赋予了这四种HIV-1包膜中的全部四种以及其中两种感染CD4(+) CCR5(+)细胞的能力增强以及感染CCR5(+)细胞的能力。HNS2对R2的中和作用被环化的R2 V3 35聚体合成肽显著抑制。同样，该肽在阻断其他血清对R2的中和或HNS2对其他原代病毒的中和方面也有一些较小的效果。总之，这些结果表明，R2克隆中不寻常的V3突变解释了其不寻常的中和敏感性表型及其介导不依赖CD4感染的能力，这两者都可能与HNS2的免疫原性和中和活性有关。这也是发现的首个能够进行不依赖CD4感染的原代HIV-1分离株包膜糖蛋白。
