PHENOTYPIC AND GENOTYPIC DETERMINANTS OF SHIV PATHOGENESIS

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 研究猴-人免疫缺陷病毒SHIV（SF 162 P3 N）中使用CCR 5（R5）的病毒辅助受体转换为使用CXCR 4（X4）的病毒的途径。  感染的恒河猴BR 24，对感染后20周存在的变体进行分析，该时间是首次通过PCR检测到X4开关变体的标志性gp 120 V3环序列的时间。出乎意料的是，具有His/Ile而不是特征性X4 V3 His/Arg插入的循环和组织变体在该时间点占主导地位。对包膜蛋白（Env）的V5可变环的C2保守区序列的系统发育分析表明，携带HI插入的病毒代表了亲本SHIV（SF 162 P3 N）和最终X4 HR开关变体之间的进化中间体。功能分析表明，Hl变体也是表型中间体，能够使用CCR 5和CXCR 4两者用于进入。然而，R5 X4中间病毒进入表达CCCR 5的靶细胞的效率低于亲本R5毒株，并且对CCR 5和CXCR 4抑制剂的敏感性高于亲本R5或最终X4病毒。它也比亲本R5病毒对抗体中和更敏感，特别是对针对CD 4结合位点的试剂，但不如晚期X4病毒敏感。值得注意的是，决定CXCR 4使用的V3环序列也赋予可溶性CD 4中和敏感性。总的来说，这些数据表明，类似于人类免疫缺陷病毒1型（HIV-1）感染的个人，从CCR 5到CXCR 4的使用在BR 24过渡的演变通过一个中间阶段，减少病毒进入和辅助受体的使用效率。这些数据进一步支持了一个模型，该模型将开放的包膜gp 120构象、更好的CD 4结合和CXCR 4使用的扩展联系起来。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. To examine the pathway of the coreceptor switching of CCR5- using (R5) virus to CXCR4-using (X4) virus in simian-human immunodeficiency virus SHIV(SF162P3N)  infected rhesus macaque BR24, analysis was performed on variants present at 20 weeks postinfection, the time when the signature gp120 V3 loop sequence of the X4 switch variant was first detected by PCR. Unexpectedly, circulating and tissue variants with His/Ile instead of the signature X4 V3 His/Arg insertions predominated at this time point. Phylogenetic analysis of the sequences of the C2 conserved region to the V5 variable loop of the envelope (Env) protein showed that viruses bearing HI insertions represented evolutionary intermediates between the parental SHIV(SF162P3N) and the final X4 HR switch variant. Functional analyses demonstrated that the HI variants were phenotypic intermediates as well, capable of using both CCR5 and CXCR4 for entry. However, the R5X4 intermediate virus entered CCCR5- expressing target cells less efficiently than the parental R5 strain and was more sensitive to both CCR5 and CXCR4 inhibitors than either the parental R5 or the final X4 virus. It was also more sensitive than the parental R5 virus to antibody neutralization, especially to agents directed against the CD4 binding site, but not as sensitive as the late X4 virus. Significantly, the V3 loop sequence that determined CXCR4 use also conferred soluble CD4 neutralization sensitivity. Collectively, the data illustrate that, similar to human immunodeficiency virus type 1 (HIV-1) infection in individuals, the evolution from CCR5 to CXCR4 usage in BR24 transitions through an intermediate phase with reduced virus entry and coreceptor usage efficiencies. The data further support a model linking an open envelope gp120 conformation, better CD4 binding, and expansion to CXCR4 usage.