Department of Virology and Preventive Medicine, Gunma University Graduate School of Medicine, Showa-machi, Maebashi, Gunma-371-8511, Japan.
Microbiol Immunol. 2013 Jun;57(6):437-44. doi: 10.1111/1348-0421.12051.
Human immunodeficiency viruses initiate infections via CCR5 coreceptors and then change their tropism to C-X-C chemokine receptor type 4 (CXCR4), this change being associated with rapid disease progression. HIV-1IIIB, a widely described pure X4-tropic strain, is distinct from R5X4-tropic viruses. In this study, the requirement for amino terminal regions (NTRs) of CXCR4 for entry of HIV-1IIIB virus into host cells was examined and compared to that of R5X4-tropic viruses. CXCR4 and its deletion mutant (CXCR4ΔNTR23; first 23 amino acids removed from NTR) were amplified to examine their coreceptor activities. NP-2/CD4/CXCR4 and NP-2/CD4/CXCR4ΔNTR23 cell lines were prepared accordingly. Indirect immune fluorescence assay (IFA), PCR, and reverse transcriptase (RT) activity were used to compare the process of infection of host cells by HIV-1IIIB virus, one R5-tropic and five other R5X4-tropic viruses. All the R5X4-tropic HIVs were found to utilize both CCR5 and CXCR4 but unable to use CXCR4ΔNTR23 as coreceptors. In contrast, X4-tropic HIV-1IIIB was found to preferentially infect through CXCR4ΔNTR23. Viral antigens in infected NP-2/CD4/CXCR4ΔNTR23 cells were detected by IFA and confirmed by detection of proviral DNA and by performing RT assays on the spent cell-supernatants. In dual tropic viruses, deletion of 23 amino acids from NTR abrogates the coreceptor activity of CXCR4. This observation demonstrates that NTR of CXCR4 have an obligatory coreceptor role for dual tropic viruses. However, HIV-1IIIB may have different requirements for NTR than R5X4 viruses or may infect host cells independent of NTR of CXCR4.
人类免疫缺陷病毒通过 CCR5 核心受体启动感染，然后改变其对 C-X-C 趋化因子受体 4（CXCR4）的嗜性，这种变化与快速疾病进展有关。HIV-1IIIB 是一种广泛描述的纯 X4 嗜性株，与 R5X4 嗜性病毒不同。在这项研究中，检查了 CXCR4 的氨基末端区域（NTR）对 HIV-1IIIB 病毒进入宿主细胞的需求，并将其与 R5X4 嗜性病毒进行了比较。扩增了 CXCR4 及其缺失突变体（CXCR4ΔNTR23；从 NTR 中去除前 23 个氨基酸），以检查其辅助受体活性。相应地制备了 NP-2/CD4/CXCR4 和 NP-2/CD4/CXCR4ΔNTR23 细胞系。间接免疫荧光测定（IFA）、PCR 和逆转录酶（RT）活性用于比较 HIV-1IIIB 病毒、一种 R5 嗜性病毒和其他五种 R5X4 嗜性病毒感染宿主细胞的过程。发现所有 R5X4 嗜性 HIV 均利用 CCR5 和 CXCR4，但不能利用 CXCR4ΔNTR23 作为辅助受体。相比之下，X4 嗜性 HIV-1IIIB 被发现优先通过 CXCR4ΔNTR23 感染。IFA 检测到感染 NP-2/CD4/CXCR4ΔNTR23 细胞中的病毒抗原，并通过检测前病毒 DNA 和对用过的细胞-上清液进行 RT 检测来确认。在双重嗜性病毒中，从 NTR 缺失 23 个氨基酸会破坏 CXCR4 的辅助受体活性。这一观察结果表明，CXCR4 的 NTR 对于双重嗜性病毒具有必需的辅助受体作用。然而，HIV-1IIIB 可能对 NTR 有不同于 R5X4 病毒的要求，或者可能独立于 CXCR4 的 NTR 感染宿主细胞。
