Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, United States of America.
PLoS One. 2011;6(7):e22020. doi: 10.1371/journal.pone.0022020. Epub 2011 Jul 8.
Viral resistance to small molecule allosteric inhibitors of CCR5 is well documented, and involves either selection of preexisting CXCR4-using HIV-1 variants or envelope sequence evolution to use inhibitor-bound CCR5 for entry. Resistance to macromolecular CCR5 inhibitors has been more difficult to demonstrate, although selection of CXCR4-using variants might be expected. We have compared the in vitro selection of HIV-1 CC1/85 variants resistant to either the small molecule inhibitor maraviroc (MVC) or the macromolecular inhibitor 5P12-RANTES. High level resistance to MVC was conferred by the same envelope mutations as previously reported after 16-18 weeks of selection by increasing levels of MVC. The MVC-resistant mutants were fully sensitive to inhibition by 5P12-RANTES. By contrast, only transient and low level resistance to 5P12-RANTES was achieved in three sequential selection experiments, and each resulted in a subsequent collapse of virus replication. A fourth round of selection by 5P12-RANTES led, after 36 weeks, to a "resistant" variant that had switched from CCR5 to CXCR4 as a coreceptor. Envelope sequences diverged by 3.8% during selection of the 5P12-RANTES resistant, CXCR4-using variants, with unique and critical substitutions in the V3 region. A subset of viruses recovered from control cultures after 44 weeks of passage in the absence of inhibitors also evolved to use CXCR4, although with fewer and different envelope mutations. Control cultures contained both viruses that evolved to use CXCR4 by deleting four amino acids in V3, and others that maintained entry via CCR5. These results suggest that coreceptor switching may be the only route to resistance for compounds like 5P12-RANTES. This pathway requires more mutations and encounters more fitness obstacles than development of resistance to MVC, confirming the clinical observations that resistance to small molecule CCR5 inhibitors very rarely involves coreceptor switching.
病毒对 CCR5 的小分子别构抑制剂的耐药性已有充分的记录，涉及到预先存在的使用 CXCR4 的 HIV-1 变体的选择，或者是包膜序列进化以利用结合抑制剂的 CCR5 进行进入。尽管预期会选择使用 CXCR4 的变体，但对大分子 CCR5 抑制剂的耐药性更难证明。我们比较了 HIV-1 CC1/85 变体对小分子抑制剂马拉维若（MVC）或大分子抑制剂 5P12-RANTES 的体外选择。通过逐渐增加 MVC 的水平，在 16-18 周的选择后，与先前报道的相同的包膜突变赋予了对 MVC 的高水平耐药性。MVC 耐药突变体对 5P12-RANTES 的抑制完全敏感。相比之下，在三个连续的选择实验中，仅实现了对 5P12-RANTES 的短暂和低水平耐药性，并且每个实验都导致病毒复制的随后崩溃。通过 5P12-RANTES 进行的第四次选择在 36 周后导致了一种“耐药”变体，该变体已从 CCR5 切换为 CXCR4 作为核心受体。在选择对 5P12-RANTES 耐药的、使用 CXCR4 的变体时，包膜序列发生了 3.8%的分歧，在 V3 区域有独特且关键的取代。在没有抑制剂的情况下传代 44 周后，从对照培养物中回收的一部分病毒也进化为使用 CXCR4，尽管包膜突变较少且不同。对照培养物中既有通过在 V3 中删除四个氨基酸而进化为使用 CXCR4 的病毒，也有通过 CCR5 维持进入的病毒。这些结果表明，对于像 5P12-RANTES 这样的化合物，核心受体切换可能是耐药的唯一途径。该途径需要更多的突变，并遇到更多的适应性障碍，而不是对 MVC 的耐药性发展，这证实了临床观察结果，即对小分子 CCR5 抑制剂的耐药性很少涉及核心受体切换。
