Antiviral Drug Resistance in Human Cytomegalovirus

描述（由申请人提供）：在严重免疫抑制的宿主中，耐药性限制了巨细胞病毒（CMV）疾病长期抗病毒治疗的疗效。尽管联合抗逆转录病毒疗法的出现降低了侵袭性巨细胞病毒疾病的频率，但它仍然是抗hiv治疗失败和发生原发性巨细胞病毒感染的移植受者的一个问题。在过去的几年中，我们已经对CMV UL97磷酸转移酶和UL54 DNA聚合酶基因的常见突变有了合理的了解，这些突变赋予了当前系统性抗CMV药物更昔洛韦、氟膦酸钠和西多福韦的耐药性。这一信息已被广泛用于巨细胞病毒耐药性的基因型诊断。我们的知识还存在一些空白。UL97和UL54或其他参与DNA复制的病毒基因可能存在额外的突变，这些突变赋予了不同程度的耐药性或生长适应性。多种突变的综合效应尚未得到很好的描述。在评估不同病毒遗传背景时，特异性耐药突变似乎赋予了对相同药物不同程度的耐药。CMV生长和耐药的表型分析有待改进。一种新的抗巨细胞病毒苯并咪唑l -核苷药物马里巴韦在早期临床试验中似乎具有效力、口服生物利用度、低毒性以及直接抑制UL97的不同抗病毒作用机制等优点。已发现耐马里巴韦的巨细胞病毒毒株UL97或UL27基因发生突变。现有的信息暗示了病毒复制的病毒粒子组装阶段的复杂性，以及它作为抗病毒靶点的潜力。未来一段时间的具体目标仍然是：(1)通过将突变转移到参考CMV毒株，研究影响当前抗CMV药物耐药和交叉耐药的其他病毒突变；(2)研究不同病毒遗传背景下单个和多个突变的表型效应；(3)确定CMV对马里巴韦耐药的遗传基础。实验重点包括开发高效、诊断有用的方法来构建和分型含有特定突变的重组病毒，并确定目前未知的CMV基因UL27的功能，该基因最近被发现在几种马里巴韦耐药病毒中发生突变。

DESCRIPTION (provided by applicant): Drug resistance limits the efficacy of long-term antiviral therapy for cytomegalovirus (CMV) disease in severely immunosuppressed hosts. Although the advent of combination antiretroviral therapy has reduced the frequency of invasive CMV disease, it continues as a problem in those failing anti-HIV therapy and in transplant recipients who develop primary CMV infection. In the past few years we have developed a reasonable understanding of the common mutations in the CMV UL97 phosphotransferase and UL54 DNA polymerase genes that confer resistance to the current systemic anti-CMV drugs ganciclovir, foscarnet and cidofovir. This information is already widely used for genotypic diagnosis of CMV resistance. Some gaps in our knowledge remain. There are probably additional mutations in UL97 and UL54, or in other viral genes involved in DNA replication, that confer varying degrees of drug resistance or growth adaptation. The combined effects of multiple mutations have not been well characterized. Specific resistance mutations seem to confer varying degrees of resistance to the same drugs when assessed in different viral genetic backgrounds. Phenotypic assays for CMV growth and drug resistance need to be improved. A newer anti- CMV benzimidazole L-riboside drug, maribavir, appears to have the advantages of potency, oral bioavailablility, low toxicity in early clinical trials, and different mechanisms of antiviral action involving the direct inhibition of UL97. Maribavir-resistant CMV strains have been found with mutations in their UL97 or UL27 genes. The available information hints at the complexity of the virion assembly stage of viral replication, and its potential as an antiviral target. The specific aims for the upcoming period remain (1) to study additional viral mutations that affect resistance and cross-resistance to current anti-CMV drugs, by transfer of the mutations to reference CMV strains, (2) investigate the phenotypic effects of single and multiple mutations on different viral genetic backgrounds, and (3) determine the genetic basis of CMV resistance to maribavir. Experimental priorities include the development of efficient, diagnostically useful approaches for constructing and phenotyping recombinant viruses containing specific mutations, and defining the presently unknown function of the CMV gene UL27 which was recently found to be mutated in several maribavir-resistant viruses.