Antiviral Drug Resistance in Human Cytomegalovirus

描述(申请人提供)：耐药性限制了在严重免疫抑制的宿主中对巨细胞病毒(CMV)疾病的长期抗病毒治疗的有效性。尽管联合抗逆转录病毒疗法的出现减少了侵袭性CMV疾病的发生率，但对于那些抗HIV治疗失败的人和发生原发CMV感染的移植受者来说，这仍然是一个问题。在过去的几年里，我们对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理解，这些突变导致了对当前系统抗CMV药物更昔洛韦、磷甲酸钠和西多福韦的耐药性。这一信息已被广泛用于CMV抗性的基因诊断。我们的知识中仍然存在一些差距。可能在UL97和UL54或其他与DNA复制有关的病毒基因中存在额外的突变，这些突变导致不同程度的耐药性或生长适应。多个突变的联合效应还没有得到很好的描述。当在不同的病毒遗传背景下进行评估时，特定的耐药性突变似乎会对相同的药物产生不同程度的耐药性。CMV生长和耐药性的表型分析需要改进。抗巨细胞病毒新药苯并咪唑L核苷类药物马利巴韦具有药效好、口服生物利用度高、早期临床试验毒性低、直接抑制UL97等不同的抗病毒作用机制等优点。已发现对maribavir耐药的CMV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株来研究影响对当前抗CMV药物的耐药性和交叉耐药性的其他病毒突变，(2)调查不同病毒遗传背景下单个和多个突变的表型效应，以及(3)确定CMV对maribavir的耐药性的遗传基础。实验重点包括开发高效、诊断有用的方法来构建包含特定突变的重组病毒并对其进行表型鉴定，以及确定CMV基因UL27目前未知的功能，该基因最近被发现在几种对maribavir耐药的病毒中发生突变。

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.