VACCINES FOR PREVENTION OF EXPERIMENTAL CONGENITAL CMV

人巨细胞病毒（Human cytomegalovirus，HCMV）是一种重要的病原体，可引起免疫功能低下者（包括新生儿）的严重发病。 特别是，先天性CMV感染的婴儿具有神经发育不良结局的高风险。 由于预先存在的母体免疫保护免受由HCMV引起的严重疾病，因此开发旨在预防与先天性感染相关的大量发病率的疫苗具有相当大的兴趣。然而，由于巨细胞病毒严格的种属特异性，CMV疫苗难以在临床前环境中进行评估。 由于豚鼠巨细胞病毒（GPCMV）穿过胎盘，引起子宫内感染，豚鼠提供了一个模型系统，在其中测试疫苗预防CMV疾病。 不幸的是，该系统迄今尚未被充分利用，主要是因为对GPCMV的分子生物学知之甚少。 然而，最近已经克隆、表征和表达了编码主要体液免疫靶糖蛋白B（gB）和细胞介导的免疫靶pp65（UL83）的GPCMV基因。 因此，亚单位疫苗研究现在在该模型中是可行的。 因此，这些研究提出了三个主要目标。首先，将在我们的先天性感染模型中评价重组形式的包膜糖蛋白gB的免疫原性和保护效力。 我们将检验的假设是，重组gB将提供针对先天性CMV的保护，但以一种依赖于免疫抑制剂的方式。 我们将直接评估是否一个更有效的免疫调节剂，单磷酰脂质A（MPL），提供了一个更好的佐剂效果比明矾为基础的佐剂单独。 这将是首次在GPCMV模型中评估与人类临床使用相关的佐剂。 在第二个具体目标，我们将测试的作用，细胞毒性T淋巴细胞（CTL）的目标，UL83，作为载体疫苗表达的牛痘。 我们假设针对该CTL靶点的疫苗接种将提供针对先天性CMV疾病的保护。 这将是第一次评估一种疫苗，该疫苗在先天性感染模型中仅产生细胞介导的反应。 最后，在第三个具体目标中，我们将进行第一项研究，以测试DNA疫苗对先天性CMV感染的保护效力。 我们假设靶向gB和UL83的DNA疫苗将在我们的模型中提供针对疾病的功效。 从这些研究中获得的信息将与正在进行的HCMV疫苗研究相关，并将有助于优先考虑在预防先天性巨细胞病毒感染的进一步临床试验中应采用哪些疫苗策略。

Human cytomegalovirus (HCMV) is an important pathogen which causes severe morbidity in immunocompromised individuals, including newborn infants. In particular, infants born with congenital CMV infection are at high risk for poor neurodevelopmental outcome. Since pre-existing maternal immunity protects against severe disease caused by HCMV, there is considerable interest in developing vaccines designed to prevent the substantial morbidity associated with congenital infection. Vaccines for CMV have been difficult to evaluate in the preclinical setting, however, because of the strict species specificity of cytomegaloviruses. Since the guinea pig cytomegalovirus (GPCMV) crosses the placenta, causing infection in utero, the guinea pig provides a model system in which to test vaccines for the prevention of CMV disease. Unfortunately, this system has not to date been exploited to its fullest potential, largely because so little is known about the molecular biology of GPCMV. However, recently the GPCMV genes encoding the major humoral immune target glycoprotein B (gB) and the cell-mediated immune target pp65 (UL83) have been cloned, characterized and expressed. Subunit vaccine studies are thus now feasible in this model. Therefore, these studies propose three major aims. First, the immunogenicity and protective efficacy of a recombinant form of envelope glycoprotein gB will be evaluated in our congenital infection model. The hypothesis we will test is that recombinant gB will provide protection against congenital CMV, but in an adjuvant-dependent fashion. We will directly evaluate whether a more potent immunomodulatory agent, monophosphoryl lipid A (MPL), provides a better adjuvant effect than alum-based adjuvants alone. These will be the first assessments of adjuvants relevant to human clinical use in the GPCMV model. In the second specific aim, we will test the role of a cytotoxic-T-lymphocyte (CTL) target, UL83, as a vectored vaccine expressed in vaccinia. We hypothesize that vaccination against this CTL target will provide protection against congenital CMV disease. This will be the first assessment of a vaccine which elicits only cell-mediated responses in a model of congenital infection. Finally, in the third specific aim we will conduct the first studies to test the protective efficacy of DNA vaccines for protection against congenital CMV infection. We hypothesize that DNA vaccines which target both gB and UL83 will provide efficacy against disease in our model. Information obtained from these studies will be relevant to ongoing studies of HCMV vaccines, and will help to prioritize which vaccine strategies should be pursued in further clinical trials for the prevention of congenital cytomegalovirus infection.