A neonatal mouse model to study retrovirus-specific humoral responses

项目摘要 只有极少数人对逆转录病毒感染具有天然抵抗力。虽然全基因组关联 研究可以确定与抗性相关的遗传位点，在基因中找到特定的抗性基因， 丰富的基因座已经被证明是一个巨大的挑战。另一方面，近交系小鼠提供了一个很好的选择， 绘制负责逆转录病毒抗性和易感性的哺乳动物基因。我们已经描述了 隐性基因座命名为“病毒感染性控制器1”（vic 1），其负责产生逆转录病毒， 来自I/LnJ株的小鼠中的中和抗体（Ab）（2）。vic 1介导中和抗体应答， 两种不同的鼠逆转录病毒（6，2，8）。因此，vic 1代表了一种广泛耐药的机制， 逆转录病毒利用定位克隆和计算方法，我们确定了H2-Ob（Ob）作为基因 编码Vic 1（1）。Ob编码β亚基，β亚基与Oa编码的α亚基一起形成 进化上保守的非经典主要组织相容性复合物II类分子H2-O（HLA-1）， DO），抗原呈递的负调节因子。H2-O/HLA-DO的精确功能仍然是 这是一个有争议的问题，但它似乎与其通过抑制另一种MHC-II肽库来修饰MHC-II肽库的能力有关。 MHC-II样分子，H-2 M（人类HLA-DM）（9）。 通过将Ob的I/LnJ等位基因移动到 几种病毒易感背景，如C3 H/HeN，B6和BALB/cJ，并通过产生敲除 在B6小鼠中的基因的等位基因。所有这些动物产生逆转录病毒中和抗体。然而，效果只 如果这些动物在成年时被感染，相反，I/LnJ小鼠产生逆转录病毒- 中和抗体，而不论其感染时的年龄，甚至当他们作为新生儿感染时。这一发现 提示我们寻找I/LnJ新生儿耐药的遗传基础。这个特征成功地与 15号染色体上的一个4.1 Mb的单一显性区域，即病毒感染性控制因子2（vic 2）。Vic 2函数为 只有在没有功能性Ob的情况下才明显。非功能性Ob和vic 2 i的遗传赋予了 从所有敏感品系产生抗新生小鼠病毒抗体的能力。 许多病毒，包括逆转录病毒，感染成人，但也通过母亲给新生儿 在分娩和哺乳期间。普遍认为新生儿的免疫系统是 这导致了疫苗接种不发达，增加了感染风险，并削弱了对许多疫苗的反应。然而，I/LnJ 小鼠产生病毒中和免疫应答，与它们暴露于病毒的年龄无关。 病原体因此，解开Vic 2功能的机制对于 了解新生儿免疫系统的未知特征，并获得刺激新生儿免疫系统的能力。 在新生儿中产生病原体特异性免疫。vic 2的鉴定和途径的描绘 是本提案的目标。

Project Summary Only rare humans are naturally resistant to retroviral infections. Although genome wide association studies can identify genetic loci associated with the resistance, finding particular resistance genes within gene- rich loci has proven to be a great challenge. On the other hand, inbred mice offer a great alternative for mapping mammalian genes responsible for resistance and susceptibility to retroviruses. We have described a recessive locus named ‘virus infectivity controller 1’ (vic1), which is responsible for production of retrovirus- neutralizing antibodies (Ab) in mice from the I/LnJ strain (2). vic1 mediates a neutralizing Ab response against two different murine retroviruses (6, 2, 8). Thus, vic1 represents a mechanism of broad resistance against retroviruses. Using positional cloning and computational approaches we identified H2-Ob (Ob) as the gene coding for Vic1 (1). Ob encodes the beta subunit which together with alpha subunit, encoded by Oa, forms evolutionally conserved the non-classical Major Histocompatibility Complex class II-like molecule H2-O (HLA- DO in humans), a negative regulator of antigen presentation. The precise function of H2-O/HLA-DO is still debated, but it appears to be related to its ability to modify the MHC-II peptide repertoire by inhibiting another MHC-II-like molecule, H-2M (HLA-DM in humans) (9). The role of non-functional Ob in retroviral resistance was confirmed by moving the I/LnJ allele of Ob to several virus-susceptible backgrounds, such as C3H/HeN, B6, and BALB/cJ, and by producing a knock-out allele of the gene in B6 mice. All these animals produced retrovirus-neutralizing Abs. However, the effect only had high penetrance if these animals were infected as adults. In contrast, I/LnJ mice produced retrovirus- neutralizing Abs irrespective of their age at infection, even when they were infected as newborns. The finding prompted us to search for the genetic basis of resistance of I/LnJ neonates. The trait was successfully linked to a single dominant 4.1 Mb region of Chromosome 15, virus infectivity controller 2 (vic2). Vic2 function was only apparent in the absence of functional Ob. The inheritance of both non-functional Ob and vic2i conferred the ability to produce anti-virus Abs to neonatal mice from all susceptible strains. Many viruses, including retroviruses, infect adults, but are also passed from mothers to newborns during birth and breastfeeding. It is commonly accepted that the immune system of a newborn is underdeveloped, increasing the risk of infection and impairing responses to many vaccines. However, I/LnJ mice generate a virus-neutralizing immune response independent of the age at which they were exposed to the pathogen. Thus, it is fundamentally important to unravel the mechanism of Vic2’s function in order to understand the unknown features of the neonate immune system and to acquire the ability of stimulating productive pathogen-specific immunity in neonates. Identification of vic2 and the delineation of the pathway that it controls are the goals of this proposal.