A neonatal mouse model to study retrovirus-specific humoral responses

项目概要 只有极少数人对逆转录病毒感染具有天然抵抗力。尽管全基因组关联 研究可以识别与抗性相关的基因位点，在基因中找到特定的抗性基因 丰富的基因座已被证明是一个巨大的挑战。另一方面，近交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图谱。我们已经描述了一个 名为“病毒感染性控制器 1”（vic1）的隐性基因座，负责产生逆转录病毒 I/LnJ 品系小鼠体内的中和抗体 (Ab) (2)。 vic1 介导中和抗体反应 两种不同的鼠逆转录病毒（6、2、8）。因此，vic1 代表了一种广泛抵抗的机制。 逆转录病毒。使用定位克隆和计算方法，我们将 H2-Ob (Ob) 确定为基因 Vic1 (1) 的编码。 Ob 编码 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体 II 类分子 H2-O (HLA- DO（人类），抗原呈递的负调节因子。 H2-O/HLA-DO的精确功能仍然是 有争议，但它似乎与其通过抑制另一种肽来修饰 MHC-II 肽库的能力有关。 MHC-II 样分子，H-2M（人类 HLA-DM）(9)。 通过将 Ob 的 I/LnJ 等位基因移至 多种病毒敏感背景，例如 C3H/HeN、B6 和 BALB/cJ，并通过产生敲除 B6 小鼠中该基因的等位基因。所有这些动物都产生了逆转录病毒中和抗体。但效果仅 如果这些动物成年后被感染，则具有很高的外显率。相比之下，I/LnJ 小鼠产生逆转录病毒 中和抗体，无论感染时的年龄如何，即使他们在新生儿时被感染。研究结果 促使我们寻找I/LnJ新生儿耐药的遗传基础。该特征已成功链接 15 号染色体的单个显性 4.1 Mb 区域，即病毒感染性控制器 2 (vic2)。 Vic2 功能是 仅在功能性 Ob 缺失时才明显。非功能性 Ob 和 vic2i 的继承都赋予 能够从所有易感品系中向新生小鼠产生抗病毒抗体。 许多病毒，包括逆转录病毒，会感染成年人，但也会从母亲传染给新生儿 在出生和哺乳期间。人们普遍认为新生儿的免疫系统是 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反应，与接触病毒的年龄无关 病原体。因此，阐明 Vic2 的功能机制对于 了解新生儿免疫系统的未知特征并获得刺激的能力 新生儿产生有效的病原体特异性免疫力。 vic2 的鉴定和通路的描绘 它所控制的是本提案的目标。

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.