Th17细胞在小鼠巨细胞病毒感染急性期的作用研究

目的 整体水平观察Th17细胞在小鼠巨细胞病毒(MCMV)播散性感染急性期的作用.方法 建立MCMV播散性感染模型,病毒接种后第3、7、14和28天各处死3只小鼠;同时设模拟感染鼠作为对照.应用real-time PCR法检测MCMV感染鼠脏器MCMV DNA载量;HE染色观察MCMV感染后脾组织病理损伤变化;流式细胞术检测脾细胞中CD4+IL-17A+T细胞比率;ELISA法检测脾细胞培养上清中IL-17A蛋白浓度.结果 感染急性期唾液腺组织中MCMV DNA于感染后14 d最高;脾组织病理损伤也于感染后14 d最严重;与模拟感染对照鼠相比,MCMV感染鼠脾细胞中CD4+IL-17A+T细胞比率呈升高趋势(均P＜0.01),且于感染后14 d达峰值[(1.14±0.09)％ vs (0.19±0.04)％,t=17.551,P=0.000];病毒特异性IL-17A浓度也于感染后14 d达峰值[(81.98±12.37) pg/ml vs (44.96±8.44) pg/ml,t=4.281,P=0.006];脾细胞培养上清中病毒特异性IL-17A水平与唾液腺组织中MCMV DNA载量呈正相关(r=0.54,P＜0.05);脾组织病理损伤越重,脾细胞培养上清中IL-17A浓度越高.结论 Th17细胞主要通过IL-17A参与MCMV播散性感染急性期免疫应答,直接或间接的促进病毒复制或脾组织局部病理损伤,可能是MCMV持续性感染的重要原因之一.     

AIM2炎性体识别胞浆鼠巨细胞病毒DNA的实验研究

目的 观察AIM2( absent in melanoma 2)在感染早期识别胞浆小鼠巨细胞病毒(MCMV) DNA的变化状况.方法 建立MCMV全身播散型感染模型,接种MCMV Smith株后第1、3、5和7天各处死3只小鼠;同时设模拟感染小鼠作为正常对照.Western blot检测脾脏巨噬细胞中AIM2、衔接子凋亡相关点样蛋白(ASC)和caspase-1蛋白的表达状况;同时应用ELISA法检测血清中IL-1β和IL-18的水平;空斑法测定感染小鼠唾液腺感染性病毒滴度.结果 MCMV感染后第3、5、7天,小鼠唾液腺组织中感染性病毒滴度逐渐增加;MCMV感染鼠脾脏巨噬细胞中AIM2、ASC和caspase-1蛋白的表达呈现一致的变化,与模拟感染对照鼠比较,AIM2、ASC和caspase-1蛋白相对吸光值在感染后第1天开始升高(P＞0.05),第3天明显升高并达峰值[分别为(1.121±0.243) vs(0.240±0.046),(1.318±0.333) vs (0.248±0.090),(1.085±0.243) vs (0.247±0.064); P＜0.01],其后接近正常;MCMV感染鼠血清IL-1β和IL-18水平在感染后第3天也明显高于模拟感染对照鼠[分别为(112.72±5.20) pg/ml vs (47.86±4.35) pg/ml,(42.74±4.23) pg/ml vs( 22.60±2.82)pg/ml;P＜0.01],其后均逐渐下降接近正常.结论 MCMC感染早期巨噬细胞通过AIM2炎性体识别胞浆MCMV DNA,可能成为CMV感染及感染后所引起的疾病的治疗靶点.     

急性MCMV感染对小鼠脾Th1/Th2/Th17细胞亚群分化的影响

目的:在整体水平观察小鼠巨细胞病毒(MCMV)感染对小鼠脾Th1/Th2/Th17细胞亚群分化及其主要的效应性细胞因子(IFN-γ、IL-4、IL-17A)表达的影响.方法:建立MCMV感染模型,8只BALB/c小鼠分别于接种MCMV Smith株后3天和14天各处死4只;另设8只接种唾液腺匀浆的模拟感染小鼠作为对照.用空斑形成试验测定肝、脾和唾液腺组织病毒滴度;流式细胞术检测脾T淋巴细胞中Th1(CD4+ IFN-γ+)、Th2(CD4+ IL-4+)、Th17(CD4+IL-17A+)细胞比例,双抗体夹心ELISA法检测脾细胞培养上清中病毒特异性IFN-γ、IL-4、IL-17A水平.结果:MCMV感染早期肝、脾和唾液腺组织中病毒呈低水平复制,而感染后14天仅在唾液腺组织呈高水平复制;Th1细胞比例及病毒特异性IFN-γ主要在MCMV感染早期呈显著升高(P ＜0.01);Th2细胞及IL-4均无明显表达及改变;Th17细胞及病毒特异性IL-17A则主要在感染后14天升高(P＜0.05).结论:MCMV感染早期,机体通过上调Th1细胞分化比例及IFN-γ的表达发挥抗病毒效应,而MCMV诱导Th17细胞分化及IL-17A的高表达可能是MCMV感染致宿主特异性细胞免疫功能失调并逃避机体特异性细胞免疫攻击的原因之一.     

小鼠巨细胞病毒开放阅读框M43突变株体内效应研究

小鼠巨细胞病毒RvM4 3突变株的M4 3开放阅读框中插入Tn -gpt序列。突变株和野生型RqM4 3分别通过唾液腺注射感染免疫缺陷型小鼠CM17SCID ,在感染后不同的时间内分别取出小鼠的唾液腺 ,脾 ,肝 ,肺和肾脏 ,测定M4 3突变株的滴度。实验显示RvM4 3在唾液腺 ,脾 ,和肝中的滴度与野生型无显著性差异 ,但在感染 2 1天后 ,肾脏和肺中的病毒滴度有显著性差异。突变型和野生型感染后影响的死亡时间也存在着显著性差异。结果证实M4 3突变不影响体外细胞的复制 ,但对体内不同器官病毒的生长有不同的影响 ,同时有较弱的降低毒性的作用。研究为探索巨细胞病毒的致病机制提供了新的资料。     

经胎盘接种小鼠巨细胞病毒宫内感染模型建立

目的应用小鼠巨细胞病毒宫内感染模型,观察母鼠妊娠结局。方法用ELISA筛选无MCMV感染史性成熟期小鼠,雌雄同笼受孕。孕龄12.5天时,模型组胎盘显微注射MCMV,对照组注射生理盐水,空白对照组不做任何处理。部分在孕龄18.5天处死母鼠,部分待母鼠自然分娩,观察母鼠妊娠结局及子代感染情况。结果模型组36.62%(26/71)和生理盐水对照组29.85%(20/67)的死胎率,χ2=0.711,P>0.05。分别和空白对照组0.00%(0/68),P<0.01。比较三组组畸胎率分别为22.54%(16/71)、0.00%(0/67)和0.00%(0/68),P<0.01。空白对照组和生理盐水对照组未发现胎盘和胎仔感染,模型组胎盘感染率63.27%(31/49)、胎仔感染率为32.65%(16/49),χ2=0.136,P<0.01。结论小鼠巨细胞病毒宫内模型的建立为其发病机理研究、选择宫内感染的干预介入点提供了新的靶点。     

Identification of mutations in a temperature‐sensitive mutant (tsm5) of murine cytomegalovirus using complementary genome sequencing

Identification of mutations in mutants derived chemically is a difficult and relatively random process. NimbleGen Comparative Genome Sequencing (CGS) was assessed as an inexpensive, rapid method of identifying mutations in the temperature‐sensitive mutant tsm5 of the K181 (Birmingham) variant of murine cytomegalovirus (MCMV). This genome resequencing approach requires an established genome sequence as a reference. Comparison of tsm5 and the K181 (Birmingham) variant with the published K181 (Perth) MCMV genomic sequence revealed a total of 10 synonymous and 15 non‐synonymous SNPs in tsm5 and 14 of the latter were confirmed by sequencing. Thus, while CGS cannot be relied upon to identify correctly all mutations it was helpful for identifying a large number of mutations for further investigation that could contribute to the ts phenotype of tsm5. J. Med. Virol. 81:511–518, 2009. © 2009 Wiley‐Liss, Inc.     

小鼠巨细胞病毒对小鼠未成熟卵母细胞体外成熟的影响

目的探讨小鼠巨细胞病毒对小鼠卵母细胞体外成熟的影响.方法将未成熟小鼠卵母细胞置于含100 TCID50、10TCID50、1TCID50小鼠巨细胞病毒的培养液中培养,观察卵母细胞的生发泡破裂率和第一极体的释放率,并应用电镜观察卵母细胞超微结构.结果各组的卵母细胞生发泡破裂率和第一极体的释放率差异无显著性,100 TCID50组未出现卵母细胞超微结构异常.结论小鼠巨细胞病毒对未成熟卵母细胞体外成熟发育无重大影响.     

Patterns of divergence in the vCXCL and vGPCR gene clusters in primate cytomegalovirus genomes

Primate cytomegalovirus (CMV) genomes contain tandemly repeated gene clusters putatively encoding divergent CXC chemokine ligand-like proteins (vCXCLs) and G protein-coupled receptor-like proteins (vGPCRs). In human, chimpanzee and rhesus CMVs, respectively, the vCXCL cluster contains two, three and six genes, and the vGPCR cluster contains two, two and five genes. We report that (i) green monkey CMV strains fall into two groups, containing either eight and five genes or seven and six genes in the respective clusters, and (ii) owl monkey CMV has two and zero genes. Phylogenetic analysis suggested that the vCXCL cluster evolved from a CXCL chemokine gene (probably GRO-α) that was captured in an incompletely spliced form by an ancestor of Old and New World primate CMVs, and that the vGPCR cluster evolved from a GPCR gene captured by an Old World primate CMV. Both clusters appear to have evolved via complex duplication and deletion events.     

Characterization of the murine cytomegalovirus m136 gene

The 230-kbp murine cytomegalovirus (MCMV) genome is predicted to encode 182 open reading frames (orfs). One gene whose functional role is not known is encoded by the 762-bp m136 orf. Sequence analysis of rat cytomegalovirus (RCMV) strains Maastricht and English revealed homologous orfs, pr136, and ORF HJ4, respectively. Conservation of these orfs suggested that m136 and the RCMV homologs might play a role during virus replication. Expression of an epitope tagged form of m136 (m136-V5) yielded a polypeptide of 34 kDa that localized to the perinuclear region of transfected mouse 3T3 fibroblasts. Three independently generated MCMV m136 mutants were isolated and characterized. Mutations were introduced into the m136 orf by inserting either a β-glucuronidase (m136-β-gluc) or a guanosine phosphoribosyl transferase (m136-gpt) expression cassette into a unique BglII site, or by inserting a gpt cassette into a deleted region (Δm136) of m136. No differences were observed in viral yield, plaque size, and plaque morphology between the parental strain and any of the m136 mutant viruses. In vivo analysis using a SCID mouse virulence model showed a consistently measurable attenuated phenotype for all three m136 mutants. The results showed that although the m136 gene was not essential for replication in vitro or in vivo, an intact m136 gene was necessary to yield wild type virulence during infection of the host.     

Murine cytomegalovirus regulation of NKG2D ligands

Human cytomegalovirus (HCMV) is a ubiquitous pathogen that causes morbidity risk in immunologically suppressed and immunodeficient patients including congenital infections. Approaches to curb the consequences of HCMV infections are restricted by a lack of complete understanding of viral pathogenesis. The infection of mice with murine cytomegalovirus (MCMV) as a model of HCMV infection has been particularly useful in elucidating the role of innate and adaptive immune response mechanisms. A large number of cytomegalovirus genes modulate the innate and the adaptive host immune response. The products of several MCMV genes are involved in subverting the natural killer (NK) cell response by down-modulating cellular ligands for the NKG2D receptor expressed on NK cells and CD8⁺ T cells. Mutant viruses lacking these immunoevasion genes are attenuated with respect to virus growth in vivo. Given the importance of the NKG2D receptor in controlling both NK- and T cell-mediated immunity, it is of tremendous importance to understand the molecular mechanisms and consequences of viral regulation of the NKG2D ligands.     

Genes of murine cytomegalovirus exist as a number of distinct genotypes

Murine cytomegaloviruses encode a number of genes which modulate polymorphic host immune responses. We suggest that these viral genes should themselves therefore exhibit sequence polymorphism. Additionally, clinical isolates of human cytomegalovirus (HCMV) have been shown to vary extensively from the common laboratory strains. Almost all research conducted on murine cytomegalovirus (MCMV) has used the laboratory strains Smith and K181, which have been extensively passaged in vitro and in vivo since isolation. Using the heteroduplex mobility assay (HMA) to determine levels of sequence variation 11 MCMV genes were examined from 26 isolates of MCMV from wild mice, as well as both laboratory strains. Both the HMA and sequencing of selected genes demonstrated that whilst certain genes (M33, mck-2, m147.5, m152) were highly conserved, others (m04, m06, M44, m138, m144, m145 and m155) contained significant sequence variation. Several of these genes (m06, m144 and m155) exist in wild MCMV strains as one of several distinct genotypes.     

A rapid and easy method for production and selection of recombinant adenovirus genomes

Adenoviruses are used widely as vectors for gene therapy. Due to the large size of their genome there is a low frequency of unique restriction sites and many techniques have been described to construct recombinant viruses. Whatever the considered technique, the Escherichia coli strain BJ5183 is used to obtain recombinant adenovirus genomes in a plasmid, or to construct defective viral backbones which will be used to produce infectious viral particles by homologous recombination in HEK293 cells. Unfortunately BJ5183 bacteria do not produce a sufficient amount of plasmid DNA to allow for restriction analysis. Plasmids have to be transferred into another strain to detect the expected construction. It is reported now that the common E. coli strain, Top10F′ can be used for the construction of recombinant adenovirus genomes. A plasmid carrying a kanamycin resistance gene and containing the two ends of the adenovirus genome was used. It permits modification by classical molecular biology techniques or homologous recombination at both ends of the genome. The remainder of the genome is introduced by homologous recombination in Top10F′. Several homologous recombination steps were successfully performed without the steps of extraction and introduction of plasmid DNA in another strain to check the plasmids obtained.     

Listeria monocytogenes as novel carrier system for the development of live vaccines

Listeria monocytogenes is a facultative intracellular bacterium that enters a variety of non-professional mammalian cells by triggered phagocytosis (“zipper mechanism”) and replicates in the cytosol of the infected host cells. Therefore, it is a promising vaccine vector for the presentation of passenger antigens to the MHC class II and especially class I pathways. Here, we review recent progress made in our laboratory on the development of novel attenuated L. monocytogenes carrier strains for the delivery of heterologous antigens or antigen-encoding DNA and RNA to eukaryotic host cells. Based on the deletion of the chromosomal copy of the tryptophanyl-tRNA synthetase gene (trpS) and plasmid-based in trans complementation of the same, we were able to establish a balanced-lethal plasmid system in L. monocytogenes. Safety concerns in the antigen delivery in vivo were addressed by chromosomal deletion of genes in the basic branch of the aromatic amino acid pathway, resulting in safe, attenuated L. monocytogenes carrier strains. Furthermore, plasmid-based expression of a cytosolically expressed phage lysin resulted in a self-destructing carrier strain that has been successfully used for the delivery of antigens as well as antigen-encoding plasmid DNA and particularly mRNA, therefore overcoming bottlenecks that have been shown to exist for bacteria-mediated DNA delivery.     

The IFN regulatory factor 7‐dependent type I IFN response is not essential for early resistance against murine cytomegalovirus infection

IFN regulatory factor 7 (IRF7) has been described as the master regulator of type I IFN responses and has been shown to be critical for innate antiviral immunity in vivo. In addition to type I IFN, NK cell responses are involved in the control of viral replication during acute viral infection. To investigate the role of IRF7 in the context of a viral infection that induces a strong NK cell response, the murine cytomegalovirus (MCMV) infection model was used. WT, IRF7‐deficient and IRF3/IRF7‐double deficient mice were infected with MCMV. The systemic IFN‐α response to MCMV was entirely dependent on IRF7, but independent of IRF3. However, peak IFN‐β production during MCMV infection was not affected by the lack of IRF7 or both IRF7 and IRF3. Despite the complete lack of IFN‐α production IRF7‐ and IRF3/IRF7‐deficient mice were surprisingly efficient in controlling MCMV replication and were only modestly more susceptible to MCMV infection than WT mice. NK cell cytotoxicity was unimpaired and NK cell IFN‐γ production was enhanced in IRF7‐deficient mice correlating with increased levels of bioactive IL‐12. Owing to these compensatory mechanisms IRF7‐dependent antiviral immune responses were not essential for resistance against acute MCMV infection in vivo.     

Studies of an outbreak of acute hepatitis A: II. Antibody changes to cytomegalovirus and herpesvirus

The acute and convalescent sera from 14 schoolchildren with acute hepatitis A were tested for antibody changes to 70 viral antigens. Marked decreases were noted in the levels of antibody to cytomegalovirus in 5 of the 14 children and in the levels of antibody to herpesvirus type 1 in 3. No such changes were noted in 9 sex- and age-matched healthy control children from the same classes.     

The salivary glands as a privileged site of cytomegalovirus immune evasion and persistence

The salivary glands (SG) provide a haven for persistent cytomegalovirus replication, and in this regard are a privileged site of virus immune evasion. The murine cytomegalovirus (MCMV) model has provided insight into the immunological environment of the SG and the unqiue virus–host relationship of this organ. In response to MCMV infection, a robust T cell-mediated immune response is elicited, comprised predominantly of CD8+ T cells that phenotypically and functionally appear activated. However, they fail to clear virus by an unknown evasion mechanism that is independent of inhibitory NKG2A- or Programmed Death 1-mediated signaling. Virus is eventually eliminated from the SG by effector CD4+ T cells expressing antiviral cytokines. However, this mechanism is severely dampened by high levels of the immunosuppressive cytokine IL-10, selectively expressed by SG CD4+ T cells.     

Developmental disorders of the mouse brain induced by murine cytomegalovirus: Animal models for congenital cytomegalovirus infection

Developmental disorders induced by congenital cytomegalovirus (CMV) infection mainly involve the central nervous system. The type and degree of the brain disorders seems to depend on infection time during gestation, virulence, route of infection and viral susceptible cells in each embryonal stage. Since transplacental transmission has been reported not to occur with murine CMV (MCMV), we developed mouse models for congenital CMV infection by surgical injection of MCMV into the mouse conceptus or embryo at different gestational stages. For the early stage, the mouse embryos were not infected with MCMV even after injecting the virus into the blastocysts, which were developed in the pseudo-pregnant mothers or cultured in vitro. Isolated whole mouse embryos of day 7.5 of gestation (E7.5), adsorbed with a high titer of MCMV and cultured for 3 days, were susceptible to MCMV infection. Therefore, the mouse embryo acquires the susceptibility around this period. Microphthalmia and cerebral atrophy were induced in mouse embryos after injection of MCMV into the conceptus on E8.5. Viral antigen-positive cells were widely distributed in the mesenchyme around the oral and nasal cavities and in the mesenchyme around the brain, especially the endothelial cells of vessels and the perivascular mesodermal cells, then infection extends to the eyes, brain or choroid plexus. This finding suggests that mesenchymal infection may be the critical step in disrupting organogenesis, resulting in brain disorders. For the late stage, mouse embryos were infected with MCMV by injecting the virus into the cerebral ventricles on E15.5. Brains of the offspring showed massive necrosis with gliomesodermal proliferation in the cerebral cortex. Viral antigen-positive cells were observed in laminar array in the lesion-free cortex and the hippocampus, suggesting that the infected cells migrate in association with the lamina formation. Imrnuno-histochemical double-staining showed that brain cells susceptible to MCMV infection may be mainly neuronal and endothelial cells, resulting in cerebral atrophy with reduction of neuronal cells and cystic lesions, presumably due to ischemic vascular changes.