鼠疫疫苗研究的现状与展望

鼠疫（Plague）是由鼠疫耶尔森菌(Yersina pestis，Y. pestis)（简称鼠疫菌）引起的一种烈性传染病，属甲类传染病，具有高度传染性和致病性。在过去的鼠疫大流行中近2亿感染者死亡。疫苗接种是疾病预防控制的重要方法。现就鼠疫疫苗的研究进展作一综述，为新疫苗的研制提供参考。     

鼠疫的流行病学概述

鼠疫是由鼠疫耶尔森菌(Yersinia pestis)引起严重危害人类健康的烈性传染病。本文介绍了鼠疫病原体——鼠疫耶尔森菌的一般特性及生物学特性, 并对国内、外鼠疫疫情现状进行总结。目前鼠疫在全球范围内的流行已进入新的活跃期,世界卫生组织将鼠疫列为近20年来重新流行的急性传染病之一。当前,全球疫区主要分布在非洲、亚洲和南美洲。我国人间鼠疫自20世纪80年代开始处于明显回升势态,近10年流行逐渐下降,但防控形势依然艰巨。     

鼠疫耶尔森氏菌环二鸟苷酸代谢及生物被膜形成调控研究进展

鼠疫耶尔森氏菌(Yersinia pestis,以下简称"鼠疫菌")是烈性传染病鼠疫的病原菌,以鼠蚤作为传播媒介。鼠疫菌在其传播媒介鼠蚤的前胃中形成生物被膜从而促进其在宿主间传播。鼠疫菌生物被膜的形成受第二信使分子环二鸟苷酸(c-di-GMP)的正向调控。鼠疫菌中c-di-GMP由二鸟苷酸环化酶(DGC)HmsT和HmsD合成,由磷酸二酯酶(PDE)HmsP降解。文中主要介绍影响鼠疫菌环二鸟苷酸代谢及生物被膜形成的调控因子,并对其作用机制进行讨论和总结。     

鼠疫耶尔森菌的基因组学和后基因组学研究进展

鼠疫耶尔森菌能导致致病性极强的鼠疫,可作为生物武器使用。鼠疫耶尔森菌的基因组全长4.65Mb,GC含量为47.6%,含有3个重要质粒pFra/pMT1,pPst/pPCP1和pYV1/pCD1,其中质粒pFra/pMT1和pPst/pPCP1为鼠疫耶尔森菌独有。鼠疫耶尔森菌基因组富含大量的插入序列和假基因,存在频繁的基因内重组,以水平转移的方式获得外源基因。鼠疫耶尔森菌基因组结构和功能的研究为鼠疫的发生、流行、暴发、致病机制研究和筛选鼠疫耶尔森菌治疗药物、研制疫苗提供理论基础和科学依据。     

假结核耶尔森氏菌与宿主之间相互作用的分子机制研究进展

耶尔森氏菌属中有3个种对人和动物具有致病性,包括鼠疫杆菌(Yersinia pestis)、小肠结肠炎耶尔森氏菌(Yersinia enterocolitica)和假结核耶尔森氏菌(Yersinia pseudotuberculosis)。研究发现,假结核耶尔森氏菌能通过小鼠小肠派氏淋巴结的M细胞(Microfold cell)进行跨细胞转运。这种转运方式首先是细菌利用其表面蛋白侵袭素Invasin或黏附素Yad A蛋白识别并结合宿主细胞表面的整合素Integrin受体家族成员的β1链,然后细胞膜上的分泌通道打开,细菌利用Ⅲ型分泌系统把效应蛋白注入宿主细胞内,破坏宿主细胞免疫系统进行感染的过程。过去三十年内关于假结核耶尔森氏菌有大量的文献报道,本文综述该菌与宿主细胞之间相互作用分子机制的研究进展,并讨论目前关于假结核耶尔森氏菌的研究方向及热点。     

鼠疫耶尔森菌抗原检测试剂用国家参考品的研制

目的研制鼠疫耶尔森菌(Yersinia pestis)抗原检测试剂用国家参考品。方法通过对5株鼠疫耶尔森菌和10株非鼠疫耶尔森菌的菌种检定、培养及灭活、抗原检测,组建鼠疫耶尔森菌抗原检测试剂用国家参考品。对参考品进行样品均匀性以及稳定性评估,组织5家实验室协作标定。结果参考品由5份阳性、10份阴性、1份最低检出量以及1份重复性样品组成,均匀性和稳定性良好。协作标定结果显示:①5份阳性参考品阳性率100%;②10份阴性参考品阴性率100%;③最低检出量参考品的检出量不高于1.0×10~6个菌/mL;④重复性参考品检测反应结果应一致(酶联免疫法、上转发光免疫层析法等CV<5%)。结论建立的鼠疫耶尔森菌抗原检测试剂用国家参考品填补了相关领域的空白,可用于相关试剂的质量控制。     

鼠疫耶尔森氏菌基因表达的环境调节

鼠疫耶尔森氏菌是烈性传染病鼠疫的病原菌,该菌在媒介(跳蚤)和宿主(哺乳动物)之间的循环过程中,基因表达适应环境谱的变化。本介绍鼠疫耶尔森氏菌适应环境信号如不同温度、离子浓度、pH等条件下的基因表达调控研究现状。     

鼠疫耶尔森氏菌LcrV基因的克隆及序列分析

为了研究鼠疫耶尔森氏菌（Y.pestis）保护性抗原V蛋白,从基因库中查得Y.pestis LcrV基因DNA序列,针对序列设计合成了一对PCR扩增引物,以本所保存的Y.pestis菌种为模板进行基因扩增,结果获得长约980bp的DNA片段。将扩增产物回收纯化,克隆至pGEM-T载体,构建重组载体pGEN-T/ypV,经过PCR,酶切鉴定,并对pGEM-T/ypV中的V基因片段进行测序,分析测序结果与己知序列相同,表明获得了LcrV基因。     

环介导等温扩增技术检测鼠疫耶尔森菌的敏感性和特异性研究

为观察环介导等温扩增(loop-mediated isothermal amplification,LAMP)技术能否适用于我国不同疫源地鼠疫耶尔森菌所有基因组型的检测,本研究建立了一种基于3a靶序列设计特异性引物快速检测鼠疫耶尔森菌的LAMP方法.选择分离自我国11个鼠疫自然疫源地的65株野生代表性鼠疫耶尔森菌株,同...     

鼠疫减毒活疫苗研究现状与展望

鼠疫(plague)是由鼠疫耶尔森氏菌(Yersinia pesits)引起的烈性传染病,在人类历史上曾造成约2亿人的死亡,在我国被列为甲类传染病。由于鼠疫菌具有高度致病性、传染性,被列为最具潜力的生物战剂和生物恐怖剂。在面临鼠疫威胁时,疫苗是最为有力的武器。鼠疫疫苗研究中,减毒活疫苗是重要的研究方向,现就鼠疫减毒活疫苗的研究现状进行综述,为新疫苗的研制提供参考。     

Role of the Yersinia pestis yersiniabactin iron acquisition system in the incidence of flea-borne plague

Plague is a flea-borne zoonosis caused by the bacterium Yersinia pestis. Y. pestis mutants lacking the yersiniabactin (Ybt) siderophore-based iron transport system are avirulent when inoculated intradermally but fully virulent when inoculated intravenously in mice. Presumably, Ybt is required to provide sufficient iron at the peripheral injection site, suggesting that Ybt would be an essential virulence factor for flea-borne plague. Here, using a flea-to-mouse transmission model, we show that a Y. pestis strain lacking the Ybt system causes fatal plague at low incidence when transmitted by fleas. Bacteriology and histology analyses revealed that a Ybt-negative strain caused only primary septicemic plague and atypical bubonic plague instead of the typical bubonic form of disease. The results provide new evidence that primary septicemic plague is a distinct clinical entity and suggest that unusual forms of plague may be caused by atypical Y. pestis strains.     

No evidence of persistent Yersina pestis infection at prairie dog colonies in north-central Montana

Sylvatic plague is a flea-borne zoonotic disease caused by the bacterium Yersinia pestis, which can cause extensive mortality among prairie dogs (Cynomys) in western North America. It is unclear whether the plague organism persists locally among resistant host species or elsewhere following epizootics. From June to August 2002 and 2003 we collected blood and flea samples from small mammals at prairie dog colonies with a history of plague, at prairie dog colonies with no history of plague, and from off-colony sites where plague history was unknown. Blood was screened for antibody to Y. pestis by means of enzyme-linked immunosorbent assay or passive hemagglutination assay and fleas were screened for Y. pestis DNA by polymerase chain reaction. All material was negative for Y. pestis including 156 blood samples and 553 fleas from colonies with a known history of plague. This and other studies provide evidence that Y. pestis may not persist at prairie dog colonies following an epizootic.     

Comparative and evolutionary genomics of Yersinia pestis

Yersinia pestis is the causative agent of plague, causing three human plague pandemics in history. Comparative and evolutionary genomics of Y. pestis are extensively discussed in this review. Understanding the genomic variability and the adaptive evolution of Y. pestis from the genomic point of view will contribute greatly to plague detection, identification, control and prevention.     

Yersinia pestis YopE contains a dominant CD8 T cell epitope that confers protection in a mouse model of pneumonic plague

Septic bacterial pneumonias are a major cause of death worldwide. Several of the highest priority bioterror concerns, including anthrax, tularemia, and plague, are caused by bacteria that acutely infect the lung. Bacterial resistance to multiple antibiotics is increasingly common. Although vaccines may be our best defense against antibiotic-resistant bacteria, there has been little progress in the development of safe and effective vaccines for pulmonary bacterial pathogens. The Gram-negative bacterium Yersinia pestis causes pneumonic plague, an acutely lethal septic pneumonia. Historic pandemics of plague caused millions of deaths, and the plague bacilli's potential for weaponization sustains an ongoing quest for effective countermeasures. Subunit vaccines have failed, to date, to fully protect nonhuman primates. In mice, they induce the production of Abs that act in concert with type 1 cytokines to deliver high-level protection; however, the Y. pestis Ags recognized by cytokine-producing T cells have yet to be defined. In this study, we report that Y. pestis YopE is a dominant Ag recognized by CD8 T cells in C57BL/6 mice. After vaccinating with live attenuated Y. pestis and challenging intranasally with virulent plague, nearly 20% of pulmonary CD8 T cells recognize this single, highly conserved Ag. Moreover, immunizing mice with a single peptide, YopE(69-77), suffices to confer significant protection from lethal pulmonary challenge. These findings suggest YopE could be a valuable addition to subunit plague vaccines and provide a new animal model in which sensitive, pathogen-specific assays can be used to study CD8 T cell-mediated defense against acutely lethal bacterial infections of the lung.     

Uniquely insidious: Yersinia pestis biofilms

Bubonic plague, one of history's deadliest infections, is transmitted by fleas infected with Yersinia pestis. The bacteria can starve fleas by blocking their digestive tracts, which stimulates the insects to bite repeatedly and thereby infect new hosts. Direct examination of infected fleas, aided by in vitro studies and experiments with the nematode Caenorhabditis elegans, have established that Y. pestis forms a biofilm in the insect. The extracellular matrix of the biofilm seems to contain a homopolymer of N-acetyl-d-glucosamine, which is a constituent of many bacterial biofilms. A regulatory mechanism involved in Y. pestis biofilm formation, cyclic-di-GMP signaling, is also widespread in bacteria; yet only Y. pestis forms biofilms in fleas. Here, the historical background of bubonic plague is briefly described and recent studies investigating the mechanisms by which these unique and deadly biofilms are formed are discussed.     

Exposure of small rodents to plague during epizootics in black-tailed prairie dogs

Plague, caused by the bacterium Yersinia pestis, causes die-offs of colonies of prairie dogs (Cynomys ludovicianus). It has been argued that other small rodents are reservoirs for plague, spreading disease during epizootics and maintaining the pathogen in the absence of prairie dogs; yet there is little empirical support for distinct enzootic and epizootic cycles. Between 2004 and 2006, we collected blood from small rodents captured in colonies in northern Colorado before, during, and for up to 2 yr after prairie dog epizootics. We screened 1,603 blood samples for antibodies to Y. pestis, using passive hemagglutination and inhibition tests, and for a subset of samples we cultured blood for the bacterium itself. Of the four species of rodents that were common in colonies, the northern grasshopper mouse (Onychomys leucogaster) was the only species with consistent evidence of plague infection during epizootics, with 11.1-23.1% of mice seropositive for antibody to Y. pestis during these events. Seropositive grasshopper mice, thirteen-lined ground squirrels (Spermophilus tridecemlineatus), and deer mice (Peromyscus maniculatus) were captured the year following epizootics. The appearance of antibodies to Y. pestis in grasshopper mice coincided with periods of high prairie dog mortality; subsequently, antibody prevalence rates declined, with no seropositive individuals captured 2 yr after epizootics. We did not detect plague in any rodents off of colonies, or on colonies prior to epizootics, and found no evidence of persistent Y. pestis infection in blood cultures. Our results suggest that grasshopper mice could be involved in epizootic spread of Y. pestis, and possibly, serve as a short-term reservoir for plague, but provide no evidence that the grasshopper mouse or any small rodent acts as a long-term, enzootic host for Y. pestis in prairie dog colonies.     

Analysis of insect toxin complex gene variability of Yersinia pestis and Yersinia pseudotuberculosis strains

The nucleotide sequences of the Tc's insect toxin complex genes have been analyzed in 18 natural strains of the main and non-main subspecies of Yersinia pestis isolated in different natural foci in the Russian Federation, as well as neighboring and more remote countries, as compared to the data on Y. pestis and Y. pseudotuberculosis strains stored in the NCBI GenBank database. The nucleotide sequences of these genes in plague agent strains have been found to be highly conserved, in contrast to those of the pseudotuberculosis agent. The sequences of two genes, tcaC and tccC2, have been found to be almost identical in Y. pestis strains, whereas other three genes (tcaA, tcaB, and tccC1) contain a few mutations, which, however, are not common for all strains of the plague agent. Exceptions are only strains of the Y. pestis biovar orientalis, whose tcaB gene is in a nonfunctional state due to a nucleotide deletion. The results suggest that the formation of the species Y. pestis as an agent of a natural focal infection with a transmissive mechanism has not resulted in degradation of the Tc's complex genes. Instead, these genes are likely to have been altered as the plague agent have been adapting to the new environment.