细菌分泌系统与茄科雷尔氏菌致病机理的关系研究进展

青枯病(bacterial wilt)的致病菌茄科雷尔氏菌Ralstonia solanacearum主要通过Ⅲ型及Ⅱ型分泌系统等将多种毒性因子输送到细胞外而使寄主植物致病。主要综述了近年来茄科雷尔氏菌Ⅲ型和Ⅱ型分泌系统的Phc、Prh、EPS和Peh 4个调控网络与该病原菌致病性之间的关系,以及2个分泌系统相互之间的关系。可为进一步研究该病害的作用机理及寻找其致病性靶标提供参考。     

Ultrastructural and cell wall modifications during infection of <Emphasis Type="Italic">Eucalyptus viminalis</Emphasis> roots by a pathogenic <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> strain

Fusarium species are soil-borne fungal pathogens that produce a variety of disease symptoms when attacking crop plants. The mode of root colonization of Eucalyptus viminalis seedlings by a pathogenic F. oxyporum strain (Foeu1) at the ultrastructural level and changes in cell wall pectin during host pathogen interactions are described. Root systems of E. viminalis plants were inoculated with F. oxysporum in an in vitro model system. Hyphae of F. oxysporum adhered to the outer epidermal cell walls through fibrillar material, and after penetration they spread into the internal tissues. They developed intercellularly and intracellularly in the root cortex and invaded vascular tissues. Papillae were induced, and the host plasma membrane ruptured in colonized cells, causing rapid host tissue and cell damage. Changes in distribution and occurrence of nonesterified and methyl-esterified pectins were evaluated after root colonization by F. oxysporum using two monoclonal antibodies, JIM 5 and JIM 7, respectively. Nonesterified pectin in control roots was mainly localized in the epidermal cell walls and middle lamellae in parenchymal cortex, whereas methyl-esterified pectin accumulated more in primary cell walls of the cortex and phloem. Decreases in immunodetected nonesterified and methyl-esterified pectins were associated with extensive plant tissue degradation after root colonization by the pathogenic fungus.     

Experimental Leptospira borgpetersenii serovar hardjo infection of pregnant cattle

Objective To observe the effect upon the foetus of experimental infection of pregnant cattle with Leptospira borg-petersenii serovar hardjo .
Design A disease transmission study using pregnant cattle.
Procedure Fourteen heifers serologically negative to L hardjo were artificially inseminated and later challenged with a north-Queensland isolate of L hardjo by conjunctival inoculation. The heifers were serologically monitored and their urine examined for the presence of leptospires using culture and fluorescent-antibody tests at appropriate intervals. Elective caesarean sections were performed on pregnant heifers at 6.5 weeks after the challenge. Foetuses were examined using serological, histopathological, microbiological and fluorescent-antibody tests.
Results Ten of the heifers became pregnant, but three subsequently aborted before challenge. After challenge, all 14 heifers seroconverted and L hardjo was isolated from the urine of 6 of the 7 pregnant heifers. No evidence of foetal L hardjo infection was detected. Two of the foetuses had histopatho-logical lesions consistent with Neospora s p infection.
Conclusion It is likely that the isolate of L hardjo used in this study does not normally infect the foetus. Neospora s p may be a more significant cause of bovine reproductive wastage.     

SARS-CoV-2 infection in farmed minks,associated zoonotic concerns,and importance of the One Health approach during the ongoing COVID-19 pandemic

The coronavirus disease 2019 (COVID-19) pandemic has now affected over 72.5 million people worldwide, with nearly 1.6 million deaths reported globally as of December 17, 2020. SARS-CoV-2 has been implicated to have originated from bats and pangolins, and its intermediate animal hosts are being investigated. Crossing of the species barrier and exhibition of zoonosis have been reported in SARS-CoV-2 in farm (minks), domesticated (cats and dogs), and wild animals (tigers, puma, and lions). Recently, the rapid spread of SARS-CoV-2 infection was reported in mink farms, which led to the death of a myriad minks. The clinical and pathological findings of SARS-CoV-2 infection and the rapid animal-to-animal transmission in minks are almost similar to the findings observed in patients with COVID-19. Additionally, the rapid virus transmission among minks and the associated mutations resulted in a new mink-associated variant that was identified in both minks and humans, thereby providing evidence of mink-to-human transmission of SARS-CoV-2. The new mink-associated SARS-CoV-2 variant with a possible reduced sensitivity to neutralizing antibodies poses serious risks and is expected to have a direct effect on the diagnostic techniques, therapeutics, and vaccines that are currently under development. This article highlights the current evidence of SARS-CoV-2 infection in farmed minks, and provides an understanding of the pathogenesis of COVID-19 in minks and the associated zoonotic concerns of SARS-CoV-2 transmission from minks to humans with an emphasis on appropriate mitigation measures and on the necessity of adopting the One Health approach during the COVID-19 pandemic.     

A systematic study of Tupaia as a model for human acute hepatitis B infection

The molecular features of hepatitis B virus (HBV) infection, eradication, and pathogenesis are poorly understood, partly due to the lack of an adequate animal model that faithfully reproduces the course of infection. Although Tupaia belangeri were previously recognized as HBV-susceptible animals, the course of infection in adult tupaias remains obscure. Herein, we performed a longitudinal study and demonstrated that adult tupaias were efficiently infected (90% infection rate) with 10⁸ copies of the HBV genome. HBV replicated vigorously, produced high levels of covalently closed circular DNA (cccDNA) in hepatocytes, and released hepatitis B surface antigen (HBsAg), hepatitis Be antigen (HBeAg), and HBV DNA into the serum at day 9 post-inoculation (p.i.), which then decreased on day 15 p.i. The kinetics were consistent with the expression of liver HBsAg and HBeAg, as determined with immunohistochemistry. The viral products in serum at day 9 and 15 p.i. represented de novo synthesized viral products, as treatment with a viral entry inhibitor completely abolished these products from the serum. Viral clearance and serological conversion occurred at day 21 p.i. and were accompanied by elevated alanine transaminase (ALT) levels and liver pathology, such as inflammatory infiltration and hepatocyte ballooning degeneration. Although ALT levels eventually returned to normal levels by day 42 p.i., the liver pathology persisted until at least day 120 p.i. The HBV infection process in tupaia, therefore, exhibits features similar to that of human acute HBV infection, including viral replication, viral eradication, ALT elevation, and liver pathology. Thus, adopting the tupaia model to study host-HBV interactions presents an important advance which could facilitate further investigation and understanding of human HBV infection, especially for features like cccDNA that current small-animal models cannot effectively model.     

猪戊型肝炎病毒4型感染新西兰大白兔肝脏和脑组织中IL-4与IL-5的表达

为了解细胞因子IL-4和IL-5在戊型肝炎病毒(HEV)感染中的表达及其作用,以新西兰大白兔为模型,腹腔注射感染HEV-4,攻毒后第7、14、21、28、35天对兔的心、肝、脑、肾等进行组织病理学观察,应用实时荧光定量PCR对肝脏、脑等器官中IL-4和IL-5的表达水平及变化进行检测.结果显示,肝脏中IL-4和IL-5...     

两株H4N3禽流感病毒全基因组序列分析及对小鼠的致病性研究

2009年在我国南方活禽交易市场进行流行病学调查时,从鸭体内分离到2株H4N3亚型禽流感病毒(AIV),DK/FJ/S1419/09(H4N3)(FJ/419/2009)和DK/HUN/S1010/09(H4N3)(HuN/010/2009)。为了解这2株H4N3亚型AIV的生物学特性,本研究对其进行全基因组分析及对小鼠致病性研究。结果显示:其HA基因来源于近两年流行的H4亚型病毒株,NA基因来源于其它亚型病毒株。内部基因来源较复杂,与FJ/419/2009内部基因同源性最高的病毒株均来自国内H5、H6等亚型分离株,但与HuN/010/2009同源的内部基因则差异较大,与PA、M和NS同源性最高的病毒株分别为A/wild/duck/Korea/UP122/2007(H1N1),A/muscovy/duck/Thailand/CU-LM1983/2009(H4N6)and A/avian/Japan 8KI0068/2008(H3N6)。用106EID50病毒剂量感染6周龄BALB/c小鼠,结果显示试验组小鼠感染后第3 d采脏器样品,仅在鼻甲和肺部能检测到病毒存在。以上数据表明,尽管这2株H4N3特殊亚型组合病毒来源复杂,但对小鼠的致病性较低。     

生物体中位点2切割蛋白酶在致病菌致病机理方面的研究进展

膜内切割蛋白酶在信号传导过程中起着重要作用。Site-2 proteases（简称s2p）属于膜内切割蛋白酶中的金属蛋白酶类,如今在大多数细菌基因组中都发现了s2p。然而目前除了具有代表性的Rsep和SpolVFB蛋白酶被人们熟知之外,s2p更多的作用还未被发现。笔者就其实验结果以及结合最新关于s2p蛋白的研究数据,对s2p在细菌体内的生理生化作用及其在致病菌内致病过程中所起到作用展开一定的讨论。     

兔病毒性出血症发病机理的初步研究

兔病毒性出血症是兔的一种败血性传染病,通过电镜观察和免疫胶体金-银法的监测,病毒最先侵害的靶器官是肝、脾和肺,然后到达全身血流,最后分布到其它器官。发现动物在感染后18～24小时,在肝、脾、肺、肾和肠上皮细胞、血管壁内皮细胞、循环的中性白细胞、淋巴细胞及肥大细胞的核内有病毒颗粒,其直径为32～34nm,无囊膜。感染后24小时直到死亡前,大部分病毒颗粒被释放到细胞浆和间质中去。初步认为本病是由于病毒血症对各器官的直接损伤,尤其对血管壁的损伤,导致全身弥散性血管内凝血(DIC)及全身性出血。由于血液的丧失,继而使全身各器官发生缺氧,最终引起生命重要器官的功能衰竭而死亡。