Experimental infection with BCG as a model of tuberculosis in the brushtail possum (Trichosurus vulpecula)

AIMS: To study the development and progression of lesions produced following experimental inoculations of possums with Bacille Calmette-Guérin (BCG) Pasteur Strain 1173P2 and to compare these with lesions that occurred following natural Mycobacterium bovis infection.

METHODS: Possums were inoculated with 5 x 10⁶ colony forming units (cfu) of BCG via the intra-dermal (I/D) route into the dorsum of the neck (n=38) or the left brachium (n=7), orally (n=10), via the endo-bronchial (E/B) route (n=12), or intravenously (I/V) (n=10, half of which received 5 x 10⁶ cfu and half of which received 5 x 10⁷ cfu of BCG). The possums were humanely killed between 1–4 weeks post inoculation (p.i.), and the nature and distribution of lesions examined grossly and histopathologically.

RESULTS: The distribution of lesions following I/D inoculation via either route was similar to that of the natural disease, but there were few lesions in the lung. Endo-bronchial inoculation resulted in pulmonary disease but produced few lesions outside the respiratory tract. Lesions produced by I/V inoculation were similar in distribution to those seen in terminally ill tuberculous possums. No lesions were produced following oral inoculation. Regression of lesions commenced after 3 weeks p.i.

CONCLUSIONS: Although the phenomenon of lesion resolution restricts the use of BCG to the study of early lesion development, it avoids the overwhelming disease induced using M. bovis and thus allows the early phases of the development and progression of tuberculosis in this species to be observed. Intra-dermal inoculation produced evidence that infection through the skin is associated with lesions in superficial lymph nodes, whereas pulmonary disease was associated with E/B inoculation. The results are consistent with the hypothesis that both percutaneous and respiratory routes are important in natural infection of possums with M. bovis.     

奶牛乳房炎的研究进展及防控措施

奶牛乳房炎发病率高且危害大,在奶牛养殖中属于常见疾病。该病主要是由于病原微生物入侵奶牛乳腺组织而引发的局部炎症,其不仅会造成奶牛产奶量降低,而且还会影响牛奶的品质。由于治疗过程中的兽药残留和由某些病原微生物感染引起的奶牛乳房炎治愈率低等问题,奶牛乳房炎的防治显得极为重要。从病原菌的种类、致病机理以及诊断方法和防控措施等方面介绍了奶牛乳房炎的研究进展,以期为奶牛乳房炎的科学防治提供参考。     

H9N2亚型禽流感病毒反向遗传操作平台的建立

H9N2亚型禽流感病毒(AIV)在自然界中广泛存在和传播,给养禽业造成了巨大损失。为了进一步揭示该病毒的致病机制,本研究采用RT-PCR技术扩增禽流感病毒A/Chicken/Shanghai/1/2006(简称SH1)的PB2、PB1、PA、HA、NP、NA、M、NS 8个基因片段,并分别克隆至PLLB双向表达载体上。采用8质粒系统共转染293T细胞,转染48 h后加入TPCK胰酶作用2 h,将上清液和细胞一同接种9~11日龄SPF鸡胚,并检测其血凝效价。经序列比对,拯救获得的病毒rSH1的8个基因片段序列均与亲本病毒SH1的序列相同。实验结果表明,本研究成功建立了H9N2亚型禽流感病毒反向遗传操作系统,为该病毒的致病机理和传播机制研究等奠定了技术平台。     

HA蛋白位点变异影响H7N9亚型流感病毒特性的研究进展

2013年春，我国首次出现人感染H7N9亚型禽流感疫情，对家禽养殖和公众健康均产生了严重危害，并且在第5波流行期又演变出血凝素（hemagglutinin，HA）蛋白裂解位点处存在插入突变的高致病性禽流感病毒株。HA作为A型流感病毒表面表达丰度最高的糖蛋白，在介导病毒与宿主细胞表面受体的结合、促进病毒囊膜与细胞膜的融合、刺激机体产生中和抗体等方面具有至关重要的作用。本文围绕H7N9病毒，简要综述了HA蛋白的结构与功能，及其关键功能氨基酸位点变异影响病毒生物学特性的研究进展，以期为深入解析HA蛋白在H7N9病毒感染致病中的作用提供重要参考。     

烟草青枯病研究进展

详细介绍了烟草青枯病的发病症状、病原、致病性、生化型、发病动态、流行规律、致病机理和综合防治措施,为烟草青枯病的进一步研究提供参考。     

猪附红细胞体致病机理的研究进展

作者综述了猪附红细胞体的致病机理,其主要包括4个方面:①猪附红细胞体引起红细胞膜改变,导致自身免疫溶血性贫血;②使机体产生自身抗体即M型冷凝素,导致红细胞凝集、溶解和机体Ⅱ型过敏反应;③使血液葡萄糖水平降低,机体出现酸中毒,被感染的红细胞携带氧气的能力下降,常导致机体呼吸困难;④当出现严重的寄生虫血症时,抑制猪的免疫反应。     

镰刀菌毒素对植物形态和结构的影响

镰刀菌毒素是镰刀菌产生的非寄主选择性毒素,可导致植物萎蔫、根腐、穗腐等各种病症。本文综述了镰刀菌毒素的主要种类、产毒菌种及其侵染的主要植物,毒素作用机理及其对植株外观形态、细胞及细胞器结构、维管束等的影响,并提出了镰刀菌毒素研究在抗性材料筛选和抗性机理研究方面的应用前景。     

乙型肝炎病毒的研究进展

乙型肝炎病毒（Hepatitis B Virus,HBV）是目前己知的最小动物DNA病毒之一.由HBV所引起的乙型肝炎是一种流行久远、传播广泛、危害严重的传染性疾病。目前,全世界约有4亿多人携带HBV,平均每年约有100万人死于HBV相关的肝癌。在中国,每年约有50万人死于HBV感染导致的晚期肝硬化和肝癌,本文从乙肝病毒的特征,基因组结构,变异与分型,复制和转录模式,发病机制,检测指标等方面等方面进行了综述。     

猫杯状病毒分子生物学特征及研究进展

猫杯状病毒（Feline calicivirus,FCV）是在猫科动物中高度流行的重要病原体,能够引起猫科动物急性口腔溃疡、上呼吸道传染病和慢性胃肠炎等疾病。目前研究证明疫苗免疫可有效减少该病的发生。此外,已开展FCV反向遗传操作系统的研究,并成功表达外源基因,为进一步研究特定蛋白的结构和功能、病毒致病机理、构建杯状病毒嵌合载体疫苗打下了基础。本文从FCV的病原及生物学特性、基因组结构及其编码产物、致病机理、流行病学及疫病的防治等方面进行综合阐述。     

Restoring catalase activity in Staphylococcus aureus subsp. anaerobius leads to loss of pathogenicity for lambs

Staphylococcus aureus subsp. anaerobius, a microaerophilic and catalase-negative bacterium, is the etiological agent of abscess disease, a specific chronic condition of sheep and goats, which is characterized by formation of necrotic lesions that are located typically in superficial lymph nodes. We constructed an isogenic mutant of S. aureus subsp. anaerobius (RDKA84) that carried a repaired and functional catalase gene from S. aureus ATCC 12600, to investigate whether the lack of catalase in S. aureus subsp. anaerobius plays a role in its physiological and pathogenic characteristics. The catalase activity had no apparent influence on the in vitro growth characteristics of RDKA84, which, like the wild-type, did not grow on aerobically incubated agar plates. Restoration of catalase activity in RDKA84 substantially increased resistance to H₂O₂ when analyzed in a death assay. The intracellular survival rates of the catalase-positive mutant RDKA84 in polymorphonuclear neutrophils (PMN) isolated from adult sheep were significantly higher than those of the wild-type, while no differences were found with PMN isolated from lambs. RDKA84 showed significantly lower survival rates in murine macrophages (J774A.1 cells) than the wild-type strains did, whereas, in bovine mammary epithelial cells (MAC-T), no differences in intracellular survival were observed. Interestingly, the virulence for lambs, the natural host for abscess disease, of the catalase-positive mutant RDKA84 was reduced dramatically in comparison with wild-type S. aureus subsp. anaerobius in two experimental models of infection.