Preparation and application of a novel monoclonal antibody specific for the heat shock protein 60 of Lawsonia intracellularis

Porcine proliferative enteropathy(PPE),an important infectious disease in pig production caused by an obligate intracellular bacterium Lawsonia intracellularis,is commonly associated with diarrhea and reduced weight gain in growing pigs widespread.An accurate method for detecting L.intracellularis is particularly important for preventing and controlling PPE.Heat shock protein 60(Hsp60)is an immunodominant bacterial antigen found in all eukaryotic and prokaryotic organisms.Thus,the purpose of the current investigation was to produce a novel L.intracellularis Hsp60 monoclonal antibody(mAb)useful for immunodiagnostics.Three hybridomas secreted anti-Hsp60 termed 3E5,4E2,and 9G6 were generated,and the titers of ascitic fluids of 3E5,4E2,9G6 were 1:1024000,1:2048000 and 1:2048000,respectively.The Western blotting analysis demonstrated that recombinant Hsp60(rHsp60)was recognized by mAbs 3E5,4E2 and 9G6.Subsequently,analyses of specificity showed all the mAbs were highly specific to L.intracellularis while could not significantly react with other enteric bacteria commonly found in the ileum of pigs,such as Escherichia coli,Salmonella Choleraesuis,Salmonella Typhimurium,and Brachyspira hyodysenteriae.Furthermore,the mAbs were useful for detecting L.intracellularis in the infected monolayer cells and histological sections of the ileum from PPE-affected pigs.Our research will provide a foundation for the development of immunological diagnostic tests.

Molecular epidemiology, characterization of virulence factors and antibiotic resistance profile of Streptococcus agalactiae isolated from dairy farms in China and Pakistan

Streptococcus agalactiae is one of the most common pathogens that cause bovine mastitis worldwide. Identifying pathogen prevalence and virulence factors is critical for developing prevention and control approaches. Herein, 1 161 milk samples from various dairy farms in China(n=558) and Pakistan(n=603) were collected between 2019–2021 and were subjected to S. agalactiae isolation. Prevalence, serotyping, virulence genes, and antibiotic-resistant genes of S. agalactiae were evaluated by PCR assay. All isolates were characterized for haemolysis, biofilm production, cytotoxicity, adhesion, and invasion on bovine mammary epithelial cells. The prevalence of S. agalactiae-induced mastitis in cattle was found to be considerably higher in Pakistan than in China. Jiangsu and Sindh provinces had the highest area-wise prevalence in China and Pakistan, respectively. Serotypes Ia and II were prevalent in both countries, whereas serotype III was found only in Pakistan. Moreover, all isolates tested positive for PI-2b gene but negative for PI-1 and PI-2a genes. All isolates harboured cfb, cylE, hylB, and fbsB virulent genes, whereas many of them lacked bibA, rib and bca. However, the absence of bac and scp genes in Chinese isolates and cspA in Pakistani isolates was noted, while spb1 and lmb were not detected in isolates of both countries. Pakistani isolates, particularly serotype Iapositive, had a considerably higher ability to produce biofilm, haemolysis, cytotoxicity, adhesion, and invasion than Chinese isolates. Most of the isolates were phenotypically resistant to tetracycline, erythromycin, and clindamycin and genotypic resistance was confirmed by the presence of ermA, ermB, tetM and tetO genes. Our study highlights the antimicrobial resistance profile and virulence-related factors contributing to the epidemiological spread of mastitis-causing S. agalactiae in China and Pakistan. The findings may facilitate future studies designed to develop improved treatment and control strategies against this pathogen.

The vital role of CovS in the establishment of Streptococcus equi subsp.zooepidemicus virulence

Streptococcus equi subsp.zooepidemicus(SEZ)is an important zoonotic agent.Here,a virulence-attenuated strain M35246 derived from natural variation of wild-type SEZ ATCC35246 was found.M35246 showed a deletion of 25contiguous genes as well as a loss-of-function mutation in covS.Subsequently,a 25-gene-deleted strain(ΔPI),a covS-mutant strain(Mcov S),and relevant complementary strains were constructed and investigated.M35246 and Mcov S were significantly less encapsulated and exhibited poorer anti-phagocytic capacity compared to wild-type SEZ.McovS was significantly more sensitive toβ-lactams,aminoglycosides,macrolides,and lincosamides than wild-type SEZ.M35246,McovS,andΔPI exhibited an increase in median lethal dose(LD_(50))in mice by 10~5,10~5,and 5 times when compared to wild-type SEZ,respectively.Neither M35246 nor McovS were isolated from mice 48 h after being challenged with approximately 2000 times the LD_(50)of wild-type SEZ.Transcriptome analysis showed that 668 significantly differentially expressed genes existed between McovS and wild-type SEZ.Numerous virulence factor-encoding genes and anabolicrelated genes in McovS that were involved in anti-phagocytosis,capsule formation,pathogenicity,and antibiotic resistance were downregulated significantly relative to the wild-type strain.This study revealed that the CovS plays a vital role in the establishment of SEZ virulence.

电子基板用玻璃/陶瓷复合材料的低温共烧与性能

玻璃/陶瓷低温共烧复合材料具有高导热性、快速电子信号传输性能、热膨胀系数与硅匹配、力学性能良好等优点,被广泛应用作电子基板材料。本文简要阐述了玻璃/陶瓷复合材料的烧结机理和影响因素,综述了主要的制备方法,指出了烧结过程中可能存在的关键问题,并讨论了玻璃/陶瓷复合材料的性能调控方法。最后,展望了玻璃/陶瓷复合材料在电子信息领域的发展方向和应用前景。

白光LED用Phosphor-on-Glass(PoG)材料的制备与表征

采用商业Ce^3+∶YAG荧光粉包埋钇铝硅酸盐玻璃并在该体系玻璃转变温度附近进行烧结的方法,成功制备了荧光粉粘附在玻璃表面上的复合材料(Phosphor-on-Glass,PoG)。利用XRD、SEM和荧光光谱仪等研究了PoG材料的物相、显微结构和变温发光性能。研究结果表明:PoG材料结构为荧光粉/玻璃/荧光粉复合体,Ce^3+∶YAG荧光粉粘附在玻璃上下表面且均匀分布,其形貌与颗粒大小未发生明显变化。固定烧结时间为10h,PoG材料的荧光强度随着烧结温度的增加先增强后减弱;PoG材料的发光抗热淬灭性能较好(热激活能为0.22eV),这说明Ce^3+∶YAG荧光粉的优良发光性能在PoG材料中得到了很好地保存。以PoG材料封装的白光LED样品在100mA电流驱动下,获得白光输出,其中最接近纯白光(0.33,0.33)的LED光效为69.8lm/W,相关色温为5873K,显色指数72.3。由于Ce^3+∶YAG荧光粉缺乏红色发光,尝试在钇铝硅酸盐玻璃基质中掺杂Eu3+以增加红色发光部分,获得光效为52.1lm/W,相关色温为3910K,显色指数75.8的暖白光输出。

Sn^(2+)-Mn^(2+)共掺杂Gd_(2)O_(3)-Al_(2)O_(3)-SiO_(2)玻璃光致发光性能与能量传递

通过传统的高温熔融淬火技术制备了Sn^(2+)-Mn^(2+)共掺杂的Gd_(2)O_(3)-Al_(2)O_(3)-SiO_(2)(GAS∶0.5Sn^(2+),yMn^(2+))玻璃。研究了玻璃的光致发光特性和Sn^(2+)-Mn^(2+)能量传递过程。在365 nm激发下,随着Mn^(2+)浓度的增加(1.0%,1.5%,2.0%,2.5%,3.0%,3.5%,4.0%),玻璃中Sn^(2+)的发光强度逐渐降低,而Mn^(2+)的发光强度逐渐增大。Sn^(2+)的衰减时间随着Mn^(2+)含量的增加而减小,玻璃中产生了Sn^(2+)到Mn^(2+)离子的能量传递。GAS∶0.5Sn^(2+),yMn^(2+)玻璃的光致发光量子产率(PLQY)随着Mn^(2+)含量的增加而减小,其最大值为25.48%。玻璃中Mn^(2+)离子浓度达到4.0%时,其发光属于准白光发射,色坐标为(0.323,0.273)。另外,本文还研究了Sn^(2+)-Mn^(2+)共掺杂玻璃的发光热猝灭现象,Sn^(2+)发光中心电子跃迁所需克服的热激活能约为0.23 eV。

Evaluating the efficacy of an attenuated Streptococcus equi ssp. zooepidemicus vaccine produced by multi-gene deletion in pathogenicity island SeseCisland_4

Streptococcus equi ssp. zooepidemicus(SEZ) is a pathogen associated with a wild range of animal species. Frequent outbreaks have occurred in recent years in pigs, horses, goats and dogs which is liable to infect humans. There is a lack of efficient vaccines against this disease and the occurrence of antibiotic resistance may render drug therapies ineffective. In this study, gene deletion mutant(ΔSEZ) in pathogenicity islands SeseCisland_4 was constructed. The mutant ΔSEZ had a 52-fold decrease in 50% lethal dose(LD_(50)) and had less capacity to adhere epithelial cells. Importantly, immunization of mice with attenuated vaccine ΔSEZ at the dose of 10~2 colony-forming units(CFU) mL^(–1) elicited a significant humoral antibody response, with an antibody titer of 1:12 800. Therefore, 10~2 CFU mL^(–1) might be used as the appropriate immune dose for the attenuated vaccine ΔSEZ, which provided mice with efficient protection against virulent SEZ. In addition, the hyperimmune sera against 10~2 CFU m L–1 attenuated vaccine ΔSEZ could confer significant protection against virulent SEZ infection in the passive immunization experiment and exhibited efficient bactericidal activity in the whole blood assay. Meanwhile, no viable bacteria was detected in blood when mice were immunized with ΔSEZ at the dose of 10~2 CFU mL^(–1) via hypodermic injection. Thereafter, the mutant ΔSEZ at the dose of 10~2 CFU mL^(–1) could confer significant protection in mice and had less negative effects on host, which could be an effective attenuated vaccine candidate for the prevention of SEZ.