流感嗜血杆菌ATCC49247来源的IgA酶理化性质及其对低糖基化IgA1的分解作用

【背景】近年来,能够特异性切割人IgA1分子的IgA蛋白酶(IgA酶)被认为是治疗IgA肾病(IgAN)的潜在药物,但各种物理化学因素均可能影响其生物学活性。【目的】研究流感嗜血杆菌(Haemophilus influenzae) ATCC49247 IgA酶的理化性质,确定IgA酶最适的作用条件后观察IgA酶对低糖基化IgA1的作用。【方法】从细菌培养液中分离纯化IgA酶,SDS-PAGE电泳后银染法分别检测多种理化条件下IgA酶的水解活性及其对低糖基化IgA1的消化作用。【结果】H. influenzae ATCC49247IgA酶可耐受的反应温度较广,最适温度为50°C;在高于60°C的环境中,IgA酶便不可逆地丧失了稳定性;IgA酶在pH 6.0-9.0的环境下能够保持完整催化活性;1 mmol/L的PMSF和高于10 mmol/L的SDS能够强烈地抑制IgA酶的活性,DTT和EDTA对IgA酶活性无明显影响;所有浓度的Al~(3+)、Fe~(3+)和高浓度的Cu~(2+)、Zn~(2+)、Fe~(2+)对IgA酶均表现出强烈的抑制作用,同时Co~(2+)、Mn~(2+)、Ca~(2+)、Ni~(2+)和Mg~(2+)都对IgA酶活性没有明显影响。选择了最适宜的IgA酶作用条件,发现IgA酶能够有效降解低糖基化IgA1底物。【结论】确定IgA酶最适宜的作用条件能保持良好的酶活性,更好地发挥了IgA酶对低糖基化IgA1的降解作用,为IgA酶的临床研究和药用价值的进一步开发提供一定的依据。     

A chalcone with potent inhibiting activity against biofilm formation by nontypeable Haemophilus influenzae

Nontypeable Haemophilus influenzae (NTHi), an important human respiratory pathogen, frequently causes biofilm infections. Currently, resistance of bacteria within the biofilm to conventional antimicrobials poses a major obstacle to effective medical treatment on a global scale. Novel agents that are effective against NTHi biofilm are therefore urgently required. In this study, a series of natural and synthetic chalcones with various chemical substituents were evaluated in vitro for their antibiofilm activities against strong biofilm‐forming strains of NTHi. Of the test chalcones, 3‐hydroxychalcone (chalcone 8 ) exhibited the most potent inhibitory activity, its mean minimum biofilm inhibitory concentration (MBIC₅₀) being 16 μg/mL (71.35 μM), or approximately sixfold more active than the reference drug, azithromycin (MBIC₅₀ 419.68 μM). The inhibitory activity of chalcone 8 , which is a chemically modified chalcone, appeared to be superior to those of the natural chalcones tested. Significantly, chalcone 8 inhibited biofilm formation by all studied NTHi strains, indicating that the antibiofilm activities of this compound occur across multiple strong‐biofilm forming NTHi isolates of different clinical origins. According to antimicrobial and growth curve assays, chalcone 8 at concentrations that decreased biofilm formation did not affect growth of NTHi, suggesting the biofilm inhibitory effect of chalcone 8 is non‐antimicrobial. In terms of structure–activity relationship, the possible substituent on the chalcone backbone required for antibiofilm activity is discussed. These findings indicate that 3‐hydroxychalcone (chalcone 8 ) has powerful antibiofilm activity and suggest the potential application of chalcone 8 as a new therapeutic agent for control of NTHi biofilm‐associated infections.     

b型流感嗜血杆菌培养及细菌溶解产物制备工艺研究

目的研究b型流感嗜血杆菌(Haemophilus influenza type b,Hib)培养条件及细菌溶解产物制备工艺。方法比较Hib在传统培养基和改良培养基的生长情况,优化改良培养基在生物反应器中对Hib培养条件(p H值、温度、溶解氧等),研究最佳菌体细胞破碎方法及细菌溶解产物纯化制备工艺。结果改良培养基可代替传统培养基用于Hib的生产培养,且Hib在p H7.4、温度为36℃、溶解氧为25%的改良培养基中,生长迅速,菌体产量最高。高压匀浆破碎法的破碎效果明显优于超声波破碎法,破碎效果达到98%以上,纯化后的细菌溶解产物的多糖含量、总氮含量、蛋白质含量、核酸含量及细菌内毒素含量均符合《中华人民共和国药典》(三部)2010版中b型流感嗜血杆菌结合疫苗的质量标准。结论初步建立了b型流感嗜血杆菌培养及细菌溶解产物制备工艺。     

Effects of lipid environment on the conformational changes of an ABC importer

In order to shuttle substrates across the lipid bilayer, membrane proteins undergo a series of conformation changes that are influenced by protein structure, ligands, and the lipid environment. To test the effect of lipid on conformation change of the ABC transporter MolBC, EPR studies were conducted in lipids and detergents of variable composition. In both a detergent and lipid environment, MolBC underwent the same general conformation changes as detected by site-directed EPR spectroscopy. However, differences in activity and the details of the EPR analysis indicate conformational rigidity that is dependent on the lipid environment. From these observations, we conclude that native-like lipid mixtures provide the transporter with greater activity and conformational flexibility as well as technical advantages such as reconstitution efficiency and protein stability.     

Intranasal immunization with a lipooligosaccharide-based conjugate vaccine from nontypeable Haemophilus influenzae enhances bacterial clearance in mouse nasopharynx

Nontypeable Haemophilus influenzae (NTHi) is a major cause of otitis media in children. We investigated whether intranasal immunization with a detoxified lipooligosaccharide-tetanus toxoid (dLOS-TT) conjugate vaccine would generate protective immunity against NTHi in a mouse model of nasopharyngeal clearance. The results demonstrated that intranasal immunization with dLOS-TT plus adjuvant cholera toxin (CT) significantly induced LOS-specific IgA antibodies in mouse external secretions, especially in nasal wash (90-fold), bronchoalveolar lavage fluid (25-fold), saliva (13-fold) and fecal extract (three-fold). LOS-specific IgA antibody-forming cells were also found in mucosal and lymphoid tissues with their highest numbers in the nasal passage (528 per 10(6) cells). In addition, the intranasal immunization elicited a significant rise in LOS-specific IgG (32-fold) and IgA (13-fold) in serum. For the immunized mice which had been challenged through the nose with 10(7) live NTHi strain 9274 cells, the vaccine group showed a significant reduction (74-77%) of NTHi, compared to that of control groups with CT alone or dLOS plus CT (P<0.05). Negative correlations were found between bacterial counts and the levels of nasal wash IgA or IgG, saliva IgA and serum IgG. The clearance of five heterologous strains was investigated and revealed a significant clearance of strains 3198, 5657 and 7502 but not of strains 1479 and 2019. These data suggest that intranasal immunization with dLOS-TT vaccine elicits both mucosal and systemic immunity against NTHi and enhances bacterial clearance from nasopharynx in mice. Such a vaccine and vaccination regime may be applicable to humans with an appropriate formulation.     

临床分离嗜血杆菌的菌群分布及其耐药性分析

目的调查中山大学附属第一医院嗜血杆菌的临床分布及耐药性情况。方法按照标准方法分离嗜血杆菌并进行药物敏感试验及其检测：结果共分离出146株嗜血杆菌,嗜血杆菌对青霉素敏感率仅为14％,对氨苄西林、头孢克洛、头孢丙烯、莫西沙星、阿奇霉素的敏感率分别为77．9％,98．2％,98．2％,68．7％,98．3％。结论头孢克洛、头孢丙烯、阿奇霉素是治疗嗜血杆菌感染的有效抗生素,应加强对嗜血杆菌的培养及耐药性监测工作。     

重组不可分型流感嗜血杆菌E蛋白与血浆脂蛋白(a)的相互作用

目的:E蛋白(Protein E,PE)是不可分型流感嗜血杆菌(Nontypeable Haemophilus influenza,NTHi)表面的一种纤溶酶原(plasminogen,Plg)受体,其C末端含有两个赖氨酸残基。NTHi可通过其表面的PE与Plg结合,从而利用机体的纤溶系统深层入侵宿主。基于脂蛋白(a)[Lipoprotein(a),Lp(a)]中载脂蛋白(a)[Apolipoprotein(a),Apo(a)]与Plg高度的同源性,拟证明Lp(a)是否会与重组表达的PE(r PE)结合。方法:原核表达并纯化r PE及敲除C末端两个赖氨酸残基的r PEΔKK,密度梯度离心结合阴离子交换层析分离人血浆Lp(a),通过ELISA、Pull down、Western blot等方法研究r PE与Lp(a)的相互作用。结果:r PE与Lp(a)结合,但不与LDL结合,且r PEΔKK与Lp(a)的结合能力明显低于r PE;赖氨酸类似物6-氨基乙酸(EACA)能有效抑制r PE与Lp(a)的结合;Lp(a)对r PE与Plg的结合具有微弱的抑制作用。结论:r PE能够与Lp(a)结合,其中r PE的C末端赖氨酸残基和Apo(a)的赖氨酸结合位点(lysine binding sites,LBS)是r PE与Lp(a)结合的主要位点。     

Modelling of endemic carriage of Haemophilus influenzae in Aboriginal infants in Northern Australia

Aboriginal infants and children in rural communities in Northern Australia have high rates of nasopharyngeal carriage of nonencapsulated Haemophilus influenzae (NCHi), with positive swab rates of 76%. In this population, the acquisition of NCHi from soon after birth is associated with the onset of otitis media and with muco-purulent nasal discharge, while the long-term persistence of NCHi carriage is associated with the acquisition and turnover of large numbers of antigenically diverse strains. Mathematical models have been fitted to data on the acquisition and loss of encapsulated strains of H. influenzae and 43 different strains of NCHi in 10 children followed from early infancy for up to 2 years. Subject to plausible assumptions, the preferred model estimated the mean time to acquisition of a H. influenzae strain to be 7 days after first becoming exposed after birth. For an infant already carrying H. influenzae, each additional strain was acquired after a mean waiting period of 45 days. On average, 1.50 different strains of H. influenzae were detected in four colonies routinely typed from each positive swab, but it was estimated that another 2.55 strains were 'hidden' behind these more frequent strains. With an average of 4.05 strains per carrier, it was estimated that each strain was carried for an average of 137 days, although detected on only 37% of occasions. Thus we have developed mathematical models that provide estimates for duration of colonisation, time to colonisation, and number of colonising strains in a population in which H. influenzae is highly endemic, characterised by sequential and concurrent carriage of multiple strains in each infant.