Characterization of humoral responses in mice immunized with plasmid DNAs encoding SARS-CoV spike gene fragments

The immunological characteristics of SARS-CoV spike protein were investigated by administering mice with plasmids encoding various S gene fragments. We showed that the secreting forms of S1, S2 subunits and the N-terminus of S1 subunit (residues 18-495) were capable of eliciting SARS-CoV specific antibodies and the region immediate to N-terminus of matured S1 protein contained an important immunogenic determinant for elicitation of SARS-CoV specific antibodies. In addition, mice immunized with plasmids encoding S1 fragment developed a Th1-mediated antibody isotype switching. Another interesting finding was that mouse antibodies elicited separately by plasmids encoding S1 and S2 subunits cooperatively neutralized SARS-CoV but neither the S1 nor S2 specific antibodies did, suggesting the possible role of both S1 and S2 subunits in host cell docking and entry. These results provide insights into understanding the immunological characteristics of spike protein and the development of subunit vaccines against SARS-CoV.     

Altered temperature induction sensitivity of the lambda pR/cI857 system for controlled gene E expression in Escherichia coli

Cell lysis of Gram-negative bacteria can be efficiently achieved by expression of the cloned lysis gene E of bacteriophage PhiX174. Gene E expression is tightly controlled by the rightward lambda pR promoter and the temperature-sensitive repressor cI857 on lysis plasmid pAW12. The resulting empty bacterial cell envelopes, called bacterial ghosts, are currently under investigation as candidate vaccines. Expression of gene E is stringently repressed at temperatures up to 30 degrees C, whereas gene E expression, and thus cell lysis, is induced at temperatures higher than 30 degrees C due to thermal inactivation of the cI857 repressor. As a consequence, the production of ghosts requires that bacteria have to be grown at 28 degrees C before the lysis process is induced. In order to reflect the growth temperature of pathogenic bacteria in vivo, it seemed favorable to extend the heat stability of the lambda pR promoter/cI857 repressor system, allowing pathogens to grow at 37 degrees C before induction of lysis. In this study we describe a mutation in the lambda pR promoter, which allows stringent repression of gene E expression at temperatures up to 36 degrees C, but still permits induction of cell lysis at 42 degrees C.     

活细胞单分子实时视见研究

我们对细胞生物学与分子生物学中有关分子事件和相互作用的认识,大部分都是集团平均水平研究的结果,并且基于所有的分子在给定时间内以完全相同的方式运动这样一种不真实的假设。现在,激光技术和全内反射显微镜的应用,以及绿色荧光蛋白(green fluorescent proteins,GFPs)等新的分子荧光探针的出现,使得显示活细胞单个生物分子的运动行为和轨迹成为可能。单分子水平的研究将会加深人们对分子和细胞生物学的基本概念的认识。     

青海省15岁以下儿童麻疹疫苗强化免疫分析

实验中对麻疹疫苗强化免疫前、后的现场进行了调查、评估并对麻疹监测系统和传染病报告系统的疫情资料进行了分析。结果表明,这次强化免疫接种儿童1100315人,报告接种率和调查接种率均>95%;接种后麻疹发病人数明显减少,发病率仅为0.66/10万,较强化免疫前发病率9.15/10万下降了82.51%,约有1/3不良反应者确诊为风疹;2006年7月—2007年6月麻疹监测系统数据显示,目前88%的麻疹病例发生在8月龄~14岁,约有32%病例为无免疫史或免疫史不详。高质量MV强化免疫能迅速降低麻疹发病,因此强化免疫接种人群的确定必须结合当地流行病学监测资料并尽可能在较大范围内开展,以形成有效的人群免疫屏障来阻断麻疹病毒的传播。保证>95%接种率是该次强化免疫活动的前提,同时须作好充分准备以应对可能发生预防接种时出现的不良反应。建议在提高常规免疫服务质量的情况下,每3~4年仍需开展后续强化免疫。     

Decision analysis approach to risk/benefit evaluation in the ethical review of controlled human infection studies

Risks and benefit evaluation for controlled human infection studies, where healthy volunteers are deliberately exposed to infectious agents to evaluate vaccine efficacy, should be explicit, systematic, thorough, and non-arbitrary. Decision analysis promotes these qualities using four steps: (1) determining explicit criteria and measures for evaluation, (2) identifying alternatives to the study, (3) defining the models used to estimate the measures for each alternative, and (4) running the models to produce the estimates and compare the alternatives. In this paper, we describe how decision analysis might be applied by funders and regulators, as well as by others contemplating the use of novel controlled human infection studies for vaccine development and evaluation.     

Using homology modeling to interrogate binding affinity in neutralization of ricin toxin by a family of single domain antibodies

In this report we investigated, within a group of closely related single domain camelid antibodies (V_HHs), the relationship between binding affinity and neutralizing activity as it pertains to ricin, a fast‐acting toxin and biothreat agent. The V1C7‐like V_HHs (V1C7, V2B9, V2E8, and V5C1) are similar in amino acid sequence, but differ in their binding affinities and toxin‐neutralizing activities. Using the X‐ray crystal structure of V1C7 in complex with ricin's enzymatic subunit (RTA) as a template, Rosetta‐based homology modeling coupled with energetic decomposition led us to predict that a single pairwise interaction between Arg29 on V5C1 and Glu67 on RTA was responsible for the difference in ricin toxin binding affinity between V1C7, a weak neutralizer, and V5C1, a moderate neutralizer. This prediction was borne out experimentally: substitution of Arg for Gly at position 29 enhanced V1C7's binding affinity for ricin, whereas the reverse (ie, Gly for Arg at position 29) diminished V5C1's binding affinity by >10 fold. As expected, the V5C1_R29G mutant was largely devoid of toxin‐neutralizing activity (TNA). However, the TNA of the V1C7_G29R mutant was not correspondingly improved, indicating that in the V1C7 family binding affinity alone does not account for differences in antibody function. V1C7 and V5C1, as well as their respective point mutants, recognized indistinguishable epitopes on RTA, at least at the level of sensitivity afforded by hydrogen‐deuterium mass spectrometry. The results of this study have implications for engineering therapeutic antibodies because they demonstrate that even subtle differences in epitope specificity can account for important differences in antibody function.     

Frugivory by Small Vertebrates Within a Deforested, Dry Tropical Region of Central America

Small vertebrates were inventoried within three habitat types in a degraded dry forest region of Panama. Animals were classified as frugivorous if they were observed foraging on fruit or if fecal samples contained mostly or exclusively seeds. Overall, we found that eight bat species and 21 bird species consumed fruit. The greatest numbers of birds were observed within live fences and bird species richness was greatest within riparian forests. Bat assemblages were not significantly different between habitats. The implication is that ecosystem services such as seed dispersal may still be functional in this landscape.     

Proteomics in immunity and herpes simplex encephalitis

The genetic theory of infectious diseases has proposed that susceptibility to life-threatening infectious diseases in childhood, occurring in the course of primary infection, results mostly from individually rare but collectively diverse single-gene variants. Recent evidence of an ever-expanding spectrum of genes involved in susceptibility to infectious disease indicates that the paradigm has important implications for diagnosis and treatment. One such pathology is childhood herpes simplex encephalitis, which shows a pattern of rare but diverse disease-disposing genetic variants. The present report shows how proteomics can help to understand susceptibility to childhood herpes simplex encephalitis and other viral infections, suggests that proteomics may have a particularly important role to play, emphasizes that variation over the population is a critical issue for proteomics and notes some new challenges for proteomics and related bioinformatics tools in the context of rare but diverse genetic defects.