We have sequenced the genome of Shigella-exneri serotype 2a, the most prevalent species and serotype that causes bacillary dysentery or shigellosis in man. The whole genome is composed of a 4 607 203 bp chromosome and a 221 618 bp virulence plasmid, designated pCP301. While the plasmid shows minor divergence from that sequenced in serotype 5a, striking characteristics of the chromosome have been revealed. The S-exneri chromosome has, astonishingly, 314 IS elements, more than 7-fold over those possessed by its close relatives, the non-pathogenic K12 strain and enterohemorrhagic O157:H7 strain of Escherichia coli. There are 13 translocations and inversions compared with the E.coli sequences, all involve a segment larger than 5 kb, and most are associated with deletions or acquired DNA sequences, of which several are likely to be bacteriophage-transmitted pathogenicity islands. Furthermore, S-exneri, resembling another human-restricted enteric pathogen, Salmonella typhi, also has hundreds of pseudogenes compared with the E.coli strains. All of these could be subjected to investigations towards novel preventative and treatment strategies against shigellosis.

Staphylococcus epidermidis strains are diverse in their pathogenicity; some are invasive and cause seri-ous nosocomial infections, whereas others are non-pathogenic commensal organisms, To analyse the implications of different virulence factors in Staphylo-coccus epidermidis infections, the complete genome of Staphylococcus epidermidis strain ATCC 12228, a non-biofilm forming, non-infection associated strain used for detection of residual antibiotics in food prod-ucts, was sequenced, This strain showed low viru-lence by mouse and rat experimental infections, The genome consists of a single 2499 279 bp chromosome and six plasmids. The chromosomal G+C content is 32.1% and 2419 protein coding sequences (CDS) are predicted, among which 230 are putative novel genes. Compared to the virulence factors in Staphylococcus aureus, aside from δ-haemolysin and 13-haemolysin, other toxin genes were not found. In contrast, the majority of adbesin genes are intact in ATCC 12228. Most strikingly, the ica operon coding for the enzymes synthesizing interbacterial cellular polysaccharide is missing in ATCC 12228 and rearrangements of adja-cent genes are shown. No mec genes, IS256, IS257, were found in ATCC 12228. It is suggested that the absence of the ica operon is a genetic marker in com-mensal Staphylococcus epidermidis strains which are less likely to become invasive.

目的 研究中药复方ZL-1在鸭己型肝炎病毒（DHBV）持续性感染模型中抗嗜肝DNA病毒的作用。方法 应用中药复方ZL-1治疗实验感染鸭，口服给药，剂量500mg•kg-1•d-1，分2次服用，连续4周。采用斑点分子杂交和southem印迹杂交检测治疗后感染鸭血清和肝脏中病毒的动态变化。同时以拉米夫定及安慰剂作为对照组。结果 复方药物ZL-l治疗后血清中DHBvDNA均数从3.6×1010拷贝/ml下降至0.9×1010拷贝/ml（P<001），抑制病毒率为75%，但尚不能清除病毒血症，肝组织中总DHBvDNA和DHmv超螺旋型DNA量无明显减少，停药观察2周，病毒复制反弹不明显。拉米夫定治疗后可显著降低病毒血症（P<0.01），抑制病毒率达99%，同时肝组织中总DHBVDNA和DHBV超螺旋型DNA量减少，但停药观察2周，病毒复制反弹明显。安慰剂组（口服生理盐水）治疗前后病毒水平的差异无显著性（P>0.05）。结论 复方药物ZL-1治疗4周可使感染鸭病毒血症降低。但不能清除病毒血症，肝脏中病毒复制水平也无显著下降。

目的 利用DHBV感染鸭模型，研究鸭IFN-γ真核表达质粒作为免疫佐剂对DNA疫苗诱导免疫应答的影响和预防DHBV感染的作用。方法 用DuIFN-γ真核表达质粒与DHBpreS/SDNA疫苗共免疫，或用DHBpreS/SDNA疫苗单独免疫正常幼鸭，检测经免疫前后鸭PBMC表达DuIFN-γ的mRNA水平（半定量竞争性RT-PCR）、诱生的抗体水平（ELISA）、病毒攻击免疫鸭后血清和肝脏中的病毒DNA变化（斑点和Southern印迹核酸杂交）。结果 IFN-γ表达质粒作为免疫佐剂，可以增强DNA疫苗诱导的鸭PBMCIFN-γ的mRNA表达水平。用大剂量病毒攻击免疫鸭的结果显示，用DuIFN-γ表达质粒和DHBpreS/SDNA疫苗共免疫鸭清除DHBV的速度，明显比仅用DHBpreS/SDNA疫苗免疫鸭清除病毒的速度快，肝脏中DHBV总DNA和共价闭环DNA（cccDNA）的量也低于DHBpreS/SDNA单独免疫组。结论 IFN-γ真核表达质粒作为免疫调节佐剂在DNA免疫中具有潜在的应用价值。

目的 构建汉坦病毒浙37（Z37）株包膜糖蛋白基因G1、G2真核表达质粒，并在真核细胞中表达。方法 根据Z37M基因序列设计6条引物，分别以质粒pGEMZ37、pCUMZ37为模板，通过聚合酶链反应（PCR）获得G1及G2片段。将G1、G2片段经BamHⅠ、XhoⅠ双酶切后插入至真核表达载体pcDNA3.1（+），经酶切鉴定，并测序证实。以磷酸钙沉淀法分别将重组质粒转染COS27细胞，用间接免疫荧光法（IFA）检测瞬时表达的蛋白。结果 获得分别含有编码汉坦病毒（HV）Z37株包膜糖蛋白G1、G2基因的重组质粒pcDNA3.12G1、pcDNA3.12G2；在转染的COS27细胞内，用IFA可检测到细胞内有特异性荧光。结论 成功地构建了HVZ37株包膜糖蛋白G1、G2基因真核表达载体，并可在COS27细胞中瞬时表达。