AIM:Panton-Valentine leukocidin(PVL)is a pore-forming toxin secreted by Staphylococcus aureus epidemiologieally associated with the often-lethal necrotizing pneumonia.Until now,the mechanisms of pathogene-sis of PVL leading to the fatal pulmonia remains undefined and also acquired plenty of the toxins is difficult.In the present study，we obtain recombinant staphylococcal F and S components of the Panton-Valentine leukocidin by gene engineering and evaluate its biological activity in vitro,which provides an experimental basis for the further studies of its biological func-tion and its toxicity in pneumonia.METHODS:The full-length of F and S components of PVL gene amplified from the strain of Staphylococcus aureus DNA by hiSh-fidelity PCR was cloned into prokaryotic expression vector pET22b(+),and the vector was transformed into BL21(DE3)plysS to construct a prokaryotie expression system.The integrity of the opening-reading frame of each construct was verified by DNA sequencing.The recombinant PVL(rPVL)was induced by1.0 mmol/L IPTG.The expressed products were identified by SDS-PAGE and the fusion proteins(6His-LukS-PV and 6His-LukF-PV)were purified from lysates of transfeeted E.coli cells by affinity chromatography on nitrilotriacetic acid columns.The eytolytie activity was tested by incubation of rPVL with human polymorphonuclear neutrophils(PMNs)in vitro.RESULTS:The nueleotide sequence of the cloned PVL gene was the same as that of reported in GenBank.E coli BL21(DE3)plysS containing recombinant vectors grow at 37℃causes some proteins to accumulate as inclusion bodies.while incubation at 30℃led to a significant amount of soluble active proteins which accounted for about 31.7％ of the total bacterial protein.The relative molecular weight showed on SDS-PAGE profile was consistent with the expected value which the LukS-PV protein was about 34 kD.and the LukF-PV protein was about 35 kD.The purified rPVL was obtained and its cytolytic activity to PMNs was demonstrated.CONCLUSION:The genes of 1ukS-PV and lukF-PV are successfully cloned into plasmid pET22b(+)and expressed in E coli respectively.which provide a basis for analyzing the toxicity related to the diseases and further studies about the pathogenesis of PVL.%目的:通过基因工程方法获得重组的杀白细胞毒素,为深入研究其致病机制打下基础.方法:利用PCR方法从产杀白细胞毒素金葡菌临床分离株的基因组DNA中克隆PVL-s和PVL-F基因序列,分别将其克隆到载体pET22b中,构建重组pET22b-hlKS和pET22b-hKF原核表达载体,转化感受态大肠杆菌BL21(DE3)pLysS,异丙基硫代13一D半乳糖苷(sopropyl-beta-D-thiogalactopyranoside,IFFG)诱导表达,将其可溶性表达经镍离子螯合亲和层析纯化后,通过对外周血粒细胞和多形核白细胞的刺激反应鉴定其活性.结果:以PCR方法获得PVL-S和PVL-F基因片段,与克隆载体连接后测序与文献报道的基本一致,成功构建了pET22b-LuKS和pET22b-LuKF原核表达质粒,并高效诱导表达出相对分子质量约34 kD的s蛋白及相对分子质量约35 kD的F蛋白.重组蛋白(rPVS,rPVF)在37℃经IPTG诱导时均以包涵体形式存在,而30℃时部分出现可溶性表达,部分为包涵体.将上清可溶性重组蛋白作用于外周血粒细胞,可导致粒细胞出现凋亡,部分出现坏死.结论:成功构建了表达载体pET22b-LuKS和pET22b-LuKF,对其编码的S片段和F片段进行了原核表达和鉴定,高效表达了杀白细胞毒素的S和F两类蛋白,为进一步对其致病机制和免疫原性的研究奠定基础.
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