梅毒螺旋体TpN17与TpN47表位肽融合抗原的重组表达及其酶联免疫吸附试验建立和应用

Recombinant expression of the fusion antigen based on Treponema pallidum TpN17 and TpN47 epitope peptides and establishment and application of the associated ELISA

摘要:

以重组TpNs为抗原的ELISAs已被证明是具有较高敏感性和特异性的梅毒血清学检测方法, 若在ELISAs使用多种TpNs抗原, 可进一步提高检测敏感性和特异性。根据抗原表位分析结果, 本研究首先采用连接引物PCR获得了TpN17和TpN47抗原表位序列融合成的人工基因片段tpE17-47, 然后构建了全长tpN17、tpN47基因以及tpE17-47融合基因的原核表达系统。SDS-PAGE和BioRad凝胶图象分析系统检查结果显示, 所构建的原核表达系统能稳定表达目的重组蛋白rTpN17、rTpN47和rTpE17-47, 其产量分别约占细菌总蛋白的36%、20%和28%。采用Ni-NTA亲和层析法提纯的rTpN17、rTpN47和rTpE17-47蛋白经SDS-PAGE分析, 均显示为单一的蛋白条带。Western blotting结果表明, rTpN17、rTpN47和rTpE17-47蛋白均可被梅毒抗体阳性的病人血清所识别。以rTpE17-47为包被抗原的rTpE17-47-ELISA检测630例临床确诊梅毒患者血清标本的阳性率为98.6%, 仅略高于TPPA(97.9%)(P>0.05), 但明显高于rTpN17-ELISA(83.8%)、rTpN47-ELISA(83.3%)和RPR(72.1%)(P<0.01)。上述ELISAs和TPPA对25例SLE、36例RA患者和250例健康体检者的血清标本检测结果均为阴性, 但RPR分别有1、2和2例标本检测结果为阳性。本试验成功地构建了rTpE17-47抗原表位融合基因及其高效原核表达系统, 所建立的rTpE17-47-ELISA可作为一种快速、简便、安全、敏感和特异的梅毒血清学筛查或诊断新方法。

Abstract:

Using recombinant TpNs proteins of Treponema pallidum as antigens, ELISAs are proved to be of higher sensitivity and specificity. However, they can be further increased by using multiple TpNs antigens. According to the epitope analysis, we firstly used linking primers PCRs to obtain an artificial fusion gene segment tpE17-47 containing epitopes of both TpN17 and TpN47. Subsequently, we conducted the prokaryotic expression systems of entire tpN17 and tpN47 genes and tpE17-47 fusion gene. SDS-PAGE analysis and BioRad Gel Image Analysis System showed that the recombinant proteins rTpN17, rTpN47 and rTpE17-47 expressed stably, with 36%, 20% and 28% yields of total bacterial protein, respectively. After purified by Ni-NTA affinity chromatography, all the three recombinant proteins could be recognized by T. pallidum antibody positive sera from syphilis patients. The positive rate of rTpE17-47-ELISA for detecting serum specimens in clinically 630 cases with syphilis was 98.6%. This rate was slightly higher than that by Treponema pallidum particle agglutination (TPPA) (97.9%) (P>0.05), but significantly higher than those by rTpN17-ELISA (83.8%), rTpN47-ELISA (83.3%) and rapid plasma reagin (RPR)(72.1%)(P<0.01). Furthermore, both ELISAs and TPPA for detecting the serum specimens in 25 cases with SLE, 36 cases with RA and 250 healthy cases were all negative. RPR showed positive in 1 case with SLE, 2 cases with RA and 2 healthy cases. This could be a novel serological screening or diagnostic method of syphilis with advantages of quickness, convenience, safety, sensitivity and specificity.