Attridge S R, Qadri F, Albert M J, Manning P A
Microbial Pathogenesis Unit, Department of Microbiology and Immunology, The University of Adelaide, South Australia 5005, Australia.
Clin Diagn Lab Immunol. 2000 May;7(3):444-50. doi: 10.1128/CDLI.7.3.444-450.2000.
Volunteer studies with Vibrio cholerae O1 have shown that the best correlate of a vaccine's protective efficacy is its propensity to elicit serum bactericidal responses in its recipients. Attempts to detect such responses following infection with V. cholerae O139, however, have met with varying success. Using a tube-based assay which involves viable counting, we now report that strains of serogroup O139 can appear to be sensitive or resistant to a fixed concentration of complement in the presence of antibody, depending on assay conditions. Susceptibility to lysis is critically dependent on the availability of complement, but with O139 indicator strains this is not simply determined by the concentration of serum added to the reaction mix. The nature of the assay diluent and the concentration of indicator bacteria can also dramatically affect bactericidal end points, whereas such variables have minimal significance with O1 indicator bacteria. Although some laboratories use unencapsulated mutant strains to seek evidence of seroconversion following exposure to V. cholerae O139, this is not necessary, and our findings question the significance of capsule expression as a determinant of complement sensitivity when antibody is present. The medium used for growth of the indicator strain and the particular strain used appeared to be unimportant. Each of seven O139 isolates tested was found to be lysed by antibody and complement in our standard assay system, which allowed the detection of significant serum bactericidal responses in 9 of 11 cases of O139 disease.
对霍乱弧菌O1的志愿者研究表明，疫苗保护效力的最佳相关指标是其在接种者中引发血清杀菌反应的倾向。然而，在感染霍乱弧菌O139后检测此类反应的尝试取得了不同程度的成功。我们现在报告，使用基于试管的活菌计数检测方法，在有抗体存在的情况下，O139血清群菌株对固定浓度的补体可能表现出敏感或抗性，这取决于检测条件。对裂解的敏感性关键取决于补体的可用性，但对于O139指示菌株，这不仅仅由添加到反应混合物中的血清浓度决定。检测稀释剂的性质和指示菌的浓度也会显著影响杀菌终点，而这些变量对O1指示菌的影响极小。尽管一些实验室使用非包膜突变株来寻找接触霍乱弧菌O139后血清转化的证据，但这并非必要，而且我们的研究结果对抗体存在时荚膜表达作为补体敏感性决定因素的重要性提出了质疑。用于指示菌生长的培养基和所使用的特定菌株似乎并不重要。在我们的标准检测系统中，所测试的7株O139分离株中的每一株都被抗体和补体裂解，这使得在11例O139疾病中有9例检测到显著的血清杀菌反应。
