Duranti M A, Franzoni L, Sartor G, Benedetti A, Iwai L K, Gruber A, Zingales B, Guzman F, Kalil J, Spisni A, Cunha-Neto E
Laboratory of Transplantation Immunology, Heart Institute, Faculty of Medicine, University of São Paulo, SP, Brazil.
Exp Parasitol. 1999 Sep;93(1):38-44. doi: 10.1006/expr.1999.4428.
The Trypanosoma cruzi recombinant protein B13 contains tandemly repeated domains and shows high sensitivity in the serological diagnosis of Chagas' disease. It has been shown that the immunodominant epitope of B13 is contained in the GDKPSLFGQAAAGDKPSLF-NH(2) sequence and that the hexapeptide AAAGDK seems to be the "core" of that epitope. Three peptides containing that "core" sequence, one corresponding to the entire repeat motif GDKPSLFGQAAAGDKPSLF-NH(2), pB13, and two smaller fragments, FGQAAAGDK-NH(2), S4, and QAAAGDKPS-NH(2), S5, have been tested in competitive ELISA with recombinant protein B13 in the solid phase against 40 chagasic sera from Brazilian patients. The median percentage inhibition for pB13, S4, and S5 were, respectively, 91, 86, and 68%. The possibility that the distinct antigenic activity of those peptides correlates with the existence of preferential conformational properties has been investigated by CD and NMR spectroscopy. Results indicate their propensity to adopt a helical configuration, centered in the AAAGDK sequence, and whose extent and stability directly correlates with the peptides' antigenicity. The data are discussed in the light of the existence of conformational preferences involving immunodominant epitopes in tandemly repeated antigens.
克氏锥虫重组蛋白B13含有串联重复结构域，在恰加斯病的血清学诊断中表现出高敏感性。研究表明，B13的免疫显性表位包含在GDKPSLFGQAAAGDKPSLF-NH(2)序列中，六肽AAAGDK似乎是该表位的“核心”。含有该“核心”序列的三种肽，一种对应于整个重复基序GDKPSLFGQAAAGDKPSLF-NH(2)，即pB13，另外两种较小的片段，FGQAAAGDK-NH(2)，即S4，以及QAAAGDKPS-NH(2)，即S5，已在竞争性ELISA中用固相重组蛋白B13针对40份来自巴西患者的恰加斯病血清进行了测试。pB13、S4和S5的中位抑制百分比分别为91%、86%和68%。通过圆二色光谱和核磁共振光谱研究了这些肽不同的抗原活性与优先构象特性的存在之间的相关性。结果表明它们倾向于采用以AAAGDK序列为中心的螺旋构象，其程度和稳定性与肽的抗原性直接相关。结合串联重复抗原中涉及免疫显性表位的构象偏好的存在对这些数据进行了讨论。
