Yxfeldt G, Fröman G, Mårdh P A, Ward M E
Institute of Clinical Bacteriology, Uppsala University, Sweden.
Microbiology (Reading). 1994 Apr;140 ( Pt 4):815-21. doi: 10.1099/00221287-140-4-815.
One problem of peptide vaccines is that antibodies generated against them react poorly with the target sequence on the native protein. Using monoclonal antibodies (mAbs) to the serovar L1 type-specific epitope on the major outer-membrane protein of Chlamydia trachomatis as our model in conjunction with the Pin Technology Epitope Scanning technique, we had previously identified the critical binding site at this epitope as DAVP. Amino acid substitution showed that AV were essential residues for binding. A series of structurally related (heteroclitic) peptides retaining AV were synthesized. Some of these were found to be much more reactive with the model mAb than peptides of cognate sequence. It was hypothesized that the DAVP peptide only approximated to the conformation of the homologous sequence in the native protein, whereas some of the flexible heteroclitic peptides produced conformations which more closely resembled the native constrained sequence. The key question was whether the most reactive heteroclitic peptide would also generate antibody capable of more efficient binding to the native protein. We therefore immunized mice with one of six heteroclitic peptides or one of two native sequence control peptides. The reactivity of these antisera with the peptide immunogens and with native chlamydial elementary bodies was then evaluated by enzyme immunoassay. Pooled antisera to two of the heteroclitic peptides reacted with significantly greater absorbance (P < 0.05) and at higher dilution with whole chlamydiae than did pooled antisera to the control peptides. This suggests that heteroclitic peptides may in some circumstances be useful to increase the reactivity of site-specific antibodies with epitopes on the native protein important for vaccine development or for serodiagnosis.
肽疫苗的一个问题是，针对它们产生的抗体与天然蛋白质上的靶序列反应不佳。我们以针对沙眼衣原体主要外膜蛋白上血清型L1型特异性表位的单克隆抗体（mAb）作为模型，并结合Pin技术表位扫描技术，之前已确定该表位的关键结合位点为DAVP。氨基酸取代表明AV是结合的必需残基。合成了一系列保留AV的结构相关（异向性）肽。发现其中一些肽与模型单克隆抗体的反应性比同源序列的肽高得多。据推测，DAVP肽仅近似于天然蛋白质中同源序列的构象，而一些柔性异向性肽产生的构象更类似于天然受限序列。关键问题是，反应性最高的异向性肽是否也能产生能够更有效地结合天然蛋白质的抗体。因此，我们用六种异向性肽之一或两种天然序列对照肽之一免疫小鼠。然后通过酶免疫测定评估这些抗血清与肽免疫原和天然衣原体原体的反应性。与对照肽的混合抗血清相比，针对两种异向性肽的混合抗血清与全衣原体反应时，吸光度显著更高（P < 0.05）且稀释度更高。这表明在某些情况下，异向性肽可能有助于提高位点特异性抗体与对疫苗开发或血清诊断重要的天然蛋白质上的表位的反应性。
