The nature of immunodominant antigens of periodontopathic bacteria

本研究的目的是确定牙龈卟啉单胞菌381的免疫优势抗原，并检测其组成和分子量。选择了14名对牙龈卟啉单胞菌381超声提取物具有高抗体滴度的牙周患者。将牙龈卟啉单胞菌381的全细胞、超声处理的提取物和外膜蛋白以未处理和加热的形式用作抗原。总糖，蛋白质和脂多糖估计在每一个的三种抗原。通过酶联免疫吸附试验（ELISA），在热处理之前和之后评价抗体与三种抗原的结合。此外，进行免疫印迹分析。定量分析表明，整个细胞含有约10倍的脂多糖，而外膜蛋白含有两倍的碳水化合物。根据热处理下抗体结合的降低率将14份血清分为三组。关于超声处理的提取物，在14份血清中的11份中，在热处理下抗体结合显示出高度降低（77.5-92.3%）。然而，在三份血清中，热处理几乎不降低与外膜蛋白抗原的抗体结合（14.9-30.9%）。此外，这三种血清对全细胞抗原显示出几乎相同的应答（减少15.2-24.9%）。本研究表明，牙龈卟啉单胞菌的免疫优势抗原似乎主要由蛋白质组成，分子量为57，44，42和39 kDa。此外，从全细胞和外膜蛋白的结果表明，非蛋白质物质可能有助于作为抗原的抗体结合。

The present study had the purpose to determine the immunodominant antigens of P. gingivalis 381 and to examine their composition and molecular weight. Fourteen periodontal patients, with high antibody titers to P. gingivalis 381 sonicated extract, were selected. Whole cell, sonicated extract and outer membrane protein of P. gingivalis 381 were used as antigen in untreated and heated form. Total sugar, protein and lipopolysaccharide were estimated in each one of the three antigens. Antibody binding to the three antigens was evaluated, before and after heat treatment, by an enzyme-linked immunosorbent assay (ELISA). In addition, the immunoblotting analysis was performed. The quantitative assays showed that the whole cell contained about ten times more lipopolysaccharide while the outer membrane protein contained twice the amount of carbohydrates. The 14 sera were classified into three groups according to the rate of reduction of antibody binding under heat treatment. Concerning the sonicated extract, the antibody binding showed high reduction (77.5-92.3%) under heat treatment in 11 out of 14 sera. However, antibody binding to the outer membrane protein antigen was hardly decreased by heat treatment in three sera (14.9-30.9%). Also, these three sera showed almost the same response to the whole cell antigen (reduction 15.2-24.9%). The present study indicates that the immunodominant antigens of P. gingivalis seemed to be composed mainly of protein and appeared to be at molecular weights of 57, 44, 42 and 39 kDa. Furthermore, a possibility that non-proteinic substances, may contribute to the antibody binding as an antigen is indicated from the results of the whole cell and the outer membrane protein.