Barbet A F, Myler P J, Williams R O, McGuire T C
Department of Veterinary Microbiology and Pathology, Washington State University, Pullman.
Mol Biochem Parasitol. 1989 Jan 15;32(2-3):191-9. doi: 10.1016/0166-6851(89)90070-4.
African trypanosomes evade the immune response of the mammalian host by undergoing antigenic variation, caused by sequence changes in a variable surface glycoprotein (VSG). The majority of trypanosome clones analyzed thus far are not known to share surface exposed epitopes or express appreciably homologous VSGs. We show here that four clones of Trypanosoma brucei from the same serodeme express different VSGs and share exposed epitopes to varying degrees, as defined by monoclonal antibodies. Rabbit antiserum against any one of the four VSGs recognizes epitopes present on all four trypanosomes in live cell immunofluorescence assay. The expressed VSGs are partially homologous at the N-terminus with multiple point substitutions of amino acids which distinguish each of the four VSGs. The genes coding for these VSGs are members of one gene family and an expression-linked copy with a unique restriction map is present in each trypanosome. Analysis of the ontogeny of the expressed genes should reveal mechanisms of evolution in trypanosome variable antigen repertoires.
非洲锥虫通过可变表面糖蛋白（VSG）的序列变化引起抗原变异，从而逃避哺乳动物宿主的免疫反应。到目前为止，大多数已分析的锥虫克隆并不共享表面暴露表位，也不表达明显同源的VSG。我们在此表明，来自同一血清型的四个布氏锥虫克隆表达不同的VSG，并在不同程度上共享暴露表位，这是由单克隆抗体定义的。针对这四种VSG中任何一种的兔抗血清在活细胞免疫荧光试验中识别所有四种锥虫上存在的表位。所表达的VSG在N端部分同源，具有多个区分这四种VSG的氨基酸点突变。编码这些VSG的基因是一个基因家族的成员，每个锥虫中都存在一个具有独特限制图谱的表达连锁拷贝。对所表达基因个体发生的分析应能揭示锥虫可变抗原库的进化机制。
