Blanton R E, Licate L S, Aman R A
Department of Medicine, Case Western Reserve University, Cleveland, OH 44106-4983.
Mol Biochem Parasitol. 1994 Jan;63(1):1-11. doi: 10.1016/0166-6851(94)90003-5.
Immunologic screening of a Schistosoma haematobium cDNA library with species-specific human antisera identified a clone whose predicted amino acid sequence encodes a member of the serine protease inhibitor (serpin) gene family. This cDNA consists of 1397 bp with a single open reading frame that can encode a 409-amino acid protein of 46,261 Da. The native antigen is a 54-58-kDa glycoprotein and is located on the surface of adult worms. Sequence comparison with other serpins predicts the amino acid Phe at the putative reactive center of the protein. Phenylalanine is also found at the corresponding site of a vaccinia serpin that may contribute to the hemorrhagic phenotype of some strains of cowpox virus. Though the human parasites S. haematobium and Schistosoma mansoni demonstrate a close antigenic relationship, the S. haematobium serpin gene product demonstrates marked species-specific immunogenicity. By Northern blot hybridization, however, both species express a 1700-nucleotide mRNA that hybridizes with the S. haematobium serpin cDNA. The intensity of cross hybridization for the S. mansoni mRNA is 10-fold lower than that for S. haematobium. Southern blots of genomic DNA and gene titration experiments indicate that the S. haematobium gene is present in approximately 4-5 copies per haploid genome.
用种属特异性人抗血清对埃及血吸虫cDNA文库进行免疫筛选，鉴定出一个克隆，其预测的氨基酸序列编码丝氨酸蛋白酶抑制剂（serpin）基因家族的一个成员。该cDNA由1397个碱基对组成，有一个单一的开放阅读框，可编码一个46,261 Da的409个氨基酸的蛋白质。天然抗原是一种54 - 58 kDa的糖蛋白，位于成虫表面。与其他serpin的序列比较预测该蛋白假定反应中心的氨基酸为苯丙氨酸。在痘苗病毒serpin的相应位点也发现了苯丙氨酸，这可能与某些牛痘病毒株的出血表型有关。虽然人体寄生虫埃及血吸虫和曼氏血吸虫表现出密切的抗原关系，但埃及血吸虫serpin基因产物表现出明显的种属特异性免疫原性。然而，通过Northern印迹杂交，这两个种都表达一种1700个核苷酸的mRNA，它与埃及血吸虫serpin cDNA杂交。曼氏血吸虫mRNA的交叉杂交强度比埃及血吸虫低10倍。基因组DNA的Southern印迹和基因滴定实验表明，埃及血吸虫基因在每个单倍体基因组中约有4 - 5个拷贝。
