Aim: To construct the gene of murine single-chain Fv fragment (scFv) against human cervical cancer and to predict the physical and chemical characteristics, secondary structure, tertiary structure and the molecular evolution of the scFv using computer-assisted modeling.
Methods: The variable region gene of the heavy and light chains were amplified respectively using recombinant DNA techniques from CSA125 hybridoma cells that can secret monoclonal antibodies with high activity and specificity against human cervical cancer. These two fragments were then spliced together through a flexible linker to scFv against human cervical cancer by using splicing overlap extension (SOE) PCR. The scFv gene, named CSAs-1, was cloned into the vector pMD18-T. The physical and chemical characteristics secondary and tertiary structure and the phylogenetic tree were predicted using Internet and corresponding softwares.
Results: The whole scFv gene was cloned successfully and encoded 278 amino acids. Theoretically, the CSAs-1 scFv was relative molecular masses 28,800, the isoelectric point (pI) was 7.215. PHDsec indicated that CSAs-1 was alpha+beta globin. There were many protein kinase C phosphorylation sites and casein kinase II phosphorylation sites in the V(H) and V(L) domains. The computer graphic modeling indicated the linker was isolated from V(H) and V(L). The V(L), as well as the V(H), was involved in composing the hydrophobic "pocket" which was beneficial to the antigen binding. Phylogenetic tree analysis indicated that V(H) genes from various vertebrate species formed three clusters that corresponded to three V(H) groups and that V(L) sequences from each species had a level of diversity similar to that of their V(H) genes. CSAs-1 V regions belong to A group.
Conclusion: The construction and analysis of a molecular model of scFv laid the foundation for the further research into genetic engineering antibody and the mechanism of antigen-antibody interaction.