Functional expression of single-chain antibody to leukotriene C4

Leukotriene C4 (LTC4) is synthesized by binding of glutathione to LTA4, an epoxide derived from arachidonic acid, and further metabolized to LTD4 and LTE4. We previously prepared a monoclonal antibody with a high affinity and specificity to LTC4. To explore the structure of the antigen-binding site of a monoclonal antibody against LTC4 (mAbLTC), we isolated full-length cDNAs for heavy and light chains of mAbLTC. The heavy and light chains consisted of 461 and 238 amino acids including a signal peptide with molecular weights of 51,089 and 26,340, respectively. An expression plasmid encoding a single-chain antibody comprising variable regions of mAbLTC heavy and light chains (scFvLTC) was constructed and expressed in COS-7 cells. The recombinant scFvLTC showed a high affinity with LTC4 comparable to mAbLTC. The scFvLTC also bound to LTD4 and LTE4 with 48% and 17% reactivities, respectively, as compared with LTC4 binding, whereas the antibody showed almost no affinity for LTB4.