OBJECTIVETo screen the specific antibody binding peptides of tuberculosis from phage-displayed random phage display (Ph.D.)-7 peptide libraries with purified IgG from tuberculosis serum, and to provide the basis for the development of serological detection reagent of tuberculosis.

METHODSPurified IgG of tuberculosis serum was used as solid ligand to screen the binding peptide from the Ph.D.-7 peptide library, according to the biopanning process of absorption, elution and amplification. Purified IgG of health people serum was used as the molecule of counter selection during the second and third selection. Phages were enriched after 3 rounds of screening, then 20 single phages separately eluted by IgG of tuberculosis and health people were randomly selected on each direction of the determination plates and amplified. The single chains DNA were extracted as template for sequencing. The combination abilities of selected clones to IgG of tuberculosis and health people were tested by indirect enzyme linked immunosorbent assay (ELISA), and the positive clone was identified. Serum samples, from 47 patients with tuberculosis and 37 healthy people vaccinated with BCG, were verified by positive phage clones using phage-ELISA. The verifying results of 24 serum samples used for panning were separately analyzed statistically.

RESULTSAfter 3 rounds of panning, remarkable enrichment of phages that could specifically bind with target molecules were observed. Single phages were randomly selected for sequencing analysis and 12 sequences were obtained. 12 phage clones with different sequences were amplified and detected with indirect ELISA and single phage H12 showed higher affinity with IgG of tuberculosis (S/N ≥ 2.1) and was identified as the positive clone. It was found that, in indirect ELISA with single Phage H12, the A(450) value of tuberculosis patients (0.105 ± 0.010) was significantly higher than that of healthy individuals (0.070 ± 0.005), and the t value was 2.912 (P < 0.0001). The A(450) value of 12 serum samples of tuberculosis patients and 12 samples of health individuals used for panning were 0.144 ± 0.016 and 0.052 ± 0.004, and the t value was 5.69 (P < 0.0001).

CONCLUSIONBy using phage-displayed random peptide libraries, we obtained the specific antibody binding peptides of tuberculosis, which showed specific binding activity with IgG of tuberculosis. It can provide a basis for the establishment of a new serological detection method of tuberculosis with peptide.