Although serological detection is a practical strategy for early detection and diagnosis of tuberculosis (TB), inconsistent and imprecise estimates of sensitivity and specificity block its development and application for clinic. New or alternative serological antigens with improved accuracy are urgently needed. A phage-displayed random peptide library was employed to screen for immunoactive peptides using specific immunoglobulin G (IgG) of TB patients as target molecules. With two screening strategies, 20 single phages displaying different sequences were obtained and no sequence homology was found among these phages. From the results of phage-ELISA, H12, TB6, TB15, and TB18 phages showed higher affinity to IgGs from TB patients(S/N ≥2.1) and were identified as the positive clones. Significant differences in the detection values of sera from 47 TB patients and 37 healthy individuals were found for these four phage clones. According to the reactivity of 284 human sera to synthetic H12, TB6, TB15, and TB18 peptides as determined by ELISA, TB15 showed significantly higher areas under the curve (AUC) and sensitivity than other peptides, providing a lead molecule for the development of new serology diagnostic strategies for TB.

A fluorobody is a manmade hybrid molecule that is composed of green fluorescent protein (GFP) and a fragment of antibody, which combines the affinity and specificity of an antibody with the visibility of a GFP. It is able to provide a real-time indication of binding while avoiding the use of tags and secondary binding reagents. Here, the expression, purification and crystal structure of a recombinant fluorobody for TLH (thermolabile haemolysin), a toxin from the lethal food-borne disease bacterium Vibrio parahaemolyticus, are presented. This is the first structure of a fluorobody to be reported. Crystals belonging to space group P4 3 2 1 2, with unit-cell parameters a = b = 63.35, c = 125.90 Å , were obtained by vapour diffusion in hanging drops and the structure was refined to an R free of 16.7% at 1.5 Å resolution. The structure shows a CDR loop of the antibody on the GFP scaffold.