Use of synthetic peptides derived from the antigens ESAT-6 and CFP-10 for differential diagnosis of bovine tuberculosis in cattle

In Great Britain an independent scientific review for the government has co ncluded that the development of a cattle vaccine against Mycobacterium bovi s infection holds the best long-term prospect for tuberculosis control in B ritish herds, A precondition for vaccination is the development of a comple mentary diagnostic test to differentiate between vaccinated animals and tho se infected with M, bovis so that testing and slaughter-based control strat egies can continue alongside vaccination. To date bacillus Calmette-Guerin (BCG), an attenuated strain of M, bovis, is the only available vaccine for the prevention of tuberculosis. However, tests based on tuberculin purified protein derivative cannot distinguish between M. bovis infection and BCC v accination, Therefore, specific antigens expressed by M, bovis but absent f rom BCG constitute prime candidates for differential diagnostic reagents. R ecently, two such antigens, ESAT-6 and CFP-10, have been reported to be pro mising candidates as diagnostic reagents for the detection of M, bovis infe ction in cattle, Here we report the identification of promiscuous peptides of CFP-10 that were recognized by M, bovis-infected cattle. Five of these p eptides were formulated into a peptide cocktail together with five peptides derived from ESAT-6, Using this peptide cocktail in T-cell assays, M. bovi s-infected animals were detected, while BCG-vaccinated or Mycobacterium avi um-sensitized animals did not respond. The sensitivity of the peptide cockt ail as an antigen in a whole-blood gamma interferon assay was determined us ing naturally infected field reactor cattle, and the specificity was determ ined using blood from BCG-vaccinated and noninfected, nonvaccinated animals . The sensitivity of the assay in cattle with confirmed tuberculosis was fo und to be 77.9%, with a specificity of 100% in BCG-vaccinated or nonvaccina ted animals, This compares favorably with the specificity of tuberculin whe n tested in noninfected or vaccinated animals. In summary, our results demo nstrate that this peptide cocktail can discriminate between M, bovis infect ion and BCG vaccination with a high degree of sensitivity and specificity.