RESUMEN
Immunoassays are practical and cost-effective approaches suitable for large-scale tuberculosis (TB) screening. This study identified new peptide mimotopes of Mycobacterium tuberculosis and applied them in the serodiagnosis of TB. Thereby, linear (X15, X8CX8) and constrained (LX-4 and LX-8) phage display peptide libraries were screened with purified Immunoglobulin G antibodies from TB-positive patients, and eight mimotopes were selected. The mimotope peptides were screened using the SPOT-synthesis technique followed by immunoblotting. Peptides P.Mt.PD.4 and P.Mt.PD.7 demonstrated the highest binding affinity and were chemically synthesized and used as antigens for enzyme-linked immunosorbent assay (ELISA) assays. Experimental designs were used to optimize the assays and to assess each variable's influence. Peptide P.Mt.PD.7 was differentiated between positive and negative samples and achieved 100% sensitivity and specificity when tested on a 100-sera panel. Therefore, the selected peptide was applied to the ELISA assay as a screening method for diagnosing TB represents a potential tool for helping to combat the disease.
Asunto(s)
Bacteriófagos , Mycobacterium tuberculosis , Tuberculosis , Ensayo de Inmunoadsorción Enzimática/métodos , Humanos , Biblioteca de Péptidos , Péptidos , Proyectos de Investigación , Tuberculosis/diagnósticoRESUMEN
Abstract The rapid and accurate diagnosis of tuberculosis (TB), especially considering limited resources, is still a challenge. Development of new methodologies and tests are needed to overcome several disadvantages of the available standard tests. We evaluated the diagnostic potential of two antigens specific for Mycobacterium tuberculosis, the CFP10 and ESAT6 recombinant proteins, and developed stable formulations thereof. Sensitivity and specificity of the delayed-type hypersensitivity (DTH) skin testing and the induction of gamma interferon production (IFN-γ) by lymphocytes, as a non-invasive test, were evaluated using the CFP10 and ESAT6 protein formulations. The recombinant proteins produced by our group presented a high DTH response and the ability to differentiate between tuberculosis infection, BCG vaccination, and the contact with non-tuberculous mycobacteria (NTM). The production of IFN-γ by stimulation with individual and combined proteins was detected in a panel of 40 individuals and showed a specificity of 100% and a sensitivity of 90% when the two proteins were used together. Lyophilized formulations were stable under all conditions, while soluble formulations were stable under freezing at -20 ºC and -80 ºC. The proposed formulations containing the ESAT6 and CFP10 recombinant antigens constitute satisfactory tools for TB testing, suitable to be developed and implemented in a large-scale trial.