The stable incidence of new leprosy cases suggests that transmission of infection continues despite worldwide implementation of MDT. Thus, specific tools are needed to diagnose early stageMycobacterium lepraeinfection, the likely sources of transmission.M. lepraeantigens that induce T-cell responses inM. lepraeexposed and/or infected individuals thus are major targets for new diagnostic tools. Previously, we showed that ML1601c was immunogenic in patients and healthy household contacts (HHC). However, some endemic controls (EC) also recognized this protein. To improve the diagnostic potential, IFN-γresponses to ML1601c peptides were assessed using PBMC from Brazilian leprosy patients and EC. Five ML1601c peptides only induced IFN-γin patients and HHC. Moreover, 24-hour whole-blood assay (WBA), two ML1601c peptides could assess the level ofM. lepraeexposure in Ethiopian EC. Beside IFN-γ, also IP-10, IL-6, IL-1β, TNF-α, and MCP-1 were increased in EC from areas with high leprosy prevalence in response to these ML1601c peptides. Thus, ML1601c peptides may be useful for differentiatingM. lepraeexposed or infected individuals and can also be used to indicate the magnitude ofM. lepraetransmission even in the context of various HLA alleles as present in these different genetic backgrounds.
Host immune responses induced by specific Mycobacterium leprae antigens in an overnight whole-blood assay correlate with the diagnosis of paucibacillary leprosy patients in China
