Human eosinophil peroxidase induces surface alteration, killing, and lysis of Mycobacterium tuberculosis

The antimycobacterial role of eosinophil peroxidase (EPO), one of the most abundant granule proteins in human eosinophils, was investigated. Our data indicate that purified EPO shows significant inhibitory activity towards Mycobacterium tuberculosis H37Rv. On a molar basis, this activity was similar to that exhibited by neutrophil myeloperoxidase (MPO) and was both dose and time dependent. In contrast to the activity of MPO, which requires H2O2, EPO also exhibited anti-M. tuberculosis activity in the absence of exogenously added peroxide. Morphological evidence confirmed that the mechanism of action of EPO against mycobacteria differs from that of MPO. While MPO kills M. tuberculosis H37Rv exclusively in the presence of hydrogen peroxide, it does not induce morphological changes in the pathogen. In contrast, EPO-treated bacteria frequently had cell wall lesions and eventually underwent lysis, either in the presence or in the absence of H2O2.