Iron Storage Proteins Are Essential for the Survival and Pathogenesis of Mycobacterium tuberculosis in THP-1 Macrophages and the Guinea Pig Model of Infection

Abstract

<jats:title>ABSTRACT</jats:title> <jats:p> Iron is one of the crucial elements required for the growth of <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Mycobacterium tuberculosis</jats:named-content> . However, excess free iron becomes toxic for the cells because it catalyzes the production of reactive oxygen radicals, leading to oxidative damage. Hence, it is essential for the pathogen to have the ability to store intracellular iron in an iron-rich environment and utilize it under iron depletion. <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">M. tuberculosis</jats:named-content> has two iron storage proteins, namely BfrA (Rv1876; a bacterioferritin) and BfrB (Rv3841; a ferritin-like protein). However, the demonstration of biological significance requires the disruption of relevant genes and the evaluation of the resulting mutant for its ability to survive in the host and cause disease. In this study, we have disrupted <jats:italic>bfrA</jats:italic> and <jats:italic>bfrB</jats:italic> of <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">M. tuberculosis</jats:named-content> and demonstrated that these genes are crucial for the storage and supply of iron for the growth of bacteria and to withstand oxidative stress <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">in vitro</jats:named-content> . In addition, the <jats:italic>bfrA bfrB</jats:italic> double mutant (H37Rv Δ <jats:italic>bfrA</jats:italic> Δ <jats:italic>bfrB</jats:italic> ) exhibited a marked reduction in its ability to survive inside human macrophages. Guinea pigs infected with H37Rv Δ <jats:italic>bfrA</jats:italic> Δ <jats:italic>bfrB</jats:italic> exhibited a marked diminution in the dissemination of the bacilli to spleen compared to that of the parental strain. Moreover, guinea pigs infected with H37Rv Δ <jats:italic>bfrA</jats:italic> Δ <jats:italic>bfrB</jats:italic> exhibited significantly reduced pathological damage in spleen and lungs compared to that of animals infected with the parental strain. Our study clearly demonstrates the importance of these iron storage proteins in the survival and pathogenesis of <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">M. tuberculosis</jats:named-content> in the host and establishes them as attractive targets for the development of new inhibitors against mycobacterial infections. </jats:p>