Interaction of Mycobacterium leprae with Human Airway Epithelial Cells: Adherence, Entry, Survival, and Identification of Potential Adhesins by Surface Proteome Analysis

Abstract

f This study examined the in vitro interaction between Mycobacterium leprae, the causative agent of leprosy, and human alveolar and nasal epithelial cells, demonstrating that M. leprae can enter both cell types and that both are capable of sustaining bacterial survival. Moreover, delivery of M. leprae to the nasal septum of mice resulted in macrophage and epithelial cell infection in the lung tissue, sustaining the idea that the airways constitute an important M. leprae entry route into the human body. Since critical aspects in understanding the mechanisms of infection are the identification and characterization of the adhesins involved in pathogen-host cell interaction, the nude mouse-derived M. leprae cell surface-exposed proteome was studied to uncover potentially relevant adhesin candidates. A total of 279 cell surface-exposed proteins were identified based on selective biotinylation, streptavidin-affinity purification, and shotgun mass spectrometry; 11 of those proteins have been previously described as potential adhesins. In vitro assays with the recombinant forms of the histone-like protein (Hlp) and the heparin-binding hemagglutinin (HBHA), considered to be major mycobacterial adhesins, confirmed their capacity to promote bacterial attachment to epithelial cells. Taking our data together, they suggest that the airway epithelium may act as a reservoir and/or portal of entry for M. leprae in humans. Moreover, our report sheds light on the potentially critical adhesins involved in M. leprae-epithelial cell interaction that may be useful in designing more effective tools for leprosy control.

A Novel DNA-Binding Protein Plays an Important Role in Helicobacter pylori Stress Tolerance and Survival in the Host

“…As HLPs have multiple functions in DNA organization, in modulating DNA replication, recombination, and repair, and in regulating gene expression, the mouse colonization results would be the combined effects due to loss of a subset of these functions. Little is known about HLPs and their relevance to pathogen virulence at all, although an HLP from Mycobacterium leprae was implicated in adhesion to mouse epithelial cells (55) and the H. pylori Hup protein expression level was shown to be associated with gastric carcinogenesis (56). Identifying a colonization role for a novel HLP in H. pylori connects its function to stomach persistence and to pathogenesis.…”

Innate Immune Responses in Leprosy

“…Viable bacilli have been found for at least 2 days in discharged nasal secretion ( 6 ). The hypothesis of respiratory transmission is validated by studies that demonstrated that adhesins present in M. leprae surface, like heparin-binding hemagglutinin and histone-like protein may attach in alveolar and nasal epithelial cells and both cell types are capable of sustaining bacterial survival ( 7 , 8 ). In addition, a previous study demonstrated that mce1a gene is found in M. leprae genome and that mce1a product is associated with M. leprae entry into respiratory epithelial cells ( 9 ).…”

Detection of Mycobacterium tuberculosis DNA on the oral mucosa of tuberculosis patients

“…However, the concept appeared feasible, in part because Mycobacterium cells, like most bacteria, have evolved mechanisms to adhere to surfaces, including mammalian cells. M. leprae cells were shown to adhere to nasal and alveolar epithelial cells 9 , while M. avium cells were shown to adhere to the bronchial epithelium 10 and to non-biological surfaces 11 12 . In nature, many environmental Mycobacterium species are more commonly associated with surfaces than with fluid matrices 13 .…”