The Two-Component System PhoRP-Dependent Proinflammatory Response from Infection with Mycobacterium abscessus in Cystic Fibrosis.

Abstract

Abstract The goal of this research was to determine the role of PhoRP two-component system, which is a regulatory system widely used by bacteria to sense and respond to environmental stimuli with coordinated changes in gene expression. NTM (non-tuberculous mycobacterium) Mycobacterium abscessus complex (MABSC) infect cystic fibrosis (CF) patients. Knowledge gained on the mechanism of infection, morphology, gene expression, and pathogenicity will help develop better treatment and prevent infection of this deadly mycobacterium in people with CF. This type of mycobacteria is highly resistant to antibiotics and is of major concern in healthcare because CF patients are susceptible to infection of this pathogen. Research for phoRP is limited and more knowledge is urgently needed about this two-component system for treatment advancement of CF patients. Unpublished results from the Schaefers lab have demonstrated that MABSC strains such as M. abscessus and M. Massiliense lacking phoRP are less able to survive in macrophages and less fit in murine models. The focus of my project is to understand the role of the phoRP-system and phoRP-regulated factors in the induction of a proinflammatory response from human cells. The proinflammatory response of TNFα (tumor necrosis alpha), a key inflammatory cytokine that mediates mycobacterial killing, host defense and granuloma formation (Bernut et al., 2016; Kim et al., 2017) and interleukin 6 (IL-6) is investigated. I found that Mycobacterium that lack phoRP induces more proinflammatory cytokines from human cells, suggesting a mechanism for why these mutants were less fit in virulence models. My findings demonstrate the importance of phoRP for full virulence in MABSC. In addition, the role of the putative pilin gene and putative gene glycosyltransferase (both regulated by phoRP) was examined and findings highly suggest that these two genes play a role in the virulence of M. abscessus. There was a remarkable decrease in TNFα levels when a putative glycosyltransferase gene was deleted. Additionally, when components of a putative pilin operon were deleted, there was an altered TNFα elicited from THP-1 macrophages compared to the parental strain. Together, these data demonstrate that phoRP and phoRP-regulated factors are involved in eliciting a proinflammatory response from the host.