ESX-5-deficient Mycobacterium marinum is hypervirulent in adult zebrafish

Abstract

SummaryESX-5 is a mycobacterial type VII protein secretion system responsible for transport of numerous PE and PPE proteins. It is involved in the induction of host cell death and modulation of the cytokine response in vitro. In this work, we studied the effects of ESX-5 in embryonic and adult zebrafish using Mycobacterium marinum. We found that ESX-5-deficient M. marinum was slightly attenuated in zebrafish embryos. Surprisingly, the same mutant showed highly increased virulence in adult zebrafish, characterized by increased bacterial loads and early onset of granuloma formation with rapid development of necrotic centres. This early onset of granuloma formation was accompanied by an increased expression of pro-inflammatory cytokines and tissue remodelling genes in zebrafish infected with the ESX-5 mutant. Experiments using RAG-1-deficient zebrafish showed that the increased virulence of the ESX-5 mutant was not dependent on the adaptive immune system. Mixed infection experiments with wildtype and ESX-5 mutant bacteria showed that the latter had a specific advantage in adult zebrafish and outcompeted wild-type bacteria. Together our experiments indicate that ESX-5-mediated protein secretion is used by M. marinum to establish a moderate and persistent infection.

Animal Models of Tuberculosis: Zebrafish

“…Interestingly, although this mutant is clearly attenuated in embryos, the effect is only minor in the context of the adaptive immune system. The reverse is also possible, as was shown by Weerdenburg et al (2012). An M. marinum mutant disrupted in ESX-5 secretion was slightly attenuated in embryos, but showed increased virulence in adult zebrafish, characterized by highly increased bacterial loads and early onset of granuloma formation.…”

Recommendations for Health Monitoring and Reporting for Zebrafish Research Facilities

“…29 Infection with this species has been documented to alter gene expression in several studies. [30][31][32][33] Finally, fast-growing M. chelonae has been observed to autofluoresce, which may confound studies using fluorescence to examine biological processes. 34 M. abscessus is very close phylogenetically to M. chelonae, and similarly produces predominantly subclinical infections; the recently described M. saopaulense also belongs to this group.…”

A Review of Secretion Systems in Pathogenic and Non-Pathogenic Bacteria

“…Although Gram-negative bacteria have only one membrane, but some of them and most mycobacteria have a cell wall, which are widely surrounded by lipids called mycomembrane and are mostly formed of mycolic acids covalently attached to free fats (glycols) [44][45][46][47][48] . As a result, the genomes of these species, code specific secretion systems that are named Type VII secretion systems (T7SS), to transfer virulence factors in their complex cell coverings.…”

“…In M.marinum, ESX-5, the release of a large number of proteins is responsible for mycobacterial proteins called PE and PPE 46 , and the immune system play a role in the changes 45 . In Mycobacterium marinum, ESX-5 is responsible for the release of a large number of proteins in mycobacterial sections called PE and PPE proteins and play an important role modulation of immune system 45,47,48 . While non-pathogenic mycobacteria only have a few of these proteins.…”