Vibrio cholerae Evades Neutrophil Extracellular Traps by the Activity of Two Extracellular Nucleases

Abstract

The Gram negative bacterium Vibrio cholerae is the causative agent of the secretory diarrheal disease cholera, which has traditionally been classified as a noninflammatory disease. However, several recent reports suggest that a V. cholerae infection induces an inflammatory response in the gastrointestinal tract indicated by recruitment of innate immune cells and increase of inflammatory cytokines. In this study, we describe a colonization defect of a double extracellular nuclease V. cholerae mutant in immunocompetent mice, which is not evident in neutropenic mice. Intrigued by this observation, we investigated the impact of neutrophils, as a central part of the innate immune system, on the pathogen V. cholerae in more detail. Our results demonstrate that V. cholerae induces formation of neutrophil extracellular traps (NETs) upon contact with neutrophils, while V. cholerae in return induces the two extracellular nucleases upon presence of NETs. We show that the V. cholerae wild type rapidly degrades the DNA component of the NETs by the combined activity of the two extracellular nucleases Dns and Xds. In contrast, NETs exhibit prolonged stability in presence of the double nuclease mutant. Finally, we demonstrate that Dns and Xds mediate evasion of V. cholerae from NETs and lower the susceptibility for extracellular killing in the presence of NETs. This report provides a first comprehensive characterization of the interplay between neutrophils and V. cholerae along with new evidence that the innate immune response impacts the colonization of V. cholerae in vivo. A limitation of this study is an inability for technical and physiological reasons to visualize intact NETs in the intestinal lumen of infected mice, but we can hypothesize that extracellular nuclease production by V. cholerae may enhance survival fitness of the pathogen through NET degradation.

Evasion of Neutrophil Extracellular Traps by Respiratory Pathogens

“…Seper and colleagues (38) found that a Vibrio cholerae strain deficient for two extracellular nucleases, deoxyribonuclease and xds, was less invasive than wild-type V. cholerae in immunocompetent mice, although no difference between strains was seen in neutropenic mice, and quantitative RT-PCR revealed that the presence of either NETs or DNA was able to up-regulate the expression of deoxyribonuclease and xds (38). Neisseria gonorrheae has also been shown to encode the heat-stable nuclease, nuc, thought to be important for remodeling N. gonorrheae biofilms (39).…”

Vibrio cholerae GbpA elicits necrotic cell death in intestinal cells

“…An earlier study showed that V. cholerae infection stimulates ROS production in human neutrophils (Seper et al, 2013). Furthermore, the mitochondria of cells were the main contributor of ROS generation.…”

A Thermonuclease ofNeisseria gonorrhoeaeEnhances Bacterial Escape From Killing by Neutrophil Extracellular Traps

“…Species of Streptococcus, Staphylococcus, Vibrio, and Leishmania express nucleases that aid in escape from NETs, to promote pathogen survival and spread [24][25][26][27][28]. We now add N. gonorrhoeae to this list, with 3 pieces of evidence to show that N. gonorrhoeae Nuc can degrade NETs.…”