The state of art of neutrophil extracellular traps in protozoan and helminthic infections

Abstract

Neutrophil extracellular traps (NETs) are DNA fibers associated with histones, enzymes from neutrophil granules and anti-microbial peptides. NETs are released in a process denominated NETosis, which involves sequential steps that culminate with the DNA extrusion. NETosis has been described as a new mechanism of innate immunity related to defense against different pathogens. The initial studies of NETs were carried out with bacteria and fungi, but currently a large variety of microorganisms capable of inducing NETs have been described including protozoan and helminth parasites. Nevertheless, we have little knowledge about how NETosis process is carried out in response to the parasites, and about its implication in the resolution of this kind of disease. In the best case, the NETs entrap and kill parasites in vitro, but in others, immobilize the parasites without affecting their viability. Moreover, insufficient studies on the NETs in animal models of infections that would help to define their role, and the association of NETs with chronic inflammatory pathologies such as those occurring in several parasitic infections have left open the possibility of NETs contributing to pathology instead of protection. In this review, we focus on the reported mechanisms that lead to NET release by protozoan and helminth parasites and the evidence that support the role of NETosis in the resolution or pathogenesis of parasitic diseases.

The Role of Small Extracellular Vesicles in Viral-Protozoan Symbiosis: Lessons From Trichomonasvirus in an Isogenic Host Parasite Model

“…The single human protein (MGAM) more abundant in the virus-positive TV phenotype is involved in neutrophil degranulation. Neutrophils are important in resolving protozoan parasitic diseases (Mercer et al, 2018;Diaz-Godinez and Carrero, 2019) using killing mechanisms including degranulation whereby they release inflammatory mediators, proteases, and cytolytic factors (Lacy, 2006). Whether MGAM facilitates virus-positive TV sEVs in dampening the immune response should be investigated since it may have broader implications for neutrophil regulation.…”

Influence of the Host and Parasite Strain on the Immune Response During Toxoplasma Infection

“…Neutrophils, the most abundant cells at the site of infection, can form neutrophil extracellular traps, or NETs. These consist of extracellular masses of nuclear DNA fibers associated with histones and enzymes of cytoplasmic granules and anti-microbial peptides, such as myeloperoxidase (MPO) or lactoperoxidase, that are able to kill various microorganisms (Brinkmann et al, 2004 ; Díaz-Godínez and Carrero, 2019 ). In the case of Toxoplasma , NETs cause the immobilization of entrapped parasites, leading to their death (Abdallah et al, 2012 ; Yildiz et al, 2017 ).…”

Neutrophil Adaptations upon Recruitment to the Lung: New Concepts and Implications for Homeostasis and Disease

“…The hallmark function of neutrophils is microbial clearance, especially of bacteria, by phagocytosis. It is now well understood how bacteria are captured and digested internally [1,51], but neutrophils are also well equipped to clear viruses [52,53] and fungi [2], as well as contribute to defense against parasites [54]. Figure 1.…”