Human neutrophil extracellular traps do not impair in vitro Toxoplasma gondii infection

Isabela S Macedo; Flávio A Lara; Helene S Barbosa; Elvira M Saraiva; Rubem F S Menna-Barreto; Rafael M Mariante

doi:10.3389/fimmu.2023.1282278

Human neutrophil extracellular traps do not impair in vitro Toxoplasma gondii infection

Front Immunol. 2023 Dec 5:14:1282278. doi: 10.3389/fimmu.2023.1282278. eCollection 2023.

Authors

Isabela S Macedo¹, Flávio A Lara², Helene S Barbosa¹, Elvira M Saraiva³, Rubem F S Menna-Barreto⁴, Rafael M Mariante¹

Affiliations

¹ Laboratório de Biologia Estrutural, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil.
² Laboratório de Microbiologia Celular, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil.
³ Laboratório de Imunobiologia das Leishmanioses, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
⁴ Laboratório de Biologia Celular, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil.

Abstract

Introduction: Toxoplasma gondii, responsible for causing toxoplasmosis, is a prevalent food and waterborne pathogen worldwide. It commonly infects warm-blooded animals and affects more than a third of the global human population. Once ingested, the parasite enters the host's small intestine and rapidly disseminates throughout the body via the bloodstream, infiltrating various tissues. Leukocyte-driven responses are vital against T. gondii, with neutrophils playing a dual role: swiftly recruited to infection sites, releasing inflammatory mediators, and serving as a replication hub and Trojan horses, aiding parasite spread. Neutrophils from various hosts release extracellular traps (NETs) against the protozoan. However, gaps persist regarding the mechanisms of NETs production to parasite and their significance in infection control. This study investigates the interplay between human neutrophils and T. gondii, exploring dynamics, key molecules, and signaling pathways involved in NETs production upon protozoan challenge.

Methods and results: Using confocal and electron microscopy, live cell imaging, pharmacological inhibitors, and DNA quantification assays, we find that human neutrophils promptly release both classical and rapid NETs upon pathogen stimulation. The NETs structure exhibits diverse phenotypes over time and is consistently associated with microorganisms. Mechanisms involve neutrophil elastase and peptidylarginine deiminase, along with intracellular calcium signaling and the PI3K pathway. Unexpectedly, human traps do not diminish viability or infectivity, but potentially aid in capturing parasites for subsequent neutrophil phagocytosis and elimination.

Discussion: By revealing NETs formation mechanisms and their nuanced impact on T. gondii infection dynamics, our findings contribute to broader insights into host-pathogen relationships.

Keywords: NET; Toxoplasma gondii; classic/rapid NETs; entrapment; human neutrophils; infectivity; live cell imaging; viability.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Extracellular Traps* / metabolism
Humans
Neutrophils / metabolism
Phosphatidylinositol 3-Kinases / metabolism
Toxoplasma* / physiology
Toxoplasmosis* / metabolism

Substances

Phosphatidylinositol 3-Kinases

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This research was funded by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Universal 432255/2016-8), Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ, scholarship E-26/260.048/2018, Redes de Pesquisa em Saúde E-26/211.570/2019), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Finance Code 001), and Instituto Oswaldo Cruz/Fiocruz.