Canine Angiostrongylus vasorum-Induced Early Innate Immune Reactions Based on NETs Formation and Canine Vascular Endothelial Cell Activation In Vitro

Fasciola hepatica soluble antigens (FhAg) induce ovine PMN innate immune reactions and NET formation in vitro and in vivo

Fasciola hepatica causes liver fluke disease, a worldwide neglected and re-emerging zoonotic disease, leading to hepatitis in humans and livestock. In the pathogenesis, flukes actively migrate through liver parenchyma provoking tissue damage. Here, parasites must confront leukocytes of the innate immune system in vivo. Polymorphonuclear neutrophils (PMN) are the most abundant granulocytes and first ones arriving at infection sites. PMN may display neutrophil extracellular traps (NETs), consisting of nuclear DNA, decorated with histones, enzymes, and antimicrobial peptides. We investigated for the first time whether F. hepatica soluble antigens (FhAg) can also trigger NETosis and innate immune reactions in exposed ovine PMN. Thus, isolated PMN were co-cultured with FhAg and NET formation was visualized by immunofluorescence and scanning electron microscopy analyses resulting in various phenotypes with spread NETs being the most detected in vitro. In line, NETs quantification via Picogreen®-fluorometric measurements revealed induction of anchored- and cell free NETs phenotypes. Live cell 3D-holotomographic microscopy revealed degranulation of stimulated PMN at 30 min exposure to FhAg. Functional PMN chemotaxis assays showed a significant increase of PMN migration (p = 0.010) and intracellular ROS production significantly increased throughout time (p = 0.028). Contrary, metabolic activities profiles of FhAg-exposed PMN did not significantly increase. Finally, in vivo histopathological analysis on F. hepatica-parasitized liver tissue sections of sheep showed multifocal infiltration of inflammatory cells within liver parenchyma, and further fluorescence microscopy analyses confirmed NETs formation in vivo. Overall, we hypothesized that NET-formation is a relevant host defence mechanism that might have a role in the pathogenesis of fasciolosis in vivo.

Cryptosporidium parvum-induced neutrophil extracellular traps in neonatal calves is a stage-independent process

Introduction

Infections with the apicomplexan obligate intracellular parasite Cryptosporidium parvum lead to cryptosporidiosis-a worldwide zoonotic infection. C. parvum is one of the most common diarrheal pathogens in young calves, which are the main reservoir of the pathogen. Cryptosporidiosis leads to severe economic losses in the calf industry and being a major contributor to diarrhea morbidity and mortality in children. Polymorphonuclear neutrophils (PMN) are part of the innate immune system. Their effector mechanisms directed against invasive parasites include phagocytosis, production of antimicrobial molecules as well as the formation of so-called neutrophil extracellular traps (NETs). Like other leukocytes of the innate immune system, PMN are thus able to release chromatin fibers enriched with antimicrobial granular molecules extracellularly thereby immobilizing and partially killing invasive bacteria, viruses, fungi and parasites.

Methods

In vitro interactions of neonatal bovine PMN and C. parvum-oocysts and sporozoites were illustrated microscopically via scanning electron microscopy- and live cell imaging 3D holotomographic microscopy analyses. C. parvum-triggered NETosis was quantified via extracellular DNA measurements as well as verified via detection of NET-typical molecules [histones, neutrophil elastase (NE)] through immunofluorescence microscopy analysis. To verify the role of ATP in neonatal-derived NETosis, inhibition experiments were performed with NF449 (purinergic receptor antagonist with high specificity to P2X1 receptor).

Results and discussion

Using immunofluorescence- and SEM-based analyses, we demonstrate here for the first time that neonate bovine PMN are capable of forming NETs against C. parvum-sporozoites and oocysts, thus as a stage-independent cell death process. Our data further showed that C. parvum strongly induces suicidal neonatal NETosis in a P2X1-dependent manner, suggesting anti-cryptosporidial effects not only through firm sporozoite ensnarement and hampered sporozoite excystation, but also via direct exposure to NETs-associated toxic components.

High Presence of NETotic Cells and Neutrophil Extracellular Traps in Vaginal Discharges of Women with Vaginitis: An Exploratory Study

Infectious vaginitis is a microbiological syndrome of great importance in public health that affects millions of women worldwide. However, no studies have explored the phenomenon of the production of the neutrophil extracellular traps (NETs) that are released into the female reproductive tract in these pathologies. This study aimed to determine the presence of NETosis in vaginal discharges of women with bacterial vaginosis, candidiasis, and trichomoniasis by characterizing NETs. Extracellular DNA with neutrophil elastase and citrullinated histones was identified to confirm the NET components (n = 10). The concentration, phenotypes of NETs, and number of NETotic cells were determined. The results showed an increase in NETotic cells in women with Candida albicans (CA) and Trichomonas vaginalis (TV) and an increase in NETs in TV-induced vaginitis. Samples of CA- and TV-infected women showed different NET phenotypes (diffNETs, sprNETs, and aggNETs); diffNETs were found in high concentrations in samples with CA and were increased in three types of NETs in TV infections. Samples with intermediate microbiota and bacterial vaginosis showed increased NETotic cells while the intermediate microbiota presented a higher concentration of NETs. Therefore, alterations in the microbiota and the presence of fungal and parasitic infections are important stimuli for the activation and induction of NETosis, and their cytotoxic effects could enhance tissue damage.

Nationwide Seroprevalence Survey of Angiostrongylus vasorum-Derived Antigens and Specific Antibodies in Dogs from Colombia

Angiostrongylus vasorum is a cardiopulmonary nematode, causing several clinical manifestations in dogs, e.g., severe respiratory signs, coagulopathy, and gastrointestinal or neurological signs. In the last decades, this parasite has been described to spread and emerge in Europe and North America. Scant studies on A. vasorum occurrence in South America exist. Recently, A. vasorum was detected in gastropod intermediate hosts in Colombia, where data on definitive host prevalence, e.g., dogs and wild canids, are still limited. Therefore, the sera of 955 dogs, varying in age and breed from seven different departments all over Colombia, were collected and analysed for A. vasorum antigens and parasite-specific antibodies by ELISA. In total, 1.05 % (n = 10; 95 % CI 0.40–1.69) of the samples were antigen-positive and 2.62 % (n = 25; 95 % CI 1.61–3.63) were antibody-positive. These results confirm the presence of A. vasorum in Colombia, although positive results in antigen and antibody reactions in the same dog were not detected. This study is the first large-scale survey on A. vasorum seroprevalences in dogs from Colombia.

Gurltia paralysans: A Neglected Angio-Neurotropic Parasite of Domestic Cats (Felis catus) and Free-Ranging Wild Felids (Leopardus spp.) in South America

Gurltia paralysans is a neglected and re-emerging metastrongyloid angio-neurotropic nematode causing severe chronic meningomyelitis in domestic cats (Felis catus) as well as in free-ranging small wild felids such as kodkods (Leopardus guigna), margays (Leopardus wiedii) and the northern tiger cat (Leopardus triginus) in South America. Within these definitive hosts (DH), adult males and females of G. paralysans parasitize the leptomeningeal veins of the subarachnoid space and/or the meningeal veins of spinal cord parenchyma, inducing vascular alterations. Feline gurltiosis has been associated with progressive thrombophlebitis of the meningeal veins, resulting in ambulatory paraparesis, paraplegia, ataxia, hindlimb proprioceptive deficit, uni- or bilateral hyperactive patellar reflexes, faecal and urinary incontinence, and tail paralysis. The complete life cycle of G. paralysans has not been elucidated yet, but most probably involves gastropods as obligate intermediate hosts (IH). In terms of epidemiology, G. paralysans infections in domestic and wild felids are scattered around various South American countries, with hyperendemic areas in southern parts of Chile. Etiological diagnosis of G. paralysans still represents a challenge for clinicians due to a lack of evidence of the excretion of either eggs or larvae in faeces or in other body fluids. Diagnosis is based on clinical neurological signs, imaging findings through computed tomography (CT), myelography, magnetic resonance imaging (MRI), and post mortem examination. Nonetheless, novel diagnostic tools have been developed, including semi-nested PCR for detecting circulating G. paralysans DNA in the cerebrospinal fluid, serum and blood samples as well as in serological diagnostic kits detecting parasite-derived antigens, but these need validation for routine usage. The hypothetical life cycle of G. paralysans is addressed in this article, including the exogenous stages (i.e., eggs, and first- (L1), second- (L2) and third-stage (L3) larvae) and obligate gastropod IH and/or paratenic hosts (PH), and we propose possible anatomical migration routes of infective L3 that reach the leptomeningeal veins in vivo. Finally, the pro-inflammatory endothelium- and leukocyte-derived innate immune reactions of the host against G. paralysans, which most likely result in thrombophlebitis and meningomyelitis, are briefly touched on.

Hemostatic Dysfunction in Dogs Naturally Infected with Angiostrongylus vasorum—A Narrative Review

This narrative review aims to describe Angiostrongylus vasorum-induced hemostatic dysfunction of dogs with emphasis on clinical and laboratory findings as well as potential therapeutic strategies for the bleeding patient. Canine angiostrongylosis (CA) is a disease with potentially high morbidity and mortality in endemic areas and with fatal outcome often associated with either severe respiratory compromise, pulmonary hypertension and right-sided heart failure, or hemostatic dysfunction with severe bleeding. The most common signs of hemorrhage are hematomas, petecchiation, ecchymoses, oral mucosal membrane bleeding and scleral bleeding, while intracranial and pulmonary hemorrhage are among the most severe. The pathophysiological mechanisms underlying hemostatic dysfunction in these patients are presently researched. While the larval effect on platelets remains unknown, the parasite appears to induce dysregulation of hemostatic proteins, with studies suggesting a mixture of pro-coagulant protein consumption and hyperfibrinolysis. Importantly, not all dogs display the same hemostatic abnormalities. Consequently, characterizing the hemostatic state of the individual patient is necessary, but has proven difficult with traditional coagulation tests. Global viscoelastic testing shows promise, but has limited availability in general practice. Treatment of A. vasorum-infected dogs with hemostatic dysfunction relies on anthelmintic treatment as well as therapy directed at the individual dog’s specific hemostatic alterations.

Pneumothorax in a persistent canine Angiostrongylus vasorum infection

Canine angiostrongylosis is a gastropod-borne parasitosis caused by the cosmopolitan nematode Angiostrongylus vasorum. It is associated with cardiorespiratory disorders and eventually fatal coagulopathies. A 6-months-old female dog previously diagnosed with bronchopneumonia and pneumothorax, treated accordingly without success, was hospitalized for further treatment. Complementary diagnostics confirmed previous findings plus pneumomediastinum, thoracic exudate, leucocytosis, thrombocytosis, hypercoagulability, and hyperglobulinemia. Coprological analysis showed a severe patent A. vasorum infection. After the third daily fenbendazole administration, all A. vasorum larvae were found dead in follow-up coprological analyses while in intensive care. Upon release, the dog was monitored until full clinical recovery 3 months later. Up to date, A. vasorum infection-related pneumothorax was rarely described, particularly with full recovery of such a young patient. Thus, a parasitological aetiology should be considered for dogs with severe bronchopneumonia or pneumothorax, especially in Europe and South America where increasing numbers of canine angiostrongylosis cases call for enhanced awareness of veterinary practitioners.