Eimeria bovis Macromeront Formation Induces Glycolytic Responses and Mitochondrial Changes in Primary Host Endothelial Cells

Monitoring cellular dynamics upon infection using a holotomography-based approach

Many intracellular bacteria interfere with mitochondrial dynamics or target other organelles, thereby inducing a specific cellular response that could emerge as a strategy of the pathogen to ensure its survival, or as a form of defense employed by the host cell to restrict dissemination. In this context, the concomitant monitoring of both pathogen migration and (intra)cellular dynamics in live cells emerges as a pivotal aspect for the comprehension of the infection sequence and to visualize the pathogen-mediated remodeling that could occur to the entire cellular system. Holotomographic microscopy can be used to achieve this goal, allowing the simultaneous analysis of both bacterial movement and intracellular alteration for extended periods of time, with high spatial resolution and avoiding side-effects due to phototoxicity. Here we provide a holotomography-based approach to detect Listeria monocytogenes dynamics and its effects on the entire cellular system at morphological level.

Isolation of a Novel Caprine Eimeria christenseni Strain (GC) in Canary Islands and Analysis of Parasitological, Clinical, and Pathological Findings on Experimentally Infected Goat Kids

Eimeria christenseni is considered among the most pathogenic Eimeria species in goats. The aim of this study was to isolate an E. christenseni strain and to assess its infectivity, pathogenicity, and ability to develop a protective immune response. After previous collection of E. christenseni-positive faeces, purification of oocysts, and amplification in donor animals, an experimental infection was carried out. A total of 19 kids were divided into three groups: primary-infected and challenged, challenge control, and uninfected control. Infections were performed orally with 2 × 105 sporulated oocysts per animal. Oocyst shedding, clinical signs, and production parameters, in addition to haematological and histopathological features, were monitored. The results showed that the Gran Canaria (GC) E. christenseni strain had similar morphological and biological characteristics to those previously described, but no significant clinical signs were observed despite the high oocyst counts here recorded. The novel strain isolated would therefore be of low pathogenicity but still able to develop significant immunoprotective responses upon challenge infections. Its biological similarities to highly pathogenic species such as Eimeria ninakohlyakimovae and Eimeria arloingi might enable comparative studies aimed at developing alternative strategies for drug treatments, including Eimeria species (strain)-specific vaccination strategies for the efficient control of goat coccidiosis.

Neospora caninum Infection Triggers S-phase Arrest and Alters Nuclear Characteristics in Primary Bovine Endothelial Host Cells

Neospora caninum represents a major cause of abortive disease in bovines and small ruminants worldwide. As a typical obligate intracellular apicomplexan parasite, N. caninum needs to modulate its host cell for successful replication. In the current study, we focused on parasite-driven interference with host cell cycle progression. By performing DNA content-based cell cycle phase analyses in N. caninum-infected primary bovine umbilical vein endothelial cells (BUVEC), a parasite-driven S-phase arrest was detected at both 24 and 32 h p. i., being paralleled by fewer host cells experiencing the G0/G1 cell cycle phase. When analyzing S-subphases, proliferation cell nuclear antigen (per PCNA)-based experiments showed a reduced population of BUVEC in the late S-phase. Analyses on key molecules of cell cycle regulation documented a significant alteration of cyclin A2 and cyclin B1 abundance in N. caninum-infected host endothelial cells, thereby confirming irregularities in the S-phase and S-to-G2/M-phase transition. In line with cell cycle alterations, general nuclear parameters revealed smaller nuclear sizes and morphological abnormalities of BUVEC nuclei within the N. caninum-infected host cell layer. The latter observations were also confirmed by transmission electron microscopy (TEM) and by analyses of lamin B1 as a marker of nuclear lamina, which illustrated an inhomogeneous nuclear lamin B1 distribution, nuclear foldings, and invaginations, thereby reflecting nuclear misshaping. Interestingly, the latter finding applied to both non-infected and infected host cells within parasitized BUVEC layer. Additionally, actin detection indicated alterations in the perinuclear actin cap formation since typical nucleo-transversal filaments were consistently lacking in N. caninum-infected BUVEC, as also documented by significantly decreased actin-related intensities in the perinuclear region. These data indicate that N. caninum indeed alters host cell cycle progression and severely affects the host cell nuclear phenotype in primary bovine endothelial host cells. In summary, these findings add novel data on the complex N. caninum-specific modulation of host cell and nucleus, thereby demonstrating clear differences in cell cycle progression modulation driven by other closely related apicomplexans like Toxoplasma gondii and Besnotia besnoiti.

The Cellular Innate Immune Response of the Invasive Pest Insect Drosophila suzukii against Pseudomonas entomophila Involves the Release of Extracellular Traps

Drosophila suzukii is a neobiotic invasive pest that causes extensive damage to fruit crops worldwide. The biological control of this species has been unsuccessful thus far, in part because of its robust cellular innate immune system, including the activity of professional phagocytes known as hemocytes and plasmatocytes. The in vitro cultivation of primary hemocytes isolated from D. suzukii third-instar larvae is a valuable tool for the investigation of hemocyte-derived effector mechanisms against pathogens such as wasp parasitoid larvae, bacteria, fungi and viruses. Here, we describe the morphological characteristics of D. suzukii hemocytes and evaluate early innate immune responses, including extracellular traps released against the entomopathogen Pseudomonas entomophila and lipopolysaccharides. We show for the first time that D. suzukii plasmatocytes cast extracellular traps to combat P. entomophila, along with other cell-mediated reactions, such as phagocytosis and the formation of filopodia.