The SUN-like protein TgSLP1 is essential for nuclear division in the apicomplexan parasite Toxoplasma gondii.

Connections between the nucleus and the cytoskeleton are important for positioning and division of the nucleus. In most eukaryotes, the linker of nucleoskeleton and cytoskeleton (LINC) complex spans the outer and inner nuclear membranes and connects the nucleus to the cytoskeleton. In opisthokonts, it is composed of Klarsicht, ANC-1 and Syne homology (KASH) domain proteins and Sad1 and UNC-84 (SUN) domain proteins.

Where is the EXIT? Phenotypic screens for new egress factors in apicomplexan parasites.

Apicomplexans, such as Plasmodium and Toxoplasma are obligate intracellular parasites that invade, replicate and finally EXIT their host cell. During replication within a parasitophorous vacuole (PV), the parasites establish an extensive F-actin-containing network that connects individual parasites and is required for material exchange, recycling and the final steps of daughter cell assembly. After multiple rounds of replication, the parasites exit the host cell involving multiple signalling cascades, disassembly of the network, secretion of microneme proteins and activation of the acto-myosin motor.

A splitCas9 phenotypic screen in Toxoplasma gondii identifies proteins involved in host cell egress and invasion.

Apicomplexan parasites, such as Toxoplasma gondii, have specific adaptations that enable invasion and exit from the host cell. Owing to the phylogenetic distance between apicomplexan parasites and model organisms, comparative genomics has limited capacity to infer gene functions. Further, although CRISPR/Cas9-based screens have assigned roles to some Toxoplasma genes, the functions of encoded proteins have proven difficult to assign.

Serological and molecular survey of hepatitis E virus in cats and dogs in Spain.

Hepatitis E virus (HEV) is an emerging zoonotic pathogen that is currently recognized as one of the major causes of acute human hepatitis worldwide. In Europe, the increasing number of hepatitis E cases is mainly associated with the consumption of animal food products or contact with infected animals. Dogs and cats have been suggested as a zoonotic source of HEV infection.

An endocytic-secretory cycle participates in Toxoplasma gondii in motility.

Apicomplexan parasites invade host cells in an active process involving their ability to move by gliding motility. While the acto-myosin system of the parasite plays a crucial role in the formation and release of attachment sites during this process, there are still open questions regarding the involvement of other mechanisms in parasite motility. In many eukaryotes, a secretory-endocytic cycle leads to the recycling of receptors (integrins), necessary to form attachment sites, regulation of surface area during motility, and generation of retrograde membrane flow.

UAP56 is a conserved crucial component of a divergent mRNA export pathway in Toxoplasma gondii.

Nucleo-cytoplasmic RNA export is an essential post-transcriptional step to control gene expression in eukaryotic cells and is poorly understood in apicomplexan parasites. With the exception of UAP56, a component of TREX (Transcription Export) complex, other components of mRNA export machinery are not well conserved in divergent supergroups. Here, we use Toxoplasma gondii as a model system to functionally characterize TgUAP56 and its potential interaction factors.

Gliding Associated Proteins Play Essential Roles during the Formation of the Inner Membrane Complex of Toxoplasma gondii.

The inner membrane complex (IMC) of apicomplexan parasites is a specialised structure localised beneath the parasite's plasma membrane, and is important for parasite stability and intracellular replication. Furthermore, it serves as an anchor for the myosin A motor complex, termed the glideosome. While the role of this protein complex in parasite motility and host cell invasion has been well described, additional roles during the asexual life cycle are unknown.

Vacuolar protein sorting mechanisms in apicomplexan parasites.

The phylum Apicomplexa comprises more than 5000 species including pathogens of clinical and economical importance. These obligate intracellular parasites possess a highly complex endomembrane system to build amongst others three morphologically distinct secretory organelles: rhoptries, micronemes and dense granules. Proteins released by these organelles are essential for invasion and hijacking of the host cell.

Characterization of the Neospora caninum NcROP40 and NcROP2Fam-1 rhoptry proteins during the tachyzoite lytic cycle.

Virulence factors from the ROP2-family have been extensively studied in Toxoplasma gondii, but in the closely related Neospora caninum only NcROP2Fam-1 has been partially characterized to date. NcROP40 is a member of this family and was found to be more abundantly expressed in virulent isolates. Both NcROP2Fam-1 and NcROP40 were evaluated as vaccine candidates and exerted a synergistic effect in terms of protection against vertical transmission in mouse models, which suggests that they may be relevant for parasite pathogenicity.

Conditional U1 Gene Silencing in Toxoplasma gondii.

The functional characterisation of essential genes in apicomplexan parasites, such as Toxoplasma gondii or Plasmodium falciparum, relies on conditional mutagenesis systems. Here we present a novel strategy based on U1 snRNP-mediated gene silencing. U1 snRNP is critical in pre-mRNA splicing by defining the exon-intron boundaries.

Advantages and disadvantages of conditional systems for characterization of essential genes in Toxoplasma gondii.

The dissection of apicomplexan biology has been highly influenced by the genetic tools available for manipulation of parasite DNA. Here, we describe different techniques available for the generation of conditional mutants. Comparison of the advantages and disadvantages of the three most commonly used regulation systems: the tetracycline inducible system, the regulation of protein stability and site-specific recombination are discussed.

Clinical outcome and vertical transmission variability among canine Neospora caninum isolates in a pregnant mouse model of infection.

We compared the clinical outcome and vertical transmission of six canine Neospora caninum isolates using a pregnant BALB/c model. Four of the isolates were obtained from oocysts of naturally infected dogs (Nc-Ger2, Nc-Ger3, Nc-Ger6 and Nc-6Arg) and two were from diseased dogs with neurological signs (Nc-Bahia and Nc-Liv). The dams were inoculated with 2×106 tachyzoites of each isolate at day 7 of pregnancy.

Mice congenitally infected with low-to-moderate virulence Neospora caninum isolates exhibited clinical reactivation during the mating period without transmission to the next generation.

Endogenous transplacental transmission (EnTT) is the major transmission route of Neospora caninum in cattle. Thus, the development of a standardised experimental model of EnTT is needed for more appropriate testing of parasite biology and control strategies. A recent study reported up to 40-50% EnTT rates in chronically infected dams with either high or low-to-moderate virulence isolates, although low fertility rates were observed in dams inoculated with the high virulence isolate.

Specific antibody responses against Neospora caninum recombinant rNcGRA7, rNcSAG4, rNcBSR4 and rNcSRS9 proteins are correlated with virulence in mice.

The intraspecific diversity of Neospora caninum is a determinant for in vivo parasite virulence and in vitro parasite behaviour. The relationship between isolate virulence and specific antibody responses against key parasite proteins has not been well characterized. The response kinetics and the differences in specific anti-rNcGRA7, -rNcSAG4, -rNcBSR4 and -rNcSRS9 antibody levels were analysed by recombinant protein-based ELISA in groups of mice inoculated with 10 different N.

Low efficacy of NcGRA7, NcSAG4, NcBSR4 and NcSRS9 formulated in poly-ε-caprolactone against Neospora caninum infection in mice.

The protective efficacy of vaccination with Neospora caninum recombinant antigens was evaluated in Balb/c pregnant and non-pregnant mouse models of neosporosis. A major immunodominant dense granule protein (NcGRA7) and three bradyzoite-specific surface antigens (NcSAG4, NcBSR4 and NcSRS9) were expressed in Escherichia coli and encapsulated within poly-ε-caprolactone (PCL) nanoparticles for the first time. Good efficiencies of entrapment (greater than 50%) were obtained for all encapsulated proteins.

Influence of Neospora caninum intra-specific variability in the outcome of infection in a pregnant BALB/c mouse model.

Previous assays in pregnant animals have demonstrated the effect of different host factors and timing of infection on the outcome of neosporosis during pregnancy. However, the influence of Neospora caninum isolate itself has been poorly investigated. Here, we compared the effects on clinical outcome and vertical transmission observed in a pregnant mouse model following infection with 10 different N.