Shaping the Microbial Landscape: Parasitoid-Driven Modifications of Bactrocera dorsalis Microbiota.

Koinobiont endoparasitoids regulate the physiology of their hosts through altering host immuno-metabolic responses, processes which function in tandem to shape the composition of the microbiota of these hosts. Here, we employed 16S rRNA and ITS amplicon sequencing to investigate whether parasitization by the parasitoid wasps, Diachasmimorpha longicaudata (Ashmaed) (Hymenoptera: Braconidae) and Psyttalia cosyrae (Wilkinson) (Hymenoptera: Braconidae), induces gut dysbiosis and differentially alter the gut microbial (bacteria and fungi) communities of an important horticultural pest, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). We further investigated the composition of bacterial communities of adult D. longicaudata and P. cosyrae to ascertain whether the adult parasitoids and parasitized host larvae share microbial taxa through transmission. We demonstrated that parasitism by D. longicaudata induced significant gut perturbations, resulting in the colonization and increased relative abundance of pathogenic gut bacteria. Some pathogenic bacteria like Stenotrophomonas and Morganella were detected in both the guts of D. longicaudata-parasitized B. dorsalis larvae and adult D. longicaudata wasps, suggesting a horizontal transfer of microbes from the parasitoid to the host. The bacterial community of P. cosyrae adult wasps was dominated by Arsenophonus nasoniae, whereas that of D. longicaudata adults was dominated by Paucibater spp. and Pseudomonas spp. Parasitization by either parasitoid wasp was associated with an overall reduction in fungal diversity and evenness. These findings indicate that unlike P. cosyrae which is avirulent to B. dorsalis, parasitization by D. longicaudata induces shifts in the gut bacteriome of B. dorsalis larvae to a pathobiont-dominated community. This mechanism possibly enhances its virulence against the pest, further supporting its candidacy as an effective biocontrol agent of this frugivorous tephritid fruit fly pest.

SOD3 suppresses early cellular immune responses to parasite infection.

Host immune responses are tightly controlled by various immune factors during infection, and protozoan parasites also manipulate the immune system to evade surveillance, leading to an evolutionary arms race in host‒pathogen interactions; however, the underlying mechanisms are not fully understood. We observed that the level of superoxide dismutase 3 (SOD3) was significantly elevated in both Plasmodium falciparum malaria patients and mice infected with four parasite species. SOD3-deficient mice had a substantially longer survival time and lower parasitemia than control mice after infection, whereas SOD3-overexpressing mice were much more vulnerable to parasite infection. We revealed that SOD3, secreted from activated neutrophils, bound to T cells, suppressed the interleukin-2 expression and concomitant interferon-gamma responses crucial for parasite clearance. Overall, our findings expose active fronts in the arms race between the parasites and host immune system and provide insights into the roles of SOD3 in shaping host innate immune responses to parasite infection.

Parasite infection in a cell population: role of the partitioning kernel.

We consider a cell population subject to a parasite infection. Cells divide at a constant rate and, at division, share the parasites they contain between their two daughter cells. The sharing may be asymmetric, and its law may depend on the number of parasites in the mother. Cells die at a rate which may depend on the number of parasites they carry, and are also killed when this number explodes. We study the survival of the cell population as well as the mean number of parasites in the cells, and focus on the role of the parasites partitioning kernel at division.

Plasmodium vivax spleen-dependent protein 1 and its role in extracellular vesicles-mediated intrasplenic infections.

Recent studies indicate that human spleen contains over 95% of the total parasite biomass during chronic asymptomatic infections caused by Plasmodium vivax. Previous studies have demonstrated that extracellular vesicles (EVs) secreted from infected reticulocytes facilitate binding to human spleen fibroblasts (hSFs) and identified parasite genes whose expression was dependent on an intact spleen. Here, we characterize the P. vivax spleen-dependent hypothetical gene (PVX_114580). Using CRISPR/Cas9, PVX_114580 was integrated into P. falciparum 3D7 genome and expressed during asexual stages. Immunofluorescence analysis demonstrated that the protein, which we named P. vivax Spleen-Dependent Protein 1 (PvSDP1), was located at the surface of infected red blood cells in the transgenic line and this localization was later confirmed in natural infections. Plasma-derived EVs from P. vivax-infected individuals (PvEVs) significantly increased cytoadherence of 3D7_PvSDP1 transgenic line to hSFs and this binding was inhibited by anti-PvSDP1 antibodies. Single-cell RNAseq of PvEVs-treated hSFs revealed increased expression of adhesion-related genes. These findings demonstrate the importance of parasite spleen-dependent genes and EVs from natural infections in the formation of intrasplenic niches in P. vivax, a major challenge for malaria elimination.

Intraspecific variation in Gyrodactylus mediotorus and G. crysoleucas (Gyrodactylidae) from Nearctic shiners (Leuciscidae): evidence for ongoing speciation, host-switching, and parasite translocation.

A parasitological investigation of Cyprinella venusta and Notropis cf. stramineus sampled in Texas, USA, in the Guadalupe River, revealed the presence of Gyrodactylus crysoleucas Mizelle and Kritsky, 1967 on C. venusta, and Gyrodactylus mediotorus King, Marcogliese, Forest, McLaughlin & Bentzen, 2013 on both fish species. This represents new leuscicid fish hosts and locality records for these two gyrodactylids. Gyrodactylus crysoleucas previously identified from both non-native Californian Notemigonus crysoleucas and from farmed stocks in Minnesota demonstrated intraspecific variability in terms of morphology and genetics as a local adaptation associated with isolation by distance. Results further confirmed G. crysoleucas as alien in the western USA and suggested host-switching involving C. venusta and N. crysoleucas. Conservative morphology and genetics on the part of G. mediotorus from C. venusta and N. cf. stramineus (Guadalupe River) was observed, while higher genetic divergence in the ITS sequences associated with morphological discrepancy was found between the studied G. mediotorus specimens and those of Notropis hudsonius than when considering the parasites of Notropis texanus. The separation of G. mediotorus into geographical subgroups may indicate ongoing speciation linked to the Pleistocene glaciations in North America, and to hydrographic barriers that facilitated separate evolutionary paths leading to speciation. We suggest that deep investigations of Gyrodactylus populations will help to understand the speciation of these parasites and their adaptation to Nearctic fish hosts.

Title: Variation intraspécifique chez Gyrodactylus mediotorus et G. crysoleucas (Gyrodactylidae), parasites de ménés néarctiques (Leuciscidae) : preuves d'une spéciation en cours, d'un changement d'hôte et d'une translocation de parasites. Abstract: Une enquête parasitologique sur Cyprinella venusta et Notropis cf. stramineus échantillonnés au Texas, États-Unis, dans la rivière Guadalupe, a révélé la présence de Gyrodactylus crysoleucas Mizelle et Kritsky, 1967 sur C. venusta, et de Gyrodactylus mediotorus King, Marcogliese, Forest, McLaughlin & Bentzen, 2013 sur les deux espèces de poissons. Ceci représente de nouveaux poissons Leuciscidae hôtes et des nouvelles localités pour ces deux Gyrodactylidae. Gyrodactylus crysoleucas, identifié précédemment à partir de Notemigonus crysoleucas californiens non indigènes et de stocks d'élevage du Minnesota a démontré une variabilité intraspécifique en termes de morphologie et de génétique en tant qu'adaptation locale associée à l'isolement par la distance. Les résultats ont en outre confirmé que G. crysoleucas était exotique dans l'ouest des États-Unis et ont suggéré un changement d'hôte impliquant C. venusta et N. crysoleucas. Une morphologie et une génétique conservatrices pour G. mediotorus de C. venusta et N. cf. stramineus (rivière Guadalupe) ont été observées, tandis qu'une divergence génétique plus élevée dans les séquences ITS, associée à une divergence morphologique, a été trouvée chez les spécimens étudiés de G. mediotorus et de Notropis hudsonius lorsque l'on considère les parasites de Notropis texanus. La séparation de G. mediotorus en sous-groupes géographiques peut indiquer une spéciation continue liée aux glaciations du Pléistocène en Amérique du Nord et à des barrières hydrographiques qui ont facilité des chemins évolutifs séparés menant à la spéciation. Nous suggérons que des études approfondies sur les populations de Gyrodactylus aideront à comprendre la spéciation de ces parasites et leur adaptation aux poissons hôtes néarctiques.

Trichomonas vaginalis extracellular vesicles up-regulate and directly transfer adherence factors promoting host cell colonization.

Trichomonas vaginalis, a common sexually transmitted parasite that colonizes the human urogenital tract, secretes extracellular vesicles (TvEVs) that are taken up by human cells and are speculated to be taken up by parasites as well. While the crosstalk between TvEVs and human cells has led to insight into host:parasite interactions, roles for TvEVs in infection have largely been one-sided, with little known about the effect of TvEV uptake by T. vaginalis. Approximately 11% of infections are found to be coinfections of multiple T. vaginalis strains. Clinical isolates often differ in their adherence to and cytolysis of host cells, underscoring the importance of understanding the effects of TvEV uptake within the parasite population. To address this question, our lab tested the ability of a less adherent strain of T. vaginalis, G3, to take up fluorescently labeled TvEVs derived from both itself (G3-EVs) and TvEVs from a more adherent strain of the parasite (B7RC2-EVs). Here, we showed that TvEVs generated from the more adherent strain are internalized more efficiently compared to the less adherent strain. Additionally, preincubation of G3 parasites with B7RC2-EVs increases parasite aggregation and adherence to host cells. Transcriptomics revealed that TvEVs up-regulate expression of predicted parasite membrane proteins and identified an adherence factor, heteropolysaccharide binding protein (HPB2). Finally, using comparative proteomics and superresolution microscopy, we demonstrated direct transfer of an adherence factor, cadherin-like protein, from TvEVs to the recipient parasite's surface. This work identifies TvEVs as a mediator of parasite:parasite communication that may impact pathogenesis during mixed infections.

Pathogenicity associated with an infestation of the marine leech parasite Pterobdella arugamensis in farmed fish.

The marine leech Pterobdella arugamensis is a hematophagous parasite, and the extent of injury to the host largely depends on the number of attached leeches. This study aimed to assess the pathogenicity of marine leeches in Asian seabass (Lates calcarifer) and tiger grouper (Epinephelus fuscoguttatus) fingerlings under laboratory conditions. Five groups of healthy Asian seabass and tiger grouper were exposed to varying numbers of marine leeches (0, 1, 10, 30, or 70 per fish) for 7 d. Infested Asian seabass and tiger grouper both showed pathological changes even with only 1 leech, manifesting as clinical signs like haemorrhages. The cumulative mortality at 7 d post-exposure (dpe) was 11 or 33% for Asian seabass infested with 1 or 10 marine leeches, respectively. Fish with 30 or 70 marine leeches showed higher rates of mortality (56%). A similar trend was seen in tiger grouper, with mortality rates reaching 78% in fish with 30 or 70 marine leeches, and 56 or 33% in fish with 10 leeches or 1 leech, respectively. Factorial analysis of mortality after 7 dpe between both species showed significant differences (2-way ANOVA p = 0.001) when exposed to varying numbers of marine leeches. The haematocrit values differed significantly between Asian seabass or tiger grouper infested with either 0 or 1 marine leech and those infested with 10, 30, or 70 marine leeches (1-way ANOVA, p = 0.0001). This suggests that marine leech infestation has a measurable impact on both species. Consequently, fish farmers should promptly address leech infestation upon discovery in their cages.

Alterations of plasma circulating microRNAs in BALB/c mice with Toxocara canis visceral and cerebral larva migrans.

BACKGROUND: Human toxocariasis is a neglected parasitic disease characterised by the syndromes visceral, cerebral, and ocular larva migrans. This disease is caused by the migrating larvae of Toxocara roundworms from dogs and cats, affecting 1.4 billion people globally. Via extracellular vesicles (EVs), microRNAs have been demonstrated to play roles in host-parasite interactions and proposed as circulating biomarkers for the diagnosis and follow-up of parasitic diseases. METHODS: Small RNA-seq was conducted to identify miRNAs in the infective larvae of T. canis and plasma EV-containing preparations of infected BALB/c mice. Differential expression analysis and target prediction were performed to indicate miRNAs involved in host-parasite interactions and miRNAs associated with visceral and/or cerebral larva migrans in the infected mice. Quantitative real-time polymerase chain reaction (PCR) was used to amplify circulating miRNAs from the infected mice. RESULTS: This study reports host and parasite miRNAs in the plasma of BALB/c mice with visceral and cerebral larva migrans and demonstrates the alterations of these miRNAs during the migration of larvae from the livers through the lungs and to the brains of infected mice. After filtering unspecific changes in an irrelevant control, T. canis-derived miRNAs and T. canis infection-induced differential miRNAs are predicted to modulate genes consistently involved in mitogen-activated protein kinase (MAPK) signalling and pathways regulating axon guidance and pluripotency of stem in the infected mice with visceral and cerebral larva migrans. For these plasma circulating miRNAs predicted to be involved in host-parasite crosstalk, two murine miRNAs (miR-26b-5p and miR-122-5p) are experimentally verified to be responsive to larva migrans and represent circulating biomarker candidates for visceral and cerebral toxocariasis in BALB/c mice. CONCLUSIONS: Our findings provide novel insights into the crosstalk of T. canis and the mammalian host via plasma circulating miRNAs, and prime agents and indicators for visceral and cerebral larva migrans. A deep understanding of these aspects will underpin the diagnosis and control of toxocariasis in humans and animals.

Occurrence of parasitism promoted by Myzobdella lugubris Leidy, 1851 (Annelida: Piscicolidae) in Callinectes bocourti (Crustacea: Portunidae): A report of invasive leech in Brazilian Amazon province.

This study reports the presence of high parasitic load by Myzobdella lugubris Leidy, 1851 in the swimming crab Callinectes bocourti A. Milne-Edwards, 1879 from Amazon mangrove. We sampled the swimming crabs using a baited trap, between January and June 2023, in Santa Maria River, located in the municipality of Curuçá, state of Pará, Brazil (geographical coordinates 0°40'3.705"S, 047°54'43.405"W). After sampling, each swimming crab was individually placed in plastic containers for the count of leeches per individual. In the laboratory, the specimens were sexed, measured (parasite and host) and fixed in 70% alcohol. For the leech species identification, macroscopic techniques were combined with light microscopy (LM) and scanning electron microscopy (SEM). We examined 86 specimens of C. bocourti (75 males and 11 females) in a ratio of 1 M:0.14 F, all infested with leeches. In total, 186 leech specimens were collected, ranging from 1 to 21 leeches per host. Leeches oviposited the cocoons in greater quantities in ventral area of swimming crab carapace (32%), followed by dorsal area of carapace (29.09%), chelipeds (24.34%) and ambulatory legs (14.57%). The presence of M. lugubris is a risk to the health of the host, once it may transmit a range of diseases to aquatic organisms, and subsequently risk to human health.

Does the body size, sex, and reproductive modes of leaf litter anurans affect the diversity of parasites?

We describe the composition of endoparasites associated with leaf litter anurans from an Atlantic Forest area, in southeastern Brazil. We tested if body size, sex, and reproductive modes of anuran hosts influence endoparasite abundance and richness. We sampled 583 individuals from 11 anuran species and recorded 1,600 helminths from 14 taxa. The helminths that infected the greatest number of anuran host species were the nematodes Cosmocerca parva (8 spp.), Physaloptera sp. (8 spp.), and Cosmocerca brasiliense (7 spp.), and the most abundant helminth species were Physaloptera sp. (14.6%), Cosmocerca brasiliense (13.7%) and Cosmocerca parva (12.6%). Both helminth abundance and richness were positively affected by anuran body size and dependence on water for reproduction. Larger hosts can contain a higher abundance of parasites because they may provide more physical space than smaller ones, or it can simply be a function of age. Besides, parasite species richness can be highly correlated with the amount of time a host spends in association with aquatic habitats, a conservative aspect of both parasite and host natural history. Within host species, there was a positive and significant influence of body size on helminth abundance. Haddadus binotatus females had greater helminth abundance than males, probably due to sex-related differences in behavior and/or in physiology. Our data suggest that reproductive modes could also influence helminth infection parameters in other anuran communities and should be considered in detail in future analyses.

Pleiotropy alleviates the fitness costs associated with resource allocation trade-offs in immune signalling networks.

Many genes and signalling pathways within plant and animal taxa drive the expression of multiple organismal traits. This form of genetic pleiotropy instigates trade-offs among life-history traits if a mutation in the pleiotropic gene improves the fitness contribution of one trait at the expense of another. Whether or not pleiotropy gives rise to conflict among traits, however, likely depends on the resource costs and timing of trait deployment during organismal development. To investigate factors that could influence the evolutionary maintenance of pleiotropy in gene networks, we developed an agent-based model of co-evolution between parasites and hosts. Hosts comprise signalling networks that must faithfully complete a developmental programme while also defending against parasites, and trait signalling networks could be independent or share a pleiotropic component as they evolved to improve host fitness. We found that hosts with independent developmental and immune networks were significantly more fit than hosts with pleiotropic networks when traits were deployed asynchronously during development. When host genotypes directly competed against each other, however, pleiotropic hosts were victorious regardless of trait synchrony because the pleiotropic networks were more robust to parasite manipulation, potentially explaining the abundance of pleiotropy in immune systems despite its contribution to life history trade-offs.

Glucose and trehalose metabolism through the cyclic pentose phosphate pathway shapes pathogen resistance and host protection in Drosophila.

Activation of immune cells requires the remodeling of cell metabolism in order to support immune function. We study these metabolic changes through the infection of Drosophila larvae by parasitoid wasp. The parasitoid egg is neutralized by differentiating lamellocytes, which encapsulate the egg. A melanization cascade is initiated, producing toxic molecules to destroy the egg while the capsule also protects the host from the toxic reaction. We combined transcriptomics and metabolomics, including 13C-labeled glucose and trehalose tracing, as well as genetic manipulation of sugar metabolism to study changes in metabolism, specifically in Drosophila hemocytes. We found that hemocytes increase the expression of several carbohydrate transporters and accordingly uptake more sugar during infection. These carbohydrates are metabolized by increased glycolysis, associated with lactate production, and cyclic pentose phosphate pathway (PPP), in which glucose-6-phosphate is re-oxidized to maximize NADPH yield. Oxidative PPP is required for lamellocyte differentiation and resistance, as is systemic trehalose metabolism. In addition, fully differentiated lamellocytes use a cytoplasmic form of trehalase to cleave trehalose to glucose and fuel cyclic PPP. Intracellular trehalose metabolism is not required for lamellocyte differentiation, but its down-regulation elevates levels of reactive oxygen species, associated with increased resistance and reduced fitness. Our results suggest that sugar metabolism, and specifically cyclic PPP, within immune cells is important not only to fight infection but also to protect the host from its own immune response and for ensuring fitness of the survivor.

How do host population dynamics impact Lyme disease risk dynamics in theoretical models?

Lyme disease is the most common wildlife-to-human transmitted disease reported in North America. The study of this disease requires an understanding of the ecology of the complex communities of ticks and host species involved in harboring and transmitting this disease. Much of the ecology of this system is well understood, such as the life cycle of ticks, and how hosts are able to support tick populations and serve as disease reservoirs, but there is much to be explored about how the population dynamics of different host species and communities impact disease risk to humans. In this study, we construct a stage-structured, empirically-informed model with host dynamics to investigate how host population dynamics can affect disease risk to humans. The model describes a tick population and a simplified community of three host species, where primary nymph host populations are made to fluctuate on an annual basis, as commonly observed in host populations. We tested the model under different environmental conditions to examine the effect of environment on the interactions of host dynamics and disease risk. Results show that allowing for host dynamics in the model reduces mean nymphal infection prevalence and increases the maximum annual prevalence of nymphal infection and the density of infected nymphs. Effects of host dynamics on disease measures of nymphal infection prevalence were nonlinear and patterns in the effect of dynamics on amplitude in nymphal infection prevalence varied across environmental conditions. These results highlight the importance of further study of the effect of community dynamics on disease risk. This will involve the construction of further theoretical models and collection of robust field data to inform these models. With a more complete understanding of disease dynamics we can begin to better determine how to predict and manage disease risk using these models.

Leeches Baicalobdella torquata feed on hemolymph but have a low effect on the cellular immune response of amphipod Eulimnogammarus verrucosus from Lake Baikal.

Lake Baikal is one of the largest and oldest freshwater reservoirs on the planet with a huge endemic diversity of amphipods (Amphipoda, Crustacea). These crustaceans have various symbiotic relationships, including the rarely described phenomenon of leech parasitism on amphipods. It is known that leeches feeding on hemolymph of crustacean hosts can influence their physiology, especially under stressful conditions. Here we show that leeches Baicalobdella torquata (Grube, 1871) found on gills of Eulimnogammarus verrucosus (Gerstfeldt, 1858), one of the most abundant amphipods in the Baikal littoral zone, indeed feed on the hemolymph of their host. However, the leech infection had no effect on immune parameters such as hemocyte concentration or phenoloxidase activity and also did not affect glycogen content. The intensity of hemocyte reaction to foreign bodies in a primary culture was identical between leech-free and leech-infected animals. Artificial infection with leeches also had only a subtle effect on the course of a model microbial infection in terms of hemocyte concentration and composition. Despite we cannot fully exclude deleterious effects of the parasites, our study indicates a low influence of a few leeches on E. verrucosus and shows that leech-infected amphipods can be used at least for some types of ecophysiological experiments.

Associating with kin selects for disease resistance and against tolerance.

Behavioural and physiological resistance are key to slowing epidemic spread. We explore the evolutionary and epidemic consequences of their different costs for the evolution of tolerance that trades off with resistance. Behavioural resistance affects social cohesion, with associated group-level costs, while the cost of physiological resistance accrues only to the individual. Further, resistance, and the associated reduction in transmission, benefit susceptible hosts directly, whereas infected hosts only benefit indirectly, by reducing transmission to kin. We therefore model the coevolution of transmission-reducing resistance expressed in susceptible hosts with resistance expressed in infected hosts, as a function of kin association, and analyse the effect on population-level outcomes. Using parameter values for guppies, Poecilia reticulata, and their gyrodactylid parasites, we find that: (1) either susceptible or infected hosts should invest heavily in resistance, but not both; (2) kin association drives investment in physiological resistance more strongly than in behavioural resistance; and (3) even weak levels of kin association can favour altruistic infected hosts that invest heavily in resistance (versus selfish tolerance), eliminating parasites. Overall, our finding that weak kin association affects the coevolution of infected and susceptible investment in both behavioural and physiological resistance suggests that kin selection may affect disease dynamics across systems.

The interplay of cytokines in bovine tropical theileriosis: a mini review.

Studying cytokine profiling in Theleria annulata infection enhances our understanding of how the immune response unfolds, the intricate interactions between the host and the parasite, the strategies employed by the parasite to evade the immune system, and potential avenues for developing treatments. The generation of pro-inflammatory cytokines plays a pivotal role in the immune response against T. annulata infection. Elevated concentrations of these cytokines potentially contribute to the manifestation of clinical symptoms associated with the disease, such as fever, anemia, exophthalmia, and weight loss. The production of anti-inflammatory cytokines potentially serves as a regulatory mechanism for the immune response, preventing the development of severe disease. Nevertheless, in animals afflicted by T. annulata infection, there is often a notable decrease in the levels of these cytokines, suggesting that they may not be as effective in mitigating the disease as they are in uninfected animals. This knowledge can be harnessed to develop improved diagnostic methods, treatments, and vaccines for tropical theileriosis. The objective of this current mini review is to achieve the same goal by consolidating the available knowledge of cytokine interactions in Bovine Tropical Theileriosis (BTT).

Differential effects of plant-beneficial fungi on the attraction of the egg parasitoid Trissolcus basalis in response to Nezara viridula egg deposition.

There is increasing evidence that plant-associated microorganisms play important roles in defending plants against insect herbivores through both direct and indirect mechanisms. While previous research has shown that these microbes can modify the behaviour and performance of insect herbivores and their natural enemies, little is known about their effect on egg parasitoids which utilize oviposition-induced plant volatiles to locate their hosts. In this study, we investigated how root inoculation of sweet pepper (Capsicum annuum) with the plant-beneficial fungi Beauveria bassiana ARSEF 3097 or Trichoderma harzianum T22 influences the olfactory behaviour of the egg parasitoid Trissolcus basalis following egg deposition by its host Nezara viridula. Olfactometer assays showed that inoculation by T. harzianum significantly enhanced the attraction of the egg parasitoid, while B. bassiana had the opposite effect. However, no variation was observed in the chemical composition of plant volatiles. Additionally, fitness-related traits of the parasitoids (wasp body size) were not altered by any of the two fungi, suggesting that fungal inoculation did not indirectly affect host quality. Altogether, our results indicate that plant inoculation with T. harzianum T22 can be used to enhance attraction of egg parasitoids, which could be a promising strategy in manipulating early plant responses against pest species and improving sustainable crop protection. From a more fundamental point of view, our findings highlight the importance of taking into account the role of microorganisms when studying the intricate interactions between plants, herbivores and their associated egg parasitoids.

Coinfection frequency in water flea populations is a mere reflection of parasite diversity.

In nature, parasite species often coinfect the same host. Yet, it is not clear what drives the natural dynamics of coinfection prevalence. The prevalence of coinfections might be affected by interactions among coinfecting species, or simply derive from parasite diversity. Identifying the relative impact of these parameters is crucial for understanding patterns of coinfections. We studied the occurrence and likelihood of coinfections in natural populations of water fleas (Daphnia magna). Coinfection prevalence was within the bounds expected by chance and parasite diversity had a strong positive effect on the likelihood of coinfections. Additionally, coinfection prevalence increased over the season and became as common as a single infection. Our results demonstrate how patterns of coinfection, and particularly their temporal variation, are affected by overlapping epidemics of different parasites. We suggest that monitoring parasite diversity can help predict where and when coinfection prevalence will be high, potentially leading to increased health risks to their hosts.

A screen for Plasmodium falciparum sporozoite surface protein binding to human hepatocyte surface receptors identifies novel host-pathogen interactions.

BACKGROUND: Sporozoite invasion of hepatocytes is an essential step in the Plasmodium life-cycle and has similarities, at the cellular level, to merozoite invasion of erythrocytes. In the case of the Plasmodium blood-stage, efforts to identify host-pathogen protein-protein interactions have yielded important insights including vaccine candidates. In the case of sporozoite-hepatocyte invasion, the host-pathogen protein-protein interactions involved are poorly understood. METHODS: To gain a better understanding of the protein-protein interaction between the sporozoite ligands and host receptors, a systematic screen was performed. The previous Plasmodium falciparum and human surface protein ectodomain libraries were substantially extended, resulting in the creation of new libraries comprising 88 P. falciparum sporozoite protein coding sequences and 182 sequences encoding human hepatocyte surface proteins. Having expressed recombinant proteins from these sequences, a plate-based assay was used, capable of detecting low affinity interactions between recombinant proteins, modified for enhanced throughput, to screen the proteins for interactions. The novel interactions identified in the screen were characterized biochemically, and their essential role in parasite invasion was further elucidated using antibodies and genetically manipulated Plasmodium parasites. RESULTS: A total of 7540 sporozoite-hepatocyte protein pairs were tested under conditions capable of detecting interactions of at least 1.2 µM KD. An interaction between the human fibroblast growth factor receptor 4 (FGFR4) and the P. falciparum protein Pf34 is identified and reported here, characterizing its affinity and demonstrating the blockade of the interaction by reagents, including a monoclonal antibody. Furthermore, further interactions between Pf34 and a second P. falciparum rhoptry neck protein, PfRON6, and between human low-density lipoprotein receptor (LDLR) and the P. falciparum protein PIESP15 are identified. Conditional genetic deletion confirmed the essentiality of PfRON6 in the blood-stage, consistent with the important role of this protein in parasite lifecycle. Pf34 was refractory to attempted genetic modification. Antibodies to Pf34 abrogated the interaction and had a modest effect upon sporozoite invasion into primary human hepatocytes. CONCLUSION: Pf34 and PfRON6 may be members of a functionally important invasion complex which could be a target for future interventions. The modified interaction screening assay, protein expression libraries and P. falciparum mutant parasites reported here may be a useful tool for protein interaction discovery and antigen candidate screening which could be of wider value to the scientific community.

Quantitative phosphoproteomic analysis of chicken DF-1 cells infected with Eimeria tenella, using tandem mass tag (TMT) and parallel reaction monitoring (PRM) mass spectrometry.

Eimeria tenella is an obligate intracellular parasite which causes great harm to the poultry breeding industry. Protein phosphorylation plays a vital role in host cell-E. tenella interactions. However, no comprehensive phosphoproteomic analyses of host cells at various phases of E. tenella infection have been published. In this study, quantitative phosphoproteomic analysis of chicken embryo DF-1 fibroblasts that were uninfected (UI) or infected with E. tenella for 6 h (PI6, the early invasion phase) or 36 h (PI36, the trophozoite development phase) was conducted. A total of 10,122 phosphopeptides matched to 3,398 host cell phosphoproteins were identified and 13,437 phosphorylation sites were identified. Of these, 491, 1,253, and 275 differentially expressed phosphorylated proteins were identified in the PI6/UI, PI36/UI, and PI36/PI6 comparisons, respectively. KEGG pathway enrichment analysis showed that E. tenella modulated host cell processes through phosphorylation, including focal adhesion, regulation of the actin cytoskeleton, and FoxO signaling to support its early invasion phase, and modulating adherens junctions and the ErbB signaling pathway to favor its trophozoite development. These results enrich the data on the interaction between E. tenella and host cells and facilitate a better understanding of the molecular mechanisms underlying host-parasite relationships.

Title: Analyse phosphoprotéomique quantitative de cellules DF-1 de poulet infectées par Eimeria tenella, par spectrométrie de masse avec marqueur de masse en tandem (TMT) et surveillance des réactions parallèles (PRM). Abstract: Eimeria tenella est un parasite intracellulaire obligatoire qui cause de graves dommages à l'industrie de l'élevage de volailles. La phosphorylation des protéines joue un rôle essentiel dans les interactions entre la cellule hôte et E. tenella. Cependant, aucune analyse phosphoprotéomique complète des cellules hôtes à différentes phases de l'infection par E. tenella n'a été publiée. Dans cette étude, une analyse phosphoprotéomique quantitative de fibroblastes DF-1 d'embryon de poulet non infectés (NI) ou infectés par E. tenella pendant 6 h (PI6, la phase d'invasion précoce) ou 36 h (PI36, la phase de développement des trophozoïtes) a été réalisée. Un total de 10 122 phosphopeptides correspondant à 3 398 phosphoprotéines de cellules hôtes ont été identifiés et 13 437 sites de phosphorylation ont été identifiés. Parmi celles-ci, 491, 1 253 et 275 protéines différentiellement phosphorylées exprimées ont été identifiées respectivement dans les comparaisons PI6/NI, PI36/NI et PI36/PI6. L'analyse d'enrichissement de la voie KEGG a montré qu'E. tenella modulait les processus de la cellule hôte par phosphorylation, y compris l'adhésion focale, la régulation du cytosquelette d'actine et la signalisation FoxO, pour aider sa phase d'invasion précoce, et la modulation des jonctions adhérentes et de la voie de signalisation ErbB pour favoriser le développement de son trophozoïte. Ces résultats enrichissent les données sur l'interaction entre E. tenella et les cellules hôtes et facilitent une meilleure compréhension des mécanismes moléculaires sous-jacents aux relations hôtes­parasites.