Dynamics Of Host-pathogen Interactions Research Articles

Field Screening of tomato breeding lines for improved resistance against Tomato Yellow Leaf Curl Virus (TYLCV)

The tomato represents an extensively cultivated crop within tropical and subtropical regions of the world for their fresh market and processing attribute. However, its production frequently encounters substantial setbacks due to notable losses associated with diseases such as Tomato Yellow Leaf Curl Virus (TyLCV). To address this challenge, the current study aimed to assess the resistance or susceptibility of selected 25 tomato breeding lines for TyLCV under natural field screenings to mimic real-world scenarios in accordance with the disease reaction score of Banerjee and Kalloo (1987). The field screening results showed that, the check Arka Vishes line demonstrated high resistance (HR) to TLCV, with reduced PDS, PDI values and a low coefficient of infection (CI). Several lines, including CBE SL 101, CBE SL 105, CBE SL 108, CBE SL 110, and CBE SL 114, exhibited a resistant (R) reaction, while others, such as CBE SL 102, CBE SL 107, CBE SL 112, CBE SL 120, and Arka Rakshak, displayed moderate resistance (MR). Conversely, lines CBE SL 103, CBE SL 104, CBE SL 106, CBE SL 109, CBE SL 111, CBE SL 115, CBE SL 117, and CBE SL 123 showed moderate susceptibility (MS), and the remaining lines, namely CBE SL 113, CBE SL 116, CBE SL 118, CBE SL 119, CBE SL 121, and CBE SL 122, were deemed susceptible to TLCV. The varying disease responses observed across these lines provide valuable insights into the complex dynamics of host-pathogen interactions in tomato plants, informing strategies for disease management and breeding efforts aimed at enhancing resistance to TLCV.

Agent-based model predicts that layered structure and 3D movement work synergistically to reduce bacterial load in 3D in vitro models of tuberculosis granuloma.

Tuberculosis (TB) remains a global public health threat. Understanding the dynamics of host-pathogen interactions within TB granulomas will assist in identifying what leads to the successful elimination of infection. In vitro TB models provide a controllable environment to study these granuloma dynamics. Previously we developed a biomimetic 3D spheroid granuloma model that controls bacteria better than a traditional monolayer culture counterpart. We used agent-based simulations to predict the mechanistic reason for this difference. Our calibrated simulations were able to predict heterogeneous bacterial dynamics that are consistent with experimental data. In one group of simulations, spheroids are found to have higher macrophage activation than their traditional counterparts, leading to better bacterial control. This higher macrophage activation in the spheroids was not due to higher counts of activated T cells, instead fewer activated T cells were able to activate more macrophages due to the proximity of these cells to each other within the spheroid. In a second group of simulations, spheroids again have more macrophage activation but also more T cell activation, specifically CD8+ T cells. This higher level of CD8+ T cell activation is predicted to be due to the proximity of these cells to the cells that activate them. Multiple mechanisms of control were predicted. Simulations removing individual mechanisms show that one group of simulations has a CD4+ T cell dominant response, while the other has a mixed/CD8+ T cell dominant response. Lastly, we demonstrated that in spheroids the initial structure and movement rules work synergistically to reduce bacterial load. These findings provide valuable insights into how the structural complexity of in vitro models impacts immune responses. Moreover, our study has implications for engineering more physiologically relevant in vitro models and advancing our understanding of TB pathogenesis and potential therapeutic interventions.

An overview of next generation sequencing strategies and genomics tools used for tuberculosis research.

Tuberculosis (TB) is a grave public health concern and is considered the foremost contributor to human mortality resulting from infectious disease. Due to the stringent clonality and extremely restricted genomic diversity, conventional methods prove inefficient for in-depth exploration of minor genomic variations and the evolutionary dynamics operating in Mycobacterium tuberculosis (M.tb) populations. Until now, the majority of reviews have primarily focused on delineating the application of whole-genome sequencing (WGS) in predicting antibiotic resistant genes, surveillance of drug resistance strains, and M.tb lineage classifications. Despite the growing use of next generation sequencing (NGS) and WGS analysis in TB research, there are limited studies that provide a comprehensive summary of there role in studying macroevolution, minor genetic variations, assessing mixed TB infections, and tracking transmission networks at an individual level. This highlights the need for systematic effort to fully explore the potential of WGS and its associated tools in advancing our understanding of TB epidemiology and disease transmission. We delve into the recent bioinformatics pipelines and NGS strategies that leverage various genetic features and simultaneous exploration of host-pathogen protein expression profile to decipher the genetic heterogeneity and host-pathogen interaction dynamics of the M.tb infections. This review highlights the potential benefits and limitations of NGS and bioinformatics tools and discusses their role in TB detection and epidemiology. Overall, this review could be a valuable resource for researchers and clinicians interested in NGS-based approaches in TB research.

High burden of viruses and bacterial pathobionts drives heightened nasal innate immunity in children.

Studies during the COVID-19 pandemic showed that children had heightened nasal innate immune responses compared with adults. To evaluate the role of nasal viruses and bacteria in driving these responses, we performed cytokine profiling and comprehensive, symptom-agnostic testing for respiratory viruses and bacterial pathobionts in nasopharyngeal samples from children tested for SARS-CoV-2 in 2021-22 (n = 467). Respiratory viruses and/or pathobionts were highly prevalent (82% of symptomatic and 30% asymptomatic children; 90 and 49% for children <5 years). Virus detection and load correlated with the nasal interferon response biomarker CXCL10, and the previously reported discrepancy between SARS-CoV-2 viral load and nasal interferon response was explained by viral coinfections. Bacterial pathobionts correlated with a distinct proinflammatory response with elevated IL-1β and TNF but not CXCL10. Furthermore, paired samples from healthy 1-year-olds collected 1-2 wk apart revealed frequent respiratory virus acquisition or clearance, with mucosal immunophenotype changing in parallel. These findings reveal that frequent, dynamic host-pathogen interactions drive nasal innate immune activation in children.

Iron mobilization from intact ferritin: effect of differential redox activity of quinone derivatives with NADH/O2 and in situ-generated ROS.

Ferritins are multimeric nanocage proteins that sequester/concentrate excess of free iron and catalytically synthesize a hydrated ferric oxyhydroxide bio-mineral. Besides functioning as the primary intracellular iron storehouses, these supramolecular assemblies also oversee the controlled release of iron to meet physiologic demands. By virtue of the reducing nature of the cytosol, reductive dissolution of ferritin-iron bio-mineral by physiologic reducing agents might be a probable pathway operating in vivo. Herein, to explore this reductive iron-release pathway, a series of quinone analogs differing in size, position/nature of substituents and redox potentials were employed to relay electrons from physiologic reducing agent, NADH, to the ferritin core. Quinones are well known natural electron/proton mediators capable of facilitating both 1/2 electron transfer processes and have been implicated in iron/nutrient acquisition in plants and energy transduction. Our findings on the structure-reactivity of quinone mediators highlight that iron release from ferritin is dictated by electron-relay capability (dependent on E1/2 values) of quinones, their molecular structure (i.e., the presence of iron-chelation sites and the propensity for H-bonding) and the type/amount of reactive oxygen species (ROS) they generate in situ. Juglone/Plumbagin released maximum iron due to their intermediate E1/2 values, presence of iron chelation sites, the ability to inhibit in situ generation of H2O2 and form intramolecular H-bonding (possibly promotes semiquinone formation). This study may strengthen our understanding of the ferritin-iron-release process and their significance in bioenergetics/O2-based cellular metabolism/toxicity while providing insights on microbial/plant iron acquisition and the dynamic host-pathogen interactions.

Establishment of a cobia (Rachycentron canadum) gill cell line: A valuable tool for immune response studies

Cobia (Rachycentron canadum), a commercially important marine fish, has been used to develop a novel gill cell line, designated CG, for the first time. The CG cell line was cultured in Leibovitz's-15 medium with 5% fetal bovine serum (FBS) and successfully sub-cultured more than 110 passages. It underwent verification through sequencing of the mitochondrial cytochrome C oxidase subunit I (COI) gene. Optimal growth rate was achieved when the CG cell line was cultured in a medium supplemented with 5% FBS, 1% Penicillin-Streptomycin (P/S), and 5 parts per thousand (ppt) of coral sea salt water, maintained at a temperature of 27 °C. The addition of 5 ppt of salt in the growth medium suggests that this cell line could be a viable in vitro tool for marine ecosystem toxicological studies or for culturing marine parasitic microorganisms. The CG cell line was also successfully transfected using the pTurbo-GFP plasmids, showing an 18% efficiency, with observable GFP expression. Furthermore, the cell line has been effectively cryopreserved. Gene expression analysis indicated that the CG cell line exhibits responsive regulation of immune gene expression when exposured to various stimulants, highlighting its potential as an in vitro platform for immune response studies. This makes it suitable for exploring dynamic immune signaling pathways and host-pathogen interactions, thereby offering valuable insights for therapeutic development.

Tuberculosis infection and hypertension: prevalence estimates from the US National Health and Nutrition Examination Survey

ObjectivesTuberculosis infection (TBI) is marked by dynamic host–pathogen interactions with persistent low-grade inflammation and is associated with increased risk of cardiovascular diseases (CVD) including acute coronary syndrome, myocardial infarction and...

Hysteresis and Hopf bifurcation: Deciphering the dynamics of an in-host model of SARS-CoV-2 with logistic target cell growth and sigmoidal immune response

Mathematical models of in-host dynamics of SARS-CoV-2 may reveal the intricate underlying dynamics of host-pathogen interaction and guide crucial steps to curtail progression of COVID-19 and other similar infectious diseases. While the existing models on SARS-CoV-2 have considered a wide range of host-pathogen interactions, at their core, these models are remarkably similar, particularly in the choice of mathematical functions used in modeling the interactions. Specifically, these models have employed mass action kinetics while modeling target-cell interaction with virus particles and immune response to virus, thus overlooking the role of saturated evolution of target epithelial cells as well as immune cells. Here we fill this gap by developing a more comprehensive model of in-host dynamics of SARS-CoV-2 that concurrently models target epithelial cell growth using a logistic equation and virus-immune interaction using Michaelis–Menten kinetics. We identify a feasible disease-free equilibrium whose local stability depends on ”reproduction number” and global stability on the replenishment rate as well as the removal rate of immune cells. We also obtain multiple endemic equilibria and perform their local and global stability analysis. Our detailed numerical investigation demonstrates that the infection rate and reproduction number govern several interesting dynamical behaviors such as forward bifurcation with and without hysteresis, Hopf bifurcation, and multiple endemic equilibria. To analyze the impact of parameters on the model system and disease dynamics, we investigate several sensitive parameters and compute their sensitivity indices. Finally, to understand the impact of anti-viral therapy on viral load, we identify a novel threshold of replication rate that must be crossed to enable virus proliferation. Our results thus provide novel insights into the in-host dynamics of SARS-CoV-2 and we expect this model will help in the development of better treatment strategies for COVID-19 and other such infectious diseases.

Untangling Cellular Host-Pathogen Encounters at Infection Bottlenecks.

Bacterial pathogens can invade the tissue and establish a protected intracellular niche at the site of invasion that can spread locally (e.g., microcolonies) or to systemic sites (e.g., granulomas). Invasion of the tissue and establishment of intracellular infection are rare events that are difficult to study in the in vivo setting but have critical clinical consequences, such as long-term carriage, reinfections, and emergence of antibiotic resistance. Here, I discuss Salmonella interactions with its host macrophage during early stages of infection and their critical role in determining infection outcome. The dynamics of host-pathogen interactions entail highly heterogenous host immunity, bacterial virulence, and metabolic cross talk, requiring in vivo analysis at single-cell resolution. I discuss models and single-cell approaches that provide a global understanding of the establishment of a protected intracellular niche within the tissue and the host-pathogen landscape at infection bottlenecks during early stages of infection. Studying cellular host-pathogen interactions in vivo can improve our knowledge of the trajectory of infection between the initial inoculation with a dose of pathogens and the appearance of symptoms of disease.

Manipulation of microvillar proteins during Salmonella enterica invasion results in brush border effacement and actin remodeling.

Enterocyte invasion by the gastrointestinal pathogen Salmonella enterica is accompanied by loss of brush border and massive remodeling of the actin cytoskeleton, leading to microvilli effacement and formation of membrane ruffles. These manipulations are mediated by effector proteins translocated by the Salmonella Pathogenicity Island 1-encoded type III secretion system (SPI1-T3SS). To unravel the mechanisms of microvilli effacement and contribution of SPI1-T3SS effector proteins, the dynamics of host-pathogen interactions was analyzed using live cell imaging (LCI) of polarized epithelial cells (PEC) expressing LifeAct-GFP. PEC were infected with S. enterica wild-type and mutant strains with defined defects in SPI1-T3SS effector proteins, and pharmacological inhibition of actin assembly were applied. We identified that microvilli effacement involves two distinct mechanisms: i) F-actin depolymerization mediated by villin and ii), the consumption of cytoplasmic G-actin by formation of membrane ruffles. By analyzing the contribution of individual SPI1-T3SS effector proteins, we demonstrate that SopE dominantly triggers microvilli effacement and formation of membrane ruffles. Furthermore, SopE via Rac1 indirectly manipulates villin, which culminates in F-actin depolymerization. Collectively, these results indicate that SopE has dual functions during F-actin remodeling in PEC. While SopE-Rac1 triggers F-actin polymerization and ruffle formation, activation of PLCγ and villin by SopE depolymerizes F-actin in PEC. These results demonstrate the key role of SopE in destruction of the intestinal barrier during intestinal infection by Salmonella.

Quantitative Phosphoproteome Analysis of the Interaction Between Fusarium graminearum and Triticum aestivum.

Quantitative proteomics is a powerful method for distinguishing protein abundance changes in a biological system across conditions. In addition to recent advances in computational power and bioinformatics methods, improvements to sensitivity and resolution of mass spectrometry (MS) instrumentation provide an innovative approach for studying host-pathogen interaction dynamics and posttranslational modifications. In this protocol, we provide a workflow for state-of-the-art MS-based proteomics to assess changes in phosphorylated protein abundance upon interaction between the worldwide cereal crop, Triticum aestivum (wheat), and the global cereal crop fungal pathogen, Fusarium graminearum, during infection. This protocol mimics a time course of infection of T. aestivum by F. graminearum in the greenhouse, and the harvested samples undergo Fe-NTA phosphoenrichment combined with label-free quantification (LFQ) for detection by liquid-chromatography (LC)-coupled with tandem MS/MS. Our approach provides an in-depth view of changes in phosphorylation from both the host and pathogen perspectives in a single experiment across infection time points and different host cultivars.

Listeria motility increases the efficiency of epithelial invasion during intestinal infection.

Listeria monocytogenes (Lm) is a food-borne pathogen that causes severe bacterial gastroenteritis, with high rates of hospitalization and mortality. Lm is ubiquitous in soil, water and livestock, and can survive and proliferate at low temperatures. Following oral ingestion of contaminated food, Lm crosses the epithelium through intestinal goblet cells in a mechanism mediated by Lm InlA binding host E-cadherin. Importantly, human infections typically occur with Lm growing at or below room temperature, which is flagellated and motile. Even though many important human bacterial pathogens are flagellated, little is known regarding the effect of Lm motility on invasion and immune evasion. Here, we used complementary imaging and computer modeling approaches to test the hypothesis that bacterial motility helps Lm locate and engage target cells permissive for invasion. Imaging explanted mouse and human intestine, we showed that Lm grown at room temperature uses motility to scan the epithelial surface and preferentially attach to target cells. Furthermore, we integrated quantitative parameters from our imaging experiments to construct a versatile "layered" cellular Potts model (L-CPM) that simulates host-pathogen dynamics. Simulated data are consistent with the hypothesis that bacterial motility enhances invasion by allowing bacteria to search the epithelial surface for their preferred invasion targets. Indeed, our model consistently predicts that motile bacteria invade twice as efficiently over the first hour of infection. We also examined how bacterial motility affected interactions with host cellular immunity. In a mouse model of persistent infection, we found that neutrophils migrated to the apical surface of the epithelium 5 hours post infection and interacted with Lm. Yet in contrast to the view that neutrophils "hunt" for bacteria, we found that these interactions were driven by motility of Lm-which moved at least ~50x faster than neutrophils. Furthermore, our L-CPM predicts that motile bacteria maintain their invasion advantage even in the presence of host phagocytes, with the balance between invasion and phagocytosis governed almost entirely by bacterial motility. In conclusion, our simulations provide insight into host pathogen interaction dynamics at the intestinal epithelial barrier early during infection.

DRNASb: a systems biology approach to decipher dynamics of host-pathogen interactions using temporal dual RNA-seq data.

Infection triggers a dynamic cascade of reciprocal events between host and pathogen wherein the host activates complex mechanisms to recognise and kill pathogens while the pathogen often adjusts its virulence and fitness to avoid eradication by the host. The interaction between the pathogen and the host results in large-scale changes in gene expression in both organisms. Dual RNA-seq, the simultaneous detection of host and pathogen transcripts, has become a leading approach to unravelling complex molecular interactions between the host and the pathogen and is particularly informative for intracellular organisms. The amount of in vitro and in vivo dual RNA-seq data is rapidly growing, which demands computational pipelines to effectively analyse such data. In particular, holistic, systems-level, and temporal analyses of dual RNA-seq data are essential to enable further insights into the host-pathogen transcriptional dynamics and potential interactions. Here, we developed an integrative network-driven bioinformatics pipeline, dRNASb, a systems biology-based computational pipeline to analyse temporal transcriptional clusters, incorporate molecular interaction networks (e.g. protein-protein interactions), identify topologically and functionally key transcripts in host and pathogen, and associate host and pathogen temporal transcriptome to decipher potential between-species interactions. The pipeline is applicable to various dual RNA-seq data from different species and experimental conditions. As a case study, we applied dRNASb to analyse temporal dual RNA-seq data of Salmonella-infected human cells, which enabled us to uncover genes contributing to the infection process and their potential functions and to identify putative associations between host and pathogen genes during infection. Overall, dRNASb has the potential to identify key genes involved in bacterial growth or host defence mechanisms for future uses as therapeutic targets.

Coevolutionary dynamics of host-pathogen interaction with density-dependent mortality.

This study explores the coevolutionary dynamics of host-pathogen interaction based on a susceptible-infected population model with density-dependent mortality. We assume that both the host’s resistance and the pathogen’s virulence will adaptively evolve, but there are inevitable costs in terms of host birth rate and disease-related mortality rate. Particularly, it is assumed that both the host resistance and pathogen virulence can affect the transmission rate. By using the approach of adaptive dynamics and numerical simulation, we find that the finally coevolutionary outcome depends on the strength of host-pathogen asymmetric interaction, the curvature of trade-off functions, and the intensity of density-dependent natural mortality. To be specific, firstly, we find that if the strengths of host-pathogen asymmetric interaction and disease-related mortality are relatively weak, or the density-dependent natural mortality is relatively strong, then the host resistance and pathogen virulence will evolve to a continuously stable strategy. However, if the strength of host-pathogen asymmetric interaction and disease-related mortality becomes stronger, then the host resistance and pathogen virulence will evolve periodically. Secondly, we find that if the intensities of both the birth rate trade-off function and the density-dependent natural mortality are relatively weak, but the strength of host-pathogen asymmetric interaction becomes relatively strong, then the evolution of host resistance will have a relatively strongly accelerating benefit, the evolutionary branching of host resistance will first arise. However, if the strength of host-pathogen asymmetric interaction is relatively weak, but the intensity of the trade-off function of disease-related mortality becomes relatively strong, then the evolution of pathogen virulence will have a relatively strongly decelerating cost, and the evolutionary branching of pathogen virulence will first arise. Thirdly, after the evolutionary branching of host resistance and pathogen virulence, we further study the coevolutionary dynamics of two-hosts-one-pathogen interaction and one-host-two-pathogens interaction. We find that if the evolutionary branching of host resistance arises firstly, then the finally evolutionary outcome contains a dimorphic host and a monomorphic pathogen population. If the evolutionary branching of pathogen virulence arises firstly, then the finally evolutionary outcome may contain a monomorphic host and a dimorphic pathogen population.

The relationship between pathogen life-history traits and metapopulation dynamics.

Summary Plant pathogen traits, such as transmission mode and overwintering strategy, may have important effects on dispersal and persistence, and drive disease dynamics. Still, we lack insights into how life‐history traits influence spatiotemporal disease dynamics.We adopted a multifaceted approach, combining experimental assays, theory and field surveys, to investigate whether information about two pathogen life‐history traits – infectivity and overwintering strategy – can predict pathogen metapopulation dynamics in natural systems. For this, we focused on four fungal pathogens (two rust fungi, one chytrid fungus and one smut fungus) on the forest herb Anemone nemorosa.Pathogens infecting new plants mostly via spores (the chytrid and smut fungi) had higher patch occupancies and colonization rates than pathogens causing mainly systemic infections and overwintering in the rhizomes (the two rust fungi). Although the rust fungi more often occupied well‐connected plant patches, the chytrid and smut fungi were equally or more common in isolated patches. Host patch size was positively related to patch occupancy and colonization rates for all pathogens.Predicting disease dynamics is crucial for understanding the ecological and evolutionary dynamics of host–pathogen interactions, and to prevent disease outbreaks. Our study shows that combining experiments, theory and field observations is a useful way to predict disease dynamics.

Do contrasting patterns of migration movements and disease outbreaks between congeneric waterfowl species reflect differing immunity?

Long-distance migrations influence the dynamics of hostpathogen interactions and understanding the role of migratory waterfowl in the spread of the highly pathogenic avian influenza viruses (HPAIV) is important. While wild geese have been associated with outbreak events, disease ecology of closely related species has not been studied to the same extent. The swan goose (Anser cygnoides) and the bar-headed goose (Anser indicus) are congeneric species with distinctly different HPAIV infection records; the former with few and the latter with numerous records. We compared movements of these species, as well as the more distantly related whooper swan (Cygnus cygnus) through their annual migratory cycle to better understand exposure to HPAIV events and how this compares within and between congeneric and noncongeneric species. In spite of their record of fewer infections, swan geese were more likely to come in contact with disease outbreaks than bar-headed geese. We propose two possible explanations: i) frequent prolonged contact with domestic ducks increases innate immunity in swan geese, and/or ii) the stress of high-elevation migration reduces immunity of bar-headed geese. Continued efforts to improve our understanding of species-level pathogen response is critical to assessing disease transmission risk.

Profiling of alternative polyadenylation and gene expression in PEDV-infected IPEC-J2 cells.

Since 2010, porcine epidemic diarrhea virus (PEDV) has received global attention with the emergence of variant strains characterized with high pathogenicity. The pathogen–host interaction after PEDV infection is still unclear. To investigate this issue, high-throughput-based sequencing technology is one of the optimal choices. In this study, we used in vitro transcription sequencing alternative polyadenylation sites (IVT-SAPAS) method, which allowed accurate profiling of gene expression and alternative polyadenylation (APA) sites to profile APA switching genes and differentially expressed genes (DEGs) in IPEC-J2 cells during PEDV variant strain infection. We found 804 APA switching genes, including switching in tandem 3′ UTRs and switching between coding region and 3′ UTR, and 1,677 DEGs in host after PEDV challenge. These genes participated in variety of biological processes such as cellular process, metabolism and immunity reactions. Moreover, 413 genes, most of which are the “focus” genes in interaction networks, were found to be involved in both APA switching genes and DEGs, suggesting these genes were synchronously regulated by different mechanisms. In summary, our results gave a relatively comprehensive insight into dynamic host–pathogen interactions in the regulation of host gene transcripts during PEDV infection.Supplementary InformationThe online version of this article (10.1007/s11262-020-01817-6) contains supplementary material, which is available to authorized users.

Host-pathogen interaction in sugarcane and red rot pathogen: exploring expression of phytoalexin biosynthesis pathway genes

Sugarcane crop, the major source of sugar is a high value commercial crop. The importance of the crop is growing as it has the potential to boost the green fuel production and various other eco-friendly products. The fungal disease, red rot (Colletotrichum falcatum) is a dreadful one and studying the dynamics of host-pathogen interaction is essential to develop disease resistant varieties. Earlier, the role of 3-deoxyanthocyanidin phytoalexins in red rot resistance was established. Further studies were made to assess antifungal activities of these compounds against C. falcatum through in vitro assays. Since phenyl propanoid biosynthesis pathway is the major secondary metabolite producing pathway which leads to production of flavonoids, isoflavonoids and lignin, studies were made to explore expression dynamics in major gene transcripts involved in anthocyanidin pathway by qRT-PCR. Our studies showed antifungal nature of the sugarcane phytoalexins 3-deoxy anthocyanidin compounds, apigeninidin and luteolinidin along with differential expression of transcripts involved in the phytoalexin biosynthesis pathway during compatible and incompatible interactions.

A pathway to cure chronic infection with Toxoplasma gondii through immunological intervention.

Toxoplasma gondii, an obligate intracellular protozoan parasite, can establish a chronic infection in the brain by forming tissue cysts. This chronic infection is widespread in humans worldwide including developed countries, with up to one third of the population being estimated to be infected with this parasite. Diagnosis of this chronic infection is usually conducted by serological detection of IgG antibodies against this parasite. Since infected individuals remain positive for these antibodies for years, it has generally been considered that this infection is a lifelong infection. It is also often considered that this chronic infection is "latent" or "quiescent". However, recent discovery of the capability of perforin-dependent, CD8+ T cell-mediated immune responses to eliminate T. gondii cysts in collaboration with phagocytes illustrated dynamic interplays between T. gondii cysts and host immune system during this chronic infection. Importantly, the cytotoxic T cell-mediated protective immunity is able to remove mature cysts of the parasite. It is now clear that chronic T. gondii infection is not "latent" or "quiescent". Elucidating the mechanisms of the dynamic host-pathogen interactions between the anti-cyst protective immunity and T. gondii cysts and identifying the pathway to appropriately activate anti-cyst CD8+ cytotoxic T cells would be able to open a door for eradicating T. gondii cysts and curing chronic infection with this parasite.

Host-induced spermidine production in motile Pseudomonas aeruginosa triggers phagocytic uptake.

Exploring the complexity of host-pathogen communication is vital to understand why microbes persist within a host, while others are cleared. Here, we employed a dual-sequencing approach to unravel conversational turn-taking of dynamic host-pathogen communications. We demonstrate that upon hitting a host cell, motile Pseudomonas aeruginosa induce a specific gene expression program. This results in the expression of spermidine on the surface, which specifically activates the PIP3-pathway to induce phagocytic uptake into primary or immortalized murine cells. Non-motile bacteria are more immunogenic due to a lower expression of arnT upon host-cell contact, but do not produce spermidine and are phagocytosed less. We demonstrate that not only the presence of pathogen inherent molecular patterns induces immune responses, but that bacterial motility is linked to a host-cell-induced expression of additional immune modulators. Our results emphasize on the value of integrating microbiological and immunological findings to unravel complex and dynamic host-pathogen interactions.