Host Pathogen Research Articles

Plant cell wall structure and dynamics in plant-pathogen interactions and pathogen defence.

Plant cell walls delimit plant cells from their environment and provide mechanical stability to withstand internal turgor pressure as well as external influences. Environmental factors can be beneficial or harmful for the plants and vary substantially depending on prevailing combinations of climate conditions and stress exposure. Consequently, the physicochemical properties of plant cell walls need to be adaptive, and their functional integrity needs to be monitored by the plant. One major threat to plants is posed by phytopathogens, which employ a diversity of infection strategies and lifestyles to colonise host tissues. During these interactions, the plant cell wall represents a barrier that impedes the colonisation of host tissues and pathogen spread. In a tussle over maintenance and breakdown, plant cell walls can be rapidly and efficiently remodelled by enzymatic activities of plant and pathogen origin, heavily influencing the outcome of plant-pathogen interactions. We review the role of locally and systemically induced cell wall remodelling and the importance of tissue-dependent cell wall properties for the interaction with pathogens. Furthermore, we discuss the importance of cell wall-dependent signalling for defence response induction and the influence of abiotic factors on cell wall integrity and cell wall-associated pathogen resistance mechanisms.

The chosen few: Mycobacterium tuberculosis isolates for IMPAc-TB

The three programs that make up the Immune Mechanisms of Protection Against Mycobacterium tuberculosis Centers (IMPAc-TB) had to prioritize and select strains to be leveraged for this work. The CASCADE team based at Seattle Children’s Research Institute are leveraging M.tb H37Rv, M.tb CDC1551, and M.tb SA161. The HI-IMPACT team based at Harvard T.H. Chan School of Public Health, Boston, have selected M.tb Erdman as well as a novel clinical isolate recently characterized during a longitudinal study in Peru. The PHOENIX team also based at Seattle Children’s Research Institute have selected M.tb HN878 and M.tb Erdman as their isolates of choice. Here, we describe original source isolation, genomic references, key virulence characteristics, and relevant tools that make these isolates attractive for use. The global context for M.tb lineage 2 and 4 selection is reviewed including what is known about their relative abundance and acquisition of drug resistance. Host–pathogen interactions seem driven by genomic differences on each side, and these play an important role in pathogenesis and immunity. The few M.tb strains chosen for this work do not reflect the vast genomic diversity within this species. They do, however, provide specific virulence, pathology, and growth kinetics of interest to the consortium. The strains selected should not be considered as “representative” of the growing available array of M.tb isolates, but rather tools that are being used to address key outstanding questions in the field.

Strategic genetic insights and integrated approaches for successful management of blackleg in canola/rapeseed farming

AbstractThis review describes a triumphant narrative in the battle against the devastating plant pathogen complex, Leptosphaeria maculans and L. biglobosa, and the success of the world's second‐largest oilseed crop, canola/oilseed rape. Emphasizing global collaborations, the article explores successfully mitigating this destructive disease in canola/rapeseed production across Australia, Canada and Europe. It highlights how strategies may vary between continents to adapt to specific contexts. While initial resistance (R) genes proved effective, the evolution of the pathogen under crop‐induced disease pressure led to the breakdown of these genes. Now, growers in these regions have been equipped with new tools, allowing them to make informed decisions that help to keep the disease at generally low levels. A pivotal factor in this success has been a deepened understanding of the intricate science underlying the host–pathogen interaction. Concerted efforts of individual laboratories and collaborative initiatives have played an essential role in this success, including novel methods for disease control based on extensive research that has translated into developing highly resistant varieties, enhanced pathogen monitoring, improved cultivar recommendation and integrated management strategies. The review showcases many milestone advancements, including the cloning of numerous avirulence genes within the pathogen, characterization of specific R genes, the development of various molecular tools for monitoring both pathogen and host, the introduction of groundbreaking disease management strategies such as R gene labelling, rotation and stacking, and establishment of a universal pathogen isolate collection that facilitates the exchange of information among multiple laboratories and adds a new dimension to this triumph.

Characterization of NFDQ1 in Cryptosporidium parvum

BackgroundCryptosporidium spp. are important zoonotic parasites that can cause moderate to severe diarrhea in humans and animals. Among the three Cryptosporidium species infecting the intestines of calves, Cryptosporidium parvum has a broad host range and causes severe diarrhea in calves, while Cryptosporidium bovis and Cryptosporidium ryanae mainly infect calves without obvious clinical symptoms. Comparative genomic analysis revealed differences in the copy number of genes encoding the nonfinancial disclosure quality (NFDQ) secretory protein family among the three species, suggesting that this protein family may be associated with the host range or pathogenicity of Cryptosporidium spp. To understand the function of cgd8_10 encoded NFDQ1, tagged and knockout strains were constructed and characterized in this study.MethodsTo determine the localization of NFDQ1, we used clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) technology to tag the C-terminus of NFDQ1 with three hemagglutinin epitopes (3 × HA). The tagged strain was constructed, and the genomic insertion was confirmed by polymerase chain reaction (PCR). Immunofluorescence assays were performed to observe the localization of NFDQ1 both in extracellular sporozoites and at various intracellular developmental stages. Immunoelectron microscopy was used to study the ultrastructural localization of NFDQ1. Then, the ΔNFDQ1 strain was generated by CRISPR/Cas9 and the in vitro growth assay on HCT-8 cells was used to analyze of phenotypic changes after knockout NFDQ1 in parasites.ResultsThe NFDQ1 tagging and knockout stains were successfully constructed by CRISPR/Cas9 technology and the insertions of transgenic strains were validated by PCR. The expression of NFDQ1 was validated in parasite by western blot. Immunofluorescence and immune-electron microscopy assay showed that NFDQ1 expressed in both asexual and sexual stages of C. parvum, where it was localized to the cytoplasm of the parasite. Upon ablation of NFDQ1, the ΔNFDQ1 strain showed an apparent growth retardation during sexual replication in vitro.ConclusionsNFDQ1 is a cytoplasmic protein without specific localization to secretory organelles, and it may participate in C. parvum growth during sexual reproduction. Future study should determine the role of NFDQ1 following C. parvum infection in vivo.Graphical

Novel Fosfomycin Resistance Mechanism in Pseudomonas entomophila Due to Atypical Pho Regulon Control of GlpT

Background/Objectives: Pseudomonas entomophila is a ubiquitous bacterium capable of killing insects of different orders and has become a model for host–pathogen studies and a promising tool for biological pest control. In the human pathogen Pseudomonas aeruginosa, spontaneous resistance to fosfomycin arises almost exclusively from mutations in the glycerol-3-phosphate transporter (GlpT), the drug’s sole entry route in this species. Here, we investigated whether this specificity is conserved in P. entomophila, as it could provide a valuable marker system for studying mutation rates and spectra and for selection in genetic engineering. Methods: We isolated 16 independent spontaneous fosfomycin-resistant mutants in P. entomophila, and studied the genetic basis of the resistance using a combination of sequencing, phenotyping and computational approaches. Results: We only found two mutants without alterations in glpT or any of its known regulatory elements. Whole-genome sequencing revealed unique inactivating mutations in phoU, a key regulator of the phosphate starvation (Pho) regulon. Computational analyses identified a PhoB binding site in the glpT promoter, and experiments showed that phoU inactivation reduced glpT expression nearly 20-fold. While placing a sugar-phosphate transporter under the Pho regulon may seem advantageous, bioinformatic analysis shows this configuration is atypical among pseudomonads. Conclusions: this atypical Pho regulon control of GlpT probably reflects the peculiarities of P. entomophila’s habitat and lifestyle; highlighting how readily regulatory evolution can lead to the rapid divergence of resistance mechanisms, even among closely related species.

Scots Pines With Tolerance to Melampsora pinitorqua and Diplodia sapinea Show Distinct Metabolic Profiles.

Diplodia sapinea causes Diplodia tip blight (DTB) and is recognised as an opportunistic necrotrophic pathogen affecting conifers. While DTB is associated with abiotic stress, the impact of biotic stress in the host on D. sapinea's lifestyle shift is unknown. Observed co-occurrences of D. sapinea and Melampsora pinitorqua, causing pine twisting rust on Scots pine (Pinus sylvestris), instigated an investigation into their interaction with and influence on the defence mechanisms of the host. We hypothesised that M. pinitorqua infections predispose the trees to D. sapinea by stressing the host and altering the shoot metabolites. Pines in a plantation were sampled over time to study pathogen biomass and host metabolites. Symptoms of both pathogens were consistent over years, and the preceding season's symptoms affected the metabolic profiles pre-infection and M. pinitorqua's proliferation. Symptoms of M. pinitorqua altered shoot metabolites more than fungal biomass, with co-symptomatic trees exhibiting elevated M. pinitorqua biomass. Specific phenolic compounds had a strong positive association with the shoot symptom × D. sapinea interaction. D. sapinea's biomass presymptoms was independent of previous disease symptoms and infection by M. pinitorqua. Some trees showed disease tolerance, with delayed rust infections and minimal DTB symptoms. Further investigations on this trait are needed.

Genomic characterization of Pantoea dispersa A003 isolated from a clinical patient

IntroductionPantoea dispersa is a Gram-negative bacterium generally considered as a plant pathogen and rarely causes human infections. To date, there have been 13 studies that have documented clinical infections linked to P. dispersa, with a primary emphasis on the initial identification of this pathogen. The genomic features and the mechanisms underlying the pathogenesis of P. dispersa remain largely uninvestigated. In the present study, we describe a clinical infection caused by P. dispersa and provide the first genomic analysis of this bacterium.MethodsThe bacterial strain designated A003 was isolated from blood samples. Preliminary identification of strain A003 was conducted using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) technology (VITEK® MS, bioMérieux, France). Biochemical and antimicrobial susceptibility assessments were carried out utilizing the VITEK-2 compact automated microbial analysis system (bioMérieux, France). Additionally, whole genome sequencing and subsequent analysis were performed to further elucidate the potential pathogenicity.ResultsThe bacterial isolate was cultured overnight at 35°C in a CO2-enriched environment on Columbia blood agar, resulting in the appearance of a white, smooth, Gram-negative rod-shaped bacterium with diameters ranging from 1 to 2 mm. Identification of strain A003 was achieved with a high confidence level of 99.9% as P. dispersa using MALDI-TOF mass spectrometry. The average nucleotide identity (ANI) value between strain A003 and the reference strain P. dispersa DSM 30073T was 98.08%, while the DNA–DNA hybridization (DDH) value was 84.10% (Formula 2) based on genome sequencing data, which further confirmed that A003 belonged to the P. dispersa species. Comprehensive analysis revealed the presence of 372 virulence factors, 15 antibiotic resistance genes, 222 carbohydrate-active enzymes, and 666 genes related to Type III secretion system (T3SS) effector proteins, as identified through the core databases of VFDB (Virulence Factors of Pathogenic Bacteria), CARD (Comprehensive Antibiotic Resistance Database), CAZY (Carbohydrate-Active enZYmes Database), and T3SS. The virulence factors included type IV pili (TFP), type VI secretion system, flagella, iron uptake system, and ompA, which are implicated in bacterial pathogenicity. The antibiotic resistance profile indicated resistance to fluoroquinolones, cephalosporins, penams, macrolides, and aminoglycosides, as annotated by the CARD database.ConclusionThe draft genome sequenced represents the inaugural genomic sequence of P. dispersa derived from clinical sources. This advancement may enhance clinical practitioners’ comprehension of the organism’s clinical attributes and serve as a foundational resource for future research into its virulence, antibiotic resistance, and host–pathogen interactions.

Genome resource announcement for emerging pathogen Bipolaris gigantea, isolated from Microstegium vimineum

Bipolaris gigantea is a pathogen of the invasive grass Microstegium vimineum and an emerging pathogen of other hosts such as hemp and barley, causing characteristic eyespot foliar lesions. The fungus is characterized by long pale hyaline conidia measuring about 300 to 350 μm. Previously, this pathogen was classified in the Drechslera genus, and recently reassigned as Bipolaris based on molecular identification. Here, we generated a high-quality draft genome sequence of B. gigantea isolate BGF using long and short read DNA sequencing. The assembled genome, 30.23 Mb in size with a BUSCO completeness score of 98.4%, exhibited synteny with the common grass pathogen B. sorokiniana isolate 10943. Average nucleotide identity (ANI) and single nucleotide polymorphisms (SNP) analyses revealed high sequence identity with B. gigantea isolates from Cannabis sativa fields in Kentucky. This research provides a genomic resource that will contribute to future studies to understand the host range evolution and pathogenicity of this novel pathogen.

Unravelling the Current Status of Rice Stripe Mosaic Virus: Its Geographical Spread, Biology, Epidemiology, and Management

Rice stripe mosaic virus (RSMV) belongs to the Cytorhabdovirus species in the Rhabdoviridae family. Recently, RSMV was widely spread in East Asia and caused severe yield losses. RSMV is transmitted by the planthopper vectors, Recilia dorsalis, Nephotettix virescens, and Nilaparvata lugens, that mostly affect rice. The adult vectors can hibernate, transmit the virus, lay eggs on rice plants, and, finally, multiply in subsequent generations, resulting in new infection outbreaks. RSMV-infected rice varieties display striped mosaicism, mild dwarfism, stiff and twisted leaves, delayed heading, short panicles with large unfilled grains, and yield reduction. In nature, the infection of multiple pathogens in the same host is widespread, which is defined as co-infection. It can be antagonistic or synergistic. Pathological synergistic effects between RSMV and other viruses can generate strains with new genetic characteristics, leading to unpredictable epidemiological consequences. After the first identification of RSMV in 2015, significant advancements in understanding the disease’s characteristics, symptoms, cycles, geographic distribution, potential vectors, and synergistic interaction, as well as its management strategies, were developed. To reduce the damage due to RSMV infection, many scientists have recommended pest control techniques to target adult vectors. It is also essential to confirm the actual time of monitoring, development of resistant varieties, and changes in cultivation systems. Due to the limitations of the conventional plant disease control technologies, improvements in efficiency and safety are in high demand. Therefore, to find efficient and environmentally safe controls to mitigate these challenges, reviews of research are the foremost step. In this review, we summarize the basic epidemiological information about the origin of RSMV and its infection symptoms in the field, synergistic interaction with viruses during co-transmission, yield losses, formulation of the disease cycle, and control strategies from several case studies. Finally, we recommend the formulation of the disease cycle and management strategies of RSMV infection.

Investigation of Viral, Bacterial and Parasitic Zoonotic Diseases in Rodents in Turkey.

Rodents are reservoir hosts for zoonotic pathogens that cause tropical diseases, many of which have been overlooked. The aim of this study was to investigate the presence of viral lymphocytic choriomeningitis and hantavirus infections, bacterial tularaemia and leptospirosis, and parasitic leishmaniasis and toxoplasmosis in rodents that are likely to carry and spread zoonotic agents, by using molecular methods. A total of 498 voles collected from 20 counties of Erzurum province. Conventional PCR was used for pathogen search. PCR-positive samples were subjected to sequence analysis. Hantavirus (4.8%, 24/498) and tularaemia (0.8%, 4/498) positivity were detected. However, no positivity was detected for other selected pathogens. Rodents, which are pathogen carriers and potential risk factors, are thought to may act as reservoirs for hantavirus and tularaemia in the study area. A preliminary study has been carried out at the point of detection of these diseases of global importance. The extent of the distribution of the infections, alternative hosts and the consequences of human exposure needs to be clarified through further studies.

Insights into ubiquitinome dynamics in the host‒pathogen interplay during Francisella novicida infection

Ubiquitination functions as an important posttranslational modification for orchestrating inflammatory immune responses and cell death during pathogenic infection. The ubiquitination machinery is a major target hijacked by pathogenic bacteria to promote their survival and proliferation. Type I interferon (IFN-I) plays detrimental roles in host defense against Francisella novicida (F. novicida) infection. The effects of IFN-I on the ubiquitination of host proteins during F. novicida infection remain unclear. Herein, we delineate the dynamic ubiquitinome alterations in both wild-type (WT) and interferon-alpha receptor-deficient (Ifnar–/–) primary bone marrow-derived macrophages (BMDMs) during F. novicida infection. Using diGly proteomics and stable isotope labeling (SILAC), we quantified ubiquitination sites in proteins from primary WT and Ifnar–/– BMDMs with and without F. novicida infection. Our mass spectrometry analysis identified 2,491 ubiquitination sites in 1,077 endogenous proteins. Our study revealed that F. novicida infection induces dynamic changes in the ubiquitination of proteins involved in the cell death, phagocytosis, and inflammatory response pathways. IFN-I signaling is essential for both the increase and reduction in ubiquitination in response to F. novicida infection. We identified IFN-I-dependent ubiquitination in proteins involved in glycolysis and vesicle transport processes and highlighted key hub proteins modified by ubiquitination within cell death pathways. These findings underscore the significant influence of IFN-I signaling on modulating ubiquitination during F. novicida infection and provide valuable insights into the complex interplay between the host and F. novicida.

Quantification of influenza virus mini viral RNAs using Cas13.

Influenza A virus (IAV) RNA synthesis produces full-length and deletion-containing RNA molecules, which include defective viral genomes (DVG) and mini viral RNAs (mvRNA). Sequencing approaches have shown that DVG and mvRNA species may be present during infection, and that they can vary in size, segment origin, and sequence. Moreover, a subset of aberrant RNA molecules can bind and activate host pathogen receptor retinoic acid-inducible gene I (RIG-I), leading to innate immune signaling and the expression of type I and III interferons. Measuring the kinetics and distribution of these immunostimulatory aberrant RNA sequences is important for understanding their function in IAV infection. Here, we explored if IAV mvRNA molecules can be detected and quantified using amplification-free, CRISPR-LbuCas13a-based detection. We show that CRISPR-LbuCas13a can be used to measure the copy numbers of specific mvRNAs in samples from infected tissue culture cells. However, to efficiently detect mvRNAs in other samples, promiscuous CRISPR guide RNAs are required that activate LbuCas13a in the presence of multiple mvRNA sequences. One crRNA was able to detect full-length IAV segment 5 without amplification, allowing it to be used for general IAV infection detection nasopharyngeal swabs. Using CRISPR-LbuCas13a, we confirm that mvRNAs are present in ferret upper and lower respiratory tract tissue, as well as clinical nasopharyngeal swab extracts of hospitalized patients. Overall, CRISPR-LbuCas13a-based RNA detection is a useful tool for studying deletion-containing viral RNAs and it complements existing amplification-based approaches.

Signature of viral fossils: a comparative genomics approach to understand the diversity of endogenous retroviruses in bats

Endogenous retroviruses (ERVs) are traces of past viral infections commonly found in vertebrate genomes. Many ERVs are tightly regulated by the host genomes and co-opted for various functions within the hosts. Bats are the only true volant mammals, with the smallest mammalian genomes and a high fraction of ERVs within the genomes. They are important hosts for various zoonotic viral pathogens and can effectively modulate their immune response to tolerate viral infections. Integrations of retroviruses have been implicated as one of the mechanisms by which bats have co-evolved strategies to combat viral infections. In this study, we investigated the diversity of ERVs in over 40 publicly available bat genomes to understand the distribution and the evolution of ERVs within bats. We observed all classes of ERVs within bat genomes including even the complex lenti retroviruses. Alpha and spuma retroviruses which are, generally considered rare in mammals, were common within bats. We observed a positive correlation between bat genome size and length of ERV elements. Interestingly, nearly 30% of the ERVs within bats are intact suggesting a recent origin or co-option by the host genome. Future studies focusing on comparative genomic and experimental data will be critical to understand the role of these ERVs in host genome evolution.

An iron-binding protein of entomopathogenic fungus suppresses the proliferation of host symbiotic bacteria

BackgroundEntomopathogenic fungal infection-induced dysbiosis of host microbiota offers a window into understanding the complex interactions between pathogenic fungi and host symbionts. Such insights are critical for enhancing the efficacy of mycoinsecticides. However, the utilization of these interactions in pest control remains largely unexplored.ResultsHere, we found that infection by the host-specialist fungus Metarhizium acridum alters the composition of the symbiotic microbiota and increases the dominance of some bacterial symbionts in locusts. Meanwhile, M. acridum also effectively limits the overgrowth of the predominant bacteria. Comparative transcriptomic screening revealed that the fungus upregulates the production of MaCFEM1, an iron-binding protein, in the presence of bacteria. This protein sequesters iron, thereby limiting its availability. Functionally, overexpression of MaCFEM1 in the fungus induces iron deprivation, which significantly suppresses bacterial growth. Conversely, MaCFEM1 knockout relieves the restriction on bacterial iron availability, resulting in iron reallocation. Upon ΔMaCFEM1 infection, some host bacterial symbionts proliferate uncontrollably, turning into opportunistic pathogens and significantly accelerating host death.ConclusionsThis study elucidates the critical role of pathogenic fungal-dominated iron allocation in mediating the shift of host microbes from symbiosis to pathogenicity. It also highlights a unique biocontrol strategy that jointly exploits pathogenic fungi and bacterial symbionts to increase host mortality.5MpJPM8R63G6GM1oNrbXUCVideo

Pangolin scales as adaptations for innate immunity against pathogens

BackgroundPangolins are the only mammals that have overlapping scales covering most of their bodies, and they play a crucial role in the ecosystem, biological research, and human health and disease. Previous studies indicated pangolin scale might provide an important mechanical defense to themselves. The origin and exact functions of this unique trait remain a mystery. Using a multi-omics analysis approach, we report a novel functional explanation for how mammalian scales can provide host–pathogen defense.ResultsOur data suggest that pangolin scales have a sophisticated structure that could potentially trap pathogens. We identified numerous proteins and metabolites exhibiting antimicrobial activity, which could suggest a role for scales in pathogen defense. Notably, we found evidence suggesting the presence of exosomes derived from diverse cellular origins, including mesenchymal stem cells, immune cells, and keratinocytes. This observation suggests a complex interplay where various cell types may contribute to the release of exosomes and antimicrobial compounds at the interface between scales and viable tissue. These findings indicate that pangolin scales may serve as a multifaceted defense system, potentially contributing to innate immunity. Comparisons with human nail and hair revealed pangolin-specific proteins that were enriched in functions relating to sensing, immune responses, neutrophil degranulation, and stress responses. We demonstrated the antimicrobial activity of key pangolin scale components on pathogenic bacteria by antimicrobial assays.ConclusionsThis study identifies a potential role of pangolin scales and implicates scales, as possible determinants of pathogen defense due to their structure and contents. We indicate for the first time the presence of exosomes in pangolin scales and propose the new functions of scales and their mechanisms. This new mechanism could have implications for multiple fields, including providing interesting new research directions and important insights that can be useful for synthesizing and implementing new biomimetic antimicrobial approaches.

The Impact of Exposure Dosage and Host Genetics on the Shedding Kinetics of Flavobacterium psychrophilum in Rainbow Trout.

Flavobacterium psychrophilum, the causative agent of bacterial cold water disease (BCWD), is one of the leading pathogens in rainbow trout (Oncorhynchus mykiss) aquaculture. To date, there is little knowledge of the transmission kinetics of F. psychrophilum over the course of infection. In particular, how transmission is affected by host genotype and pathogen exposure dosage are not well studied. In order to fill in these knowledge gaps, we exposed two divergently selected lines of rainbow trout (ARS-Fp-R and ARS-Fp-S) to a range of dosages of F. psychrophilum (strain CSF117-10). We then measured mortality and bacterial shedding to estimate transmission risk at multiple time points since initial infection. As dosage increased, the number of fish shedding and the amount of bacteria shed increased ranging from 0% to 100% and 103 to 108 cells fish-1 h-1, respectively. In addition, we found that disease resistance (survival) was not correlated with transmission risk blocking, in that 67% of fish which shed bacteria experienced no clinical disease. In general, fish mortality began on Day 3, peaked between Days 5-7 and was higher in the ARS-Fp-R line. Results from this study could be used to develop epidemiological models and improve disease management, particularly in the context of aquaculture and selective breeding.

Genetic Diversity and Pathogenicity of Phytophthora infestans Isolates on Four Solanum tuberosum (Potato) Cultivars in Nariño, Colombia

Phytophthora infestans remains a major threat to global potato production. This study focused on characterizing and assessing the pathogenicity of P. infestans isolates on detached potato leaves and in greenhouse trials across four cultivars. Seven isolates were obtained from high potato-producing regions in the department of Nariño, Colombia. The isolates were analyzed using 12 microsatellite markers to determine genetic distances. Two genetically distinct isolates showed markedly different pathogenicity on detached leaves: isolate P00921 caused complete infection by day five, whereas P00321 showed no symptoms. These two isolates (P00921 and P00321) selected for having the greatest genetic distance and highest pathogenicity among the seven analyzed were further tested in a greenhouse setup on four potato cultivars using a randomized block design. Disease progression was monitored over nine days. The results indicated significant variations in pathogenicity linked to genetic diversity among isolates. Notably, Capiro and Margarita cultivars were more prone to severe disease than Suprema and Única. These findings highlight the complex nature of host–pathogen interactions and suggest the need for tailored approaches in disease management and cultivar selection.

Viral-bacterial co-infections screen in vitro reveals molecular processes affecting pathogen proliferation and host cell viability

The broadening of accessible methodologies has enabled mechanistic insights into single-pathogen infections, yet the molecular mechanisms underlying co-infections remain largely elusive, despite their clinical frequency and relevance, generally exacerbating symptom severity and fatality. Here, we describe an unbiased in vitro screening of pairwise co-infections in a murine macrophage model, quantifying pathogen proliferation and host cell death in parallel over time. The screen revealed that the majority of interactions are antagonistic for both metrics, highlighting general patterns depending on the pathogen virulence strategy. We subsequently decipher two distinct molecular interaction points: Firstly, murine Adenovirus 3 modifies ASC-dependent inflammasome responses in murine macrophages, altering host cell death and cytokine production, thereby impacting secondary Salmonella infection. Secondly, murine Adenovirus 2 infection triggers upregulation of Mprip, a crucial mediator of phagocytosis, which in turn causes increased Yersinia uptake, specifically in virus pre-infected bone-marrow-derived macrophages. This work therefore encompasses both a first-of-its-kind systematic assessment of host-pathogen-pathogen interactions, and mechanistic insight into molecular mediators during co-infection.

The RNA receptor RIG-I binding synthetic oligodeoxynucleotide promotes pneumonia survival.

Pneumonia is a worldwide threat to public health, demanding novel preventative and therapeutic strategies. The lung epithelium is a critical environmental interface that functions as a physical barrier to pathogen invasion while also actively sensing and responding to pathogens. We have reported that stimulating lung epithelial cells with a combination therapeutic consisting of a diacylated lipopeptide and a synthetic CpG oligodeoxynucleotide (ODN) induces synergistic pneumonia protection against a wide range of pathogens. We report here that mice deficient in Toll-like receptor 9 (TLR9), the previously described receptor for ODN, still displayed partial ODN-induced protection. This prompted us to seek an alternate ODN receptor, and we discovered by mass spectroscopy that the RNA sensor RIG-I could also bind DNA-like ODN. ODN binding by RIG-I resulted in MAVS-dependent pneumonia-protective signaling events. While RIG-I is essential to native defenses against viral infections, we report that therapeutic RIG-I activation with ODN promoted pathogen killing and host survival following both viral and bacterial challenges. These data indicate that maximal ODN-induced pneumonia protection requires activation of both TLR9/MyD88 and RIG-I/MAVS signaling pathways. These findings not only identify what we believe to be a novel pattern recognition receptor for DNA-like molecules, but reveal a potential therapeutic strategy to protect susceptible individuals against lethal pneumonias during periods of peak vulnerability.

First person – Cecilia Alejandra Vazquez

ABSTRACT First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping researchers promote themselves alongside their papers. Cecilia Alejandra Vazquez is first author on ‘ Intracellular lipid droplets are exploited by Junín virus in a nucleoprotein-dependent process’, published in JCS. Cecilia Alejandra is a postdoc in the lab of Dr Sandra M. Cordo and Dr Cybele C. García at Universidad de Buenos Aires Int, Buenos Aires, Argentina, where she is interested in all things regarding the ‘One Health’ concept of optimizing the health of people, animals and ecosystems. In particular, I am passionate about host–pathogen interactions, how they can be affected by the environment and how understanding them can lead to the development of new therapies.