Host Immunity Research Articles

Multi-omics approaches define novel aphid effector candidates associated with virulence and avirulence phenotypes

Abstract Background Compatibility between plant parasites and their hosts is genetically determined {Citation}both interacting organisms. For example, plants may carry resistance (R) genes or deploy chemical defences. Aphid saliva contains many proteins that are secreted into host tissues. Subsets of these proteins are predicted to act as effectors, either subverting or triggering host immunity. However, associating particular effectors with virulence or avirulence outcomes presents challenges due to the combinatorial complexity. Here we use defined aphid and host genetics to test for co-segregation of expressed aphid transcripts and proteins with virulent or avirulent phenotypes. Results We compared virulent and avirulent pea aphid parental genotypes, and their bulk segregant F1 progeny on Medicago truncatula genotypes carrying or lacking the RAP1 (Resistance to Acyrthosiphon pisum 1) resistance quantitative trait locus. Differential gene expression analysis of whole body and head samples, in combination with proteomics of saliva and salivary glands, enabled us to pinpoint proteins associated with virulence or avirulence phenotypes. There was relatively little impact of host genotype, whereas large numbers of transcripts and proteins were differentially expressed between parental aphids, likely a reflection of their classification as divergent biotypes within the pea aphid species complex. Many fewer transcripts intersected with the equivalent differential expression patterns in the bulked F1 progeny, providing an effective filter for removing genomic background effects. Overall, there were more upregulated genes detected in the F1 avirulent dataset compared with the virulent one. Some genes were differentially expressed both in the transcriptome and in the proteome datasets, with aminopeptidase N proteins being the most frequent differentially expressed family. In addition, a substantial proportion (27%) of salivary proteins lack annotations, suggesting that many novel functions remain to be discovered. Conclusions Especially when combined with tightly controlled genetics of both insect and host plant, multi-omics approaches are powerful tools for revealing and filtering candidate lists down to plausible genes for further functional analysis as putative aphid effectors.

Single‐nucleus RNA sequencing reveals midgut cellular heterogeneity and transcriptional profiles in Bombyx mori cytoplasmic polyhedrosis virus infection

AbstractThe gut is not only used by insects as an organ for the digestion of food and absorption of nutrients but also as an important barrier against the invasion and proliferation of pathogenic microorganisms. Bombyx mori cytoplasmic polyhedrosis virus (BmCPV), an insect‐specific virus, predominantly colonizes the midgut epithelial cells of the silkworm, thereby jeopardizing its normal growth. However, there is limited knowledge of the cellular immune responses to viral infection and whether the infection is promoted or inhibited by different types of cells in the silkworm midgut. In this study, we used single‐nucleus RNA sequencing to identify representative enteroendocrine cells, enterocytes, and muscle cell types in the silkworm midgut. In addition, by analyzing the transcriptional profiles of various subpopulations in the infected and uninfected groups, we found that BmCPV infection suppresses the response of the antiviral pathways and induces the expression of BmHSP70, which plays a role in promoting BmCPV replication. However, certain immune genes in the midgut of the silkworm, such as BmLebocin3, were induced upon viral infection, and downregulation of BmLEB3 using RNA interference promoted BmCPV replication in the midgut of B. mori. These results suggest that viral immune evasion and active host resistance coexist in BmCPV‐infected silkworms. We reveal the richness of cellular diversity in the midgut of B. mori larvae by single‐nucleus RNA sequencing analysis and provide new insights into the complex interactions between the host and the virus at the single‐cell level.

Concomitant parasite infections influence tuberculosis immunopathology and favor rapid sputum conversion of pulmonary tuberculosis patients

Immunopathology of human tuberculosis (TB) in a subgroup of patients is characterized by aberrantly high concentrations of inflammatory cytokines, for example Interleukin (IL)-6. Concomitant (co-)infections by parasites can affect host immunity, but the impact on immunopathology in TB patients is poorly defined. Here we characterized a group of patients with TB ( n = 76) from Ghana with different protozoan and helminth co-infections. Plasma cytokines were measured at the onset of disease and anti-mycobacterial treatment efficacy was monitored during disease course. A subgroup of TB patients had co-infections with protozoan (n = 19) or helminth (n = 16) parasites. Plasma analyses for candidate cytokines identified lower levels of IL-6 in parasite co-infected patients with TB. Moreover, it took less time for co-infected patients to become sputum-negative for Mycobacterium tuberculosis during treatment. These results indicated an influence of parasite co-infections on immunopathology in TB and suggested positive effects on treatment efficacy.

Altered genomic methylation promotes Staphylococcus aureus persistence in hospital environment

Staphylococcus aureus can cause outbreaks and becomes multi-drug resistant through gene mutations and acquiring resistance genes. However, why S. aureus easily adapts to hospital environments, promoting resistance and recurrent infections, remains unknown. Here we show that a specific S. aureus lineage evolved from a clone that expresses the accessory gene regulator (Agr) system to subclones that reversibly suppressed Agr and caused an outbreak in the hospital setting. S. aureus with flexible Agr regulation shows increased ability to acquire antibiotic-resistant plasmids, escape host immunity, and colonize mice. Bacteria with flexible Agr regulation shows altered cytosine genomic methylation, including the decreased 5mC methylation in transcriptional regulator genes (pcrA and rpsD), compared to strains with normal Agr expression patterns. In this work, we discover how altered genomic methylation promotes flexible Agr regulation which is associated with persistent pathogen colonization in the hospital environment.

A widespread phage-encoded kinase enables evasion of multiple host antiphage defence systems.

DNA degradation (Dnd) is a widespread bacterial antiphage defence system that relies on DNA phosphorothioate (PT) modification for self/non-self discrimination and subsequent degradation of unmodified DNA. Phages employ counterstrategies to evade host immunity, but anti-Dnd immunity has not been characterized. Here we report an immune evasion protein encoded by the Salmonella phage JSS1 that contributes to subverting Dnd and other defence systems. Using quantitative proteomic and phosphoproteomic analyses, we show that the protein JSS1_004 employs N-terminal Ser/Thr/Tyr protein kinase activity to catalyse the multisite phosphorylation of host DndFGH. Notably, JSS1_004 also phosphorylates other bacterial immune systems to varying degrees, including CRISPR‒Cas, QatABCD, SIR2+HerA and DUF4297+HerA. Given that JSS1_004 and its homologues are widespread in phylogenetically diverse phages, we suggest that this strategy constitutes a family of immune evasion proteins that increases the chances of phage proliferation even when a host deploys multiple defence systems.

Shrimp Intestinal Microbiota Homeostasis: Dynamic Interplay Between the Microbiota and Host Immunity

ABSTRACTThe shrimp intestine harbors a microbiota that has pivotal roles for host's physiology. Imbalance of shrimp intestinal microbiota has been shown closely related to the occurrence of diseases. The morphological and biological features of the shrimp intestine are considered suboptimal for stable microbial colonization, making the intestinal microbiota composition highly susceptible to the impact of environmental changes or stressors, and particularly unstable. Therefore, the relative unsteadiness of the microbiota composition represents a continuous threat to host survival. Shrimp intestinal microbiota homeostasis is achieved through a dynamic interplay between the microbiota and the host's innate immunity. The shrimp intestine possesses effective innate immune mechanisms that can suppress the uncontrolled proliferation of microbiota components, and simultaneously protect the microbiota from elimination. The mechanism(s) by which the microbial components and the intestinal innate immunity interact with each other to achieve homeostasis represents an interesting interplay between host and microbiota. This review summarizes the current knowledge about intestinal microbiota colonization in shrimp, as well as the intricate mechanisms employed by the intestinal immune system to regulate this microbiota. Moreover, the potential intervention strategies to promote and protect shrimp intestinal homeostasis by modulating the microbiota are also discussed. Thus, this review seeks to comprehensively analyze the current information and contribute to a deeper understanding of the complex interplay between the shrimp intestinal microbiota and innate immunity in maintaining shrimp intestinal homeostasis and overall health. This enhanced understanding may potentially open new avenues for aquaculture management and disease mitigation strategies, ultimately benefiting the shrimp farming industry.

Infectious parvovirus B19 circulates in the blood coated with active host protease inhibitors

The lack of a permissive cell culture system has limited high-resolution structures of parvovirus B19 (B19V) to virus-like particles (VLPs). In this study, we present the atomic resolution structure (2.2 Å) of authentic B19V purified from a patient blood sample. There are significant differences compared to non-infectious VLPs. Most strikingly, two host protease inhibitors (PIs), inter-alpha-trypsin inhibitor heavy chain 4 (ITIH4) and serpinA3, were identified in complex with the capsids in all patient samples tested. The ITIH4 binds specifically to the icosahedral fivefold axis and serpinA3 occupies the twofold axis. The protein-coated virions remain infectious, and the capsid-associated PIs retain activity; however, upon virion interaction with target cells, the PIs dissociate from the capsid prior to viral entry. Our finding of an infectious virion shielded by bound host serum proteins suggests an evolutionarily favored phenomenon to evade immune surveillance and escape host protease activity.

Evolutionary Analysis and Antiviral Drug Prediction of Mpox Virus

The resurgence of mpox virus (MPXV) poses a significant challenge to global public health. Currently, there is a limited understanding of the evolutionary details of MPXV during its epidemics, and no specific drugs have been developed for it. Herein, analysis of mutations and positive selection sites (PSSs) within the MPXV genomes revealed 799 mutations and 40 PSSs. Visualization analysis indicated that these mutations and PSSs may affect protein structure. Additionally, a protein–protein interaction (PPI) network between human and MPXV was established, identifying 346 MPXV-interacting human proteins (MIHPs). An interaction network involving MIHPs and other viruses confirmed that these proteins can interact with various viruses that infect humans. Functional analysis of MIHPs suggested their enrichment in host immunity pathways. Lastly, two drugs targeting MIHPs and four compounds targeting MPXV proteins were screened as candidate antivirals against MPXV. These findings not only deepen our understanding of MPXV evolution but also aid in the development of anti-MPXV drugs.

Critical and diverse role of alarmin cytokines in parasitic infections

Alarmin cytokines including IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) function as danger signals to trigger host immunity in response to tissue injury caused by pathogenic factors such as parasitic infections. Parasitic diseases also provide an excellent context to study their functions and mechanisms. Numerous studies have indicated that alarmin cytokine released by non-immune cells such as epithelial and stromal cells induce the hosts to initiate a type 2 immunity that drives parasite expulsion but also host pathology such as tissue injury and fibrosis. By contrast, alarmin cytokines especially IL-33 derived from immune cells such as dendritic cells may elicit an immuno-suppressive milieu that promotes host tolerance to parasites. Additionally, the role of alarmin cytokines in parasite infections is reported to depend on species of parasites, cellular source of alarmin cytokines, and immune microenvironment, all of which is relevant to the parasitic sites or organs. This narrative review aims to provide information on the crucial and diverse role of alarmin cytokines in parasitic infections involved in different organs including intestine, lung, liver and brain.

CDC42 enhances phagocytic activity and exhibits antimicrobial functions through the recruitment of IQGAP1 in Apostichopus japonicus

Cell Division Cycle 42 protein (CDC42) is a pivotal member of the Rho family of small GTPases, integral to cell signaling and the regulation of cell polarity. CDC42 is extensively documented to participate in host immunity, particularly in processes such as phagocytosis and cell migration. Nevertheless, the precise mechanisms by which CDC42 affects host-bacteria interactions remain unclear in Echinoderms. In this study, we have isolated and characterized the CDC42 gene from Apostichopus japonicus, referred to as AjCDC42. The complete cDNA sequence of AjCDC42 extends 1282 base pairs, including a typical classical RHO domain, spanning amino acids from 6 to 179. Spatial expression analysis demonstrated that AjCDC42 is ubiquitously expressed across all examined tissues. Following infection with Vibrio splendidus and stimulation with LPS, the protein and mRNA levels of AjCDC42 were significantly upregulated in coelomocytes. Moreover, the knockdown of AjCDC42 significantly decreased V. splendidus-induced phagocytic activity in coelomocytes, leading to a reduced intracellular load of V. splendidus, as evidenced by flow cytometry and bacterial plate counting assays. Mechanistically, AjCDC42 was identified as an interacting partner of IQ Motif Containing GTPase Activating Protein 1 (AjIQGAP1) through the use of co-immunoprecipitation, immunofluorescence, and GST pull-down assays combined with mass spectrometry techniques. Additional functional analyses revealed that the knockdown of AjIQGAP1 similarly decreased the phagocytic activity and the intracellular load of V. splendidus in coelomocytes. Furthermore, we detected that decreased levels of AjCDC42 and AjIQGAP1 impaired cytoskeletal rearrangement and delayed lysosomal clearance of V. splendidus. In summary, our findings underscore the pivotal role of the AjCDC42-AjIQGAP1 axis in regulating coelomocytes phagocytosis in A. japonicus during V. splendidus infection.

Leptospira Leptolysin Contributes to Serum Resistance but Is Not Essential for Acute Infection.

Previous invitro works focusing on virulence determinants of the spirochete Leptospira implicated metalloproteinases as putative contributing factors to the pathogenicity of these bacteria. Those proteins have the capacity to degrade extracellular matrix components (ECM) and proteins of host's innate immunity, notably effectors of the complement system. In this study, we gained further knowledge on the role of leptolysin, one of the leptospiral-secreted metalloproteinases, previously described as having a broad substrate specificity. We demonstrated that a proportion of human patients with mild leptospirosis evaluated in the current study produced antibodies that recognize leptolysin, thus indicating that the protease is expressed during host infection. Using recombinant protein and a knockout mutant strain, Manilae leptolysin-, we determined that leptolysin contributes to Leptospira interrogans serum resistance invitro, likely by proteolysis of complement molecules of the alternative, the classical, the lectin, and the terminal pathways. Furthermore, in a hamster model of infection, the mutant strain retained virulence; however, infected animals had lower bacterial loads in their kidneys. Further studies are necessary to better understand the role and potential redundancy of metalloproteinases on the pathogenicity of this important neglected disease.

The Phytophthora infestans effector Pi05910 suppresses and destabilizes host glycolate oxidase StGOX4 to promote plant susceptibility.

Phytophthora infestans is a notorious oomycete pathogen that causes potato late blight. It secretes numerous effector proteins to manipulate host immunity. Understanding mechanisms underlying their host cell manipulation is crucial for developing disease resistance strategies. Here, we report that the conserved RXLR effector Pi05910 of P. infestans is a genotype-specific avirulence elicitor on potato variety Longshu 12 and contributes virulence by suppressing and destabilizing host glycolate oxidase StGOX4. By performing co-immunoprecipitation, yeast-two-hybrid assays, luciferase complementation imaging, bimolecular fluorescence complementation and isothermal titration calorimetry assays, we identified and confirmed potato StGOX4 as a target of Pi05910. Further analysis revealed that StGOX4 and its homologue NbGOX4 are positive immune regulators against P. infestans, as indicated by infection assays on potato and Nicotiana benthamiana overexpressing StGOX4 and TRV-NbGOX4 plants. StGOX4-mediated disease resistance involves enhanced reactive oxygen species accumulation and activated the salicylic acid signalling pathway. Pi05910 binding inhibited enzymatic activity and destabilized StGOX4. Furthermore, mutagenesis analyses indicated that the 25th residue (tyrosine, Y25) of StGOX4 mediates Pi05910 binding and is required for its immune function. Our results revealed that the core RXLR effector of P. infestans Pi05910 suppresses plant immunity by targeting StGOX4, which results in decreased enzymatic activity and protein accumulation, leading to enhanced plant susceptibility.

Genomic epidemiology and immune escape of SARS-CoV-2 recombinant strains circulating in Botswana

Background: SARS-CoV-2 continues to evolve and evade host immunity. We characterized the molecular and mutational landscape of SARS-CoV-2 recombinant strains in Botswana.Methods: We performed genomic, phylogenetic, and immunoinformatic analyses of 5,254 near-complete genomes from 2020 to 2023. We assessed the presence of mutations of interested (MutOI) that may be associated with immune escape in silico.Results: We observed a few recombinant strains in Botswana, with the majority being descendants of Omicron (XBB*), except for XV and XM. Most recombinant sequences corresponded to transmission clusters. Most recombination events occurred within the Receptor Binding Domain (RBD) of the Spike (S) protein. We identified 17 MutOI among different proteins, with the majority occurring at a very low (<4.8 × 10⁻⁵) global prevalence. We also observed S:Q474K, a MutOI in the RBD, that was predicted to escape HLA class I-mediated immune responses. Molecular surveillance is vital to inform early detection and response to potential variants with heightened immune and vaccine breakthrough properties.Conclusions: These results underscore the need for continued molecular surveillance to map the evolutionary landscape of SARS-CoV-2.

The microRNAome of Strongylus vulgaris larvae and their excretory/secretory products with identification of parasite-derived microRNAs in horse arterial tissue

The equine bloodworm, Strongylus vulgaris, is a highly pathogenic parasite causing potentially fatal vascular and intestinal damage. Parasites express and release microRNAs (miRNAs) for internal regulation and to modulate host immunity. The complete set of miRNAs expressed by S. vulgaris (the S. vulgaris miRNAome) remains unannotated and the aim of this study was to annotate the miRNAome of L4 and L5 stages of S. vulgaris, and to examine differences in miRNA abundance between larval stages and sexes. Furthermore, we aimed to determine if miRNAs were detectable in excretory/secretory products (ESPs) from larvae and in arterial tissue from their predilection site, the cranial mesenteric artery (CMA). Larvae were collected from naturally infected foals, and categorized by sex and stage. A subset of larvae was snap-frozen, while those remaining were incubated and the (ESPs) collected. Arterial tissue samples were collected from the CMA. Small RNA sequencing, followed by a custom bioinformatic pipeline, was used for annotation. We identified 142 S. vulgaris miRNAs in larvae and 136 in ESPs. Significant differences in miRNA abundance were observed between larvae and ESPs, and between L5 females (L5Fs) and L5 males (L5Ms), L4s and L5Fs, and L4s and L5Ms. No differences were found between L4s and L5s overall. In ESPs, several miRNAs were differentially abundant across all groups. Validation through quantitative real-time PCR (qPCR) detected selected miRNAs and their differential abundance in larvae and ESPs. One parasite-derived miRNA was detected in some of the horse arterial tissue samples but at very low levels. This study provided the first annotation of the S. vulgaris miRNAome. Most of the annotated larval miRNAs were also detectable in ESPs, and differences in miRNA abundance between sexes were found for larvae, and between sexes and stages for ESPs. Parasite-derived miRNAs were, however, not consistently detectable in the surrounding host arterial tissue.

Metabolites augment oxidative stress to sensitize antibiotic-tolerant Staphylococcus aureus to fluoroquinolones.

If left unchecked, infections involving antibiotic-refractory bacteria are expected to cause millions of deaths per year in the coming decades. Beyond genetically resistant bacteria, persisters, which are genetically susceptible cells that survive antibiotic doses that kill the rest of the clonal population, can potentially contribute to treatment failure and infection relapse. Stationary-phase bacterial cultures are enriched with persisters, and it has been shown that stimulating these populations with exogenous nutrients can reduce persistence to different classes of antibiotics, including topoisomerase-targeting fluoroquinolones (FQs). In this study, we show that adding glucose and amino acids to nutrient-starved Staphylococcus aureus cultures enhanced their sensitivity to FQs, including delafloxacin (Dela)-a drug that was recently approved for treating staphylococcal infections. We found that while the added nutrients increased nucleic acid synthesis, this increase was not required to sensitize S. aureus to FQs. We further demonstrate that addition of these nutrients increases membrane potential and the ability to generate harmful reactive oxygen species (ROS) during FQ treatment. Chelating iron, scavenging hydroxyl radicals, and limiting oxygenation during FQ treatment and during recovery following FQ treatment rescued nutrient-stimulated S. aureus. In all, our data suggest that while nutrient stimulation increases the activity of FQ targets in stationary-phase S. aureus, the resulting generation of ROS, presumably made possible through metabolic upregulation, is the primary driver of increased sensitivity to these drugs.IMPORTANCEStaphylococcus aureus causes many chronic and relapsing infections because of its ability to endure host immunity and antibiotic therapy. While several studies have focused on the nutrient requirements for the formation and maintenance of staphylococcal infections, the effects of the nutrient environment on bacterial responses to antibiotic treatment remain understudied. Here, we show that adding nutrients to starved S. aureus activates biosynthetic processes, including DNA synthesis, but it is the generation of harmful reactive oxidants that sensitizes S. aureus to DNA topoisomerase-targeting FQs. Our results suggest that the development of approaches aimed at perturbing metabolism and increasing oxidative stress can potentiate the bactericidal activity of FQs against antibiotic-tolerant S. aureus.

An effector essential for virulence of necrotrophic fungi targets plant HIRs to inhibit host immunity

Phytopathogens often secrete effectors to enhance their infection of plants. In the case of Sclerotinia sclerotiorum, a necrotrophic phytopathogen, a secreted protein named SsPEIE1 (Sclerotinia sclerotiorum Plant Early Immunosuppressive Effector 1) plays a crucial role in its virulence. During the early stages of infection, SsPEIE1 is significantly up-regulated. Additionally, transgenic plants expressing SsPEIE1 exhibit increased susceptibility to different phytopathogens. Further investigations revealed that SsPEIE1 interacts with a plasma membrane protein known as hypersensitive induced reaction (HIR) that dampens immune responses. SsPEIE1 is required for S. sclerotiorum virulence on wild-type Arabidopsis but not on Arabidopsis hir4 mutants. Moreover, Arabidopsis hir2 and hir4 mutants exhibit suppressed pathogen-associated molecular pattern-triggered reactive oxygen species (ROS) bursts and salicylic acid (SA)-associated immune gene induction, all of which are phenocopied by the SsPEIE1 transgenic plants. We find that the oligomerization of AtHIR4 is essential for its role in mediating immunity, and that SsPEIE1 inhibits its oligomerization through competitively binding to AtHIR4. Remarkably, both Arabidopsis and rapeseed plants overexpress AtHIR4 display significantly increased resistance to S. sclerotiorum. In summary, these results demonstrate that SsPEIE1 inhibits AtHIR4 oligomerization-mediated immune responses by interacting with the key immune factor AtHIR4, thereby promoting S. sclerotiorum infection.

Association of Major Histocompatibility Complex Polymorphism With Acute Phase Response in Broiler Chicken.

Stress associated with changes in host immunity occurs in response to altered environmental conditions, endogenous imbalances, infectious agents and harmful stimuli. The importance of genetic diversity in chickens has increased due to individual immune differences towards resistance and susceptibility to various stimuli. This study aimed to investigate the association of major histocompatibility complex (MHC) polymorphism with acute phase response (APR) in Ross 308 broiler chickens. The allelic diversity of the LEI0258 microsatellite marker was determined in 120 Ross broilers. In addition, acute phase proteins (APPs), including serum amyloid A (SAA) and alpha-1-acid glycoprotein (AGP), were analysed as markers of the APR. Furthermore, leukocyte count and the heterophil/lymphocyte ratio (H/L ratio) were examined. The antibody response to the Newcastle disease vaccine (NDV) was also measured to assess humoral mediated immunity. Lastly, the correlation between immune responses and MHC alleles was investigated to identify the most effective alleles in a stress-related situation. A total of six alleles, ranging from 195 to 448bp, were identified. Association study revealed a significant influence of MHC alleles on APPs in Ross population (p<0.05). Notably, Allele 448 had a significant correlation with SAA concentration and the H/L ratio. Allele 207 displayed a positive association with AGP concentration, whereas Allele 195 showed a negative association. Furthermore, a significant association was observed between Allele 448 and basopenia, as well as between Allele 195 and monocytosis. Results confirmed the significance of MHC as a candidate gene marker for immune responses, which supports its use for vaccine design, genetic improvement of disease-resistant traits and resource conservation in commercial broiler chickens.

CAR Treg synergy with anti-CD154 mediates infectious tolerance to dictate heart transplant outcomes.

Successful allograft specific tolerance induction would eliminate the need for daily immunosuppression and improve post-transplant quality of life. Adoptive cell therapy with regulatory T cells expressing donor-specific Chimeric Antigen Receptors (CAR-Tregs) is a promising strategy, but as monotherapy, cannot prolong the survival with allografts with multiple MHC mismatches. Using an HLA-A2-transgenic haplo-mismatched heart transplantation model in immunocompetent C57Bl/6 recipients, we show that HLA-A2-specific (A2) CAR Tregs was able to synergize with low dose of anti-CD154 to enhance graft survival. Using haplo-mismatched grafts expressing the 2W-OVA transgene and tetramer-based tracking of 2W- and OVA-specific T cells, we showed that in mice with accepted grafts, A2.CAR Tregs inhibited endogenous non-A2 donor- specific T cell, B cell and antibody responses, and promoted a significant increase in endogenous FoxP3 + Tregs with indirect donor-specificity. By contrast, in mice where A2.CAR Tregs failed to prolong graft survival, FoxP3 neg A2.CAR T cells preferentially accumulated in rejecting allografts and endogenous donor-specific responses were not controlled. This study therefore provides the first evidence for synergy between A2.CAR Tregs and CD154 blockade to promote infectious tolerance in immunocompetent recipients of haplo-mismatched heart grafts and defines features of A2.CAR Tregs when they fail to reshape host immunity towards allograft tolerance.

Bioaccumulation of polycyclic aromatic hydrocarbons and microbiota dynamics across developmental stages of the Asian tiger mosquito, Aedes albopictus exposed to urban pollutants

Aedes albopictus mosquitoes face numerous anthropic stressors in urban areas. These xenobiotics not only impact mosquito physiology but also shape the composition of their microbiota, which play important roles in host physiological traits. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants known to alter mosquito metabolism, but no studies have yet investigated their impact on microbiota. Using a bespoke indoor mesocosm tailored for Ae. albopictus mosquitoes, we investigated the dynamics of bacterial communities in both mosquitoes and their larval breeding sites following chronic exposure to a cocktail of PAHs consisting of benzo[a]pyrene, benz[a]anthracene, chrysene and benzo[b]fluoranthene. Our findings showed that PAHs have a stage-specific effect on mosquito microbiota, with a higher impact in larvae than in adults, contributing to 12.5 % and 4.5 % of the PAHs-induced variations, respectively. The presence of PAHs in the treated mesocosm led to the enrichment of bacterial families and genera known for their ability to catabolize PAHs, such as Comamonadaceae and Raoultella (increasing from 19 % to 30 % and from 1.2 % to 5.6 %, respectively). Conversely, prevalent taxa found in mosquito microbiota like Wolbachia and Cedecea exhibited a reduction (decreasing from 4 % to 0.8 % and from 12.8 % to 6.4 %, respectively). This reduction could be attributed to the competitive advantage gained by PAH-degrading taxa, or it could reflect a direct sensitivity to PAH exposure. Overall, this indicates a shift in microbiota composition favoring bacteria that can thrive in a PAH-contaminated environment. PAHs persisted in the water of breeding sites only the first 45 days of the experiment. Benzo[a]pyrene and benzo[b]fluoranthene were more susceptible to bioaccumulation in larval tissues over time. Overall, this study enhances our understanding of the impact of pollution on mosquitoes and could facilitate future research on the importance of symbiosis in urban-dwelling insect disease vectors. Given the recent advancements in the generation of axenic (microbe-free) and gnotobiotic (mosquitoes with a defined or specific microbiota) mosquitoes, further studies are needed to explore how changes in microbiota composition could influence mosquito responses to pollution, particularly in relation to host fitness, immunity, and vector competence.

A photosensitive modification of recombinant Salmonella carrying shRNA-PD-L1 promotes host immunity against poorly immunogenic tumors

The tumor microenvironment (TME) exists as a hypoxic, non-inflammatory “cold” state, it is difficult for many drugs to target the aggregation and activation of the immune system. The attenuated facultative anaerobe Salmonella can be used as a tumor-targeting vector to overcome osmotic limitations and exhibit immune effects against the hypoxic characteristics of the tumor region, maximizing the diagnostic and therapeutic targeting. Here, we genetically modified the ΔphoPΔphoQ knockout strain of attenuated Salmonella enterica serovar typhimurium LH430 to carry programmed cell death ligand 1 (PD-L1) short hairpin RNA (shRNA) on a plasmid to solve the current problem of therapeutic antibodies targeting immune checkpoints in the clinic. In addition, combining the attenuated Salmonella with the photosensitizer IR780 not only allows the bacteria to aggregate and target hypoxia at the tumor site, but also the photothermal therapy for an effective tumor ablation. This approach provides a promising strategy for photothermal therapy and immunotherapy targeting deep-seated tumors.