Antimicrobial Immunity Research Articles

ECR Spotlight – Lindsay Martin

ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Lindsay Martin is an author on ‘ Senescence of humoral antimicrobial immunity occurs in infected mosquitoes when the temperature is higher’, published in JEB. Lindsay is a graduate student in the lab of Julián Hillyer at Vanderbilt University, USA, investigating how warming environmental temperature alters mosquito aging and immunity, and how warmer temperature and aging interact together to modify the mosquito's ability to fight an infection.

Identification and Functional Analysis of Ras-Related Associated with Diabetes Gene (rrad) in Edwardsiella piscicida-Resistant Individuals of Japanese Flounder (Paralichthys olivaceus).

Ras-related associated with diabetes (RRAD) is a member of the Ras GTPase superfamily that plays a role in several cellular functions, such as cell proliferation and differentiation. In particular, the superfamily acts as an NF-κB signaling pathway inhibitor and calcium regulator to participate in the immune response pathway. A recent transcriptome study revealed that rrad was expressed in the spleen of disease-resistant Japanese flounder (Paralichthys olivaceus) individuals compared with disease-susceptible individuals, and the results were also verified by qPCR. Thus, the present study aimed to explore how rrad regulates antimicrobial immunity via the NF-κB pathway. First, the coding sequence of P. olivaceus rrad was identified. The sequence was 1092 bp in length, encoding 364 amino acids. Based on phylogenetic and structural relationship analyses, P. olivaceus rrad appeared to be more closely related to teleosts. Next, rrad expression differences between disease-resistant and disease-susceptible individuals in immune-related tissues were evaluated, and the results revealed that rrad was expressed preferentially in the spleen of disease-resistant individuals. In response to Edwardsiella piscicida infection, rrad expression in the spleen changed. In vitro, co-culture was carried out to assess the hypo-methylated levels of the rrad promoter in the disease-resistant spleen, which was consistent with the high mRNA expression. The siRNA-mediated knockdown of rrad performed with the gill cell line of P. olivaceus affected many rrad-network-related genes, i.e., dcp1b, amagt, rus1, rapgef1, ralbp1, plce1, rasal1, nckipsd, prkab2, cytbc-1, sh3, and others, as well as some inflammation-related genes, such as bal2 and Il-1β. In addition, flow cytometry analysis showed that rrad overexpression was more likely to induce cell apoptosis, with establishing a link between rrad's function and its potential roles in regulating the NF-κB pathway. Thus,. the current study provided some clarity in terms of understanding the immune response about rrad gene differences between disease-resistant and disease-susceptible P. olivaceus individuals. This study provides a molecular basis for fish rrad gene functional analysis and may serve as a reference for in-depth of bacterial disease resistance of teleost.

Immunoresponsive Gene 1 Facilitates TLR4-agonist-Induced Augmentation of Innate Antimicrobial Immunity.

Treatment with the toll-like receptor (TLR) 4 agonist monophosphoryl lipid A (MPLA) conditions innate immunocytes to respond robustly to subsequent infection, a phenotype termed innate immune memory. Our published studies show that metabolic reprogramming of macrophages is a prominent feature of the memory phenotype. We undertook studies to define the functional contributions of tricarboxylic acid (TCA) cycle reprogramming to innate immune memory. We observed that priming of wild type (WT) mice with MPLA potently facilitated accumulation of the TCA cycle metabolite itaconate at sites of infection and enhanced microbial clearance. Augmentation of itaconate accumulation and microbial clearance was ablated in immuneresponsive gene 1 (Irg1) -deficient mice. We further observed that MPLA potently induces expression of Irg1 and accumulation of itaconate in macrophages. Compared to WT macrophages, the ability of Irg1-deficient macrophages to kill Pseudomonas aeruginosa was impaired. We further observed that itaconate is directly antimicrobial against P. aeruginosa at pH 5, which is characteristic of the phagolysosome, and is facilitated by reactive oxygen species. MPLA-induced augmentation of glycolysis, oxidative phosphorylation and accumulation of the TCA cycle metabolites succinate and malate was decreased in Irg1 KO macrophages compared to WT controls. RNA sequencing revealed suppressed transcription of genes associated with phagolysosome function and increased expression of genes associated with cytokine production and chemotaxis in Irg1 deficient macrophages. This study identifies a contribution of itaconate to MPLA-induced augmentation of innate antimicrobial immunity via facilitation of microbial killing as well as impact on metabolic and transcriptional adaptations.

Senescence of humoral antimicrobial immunity occurs in infected mosquitoes when the temperature is higher.

Mosquitoes cannot use metabolism to regulate their body temperature, and therefore, climate warming is altering their physiology. Mosquitoes also experience a physiological decline with aging, a phenomenon called senescence. Because both high temperature and aging are detrimental to mosquitoes, we hypothesized that high temperatures accelerate senescence. Here, we investigated how temperature and aging, independently and interactively, shape the antimicrobial immune response of the mosquito, Anopheles gambiae. Using a zone-of-inhibition assay that measures the antimicrobial activity of hemolymph, we found that antimicrobial activity increases following infection. Moreover, in infected mosquitoes, antimicrobial activity weakens as the temperature rises to 32C, and antimicrobial activity increases from 1 to 5 days of age and stabilizes with further aging. Importantly, in E. coli-infected mosquitoes, higher temperature causes an aging-dependent decline in antimicrobial activity. Altogether, this study demonstrates that higher temperature can accelerate immune senescence in infected mosquitoes, thereby interactively shaping their ability to fight an infection.

HIV-1 and IgA Antibodies: Interactions and implications

Antibodies, particularly Immunoglobulin A (IgA), play a crucial role in mucosal tissues as immune effectors against pathogens and as immunomodulators of the microbiota. During infection with human immunodeficiency virus type 1 (HIV-1), a systemic and mucosal IgA antibody response is triggered. Although naturally produced serum IgA specific to HIV-1 envelope protein are quantitatively and qualitatively lower than their IgG counterparts, they also possess antiviral properties such as neutralization and Fc-dependent effector functions. Neutralizing IgA antibodies can block mucosal transmission of HIV-1 in animal models, suggesting that their induction through vaccination could be pivotal for infection prevention. Recently, broadly neutralizing IgA antibodies have been identified in some individuals living with HIV-1. Given the potential for vaccination to induce these mucosally protective antibodies, research efforts are needed to better understand their development and functions. This review discusses the general roles of IgA antibodies in homeostasis and antimicrobial immunity, and explores their implications in antibody responses during HIV-1 infection.

Induction of trained immunity in broiler chickens following delivery of oligodeoxynucleotide containing CpG motifs to protect against Escherichia coli septicemia

Oligodeoxynucleotides containing CpG motifs (CpG-ODN) can promote antimicrobial immunity in chickens by enriching immune compartments and activating immune cells. Innate memory, or trained immunity, has been demonstrated in humans and mice, featuring the absence of specificity to the initial stimulus and subsequently cross-protection against pathogens. We hypothesize that CpG-ODN can induce trained immunity in chickens. We delivered single or multiple administrations of CpG-ODN to birds and mitochondrial oxidative phosphorylation (OXPHOS) and glycolysis of peripheral blood mononuclear cells were quantified using Seahorse XFp. Next, chickens were administered with CpG-ODN twice at 1 and 4 day of age and challenged with Escherichia coli at 27 days of age. The CpG-ODN administered groups had significantly higher mitochondrial OXPHOS until 21 days of age while cellular glycolysis gradually declined by 14 days of age. The group administered with CpG-ODN twice at 1 and 4 days of age had significantly higher survival, lower clinical score and bacterial load following challenge with E. coli at 27 d of age. This study demonstrated the induction of trained immunity in broiler chickens following administration of CpG-ODN twice during the first 4 days of age to protect birds against E. coli septicemia at 27 days of age.

Iron regulatory protein 2 contributes to antimicrobial immunity by preserving lysosomal function in macrophages

Colorectal cancer and Crohn's disease patients develop pyogenic liver abscesses due to failures of immune cells to fight off bacterial infections. Here, we show that mice lacking iron regulatory protein 2 (Irp2), globally (Irp2-/-) or myeloid cell lineage (Lysozyme 2 promoter-driven, LysM)-specifically (Irp2ΔLysM), are highly susceptible to liver abscesses when the intestinal tissue was injured with dextran sodium sulfate treatment. Further studies demonstrated that Irp2 is required for lysosomal acidification and biogenesis, both of which are crucial for bacterial clearance. In Irp2-deficient liver tissue or macrophages, the nuclear location of transcription factor EB (Tfeb) was remarkably reduced, leading to the downregulation of Tfeb target genes that encode critical components for lysosomal biogenesis. Tfeb mislocalization was reversed by hypoxia-inducible factor 2 inhibitor PT2385 and, independently, through inhibition of lactic acid production. These experimental findings were confirmed clinically in patients with Crohn's disease and through bioinformatic searches in databases from Crohn's disease or ulcerative colitis biopsies showing loss of IRP2 and transcription factor EB (TFEB)-dependent lysosomal gene expression. Overall, our study highlights a mechanism whereby Irp2 supports nuclear translocation of Tfeb and lysosomal function, preserving macrophage antimicrobial activity and protecting the liver against invading bacteria during intestinal inflammation.

Review on Long Non-Coding RNAs as Biomarkers and Potentially Therapeutic Targets for Bacterial Infections.

The confrontation between humans and bacteria is ongoing, with strategies for combating bacterial infections continually evolving. With the advancement of RNA sequencing technology, non-coding RNAs (ncRNAs) associated with bacterial infections have garnered significant attention. Recently, long ncRNAs (lncRNAs) have been identified as regulators of sterile inflammatory responses and cellular defense against live bacterial pathogens. They are involved in regulating host antimicrobial immunity in both the nucleus and cytoplasm. Increasing evidence indicates that lncRNAs are critical for the intricate interactions between host and pathogen during bacterial infections. This paper emphatically elaborates on the potential applications of lncRNAs in clinical hallmarks, cellular damage, immunity, virulence, and drug resistance in bacterial infections in greater detail. Additionally, we discuss the challenges and limitations of studying lncRNAs in the context of bacterial infections and highlight clear directions for this promising field.

#2324 Do urinary tract infections trigger chronic inflammation in the kidney allograft? Interleukin 17 levels in the urine of kidney recipients

Abstract Background and Aims Urinary tract infections (UTI) represent the most common complication following kidney transplantation. Their role in triggering immune phenomena in kidney allograft remains unclear. Interleukin 17 (IL17) represents the significant branch in antimicrobial immunity. At the same time IL17 has been found associated with autoimmune inflammatory disorders. The triggering role of infections in autoimmunity as well as the similarities between autoimmunity and post-transplant immunity have been postulated. The aim of the study was to analyze the levels of urine IL 17A levels in relation to prior UTI history and the timeframe after the last UTI episode. Method The group of 91 kidney recipients who received kidney transplantation between 2016 and 2019 was analyzed. The set of 233 urine samples (109 from females and 124 from males) obtained within first 24 months post-transplant was investigated, among these 144 samples from the patients with no previous UTI history and 89 samples from the patients with previous UTI history (1-22 months after the last episode, average 6.7 ± SD 5.7). Furthermore, 18 samples obtained at the time of an UTI episode and 29 samples from healthy controls were included. Urine IL 17A levels were measured with Human IL 17 ELISA Kit (Sigma Aldrich) and urine IL/creatinine concentrations ratio was calculated for each value. Szapiro-Wilk test was used to assess data distribution, Kruskal-Wallis test was used to assess the differences between independent groups and two proportions Z test was used to compare the groups compositions. Results Interleukin 17A appeared detectable in 105 out of the 233 investigated samples (45%), with significantly higher frequency in samples from the recipients with previous UTI history (p = 0.02). The difference was not significant in the group who underwent recurrent UTI episodes vs. these after a single UTI episode. Among the samples in which IL 17A was detected, the period between the last UTI episode and sample collection was divided into three timeframes: 1-3 months, 4-12 months and 12-24 months. Urine IL17A levels appeared significantly higher independently in each timeframe post-UTI when compared to the samples from the recipients without UTI history and controls (p = 0.0001). Fig. 1 It was apparent within the whole group but also in males and females separately. Further, urine IL17A levels were significantly higher in males 1-3 months after the last UTI episode than in females in the analogous period (p = 0.001). Conclusion Interleukin 17A was more frequently detected in urine samples from kidney recipients with previous UTI history. UTI history impacted IL17A urine levels in the analyzed kidney recipients. Within the first 24 months post-transplant, these were higher in the recipients with UTI history prior to the sample collection and it was independent on the timeframe between the last UTI episode and the sample collection. The factors other than UTI history which influence urine IL17A detectability are not fully recognized and remain under investigation.

Characterisation, prevalence and antibiogram of Aeromonas hydrophila in turtles: insights into virulence factors, antimicrobial resistance genes and innate immunity

ABSTRACT Bacterial infection poses a significant threat to the health and survival of turtles, both in their natural habitats and in captivity. Notably, the presence and interactions of bacteria, such as those belonging to the Aeromonas genus, have been identified for their adverse impact on turtle health and ecosystem dynamics. This study investigated the prevalence, antibiotic susceptibility, virulence factors, and antimicrobial resistance genes of Aeromonas hydrophila in Trachemys scripta elegans (Red-eared Slider) and Chelonia mydas (Green Turtle). The study also examined the innate immunity of T. scripta elegans and C. mydas. Buccal and cloacal swabs from 39 turtles were collected and examined alongside 45 water samples to try to isolate and amplify A. hydrophila. Polymerase chain reaction (PCR) amplifications were then sequenced to identify the presence of specific genes associated with virulence, and antimicrobial resistance. The findings revealed that A. hydrophila had a prevalence rate of 35.9% in all examined turtle species, with 14 water samples accounting for 31% of the total samples. Buccal samples from Green and Red-eared turtles showed a higher rate of A. hydrophila isolates than cloacal samples. Sensitivity to norfloxacin (85.71%), gentamycin (71.42%), and ceftriaxone (64.28%) was observed, whereas resistance to amoxicillin (64.28%), ampicillin (57.14%), and rifamycin (57.14%) was apparent. Antibiotic resistance genes, including blaTEM and blaSHV, in A. hydrophila isolates, were present in 42.86% and 28.5% of the samples, respectively. PCR analysis confirmed the genetic identity of A. hydrophila, and five virulence genes were detected: AHCYTOEN (100%), followed by aerolysin (92.8%), alt and act (85.7%), and lipase (78.5%). Genetic sequences of the isolates had a 99% identity with the reference strains in GenBank. Furthermore, the study found the innate immunity of turtles to be robust due to serum lysozyme activity, bactericidal killing assay (BKA), total leukocyte count, heterophil/lymphocyte ratio, and packed cell volume (PCV%), all of which help to protect them from infections. Overall, this research highlights the need for continued monitoring and management of antibiotic resistance in aquatic ecosystems.

IgA antibodies against HIV-1

Antibodies, and notably immunoglobulins A (IgA), are paramount in mucosal tissues as protective immune effectors against invading pathogens and immunomodulators of the microbiota. Upon human immunodeficiency virus type1 (HIV-1) infection, systemic and mucosal IgA antibody responses are triggered. While naturally produced serum HIV-1 envelope protein-specific IgA are quantitatively and qualitatively weaker than their IgG counterparts, they also possess antiviral properties including neutralization and Fc-dependent functions. IgA neutralizers can block HIV-1 mucosal transmission in animal models, indicating that their elicitation by vaccination would be an important component for preventing infection. Moreover, the first genuine IgA broadly HIV-1 neutralizing antibodies (bNAbs) were recently identified in certain individuals living with HIV-1. Vaccine-based induction of IgA bNAbs potentially protective at the mucosal level is therefore conceivable. Hence, research efforts must therefore be undertaken to better understand their development and functions. In this review, we present the general functions of IgA in homeostasis and antimicrobial immunity and discuss their involvement in the antibody responses against HIV-1.

Spleen transcriptome analysis reveals the immune molecular responses to hypohaline or hyperhaline environments in spotted scat (Scatophagus argus)

Salinity, an important environmental factor, fluctuates frequently and violently in coastal areas, and its dramatic changes tend to have profound effects on the immune function of teleosts. The spotted scat (Scatophagus argus) can tolerate a wide range of salinity fluctuations. However, little is known about its immune response in low and high salinity environments. To elucidate the molecular immune response, the spleen transcriptome of spotted scat was analyzed by RNA sequencing (RNA-seq) after 22 d of culture in water at 5 ppt salinity (low salinity group, LS), 25 ppt salinity (control group, Ctrl), and 35 ppt salinity (high salinity group, HS). RNA-Seq revealed that 1853 and 3554 DEGs were significantly altered by adaptation to low and high salinity, respectively. In addition, 957 genes were co-enriched in the HS and LS. KEGG analysis showed that the focal adhesion, phagosome, ECM-receptor interaction and cytokine-cytokine receptor interaction pathways were significantly enriched in both the Ctrl vs. LS and Ctrl vs. HS. These pathways are involved in immune regulation. RNA-seq showed that genes related to the immune system (ighm, tsp1, sugt1 and hsp90α1), signaling and interaction (pdgfa, pdgfb, mpl, lamb1, itga2, itga3) and cell community (rac3, flna and plk3r3) were significantly downregulated in both hypohaline and hyperhaline environments. Further analysis showed that activation of the splenic NOD-like receptor signaling pathway and the innate immune system occurred in hypersaline but not in hypohaline environments. Salinity stress, particularly high salinity stress, may reduce immunity by limiting the function of the splenic phagosome, reducing resistance to bacterial adhesion, reducing the immune response to pathogens, reducing cell adhesion ability and, and reducing antimicrobial immunity in spotted scat. Evaluation of immune-related responses to salinity fluctuations could provide insight into the immune status of immune organs and the selection of appropriate salinity levels for cultured coastal marine fish.

Transcription of NOD1 and NOD2 and their interaction with CARD9 and RIPK2 in IFN signaling in a perciform fish, the Chinese perch, Siniperca chuatsi.

NOD1 and NOD2 as two representative members of nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family play important roles in antimicrobial immunity. However, transcription mechanism of nod1 and nod2 and their signal circle are less understood in teleost fish. In this study, with the cloning of card9 and ripk2 in Chinese perch, the interaction between NOD1, NOD2, and CARD9 and RIPK2 were revealed through coimmunoprecipitation and immunofluorescence assays. The overexpression of NOD1, NOD2, RIPK2 and CARD9 induced significantly the promoter activity of NF-κB, IFNh and IFNc. Furthermore, it was found that nod1 and nod2 were induced by poly(I:C), type I IFNs, RLR and even NOD1/NOD2 themselves through the ISRE site of their proximal promoters. It is thus indicated that nod1 and nod2 can be classified also as ISGs due to the presence of ISRE in their proximal promoter, and their expression can be mechanistically controlled through PRR pathway as well as through IFN signaling in antiviral immune response.

Extracellular neutrophil traps in cardiovascular diseases: problems and prospects of research

One of the links in the pathogenesis of cardiovascular diseases is chronic low-intensity systemic inflammation. In 2004, a previously unknown process was discovered — the formation of extracellular neutrophil traps (NETs) — NETosis (n eutrophil extracellular traps). NETs play a role in antimicrobial immunity though in certain cases they become a factor in the development of pathology. This review presents data on the effect of extracellular neutrophil traps on individual pathologies of the cardiovascular system (atherosclerosis, atrial fibrillation, thrombosis). The authors describe the mechanisms of NET formation (vital NETosis, suicidal NETosis) and their role in thrombus formation (as a framework for thrombus formation, initiation of coagulation), in the development of endothelial dysfunction, and electrical heterogeneity of the atrial myocardium. Data are presented indicating the connection between atherosclerosis, thrombosis, and atrial fibrillation with the activity of NETosis. Most studies demonstrate existing correlations on laboratory models, while the determination of NETs in patients with cardiovascular pathology in real clinical practice is almost absent. At the same time, understanding the processes associated with NETosis can help to identify specific markers and further strategies for the therapy of cardiovascular diseases.

Molecular characterization, expression pattern and immunologic function of CD82a in large yellow croaker (Larimichthys crocea).

Visceral white spot disease (VWND) caused by Pseudomonas plecoglossicida poses a major threat to the sustainable development of large yellow croaker (Larimichthys crocea) aquaculture. Genome-wide association analysis (GWAS) and RNA-seq research indicated that LcCD82a play an important role in resistance to visceral white spot disease in L. crocea, but the molecular mechanism of LcCD82a response to P. plecoglossicida infection is still unclear. In this study, we cloned and validated the Open Reading Frame (ORF) sequence of LcCD82a and explored the expression profile of LcCD82a in various tissues of L.crocea. In addition, two different transcript variants (LcCD82a-L and LcCD82a-S) of LcCD82a were identified that exhibit alternative splicing patterns after P. plecoglossicida infection, which may be closely related to the immune regulation during pathogenetic process of VWND. In order to explore the function of LcCD82a, we purified the recombinant protein of LcCD82a-L and LcCD82a-S. The bacterial agglutination and apoptosis function analysis showed that LcCD82a may involve in extracellular bacterial recognition, agglutination, and at the same time participate in the process of antigen presentation and induction of cell apoptosis. Collectively, our studies demonstrate that LcCD82a plays a crucial role in regulating apoptosis and antimicrobial immunity.

Paralichthys olivaceus MLKL-mediated necroptosis is activated by RIPK1/3 and involved in anti-microbial immunity.

Necroptosis is a type of proinflammatory programmed necrosis essential for innate immunity. The receptor interacting protein kinases 1/3 (RIPK1/3) and the substrate mixed lineage kinase domain-like protein (MLKL) are core components of the necroptotic axis. The activation and immunological function of necroptosis in fish remain elusive. Herein, we studied the function and activation of RIPK1/3 (PoRIPK1/3) and MLKL (PoMLKL) in teleost Paralichthys olivaceus. Bacterial infection increased the expression of RIPK1/3 and MLKL. The N-terminal four-helix bundle (4HB) domain of PoMLKL exhibited necroptosis-inducing activity, and the C-terminal pseudokinase domain exerted auto-inhibitory effect on the 4HB domain. PoRIPK3 was capable of phosphorylating the T360/S361 residues in the PoMLKL C-terminal domain and initiated necroptosis, and this necroptosis-inducing activity was enhanced by PoRIPK1. PoRIPK1/3 interacted with PoMLKL in a manner that depended on the RIP homotypic interaction motif (RHIM), and deletion of RHIM from PoRIPK1/3 led to the dissociation of PoRIPK1/3 with PoMLKL. Inhibition of PoMLKL-mediated necroptosis increased Edwardsiella tarda infection in fish cells and tissues, and led to significantly enhanced lethality of the host. Taken together, these results revealed the activation mechanism of PoRIPK1/3-PoMLKL signaling pathway and the immunological function of necroptosis in the immune defense of teleost.

Single-cell multi-omics reveal stage of differentiation and trajectory-dependent immunity-related gene expression patterns in human erythroid cells.

The role of Erythroid cells in immune regulation and immunosuppression is one of the emerging topics in modern immunology that still requires further clarification as Erythroid cells from different tissues and different species express different immunoregulatory molecules. In this study, we performed a thorough investigation of human bone marrow Erythroid cells from adult healthy donors and adult acute lymphoblastic leukemia patients using the state-of-the-art single-cell targeted proteomics and transcriptomics via BD Rhapsody and cancer-related gene copy number variation analysis via NanoString Sprint Profiler. We found that human bone marrow Erythroid cells express the ARG1, LGALS1, LGALS3, LGALS9, and C10orf54 (VISTA) immunosuppressive genes, CXCL5, CXCL8, and VEGFA cytokine genes, as well as the genes involved in antimicrobial immunity and MHC Class II antigen presentation. We also found that ARG1 gene expression was restricted to the single erythroid cell cluster that we termed ARG1-positive Orthochromatic erythroblasts and that late Erythroid cells lose S100A9 and gain MZB1 gene expression in case of acute lymphoblastic leukemia. These findings show that steady-state erythropoiesis bone marrow Erythroid cells express myeloid signature genes even without any transdifferentiating stimulus like cancer.

Dynamic MAIT Cell Recovery after Severe COVID-19 Is Transient with Signs of Heterogeneous Functional Anomalies.

Mucosal-associated invariant T (MAIT) cells are an abundant population of unconventional T cells in humans and play important roles in immune defense against microbial infections. Severe COVID-19 is associated with strong activation of MAIT cells and loss of these cells from circulation. In the present study, we investigated the capacity of MAIT cells to recover after severe COVID-19. In longitudinal paired analysis, MAIT cells initially rebounded numerically and phenotypically in most patients at 4 mo postrelease from the hospital. However, the rebounding MAIT cells displayed signs of persistent activation with elevated expression of CD69, CD38, and HLA-DR. Although MAIT cell function was restored in many patients, a subgroup displayed a predominantly PD-1high functionally impaired MAIT cell pool. This profile was associated with poor expression of IFN-γ and granzyme B in response to IL-12 + L-18 and low levels of polyfunctionality. Unexpectedly, although the overall T cell counts recovered, normalization of the MAIT cell pool failed at 9-mo follow-up, with a clear decline in MAIT cell numbers and a further increase in PD-1 levels. Together, these results indicate an initial transient period of inconsistent recovery of MAIT cells that is not sustained and eventually fails. Persisting MAIT cell impairment in previously hospitalized patients with COVID-19 may have consequences for antimicrobial immunity and inflammation and could potentially contribute to post-COVID-19 health problems.

African swine fever virus E120R inhibited cGAS‐STING‐mediated IFN‐β and NF‐κB pathways

AbstractAfrican swine fever (ASF) is an acute and severe contagious disease triggered by the African swine fever virus (ASFV), which severely threatens the global swine industry. At present, no safe and efficacious vaccine has been provided to prevent and control this disease. The pathogenesis and immune evasion mechanism of ASFV are still unknown, which seriously hinders the development of safe and effective ASF vaccines. Certain proteins of ASFV involved in immunosuppression helped to evade the host innate immune response. The cGAS‐STING signaling pathway is important to the innate immune system. It induces the production of type I interferons (IFNs) and other cytokines by recognizing cytoplasmic DNA, mediating antimicrobial innate immunity through type I IFN, and nuclear factor‐κB (NF‐κB) pathways. In the present study, E120R, a late‐phase expression protein and a key virulent factor of ASFV inhibited cGAS‐STING mediated promoter activities of IFN‐β and NF‐κB in HEK293T cells. The ectopic expression of E120R down‐regulated IFN‐β pathway by targeting interferon regulatory factor 3 (IRF3) and p65, inhibited the phosphorylation of STING, and further inhibited the phosphorylation of TANK‐binding kinase 1 (TBK1) and IRF3, with no significant effects on p65 phosphorylation. Additionally, E120R also inhibited the NF‐κB pathways by inhibiting the nuclear translocation of p50 and p65, which was mediated by Sendai virus (SeV). Further, the study showed that the 61–80 amino acids sites in the C‐terminal domain of E120R were crucial for these functions. In conclusion, our work preliminarily elucidated a novel mechanism of inhibiting host innate immune response by ASFV E120R, which will provide a new target for the ASFV live gene deletion vaccine development and the theoretical basis for ASFV prevention.

Exogenous alpha-linolenic acid and Vibrio parahaemolyticus induce EPA and DHA levels mediated by delta-6 desaturase to enhance shrimp immunity

Globally, penaeid shrimp are the most farmed and traded aquatic organisms, although they are easily susceptible to microbial pathogens. Moreover, there is a desire to increase the nutritional value of shrimp, especially the levels of n-3 polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which also possess immunomodulatory and anti-inflammatory properties. Some aquatic animals can synthesize EPA and DHA from dietary plant-sourced alpha-linolenic acid (ALA), but penaeid shrimps' ability to synthesize these n-3 PUFAs is unknown. Here, molecular biology techniques, including gas chromatography–mass spectrometry, qPCR, ELISA, etc., were used to demonstrate that exogenous ALA or Vibrio parahaemolyticus could modulate EPA and DHA levels and immune genes in Penaeus vannamei by inducing key enzymes involved in n-3 PUFAs biosynthesis, such as delta desaturases and elongation of very long-chain fatty acid (ELOVLs). Most importantly, knockdown or inhibition of ∆6 desaturase significantly decreased EPA and DHA levels and immune gene expression even with exogenous ALA treatment, consequently affecting shrimp antibacterial immunity and survival. This study provides new insight into the potential of P. vannamei to synthesize n-3 PUFAs from exogenous ALA or upon bacteria challenge, which could be leveraged to increase their nutritional content and antimicrobial immunity.