Viral infection. Prevention and cure of rotavirus infection via TLR5/NLRC4-mediated production of IL-22 and IL-18

Identification and functional characterization of interleukin-22 (IL-22) in orange-spotted grouper (Epinephelus coioides)

In mammals, IL-22 is considered as a critical cytokine regulating of immunity and homeostasis at barrier surfaces. Although IL-22 have been functional characterization in different species of fish, the studies about distinct responses of IL-22 in different organs/tissues/cell types is rather limited. Here, we identified and cloned IL-22 gene (named as Ec-IL-22) from grouper (Epinephelus coioides). Ec-IL-22 gene was detected in all orangs/tissues examined, and was induced in intestine, gill, spleen, head kidney, and primary head kidney/intestine leukocytes following the stimulation of LPS and poly (I:C), as well as Vibrio harveyi and Singapore grouper iridovirus infection (SGIV). In addition, the stimulation of DSS could induce the expression of Ec-IL-22 in intestine and primary leukocytes from intestine. Importantly, the treatment of recombinant Ec-IL-22 induced the mRNA level of proinflammatory cytokines in primary intestine/head kidney leukocytes. The present results improve the understanding of expression patterns and functional characteristics of fish IL-22 in different organs/tissues/cell types.

Epigenetic control of microglial immune responses

Microglia, the major population of brain-resident macrophages, are now recognized as a heterogeneous population comprising several cell subtypes with different (so far mostly supposed) functions in health and disease. A number of studies have performed molecular characterization of these different microglial activation states over the last years making use of "omics" technologies, that is transcriptomics, proteomics and, less frequently, epigenomics profiling. These approaches offer the possibility to identify disease mechanisms, discover novel diagnostic biomarkers, and develop new therapeutic strategies. Here, we focus on epigenetic profiling as a means to understand microglial immune responses beyond what other omics methods can offer, that is, revealing past and present molecular responses, gene regulatory networks and potential future response trajectories, and defining cell subtype-specific disease relevance through mapping non-coding genetic variants. We review the current knowledge in the field regarding epigenetic regulation of microglial identity and function, provide an exemplary analysis that demonstrates the advantages of performing joint transcriptomic and epigenomic profiling of single microglial cells and discuss how comprehensive epigenetic analyses may enhance our understanding of microglial pathophysiology.

Trained immunity: General and emerging concepts

Over the past decade, compelling evidence has unveiled previously overlooked adaptive characteristics of innate immune cells. Beyond their traditional role in providing short, non-specific protection against pathogens, innate immune cells can acquire antigen-agnostic memory, exhibiting increased responsiveness to secondary stimulation. This long-term de-facto innate immune memory, also termed trained immunity, is mediated through extensive metabolic rewiring and epigenetic modifications. While the upregulation of trained immunity proves advantageous in countering immune paralysis, its overactivation contributes to the pathogenesis of autoinflammatory and autoimmune disorders. In this review, we present the latest advancements in the field of innate immune memory followed by a description of the fundamental mechanisms underpinning trained immunity generation and different cell types that mediate it. Furthermore, we explore its implications for various diseases and examine current limitations and its potential therapeutic targeting in immune-related disorders.

Limosilactobacillus reuteri L26 BiocenolTM and its exopolysaccharide: Their influence on rotavirus-induced immune molecules in enterocyte-like cells

This study aimed to evaluate the immunomodulatory effect of the probiotic Limosilactobacillus reuteri L26 BiocenolTM (L26) and its purified exopolysaccharide (EPS) with respect to antiviral innate immune response. In our experiment, we used porcine epithelial IPEC-J2 cells as a model of the intestinal barrier in a homologous infection by porcine Rotavirus A strain OSU6 (RVA). The production of selected molecules of non-specific humoral immunity was evaluated at the mRNA level. The EPS alone significantly increased the level of interferon λ3 (IFN-λ3) mRNA in the non-infected IPEC-J2 cells (P < 0.001). We also tested whether the treatment of IPEC-J2 cells by L26 or EPS influences the replication of RVA by virus titration and real-time PCR. We found that a pre-treatment in combination with subsequent continuous stimulation has no influence on the RVA replication. However, both treatments significantly decreased the RVA-induced production of IFN-λ3 (P < 0.05) and the "SOS" cytokine interleukin 6 (IL-6; P < 0.01), already at the transcription level. In addition, the EPS treatment resulted in significantly increased IL-10 mRNA in the RVA-infected cells. In summary, we assume an immunoregulatory potential of L. reuteri L26 BiocenolTM and its EPS in the local intestinal antiviral immune response.

Tissue-specific features of innate lymphoid cells in antiviral defense

Innate lymphocytes (ILCs) rapidly respond to and protect against invading pathogens and cancer. ILCs include natural killer (NK) cells, ILC1s, ILC2s, ILC3s, and lymphoid tissue inducer (LTi) cells and include type I, type II, and type III immune cells. While NK cells have been well recognized for their role in antiviral immunity, other ILC subtypes are emerging as players in antiviral defense. Each ILC subset has specialized functions that uniquely impact the antiviral immunity and health of the host depending on the tissue microenvironment. This review focuses on the specialized functions of each ILC subtype and their roles in antiviral immune responses across tissues. Several viruses within infection-prone tissues will be highlighted to provide an overview of the extent of the ILC immunity within tissues and emphasize common versus virus-specific responses.

Meeting the Challenge of Controlling Viral Immunopathology

The mission of this review is to identify immune-damaging participants involved in antiviral immunoinflammatory lesions. We argue these could be targeted and their activity changed selectively by maneuvers that, at the same time, may not diminish the impact of components that help resolve lesions. Ideally, we need to identify therapeutic approaches that can reverse ongoing lesions that lack unwanted side effects and are affordable to use. By understanding the delicate balance between immune responses that cause tissue damage and those that aid in resolution, novel strategies can be developed to target detrimental immune components while preserving the beneficial ones. Some strategies involve rebalancing the participation of immune components using various approaches, such as removing or blocking proinflammatory T cell products, expanding regulatory cells, restoring lost protective cell function, using monoclonal antibodies (moAb) to counteract inhibitory molecules, and exploiting metabolic differences between inflammatory and immuno-protective responses. These strategies can help reverse ongoing viral infections. We explain various approaches, from model studies and some clinical evidence, that achieve innate and adaptive immune rebalancing, offering insights into potential applications for controlling chronic viral-induced lesions.

Mechanism of Qizhen decoction-mediated maturation of DC cells to activate the IL-12/JAK2/STAT4 pathway to sensitise PD-1 inhibitors in the treatment of colorectal cancer

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicine has been utilized to treat colorectal cancer (CRC). Qizhen decoction (QZD), a potential compound prescription of traditional Chinese medicine, possesses multiple biological activities. It has been used to treat CRC in clinical practice and has been proven to be effective.

AIM OF THE STUDY

To investigate the impact of QZD supported by intestinal flora in combination with PD-1 inhibitor on colorectal cancer, and to elucidate the mechanism by which QZD enhances the sensitivity of PD-1 inhibitor against colorectal cancer.

MATERIALS AND METHODS

Observation of Intestinal Flora Mediating the Effect of QZD Combined with PD-1 Inhibitor in the Treatment of Colorectal Cancer. We used Flow cytometry and qPCR to detect the effect of QZD combined with PD-1 inhibitor on the activation of effector T cells in a wild mouse model of colorectal cancer. In wild and germ-free mouse models, the differences in inflammatory factors, pathological change, body mass, colorectal length, and tumour load were observed. In the study of the mechanism of QZD combined with PD-1 inhibitor in the treatment of colorectal cancer, the study evaluated the abundance of Akkermansia, the phenotypes of effector T cells and DC cells, as well as inflammatory factors in each group of mice to determine whether Akkermansia played a role in activating DC cells. Based on the JAK2/TYK2/STAT4 pathway, the mechanism of PD-1 inhibitor sensitisation by QZD in colorectal cancer was further investigated.

RESULTS

We found that QZD combined with PD-1 inhibitor could improve the therapeutic effect on colorectal cancer by inducing more critical immune functions. QZD promotes increased Akkermansia abundance in the gut. Akkermansia promotes maturation of DC cells, and mature DC cells activate the IL-12/JAK2/STAT4 pathway, which significantly activates effector T cells. Akkermansia is key to QZD combined with PD-1 inhibitor-mediated immunity exerting a therapeutic effect on colorectal cancer.

CONCLUSION

The mechanism of action of the QZD sensitizing PD-1 inhibitor is to promote the maturation of DC cells to release IL-12 and activate the JAK2/STAT4 pathway to induce effector T cell activation by increasing the abundance of Akkermansia.

Mucosal TLR5 activation controls healthspan and longevity

Addressing age-related immunological defects through therapeutic interventions is essential for healthy aging, as the immune system plays a crucial role in controlling infections, malignancies, and in supporting tissue homeostasis and repair. In our study, we show that stimulating toll-like receptor 5 (TLR5) via mucosal delivery of a flagellin-containing fusion protein effectively extends the lifespan and enhances the healthspan of mice of both sexes. This enhancement in healthspan is evidenced by diminished hair loss and ocular lens opacity, increased bone mineral density, improved stem cell activity, delayed thymic involution, heightened cognitive capacity, and the prevention of pulmonary lung fibrosis. Additionally, this fusion protein boosts intestinal mucosal integrity by augmenting the surface expression of TLR5 in a certain subset of dendritic cells and increasing interleukin-22 (IL-22) secretion. In this work, we present observations that underscore the benefits of TLR5-dependent stimulation in the mucosal compartment, suggesting a viable strategy for enhancing longevity and healthspan.

Microbial sensing in the intestine

The gut microbiota plays a key role in host health and disease, particularly through their interactions with the immune system. Intestinal homeostasis is dependent on the symbiotic relationships between the host and the diverse gut microbiota, which is influenced by the highly co-evolved immune-microbiota interactions. The first step of the interaction between the host and the gut microbiota is the sensing of the gut microbes by the host immune system. In this review, we describe the cells of the host immune system and the proteins that sense the components and metabolites of the gut microbes. We further highlight the essential roles of pattern recognition receptors (PRRs), the G protein-coupled receptors (GPCRs), aryl hydrocarbon receptor (AHR) and the nuclear receptors expressed in the intestinal epithelial cells (IECs) and the intestine-resident immune cells. We also discuss the mechanisms by which the disruption of microbial sensing because of genetic or environmental factors causes human diseases such as the inflammatory bowel disease (IBD).

Interleukin-22 and acute pancreatitis: A review

Acute pancreatitis (AP) is one of the most common gastrointestinal diseases, and it is divided into 3 types according to its severity:mild acute pancreatitis, moderately severe acute pancreatitis, and severe acute pancreatitis. The mortality in severe acute pancreatitis is approximately 15% to 30% due to multiorgan dysfunction and the lack of specific treatment. Interleukin-22 (IL-22) is a member of the Interleukin-10 family, and it can activate several downstream signaling pathways by binding to its receptor complex, thus it is involved in cell differentiation, proliferation, and apoptosis. Some studies have reported the elevated level of IL-22 in patients with AP, which suggests IL-22 may be involved in the pathogenesis of AP. And many studies have shown that IL-22 had a protective effect against AP. This article reviews the characteristics and mechanism of IL-22 and its role in AP to provide insight into the treatment of AP.

Immunomodulation by Enteric Viruses

Enteric viruses display intricate adaptations to the host mucosal immune system to successfully reproduce in the gastrointestinal tract and cause maladies ranging from gastroenteritis to life-threatening disease upon extraintestinal dissemination. However, many viral infections are asymptomatic, and their presence in the gut is associated with an altered immune landscape that can be beneficial or adverse in certain contexts. Genetic variation in the host and environmental factors including the bacterial microbiota influence how the immune system responds to infections in a remarkably viral strain-specific manner. This immune response, in turn, determines whether a given virus establishes acute versus chronic infection, which may have long-lasting consequences such as susceptibility to inflammatory disease. In this review, we summarize our current understanding of the mechanisms involved in the interaction between enteric viruses and the immune system that underlie the impact of these ubiquitous infectious agents on our health.

Controlling viral inflammatory lesions by rebalancing immune response patterns

In this review, we discuss a variety of immune modulating approaches that could be used to counteract tissue-damaging viral immunoinflammatory lesions which typify many chronic viral infections. We make the point that in several viral infections the lesions can be largely the result of one or more aspects of the host response mediating the cell and tissue damage rather than the virus itself being directly responsible. However, within the reactive inflammatory lesions along with the pro-inflammatory participants there are also other aspects of the host response that may be acting to constrain the activity of the damaging components and are contributing to resolution. This scenario should provide the prospect of rebalancing the contributions of different host responses and hence diminish or even fully control the virus-induced lesions. We identify several aspects of the host reactions that influence the pattern of immune responsiveness and describe approaches that have been used successfully, mainly in model systems, to modulate the activity of damaging participants and which has led to lesion control. We emphasize examples where such therapies are, or could be, translated for practical use in the clinic to control inflammatory lesions caused by viral infections.

Know your neighbors: microbial recognition at the intestinal barrier and its implications for gut homeostasis and inflammatory bowel disease

Intestinal epithelial cells (IECs) perform several physiological and metabolic functions at the epithelial barrier. IECs also play an important role in defining the overall immune functions at the mucosal region. Pattern recognition receptors (PRRs) on the cell surface and in other cellular compartments enable them to sense the presence of microbes and microbial products in the intestinal lumen. IECs are thus at the crossroads of mediating a bidirectional interaction between the microbial population and the immune cells present at the intestinal mucosa. This communication between the microbial population, the IECs and the underlying immune cells has a profound impact on the overall health of the host. In this review, we focus on the various PRRs present in different cellular compartments of IECs and discuss the recent developments in the understanding of their role in microbial recognition. Microbial recognition and signaling at the epithelial barrier have implications in the maintenance of intestinal homeostasis, epithelial barrier function, maintenance of commensals, and the overall tolerogenic function of PRRs in the gut mucosa. We also highlight the role of an aberrant microbial sensing at the epithelial barrier in the pathogenesis of inflammatory bowel disease (IBD) and the development of colorectal cancer.

Targeting Inflammasome Activation in Viral Infection: A Therapeutic Solution?

Inflammasome activation is exclusively involved in sensing activation of innate immunity and inflammatory response during viral infection. Accumulating evidence suggests that the manipulation of inflammasome assembly or its interaction with viral proteins are critical factors in viral pathogenesis. Results from pilot clinical trials show encouraging results of NLRP3 inflammasome suppression in reducing mortality and morbidity in SARS-CoV-2-infected patients. In this article, we summarize the up-to-date understanding of inflammasomes, including NLRP3, AIM2, NLRP1, NLRP6, and NLRC4 in various viral infections, with particular focus on RNA viruses such as SARS-CoV-2, HIV, IAV, and Zika virus and DNA viruses such as herpes simplex virus 1. We also discuss the current achievement of the mechanisms involved in viral infection-induced inflammatory response, host defense, and possible therapeutic solutions.

Interferon-λ3 alleviates intestinal epithelium injury induced by porcine rotavirus in mice

Interferons are a group of glycoproteins that are expressed in various cell types in their inflammatory responses to infections. In this study, we explored the protective effects of porcine interferon-λ3 (PIFN-λ3) on intestinal inflammation and injury in mice induced by porcine rotavirus (PRV). BALB/c mice were administrated by PIFN-λ3 or phosphate buffer solution (PBS) for three days prior to PRV infection. We show that PRV infection caused acute inflammatory responses in mice, as indicated by increases in serum concentrations of inflammatory cytokines such as the interlukin-1β (IL-1β), interlukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) (P < 0.05). However, PIFN-λ3 administration not only decreased their concentrations but also elevated the concentrations of immunoglobulin (Ig) M and IgG in the PRV challenged mice (P < 0.05). PRV infection significantly decreased the jejunal villus height and the ratio of villus height to crypt depth (V/C); however, PIFN-λ3 treatment significantly elevated the villus height and the abundance of tight junction protein ZO-1 in the jejunum (P < 0.05). Moreover, PIFN-λ3 decreased the replication of PRV in the jejunal epithelium, but significantly increased the abundance of sIgA and the activities of maltase and sucrase in the PRV-challenged mice (P < 0.05). Interestingly, PIFN-λ3 elevated the expression levels of sodium/glucose cotransporter 1 (SGLT1) and mucin 2 (MUC2) in the PRV-challenged mice (P < 0.05). Moreover, PIFN-λ3 significantly increased the expression levels of IL-10, signal transducer and activator of transcription 1 (STAT1), and critical interferon-stimulated genes such as the 2'-5' oligoadenylate synthetase-like 1 (OASL1), interferon-induced protein with tetratricopeptide repeats 1 (IFIT1) and radical S-adenosyl methionine domain containing 2 (RSAD2) in the jejunum upon PRV infection (P < 0.05). The anti-virus and anti-inflammatory effect of PIFN-λ3 should make it an attractive candidate to prevent various pathogen-induced bowel diseases.

Bacterial flagellin is a dominant, stable innate immune activator in the gastrointestinal contents of mice and rats

Intestinal contents comprise the largest repository of immunogenic ligands of microbial origin. We undertook this study to assess the predominant microbe-associated molecular patterns (MAMPs) present therein and the receptors) that mediate the innate immune responses to them. Here, we demonstrated that intestinal contents from conventional, but not germ-free, mice and rats triggered robust innate immune responses in vitro and in vivo. Such immune responses were abrogated in the absence of either myeloid differentiation factor 88 (MyD88) or Toll-like receptor (TLR) 5, but not TLR4, suggesting that the stimuli was flagellin (i.e., protein subunit of flagella that drives bacterial motility). Accordingly, pre-treating intestinal extracts with proteinase, thereby degrading flagellin, was sufficient to block their ability to activate innate immune responses. Taken together, this work serves to underscore flagellin as a major, heat-stable and bioactive MAMP in the intestinal content that confers this milieu strong potential to trigger innate immune responses.

Segmented filamentous bacteria impede rotavirus infection via retinoic acid receptor-mediated signaling

Prevention of rotavirus (RV) infection by gut-resident segmented filamentous bacteria (SFB) is an example of the influence of gut microbiota composition on enteric viral infection. Yet, the mechanism by which SFB prevents RV infection is poorly understood. A recent report that SFB colonization of germfree mice generates retinoic acid (RA) thus activating RA receptor (RAR) signaling, which protected against Citrobacter rodentium infection, prompted us to investigate whether this pathway might contribute to SFB's protection against RV infection. Colonization of conventional mice by SFB indeed increased intestinal RA levels and direct administration of RA partially mimicked the protection against RV infection conferred by SFB. Moreover, blockade of RAR signaling eliminated SFB's protection against RV infection. Blockade of RAR signaling did not impact RV infection in the absence of SFB, nor did it alter the protection against RV infection conferred by bacterial flagellin, which in contrast to SFB, is dependent upon IL-22 signaling. SFB/RA-mediated prevention of RV infection was associated with an RA-dependent increase in enterocyte migration, consistent with the notion that enhanced anoikis is the ultimate means by which SFB, IL-22, and RA impede RV infection.

The mechanisms and cross-protection of trained innate immunity

In recent years, the traditional cognition of immunological memory being specific to adaptive immunity has been challenged. Innate immunity can mount enhanced responsiveness upon secondary stimulation, and a phenomenon is termed trained innate immunity. Trained innate immunity is orchestrated by distinct metabolic and epigenetic reprogramming in both circulating myeloid cells and myeloid progenitor cells in bone marrow, leading to long-term resistance to related and non-related pathogens infections. The induction of trained innate immunity can also polarize innate immune cells towards a hyperresponsive phenotype in the tumor microenvironment to exert antitumor effects. This review will discuss the current understanding of innate immune memory and the mechanisms during the induction of innate immunity, including signaling pathways, metabolic changes, and epigenetic rewriting. We also provide an overview of cross-protection against infectious diseases and cancers based on trained innate immunity.

NLRC4-mediated activation of CD1c+ DC contributes to perpetuation of synovitis in rheumatoid arthritis

The individual contribution of specific myeloid subsets such as CD1c+ conventional DC (cDC) to perpetuation of rheumatoid arthritis (RA) pathology remains unclear. In addition, the specific innate sensors driving pathogenic activation of CD1c+ cDC in patients with RA and their functional implications have not been characterized. Here, we assessed phenotypical, transcriptional, and functional characteristics of CD1c+ and CD141+ cDC and monocytes from the blood and synovial fluid of patients with RA. Increased levels of CCR2 and the IgG receptor CD64 on circulating CD1c+ cDC was associated with the presence of this DC subset in the synovial membrane in patients with RA. Moreover, synovial CD1c+ cDC are characterized by increased expression of proinflammatory cytokines and high abilities to induce pathogenic IFN-γ+IL-17+CD4+ T cells in vitro. Finally, we identified the crosstalk between Fcγ receptors and NLRC4 as a potential molecular mechanism mediating pathogenic activation, CD64 upregulation, and functional specialization of CD1c+ cDC in response to dsDNA-IgG in patients with RA.

Promiscuous Inflammasomes: The False Dichotomy of RNA/DNA Virus-Induced Inflammasome Activation and Pyroptosis

It is well-known that viruses activate various inflammasomes, which can initiate the programmed cell death pathway known as pyroptosis, subsequently leading to cell lysis and release of inflammatory cytokines IL-1β and IL-18. This pathway can be triggered by various sensors, including, but not limited to, NLRP3, AIM2, IFI16, RIG-I, and NLRC4. Many viruses are known either to activate or inhibit inflammasomes as a part of the innate immune response or as a mechanism of pathogenesis. Early research in the field of virus-induced pyroptosis suggested a dichotomy, with RNA viruses activating the NLRP3 inflammasome and DNA viruses activating the AIM2 inflammasome. More recent research has shown that this dichotomy may not be as distinct as once thought. It seems many viruses activate multiple inflammasome sensors. Here, we detail which viruses fit the dichotomy as well as many that appear to defy this clearly false dichotomy. It seems likely that most, if not all, viruses activate multiple inflammasome sensors, and future research should focus on expanding our understanding of inflammasome activation in a variety of tissue types as well as virus activation of multiple inflammasomes, challenging biases that stemmed from early literature in this field. Here, we review primarily research performed on human viruses but also include details regarding animal viruses whenever possible.

Rotavirus Infection in Swine: Genotypic Diversity, Immune Responses, and Role of Gut Microbiome in Rotavirus Immunity

Rotaviruses (RVs) are endemic in swine populations, and all swine herds certainly have a history of RV infection and circulation. Rotavirus A (RVA) and C (RVC) are the most common among all RV species reported in swine. RVA was considered most prevalent and pathogenic in swine; however, RVC has been emerging as a significant cause of enteritis in newborn piglets. RV eradication from swine herds is not practically achievable, hence producers’ mainly focus on minimizing the production impact of RV infections by reducing mortality and diarrhea. Since no intra-uterine passage of immunoglobulins occur in swine during gestation, newborn piglets are highly susceptible to RV infection at birth. Boosting lactogenic immunity in gilts by using vaccines and natural planned exposure (NPE) is currently the only way to prevent RV infections in piglets. RVs are highly diverse and multiple RV species have been reported from swine, which also contributes to the difficulties in preventing RV diarrhea in swine herds. Human RV-gut microbiome studies support a link between microbiome composition and oral RV immunogenicity. Such information is completely lacking for RVs in swine. It is not known how RV infection affects the functionality or structure of gut microbiome in swine. In this review, we provide a detailed overview of genotypic diversity of swine RVs, host-ranges, innate and adaptive immune responses to RVs, homotypic and heterotypic immunity to RVs, current methods used for RV management in swine herds, role of maternal immunity in piglet protection, and prospects of investigating swine gut microbiota in providing immunity against rotaviruses.

“The Good, the Bad and the Ugly”: Interplay of Innate Immunity and Inflammation

Innate immunity recognizes microorganisms through certain invariant receptors named pattern recognition receptors (PRRs) by sensing conserved pathogen-associated molecular patterns (PAMPs). Their recognition activates several signaling pathways that lead the transcription of inflammatory mediators, contributing to trigger a very rapid inflammatory cascade aiming to contain the local infection as well as activating and instructing the adaptive immunity in a specific and synchronized immune response according to the microorganism. Inflammation is a coordinated process involving the secretion of cytokines and chemokines by macrophages and neutrophils leading to the migration of other leukocytes along the endothelium into the injured tissue. Sustained inflammatory responses can cause deleterious effects by promoting the development of autoimmune disorders, allergies, cancer, and other immune pathologies, while weak signals could exacerbate the severity of the disease. Therefore, PRR-mediated signal transduction must be tightly regulated to maintain host immune homeostasis. Innate immunity deficiencies and strategies deployed by microbes to avoid inflammatory responses lead to an altered immune response that allows the pathogen to proliferate causing death or uncontrolled inflammation. This review analyzes the complexity of the immune response at the beginning of the disease focusing on COVID-19 disease and the importance of unraveling its mechanisms to be considered when treating diseases and designing vaccines.

Cyprinid-specific duplicated membrane TLR5 senses dsRNA as functional homodimeric receptors

Membrane-embedded Toll-like receptor 5 (TLR5) functions as a homodimer to detect bacterial flagellin. Cyprinid grass carp (Ctenopharyngodon idella) encodes two TLR5 genes, CiTLR5a and CiTLR5b. Here, we show that cyprinid TLR5a and TLR5b homodimers unexpectedly bind the dsRNA analog poly(I:C) and regulate interferon (IFN) response in early endosomes and lysosomes. Although TLR5 homodimers also bind flagellin, an immune response to flagellin is only triggered by TLR5a/b heterodimer. Moreover, we demonstrate that two TLR5 paralogs have opposite effects on antiviral response: CiTLR5a slightly promotes and powerfully maintains, whereas CiTLR5b remarkably inhibits virus replication. We show that the ectodomain of CiTLR5 is required for dsRNA-induced IFN signaling, and we map the key poly(I:C) binding sites to G240 for CiTLR5a and to N547 for CiTLR5b. Furthermore, we reveal that differential N-glycosylation of CiTLR5a/b affects dsRNA-IFN signaling but has no role in flagellin-mediated NF-κB induction, with paralog-specific roles for CiTLR5a-T101 and corresponding CiTLR5b-I99. Moreover, we provide evidence that the ability to sense dsRNA represents a neofunctionalization specific for membrane-bound TLR5 in cyprinid, bridging viral and bacterial immune responses.

Fiction and Facts about BCG Imparting Trained Immunity against COVID-19

The Bacille Calmette-Guérin or BCG vaccine, the only vaccine available against Mycobacterium tuberculosis can induce a marked Th1 polarization of T-cells, characterized by the antigen-specific secretion of IFN-γ and enhanced antiviral response. A number of studies have supported the concept of protection by non-specific boosting of immunity by BCG and other microbes. BCG is a well-known example of a trained immunity inducer since it imparts ‘non-specific heterologous’ immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for the recent pandemic. SARS-CoV-2 continues to inflict an unabated surge in morbidity and mortality around the world. There is an urgent need to devise and develop alternate strategies to bolster host immunity against the coronavirus disease of 2019 (COVID-19) and its continuously emerging variants. Several vaccines have been developed recently against COVID-19, but the data on their protective efficacy remains doubtful. Therefore, urgent strategies are required to enhance system immunity to adequately defend against newly emerging infections. The concept of trained immunity may play a cardinal role in protection against COVID-19. The ability of trained immunity-based vaccines is to promote heterologous immune responses beyond their specific antigens, which may notably help in defending against an emergency situation such as COVID-19 when the protective ability of vaccines is suspicious. A growing body of evidence points towards the beneficial non-specific boosting of immune responses by BCG or other microbes, which may protect against COVID-19. Clinical trials are underway to consider the efficacy of BCG vaccination against SARS-CoV-2 on healthcare workers and the elderly population. In this review, we will discuss the role of BCG in eliciting trained immunity and the possible limitations and challenges in controlling COVID-19 and future pandemics.

Re-Examining Rotavirus Innate Immune Evasion: Potential Applications of the Reverse Genetics System

Rotaviruses represent one of the most successful pathogens in the world, with high infectivity and efficient transmission between the young of many animal species, including humans. To overcome host defenses, rotaviruses have evolved a plethora of strategies to effectively evade the innate immune response, establish initial infection in the small intestine, produce progeny, and shed into the environment. Previously, studying the roles and relative contributions of specific rotaviral factors in innate immune evasion had been challenging without a plasmid-only reverse genetics system. Although still in its infancy, current reverse genetics technology will help address important research questions regarding rotavirus innate immune evasion, host range restriction, and viral pathogenesis. In this review, we summarize the current knowledge about the antiviral host innate immune defense mechanisms, countermeasures of rotavirus-encoded factors, and strategies to better understand these interactions using the rotavirus reverse genetics system.

Identifying enhancers of innate immune signaling as broad-spectrum antivirals active against emerging viruses

The increasingly frequent outbreaks of pathogenic viruses have underlined the urgent need to improve our arsenal of antivirals that can be deployed for future pandemics. Innate immunity is a powerful first line of defense against pathogens, and compounds that boost the innate response have high potential to act as broad-spectrum antivirals. Here, we harnessed localization-dependent protein-complementation assays (called Alpha Centauri) to measure the nuclear translocation of interferon regulatory factors (IRFs), thus providing a readout of innate immune activation following viral infection that is applicable to high-throughput screening of immunomodulatory molecules. As proof of concept, we screened a library of kinase inhibitors on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and identified Gilteritinib as a powerful enhancer of innate responses to viral infection. This immunostimulatory activity of Gilteritinib was found to be dependent on the AXL-IRF7 axis and results in a broad and potent antiviral activity against unrelated RNA viruses.

Mechanisms involved in controlling RNA virus-induced intestinal inflammation

Gastroenteritis is inflammation of the lining of stomach and intestines and causes significant morbidity and mortality worldwide. Many viruses, especially RNA viruses are the most common cause of enteritis. Innate immunity is the first line of host defense against enteric RNA viruses and virus-induced intestinal inflammation. The first layer of defense against enteric RNA viruses in the intestinal tract is intestinal epithelial cells (IECs), dendritic cells and macrophages under the intestinal epithelium. These innate immune cells express pathogen-recognition receptors (PRRs) for recognizing enteric RNA viruses through sensing viral pathogen-associated molecular patterns (PAMPs). As a result of this recognition type I interferon (IFN), type III IFN and inflammasome activation occurs, which function cooperatively to clear infection and reduce viral-induced intestinal inflammation. In this review, we summarize recent findings about mechanisms involved in enteric RNA virus-induced intestinal inflammation. We will provide an overview of the enteric RNA viruses, their RNA sensing mechanisms by host PRRs, and signaling pathways triggered by host PRRs, which shape the intestinal immune response to maintain intestinal homeostasis.

Nasally delivered interferon-λ protects mice against infection by SARS-CoV-2 variants including Omicron

Although vaccines and monoclonal antibody countermeasures have reduced the morbidity and mortality associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, variants with constellations of mutations in the spike gene jeopardize their efficacy. Accordingly, antiviral interventions that are resistant to further virus evolution are needed. The host-derived cytokine interferon lambda (IFN-λ) has been proposed as a possible treatment based on studies in human coronavirus 2019 (COVID-19) patients. Here, we show that IFN-λ protects against SARS-CoV-2 B.1.351 (Beta) and B.1.1.529 (Omicron) variants in three strains of conventional and human ACE2 transgenic mice. Prophylaxis or therapy with nasally delivered IFN-λ2 limits infection of historical or variant SARS-CoV-2 strains in the upper and lower respiratory tracts without causing excessive inflammation. In the lung, IFN-λ is produced preferentially in epithelial cells and acts on radio-resistant cells to protect against SARS-CoV-2 infection. Thus, inhaled IFN-λ may have promise as a treatment for evolving SARS-CoV-2 variants that develop resistance to antibody-based countermeasures.

Immunity to enteric viruses

Pathogenic enteric viruses are a major cause of morbidity and mortality, particularly among children in developing countries. The host response to enteric viruses occurs primarily within the mucosa, where the intestinal immune system must balance protection against pathogens with tissue protection and tolerance to harmless commensal bacteria and food. Here, we summarize current knowledge in natural immunity to enteric viruses, highlighting specialized features of the intestinal immune system. We further discuss how knowledge of intestinal anti-viral mechanisms can be translated into vaccine development with particular focus on immunization in the oral route. Research reveals that the intestine is a complex interface between enteric viruses and the host where environmental factors influence susceptibility and immunity to infection, while viral infections can have lasting implications for host health. A deeper mechanistic understanding of enteric anti-viral immunity with this broader context can ultimately lead to better vaccines for existing and emerging viruses.

Rotavirus-Induced Expansion of Antigen-Specific CD8 T Cells Does Not Require Signaling via TLR3, MyD88 or the Type I Interferon Receptor

Rotavirus (RV) infection induces strong adaptive immunity. While protection from reinfection requires humoral immunity, initial clearance of infection depends on cytotoxic CD8 T cells. Type I classical dendritic cells (cDC1) excel at CD8 T cell induction through cross-presentation and are essential for optimal cytotoxicity towards RV. Upon sensing of infection-induced innate immune signals through pattern recognition receptors (PRRs), cumulating in autocrine type I interferon (IFN) signaling, cDC1 mature and migrate to the draining lymph nodes (LNs), where they prime adaptive immune cells. To analyze which PRR pathways lead to robust cytotoxicity in the context of RV infection, we measured RV-specific CD8 T cell priming in mice deficient for Toll-like receptor 3 (TLR3), recognizing double-stranded RNA, or for MyD88, the adapter for all other TLRs and IL-1 family cytokines. Individual TLR3- and MyD88-mediated signaling was not required for the priming of CD8 T cell responses to RV and neither deficiency impacted on RV clearance. Surprisingly, the accumulation of RV-specific CD8 T cells was also not altered in the absence of type I IFN signaling, while their ability to produce IFNγ and granzyme were blunted. Together, this suggests a substantial level of redundancy in the sensing of RV infection and the translation of signals into protective CD8 T cell immunity.

Rotavirus Interactions With Host Intestinal Epithelial Cells

Rotavirus (RV) is the foremost enteric pathogen associated with severe diarrheal illness in young children (<5years) and animals worldwide. RV primarily infects mature enterocytes in the intestinal epithelium causing villus atrophy, enhanced epithelial cell turnover and apoptosis. Intestinal epithelial cells (IECs) being the first physical barrier against RV infection employs a range of innate immune strategies to counteract RVs invasion, including mucus production, toll-like receptor signaling and cytokine/chemokine production. Conversely, RVs have evolved numerous mechanisms to escape/subvert host immunity, seizing translation machinery of the host for effective replication and transmission. RV cell entry process involve penetration through the outer mucus layer, interaction with cell surface molecules and intestinal microbiota before reaching the IECs. For successful cell attachment and entry, RVs use sialic acid, histo-blood group antigens, heat shock cognate protein 70 and cell-surface integrins as attachment factors and/or (co)-receptors. In this review, a comprehensive summary of the existing knowledge of mechanisms underlying RV-IECs interactions, including the role of gut microbiota, during RV infection is presented. Understanding these mechanisms is imperative for developing efficacious strategies to control RV infections, including development of antiviral therapies and vaccines that target specific immune system antagonists within IECs.

Bacterial and Viral Co-Infection in the Intestine: Competition Scenario and Their Effect on Host Immunity

Bacteria and viruses are both important pathogens causing intestinal infections, and studies on their pathogenic mechanisms tend to focus on one pathogen alone. However, bacterial and viral co-infections occur frequently in clinical settings, and infection by one pathogen can affect the severity of infection by another pathogen, either directly or indirectly. The presence of synergistic or antagonistic effects of two pathogens in co-infection can affect disease progression to varying degrees. The triad of bacterial–viral–gut interactions involves multiple aspects of inflammatory and immune signaling, neuroimmunity, nutritional immunity, and the gut microbiome. In this review, we discussed the different scenarios triggered by different orders of bacterial and viral infections in the gut and summarized the possible mechanisms of synergy or antagonism involved in their co-infection. We also explored the regulatory mechanisms of bacterial–viral co-infection at the host intestinal immune interface from multiple perspectives.

A homeostatic interferon-lambda response to bacterial microbiota stimulates preemptive antiviral defense within discrete pockets of intestinal epithelium

Interferon-lambda (IFN-λ) protects intestinal epithelial cells (IECs) from enteric viruses by inducing expression of antiviral IFN-stimulated genes (ISGs). Here, we find that bacterial microbiota stimulate a homeostatic ISG signature in the intestine of specific pathogen-free mice. This homeostatic ISG expression is restricted to IECs, depends on IEC-intrinsic expression of IFN-λ receptor (Ifnlr1), and is associated with IFN-λ production by leukocytes. Strikingly, imaging of these homeostatic ISGs reveals localization to pockets of the epithelium and concentration in mature IECs. Correspondingly, a minority of mature IECs express these ISGs in public single-cell RNA sequencing datasets from mice and humans. Furthermore, we assessed the ability of orally administered bacterial components to restore localized ISGs in mice lacking bacterial microbiota. Lastly, we find that IECs lacking Ifnlr1 are hyper-susceptible to initiation of murine rotavirus infection. These observations indicate that bacterial microbiota stimulate ISGs in localized regions of the intestinal epithelium at homeostasis, thereby preemptively activating antiviral defenses in vulnerable IECs to improve host defense against enteric viruses.

Interleukin-18 and COVID-19

Vulnerability to coronavirus disease (COVID)-19 varies due to differences in interferon gamma (IFNγ) immunity. We investigated whether a key modifiable interferon precursor, interleukin-18, was related to COVID-19, overall and by severity, using Mendelian randomisation. We used four established genome-wide significant genetic predictors of interleukin-18 applied to the most recent genome-wide association study of COVID-19 (June 2021) to obtain Mendelian randomisation inverse variance weighted estimates by severity, i.e. any (cases = 112 612, non-cases = 2 474 079), hospitalised (cases = 24 274, non-cases = 2 061 529) and very severe (cases = 8779, non-cases = 1 001 875) COVID-19. To be comprehensive, we also conducted an exploratory analysis for IFNγ and two related cytokines with less well-established genetic predictors, i.e. interleukin-12 and interleukin-23. Genetically predicted interleukin-18 was associated with lower risk of any COVID-19 (odds ratio (OR) 0.96 per standard deviation, 95% confidence interval (0.94–0.99, P-value 0.004)) and of very severe COVID-19 (OR 0.88, 95% CI 0.78–0.999, P-value 0.048). Sensitivity analysis and a more liberal genetic instrument selection gave largely similar results. Few genome-wide significant genetic predictors were available for IFNγ, interleukin-12 or interleukin-23, and no associations with COVID-19 were evident. Interleukin-18 could be a modifiable target to prevent COVID-19 and should be further explored in an experimental design.

The Role of Host Glycobiology and Gut Microbiota in Rotavirus and Norovirus Infection, an Update

Rotavirus (RV) and norovirus (NoV) are the leading causes of acute gastroenteritis (AGE) worldwide. Several studies have demonstrated that histo-blood group antigens (HBGAs) have a role in NoV and RV infections since their presence on the gut epithelial surfaces is essential for the susceptibility to many NoV and RV genotypes. Polymorphisms in genes that code for enzymes required for HBGAs synthesis lead to secretor or non-secretor and Lewis positive or Lewis negative individuals. While secretor individuals appear to be more susceptible to RV infections, regarding NoVs infections, there are too many discrepancies that prevent the ability to draw conclusions. A second factor that influences enteric viral infections is the gut microbiota of the host. In vitro and animal studies have determined that the gut microbiota limits, but in some cases enhances enteric viral infection. The ways that microbiota can enhance NoV or RV infection include virion stabilization and promotion of virus attachment to host cells, whereas experiments with microbiota-depleted and germ-free animals point to immunoregulation as the mechanism by which the microbiota restrict infection. Human trials with live, attenuated RV vaccines and analysis of the microbiota in responder and non-responder individuals also allowed the identification of bacterial taxa linked to vaccine efficacy. As more information is gained on the complex relationships that are established between the host (glycobiology and immune system), the gut microbiota and intestinal viruses, new avenues will open for the development of novel anti-NoV and anti-RV therapies.

DC-CTL targeting carbonic anhydrase IX gene combined with iAPA therapy in the treatment of renal cell carcinoma

INTRODUCTION

To deliver specific antigens in tumor immunotherapy, tumor cell lysates are commonly used to sensitize dendritic cells (DCs). However, the lysates possess low immunogenicity and contain many types of non-tumor-related antigens, which may induce autoimmune diseases. Tumor antigen peptides can provide high specificity but are expensive and their short half-lives limit their clinical application.

METHODS

In this study, we used adenovirus to transfer the carbonic anhydrase IX (CA9) gene into DCs to generate specificity to renal cell carcinoma (RCC) which is the most common space-occupying lesion in humans. Inhibition of antigen presentation attenuators (iAPA) technology was also used to enhance the DC delivery capacity. Finally, DCs were co-cultured with cytotoxic T-lymphocytes (CTLs) and the anti-tumor effects were evaluated.

RESULTS

The results showed that the CA9-DC-CTLs possessed a high specificity to CA9-positive cells and showed stronger anti-tumor activity than GFP-DC-CTLs both in vitro and in vivo.

DISCUSSION

These findings may suggest a novel treatment option for RCC.

Trained Immunity as an Adaptive Branch of Innate Immunity

The concept of trained immunity has become one of the most interesting and potentially commercially and clinically relevant ideas of current immunology. Trained immunity is realized by the epigenetic reprogramming of non-immunocompetent cells, primarily monocytes/macrophages and natural killer (NK) cells, and is less specific than adaptive immunity; therefore, it may cross-protect against other infectious agents. It remains possible, however, that some of the observed changes are simply caused by increased levels of immune reactions resulting from supplementation with immunomodulators, such as glucan. In addition, the question of whether we can talk about trained immunity in cells with a life span of only few days is still unresolved.

Toward a universal influenza virus vaccine: Some cytokines may fulfill the request

The influenza virus annually causes widespread damages to the health and economy of the global community. Vaccination is currently the most crucial strategy in reducing the number of patients. Genetic variations, the high diversity of pandemic viruses, and zoonoses make it challenging to select suitable strains for annual vaccine production. If new pandemic viruses emerge, it will take a long time to produce a vaccine according to the new strains. In the present study, intending to develop a universal influenza vaccine, new bicistronic DNA vaccines were developed that expressed NP or NPm antigen with one of modified IL-18/ IL-17A/ IL-22 cytokine adjuvants. NPm is a mutant form of the antigen that has the ability for cytoplasmic accumulation. In order to investigate and differentiate the role of each of the components of Th1, Th2, Th17, and Treg cellular immune systems in the performance of vaccines, Treg competent and Treg suppressed mouse groups were used. Mice were vaccinated with Foxp3-FC immunogen to produce Treg suppressed mouse groups. The potential of the vaccines to stimulate the immune system was assessed by IFN-γ/IL-17A Dual FluoroSpot. The vaccine's ability to induce humoral immune response was determined by measuring IgG1, IgG2a, and IgA-specific antibodies against the antigen. Kinetics of Th1, Th2, and Th17 cellular immune responses after vaccination, were assessed by evaluating the expression changes of IL-17A, IFN-γ, IL-18, IL-22, IL-4, and IL-2 cytokines by semi-quantitative real-time RT-PCR. To assess the vaccines' ability to induce heterosubtypic immunity, challenge tests with homologous and heterologous viruses were performed and then the virus titer was measured in the lungs of animals. Evaluation of the data obtained from this study showed that the DNA-vaccines coding NPm have more ability to induces a potent cross-cellular immune response and protective immunity than DNA-vaccines coding NP. Although the use of IL-18/ IL-17A/ IL-22 genetic adjuvants enhanced immune responses and protective immunity, Administration of NPm in combination with modified IL-18 (Igk-mIL18-IgFC) induced the most effective immunity in Treg competent mice group.

Rotavirus susceptibility of antibiotic-treated mice ascribed to diminished expression of interleukin-22

The commensal microbiota regulates susceptibility to enteric pathogens by fine-tuning mucosal innate immune responses, but how susceptibility to enteric viruses is shaped by the microbiota remains incompletely understood. Past reports have indicated that commensal bacteria may either promote or repress rotavirus replication in the small intestine of mice. We now report that rotavirus replicated more efficiently in the intestines of germ-free and antibiotic-treated mice compared to animals with an unmodified microbiota. Antibiotic treatment also facilitated rotavirus replication in type I and type III interferon (IFN) receptor-deficient mice, revealing IFN-independent proviral effects. Expression of interleukin-22 (IL-22) was strongly diminished in the intestine of antibiotic-treated mice. Treatment with exogenous IL-22 blocked rotavirus replication in microbiota-depleted wild-type and Stat1-/- mice, demonstrating that the antiviral effect of IL-22 in animals with altered microbiome is not dependent on IFN signaling. In antibiotic-treated animals, IL-22-induced a specific set of genes including Fut2, encoding fucosyl-transferase 2 that participates in the biosynthesis of fucosylated glycans which can mediate rotavirus binding. Interestingly, IL-22 also blocked rotavirus replication in antibiotic-treated Fut2-/- mice. Furthermore, IL-22 inhibited rotavirus replication in antibiotic-treated mice lacking key molecules of the necroptosis or pyroptosis pathways of programmed cell death. Taken together, our results demonstrate that IL-22 determines rotavirus susceptibility of antibiotic-treated mice, yet the IL-22-induced effector molecules conferring rotavirus resistance remain elusive.

Pathogenesis of murine astrovirus in experimentally infected mice

Astroviruses are often associated with gastrointestinal diseases in mammals and birds. Murine astrovirus (MuAstV) is frequently detected in laboratory mice. Previous studies on MuAstV in mice did not report any symptoms or lesions. However, little information is available regarding its pathogenicity in immunodeficient mice. Therefore, in this study, we experimentally infected germ-free NOD.Cg-PrkdcscidIl2rgtm1Sug/ShiJic (NOG) mice, which are severely immunodeficient, with MuAstV. Germ-free mice were used for experimental infection to eliminate the effects of intestinal bacteria. Mice in each group were then necropsied and subjected to PCR for MuAstV detection, MuAstV RNA quantification in each organ, and histopathological examination at 4 and 28 days post inoculation (DPI). Tissue samples from the small intestine were examined by transmission electron microscopy. No symptoms or abnormalities were detected in any mice during necropsy. The MuAstV concentration was highest in the lower small intestine, where it increased approximately 8-fold from 4 to 28 DPI. Transmission electron microscopy revealed circular virus particles of approximately 25 nm in diameter in the cytoplasm of the villous epithelial cells of the lower small intestine. Histopathological examination did not reveal any abnormalities, such as atrophy, in the intestinal villi. Our results suggest that MuAstV proliferates in the villous epithelial cells of the lower small intestine and has weak pathogenicity.

Pattern recognition receptors in health and diseases

Pattern recognition receptors (PRRs) are a class of receptors that can directly recognize the specific molecular structures on the surface of pathogens, apoptotic host cells, and damaged senescent cells. PRRs bridge nonspecific immunity and specific immunity. Through the recognition and binding of ligands, PRRs can produce nonspecific anti-infection, antitumor, and other immunoprotective effects. Most PRRs in the innate immune system of vertebrates can be classified into the following five types based on protein domain homology: Toll-like receptors (TLRs), nucleotide oligomerization domain (NOD)-like receptors (NLRs), retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), C-type lectin receptors (CLRs), and absent in melanoma-2 (AIM2)-like receptors (ALRs). PRRs are basically composed of ligand recognition domains, intermediate domains, and effector domains. PRRs recognize and bind their respective ligands and recruit adaptor molecules with the same structure through their effector domains, initiating downstream signaling pathways to exert effects. In recent years, the increased researches on the recognition and binding of PRRs and their ligands have greatly promoted the understanding of different PRRs signaling pathways and provided ideas for the treatment of immune-related diseases and even tumors. This review describes in detail the history, the structural characteristics, ligand recognition mechanism, the signaling pathway, the related disease, new drugs in clinical trials and clinical therapy of different types of PRRs, and discusses the significance of the research on pattern recognition mechanism for the treatment of PRR-related diseases.

Trained Innate Immunity in Hematopoietic Stem Cell and Solid Organ Transplantation

Although significant progress has been made to improve short-term survival of transplant patients, long-term acceptance of allografts in solid organ and hematopoietic stem cell (HSC) transplantation is still a significant challenge. Current therapeutics for preventing or treating allograft rejection rely on potent immunosuppressive drugs that primarily target T cells of the adaptive immune response. Promising advances in transplant immunology have highlighted the importance of innate immune responses in allograft acceptance and rejection. Recent studies have demonstrated that innate immune cells are capable of mediating memory-like responses during inflammation, a term known as trained innate immunity. In this process, innate immune cells, such as macrophages and monocytes, undergo metabolic and epigenetic changes in response to a primary stimulus with a pathogen or their products that result in faster and more robust responses to a secondary stimulus. There is also some evidence to suggest that innate immune cells or their progenitors may be more anti-inflammatory after initial stimulation with appropriate agents, such as helminth products. Although this phenomenon has primarily been studied in the context of infection, there is emerging evidence to suggest that it could play a vital role in transplantation rejection and tolerance. Mechanisms of training innate immune cells and their progenitors in the bone marrow are therefore attractive targets for mediating long-term solid organ and HSC transplant tolerance. In this review, we highlight the potential role of proinflammatory and anti-inflammatory mechanisms of trained innate immunity in solid organ and HSC transplantation.

Diversity and dynamism of IgA-microbiota interactions

IgA mediates microbial homeostasis at the intestinal mucosa. Within the gut, IgA acts in a context-dependent manner to both prevent and promote bacterial colonization and to influence bacterial gene expression, thus providing exquisite control of the microbiota. IgA-microbiota interactions are highly diverse across individuals and populations, yet the factors driving this variation remain poorly understood. In this Review, we summarize evidence for the host, bacterial and environmental factors that influence IgA-microbiota interactions. Recent advances have helped to clarify the antigenic specificity and immune selection of intestinal IgA and have highlighted the importance of microbial glycan recognition. Furthermore, emerging evidence suggests that diet and nutrition play an important role in shaping IgA recognition of the microbiota. IgA-microbiota interactions are disrupted during both overnutrition and undernutrition and may be altered dynamically in response to diet, with potential implications for host health. We situate this research in the context of outstanding questions and future directions in order to better understand the fascinating paradigm of IgA-microbiota homeostasis.

ROS/RNS Balancing, Aerobic Fermentation Regulation and Cell Cycle Control - a Complex Early Trait ('CoV-MAC-TED') for Combating SARS-CoV-2-Induced Cell Reprogramming

In a perspective entitled 'From plant survival under severe stress to anti-viral human defense' we raised and justified the hypothesis that transcript level profiles of justified target genes established from in vitro somatic embryogenesis (SE) induction in plants as a reference compared to virus-induced profiles can identify differential virus signatures that link to harmful reprogramming. A standard profile of selected genes named 'ReprogVirus' was proposed for in vitro-scanning of early virus-induced reprogramming in critical primary infected cells/tissues as target trait. For data collection, the 'ReprogVirus platform' was initiated. This initiative aims to identify in a common effort across scientific boundaries critical virus footprints from diverse virus origins and variants as a basis for anti-viral strategy design. This approach is open for validation and extension. In the present study, we initiated validation by experimental transcriptome data available in public domain combined with advancing plant wet lab research. We compared plant-adapted transcriptomes according to 'RegroVirus' complemented by alternative oxidase (AOX) genes during de novo programming under SE-inducing conditions with in vitro corona virus-induced transcriptome profiles. This approach enabled identifying a major complex trait for early de novo programming during SARS-CoV-2 infection, called 'CoV-MAC-TED'. It consists of unbalanced ROS/RNS levels, which are connected to increased aerobic fermentation that links to alpha-tubulin-based cell restructuration and progression of cell cycle. We conclude that anti-viral/anti-SARS-CoV-2 strategies need to rigorously target 'CoV-MAC-TED' in primary infected nose and mouth cells through prophylactic and very early therapeutic strategies. We also discuss potential strategies in the view of the beneficial role of AOX for resilient behavior in plants. Furthermore, following the general observation that ROS/RNS equilibration/redox homeostasis is of utmost importance at the very beginning of viral infection, we highlight that 'de-stressing' disease and social handling should be seen as essential part of anti-viral/anti-SARS-CoV-2 strategies.

Serum level of interleukin-22 in patients with cutaneous warts: A case-control study

BACKGROUND

Warts are viral cutaneous infections caused by human papilloma virus (HPV), presented by verrucous growth over the skin surface. The immune response is considered to play a crucial role in HPV clearance. It depends on intact cellular immunity including natural killer (NK) cell and cytotoxic T cells. It has been clarified that T-helper (Th) 1 cytokines (interleukin (IL)-2, interferon-γ, and tumor necrosis factor-a) and IL-17 are involved in HPV clearance. IL-22 is one of IL-10 family of cytokines produced by NK cells, Th1, Th17, and Th22 cells. In the skin, IL-22 reduces keratinocyte cornification and enhances keratinocyte production of antimicrobial peptides. IL-22 overexpression has been demonstrated in various viral infections and skin inflammatory disorders.

AIM

The aim of this study was to assess serum levels of IL-22 in patients with warts and its association with their different clinical characteristics.

METHODS

The study included 20 patients with warts and 20 control subjects. Serum concentration of IL-22 was measured by enzyme-linked immune sorbent assay.

RESULTS

Serum levels of IL-22 were significantly higher in patients with warts than in control subjects (P < .001). The levels were significantly higher in patients with recurrent warts after prior treatment than in patients with first-time warts (P = .007). Moreover, a significant positive correlation was detected between serum levels of IL-22 and the number of warts (P = .017).

CONCLUSION

Serum level of IL-22 was elevated in patients with warts. Thus, IL-22 may have a crucial role in the antiviral immune response against this infection.

Enterocytes, fibroblasts and myeloid cells synergize in anti-bacterial and anti-viral pathways with IL22 as the central cytokine

IL22 is an important cytokine involved in the intestinal defense mechanisms against microbiome. By using ileum-derived organoids, we show that the expression of anti-microbial peptides (AMPs) and anti-viral peptides (AVPs) can be induced by IL22. In addition, we identified a bacterial and a viral route, both leading to IL22 production by T cells, but via different pathways. Bacterial products, such as LPS, induce enterocyte-secreted SAA1, which triggers the secretion of IL6 in fibroblasts, and subsequently IL22 in T cells. This IL22 induction can then be enhanced by macrophage-derived TNFα in two ways: by enhancing the responsiveness of T cells to IL6 and by increasing the expression of IL6 by fibroblasts. Viral infections of intestinal cells induce IFNβ1 and subsequently IL7. IFNβ1 can induce the expression of IL6 in fibroblasts and the combined activity of IL6 and IL7 can then induce IL22 expression in T cells. We also show that IL22 reduces the expression of viral entry receptors (e.g. ACE2, TMPRSS2, DPP4, CD46 and TNFRSF14), increases the expression of anti-viral proteins (e.g. RSAD2, AOS, ISG20 and Mx1) and, consequently, reduces the viral infection of neighboring cells. Overall, our data indicates that IL22 contributes to the innate responses against both bacteria and viruses.