Toll-like receptors regulation of viral infection and disease

Recent Insights into the Molecular Mechanisms of the Toll-like Receptor Response to Influenza Virus Infection

Influenza A viruses (IAVs) pose a significant global threat to human health. A tightly controlled host immune response is critical to avoid any detrimental effects of IAV infection. It is critical to investigate the association between the response of Toll-like receptors (TLRs) and influenza virus. Because TLRs may act as a double-edged sword, a balanced TLR response is critical for the overall benefit of the host. Consequently, a thorough understanding of the TLR response is essential for targeting TLRs as a novel therapeutic and prophylactic intervention. To date, a limited number of studies have assessed TLR and IAV interactions. Therefore, further research on TLR interactions in IAV infection should be conducted to determine their role in host-virus interactions in disease causation or clearance of the virus. Although influenza virus vaccines are available, they have limited efficacy, which should be enhanced to improve their efficacy. In this study, we discuss the current status of our understanding of the TLR response in IAV infection and the strategies adopted by IAVs to avoid TLR-mediated immune surveillance, which may help in devising new therapeutic or preventive strategies. Furthermore, recent advances in the use of TLR agonists as vaccine adjuvants to enhance influenza vaccine efficacy are discussed.

Pharmacological effects and mechanism of Kaihoujian Throat Spray (children's type) in the treatment of pediatric acute pharyngitis and tonsillitis

Context

Kaihoujian Throat Spray children's type (KHJSC) is a Chinese medicine prescription for treating pediatric acute pharyngitis and tonsillitis (APT). However, its relevant mechanisms remain unclear.

Objective

To investigate the pharmacological effects of KHJSC on APT in vitro and in vivo, and explore the possible mechanism and target proteins.

Materials and methods

The antiviral and antibacterial effects in vitro were evaluated by IC50 and MICs. Thirty-six Japanese white rabbits were averagely divided into control group, model group, amoxicillin group and 3 dose groups of KHJSC (720, 540 and 360 μL/kg/d). The model rabbits were injected with β-hemolytic Streptococcus solution into the tonsils for 2 consecutive days. KHJSC treatment started on the third day. The whole blood, serum, tonsil tissues and pharyngeal mucosa tissues were collected for routine blood tests, proteomic, ELISA and other tests on the sixth day.

Results

The IC50 of KHJSC on HCoV-229E, influenza PR8 and Ad3 were 1.99, 1.99 and 4.49 mg/mL, respectively; MICs of MDR-PA, MRSA and β-hemolytic Streptococcus were 350, 350, and 175 mg/mL. KHJSC markedly decreased the number of white blood cells, lymphocytes, neutrophils, and the level of IL-1β, IL-5, IL-6, IL-18, TNF-α and MCP-1; increased the content of IL-2 and IFN-γ. Proteomic analysis and ELISA revealed that PI3K-Akt signaling pathway, NF-κB signaling pathway and Toll-like receptor signaling pathway were the potential mechanisms of KHJSC against APT.

Discussion and conclusion

These results provided the reference and scientific basis for the application of KHJSC in clinic and further mechanisms study.

Chimeric vaccine design against the epidemic Langya Henipavirus using immunoinformatics and validation via immune simulation approaches

In July 2022, a new virus called Langya virus (LayV) was discovered in China in patients who had a fever. This virus is a type of Henipavirus (HNV) and is considered a potential threat as it could spread from animals to humans. It causes respiratory disease with symptoms including fever, coughing, and fatigue and is closely linked to two other henipaviruses that are known to infect humans, namely Hendra and Nipah viruses. These viruses may cause fatal respiratory illnesses. Investigators believe that the LayV is spread by shrews, and may have infected humans directly or via an intermediary species. Thus, the use of vaccines or immunizations against LayV is an alternate strategy for disease prevention. In this study, we employed various immunoinformatics methods to predict B cell, HTL and T cell epitopes from the LayV proteome in order to find the most promising candidate for a LayV vaccine. The most potent epitopes that are immunogenic and non-allergenic were joined with each other through suitable linkers. Human β-defensin 2 was employed as an adjuvant to increase the immunogenicity of the vaccine construct. The final sequence of a multi-epitope vaccine construct was modelled for docking with TLRs. Concisely, our results suggest that the docked complexes of vaccine-TLRs seemed to be stable. Additionally, in silico cloning was done using E. coli as the host in order to validate the expression of our designed vaccine construct. The GC content of 54.39% and CAI value of 0.94 revealed that the vaccine component expresses efficiently in the host. This study presents the novel vaccine construct for LayV which will be essential for further experimental validations to confirm the immunogenicity and safety of the proposed vaccine structure, and eventually to treat HNV-related diseases.

Toll-like Receptor Response to Human Immunodeficiency Virus Type 1 or Co-Infection with Hepatitis B or C Virus: An Overview

Toll-like receptors (TLRs) are evolutionarily conserved pattern recognition receptors that play important roles in the early detection of pathogen-associated molecular patterns and shaping innate and adaptive immune responses, which may influence the consequences of infection. Similarly to other viral infections, human immunodeficiency virus type 1 (HIV-1) also modulates the host TLR response; therefore, a proper understanding of the response induced by human HIV-1 or co-infection with hepatitis B virus (HBV) or hepatitis C virus (HCV), due to the common mode of transmission of these viruses, is essential for understanding HIV-1 pathogenesis during mono- or co-infection with HBV or HCV, as well as for HIV-1 cure strategies. In this review, we discuss the host TLR response during HIV-1 infection and the innate immune evasion mechanisms adopted by HIV-1 for infection establishment. We also examine changes in the host TLR response during HIV-1 co-infection with HBV or HCV; however, this type of study is extremely scarce. Moreover, we discuss studies investigating TLR agonists as latency-reverting agents and immune stimulators towards new strategies for curing HIV. This understanding will help develop a new strategy for curing HIV-1 mono-infection or co-infection with HBV or HCV.

Nasopharyngeal epithelial cells from patients with coronavirus disease 2019 express abnormal levels of Toll-like receptors

Aberrant activation of the immune system has been attributed with etiology and pathogenesis of coronavirus disease 2019 (COVID-19). Here, the transcript levels of toll-like receptors (TLRs) were measured in the nasopharyngeal epithelial cells obtained from COVID-19 patients to assess the involvement of these molecules in the clinical outcome of COVID-19 patients. Nasopharyngeal swab samples were used to obtain epithelial cells from 120 COVID-19 patients and 100 healthy controls. COVID-19 cases were classified into those having clinical symptoms/needing for hospitalization, having clinical symptoms/not needing for hospitalization, and those without clinical symptoms‌. The mRNA expression levels of TLRs were measured in the nasopharyngeal epithelial cells. Overall, mRNA expression of TLR1, TLR2, TLR4, and TLR6 was significantly higher in COVID-19 cases compared to controls. The mRNA expression of TLRs were all higher significantly in the samples from COVID-19 patients having clinical symptoms and needing hospitalization as well as in those with clinical symptoms/not needing for hospitalization in comparison to controls. TLR expression was significantly higher in those with clinical symptoms/needing for hospitalization and those with clinical symptoms/not needing for hospitalization compared to COVID-19 cases without clinical symptoms. In cases with clinical symptoms/needing for hospitalization and those with clinical symptoms/not needing for hospitalization, there was a correlation between TLR expression and clinicopathological findings. In conclusion, aberrant expression of TLRs in the nasopharyngeal epithelial cells from COVID-19 cases may predict the severity of the diseases and necessity for supportive cares in the hospital.

Synonymous nucleotide changes drive papillomavirus evolution

Papillomaviruses have been evolving alongside their hosts for at least 450 million years. This review will discuss some of the insights gained into the evolution of this diverse family of viruses. Papillomavirus evolution is constrained by pervasive purifying selection to maximize viral fitness. Yet these viruses need to adapt to changes in their environment, e.g., the host immune system. It has long been known that these viruses evolved a codon usage that doesn't match the infected host. Here we discuss how papillomavirus genomes evolve by acquiring synonymous changes that allow the virus to avoid detection by the host innate immune system without changing the encoded proteins and associated fitness loss. We discuss the implications of studying viral evolution, lifecycle, and cancer progression.

Immunoinformatics-guided designing and in silico analysis of epitope-based polyvalent vaccines against multiple strains of human coronavirus (HCoV)

OBJECTIVES

The group of human coronaviruses (HCoVs) consists of some highly pathogenic viruses that have caused several outbreaks in the past. The newly emerged strain of HCoV, the SARS-CoV-2 is responsible for the recent global pandemic that has already caused the death of hundreds of thousands of people due to the lack of effective therapeutic options.

METHODS

In this study, immunoinformatics methods were used to design epitope-based polyvalent vaccines which are expected to be effective against four different pathogenic strains of HCoV i.e., HCoV-OC43, HCoV-SARS, HCoV-MERS, and SARS-CoV-2.

RESULTS

The constructed vaccines consist of highly antigenic, non-allergenic, nontoxic, conserved, and non-homologous T-cell and B-cell epitopes from all the four viral strains. Therefore, they should be able to provide strong protection against all these strains. Protein-protein docking was performed to predict the best vaccine construct. Later, the MD simulation and immune simulation of the best vaccine construct also predicted satisfactory results. Finally, in silico cloning was performed to develop a mass production strategy of the vaccine.

CONCLUSION

If satisfactory results are achieved in further in vivo and in vitro studies, then the vaccines designed in this study might be effective as preventative measures against the selected HCoV strains.

CD169 (Siglec-1) as a Robust Human Cell Biomarker of Toll-Like Receptor 9 Agonist Immunotherapy

Immunotherapy is a promising therapeutic area in cancer and chronic viral infections. An important component of immunotherapy in these contexts is the activation of innate immunity. Here we investigate the potential for CD169 (Siglec 1) expression on monocytes to serve as a robust biomarker for activation of innate immunity and, particular, as a proxy for IFN-α production. Specifically, we investigated the effects of Toll-like receptor 9 agonism with MGN1703 (lefitolimod) across experimental conditions ex vivo, in humanized mice, and in clinical trial participants. Ex vivo we observed that the percentage of classical monocytes expressing CD169 increased dramatically from 10% pre-stimulation to 97% 24 hrs after MGN1703 stimulation (p<0.0001). In humanized NOG mice, we observed prominent upregulation of the proportions of monocytes expressing CD169 after two doses of MGN1703 where 73% of classical monocytes were CD169 positive in bone marrow following MGN1703 treatment vs 19% in vehicle treated mice (p=0.0159). Finally, in a clinical trial in HIV-infected individuals receiving immunotherapy treatment with MGN1703, we observed a uniform upregulation of CD169 on monocytes after dosing with 97% of classical monocytes positive for CD169 (p=0.002). Hence, in this comprehensive evaluation ex vivo, in an animal model, and in a clinical trial, we find increases in the percentage of CD169 positive monocytes to be a reliable and robust biomarker of immune activation following TLR9 agonist treatment.

Understanding the Immune System in Fetal Protection and Maternal Infections during Pregnancy

The fetal-maternal immune system determines the fate of pregnancy. The trophoblast cells not only give an active response against external stimuli but are also involved in secreting most of the cytokines. These cells have an essential function in fetal acceptance or fetal rejection. Other immune cells also play a pivotal role in carrying out a successful pregnancy. The disruption in this mechanism may lead to harmful effects on pregnancy. The placenta serves as an immune barrier in fetus protection against invading pathogens. Once the infections prevail, they may localize in placental and fetal tissues, and the presence of inflammation due to cytokines may have detrimental effects on pregnancy. Moreover, some pathogens are responsible for congenital fetal anomalies and affect almost all organs of the developing fetus. This review article is designed to address the bacterial and viral infections that threaten pregnancy and their possible outcomes. Moreover, training of the fetal immune system against the exposure of infections and the role of CD49a + NK cells in embryonic development will also be highlighted.

Expression profiles of toll like receptors, MHC and cytokine genes along with viral load in organs of ducklings infected with an Indian isolate of duck enteritis virus

A comprehensive study on the pathogenicity and host immune response was conducted in White Pekin ducklings after experimental infection with an Indian isolate of duck enteritis virus (DEV). The virus was found to be highly pathogenic and pantropic, which rapidly multiplied in various organs, mainly in the spleen and liver showing higher viral load with severe pathological lesions and caused 100% mortality. Expression profiles of immune gene transcripts in tissues (liver, spleen, brain) revealed upregulation of proinflammatory cytokines IFN-α, IFN- β, IL-1β, IL-6 and also iNOS with stimulation of TLRs (TLR-2, 3, 21). IFN-α was robustly upregulated (p < 0.05) especially in liver, might be playing role in antiviral innate immunity. Further, massive upregulation of MHC class-I (p < 0.01), expression of Th1 cytokines (IFN-γ & IL-2) and certain Th2 cytokines (IL-4 & IL-10) suggests stimulation of cell mediated as well as humoral immunity. To our knowledge, we are reporting first time about the robust upregulation of MHC class-I in spleen, liver and brain along with expression of certain cytokines in the peripheral blood mononuclear cells (PBMCs) during experimental DEV infection.

Coevolutionary Analysis Implicates Toll-Like Receptor 9 in Papillomavirus Restriction

Upon infection, DNA viruses can be sensed by pattern recognition receptors (PRRs), leading to the activation of type I and III interferons to block infection. Therefore, viruses must inhibit these signaling pathways, avoid being detected, or both. Papillomavirus virions are trafficked from early endosomes to the Golgi apparatus and wait for the onset of mitosis to complete nuclear entry. This unique subcellular trafficking strategy avoids detection by cytoplasmic PRRs, a property that may contribute to the establishment of infection. However, as the capsid uncoats within acidic endosomal compartments, the viral DNA may be exposed to detection by Toll-like receptor 9 (TLR9). In this study, we characterized two new papillomaviruses from bats and used molecular archeology to demonstrate that their genomes altered their nucleotide compositions to avoid detection by TLR9, providing evidence that TLR9 acts as a PRR during papillomavirus infection. Furthermore, we showed that TLR9, like other components of the innate immune system, is under evolutionary selection in bats, providing the first direct evidence for coevolution between papillomaviruses and their hosts. Finally, we demonstrated that the cancer-associated human papillomaviruses show a reduction in CpG dinucleotides within a TLR9 recognition complex.

Toll-Like Receptors as a Therapeutic Target in the Era of Immunotherapies

Toll-like receptors (TLRs) are the pattern recognition receptors, which are activated by foreign and host molecules in order to initiate the immune response. They play a crucial role in the regulation of innate immunity, and several studies have shown their importance in bacterial, viral, and fungal infections, autoimmune diseases, and cancers. The consensus view from an immunological perspective is that TLR agonists can serve either as a possible therapeutic agent or as a vaccine adjuvant toward cancers or infectious diseases and that TLR inhibitors may be a promising approach to the treatment of autoimmune diseases, some cancers, bacterial, and viral infections. These notions are based on the fact that TLR agonists stimulate the secretion of proinflammatory cytokines and in general, the development of proinflammatory responses. Some of the TLR-based inhibitory agents have shown to be efficacious in preclinical models and have now entered clinical trials. Therefore, TLRs seem to hold the potential to serve as a perfect target in the era of immunotherapies. We offer a perspective on TLR-based therapeutics that sheds light on their usefulness and on combination therapies. We also highlight various therapeutics that are in the discovery phase or in clinical trials.

Lower peripheral blood Toll-like receptor 3 expression is associated with an unfavorable outcome in severe COVID-19 patients

The role of innate immunity in COVID-19 is not completely understood. Therefore, this study explored the impact of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection on the expression of Pattern Recognition Receptors (PRRs) in peripheral blood cells and their correlated cytokines. Seventy-nine patients with severe COVID-19 on admission, according to World Health Organization (WHO) classification, were divided into two groups: patients who needed mechanical ventilation and/or deceased (SEVERE, n = 50) and patients who used supplementary oxygen but not mechanical ventilation and survived (MILD, n = 29); a control group (CONTROL, n = 17) was also enrolled. In the peripheral blood, gene expression (mRNA) of Toll-like receptors (TLRs) 3, 4, 7, 8, and 9, retinoic-acid inducible gene I (RIGI), NOD-like receptor family pyrin domain containing 3 (NLRP3), interferon alpha (IFN-α), interferon beta (IFN-β), interferon gamma (IFN-γ), interferon lambda (IFN-λ), pro-interleukin(IL)-1β (pro-IL-1β), and IL-18 was determined on admission, between 5–9 days, and between 10–15 days. Circulating cytokines in plasma were also measured. When compared to the COVID-19 MILD group, the COVID-19 SEVERE group had lower expression of TLR3 and overexpression of TLR4.

Cell type-specific roles of PAR1 in Coxsackievirus B3 infection

Protease-activated receptor 1 (PAR1) is widely expressed in humans and mice, and is activated by a variety of proteases, including thrombin. Recently, we showed that PAR1 contributes to the innate immune response to viral infection. Mice with a global deficiency of PAR1 expressed lower levels of CXCL10 and had increased Coxsackievirus B3 (CVB3)-induced myocarditis compared with control mice. In this study, we determined the effect of cell type-specific deletion of PAR1 in cardiac myocytes (CMs) and cardiac fibroblasts (CFs) on CVB3-induced myocarditis. Mice lacking PAR1 in either CMs or CFs exhibited increased CVB3 genomes, inflammatory infiltrates, macrophages and inflammatory mediators in the heart and increased CVB3-induced myocarditis compared with wild-type controls. Interestingly, PAR1 enhanced poly I:C induction of CXCL10 in rat CFs but not in rat neonatal CMs. Importantly, activation of PAR1 reduced CVB3 replication in murine embryonic fibroblasts and murine embryonic cardiac myocytes. In addition, we showed that PAR1 reduced autophagy in murine embryonic fibroblasts and rat H9c2 cells, which may explain how PAR1 reduces CVB3 replication. These data suggest that PAR1 on CFs protects against CVB3-induced myocarditis by enhancing the anti-viral response whereas PAR1 on both CMs and fibroblasts inhibits viral replication.

Association of Herpes simplex virus I&II infections with rs187084 SNP of TLR9 and male infertility

Since TLR9 recognises unmethylated CpG motifs in viral DNA, its polymorphisms may contribute to the susceptibility to Herpes simplex virus I&II infection. In the present study, to evaluate the role of rs187084 SNP (single nucleotide polymorphism) of TLR9 in Herpes simplex virus I&II infection and male infertility, 103 infertile and 27 fertile blood and semen samples were analysed. We assessed the micro and macro properties of semen specimens and the presence of HSV immunoglobulins. Tetra-primer ARMS PCR was used to detect SNP and to investigate the genotype distribution of TLR9-rs187084 SNPs, and the correlation between polymorphisms of TLR9 gene and male infertility. Moreover, the odds ratio (OR) and 95% confidence intervals were used to estimate the strength of the association. Based on our finding, a significant correlation was observed between HSV infection, agglutination and polymorphism (TT) under dominant (OR = 1.28, 95% CI = 0.94-1.75) and recessive (OR = 0.44, 95% CI = 0.21-0.94) models for the data, which was complied with Hardy-Weinberg equilibrium (HWE) (OR = 2.91, 95% CI = 1.02-8.30). The result showed a significant association between HSV IgM and agglutination in HSV infection (p < .001), and in addition, there were associations between alleles so that rs187084 SNP might be considered as a risk factor for the incidence of HSV infection.

Zebrafish as a Translational Model: An Experimental Alternative to Study the Mechanisms Involved in Anosmia and Possible Neurodegenerative Aspects of COVID-19?

The Coronavirus disease-2019 (COVID-19) presents a variability of clinical symptoms, ranging from asymptomatic to severe respiratory and systemic conditions. In a cohort of patients, the Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2), beyond the classical respiratory manifestations, induces anosmia. Evidence has suggested SARS-CoV-2-induced anosmia can be the result of neurodegeneration of the olfactory pathway. Neurologic symptoms associated with COVID-19 have been reported; however, the precise mechanism and possible long-lasting effects remain poorly investigated. Preclinical models are valuable tools for describing and testing new possible treatments for neurologic disorders. In this way, the zebrafish (Danio rerio) organism model represents an attractive tool in the field of neuroscience, showing economic and logistic advantages besides genetic and physiologic similarities with mammalian, including the brain structure and functions. Besides, its external embryonic development, high availability of eggs, and fast development allows easy genetic manipulation and fast replications. In the present review, we suggest that the zebrafish model can be advantageous to investigate the neurologic features of COVID-19.

Nanotechnology to the Rescue: Treatment Perspective for the Immune Dysregulation Observed in COVID-19

The study of the use of nanotechnology for drug delivery has been extensive. Nanomedical approaches for therapeutics; drug delivery in particular is superior to conventional methods in that it allows for controlled targeted delivery and release, higher stability, extended circulation time, minimal side-effects, and improved pharmacokinetic clearance (of the drug) form the body, to name a few. The magnitude of COVID-19, the current ongoing pandemic has been severe; it has caused widespread the loss of human life. In individuals with severe COVID-19, immune dysregulation and a rampant state of hyperinflammation is observed. This kind of an immunopathological response is detrimental and results in rapid disease progression, development of secondary infections, sepsis and can be fatal. Several studies have pin-pointed the reason for this immune dysregulation; deviations in the signaling pathways involved in the mediation and control of immune responses. In severe COVID-19 patients, many signaling cascades including JAK/STAT, NF-κB, MAPK/ERK, TGF beta, VEGF, and Notch signaling were found to be either upregulated or inactivated. Targeting these aberrant signaling pathways in conjunction with antiviral therapy will effectuate mitigation of the hyperinflammation, hypercytokinemia, and promote faster recovery. The science of the use of nanocarriers as delivery agents to modulate these signaling pathways is not new; it has already been explored for other inflammatory diseases and in particular, cancer therapy. Numerous studies have evaluated the efficacy and potential of nanomedical approaches to modulate these signaling pathways and have been met with positive results. A treatment regime, that includes nanotherapeutics and antiviral therapies will prove effective and holds great promise for the successful treatment of COVID-19. In this article, we review different nanomedical approaches already studied for targeting aberrant signaling pathways, the host immune response to SARS-CoV-2, immunopathology and the dysregulated signaling pathways observed in severe COVID-19 and the current treatment methods in use for targeting signaling cascades in COVID-19. We then conclude by suggesting that the use of nanomedical drug delivery systems for targeting signaling pathways can be extended to effectively target the aberrant signaling pathways in COVID-19 for best treatment results.

SARS-CoV-2 infection, COVID-19 pathogenesis, and exposure to air pollution: What is the connection?

Exposure to air pollutants has been previously associated with respiratory viral infections, including influenza, measles, mumps, rhinovirus, and respiratory syncytial virus. Epidemiological studies have also suggested that air pollution exposure is associated with increased cases of SARS-CoV-2 infection and COVID-19-associated mortality, although the molecular mechanisms by which pollutant exposure affects viral infection and pathogenesis of COVID-19 remain unknown. In this review, we suggest potential molecular mechanisms that could account for this association. We have focused on the potential effect of exposure to nitrogen dioxide (NO2 ), ozone (O3 ), and particulate matter (PM) since there are studies investigating how exposure to these pollutants affects the life cycle of other viruses. We have concluded that pollutant exposure may affect different stages of the viral life cycle, including inhibition of mucociliary clearance, alteration of viral receptors and proteases required for entry, changes to antiviral interferon production and viral replication, changes in viral assembly mediated by autophagy, prevention of uptake by macrophages, and promotion of viral spread by increasing epithelial permeability. We believe that exposure to pollutants skews adaptive immune responses toward bacterial/allergic immune responses, as opposed to antiviral responses. Exposure to air pollutants could also predispose exposed populations toward developing COIVD-19-associated immunopathology, enhancing virus-induced tissue inflammation and damage.

Immune-mediated approaches against COVID-19

The coronavirus disease-19 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The long incubation period of this new virus, which is mostly asymptomatic yet contagious, is a key reason for its rapid spread across the world. Currently, there is no worldwide-approved treatment for COVID-19. Therefore, the clinical and scientific communities have joint efforts to reduce the severe impact of the outbreak. Research on previous emerging infectious diseases have created valuable knowledge that is being exploited for drug repurposing and accelerated vaccine development. Nevertheless, it is important to generate knowledge on SARS-CoV-2 mechanisms of infection and its impact on host immunity, to guide the design of COVID-19 specific therapeutics and vaccines suitable for mass immunization. Nanoscale delivery systems are expected to play a paramount role in the success of these prophylactic and therapeutic approaches. This Review provides an overview of SARS-CoV-2 pathogenesis and examines immune-mediated approaches currently explored for COVID-19 treatments, with an emphasis on nanotechnological tools.

Expression pattern of the interferon regulatory factor family members in influenza virus induced local and systemic inflammatory responses

Type I interferon is considered to be a key cytokine in influenza virus-induced acute lung injury (ALI), in which IRF3 and IRF7 play particularly important roles. However, whether all nine members of IRF family are involved in influenza virus-induced immune response is currently unknown. In this study, we found that all members of IRF family responded to influenza virus. The IRF family expression profile seems to be related to the pathogenicity of the particular influenza virus strain. The influenza virus mainly relies on endosomal TLR signals and the positive feedback loop of IFN-I to cause either direct or indirect different expression of all IRF family members locally or systemically. Interestingly, IRF6 was somewhat different from other IRF family members during influenza virus infection. Overall, the expression profile of the IRF family may be a valuable reference for the prevention and treatment of influenza complications, which encourage further, more in-depth research.

Exploiting the reverse vaccinology approach to design novel subunit vaccines against Ebola virus

Ebola virus is a highly pathogenic RNA virus that causes the Ebola haemorrhagic fever in human. This virus is considered as one of the dangerous viruses in the world with very high mortality rate. To date, no epitope-based subunit vaccine has yet been discovered to fight against Ebola although the outbreaks of this deadly virus took many lives in the past. In this study, approaches of reverse vaccinology were utilized in combination with different tools of immunoinformatics to design subunit vaccines against Ebola virus strain Mayinga-76. Three potential antigenic proteins of this virus i.e., matrix protein VP40, envelope glycoprotein and nucleoprotein were selected to construct the subunit vaccine. The MHC class-I, MHC class-II and B-cell epitopes were determined initially and after some robust analysis i.e., antigenicity, allergenicity, toxicity, conservancy and molecular docking study, EV-1, EV-2 and EV-3 were constructed as three potential vaccine constructs. These vaccine constructs are also expected to be effective on few other strains of Ebola virus since the highly conserved epitopes were used for vaccine construction. Thereafter, molecular docking study was conducted on these vaccines and EV-1 emerged as the best vaccine construct. Afterward, molecular dynamics simulation study revealed the good performances and stability of the intended vaccine protein. Finally, codon adaptation and in silico cloning were carried out to design a possible plasmid (pET-19b plasmid vector was used) for large scale production of the EV-1 vaccine. However, further in vitro and in vivo studies might be required on the predicted vaccines for final validation.

Interplay of Cyclic GMP-AMP Synthase/Stimulator of IFN Genes and Toll-Like Receptor Nucleic Acid Sensing Pathways in Autoinflammation and Abnormal Bone Formation due to DNaseII-Deficiency

Nucleic acid (NA) sensing receptors were first described in the context of host defense. We now know that some endosomal NA sensors play a critical role in the development of systemic autoimmune diseases such as systemic lupus erythematosus, whereas cytosolic Cyclic GMP-AMP Synthase/Stimulator of IFN Genes (cGAS/STING) DNA-detecting pathway has been associated with monogenic autoinflammatory interferonopathies such as Aicardi–Goutieres and Education; collaboration; communication STING-associated vasculopathy with onset in infancy (SAVI). DNaseII hypomorphic patients and DNase^−/− IFNaR^−/− (double knockout [DKO]) mice also develop an autoinflammatory syndrome associated with an interferon signature. We now add to the description of an unusual clinical manifestation of DKO mice that involves the accrual of trabecular bone in long bone marrow and the formation of ectopic bone within the spleen. This aberrant bone formation is lost not only in STING-deficient but also in Unc93b1-deficient mice and, therefore, depends on the interplay of cells expressing cytosolic and endosomal NA sensing receptors.

The Unique Microbiome and Innate Immunity During Pregnancy

A successful pregnancy depends on not only the tolerance of the fetal immune system by the mother but also resistance against the threat of hazardous microorganisms. Infection with pathogenic microorganisms during pregnancy may lead to premature delivery, miscarriage, growth restriction, neonatal morbidity, and other adverse outcomes. Moreover, the host also has an intact immune system to avoid these adverse outcomes. It is important to note the presence of normal bacteria in the maternal reproductive tract and the principal role of the maternal-placental-fetal interaction in antimicrobial immunity. Previous studies mainly focused on maternal infection during pregnancy. However, this review summarizes the new views on the study of the maternal microbiome and expounds the innate immune defense mechanism of the maternal vagina and decidua as well as how cytotrophoblasts and syncytiotrophoblasts recognize and kill bacteria in the placenta. Fetal immune systems, thought to be weak, also exhibit an immune defense function that is indispensable for maintaining the safety of the fetus. The skin, lungs, and intestines of the fetus during pregnancy constitute the main immune barriers. These findings will provide a new understanding of the effects of normal microbial flora and how the host resists harmful microbes during pregnancy. We believe that it may also contribute to the reference on the clinical prevention and treatment of gestational infection to avoid adverse pregnancy outcomes.

Murine Leukemia Virus Exploits Innate Sensing by Toll-Like Receptor 7 in B-1 Cells To Establish Infection and Locally Spread in Mice

Lymph-borne Friend murine leukemia virus (FrMLV) exploits the sentinel macrophages in the draining popliteal lymph node (pLN) to infect highly permissive innate-like B-1 cells and establish infection in mice. The reason for FrMLV sensitivity of B-1 cells and their impact on viral spread is unknown. Here we demonstrate that Toll-like receptor 7 (TLR7) sensing and type I interferon (IFN-I) signaling in B-1 cells contribute to FrMLV susceptibility. FrMLV infection in B-1 cell-deficient mice (bumble; IκBNS dysfunctional) was significantly lower than that in the wild-type mice and was rescued by adoptive transfer of wild-type B-1 cells. This rescue of FrMLV infection in bumble mice was dependent on intact TLR7 sensing and IFN-I signaling within B-1 cells. Analyses of infected cell types revealed that the reduced infection in bumble mice was due predominantly to compromised virus spread to the B-2 cell population. Our data reveal how FrMLV exploits innate immune sensing and activation in the B-1 cell population for infection and subsequent spread to other lymphocytes.IMPORTANCE Viruses establish infection in hosts by targeting highly permissive cell types. The retrovirus Friend murine leukemia virus (FrMLV) infects a subtype of B cells called B-1 cells that permit robust virus replication. The reason for their susceptibility had remained unknown. We found that innate sensing of incoming virus and the ensuing type I interferon response within B-1 cells are responsible for their observed susceptibility. Our data provide insights into how retroviruses coevolved with the host to co-opt innate immune sensing pathways designed to fight virus infections for establishing infection. Understanding early events in viral spread can inform antiviral intervention strategies that prevent the colonization of a host.

Significance and Role of Pattern Recognition Receptors in Malignancy

Pattern recognition receptors (PRRs) are members of innate immunity, playing pivotal role in several immunological reactions. They are known to act as a bridge between innate and adaptive immunity. They are expressed on several normal cell types but have been shown with increasing frequency on/in tumor cells. Significance of this phenomenon is largely unknown, but it has been shown by several authors that they, predominantly Toll-like receptors (TLRs), act in the interest of tumor, by promotion of its growth and spreading. Preparation of artificial of TLRs ligands (agonists) paved the way to use them as a therapeutic agents for cancer, so far in a limited scale. Agonists may be combined with conventional anti-cancer modalities with apparently promising results. PRRs recognizing nucleic acids such as RIG-1 like receptors (sensing RNA) and STING (sensing DNA) constitute a novel promising approach for cancer immunotherapy.

Autophagy in Zika Virus Infection: A Possible Therapeutic Target to Counteract Viral Replication

Zika virus (ZIKV) still constitutes a public health concern, however, no vaccines or therapies are currently approved for treatment. A fundamental process involved in ZIKV infection is autophagy, a cellular catabolic pathway delivering cytoplasmic cargo to the lysosome for degradation—considered as a primordial form of innate immunity against invading microorganisms. ZIKV is thought to inhibit the Akt-mTOR signaling pathway, which causes aberrant activation of autophagy promoting viral replication and propagation. It is therefore appealing to study the role of autophagic molecular effectors during viral infection to identify potential targets for anti-ZIKV therapeutic intervention.

Opiate use inhibits TLR9 signaling pathway in vivo: possible role in pathogenesis of HIV-1 infection

The molecular mechanism of opiate use promoting HIV-1 infection is not fully understood. TLR9 is expressed in many immune cells, including monocytes, macrophages, which can recognize viruses and viral products and consequently induce the production of antiviral factors and initiate immune responses. Previous studies have shown that chronic viral infections can overcome and impair TLR9 pathway. We aimed to explore whether opiate use enhances HIV infection through inhibition of TLR9 pathway via a population-based study. A total of 200 subjects were enrolled and divided into four groups as follows: Opiate+ HIV+ (50), Opiate- HIV+ (50), Opiate+ HIV- (50), and healthy control (Opiate- HIV-, 50). All HIV-infected subjects did not receive antiretroviral therapy while they were enrolled in the study. The results showed that opiate use was associated with higher viral load and lower CD4+ T cell count. Opiate use alone led to lower expression of TLR9, IRF7, and IFN-α at the protein level in PBMCs. Combined with HIV-1 infection, opiate use resulted in lower expression of MyD88, ISG56, and MxA. In addition, morphine treatment promoted HIV-1 replication in macrophages via inhibition of TLR9 pathway. Our data reveal that opiate use plays a cofactor role in pathogenesis of HIV-1 infection through inhibition of TLR9 pathway.

Bioconjugation Approaches to Producing Subunit Vaccines Composed of Protein or Peptide Antigens and Covalently Attached Toll-Like Receptor Ligands

Traditional vaccines derived from attenuated or inactivated pathogens are effective at inducing antibody-based protective immune responses but tend to be highly reactogenic, causing notable adverse effects. Vaccines with superior safety profiles can be produced by subunit approaches, utilizing molecularly defined antigens (e.g., proteins and polysaccharides). These antigens, however, often elicit poor immunological responses, necessitating the use of adjuvants. Immunostimulatory adjuvants have the capacity to activate antigen presenting cells directly through specific receptors (e.g., Toll-like receptors (TLRs)), resulting in enhanced presentation of antigens as well as the secretion of proinflammatory chemokines and cytokines. Consequently, innate immune responses are amplified and adaptive immunity is generated. Recently, site-specific conjugation of such immunostimulatory adjuvants (e.g., TLR ligands) onto defined antigens has shown superior efficacy over unconjugated mixtures, suggesting that the development of chemically characterized immunostimulatory adjuvants and optimized approaches for their conjugation with antigens may provide a better opportunity for the development of potent, novel vaccines. This review briefly summarizes various TLR agonists utilized as immunostimulatory adjuvants and focuses on the development of techniques (e.g., recombinant, synthetic, and semisynthetic) for generating adjuvant-antigen fusion vaccines incorporating peptide or protein antigens.

Molecular characterization and expression analysis of three TLR genes in yellow catfish (Pelteobagrus fulvidraco): Responses to stimulation of Aeromonas hydrophila and TLR ligands

Toll-like receptors (TLRs) are one of the most extensively researched pattern recognition receptors (PRRs) and play an important role in the innate immune system. In this study, partial cDNA sequences of the Pf_TLR18 and Pf_TLR19 genes and complete cDNA sequence of the Pf_TLR21 gene were cloned from yellow catfish (Pelteobagrus fulvidraco). The open reading frames (ORFs) of the Pf_TLR18, Pf_TLR19 and Pf_TLR21 genes were 1956 bp, 2262 bp and 2949 bp in length, encoding 651, 753 and 982 amino acids, respectively. The Pf_TLR18 and Pf_TLR19 consist of leucine-rich repeats (LRRs), a transmembrane domain and a Toll/interleukin-I receptor domain, and the Pf_TLR21 only has LRRs and TIR domain. Homologous identity revealed that the Pf_TLR18, Pf_TLR19 and Pf_TLR21 genes have high nucleotide and protein sequence similarity with channel catfish, especially the TIR domains that exhibited the greatest conservation compared to channel catfish. Ontogenetic expression analyses indicated that the mRNA expressions of the Pf_TLR18, Pf_TLR19 and Pf_TLR21 genes could be detected from fertilized eggs to 30 day post-hatching and they exhibited different variation trends after hatching. The three TLR genes were expressed in various tissues, but they were mostly highly expressed in the spleen. The mRNA expression levels of the three genes were up-regulated in the spleen, head kidney, trunk kidney, liver and blood after challenge of killed Aeromonas hydrophila. In addition, the expressions of the three TLR genes were induced to up-regulate in isolated peripheral blood lymphocytes of yellow catfish after stimulation with lipopolysaccharides (LPS), peptidoglycan (PGN) and polyinosinic-polycytidylic acid (Poly I:C). Our findings indicate that the three TLR genes may play a potential role in the host defense against pathogenic microbes. These results will provide valuable information to better understand the function of TLR genes in the innate immune system of yellow catfish.

Chemical Tools for Studying TLR Signaling Dynamics

The detection of infectious pathogens is essential for the induction of antimicrobial immune responses. The innate immune system detects a wide array of microbes using a limited set of pattern-recognition receptors (PRRs). One family of PRRs with a central role in innate immunity are the Toll-like receptors (TLRs). Upon ligation, these receptors initiate signaling pathways culminating in the release of pro-inflammatory cytokines and/or type I interferons (IFN-I). In recent years, it has become evident that the specific subcellular location and timing of TLR activation affect signaling outcome. The subtlety of this signaling has led to a growing demand for chemical tools that provide the ability to conditionally control TLR activation. In this review, we survey current models for TLR signaling in time and space, discuss how chemical tools have contributed to our understanding of TLR ligands, and describe how they can aid further elucidation of the dynamic aspects of TLR signaling.

Selective evolution of Toll-like receptors 3, 7, 8, and 9 in bats

Previous studies have shown that bats are reservoirs of a large number of viruses, many of which cause illness and mortality in humans and other animals. However, these bat-associated pathogens cause little, if any, clinicopathology in bats. This long-term adaptation should be reflected somewhat in the immune system. Toll-like receptors (TLRs) are the first line of immune defense against pathogens in vertebrates. Therefore, this study focuses on the selection of TLRs involved in virus recognition. The coding sequences of TLR3, TLR7, TLR8, and TLR9 were sequenced in ten bats. The selection pressure acting on each gene was also detected using branch- and site-specific methods. The results showed that the ancestor of bats and certain other bat sublineages evolved under positive selection for TLR7, TLR8, and TLR9. The highest proportion of positive selection occurred in TLR9, followed by TLR8 and TLR7. All of the positively selected sites were located in the leucine-rich repeat (LRR) domain, which implied their important roles in pathogen recognition. However, TLR3 evolved under negative selection. Our results are not in line with previous studies which identified more positively selected sites in TLR8 in mammalian species. In this study, the most positively selected sites were found in TLR9. This study encompassed more species that were considered natural reservoirs of viruses. The positive selection for TLR7, TLR8, and TLR9 might contribute to the adaptation of pathogen-host interaction in bats, especially in bat TLR9.

Thyroid active agents T3 and PTU differentially affect immune gene transcripts in the head kidney of rainbow trout (Oncorynchus mykiss)

In mammals, numerous reports describe an immunomodulating effect of thyroid-active compounds. In contrast, only few reports have been published on this subject in fish. We previously demonstrated that immune cells of rainbow trout (Oncorhynchus mykiss) possess thyroid hormone receptors (THRs) and that exposure of trout to the thyroid hormone 3,3',5-triiodo-l-thyronine (T3) or the antithyroid drug propylthiouracil (PTU) alters immune cell transcript levels of THR and several immune genes. The present study aims to further characterize the immunomodulating action of thyroid-active compounds in trout immune cells. We report here the use of a custom-designed 60-mer oligo immune-targeted microarray for rainbow trout to analyze the gene expression profiles induced in the head kidney by T3 and PTU. Morphometric analyses of the thyroid showed that PTU exposure increased the size of the epithelial cells, whereas T3 induced no significant effects. Both T3 and PTU had diverse and partly contrasting effects on immune transcript profiles. The strongest differential effects of T3 and PTU on gene expressions were those targeting the Mitogen Associated Protein Kinase (MAPK), NFkB, Natural Killer (NK) and Toll-Like Receptor (TLR) pathways, a number of multipath genes (MPG) such as those encoding pleiotropic transcription factors (atf1, junb, myc), as well as important pro-inflammatory genes (tnfa, tnf6, il1b) and interferon-related genes (ifng, irf10). With these results we show for the first time in a fish species that the in vivo thyroidal status modulates a diversity of immune genes and pathways. This knowledge provides the basis to investigate both mechanisms and consequences of thyroid hormone- and thyroid disruptor-mediated immunomodulation for the immunocompetence of fish.

Role of TLR gene expression and cytokine profiling in the immunopathogenesis of viral hepatitis E

BACKGROUND

The clinical manifestations of Hepatitis E virus (HEV) range from self-limiting acute viral hepatitis (AVH) to acute liver failure (ALF). The varied clinical course is thought to be immune-mediated. Toll-like receptors (TLRs) play a central role in sensing and initiating innate antiviral-response and downstream signaling of TLRs modulates cytokine production, thereby playing an important role in determining the disease course.

OBJECTIVES

The present study was designed to elucidate the role of TLRs and cytokine production in the immunopathogenesis of HEV.

STUDY DESIGN

Peripheral blood mono-nuclear cells were separated from 50 AVH-HEV, 30 ALF-HEV patients and 50 healthy-controls. One-part of the PBMC was processed for RNA-extraction another pulsed with HEV-ORF2-peptide. Gene-expression levels of TLR (2-4, 7, and 8) were checked using semi-quantitative Real-time-PCR. Cytokine levels were analyzed using Cytokine-Bead-Array. TLR3-silencing experiments were performed and post-silencing cytokine levels were estimated.

RESULTS

TLR3 gene-expression in AVH was significantly higher than ALF (202.4±36.36 Vs 13.71±5.01; p<0.0001). Higher amount of both anti-and pro-inflammatory cytokines; IFNγ, TNF-α, IL10 and TGF-β were detected in the PBMC culture-supernatant of AVH Vs ALF (p<0.0001, p=0.0008, p=0.0002, p<0.0001 respectively). Post-silencing TLR3, significant decrease in IFNγ level was observed in the PBMC culture-supernatant (4.08±1.06 Vs 23.20±12.51; p=N0.0213).

CONCLUSIONS

TLR3 and IFNγ were found to play an important role in HEV disease pathogenesis. Patients capable of expressing high levels of TLR 3 and robust IFNγ response are able to limit the disease and recover uneventfully; while the patients with lower expression of TLR3 and IFNγ progress to ALF.

Up-regulation of the monocyte chemotactic protein-3 in sera from bone marrow transplanted children with torquetenovirus infection

BACKGROUND

Torquetenovirus (TTV) represents a commensal human virus producing life-long viremia in approximately 80% of healthy individuals of all ages. A potential pathogenic role for TTV has been suggested in immunocompromised patients with hepatitis of unknown etiology sustained by strong proinflammatory cytokines.

OBJECTIVES

The aim of this study was to investigate the sera immunological profile linked to TTV infection in bone marrow transplant (BMT) children with liver injury.

STUDY DESIGN

TTV infection was assessed in sera from 27 BMT patients with altered hepatic parameters and histological features, by the use of quantitative real-time PCR, along with TTV genogroups and coinfection with HEV. The qualitative and quantitative nature of soluble inflammatory factors was evaluated studying a large set of cytokines using the Bioplex platform. As controls, sera from 22 healthy children negative for serological and molecular hepatitis markers including TTV and HEV, and for autoimmune diseases, were selected.

RESULTS AND CONCLUSIONS

TTV was detected in 81.4% of BMT patients with a viral load ranging from 10(5) to 10(9) copies/mL. All samples were HEV-RNA negative. A pattern of cytokines, IFN-γ, TNF-α, FGF-basic (p<0.01) and MCP-3 (p<0.001) was found significantly highly expressed in TTV-positive patients compared to TTV-negative and controls. Of note, MCP-3 chemokine showed the highest sera concentration independently of the amount of TTV load and the status of immune system deregulation (p<0.001). In this pilot study for the first time, a positive association was found between TTV and increased level of MCP-3 suggesting a indirect role of TTV in liver injury.

Roles of PAR1 and PAR2 in viral myocarditis

Viral myocarditis is estimated to cause ~20% of sudden death in people under the age of 40. A variety of viruses have been found to cause myocarditis including coxsackievirus B3 (CVB3). Many studies have been performed with CVB3 because there is a mouse model of CVB3-induced myocarditis. Studies have shown that the TLR3-IFNβ pathway plays a central role in the innate immune response to CVB3 infection. Our laboratory studies the role of protease activated receptors (PAR) in different biological responses including viral infection. We examined the effect of a deficiency in either PAR1 or PAR2 on CVB3-induced myocarditis. Interestingly, we found that PAR1 knockout mice had increased cardiac injury whereas PAR2 knockout mice had decreased cardiac injury. Our studies support the notion that PARs modulate the innate immune response and can have both positive and negative effects on TLR-dependent responses.

Upregulation of Toll-like receptor 2 expression in colorectal cancer infected by human cytomegalovirus

The aim of the present study was to investigate the association between Toll-like receptor 2 (TLR2) expression and human cytomegalovirus (HCMV) in colorectal carcinoma by detecting the expression of IE1-72, TLR2, TLR4 and tumor necrosis factor (TNF)-α in colorectal carcinoma and colon adenoma samples, as well as by analyzing the mRNA levels of the proteins in colon cancer cell lines, following HCMV infection. For this study, 56 colorectal cancer and 36 colon adenoma samples were collected, and normal mucosal tissue adjacent to the tumor was used as the control. The expression of the IE1-72, TLR2, TLR4, nuclear factor (NF)-κB and TNF-α protein was detected by immunohistochemistry. Cells from the SW480 human colon carcinoma cell line were infected with HCMV. The expression of IE1-72, TLR2, TLR4, NF-κB and TNF-α mRNA was quantified at different time points prior to and following infection. The positive expression rate of IE1-72 was 44.6% (25/56) in colorectal cancer and 41.7% (15/36) in colon adenoma. These rates were significantly higher when compared with the 12.5% (7/56) observed in the normal tissues adjacent to the cancer tissues (P<0.05). The expression levels of TLR2, TLR4, NF-κB and TNF-α in colorectal cancer and adenoma were also higher than those in the control tissues. Furthermore, the expression of IE1-72 in colorectal cancer tissues was found to correlate with TLR2 and TLR4, and the correlation coefficients were 0.515 and 0.462, respectively. Following the infection of SW480 cells, the mRNA levels of TLR2 and TNF-α increased gradually from 6 h, peaked at 48 h, and then decreased gradually. No significant differences in TLR4 and NF-κB expression were identified. The results of the present study indicated that there is a specific association between HCMV and the occurrence and development of colorectal cancer, which may be facilitated by the TLR2 signaling pathway.

Astragalus Polysaccharide Protects Astrocytes from Being Infected by HSV-1 through TLR3/NF-κB Signaling Pathway

Astragalus polysaccharide (APS) is the most immunoreactive substance in Astragalus. APS can regulate the body's immunity and is widely used in many immune related diseases. However, till now, there is little information about its contribution to the protection of astrocytes infected by virus. Toll-like receptor 3 (TLR3) is a key component of the innate immune system and has the ability to detect virus infection and trigger host defence responses. This study was undertaken to elucidate the protective effect of APS on herpes simplex virus (HSV-1) infected astrocytes and the underlying mechanisms. The results showed that APS protected the astrocytes from HSV-1 induced proliferation inhibition along with increasing expression of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) markedly. Moreover, APS significantly promoted the expression of Toll-like receptor 3 (TLR3) and the activation of nuclear factor-κB (NF-κB) in astrocytes. In addition, while astrocytes were pretreated with TLR3 antibody before adding HSV-1 and APS, the expression of TLR3, TNF-α, and IL-6 and the activation of NF-κB decreased sharply. These results indicate that APS can protect astrocytes by promoting immunological function provoked by HSV-1 through TLR3/NF-κB pathway.

HSV-1 activates NF-kappaB in mouse astrocytes and increases TNF-alpha and IL-6 expression via Toll-like receptor 3

OBJECTIVE

To investigate the effect of HSV-1 infection via TLR3 on the transcriptional activity of NF-kappaB and the expression of cytokines TNF-alpha and IL-6 in astrocytes.

METHODS

HSV-1-infected primary astrocytes were cultured until the third passage and the mRNA and protein levels of TLR3, NF-kappaB, TNF-alpha, and IL-6 were assessed by immunofluorescence, RT-PCR, and Western blot. The effects of the NF-kappaB inhibitor pyrrolidine dithiocarbamate (PDTC) and TLR3-neutralizing antibody on the expression of NF-kappaB, TNF-alpha, and IL-6 were investigated.

RESULTS

Uninfected astrocytes expressed TLR3 and NF-kappaB at the mRNA and protein levels. After infection with HSV-1, the TLR3 mRNA and protein levels were up-regulated and NF-kappaB protein was highly expressed. Also, the mRNA and protein levels of TNF-alpha and IL-6 were up-regulated. Pyrrolidine dithiocarbamate inhibited NF-kappaB activation, resulting in the down-regulation of nuclear NF-kappaB protein, which led to the down-regulation of the mRNA and protein levels of TNF-alpha and IL-6. After blocking astrocyte membrane TLR3, the nuclear NF-kappaB protein expression was down-regulated and the mRNA and protein levels of TNF-alpha and IL-6 were increased. The antiviral functions of astrocytes were weaker, as reflected by higher HSV-1 glycoprotein D (gD) mRNA expression and increased HSV-1 titers.

CONCLUSION

Astrocytes infected with HSV-1 can activate NF-kappaB via TLR3 so as to up-regulate the expression of TNF-alpha and IL-6 that have antiviral functions.

Coagulation, protease-activated receptors, and viral myocarditis

The coagulation protease cascade plays an essential role in hemostasis. In addition, a clot contributes to host defense by limiting the spread of pathogens. Coagulation proteases induce intracellular signaling by cleavage of cell surface receptors called protease-activated receptors (PARs). These receptors allow cells to sense changes in the extracellular environment, such as infection. Viruses activate the coagulation cascade by inducing tissue factor expression and by disrupting the endothelium. Virus infection of the heart can cause myocarditis, cardiac remodeling, and heart failure. A recent study using a mouse model have shown that tissue factor, thrombin, and PAR-1 signaling all positively regulate the innate immune during viral myocarditis. In contrast, PAR-2 signaling was found to inhibit interferon-β expression and the innate immune response. These observations suggest that anticoagulants may impair the innate immune response to viral infection and that inhibition of PAR-2 may be a new strategy to reduce viral myocarditis.

Genetic polymorphisms in host innate immune sensor genes and the risk of nasopharyngeal carcinoma in North Africa

Nasopharyngeal carcinoma (NPC) is a rare malignancy in most parts of the world. It is an Epstein-Barr virus−associated malignancy with an unusual racial and geographical distribution. The host innate immune sensor genes play an important role in infection recognition and immune response against viruses. Therefore, we examined the association between polymorphisms in genes within a group of pattern recognition receptors (including families of Toll-like receptors, C-type lectin receptors, and retinoic acid−inducible gene I−like receptors) and NPC susceptibility. Twenty-six single-nucleotide polymorphisms (SNPs) in five pattern-recognition genes were genotyped in 492 North African NPC cases and 373 frequency-matched controls. TLR3_rs3775291 was the most significantly associated SNP (odds ratio [OR] 1.49; 95% confidence interval [95% CI] 1.11−2.00; P = 0.008; dominant model). The analysis showed also that CD209_rs7248637 (OR 0.69; 95% CI 0.52−0.93; P = 0.02; dominant model) and DDX58_rs56309110 (OR 0.70; 95% CI 0.51−0.98; P = 0.04) were associated with the risk of NPC. An 18% increased risk per allele was observed for the five most significantly associated SNPs, TLR3_rs3775291, CD209_rs7248637, DDX58_rs56309110, CD209_rs4804800, and MBL2_rs10824792, (p_trend = 8.2 × 10⁻⁴). Our results suggest that genetic variation in pattern-recognition genes is associated with the risk of NPC. These preliminary findings require replication in larger studies.

TLR3 activation evokes IL-6 secretion, autocrine regulation of Stat3 signaling and TLR2 expression in human bronchial epithelial cells

Human bronchial epithelial cells exposed to synthetic double-stranded RNA (poly I:C) exhibited increased IL-6 and RANTES secretion and TLR2 expression that was inhibited following TLR3 silencing. Increased NF-κB and Stat3 phosphorylation were detected after poly I:C exposure and pretreatment with neutralizing antibody targeting IL-6 receptor α (IL-6Rα -nAb) or blocking Jak2 and Stat3 activity inhibited Stat3 phosphorylation. TLR2 up-regulation by poly I:C was also reduced by IL-6Rα-nAb and inhibitors of Jak2, Stat3 and NF-κB phosphorylation, whereas RANTES secretion was unaffected, but abolished following NF-κB inhibition. Treatment with exogenous IL-6 failed to increase TLR2. These findings demonstrate that TLR3 activation differentially regulates TLR expression through autocrine signaling involving IL-6 secretion, IL-6Rα activation and subsequent phosphorylation of Stat3. The results also indicate that NF-κB and Stat3 are required for TLR3-dependent up-regulation of TLR2 and that its delayed expression was due to a requirement for IL-6-dependent Stat3 activation.

Expressions of Toll-like receptors 3, 4, 7, and 9 in cervical lesions and their correlation with HPV16 infection in Uighur women

Recent findings show that Toll-like receptors (TLRs) expressed in immune cells play a crucial role in the innate immune response and the subsequent induction of adaptive immune responses against microbial infection on tissue injury. Furthermore, expression of TLRs in cancer cells is associated with tumor proliferation and invasion. To explore the role of TLRs expression in cervical Carcinogenesis in Uighur women, we detected the expressions of TLR3, TLR4, TLR7, and TLR9 in 25 normal cervical tissues, 64 cervical intraepithelial neoplasia (CIN) tissues, and 63 cervical squamous cell carcinoma (CSCC) tissues using immunohistochemical staining, as well as human papillomavirus type 16 (HPV16) infection using PCR. All samples used in this study were from Xinjiang Uighur women. We found the expression levels of TLR4, TLR7, and TLR9 were significantly higher in CIN and CSCC than in normal controls (P < 0.05). Up-regulation of TLR4 and TLR7 were correlated with tumor differentiation but not FIGO stage or lymph node metastasis (P > 0.05). Up-regulation of TLR9 was correlated with lymph node metastasis (P < 0.05) but not tumor differentiation or FIGO stage (P > 0.05). We also analyzed the correlation between the expressions of TLRs and HPV16 infection and found that the expressions of TLR4 and TLR9 significantly correlated with HPV16 infection in CIN (r = 7.434, P = 0.006; r = 7.123, P = 0.008) and CSCC (r = 6.423, P = 0.001; r = 8.478, P = 0.004), whereas the expression of TLR3 was not significantly different in any of the three groups and had no significant correlation with HPV16 infection. Our results suggest that high expression of TLR4, TLR7, and TLR9 may play important roles in the development and progression of CIN and CSCC in Uighur women, and the expressions of TLR4 and TLR9 can be up-regulated by HPV16 infection.

Chandipura virus infection in mice: the role of toll like receptor 4 in pathogenesis

Background

The susceptibility of mice and humans to Chandipura virus infection is age-dependent. Upon experimental infection, mice secrete significant amounts of proinflammatory cytokines. Similarly, children who recover from natural infection with the virus show significant amounts of TNF-α production, suggesting that innate immunity plays a major role in the response to Chandipura virus. Toll-like receptors (TLR) are key host molecules involved in innate immune responses in infections. Therefore, the aim of this study was to examine the role of TLR in the response to Chandipura virus infection.

Methods

The mouse monocyte-macrophage cell line, RAW 264.7, and C3H/HeJ mice were used as models. Micro array techniques were used to identify the type of TLR involved in the response to infection. The results were validated by examining TLR expression using flow cytometry and by measuring the levels of proinflammatory cytokines and nitric oxide (NO) in the culture supernatants using bead assays and the Griess method, respectively. The pathogenic role of Toll-like receptor 4 (TLR4) was studied in a TLR4 mutant strain of mice -C3H/HeJ and the results compared with those from wild-type mice- C3H/CaJ. The pathogenic effects of NO were studied by treating experimentally infected mice with the NO inhibitor, aminoguanidine (AG).

Results

The micro array results showed that TLR4 was regulated after Chandipura virus infection. At high multiplicities of infection (10 MOI), RAW cells up- regulated cell surface expression of TLR4 and secreted significant amounts of TNF-α, MCP-1, IL-10 and IL-12 and NO. The survival rate of C3H/HeJ mice was higher than those of wild-type C3H/CaJ mice. The survived C3H/HeJ mice secreted significant quantity of MCP-1 and IFN-γ cytokines and cleared virus from brain. Similarly, the survival rate of AG-treated mice was higher than those of the untreated controls.

Conclusions

Chandipura virus regulates TLR4, which leads to the secretion of proinflammatory cytokines and NO by infected RAW cells. Difference in survival rate in TLR4 mutant mice and nitric oxide inhibitor treated mice, confirmed the role of these molecules in disease pathogenesis. The result is significant in clinical management and designing antiviral intervention for Chandipura virus infection.

The Role of TLR2 in Infection and Immunity

Toll-like receptors (TLRs) are recognition molecules for multiple pathogens, including bacteria, viruses, fungi, and parasites. TLR2 forms heterodimers with TLR1 and TLR6, which is the initial step in a cascade of events leading to significant innate immune responses, development of adaptive immunity to pathogens and protection from immune sequelae related to infection with these pathogens. This review will discuss the current status of TLR2 mediated immune responses by recognition of pathogen-associated molecular patterns (PAMPS) on these organisms. We will emphasize both canonical and non-canonical responses to TLR2 ligands with emphasis on whether the inflammation induced by these responses contributes to the disease state or to protection from diseases.

dsRNA sensors and plasmacytoid dendritic cells in host defense and autoimmunity

The innate immune system detects viruses through molecular sensors that trigger the production of type I interferons (IFN-I) and inflammatory cytokines. As viruses vary tremendously in size, structure, genomic composition, and tissue tropism, multiple sensors are required to detect their presence in various cell types and tissues. In this review, we summarize current knowledge of the diversity, specificity, and signaling pathways downstream of viral sensors and ask whether two distinct sensors that recognize the same viral component are complementary, compensatory, or simply redundant. We also discuss why viral sensors are differentially distributed in distinct cell types and whether a particular cell type dominates the IFN-I response during viral infection. Finally, we review evidence suggesting that inappropriate signaling through viral sensors may induce autoimmunity. The picture emerging from these studies is that disparate viral sensors in different cell types form a dynamic and integrated molecular network that can be exploited for improving vaccination and therapeutic strategies for infectious and autoimmune diseases.

Antimicrobial decapeptide KSL-W attenuates Candida albicans virulence by modulating its effects on Toll-like receptor, human β-defensin, and cytokine expression by engineered human oral mucosa

We investigated the toxicity of synthetic antimicrobial decapeptide KSL-W on normal human gingival epithelial cell cultures, its effect on Candida albicans adhesion and growth, and the activation of epithelial cell innate immunity. Our results indicate that KSL-W had no toxic effect on cell adhesion or growth, suggesting its safe use with human cells. Pre-treating C. albicans with KSL-W attenuated the yeast's virulence as demonstrated by its reduced adhesion and growth on engineered human oral mucosa epithelium and the subsequent decreased expression of some innate defense molecules by targeted epithelial cells. Indeed, the expression of Toll-like receptors and human β-defensins was reduced in tissues infected with KSL-W-treated Candida. Proinflammatory cytokine secretion (IL-1β and IL-6) by the epithelial cells was also regulated by KSL-W in a manner similar to that of antifungal molecule amphotericin B. These findings therefore show that KSL-W is safe for use with human cells and is able to attenuate Candida virulence by modulating its effects on host innate immunity. This study proposes the potential application of KSL-W peptide as an alternative antifungal agent.