Airway-delivered short-chain fatty acid acetate boosts antiviral immunity during rhinovirus infection

BACKGROUND

Microbiota are recognized to play a major role in regulation of immunity through release of immunomodulatory metabolites such as short-chain fatty acids (SCFAs). Rhinoviruses (RVs) induce upper respiratory tract illnesses and precipitate exacerbations of asthma and chronic obstructive pulmonary disease through poorly understood mechanisms. Local interactions between SCFAs and antiviral immune responses in the respiratory tract have not been previously investigated.

OBJECTIVE

We sought to investigate whether pulmonary metabolite manipulation through lung-delivered administration of SCFAs can modulate antiviral immunity to RV infection.

METHODS

We studied the effects of intranasal administration of the SCFAs acetate, butyrate, and propionate on basal expression of antiviral signatures, and of acetate in a mouse model of RV infection and in RV-infected lung epithelial cell lines. We additionally assessed the effects of acetate, butyrate, and propionate on RV infection in differentiated human primary bronchial epithelial cells.

RESULTS

Intranasal acetate administration induced basal upregulation of IFN-β, an effect not observed with other SCFAs. Butyrate induced RIG-I expression. Intranasal acetate treatment of mice increased interferon-stimulated gene and IFN-λ expression during RV infection and reduced lung virus loads at 8 hours postinfection. Acetate ameliorated virus-induced proinflammatory responses with attenuated pulmonary mucin and IL-6 expression observed at day 4 and 6 postinfection. This interferon-enhancing effect of acetate was confirmed in human bronchial and alveolar epithelial cell lines. In differentiated primary bronchial epithelial cells, butyrate treatment better modulated IFN-β and IFN-λ gene expression during RV infection.

CONCLUSIONS

SCFAs augment antiviral immunity and reduce virus load and proinflammatory responses during RV infection.

New triazole-substituted triterpene derivatives exhibiting anti-RSV activity: synthesis, biological evaluation, and molecular modeling

Respiratory syncytial virus (RSV) is a major cause of acute lower respiratory tract infections in infants. Currently, ribavirin, a nucleoside analog containing a 1,2,4-triazole-3-carboxamide moiety, is a first-line drug for its treatment, however, its clinical use has been limited due to its side effects. Here, we designed two new nitroaryl-1,2,3-triazole triterpene derivatives as novel anti-RSV drugs. Their anti-RSV and cytotoxic activity were evaluated in vitro, RSV protein F gene effects by RT-PCR and molecular modeling with inosine monophosphate dehydrogenase (IMPDH) were performed. Compound 8 was the best performing compound, with an EC50 value of 0.053 μM, a TI of 11160.37 and it inhibited hRSV protein F gene expression by approximately 65%. Molecular docking showed a top-ranked solution located in the same region occupied by crystallographic ligands in their complex with IMPDH. The results obtained in this study suggest that compound 8 might be a new anti-RSV candidate.

Impact of Microbiota Depletion by Antibiotics on SARS-CoV-2 Infection of K18-hACE2 Mice

Clinical and experimental data indicate that severe acute respiratory syndrome coronavirus (SARS-CoV)-2 infection is associated with significant changes in the composition and function of intestinal microbiota. However, the relevance of these effects for SARS-CoV-2 pathophysiology is unknown. In this study, we analyzed the impact of microbiota depletion after antibiotic treatment on the clinical and immunological responses of K18-hACE2 mice to SARS-CoV-2 infection. Mice were treated with a combination of antibiotics (kanamycin, gentamicin, metronidazole, vancomycin, and colistin, Abx) for 3 days, and 24 h later, they were infected with SARS-CoV-2 B lineage. Here, we show that more than 80% of mice succumbed to infection by day 11 post-infection. Treatment with Abx had no impact on mortality. However, Abx-treated mice presented better clinical symptoms, with similar weight loss between infected-treated and non-treated groups. We observed no differences in lung and colon histopathological scores or lung, colon, heart, brain and kidney viral load between groups on day 5 of infection. Despite some minor differences in the expression of antiviral and inflammatory markers in the lungs and colon, no robust change was observed in Abx-treated mice. Together, these findings indicate that microbiota depletion has no impact on SARS-CoV-2 infection in mice.

Microbiota and the Response to Vaccines Against Respiratory Virus

This mini review describes the role of gut and lung microbiota during respiratory viral infection and discusses the implication of the microbiota composition on the immune responses generated by the vaccines designed to protect against these pathogens. This is a growing field and recent evidence supports that the composition and function of the microbiota can modulate the immune response of vaccination against respiratory viruses such as influenza and SARS-CoV-2. Recent studies have highlighted that molecules derived from the microbiome can have systemic effects, acting in distant organs. These molecules are recognized by the immune cells from the host and can trigger or modulate different responses, interfering with vaccination protection. Modulating the microbiota composition has been suggested as an approach to achieving more efficient protective immune responses. Studies in humans have reported associations between a better vaccine response and specific bacterial taxa. These associations vary among different vaccine strategies and are likely to be context-dependent. The use of prebiotics and probiotics in conjunction with vaccination demonstrated that bacterial components could act as adjuvants. Future microbiota-based interventions may potentially improve and optimize the responses of respiratory virus vaccines.

Large-Scale Structure-Based Screening of Potential T Cell Cross-Reactivities Involving Peptide-Targets From BCG Vaccine and SARS-CoV-2

Although not being the first viral pandemic to affect humankind, we are now for the first time faced with a pandemic caused by a coronavirus. The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has been responsible for the COVID-19 pandemic, which caused more than 4.5 million deaths worldwide. Despite unprecedented efforts, with vaccines being developed in a record time, SARS-CoV-2 continues to spread worldwide with new variants arising in different countries. Such persistent spread is in part enabled by public resistance to vaccination in some countries, and limited access to vaccines in other countries. The limited vaccination coverage, the continued risk for resistant variants, and the existence of natural reservoirs for coronaviruses, highlight the importance of developing additional therapeutic strategies against SARS-CoV-2 and other coronaviruses. At the beginning of the pandemic it was suggested that countries with Bacillus Calmette-Guérin (BCG) vaccination programs could be associated with a reduced number and/or severity of COVID-19 cases. Preliminary studies have provided evidence for this relationship and further investigation is being conducted in ongoing clinical trials. The protection against SARS-CoV-2 induced by BCG vaccination may be mediated by cross-reactive T cell lymphocytes, which recognize peptides displayed by class I Human Leukocyte Antigens (HLA-I) on the surface of infected cells. In order to identify potential targets of T cell cross-reactivity, we implemented an in silico strategy combining sequence-based and structure-based methods to screen over 13,5 million possible cross-reactive peptide pairs from BCG and SARS-CoV-2. Our study produced (i) a list of immunogenic BCG-derived peptides that may prime T cell cross-reactivity against SARS-CoV-2, (ii) a large dataset of modeled peptide-HLA structures for the screened targets, and (iii) new computational methods for structure-based screenings that can be used by others in future studies. Our study expands the list of BCG peptides potentially involved in T cell cross-reactivity with SARS-CoV-2-derived peptides, and identifies multiple high-density "neighborhoods" of cross-reactive peptides which could be driving heterologous immunity induced by BCG vaccination, therefore providing insights for future vaccine development efforts.

Isolation and Cell Culture of Human Nasopharyngeal Cells: A Model for Testing Immune Response and Antiviral Treatment

The use of in vitro methods of infecting cell lines to test new treatments for SARS-CoV-2 does not always recapitulate the real context of the infection, and mouse models for SARS-CoV-2 infection are limited. Here we describe a novel ex vivo approach by collecting, isolating, and culturing nasal epithelial cells obtained from patients with COVID-19. This technique allows us to study immune responses and test new treatments directly on cells from patients naturally infected with SARS-CoV-2.

RvD1 treatment during primary infection modulates memory response increasing viral load during respiratory viral reinfection

Resolvin D1 (RvD1), which is biosynthesized from essential long-chain fatty acids, is involved in anti-inflammatory activity and modulation of T cell response. Memory CD8+ T cells are important for controlling tumor growth and viral infections. Exacerbated inflammation has been described as impairing memory CD8+ T cell differentiation. This study aimed to verify the effects of RvD1 on memory CD8+ T cells in vitro and in vivo in a respiratory virus infection model. Peripheral blood mononuclear cells were treated at different time points with RvD1 and stimulated with anti-CD3/anti-CD28 antibodies. Pre-treatment with RvD1 increases the expansion of memory CD8+ T cells. The IL-12 level, a cytokine described to control memory CD8+ T cells, was reduced with RvD1 pre-treatment. When the mTOR axis was inhibited, the IL-12 levels were restored. In a respiratory virus infection model, Balb/c mice were treated with RvD1 before infection or after 7 days after infection. RvD1 treatment after infection increased the frequency of memory CD8+ T cells in the lung expressing II4, II10, and Ifng. During reinfection, RvD1-treated and RSV-infected mice present a high viral load in the lung and lower antibody response in the serum. Our results show that RvD1 modulates the expansion and phenotype of memory CD8+ T cells but contributed to a non-protective response after RSV reinfection.

Association between interleukin-10 polymorphisms and CD4+CD25+FOXP3+ T cells in asthmatic children

OBJECTIVE

The aim of this study was to evaluate the association between possible functional interleukin-10 (IL-10) polymorphisms, IL-10 expression and regulatory T cells (Tregs) frequency, and/or asthma severity in a sample of children and adolescents.

METHODS

This is a nested case-control genetic association study. The study sample consisted of children and adolescents aged 8-14 from public schools. Four polymorphisms of the IL-10 gene (rs1518111, rs3024490, rs3024496, rs3024491) were genotyped in asthmatic subjects and controls using real-time PCR. Tregs cells and IL-10 were analyzed in peripheral blood mononuclear cells by flow cytometry. The severity of asthma was defined according to the Global Initiative for Asthma (GINA) guideline.

RESULTS

One hundred twenty-three asthmatic subjects and fifty-eight controls participated in the study. The single nucleotide polymorphism (SNP) rs3024491 (T allele) showed association with asthma severity, presenting a higher frequency in patients in the moderate asthma group. The T allele of variant rs3024491 also showed an association with reduced IL-10 levels (p=0.01) and with increased Tregs frequency (p=0.01). The other variants did not present consistent associations.

CONCLUSIONS

Our results suggest that moderate asthma is associated with a higher frequency of the T allele in the SNP rs3024491. In addition, the variant rs3024491 (TT) was associated with a reduction in IL-10 production and an increased percentage of Tregs cells, suggesting possible mechanisms that influence asthma severity.

TNF-mediated alveolar macrophage necroptosis drives disease pathogenesis during respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is the major cause of acute bronchiolitis in infants under 2 years old. Necroptosis has been implicated in the outcomes of respiratory virus infections. We report that RSV infection triggers necroptosis in primary mouse macrophages and human monocytes in a RIPK1-, RIPK3- and MLKL-dependent manner. Moreover, necroptosis pathways are harmful to RSV clearance from alveolar macrophages. Additionally, Ripk3^-/- mice were protected from RSV-induced weight loss and presented with reduced viral loads in the lungs.Alveolar macrophage depletion also protected mice from weight loss and decreased lung RSV virus load. Importantly, alveolar macrophage depletion abolished the upregulation of Ripk3 and Mlkl gene expression induced by RSV infection in the lung tissue.Autocrine tumor necrosis factor (TNF)-mediated RSV-triggered macrophage necroptosis and necroptosis pathways were also involved in TNF secretion even when macrophages were committed to cell death, which can worsen lung injury during RSV infection. In line, Tnfr1^-/- mice had a marked decrease in Ripk3 and Mlkl gene expression and a sharp reduction in the numbers of necrotic alveolar macrophages in the lungs. Finally, we provide evidence that elevated nasal levels of TNF are associated with disease severity in infants with RSV bronchiolitis.We propose that targeting TNF and/or the necroptotic machinery may be valuable therapeutic approaches to reduce the respiratory morbidity caused by RSV infection in young children.

Circulating Type I Interferon Levels and COVID-19 Severity: A Systematic Review and Meta-Analysis

Introduction

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections, resulting in a range of clinical manifestations and outcomes. Laboratory and immunological alterations have been considered as potential markers of disease severity and clinical evolution. Type I interferons (IFN-I), mainly represented by IFN-α and β, are a group of cytokines with an important function in antiviral responses and have played a complex role in COVID-19. Some studies have demonstrated that IFN-I levels and interferon response is elevated in mild cases, while other studies have noted this in severe cases. The involvement of IFN-I on the pathogenesis and outcomes of SARS-CoV-2 infection remains unclear. In this study, we summarize the available evidence of the association of plasma protein levels of type I IFN with the severity of COVID-19.

Methods

The PRISMA checklist guided the reporting of the data. A systematic search of the MEDLINE (PubMed), EMBASE, and Web of Science databases was performed up to March of 2021, looking for articles that evaluated plasma protein levels of IFN-I in mild, severe, or critical COVID-19 patients. Comparative meta-analyses with random effects were performed to compare the standardized mean differences in plasma protein levels of IFN-I of mild versus severe and mild versus critical patients. Meta-regressions were performed to test the moderating role of age, sex, time that the IFN-I was measured, and limit of detection of the assay used in the difference between the means.

Results

There was no significant difference in plasma levels of IFN-α when comparing between mild and severe patients (SMD = -0.236, 95% CI -0.645 to 0.173, p = 0.258, I2 = 82.11), nor when comparing between patients mild and critical (SMD = 0.203, 95% CI -0.363 to 0.770, p = 0.481, I2 = 64.06). However, there was a significant difference between healthy individuals and patients with mild disease (SMD = 0.447, 95% CI 0.085 to 0.810, p = 0.016, I2 = 62.89).

Conclusions

Peripheral IFN-α cannot be used as a severity marker as it does not determine the clinical status presented by COVID-19 patients.

Lymphoid markers predict prognosis of pediatric and adolescent acute myeloid leukemia

Acute Myeloid Leukemia (AML) is a complex and highly aggressive disease. To characterize the prognostic factors of pediatric patients with AML relapse, a retrospective cohort study was performed to collect data from children and adolescents, at a hematological oncology reference center, over 11 years. We selected 51 cases of the disease, diagnosed and treated uniformly, divided into two groups: with complete remission (n = 33; 65 %) and with relapse (n = 18; 35 %). The groups were homogeneous concerning demographic characteristics and hematological parameters at diagnosis. AML M3 was the most common subtype (n = 19; 37 %) and was associated with a good prognosis. The highest rate of relapse was with AML M0 (n = 3 of 5 patients; 60 %). The most predominant gene mutation, FLT3-ITD, did not influence the prognosis in our study. The complete remission group presented a higher mean frequency of positive cells for the granulocytic marker CD13a at diagnosis. In cases with AML relapse, CD36, CD4, CD7, and CD22 were the most expressed markers. Increase incidence of recurrence was associated with CD7 (HR 1.035; p = 0.003), CD4 (HR 1.032, p = 0.001) and CD22 (HR 1.042; p = 0.049). Our results highlight the importance of analyzing immunophenotypic markers to help predict the outcome of AML in children and adolescents.

IL-21 treatment recovers follicular helper T cells and neutralizing antibody production in respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is the major cause of lower respiratory tract infections in children under 1 year. RSV vaccines are currently unavailable, and children suffering from multiple reinfections by the same viral strain fail to develop protective responses. Although RSV-specific antibodies can be detected upon infection, these have limited neutralizing capacity. Follicular helper T (Tfh) cells are specialized in providing signals to B cells and help the production and affinity maturation of antibodies, mainly via interleukin (IL) 21 secretion. In this study, we evaluated whether RSV could inhibit Tfh responses. We observed that Tfh cells fail to upregulate IL-21 production upon RSV infection. In the lungs, RSV infection downregulated the expression of IL-21/interleukin-21 receptor (IL-21R) in Tfh cells and upregulated programmed death-ligand 1 (PD-L1) expression in dendritic cells (DCs) and B cells. PD-L1 blockade during infection recovered IL-21R expression in Tfh cells and increased the secretion of IL-21 in a DC-dependent manner. IL-21 treatment decreased RSV viral load and lung inflammation, inducing the formation of tertiary lymphoid organs in the lung. It also decreased regulatory follicular T cells, and increased Tfh cells, B cells, antibody avidity and neutralization capacity, leading to an overall improved anti-RSV humoral response in infected mice. Passive immunization with purified immunoglobulin G from IL-21-treated RSV-infected mice protected against RSV infection. Our results unveil a pathway by which RSV affects Tfh cells by increasing PD-L1 expression on antigen-presenting cells, highlighting the importance of an IL-21-PD-L1 axis for the generation of protective responses to RSV infection.

Respiratory syncytial virus reduces STAT3 phosphorylation in human memory CD8 T cells stimulated with IL-21

Respiratory syncytial virus (RSV) is a common cause of childhood lower respiratory tract infections. The recent failure of a vaccine candidate based on recombinant F protein underlines the urgent need to better understand the protective human memory immune response against RSV. Signal transducer and activator of transcription 3 (STAT3) protein is a transcription factor that promotes the maturation of the memory CD8 T cell response in cooperation with IL-10 and IL-21. However, the role of STAT3 in the memory CD8 T cell response during RSV infection remains to be elucidated. We found that in infants with bronchiolitis infected with RSV, the expression of STAT3 detected in nasal washes is reduced when compared to that in infants infected by other viruses. In vitro, RSV impairs STAT3 phosphorylation induced by IL-21 in purified human memory CD8 T cells. In addition, RSV decreases granzyme B production by memory CD8 T cells, reducing its cytotoxic activity against RSV-infected epithelial pulmonary cell lines. Together, these data indicate that RSV modulates the IL-21/STAT3 pathway in human memory CD8 T cells, and this could be a mechanism to be further explored to improve the memory response against the infection.

Microbiota-derived acetate protects against respiratory syncytial virus infection through a GPR43-type 1 interferon response

Severe respiratory syncytial virus (RSV) infection is a major cause of morbidity and mortality in infants <2 years-old. Here we describe that high-fiber diet protects mice from RSV infection. This effect was dependent on intestinal microbiota and production of acetate. Oral administration of acetate mediated interferon-β (IFN-β) response by increasing expression of interferon-stimulated genes in the lung. These effects were associated with reduction of viral load and pulmonary inflammation in RSV-infected mice. Type 1 IFN signaling via the IFN-1 receptor (IFNAR) was essential for acetate antiviral activity in pulmonary epithelial cell lines and for the acetate protective effect in RSV-infected mice. Activation of Gpr43 in pulmonary epithelial cells reduced virus-induced cytotoxicity and promoted antiviral effects through IFN-β response. The effect of acetate on RSV infection was abolished in Gpr43^−/− mice. Our findings reveal antiviral effects of acetate involving IFN-β in lung epithelial cells and engagement of GPR43 and IFNAR.

Dietary fibers and SCFAs can exert a protective effect against respiratory syncytial virus (RSV). Here, the authors report that microbiota-derived acetate protects mice against RSV infection via GPR43- mediated type 1 interferon response induction in the lungs.

Evaluation of nasal levels of interferon and clinical severity of influenza in children

BACKGROUND

Experimental data show that type I interferon has a key role in innate immune response against influenza infection.

OBJECTIVE

We compared nasal levels of interferon-α2 and β among inpatients and outpatients with influenza.

STUDY DESIGN

Children younger than 5 years of age with influenza-like illness seeking care at the emergency department within the first 72 h of disease onset were prospectively included. Clinical and demographic data and secretions through nasal wash were obtained. Influenza infection was assessed through reverse-transcription polymerase chain reaction and nasal levels of interferon-α2 and β were measured by enzyme-linked immunosorbent assay. All patients followed until the end of the disease.

RESULTS

One hundred patients were included, of which 24 had confirmed influenza infection, and 5 of them were hospitalized. Subtypes A (H3N2) and B were confirmed in 10 and 14 patients, respectively. Seventy-six patients without influenza, including 48% of outpatients, were recruited as controls. All hospitalized patients were significantly younger regardless of influenza status (age <6 months in 59% vs. 23.2%, p < 0.001). All other data were similar among the groups. Comparing median levels of interferon-α2 among children with influenza, levels were significantly higher in outpatients than in hospitalized patients and were 263.2 pg/mL (25-75 interquartile range: 58.3-634) and detectable in only one patient (90 pg/mL), respectively. The levels of interferon-α2 in controls and those of interferon-β in all groups were not detected.

CONCLUSIONS

Higher levels of interferon-α2 in patients with less severe influenza reinforce experimental evidence about the protective role of interferon-α2 against influenza infection.

Synthesis of three triterpene series and their activity against respiratory syncytial virus

The human respiratory syncytial virus (hRSV) is a leading cause of hospitalization due to acute lower respiratory infection especially in infants and young children, sometimes causing fatal cases. The monoclonal antibody palivizumab is one of the available options for preventing this virus, and at the moment there are several hRSV vaccine trials underway. Unfortunately, the only drug option to treat hRSV infection is ribavirin, which can be used in severe high-risk cases. For this reason, new medicines are needed and, in this context, the triterpenes and their derivatives are promising alternatives, since many of them have shown important antiviral activity, such as bevirimat. Therefore, we report three series of triterpene (betulin (BE), betulinic acid (BA), and ursolic acid (UA)) derivatives tested against hRSV. The derivatives were synthesized by using commercial anhydrides in an easy and inexpensive step reaction. For the antiviral assay, A549 cells were infected by hRSV and after 96 h of compound or ribavirin (positive control) treatment, the cell viability was tested by MTT assay. DMSO, non-infected cells and infected cells without treatment were used as negative control. The triterpene esterification at the hydroxyl group resulted in 17 derivatives. The 3,28-di-O-acetylbetulin derivative (1a) showed the best results for cell viability, and real-time PCR amplification was performed for 1a treatment. Remarkably, one new anti-hRSV prototype was obtained through an easy synthesis of BE, which shall represent an alternative for a new lead compound for anti-hRSV therapy.

Lack of association between viral load and severity of acute bronchiolitis in infants

Objective:

To investigate the correlation between respiratory syncytial viral load and length of hospitalization in infants with acute wheezing episodes.

Methods:

This was a two-year, cross-sectional study of infants ≤ 12 months of age with bronchiolitis at the time of admission to a tertiary hospital. For the identification of respiratory viruses, nasopharyngeal secretions were collected. Samples were analyzed (throughout the study period) by direct immunofluorescence and (in the second year of the study) by quantitative real-time PCR. We screened for three human viruses: rhinovirus, respiratory syncytial virus, and metapneumovirus.

Results:

Of 110 samples evaluated by direct immunofluorescence, 56 (50.9%) were positive for a single virus, and 16 (14.5%) were positive for two or more viruses. Among those 72 samples, the most prevalent virus was respiratory syncytial virus, followed by influenza. Of 56 samples evaluated by quantitative real-time PCR, 24 (42.8%) were positive for a single virus, and 1 (1.7%) was positive for two viruses. Among those 25 samples, the most prevalent virus was again respiratory syncytial virus, followed by human rhinovirus. Coinfection did not influence the length of the hospital stay or other outcome s. In addition, there was no association between respiratory syncytial virus load and the length of hospitalization.

Conclusions:

Neither coinfection nor respiratory syncytial viral load appears to influence the outcomes of acute bronchiolitis in infants.

Rapamycin increases RSV RNA levels and survival of RSV-infected dendritic cell depending on T cell contact

The macrolide rapamycin inhibits mTOR (mechanist target of rapamycin) function and has been broadly used to unveil the role of mTOR in immune responses. Inhibition of mTOR on dendritic cells (DC) can influence cellular immune response and the survival of DC. RSV is the most common cause of hospitalization in infants and is a high priority candidate to vaccine development. In this study we showed that rapamycin treatment on RSV-infected murine bone marrow-derived DC (BMDC) decreases the frequency of CD8(+)CD44(high) T cells. However, inhibition of mTOR on RSV-infected BMDC did not modify the activation phenotype of these cells. RSV-RNA levels increase when infected BMDC were treated with rapamycin. Moreover, we observed that rapamycin diminishes apoptosis cell death of RSV-infected BMDC co-culture with T cells and this effect was abolished when the cells were co-cultured in a transwell system that prevents cell-to-cell contact or migration. Taken together, these data indicate that rapamycin treatment present a toxic effect on RSV-infected BMDC increasing RSV-RNA levels, affecting partially CD8 T cell differentiation and also increasing BMDC survival in a mechanism dependent on T cell contact.

Respiratory viral coinfection and disease severity in children: A systematic review and meta-analysis

•

Respiratory viral coinfections are common in children.

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Overall pediatric respiratory viral coinfections have no impact on severity.

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Prognostic role of specific viral interactions remains unclear.

Background

With advent of molecular diagnostic technologies, studies have reported detection of two or more respiratory viruses in about 30% of children with respiratory infections. However, prognostic role of coinfection remains unclear.

Objective

Evaluate relation between respiratory viral confection and illness severity in children.

Study design

MEDLINE (through PUBMED), EMBASE, EBSCO, LILACS databases were searched up to March 2015 by two independent reviewers. Studies assessing severity of viral coinfection in patients aged less than 18 years were included. Standardized forms were used for data extraction of population, study design, clinical syndromes, virus combinations compared and severity outcomes. Risk of bias and quality of evidence were assessed through EPHPP and GRADE. Subgroup analysis was performed according to age and viral combinations.

Results

Of 5218 records screened, 43 were included in analysis. Viral coinfection did not influence risks of all outcomes assessed: length of stay (mean difference in days in coinfection, −0.10 [95% confidence interval: −0.51 to 0.31]), length of supplemental oxygen (−0.42 [−1.05 to 0.20]), need of hospitalization (odds ratio of coinfection, 0.96 [95% confidence interval: 0.61–1.51]), supplemental oxygen (0.94 [0.66 to 1.34]), need of intensive care (0.99 [0.64 to 1.54]), mechanical ventilation (0.81 [0.33 to 2.01]) and death (2.22 [0.83 to 5.95]). Sub-analyses according to age and viral combinations have not shown influence of these factors in outcomes.

Conclusions

Respiratory viral coinfection did not increase severity in all outcomes assessed. Further studies are necessary to confirm this finding, especially regarding role of specific viral interactions.

Immunomodulator plasmid projected by systems biology as a candidate for the development of adjunctive therapy for respiratory syncytial virus infection

An imbalance in Th1/Th2 cytokine immune response has been described to influence the pathogenesis of respiratory syncytial virus (RSV) acute bronchiolitis and the severity of infection. Th2-driven response has been well described under first RSV vaccine (formalin-inactivated RSV vaccine antigens) and replicated in some conditions for RSV-infected mice, in which a Th2-dependent lung eosinophilia increases illness severity, accompanied of tissue damage. Currently, several prototypes of RSV vaccine are being tested, but there is no vaccine available so far. The advance of bioinformatics can help to solve this issue. Systems biology approaches based on network topological analysis may help to identify new genes in order to direct Th1 immune response during RSV challenge. For this purpose, network centrality analyses from high-throughput experiments were performed in order to select major genes enrolled in each T-helper immune response. Thus, genes termed Hub (B) and bottlenecks (H), which control the flow of biological information (Th1 or Th2 immune response, in this case) within the network, would be identified. As these genes possess high potential to promote Th1 immune response, they could be cloned under regulation of specific promoters in a plasmid, which will be available as a gene-transfer adjunctive to vaccines. Th1 immune response potentiated by our strategy may contribute to accelerate Th1/Th2 shift from neonatal immune system, which might favor protective immunity against RSV infection and reduce lung damage.

Intratumoral TLR-4 Agonist Injection Is Critical for Modulation of Tumor Microenvironment and Tumor Rejection

The tumor microenvironment shelters a complex network of mechanisms that enables local Immunosuppression to support tumor growth. In this study we found that, B16F10 melanoma growth is inversely correlated with peritumoral infiltrate cell number and with cell numbers in draining lymph nodes. Tumor growth ensued even when a foreign antigen was expressed by B16F10 cells in the presence of naïve specific CD8+ T cells. Treatment with TLR agonists has shown to sometimes result in tumor regression, however, not always with long-lasting effects. We compared the relevance of different injection regimens of lipopolysaccharide (LPS). Tumor growth was arrested only by intratumoral LPS injection after the tumor was already established. This result was accompanied by a dramatic change in DC activation inside the tumor. Intratumoral LPS also enhanced antigen presentation and tumor-specific CD4+ T cell production of IFN-γ. Injection of LPS before tumor challenge or codelivery of tumor cells and LPS did not have any effect on tumor progression. Our results suggest that an efficient antitumor immune response leading to tumor regression can be achieved with proper TLR4 activation inside the tumor tissue, impacting the tumor microenvironment. These findings are relevant for the design of treatment for patients with malignant melanomas.

The immune system: endogenous anticancer mechanism

The genetic alterations acquired by cancer cells are identified by diverse immune mechanisms, creating a complex network of interactions that can either favor or control tumor growth. Defects and impairments in the immune system are associated with cancer development. Compelling new evidences are also available regarding the protective value of anti-tumor adaptive immune responses, both local and systemic, developed by the host. More recently, the identification of new subsets of T helper, T cytotoxic, and dendritic cells, unraveled new forms of interactions between immune and tumor cells. The immune system is a powerful ally in the control of cancer development, metastasis and recurrence, due to two important properties that are absent in most anti-cancer treatments--specificity, and long-lasting memory. These properties are being increasingly explored in cancer therapy, from the wide use of monoclonal antibodies to the still experimental dendritic cell based therapies. Now, more than ever, the preservation as well as the recruitment of immune responses in the host constitute important approaches to be applied in cancer therapy.

Impaired in vivo CD4+ T cell expansion and differentiation in aged mice is not solely due to T cell defects: decreased stimulation by aged dendritic cells

CD4+ T cells regulate humoral and cell-mediated immune responses, which are progressively impaired in aging, resulting in susceptibility to infections and cancer. Dendritic cells (DCs) are major activators of T cells, providing signals that drive their expansion and differentiation. In this study, we asked if decreased CD4+ T cell responses were influenced by the age of DCs rather than being exclusively due to T cell defects. Old T cells transferred to young recipients expanded and differentiated similarly to young T cells. However, aged recipients were poor stimulators of both old and young T cells, which failed to acquire CD44 expression and produce interferon gamma (IFN-γ). DCs in aged hosts expressed fewer MHC-peptide complexes. The CD86 expression in the DCs of both hosts was similar; however, CD40 levels were reduced in old DCs. Finally, old DCs failed to produce inflammatory cytokines in response to LPS. Our results indicate that the impairment of aged CD4+ T cell function is intimately related to multiple alterations in aged DCs, rather than being caused solely by intrinsic T cell defects, suggesting that the function of aged T cells may be partially rescued in vivo when appropriate stimulation is applied. These findings are relevant to vaccination design for elderly populations.

CD4+ T cell response against a non-tumor antigen is unaffected in melanoma-bearing mice

The tumor microenvironment is complex and creates an immunosuppressive network to tolerize tumor-specific immune responses; however, little information is available regarding the response against non-tumor antigens in tumor-bearing individuals. The goal of the present study was to evaluate if tumor burden could influence a CD4(+) T cell response against a soluble protein, not expressed by the tumor, in the absence of in vitro stimulation. Using an experimental system in which we can compare CD4(+) T cell responses to the Ea antigen when it is either expressed by B16F10 melanoma cells (B16EaRFP cells) or is an exogenous, non-tumor antigen (soluble EaRFP protein), in immunizations of B16F10 tumor-bearing mice, we observed that the tumor can modulate the CD4(+) T cell-specific response to the antigen when it is expressed by the tumor cells. TEa cells proliferated poorly and produced less IFN-γ in mice bearing B16F10 melanoma expressing Ea peptide, and tumor growth was impervious to this response. However, in mice bearing 7 days B16F10 tumors, not expressing the Ea antigen, priming of TEa cells was similar to that observed in tumor-free mice, based on the total number of cells recovered and proliferation assessed by CFSE dilution after EaRFP immunization. We also investigated if tumor burden could influence recall responses of already differentiated effector cells. We immunized mice with EaRFP antigen and after a few days injected B16F10 cells. After 10 days of tumor growth, we challenged the mice with the non-tumor antigen. We found that the number of TEa cells producing IFN-γ in tumor-bearing mice was not different compared to tumor-free mice. No differences in antigen presentation, assessed by YAe antibody staining, were verified in the draining lymph node of these two groups. Collectively, our data indicate that tumor burden does not affect immune responses to non-tumor antigens. These results have important implications in the design of anti-cancer therapy.