Prostaglandin E2 induction during mouse adenovirus type 1 respiratory infection regulates inflammatory mediator generation but does not affect viral pathogenesis

Immunological and Safety Profile of Bacteriophages Therapy: A preclinical Study

AIMS

Numerous pre-clinical and clinical studies have recently demonstrated the significant role of phage therapy in treating multidrug-resistant bacterial infections. However, only a few researchers have focused on monitoring the phage-mediated adverse reactions during phage therapy. The present study aimed to demonstrated the oral acute and sub-acute toxicity of bacteriophages (Klebsiella pneumoniae XDR strain) in Charles Foster rats with special reference to immunological response and adverse effects.

METHODS AND RESULTS

Bacteriophages were orally administered in dosages of 10¹⁰ PFU/mL and a 10¹⁵ PFU/mL to Charles Foster rats as a single dose (in acute toxicity study) and daily dosage for 28 days (in sub-acute toxicity study). One milliliter suspension of bacteriophages was administered through the oral gavage feeding tube. No adverse effect was observed in any of the experimental as well as in the control animals. Further, an insignificant change in food and water intake and body weight was observed throughout the study period compared with the control group rats. On the 28^th day of phage administration, blood was collected to estimate haematological, biochemical, and cytokines parameters. The data suggested no difference in the haematological, biochemical, and cytokine profile compared to the control group. No significant change in any of the treatment groups could be observed on the gross and histopathological examinations. The cytokines estimated, interleukin-1 beta (IL-1β), IL-4, IL-6, and IFN-gamma, were found within the normal range during the experiment.

CONCLUSIONS

The results concluded that no adverse effect, including the severe detrimental impact on oral administration of high (10¹⁰ PFU/mL) and very high dose (10¹⁵ PFU/mL) of the bacteriophages cocktail.

SIGNIFICANCE AND IMPACT OF STUDY

The high and long-term oral administration of bacteriophages did not induce noticeable immunological response as well.

Inhibition of microsomal prostaglandin E synthase-1 ameliorates acute lung injury in mice

Background

To examine the effects of BI 1029539 (GS-248), a novel selective human microsomal prostaglandin E synthase-1 (mPGES-1) inhibitor, in experimental models of acute lung injury (ALI) and sepsis in transgenic mice constitutively expressing the mPGES1 (Ptges) humanized allele.

Methods

Series 1: Lipopolysaccharide (LPS)-induced ALI. Mice were randomized to receive vehicle, BI 1029539, or celecoxib. Series 2: Cecal ligation and puncture-induced sepsis. Mice were randomized to receive vehicle or BI 1029539.

Results

Series 1: BI 1029539 or celecoxib reduced LPS-induced lung injury, with reduction in neutrophil influx, protein content, TNF-ɑ, IL-1β and PGE₂ levels in bronchoalveolar lavage (BAL), myeloperoxidase activity, expression of mPGES-1, cyclooxygenase (COX)-2 and intracellular adhesion molecule in lung tissue compared with vehicle-treated mice. Notably, prostacyclin (PGI₂) BAL concentration was only lowered in celecoxib-treated mice. Series 2: BI 1029539 significantly reduced sepsis-induced BAL inflammatory cell recruitment, lung injury score and lung expression of mPGES-1 and inducible nitric oxide synthase. Treatment with BI 1029539 also significantly prolonged survival of mice with severe sepsis. Anti-inflammatory and anti-migratory effect of BI 1029539 was confirmed in peripheral blood leukocytes from healthy volunteers.

Conclusions

BI 1029539 ameliorates leukocyte infiltration and lung injury resulting from both endotoxin-induced and sepsis-induced lung injury.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03016-9.

Study on the Effect of Oral Administration of Bacteriophages in Charles Foster Rats With Special Reference to Immunological and Adverse Effects

Numerous pre-clinical and clinical studies have recently demonstrated the significant role of phage therapy in treating multidrug-resistant bacterial infections. However, only a few researchers have focused on monitoring the phage-mediated adverse reactions during phage therapy. Besides adverse reactions, immunological response after short- and long-term oral administration of bacteriophages is also lacking. In this study, we administered the bacteriophages orally against Klebsiella pneumoniae XDR strain in dosages of 10¹⁵ PFU/ml and a 10²⁰ PFU/ml (still higher) to Charles Foster rats as a single dose (in acute toxicity study) and daily dosage for 28 days (in sub-acute toxicity study). One milliliter suspension of bacteriophages was administered through the oral gavage feeding tube. No adverse effect was observed in any of the experimental as well as in the control animals.Further, an insignificant change in food and water intake and body weight was observed throughout the study period compared with the control group rats. On the 28th day of phage administration, blood was collected to estimate hematological, biochemical, and cytokines parameters. The data suggested no difference in the hematological, biochemical, and cytokine profile compared to the control group. No significant change in any of the treatment groups could be observed on the gross and histopathological examinations. The cytokines estimated, interleukin-1 beta (IL-1β), IL-4, IL-6, and INF-gamma, were found within the normal range during the experiment. The results suggested no adverse effect, including the severe detrimental impact on oral administration of high (10¹⁵ PFU/ml) and very high dose (10²⁰ PFU/ml) of the bacteriophages cocktail. The high and long-term oral administration of bacteriophages did not induce noticeable immunological response as well.

Postinfectious Bronchiolitis Obliterans in Children: Diagnostic Workup and Therapeutic Options: A Workshop Report

Bronchiolitis obliterans (BO) is a rare, chronic form of obstructive lung disease, often initiated with injury of the bronchiolar epithelium followed by an inflammatory response and progressive fibrosis of small airways resulting in nonuniform luminal obliteration or narrowing. The term BO comprises a group of diseases with different underlying etiologies, courses, and characteristics. Among the better recognized inciting stimuli leading to BO are airway pathogens such as adenovirus and mycoplasma, which, in a small percentage of infected children, will result in progressive fixed airflow obstruction, an entity referred to as postinfectious bronchiolitis obliterans (PIBO). The present knowledge on BO in general is reasonably well developed, in part because of the relatively high incidence in patients who have undergone lung transplantation or bone marrow transplant recipients who have had graft-versus-host disease in the posttransplant period. The cellular and molecular pathways involved in PIBO, while assumed to be similar, have not been adequately elucidated. Since 2016, an international consortium of experts with an interest in PIBO assembles on a regular basis in Geisenheim, Germany, to discuss key areas in PIBO which include diagnostic workup, treatment strategies, and research fields.

Murine adenoviruses: tools for studying adenovirus pathogenesis in a natural host

Small laboratory animals are powerful models for investigating in vivo viral pathogenesis of a number of viruses. For adenoviruses (AdVs), however, species-specificity poses limitations to studying human adenoviruses (HAdVs) in mice and other small laboratory animals. Thus, this review covers work on naturally occurring mouse AdVs, primarily mouse adenovirus type 1 (MAdV-1), a member of the species Murine mastadenovirus A. Molecular genetics, virus life cycle, cell and tissue tropism, interactions with the host immune response, persistence, and host genetics of susceptibility are described. A brief discussion of MAdV-2 (member of species Murine mastadenovirus B) and MAdV-3 (member of species Murine mastadenovirus C) is included. We report the use of MAdVs in the development of vectors and vaccines.

Fas activity mediates airway inflammation during mouse adenovirus type 1 respiratory infection

CD8 T cells play a key role in clearance of mouse adenovirus type 1 (MAV-1) from the lung and contribute to virus-induced airway inflammation. We tested the hypothesis that interactions between Fas ligand (FasL) and Fas mediate the antiviral and proinflammatory effects of CD8 T cells. FasL and Fas expression were increased in the lungs of C57BL/6 (B6) mice during MAV-1 respiratory infection. Viral replication and weight loss were similar in B6 and Fas-deficient (lpr) mice. Histological evidence of pulmonary inflammation was similar in B6 and lpr mice, but lung mRNA levels and airway proinflammatory cytokine concentrations were lower in MAV-1-infected lpr mice compared to infected B6 mice. Virus-induced apoptosis in lungs was not affected by Fas deficiency. Our results suggest that the proinflammatory effects of CD8 T cells during MAV-1 infection are mediated in part by Fas activation and are distinct from CD8 T cell antiviral functions.

Mouse adenovirus type 1 infection of adipose tissue

Human adenovirus (HAdV) type 36 seropositivity has been linked to obesity in humans. That link is supported by a small number of studies using HAdV-36 infection of animals that are not natural hosts for HAdVs. In this study, we infected mice with mouse adenovirus type 1 (MAV-1), a mouse pathogen, to determine whether MAV-1 infected adipose tissue and was associated with adipose tissue inflammation and obesity. We detected MAV-1 in adipose tissue during acute MAV-1 infection, but we did not detect virus-induced increases in adipose tissue cytokine expression or histological evidence of adipose tissue inflammation during acute infection. MAV-1 did not persist in adipose tissue at later times, and we did not detect long-term adipose inflammation, increased adipose tissue mass, or body weight in infected mice. Our data indicate that MAV-1 is not associated with obesity in infected mice.

Contributions of CD8 T cells to the pathogenesis of mouse adenovirus type 1 respiratory infection

CD8 T cells are key components of the immune response to viruses, but their roles in the pathogenesis of adenovirus respiratory infection have not been characterized. We used mouse adenovirus type 1 (MAV-1) to define CD8 T cell contributions to the pathogenesis of adenovirus respiratory infection. CD8 T cell deficiency in β2m^-/- mice had no effect on peak viral replication in lungs, but clearance of virus was delayed in β2m^-/- mice. Virus-induced weight loss and increases in bronchoalveolar lavage fluid total protein, IFN-γ, TNF-α, IL-10, CCL2, and CCL5 concentrations were less in β2m^-/- mice than in controls. CD8 T cell depletion had similar effects on virus clearance, weight loss, and inflammation. Deficiency of IFN-γ or perforin had no effect on viral replication or inflammation, but perforin-deficient mice were partially protected from weight loss. CD8 T cells promote MAV-1-induced pulmonary inflammation via a mechanism that is independent of direct antiviral effects.

Interferon-dependent immunoproteasome activity during mouse adenovirus type 1 infection

The immunoproteasome is an inducible host mechanism that aids in the clearance of damaged proteins. The immunoproteasome also influences immune function by enhancing peptide presentation by MHC class I and promotes inflammation via IκB degradation and activation of NF-κB. We used mouse adenovirus type 1 (MAV-1) to characterize the role of the immunoproteasome in adenovirus pathogenesis. Following intranasal infection of mice, immunoproteasome activity in the heart and lung was significantly increased in an IFN-γ-dependent manner. Absence of the β5i immunoproteasome subunit and pharmacological inhibition of β5i activity had minimal effects on viral replication, virus-induced cellular inflammation, or induction of cytokine expression. Likewise, the establishment of protective immunity following primary infection was not significantly altered by β5i deficiency. Thus, although immunoproteasome activity is robustly induced during acute infection with MAV-1, our data suggest that other mechanisms are capable of compensating for immunoproteasome activity to maintain antiviral immunity and appropriate inflammatory responses.

Alveolar Epithelial Cell-Derived Prostaglandin E2 Serves as a Request Signal for Macrophage Secretion of Suppressor of Cytokine Signaling 3 during Innate Inflammation

Preservation of gas exchange mandates that the pulmonary alveolar surface restrain unnecessarily harmful inflammatory responses to the many challenges to which it is exposed. These responses reflect the cross-talk between alveolar epithelial cells (AECs) and resident alveolar macrophages (AMs). We recently determined that AMs can secrete suppressor of cytokine signaling (SOCS) proteins within microparticles. Uptake of these SOCS-containing vesicles by epithelial cells inhibits cytokine-induced STAT activation. However, the ability of epithelial cells to direct AM release of SOCS-containing vesicles in response to inflammatory insults has not been studied. In this study, we report that SOCS3 protein was elevated in bronchoalveolar lavage fluid of both virus- and bacteria-infected mice, as well as in an in vivo LPS model of acute inflammation. In vitro studies revealed that AEC-conditioned medium (AEC-CM) enhanced AM SOCS3 secretion above basal levels. Increased amounts of PGE2 were present in AEC-CM after LPS challenge, and both pharmacologic inhibition of PGE2 synthesis in AECs and neutralization of PGE2 in AEC-CM implicated this prostanoid as the major AEC-derived factor mediating enhanced AM SOCS3 secretion. Moreover, pharmacologic blockade of PGE2 synthesis or genetic deletion of a PGE2 synthase similarly attenuated the increase in bronchoalveolar lavage fluid SOCS3 noted in lungs of mice challenged with LPS in vivo. These results demonstrate a novel tunable form of cross-talk in which AECs use PGE2 as a signal to request SOCS3 from AMs to dampen their endogenous inflammatory responses during infection.

Increased lethality and defective pulmonary clearance of Streptococcus pneumoniae in microsomal prostaglandin E synthase-1-knockout mice

The production of prostaglandin E2 (PGE2) increases dramatically during pneumococcal pneumonia, and this lipid mediator impairs alveolar macrophage (AM)-mediated innate immune responses. Microsomal prostaglandin E synthase-1 (mPGES-1) is a key enzyme involved in the synthesis of PGE2, and its expression is enhanced during bacterial infections. Genetic deletion of mPGES-1 in mice results in diminished PGE2 production and elevated levels of other prostaglandins after infection. Since PGE2 plays an important immunoregulatory role during bacterial pneumonia we assessed the impact of mPGES-1 deletion in the host defense against pneumococcal pneumonia in vivo and in AMs in vitro. Wild-type (WT) and mPGES-1 knockout (KO) mice were challenged with Streptococcus pneumoniae via the intratracheal route. Compared with WT animals, we observed reduced survival and increased lung and spleen bacterial burdens in mPGES-1 KO mice 24 and 48 h after S. pneumoniae infection. While we found modest differences between WT and mPGES-1 KO mice in pulmonary cytokines, AMs from mPGES-1 KO mice exhibited defective killing of ingested bacteria in vitro that was associated with diminished inducible nitric oxide synthase expression and reduced nitric oxide (NO) synthesis. Treatment of AMs from mPGES-1 KO mice with an NO donor restored bacterial killing in vitro. These results suggest that mPGES-1 plays a critical role in bacterial pneumonia and that genetic ablation of this enzyme results in diminished pulmonary host defense in vivo and in vitro. These results suggest that specific inhibition of PGE2 synthesis by targeting mPGES-1 may weaken host defense against bacterial infections.

Prostaglandin E2 production during neonatal respiratory infection with mouse adenovirus type 1

Neonatal mice are more susceptible than adults to mouse adenovirus type 1 (MAV1) respiratory infection. In adult mice, MAV-1 respiratory infection induces production of prostaglandin E2 (PGE2), a lipid mediator that exerts suppressive effects on a variety of host immune functions. We tested the hypothesis that exaggerated PGE2 production in neonatal mice contributes to increased susceptibility to MAV-1. PGE2 concentrations were lower in lungs of uninfected neonatal mice than in adults. PGE2 production was induced by both MAV-1 and a nonspecific stimulus to a greater degree in neonatal mice than in adults, but only in adults was PGE2 induced in a virus-specific manner. Lung viral loads were equivalent in PGE2-deficient neonatal mice and wild type controls, as was virus-induced expression of IFN-γ, IL-17A, and CCL5 in the lungs. PGE2 deficiency had minimal effect on production of virus-specific IgG or establishment of protective immunity in neonatal mice. Collectively, our data indicate that lung PGE2 production is exaggerated early in life, but this effect does not mediate increased susceptibility to MAV-1 infection.

Xenogenic Adenoviral Vectors

Many nonhuman adenoviruses (AdVs) of simian, bovine, porcine, canine, ovine, murine, and fowl origin are being developed as gene delivery systems for recombinant vaccines and gene therapy applications. In addition to circumventing preexisting human AdV (HAdV) immunity, nonhuman AdV vectors utilize coxsackievirus-adenovirus receptor or other receptors for vector internalization, thereby expanding the range of cell types that can be targeted. Nonhuman AdV vectors also provide excellent platforms for veterinary vaccines. A specific nonhuman AdV vector when used in its species of origin could provide an excellent animal model for evaluating the vector efficacy and pathogenesis. These vectors are useful in prime–boost approaches with other AdV vectors or with other gene delivery systems including DNA immunization and viral or bacterial vectors. When multiple vector inoculations are required, nonhuman AdV vectors could supplement HAdV or other viral vectors.

Prostaglandin E2 Production and T Cell Function in Mouse Adenovirus Type 1 Infection following Allogeneic Bone Marrow Transplantation

Adenovirus infections are important complications of bone marrow transplantation (BMT). We demonstrate delayed clearance of mouse adenovirus type 1 (MAV-1) from lungs of mice following allogeneic BMT. Virus-induced prostaglandin E₂ (PGE₂) production was greater in BMT mice than in untransplanted controls, but BMT using PGE₂-deficient donors or recipients failed to improve viral clearance, and treatment of untransplanted mice with the PGE₂ analog misoprostol did not affect virus clearance. Lymphocyte recruitment to the lungs was not significantly affected by BMT. Intracellular cytokine staining of lung lymphocytes demonstrated impaired production of INF-γ and granzyme B by cells from BMT mice, and production of IFN-γ, IL-2, IL-4, and IL-17 following ex vivo stimulation was impaired in lymphocytes obtained from lungs of BMT mice. Viral clearance was not delayed in untransplanted INF-γ-deficient mice, suggesting that delayed viral clearance in BMT mice was not a direct consequence of impaired IFN-γ production. However, lung viral loads were higher in untransplanted CD8-deficient mice than in controls, suggesting that delayed MAV-1 clearance in BMT mice is due to defective CD8 T cell function. We did not detect significant induction of IFN-β expression in lungs of BMT mice or untransplanted controls, and viral clearance was not delayed in untransplanted type I IFN-unresponsive mice. We conclude that PGE₂ overproduction in BMT mice is not directly responsible for delayed viral clearance. PGE₂-independent effects on CD8 T cell function likely contribute to the inability of BMT mice to clear MAV-1 from the lungs.

Proinflammatory effects of interferon gamma in mouse adenovirus 1 myocarditis

Adenoviruses are frequent causes of pediatric myocarditis. Little is known about the pathogenesis of adenovirus myocarditis, and the species specificity of human adenoviruses has limited the development of animal models, which is a significant barrier to strategies for prevention or treatment. We have developed a mouse model of myocarditis following mouse adenovirus 1 (MAV-1) infection to study the pathogenic mechanisms of this important cause of pediatric myocarditis. Following intranasal infection of neonatal C57BL/6 mice, we detected viral replication and induction of interferon gamma (IFN-γ) in the hearts of infected mice. MAV-1 caused myocyte necrosis and induced substantial cellular inflammation that was composed predominantly of CD3(+) T lymphocytes. Depletion of IFN-γ during acute infection reduced cardiac inflammation in MAV-1-infected mice without affecting viral replication. We observed decreased contractility during acute infection of neonatal mice, and persistent viral infection in the heart was associated with cardiac remodeling and hypertrophy in adulthood. IFN-γ is a proinflammatory mediator during adenovirus-induced myocarditis, and persistent adenovirus infection may contribute to ongoing cardiac dysfunction.

IMPORTANCE

Studying the pathogenesis of myocarditis caused by different viruses is essential in order to characterize both virus-specific and generalized factors that contribute to disease. Very little is known about the pathogenesis of adenovirus myocarditis, which is a significant impediment to the development of treatment or prevention strategies. We used MAV-1 to establish a mouse model of human adenovirus myocarditis, providing the means to study host and pathogen factors contributing to adenovirus-induced cardiac disease during acute and persistent infection. The MAV-1 model will enable fundamental studies of viral myocarditis, including IFN-γ modulation as a therapeutic strategy.

Observation of inflammatory responses in mice orally fed with bacteriophage T7

AIMS

Analysis of inflammatory immune response upon bacteriophage intake in mice.

METHODS AND RESULTS

Bacteriophage therapy is emerging as an effective alternative to conventional antibiotics. However, its safety when applied to humans and animals remains a prime concern. This study investigated the inflammatory responses in mice fed orally with bacteriophages. The mice were fed with either murine norovirus (MNV) or bacteriophage T7 for 10 days and then sacrificed. No behavioural changes related to diet, movement or defecation were observed in either group. The inflammatory cytokine profiling showed an increased level of interleukins 1α (IL-1α), 1β (IL-1β), 2 (IL-2), 10 (IL-10), 12 (IL-12), 17A (IL-17A), interferon-γ (IFN-γ), tumour necrosis factor-α (TNF-α), granulocyte colony-stimulating factor (G-CSF) and granulocyte macrophage colony-stimulating factor (GM-CSF) in the serum from the mice fed with MNV, whereas only a slight increase in IL-17A was observed in the serum from the mice fed with bacteriophage T7. A histopathological analysis of tissue samples from the stomach, small intestine and colon revealed no significant pathological change.

CONCLUSIONS

The bacteriophage diet only caused a minimal inflammatory response in the mice.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides insights into safety concerns of orally fed bacteriophage therapy.

IL-17 contributes to neutrophil recruitment but not to control of viral replication during acute mouse adenovirus type 1 respiratory infection

IL-17-producing CD4(+) helper T cells (Th17 cells) promote inflammatory responses to many pathogens. We used mouse adenovirus type 1 (MAV-1) to determine contributions of IL-17 to adenovirus pathogenesis. MAV-1 infection of C57BL/6 mice upregulated lung expression of IL-17 and the Th17-associated factors IL-23 and RORγt. Only CD4(+)T cells were associated with virus-specific IL-17 production. Fewer neutrophils were recruited to airways of IL-17(-/-) mice following MAV-1 infection, but there were no other differences in pulmonary inflammation between IL-17(+/+) and IL-17(-/-) mice. Mice depleted of neutrophils using anti-Gr-1 antibody had greater lung viral loads than controls. Despite impaired neutrophil recruitment, there were no differences between IL-17(+/+) and IL-17(-/-) mice in peak lung viral loads, clearance of virus from the lungs, or establishment of protective immunity. We demonstrate robust Th17 responses during MAV-1 respiratory infection, but these responses are not essential for control of virus infection or for virus-induced pulmonary inflammation.