Deficiency of LIGHT signaling pathway exacerbates Chlamydia psittaci respiratory tract infection in mice

Reactive Oxygen Species Modulate Th17/Treg Balance in Chlamydia psittaci Pneumonia via NLRP3/IL-1β/Caspase-1 Pathway Differentiation

Chlamydia psittaci pneumonia (CPP) is a lung disease caused by the infection with the Chla-mydia psittaci bacterium, which can lead to severe acute respiratory distress syndrome and systemic symptoms. This study explored the specific mechanisms underlying the impact of reactive oxygen species (ROS) on the Th17/Treg balance in CPP. The levels of ROS and the differentiation ratio of Th17/Treg in the peripheral blood of healthy individuals and CPP patients were measured using ELISA and flow cytometry, respectively. The association between the ROS levels and Th17/Treg was assessed using Pearson correlation analysis. The ROS levels and the Th17/Treg ratio were measured in CD4+ T cells following H2O2 treatment and NLRP3 inhibition. The effects of H2O2 treatment and NLRP3 inhibition on the NLRP3/IL-1β/caspase-1 pathway were observed using immunoblotting. Compared to the healthy group, the CPP group exhibited increased levels of ROS in the peripheral blood, an elevated ratio of Th17 differentiation, and a decreased ratio of Treg differentiation. ROS levels were positively correlated with the Th17 cell proportion but negatively correlated with the Treg cell proportion. The ROS levels and NLRP3/IL-1β/caspase-1 expression were up-regulated in CD4+ T cells after H2O2 treatment. Furthermore, there was an increase in Th17 differentiation and a decrease in Treg differentiation. Conversely, the NLRP3/IL-1β/caspase-1 pathway inhibition reversed the effects of H2O2 treatment, with no significant change in the ROS levels. ROS regulates the Th17/Treg balance in CPP, possibly through the NLRP3/IL-1β/caspase-1 pathway. This study provides a new perspective on the development of immunotherapy for CPP.

Pneumonia in the first week after polytrauma is associated with reduced blood levels of soluble herpes virus entry mediator

Background

Pneumonia develops frequently after major surgery and polytrauma and thus in the presence of systemic inflammatory response syndrome (SIRS) and organ dysfunction. Immune checkpoints balance self-tolerance and immune activation. Altered checkpoint blood levels were reported for sepsis. We analyzed associations of pneumonia incidence in the presence of SIRS during the first week of critical illness and trends in checkpoint blood levels.

Materials and methods

Patients were studied from day two to six after admission to a surgical intensive care unit (ICU). Blood was sampled and physician experts retrospectively adjudicated upon the presence of SIRS and Sepsis-1/2 every eight hours. We measured the daily levels of immune checkpoints and inflammatory markers by bead arrays for polytrauma patients developing pneumonia. Immune checkpoint time series were additionally determined for clinically highly similar polytrauma controls remaining infection-free during follow-up. We performed cluster analyses. Immune checkpoint time trends in cases and controls were compared with hierarchical linear models. For patients with surgical trauma and with and without sepsis, selected immune checkpoints were determined in study baseline samples.

Results

In polytrauma patients with post-injury pneumonia, eleven immune checkpoints dominated subcluster 3 that separated subclusters 1 and 2 of myeloid markers from subcluster 4 of endothelial activation, tissue inflammation, and adaptive immunity markers. Immune checkpoint blood levels were more stable in polytrauma cases than controls, where they trended towards an increase in subcluster A and a decrease in subcluster B. Herpes virus entry mediator (HVEM) levels (subcluster A) were lower in cases throughout. In unselected surgical patients, sepsis was not associated with altered HVEM levels at the study baseline.

Conclusion

Pneumonia development after polytrauma until ICU-day six was associated with decreased blood levels of HVEM. HVEM signaling may reduce pneumonia risk by strengthening myeloid antimicrobial defense and dampening lymphoid-mediated tissue damage. Future investigations into the role of HVEM in pneumonia and sepsis development and as a predictive biomarker should consider the etiology of critical illness and the site of infection.

Systemic immune profiling of Omicron-infected subjects inoculated with different doses of inactivated virus vaccine

SARS-CoV-2 primary strain-based vaccination exerts a protective effect against Omicron variants-initiated infection, symptom occurrence, and disease severity in a booster-dependent manner. Yet, the underlying mechanisms remain unclear. During the 2022 Omicron outbreak in Shanghai, we enrolled 122 infected adults and 50 uninfected controls who had been unvaccinated or vaccinated with two or three doses of COVID-19 inactive vaccines and performed integrative analysis of 41-plex CyTOF, RNA-seq, and Olink on their peripheral blood samples. The frequencies of HLA-DRhi classical monocytes, non-classical monocytes, and Th1-like Tem tended to increase, whereas the frequency of Treg was reduced by booster vaccine, and they influenced symptom occurrence in a vaccine dose-dependent manner. Intercorrelation and mechanistic analysis suggested that the booster vaccination induced monocytic training, which would prime monocytic activation and maturation rather than differentiating into myeloid-derived suppressive cells upon Omicron infections. Overall, our study provides insights into how booster vaccination elaborates protective immunity across SARS-CoV-2 variants.

Lymphocyte HVEM/BTLA co-expression after critical illness demonstrates severity indiscriminate upregulation, impacting critical illness-induced immunosuppression

Introduction

The co-regulatory molecule, HVEM, can stimulate or inhibit immune function, but when co-expressed with BTLA, forms an inert complex preventing signaling. Altered HVEM or BTLA expression, separately have been associated with increased nosocomial infections in critical illness. Given that severe injury induces immunosuppression, we hypothesized that varying severity of shock and sepsis in murine models and critically ill patients would induce variable increases in HVEM/BTLA leukocyte co-expression.

Methods

In this study, varying severities of murine models of critical illness were utilized to explore HVEM⁺BTLA⁺ co-expression in the thymic and splenic immune compartments, while circulating blood lymphocytes from critically ill patients were also assessed for HVEM⁺BTLA⁺ co-expression.

Results

Higher severity murine models resulted in minimal change in HVEM⁺BTLA⁺ co-expression, while the lower severity model demonstrated increased HVEM⁺BTLA⁺ co-expression on thymic and splenic CD4⁺ lymphocytes and splenic B220⁺ lymphocytes at the 48-hour time point. Patients demonstrated increased co-expression of HVEM⁺BTLA⁺ on CD3⁺ lymphocytes compared to controls, as well as CD3⁺Ki67^- lymphocytes. Both L-CLP 48hr mice and critically ill patients demonstrated significant increases in TNF-α.

Discussion

While HVEM increased on leukocytes after critical illness in mice and patients, changes in co-expression did not relate to degree of injury severity of murine model. Rather, co-expression increases were seen at later time points in lower severity models, suggesting this mechanism evolves temporally. Increased co-expression on CD3⁺ lymphocytes in patients on non-proliferating cells, and associated TNF-α level increases, suggest post-critical illness co-expression does associate with developing immune suppression.

Analysis of microRNA expression profiles in human bronchial epithelial cells infected by Chlamydia psittaci

BACKGROUND

Chlamydia psittaci is a pathogen of birds that can cause zoonotic disease in mammals including pneumonia in humans. MicroRNAs (miRNAs) are a class of small non-coding RNA fragments with a length of about 22 nt, which play an important role in regulating gene expression after transcription. Chlamydia infection can cause changes in host cell miRNA expression, but the potential biological function of miRNAs in C. psittaci infection and pathogenesis is not well understood.

METHODS

Small RNA sequencing (sRNA-Seq) technology was used to characterise miRNA expression in human bronchial epithelial (HBE) cells after C. psittaci infection, and differentially expressed miRNAs were identified. Candidate target genes for these miRNAs were then functionally annotated by Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. The sRNA-Seq results were partially validated by quantitative real time polymerase chain reaction (qRT-PCR) and miRNA-target networks were constructed using visualization software.

RESULTS

We identified 151 differentially expressed miRNAs (46 known miRNAs and 105 novel miRNAs) in C. psittaci-infected HBE cells, of which 140 were upregulated and 11 were downregulated. Of these, 17 known miRNAs were significantly upregulated and two were downregulated using P < 0.05 and |log₂FoldChange|>1.5 as threshold criteria. GO enrichment results showed that the predicted targets of these differentially expressed miRNAs were mainly involved in transcriptional regulation and ATP binding. KEGG pathway analysis suggested that the candidate target genes were involved in several important signaling pathways such as MAPK, ErbB, cGMP-PKG, cAMP, mTOR, GNRH, oxytocin, PI3K-Akt and AMPK, which are primarily related to biological processes such as transcription and signal transduction. The qRT-PCR results for miR-2116-3p, miR-3195, miR-663a, miR-10401-5p, miR-124-3p, miR-184, miR-744-5p and hsa-miR-514b-5p were consistent with the sRNA-Seq data.

CONCLUSIONS

A large amount of miRNA expression profile data relating to C. psittaci infection was obtained, which provides a useful experimental and theoretical basis for further understanding the pathogenic mechanisms of C. psittaci infection.

Check Point Inhibitors and Their Role in Immunosuppression in Sepsis

Checkpoint regulators are a group of membrane-bound receptors or ligands expressed on immune cells to regulate the immune cell response to antigen presentation and other immune stimuli, such as cytokines, chemokines, and complement. In the context of profound immune activation, such as sepsis, the immune system can be rendered anergic by these receptors to prevent excessive inflammation and tissue damage. If this septic immunosuppression is prolonged, the host is unable to mount the appropriate immune response to a secondary insult or infection. This article describes the manner in which major regulators in the B7-CD28 family and their ligands mediate immunosuppression in sepsis.

Herpes Virus Entry Mediator (HVEM): A Novel Potential Mediator of Trauma-Induced Immunosuppression

BACKGROUND

Herpes virus entry mediator (HVEM) is a coinhibitory molecule which can both stimulate and inhibit host immune responses. Altered expression of HVEM and its ligands is associated with increased nosocomial infections in septic patients. We hypothesize critically ill trauma patients will display increased lymphocyte HVEM expression and that such alteration is predictive of infectious events.

MATERIALS AND METHODS

Trauma patients prospectively enrolled from the ICU were compared with healthy controls. Leukocytes were isolated from whole blood, stained for CD3 (lymphocytes) and HVEM, and evaluated by flow cytometry. Charts were reviewed for injuries sustained, APACHE II score, hospital course, and secondary infections.

RESULTS

Trauma patients (n = 31) were older (46.7 ± 2.4 versus 36.8 ± 2.1 y; P = 0.03) than healthy controls (n = 10), but matched for male sex (74% versus 60%; P = 0.4). Trauma patients had higher presenting WBC (13.9 ± 1.3 versus 5.6 ± 0.5 × 106/mL; P = 0.002), lower percentage of CD3+ lymphocytes (7.5% ± 0.8 versus 22.5% ± 0.9; P < 0.001), but significantly greater expression of HVEM+/CD3+ lymphocytes (89.6% ± 1.46 versus 67.3% ± 1.7; P < 0.001). Among trauma patients, secondary infection during the hospitalization was associated with higher APACHE II scores (20.6 ± 1.6 versus 13.6 ± 1.4; P = 0.03) and markedly lower CD3+ lymphocyte HVEM expression (75% ± 2.6 versus 93% ± 0.7; P < 0.01).

CONCLUSIONS

HVEM expression on CD3+ cells increases after trauma. Patients developing secondary infections have less circulating HVEM+CD3+. This implies HVEM signaling in lymphocytes plays a role in maintaining host defense to infection in after trauma. HVEM expression may represent a marker of infectious risk as well as a potential therapeutic target, modulating immune responses to trauma.

The JAK/STAT3 signaling pathway mediates inhibition of host cell apoptosis by Chlamydia psittaci infection

The JAK-STAT3 signaling pathway is a key regulator of cell growth, motility, migration, invasion and apoptosis in mammalian cells. Infection with intracellular pathogens of the genus Chlamydia can inhibit host cell apoptosis, and here we asked whether the JAK-STAT3 pathway participates in chlamydial anti-apoptotic activity. We found that, compared with uninfected cells, levels of JAK1 and STAT3 mRNA as well as total and phosphorylated JAK1 and STAT3 protein, were significantly increased in C. psittaci-infected HeLa cells. Moreover, the apoptosis rate of infected cells was higher after treatment with the tyrosine kinase inhibitor AG-490 (2-cyano-3-(3, 4-dihydroxyphenyl)-N-(phenylmethyl)-2-propenamide). Immunoblotting of apoptosis-related proteins showed that C. psittaci infection reduces Bax, but increases Bcl-2, protein levels, resulting in reduced activation of caspase-3, caspase-7, caspase-9 and PARP; AG490 attenuates these effects. Together, our data suggest that the JAK/STAT3 signaling pathway facilitates the anti-apoptotic effect of C. psittaci infection by reducing the Bax/Bcl-2 apoptotic switch ratio, and by inhibiting the intracellular activation of key pro-apoptotic enzymes.

The TNF Superfamily Molecule LIGHT Promotes the Generation of Circulating and Lung-Resident Memory CD8 T Cells following an Acute Respiratory Virus Infection

The transition of effector T cells or memory precursors into distinct long-lived memory T cell subsets is not well understood. Although many molecules made by APCs can contribute to clonal expansion and effector cell differentiation, it is not clear if clonal contraction and memory development is passive or active. Using respiratory virus infection, we found that CD8 T cells that cannot express the TNF family molecule lymphotoxin-like, exhibits inducible expression, competes with HSV glycoprotein D for herpes virus entry mediator, a receptor expressed by T lymphocytes (LIGHT) are unimpaired in their initial response and clonally expand to form effector cell pools. Thereafter, LIGHT-deficient CD8 T cells undergo strikingly enhanced clonal contraction with resultant compromised accumulation of both circulating and tissue-resident memory cells. LIGHT expression at the peak of the effector response regulates the balance of several pro- and antiapoptotic genes, including Akt, and has a preferential impact on the development of the peripheral memory population. These results underscore the importance of LIGHT activity in programming memory CD8 T cell development, and suggest that CD8 effector T cells can dictate their own fate into becoming memory cells by expressing LIGHT.