Transcriptomic Analysis Reveals Significant B Lymphocyte Suppression in Corticosteroid-Treated Hosts with Pneumocystis Pneumonia

A combined immune and inflammatory indicator predict the prognosis of severe Pneumocystis jirovecii pneumonia patients: a 12-year, retrospective, observational cohort

Persistent inflammatory damage and suppressed immune function play a crucial role in the pathogenesis and progression of the pneumocystis jirovecii pneumonia (PjP). Therefore, we aimed to investigate the correlation between the combined immune and inflammatory indicator: the neutrophil-to-lymphocyte ratio (NLR) and prognosis of non-human immunodeficiency virus (non-HIV) PjP.In the retrospective analysis conducted in ICUs at Beijing Chao-Yang Hospital, we examined data from 157 patients diagnosed with non-HIV PjP. Our findings reveal a concerning hospital mortality rate of 43.3%, with the 28-day mortality rate reaching 47.8%.Through multivariable logistic and Cox regression analyses, we established a significant association between elevated NLR levels and hospital mortality (adjusted odd ratio, 1.025; 95% CI, 1.008-1.043; p = 0.004) or 28-day mortality (adjusted hazard ratio, 1.026; 95% CI, 1.008-1.045; p = 0.005). Specifically, patients with an NLR exceeding 20.3 demonstrated markedly lower overall survival rates, underscoring the biomarker's predictive value for both hospital and 28-day mortality.In conclusion, non-HIV PjP patients in the ICU still have a high rate of mortality and a poor short-term prognosis after discharge. A high level of NLR was associated with an increased risk of hospital mortality and 28-day mortality.

Integrated analysis of microbiome and host transcriptome unveils correlations between lung microbiota and host immunity in bronchoalveolar lavage fluid of pneumocystis pneumonia patients

OBJECTIVE

The lung microbiota of patients with pulmonary diseases is disrupted and impacts the immunity. The microbiological and immune landscape of the lungs in patients with pneumocystis pneumonia (PCP) remains poorly understood.

METHODS

Multi-omics analysis and machine learning were performed on bronchoalveolar lavage fluid to explore interaction between the lung microbiota and host immunity in PCP. Then we constructed a diagnostic model using differential genes with LASSO regression and validated by qPCR. The immune infiltration analysis was performed to explore the landscape of lung immunity in patients with PCP.

RESULTS

Patients with PCP showed a low alpha diversity of lung microbiota, accompanied by the elevated abundance of Firmicutes, and the differential expressed genes (DEGs) analysis displayed a downregulation of MAPK signaling. The MAPK10, TGFB1, and EFNA3 indicated a potential to predict PCP (AUC = 0.86). The lung immune landscape in PCP showed the lower levels of naïve CD4+ T cells and activated dendritic cells. The correlation analysis of the MAPK signaling pathway-related DEGs and the differential microorganisms at the level of phylum showed that the Firmicutes was negatively correlated with these DEGs.

CONCLUSION

We profiled the characteristics of lung microbiota and immune landscape in PCP, which may contribute to elucidating the mechanism of PCP.

Immunoglobulins in COVID-19 pneumonia: from the acute phase to the recovery phase

BACKGROUND

COVID-19 pneumonia causes hyperinflammatory response that culminates in acute respiratory syndrome (ARDS) related to increased multiorgan dysfunction and mortality risk. Antiviral-neutralizing immunoglobulins production reflect the host humoral status and illness severity, and thus, immunoglobulin (Ig) circulating levels could be evidence of COVID-19 prognosis.

METHODS

The relationship among circulating immunoglobulins (IgA, IgG, IgM) and COVID-19 pneumonia was evaluated using clinical information and blood samples in a COVID-19 cohort composed by 320 individuals recruited during the acute phase and followed up to 4 to 8 weeks (n = 252) from the Spanish first to fourth waves.

RESULTS

COVID-19 pneumonia development depended on baseline Ig concentrations. Circulating IgA levels together with clinical features at acute phase was highly associated with COVID-19 pneumonia development. IgM was positively correlated with obesity (ρb = 0.156, P = 0.020), dyslipemia (ρb = 0.140, P = 0.029), COPD (ρb = 0.133, P = 0.037), cancer (ρb = 0.173, P = 0.007) and hypertension (ρb = 0.148, P = 0.020). Ig concentrations at recovery phase were related to COVID-19 treatments.

CONCLUSIONS

Our results provide valuable information on the dynamics of immunoglobulins upon SARS-CoV-2 infection or other similar viruses.

Risk-Benefit Analysis of Primary Prophylaxis Against Pneumocystis Jirovecii Pneumonia in Patients With Rheumatic Diseases Receiving Rituximab

OBJECTIVE

To identify a specific population of patients with rheumatic diseases receiving rituximab treatment for whom the benefit from primary prophylaxis against Pneumocystis jirovecii pneumonia (PJP) outweighs the risk of adverse events (AEs).

METHODS

This study included 818 patients treated with rituximab for rheumatic diseases, among whom 419 received prophylactic trimethoprim/sulfamethoxazole (TMP/SMX) with rituximab, while the remainder did not. Differences in 1-year PJP incidence between the groups were estimated using Cox proportional hazards regression. Risk-benefit assessment was performed in subgroups stratified according to risk factors based on the number needed to treat (NNT) to prevent 1 case of PJP and the number needed to harm (NNH) due to severe AEs. Inverse probability of treatment weighting was applied to minimize the confounding by indication.

RESULTS

During the 663.1 person-years, there were 11 PJP cases, with a mortality rate of 63.6%. Concomitant use of high-dose glucocorticoids (≥30 mg/day of prednisone or equivalent during 4 weeks after rituximab administration) was the most important risk factor. The PJP incidence (per 100 person-years) was 7.93 (95% confidence interval [95% CI] 2.91-17.25) in the subgroup receiving high-dose glucocorticoids compared with 0.40 (95% CI 0.01-2.25) in the subgroup without high-dose glucocorticoid use. Although prophylactic TMP/SMX significantly reduced the overall PJP incidence (HR 0.11 [95% CI 0.03-0.43]), the NNT to prevent 1 case of PJP (146) was higher than the NNH (86). In contrast, the NNT fell to 20 (95% CI 10.7-65.7) in patients receiving concomitant high-dose glucocorticoids.

CONCLUSION

The benefit associated with primary PJP prophylaxis outweighs the risk of severe AEs in patients with rheumatic diseases receiving rituximab and concomitant high-dose glucocorticoid treatment.

Trends in the Epidemiology of Pneumocystis Pneumonia in Immunocompromised Patients without HIV Infection

The increasing morbidity and mortality of life-threatening Pneumocystis pneumonia (PCP) in immunocompromised people poses a global concern, prompting the World Health Organization to list it as one of the 19 priority invasive fungal diseases, calling for increased research and public health action. In response to this initiative, we provide this review on the epidemiology of PCP in non-HIV patients with various immunodeficient conditions, including the use of immunosuppressive agents, cancer therapies, solid organ and stem cell transplantation, autoimmune and inflammatory diseases, inherited or primary immunodeficiencies, and COVID-19. Special attention is given to the molecular epidemiology of PCP outbreaks in solid organ transplant recipients; the risk of PCP associated with the increasing use of immunodepleting monoclonal antibodies and a wide range of genetic defects causing primary immunodeficiency; the trend of concurrent infection of PCP in COVID-19; the prevalence of colonization; and the rising evidence supporting de novo infection rather than reactivation of latent infection in the pathogenesis of PCP. Additionally, we provide a concise discussion of the varying effects of different immunodeficient conditions on distinct components of the immune system. The objective of this review is to increase awareness and knowledge of PCP in non-HIV patients, thereby improving the early identification and treatment of patients susceptible to PCP.

Integrated multi-omics analyses reveal the altered transcriptomic characteristics of pulmonary macrophages in immunocompromised hosts with Pneumocystis pneumonia

Introduction

With the extensive use of immunosuppressants, immunosuppression-associated pneumonitis including Pneumocystis jirovecii pneumonia (PCP) has received increasing attention. Though aberrant adaptive immunity has been considered as a key reason for opportunistic infections, the characteristics of innate immunity in these immunocompromised hosts remain unclear.

Methods

In this study, wild type C57BL/6 mice or dexamethasone-treated mice were injected with or without Pneumocystis. Bronchoalveolar lavage fluids (BALFs) were harvested for the multiplex cytokine and metabolomics analysis. The single-cell RNA sequencing (scRNA-seq) of indicated lung tissues or BALFs was performed to decipher the macrophages heterogeneity. Mice lung tissues were further analyzed via quantitative polymerase chain reaction (qPCR) or immunohistochemical staining.

Results

We found that the secretion of both pro-inflammatory cytokines and metabolites in the Pneumocystis-infected mice are impaired by glucocorticoids. By scRNA-seq, we identified seven subpopulations of macrophages in mice lung tissues. Among them, a group of Mmp12⁺ macrophages is enriched in the immunocompetent mice with Pneumocystis infection. Pseudotime trajectory showed that these Mmp12⁺ macrophages are differentiated from Ly6c⁺ classical monocytes, and highly express pro-inflammatory cytokines elevated in BALFs of Pneumocystis-infected mice. In vitro, we confirmed that dexamethasone impairs the expression of Lif, Il1b, Il6 and Tnf, as well as the fungal killing capacity of alveolar macrophage (AM)-like cells. Moreover, in patients with PCP, we found a group of macrophages resembled the aforementioned Mmp12⁺ macrophages, and these macrophages are inhibited in the patient receiving glucocorticoid treatment. Additionally, dexamethasone simultaneously impaired the functional integrity of resident AMs and downregulated the level of lysophosphatidylcholine, leading to the suppressed antifungal capacities.

Conclusion

We reported a group of Mmp12⁺ macrophages conferring protection during Pneumocystis infection, which can be dampened by glucocorticoids. This study provides multiple resources for understanding the heterogeneity and metabolic changes of innate immunity in immunocompromised hosts, and also suggests that the loss of Mmp12⁺ macrophages population contributes to the pathogenesis of immunosuppression-associated pneumonitis.

Metabolomic Profiling of Lungs from Mice Reveals the Variability of Metabolites in Pneumocystis Infection and the Metabolic Abnormalities in BAFF-R-Deficient Mice

Purpose

The incidence of Pneumocystis pneumonia (PCP) in patients without human immunodeficiency virus (HIV) has been increasing. In this study, we aimed to investigate the metabolic changes in Pneumocystis infection and the metabolic abnormalities in B-cell-activating factor receptor (BAFF-R)-deficient mice with Pneumocystis infection.

Methods

The important function of B cells during Pneumocystis infection is increasingly recognized. In this study, a Pneumocystis-infected mouse model was constructed in BAFF-R^-/- mice and wild-type (WT) mice. Lungs of uninfected WT C57BL/6, WT Pneumocystis-infected, and BAFF-R^-/- Pneumocystis-infected mice were used for metabolomic analyses to compare the metabolomic profiles among the groups, with the aim of exploring the metabolic influence of Pneumocystis infection and the influence of mature B-cell deficiency during infection.

Results

The results indicated that many metabolites, mainly lipids and lipid-like molecules, were dysregulated in Pneumocystis-infected WT mice compared with uninfected WT C57BL/6 mice. The data also demonstrated significant changes in tryptophan metabolism, and the expression levels of key enzymes of tryptophan metabolism, such as indoleamine 2,3-dioxygenase 1 (IDO1), were significantly upregulated. In addition, B-cell development and function might be associated with lipid metabolism. We found a lower level of alitretinoin and the abnormalities of fatty acid metabolism in BAFF-R^-/- Pneumocystis-infected mice. The mRNA levels of enzymes associated with fatty acid metabolism in the lung were upregulated in BAFF-R^-/- Pneumocystis-infected mice and positively correlated with the level of IL17A, thus suggesting that the abnormalities of fatty acid metabolism may be associated with greater inflammatory cell infiltration in the lung tissue of BAFF-R^-/- Pneumocystis-infected mice compared with the WT Pneumocystis-infected mice.

Conclusion

Our data revealed the variability of metabolites in Pneumocystis-infected mice, suggesting that the metabolism plays a vital role in the immune response to Pneumocystis infection.

Single-cell RNA sequencing of subcutaneous adipose tissues identifies therapeutic targets for cancer-associated lymphedema

Cancer-associated lymphedema frequently occurs following lymph node resection for cancer treatment. However, we still lack effective targeted medical therapies for the treatment or prevention of this complication. An in-depth elucidation of the cellular alterations in subcutaneous adipose tissues of lymphedema is essential for medical development. We performed single-cell RNA sequencing of 70,209 cells of the stromal vascular fraction of adipose tissues from lymphedema patients and healthy donors. Four subpopulations of adipose-derived stromal cells (ASCs) were identified. Among them, the PRG4⁺/CLEC3B⁺ ASC subpopulation c3 was significantly expanded in lymphedema and related to adipose tissue fibrosis. Knockdown of CLEC3B in vitro could significantly attenuate the fibrogenesis of ASCs from patients. Adipose tissues of lymphedema displayed a striking depletion of LYVE⁺ anti-inflammatory macrophages and exhibited a pro-inflammatory microenvironment. Pharmacological blockage of Trem1, an immune receptor predominantly expressed by the pro-inflammatory macrophages, using murine LR12, a dodecapeptide, could significantly alleviate lymphedema in a mouse tail model. Cell–cell communication analysis uncovered a perivascular ligand-receptor interaction module among ASCs, macrophages, and vascular endothelial cells. We provided a comprehensive analysis of the lineage–specific changes in the adipose tissues from lymphedema patients at a single-cell resolution. CLEC3B was found to be a potential target for alleviating adipose tissue fibrosis. Pharmacological blockage of TREM1 using LR12 could serve as a promising medical therapy for treating lymphedema.

Single-cell RNA sequencing identifies an Il1rn+/Trem1+ macrophage subpopulation as a cellular target for mitigating the progression of thoracic aortic aneurysm and dissection

Thoracic aortic aneurysm and dissection (TAAD) is a life-threatening condition characterized by medial layer degeneration of the thoracic aorta. A thorough understanding of the regulator changes during pathogenesis is essential for medical therapy development. To delineate the cellular and molecular changes during the development of TAAD, we performed single-cell RNA sequencing of thoracic aortic cells from β-aminopropionitrile-induced TAAD mouse models at three time points that spanned from the early to the advanced stages of the disease. Comparative analyses were performed to delineate the temporal dynamics of changes in cellular composition, lineage-specific regulation, and cell–cell communications. Excessive activation of stress-responsive and Toll-like receptor signaling pathways contributed to the smooth muscle cell senescence at the early stage. Three subpopulations of aortic macrophages were identified, i.e., Lyve1⁺ resident-like, Cd74^high antigen-presenting, and Il1rn⁺/Trem1⁺ pro-inflammatory macrophages. In both mice and humans, the pro-inflammatory macrophage subpopulation was found to represent the predominant source of most detrimental molecules. Suppression of macrophage accumulation in the aorta with Ki20227 could significantly decrease the incidence of TAAD and aortic rupture in mice. Targeting the Il1rn⁺/Trem1⁺ macrophage subpopulation via blockade of Trem1 using mLR12 could significantly decrease the aortic rupture rate in mice. We present the first comprehensive analysis of the cellular and molecular changes during the development of TAAD at single-cell resolution. Our results highlight the importance of anti-inflammation therapy in TAAD, and pinpoint the macrophage subpopulation as the predominant source of detrimental molecules for TAAD. Targeting the IL1RN⁺/TREM1⁺ macrophage subpopulation via blockade of TREM1 may represent a promising medical treatment.

Primary prophylaxis for Pneumocystis jirovecii pneumonia in patients receiving rituximab

BACKGROUND

Although previous studies suggested that rituximab increases the risk of Pneumocystis jirovecii pneumonia (PJP), it is uncertain whether its primary prophylaxis for PJP is justified.

RESEARCH QUESTION

Does the benefit of primary prophylaxis for PJP in patients receiving rituximab treatment outweigh the potential risk of the prophylaxis?

STUDY DESIGN AND METHODS

This retrospective study included 3524 patients (hematologic diseases=2500; rheumatic diseases=559; pre/post-solid organ transplantation=465) first exposed to rituximab between 2002 and 2018 in a tertiary referral center in South Korea. Patients were classified into a control group (n=2523) and a prophylaxis group (n=1001) according to the administration of prophylactic TMP-SMX during the first 28 days after the start of rituximab (intention-to-treat analysis). In addition, exposure to TMP-SMX was examined as a time-varying variable (time-varying analysis). Primary outcome was the prophylactic effect of TMP-SMX on the 1-year incidence of PJP. Inverse probability of treatment weights was applied to minimize the baseline imbalance. Secondary outcome included the incidence of adverse drug reactions (ADRs) related to TMP-SMX.

RESULTS

Over 2759.9 person-years, 92 PJP infections occurred, with a mortality rate of 27.2%. The prophylaxis group showed a significantly lower incidence of PJP (adjusted sub-distribution hazard ratio (aSHR), 0.20 [95% CI, 0.10-0.42]) than the control group. This result was consistent with the results of time-varying analysis, in which only one PJP infection occurred during TMP-SMX administration (aSHR, 0.01 [0.003-0.16]). The incidence of adverse drug reactions (ADRs) related to TMP-SMX was 18.1 (14.6-22.2)/100 person-years, and most were of mild-to-moderate severity. Based on ten severe ADRs, the number needed to harm was 101 (61.9-261.1), whereas the number needed to prevent one PJP infection was 32 (24.8-39.4).

INTERPRETATION

TMP-SMX prophylaxis significantly reduces PJP incidence with a tolerable safety profile in patients receiving rituximab treatment.

New Insights into Blood Circulating Lymphocytes in Human Pneumocystis Pneumonia

The host lymphocyte response is decisive in Pneumocystis pneumonia (PCP) pathophysiology but little is known of the specific roles of lymphocyte subpopulations in this fungal infection. Peripheral NK, NKT, B, TCD4+ and TCD8+ subpopulations were compared by immunophenotyping between 20 patients diagnosed with PCP (PCP(+)] and 20 uninfected immunosuppressed patients (PCP(−)). Among PCP(+) subjects, the lymphocyte populations were also compared between surviving and deceased patients. Low B cell count (<40 cells/µL) was more frequent in PCP(+) than in PCP(−) patients (p = 0.03), while there was no difference for the TCD4 count. Among the PCP(+) group, the 7 deceased patients had lower Th1 (p = 0.02) and Tc1 (p = 0.03) populations, higher Th2 response (p = 0.03), higher effector TCD8 (p < 0.01), lower central memory TCD8 (p = 0.04) and reduced NK cells (p = 0.02) compared with the 13 survivors. Th1/Th2 ratio < 17, CD8 Tc1 < 44%, effector TCD8 < 25%, central memory TCD8 < 4%, NK cells < 50 cells/µL and total lymphocytes < 0.75 G/L were associated with a higher risk of mortality (p = 0.003, p = 0.007, p = 0.0007, p = 0.004, p = 0.02 and p = 0.019, respectively). The traditional analysis of TCD4 and TCD8 populations may be insufficient in the context of PCP. It could be completed by using B cells to predict the risk of PCP, and by using lymphocyte subpopulations or total lymphocyte count, which are easy to obtain in all health care facilities, to evaluate PCP prognosis.

Signatures of B Cell Receptor Repertoire Following Pneumocystis Infection

B cells play vital roles in host defense against Pneumocystis infection. However, the features of the B cell receptor (BCR) repertoire in disease progression remain unclear. Here, we integrated single-cell RNA sequencing and single-cell BCR sequencing of immune cells from mouse lungs in an uninfected state and 1–4 weeks post-infection in order to illustrate the dynamic nature of B cell responses during Pneumocystis infection. We identified continuously increased plasma cells and an elevated ratio of (IgA + IgG) to (IgD + IgM) after infection. Moreover, Pneumocystis infection was associated with an increasing naïve B subset characterized by elevated expression of the transcription factor ATF3. The proportion of clonal expanded cells progressively increased, while BCR diversity decreased. Plasma cells exhibited higher levels of somatic hypermutation than naïve B cells. Biased usage of V(D)J genes was observed, and the usage frequency of IGHV9-3 rose. Overall, these results present a detailed atlas of B cell transcriptional changes and BCR repertoire features in the context of Pneumocystis infection, which provides valuable information for finding diagnostic biomarkers and developing potential immunotherapeutic targets.

Pneumocystis jirovecii Pneumonia in Patients with Nephrotic Syndrome: Application of Lymphocyte Subset Analysis in Predicting Clinical Outcomes

Purpose

With immunosuppressants being widely used, Pneumocystis jirovecii pneumonia (PCP) has been increasing and could be life-threatening among HIV-negative patients. This study aimed at identifying prognostic factors of PCP in patients with nephrotic syndrome.

Methods

We retrospectively investigated patients with nephrotic syndrome who were diagnosed with PCP. The diagnosis of PCP was based on clinical manifestations, radiological findings, and microbiological confirmatory tests. Predictors of outcome were determined with multivariate logistic regression analysis.

Results

A total of 57 patients were included in this study. The PCP mortality was 33.3%, which increased to 48.6% if ICU admission was required and to 60% when mechanical ventilation was needed. The T lymphocyte count and CD4/CD8 ratio independently predicted the outcome of PCP, so did the CD4⁺ T lymphocyte count (OR, 0.981; 95% CI, 0.967–0.996; p=0.001). The cut-off value of 71 cells/μl for the CD4⁺ T lymphocyte count was determined to identify patients with poor prognosis. No association was found between PCP mortality and the type of immunosuppressant used.

Conclusions

PCP is a fatal complication among nephrotic syndrome patients receiving immunosuppressive therapy. The CD4⁺ T lymphocyte count is suggested as an independent predictor of prognosis, which can be used clinically to identify patients with high risk of unfavorable outcomes.

IL-17 Inversely Correlated with IL-10 via the STAT3 Gene in Pneumocystis-Infected Mice

Background

Pneumocystis pneumonia (PCP) remains a common opportunistic infection in immunosuppressed individuals. Current studies showed that multiple immune cells and cytokines took part in the host defense against Pneumocystis (PC). However, the roles of IL-17 and IL-10 in the development of PCP have not been elucidated.

Methods

IL-10 and IL-17 levels in serum from PCP mice were detected via ELISA. The percentages of B10 cells, IL-10⁺ macrophages, and IL-10⁺ T cells in the lung from IL-17^–/– PCP mice and Th17 cells and IL-17⁺γδT cells in IL-10^–/– PCP mice were examined via flow cytometry. Also, antibody neutralization examination was also performed to elucidate the relationship of IL-17 and IL-10 in the PCP model.

Results

We noted the increase of IL-17 and IL-10 levels in serum from mice infected with Pneumocystis. Furthermore, deficiency of IL-17 or IL-10 could lead to the delayed clearance of Pneumocystis and more severed lung damage. Our data also demonstrated that IL-17 deficiency enhanced the serum IL-10 level and the percentages of B10 cells, IL-10⁺ macrophages, and IL-10⁺ T cells in the lung from PCP mice. Interestingly, we also noted an increase of the IL-17 level in serum and Th17 cell and IL-17⁺γδT cell percentages in the lung from IL-10^–/– PCP mice. Using antibody neutralization experiments, we found that the STAT3 gene might play a critical role in the interplay of IL-17 and IL-10 in PCP.

Conclusion

Taken together, our results demonstrated that IL-17 and IL-10 could play the protective roles in the progression of PCP and the inverse correlation of them might be mediated by STAT3.

Niflumic Acid Reverses Airway Mucus Excess and Improves Survival in the Rat Model of Steroid-Induced Pneumocystis Pneumonia

Although the role of adaptive immunity in fighting Pneumocystis infection is well known, the role of the innate, airway epithelium, responses remains largely unexplored. The concerted interaction of innate and adaptive responses is essential to successfully eradicate infection. Increased expression of goblet-cell-derived CLCA1 protein plus excess mucus in infant autopsy lungs and in murine models of primary Pneumocystis infection alert of innate immune system immunopathology associated to Pneumocystis infection. Nonetheless, whether blocking mucus-associated innate immune pathways decreases Pneumocystis-related immunopathology is unknown. Furthermore, current treatment of Pneumocystis pneumonia (PcP) relying on anti-Pneumocystis drugs plus steroids is not ideal because removes cellular immune responses against the fungal pathogen. In this study, we used the steroid-induced rat model of PcP to evaluate inflammation and mucus progression, and tested the effect of niflumic acid (NFA), a fenamate-type drug with potent CLCA1 blocker activity, in decreasing Pneumocystis-associated immunopathology. In this model, animals acquire Pneumocystis spontaneously and pneumonia develops owing to the steroids-induced immunodeficiency. Steroids led to decreased animal weight evidencing severe immunosuppression and to significant Pneumocystis-associated pulmonary edema as evidenced by wet-to-dry lung ratios that doubled those of uninfected animals. Inflammatory cuffing infiltrates were noticed first around lung blood vessels followed by bronchi, and both increased progressively. Similarly, airway epithelial and lumen mucus progressively increased. This occurred in parallel to increasing levels of MUC5AC and mCLCA3, the murine homolog of hCLCA1. Administration of NFA caused a significant decrease in total mucus, MUC5AC and mCLCA3 and also, in Pneumocystis-associated inflammation. Most relevant, NFA treatment improved survival at 8 weeks of steroids. Results suggest an important role of innate immune responses in immunopathology of steroid-induced PcP. They warrant evaluation of CLCA1 blockers as adjunctive therapy in this condition and describe a simple model to evaluate therapeutic interventions for steroid resistant mucus, a common condition in patients with chronic lung disease like asthma, chronic obstructive pulmonary disease (COPD) and cystic fibrosis.

IL-10-producing B cells regulate Th1/Th17-cell immune responses in Pneumocystis pneumonia

Pneumocystis pneumonia (PCP) is a common opportunistic infectious disease that is prevalent in immunosuppressed hosts. Accumulating evidence shows that B cells play an important role in infectious diseases. In the present study, the immune regulatory role of mature B cells in host defense to Pneumocystis was evaluated. Pneumocystis infection resulted in a decrease in B cells in patients and mice, and the Pneumocystis burden in B cell-deficient mice also progressively increased from weeks 1 to 7 after infection. The clearance of Pneumocystis was delayed in B cell-activating factor receptor (BAFF-R)-deficient mice (BAFF-R^-/- mice), which had few B cells and Pneumocystis-specific IgG and IgM antibodies, compared with clearance in wild-type (WT) mice. There were fewer effector CD4⁺ T cells and higher percentages of T helper (Th)1/Th17 cells in BAFF-R^-/- mice than in WT mice. Adoptive transfer of naive B cells, mRNA sequencing, and IL-1β neutralization experiments indicated that IL-1β is a likely determinant of the IL-10-producing B cell-mediated suppression of Th1/Th17-cell immune responses in BAFF-R^-/- PCP mice. Our data indicated that B cells play a vital role in the regulation of Th cells in response to Pneumocystis infection.

IL-9 Deficiency Promotes Pulmonary Th17 Response in Murine Model of Pneumocystis Infection

Introduction

Pneumocystis pneumonia (PCP) remains a severe complication with high mortality in immunocompromised patients. It has been well accepted that CD4⁺ T cells play a major role in controlling Pneumocystis infection. Th9 cells were the main source of IL-9 with multifaced roles depending on specific diseases. It is unclear whether IL-9/Th9 contributes to the immune response against PCP. The current study aims to explore the role of IL-9 and the effect of IL-9 on Th17 cells in murine model of PCP.

Materials and methods

Mice were intratracheally injected with 1 × 10⁶Pneumocystis organisms to establish the murine model of Pneumocystis infection. Pneumocystis burden was detected by TaqMan real-time PCR. Using IL-9-deficient (IL-9^−/−) mice, flow cytometry, real-time PCR and enzyme-linked immunosorbent assay (ELISA) were conducted to investigate the immune function related to Th17 response in defense against Pneumocystis infection.

Results

Reduced Pneumocystis burden was observed in lungs in IL-9^−/− mice compared with WT mice at 3-week postinfection. IL-9^−/−mice exhibited stronger Th17 immune responses than WT PCP mice through flow cytometer and real-time PCR. ELISA revealed higher levels of IL-17 and IL-23 in bronchoalveolar lavage fluid from IL-9^−/− mice than WT mice. And IL-9 deficiency promoted Th17 differentiation from CD4⁺ naive T cells. IL-17A neutralization increased Pneumocystis burden in IL-9^−/− mice.

Conclusion

Although similar basic clearance of Pneumocystis organisms was achieved in both WT and IL-9^−/− PCP mice, IL-9 deficiency could lower Pneumocystis organism burden and promote pulmonary Th17 cells response in the early stage of infection.

The lung microbiome in patients with pneumocystosis

Backround

Pneumocystis jirovecii pneumonia (PCP) is an opportunistic fungal infection that is associated with a high morbidity and mortality in immunocompromised individuals. In this study, we analysed the microbiome of the lower respiratory tract from critically ill intensive care unit patients with and without pneumocystosis.

Methods

Broncho-alveolar fluids from 65 intubated and mechanically ventilated intensive care unit patients (34 PCP+ and 31 PCP- patients) were collected. Sequence analysis of bacterial 16S rRNA gene V3/V4 regions was performed to study the composition of the respiratory microbiome using the Illumina MiSeq platform.

Results

Differences in the microbial composition detected between PCP+ and PCP- patients were not statistically significant on class, order, family and genus level. In addition, alpha and beta diversity metrics did not reveal significant differences between PCP+ and PCP- patients. The composition of the lung microbiota was highly variable between PCP+ patients and comparable in its variety with the microbiota composition of the heterogeneous collective of PCP- patients.

Conclusions

The lower respiratory tract microbiome in patients with pneumocystosis does not appear to be determined by a specific microbial composition or to be dominated by a single bacterial species.

Electronic supplementary material

The online version of this article (10.1186/s12890-017-0512-5) contains supplementary material, which is available to authorized users.