Pneumocystis murina promotes inflammasome formation and NETosis during Pneumocystis pneumonia

Pneumocystis jirovecii pneumonia (PjP) poses a serious risk to individuals with compromised immune systems, such as individuals with HIV/AIDS or undergoing immunosuppressive therapies for cancer or solid organ transplants. Severe PjP triggers excessive lung inflammation, resulting in lung function decline and consequential alveolar damage, potentially culminating in acute respiratory distress syndrome. Non-HIV patients face a 30%-60% mortality rate, emphasizing the need for a deeper understanding of inflammatory responses in PjP. Prior research emphasized macrophages in Pneumocystis infections, neglecting neutrophils' role in tissue damage. Consequently, the overemphasis on macrophages led to an incomplete understanding of the role of neutrophils and inflammatory responses. In the current investigation, our RNAseq studies on a murine surrogate model of PjP revealed heightened activation of the NLRP3 inflammasome and NETosis cell death pathways in their lungs. Immunofluorescence staining confirmed neutrophil extracellular trap (NET) presence in the lungs of the P. murina-infected mice, validating our findings. Moreover, isolated neutrophils exhibited NETosis when directly stimulated with P. murina. Isolated NETs compromised P. murina viability in vitro, highlighting the potential role of neutrophils in controlling fungal growth and promoting inflammation during P. murina pneumonia through NLRP3 inflammasome assembly and NETosis. These pathways, essential for inflammation and pathogen elimination, bear the risk of uncontrolled activation leading to excessive tissue damage and persistent inflammation. This pioneering study is the first to identify the formation of NETs and inflammasomes during Pneumocystis infection, paving the way for comprehensive investigations into treatments aimed at mitigating lung damage and augmenting survival rates for individuals with PjP.IMPORTANCEPneumocystis jirovecii pneumonia (PjP) affects individuals with weakened immunity, such as HIV/AIDS, cancer, and organ transplant patients. Severe PjP triggers lung inflammation, impairing function and potentially causing acute respiratory distress syndrome. Non-HIV individuals face a 30%-60% mortality rate, underscoring the need for deeper insight into PjP's inflammatory responses. Past research focused on macrophages in managing Pneumocystis infection and its inflammation, while the role of neutrophils was generally overlooked. In contrast, our findings in P. murina-infected mouse lungs showed neutrophil involvement during inflammation and increased expression of NLRP3 inflammasome and NETosis pathways. Detection of neutrophil extracellular traps further indicated their involvement in the inflammatory process. Although beneficial in combating infection, unregulated neutrophil activation poses a potential threat to lung tissues. Understanding the behavior of neutrophils in Pneumocystis infections is crucial for controlling detrimental reactions and formulating treatments to reduce lung damage, ultimately improving the survival rates of individuals with PjP.

Comparative efficacy and safety of Pneumocystis jirovecii pneumonia prophylaxis regimens for people living with HIV: a systematic review and network meta-analysis of randomized controlled trials

BACKGROUND

Pneumocystis jirovecii pneumonia (PCP) is a common opportunistic infection among people living with HIV (PWH), particularly among new and untreated cases. Several regimens are available for the prophylaxis of PCP, including trimethoprim-sulfamethoxazole (TMP-SMX), dapsone-based regimens (DBRs), aerosolized pentamidine (AP), and atovaquone.

OBJECTIVES

To compare the efficacy and safety of PCP prophylaxis regimens in PWH by network meta-analysis.

METHODS

DATA SOURCES: Embase, MEDLINE, and CENTRAL from inception to June 21, 2023.

STUDY ELIGIBILITY CRITERIA

Comparative randomized controlled trials (RCTs).

PARTICIPANTS

PWH.

INTERVENTIONS

Regimens for PCP prophylaxis either compared head-to-head or versus no treatment/placebo.

ASSESSMENT OF RISK OF BIAS

Cochrane risk-of-bias tool for RCTs 2.

METHODS OF DATA SYNTHESIS

Title or abstract and full-text screening and data extraction were performed in duplicate by two independent reviewers. Data on PCP incidence, all-cause mortality, and discontinuation due to toxicity were pooled and ranked by network meta-analysis. Subgroup analyses of primary versus secondary prophylaxis, by year, and by dosage were performed.

RESULTS

A total of 26 RCTs, comprising 55 treatment arms involving 7516 PWH were included. For the prevention of PCP, TMP-SMX was ranked the most favourable agent and was superior to DBRs (risk ratio [RR] = 0.54; 95% CI, 0.36-0.83) and AP (RR = 0.53; 95% CI, 0.36-0.77). TMP-SMX was also the only agent with a mortality benefit compared with no treatment/placebo (RR = 0.79; 95% CI, 0.64-0.98). However, TMP-SMX was also ranked as the most toxic agent with a greater risk of discontinuation than DBRs (RR = 1.25; 95% CI, 1.01-1.54) and AP (7.20; 95% CI, 5.37-9.66). No significant differences in PCP prevention or mortality were detected among the other regimens. The findings remained consistent within subgroups.

CONCLUSIONS

TMP-SMX is the most effective agent for PCP prophylaxis in PWH and the only agent to confer a mortality benefit; consequently, it should continue to be recommended as the first-line agent. Further studies are necessary to determine the optimal dosing of TMP-SMX to maximize efficacy and minimize toxicity.

Retracing the evolution of Pneumocystis species, with a focus on the human pathogen Pneumocystis jirovecii

SUMMARYEvery human being is presumed to be infected by the fungus Pneumocystis jirovecii at least once in his or her lifetime. This fungus belongs to a large group of species that appear to exclusively infect mammals, with P. jirovecii being the only one known to cause disease in humans. The mystery of P. jirovecii origin and speciation is just beginning to unravel. Here, we provide a review of the major steps of P. jirovecii evolution. The Pneumocystis genus likely originated from soil or plant-associated organisms during the period of Cretaceous ~165 million years ago and successfully shifted to mammals. The transition coincided with a substantial loss of genes, many of which are related to the synthesis of nutrients that can be scavenged from hosts or cell wall components that could be targeted by the mammalian immune system. Following the transition, the Pneumocystis genus cospeciated with mammals. Each species specialized at infecting its own host. Host specialization is presumably built at least partially upon surface glycoproteins, whose protogene was acquired prior to the genus formation. P. jirovecii appeared at ~65 million years ago, overlapping with the emergence of the first primates. P. jirovecii and its sister species P. macacae, which infects macaques nowadays, may have had overlapping host ranges in the distant past. Clues from molecular clocks suggest that P. jirovecii did not cospeciate with humans. Molecular evidence suggests that Pneumocystis speciation involved chromosomal rearrangements and the mounting of genetic barriers that inhibit gene flow among species.

Metabolic modulation: Pneumocystis phosphoglucomutase is a target influencing host recognition

Herein, this manuscript explores the significance of the phosphoglucomutase (PGM) enzyme in Pneumocystis spp., focusing on its role in fungal surface mannoprotein formation. Through expression of the Pneumocystis murina Pmpgm2 in a Saccharomyces cerevisiae pgm2Δ strain, we demonstrate restoration of binding to the mannose receptor (MR) and macrophages to wildtype yeast levels in this complemented strain. Gas Chromatography-Mass Spectroscopy (GC-MS) confirmed reduced mannose content in the pgm2Δ yeast strain compared to the wild-type and complemented Pmpgm2 cDNA-expressing strains. This study underscores fungal PGM function in dolichol glucosyl phosphate biosynthesis, crucial for proper cell wall mannoprotein formation. Furthermore, highlighting the conservation of targetable cysteine residues across fungal pathogens, PGM inhibition maybe a potential therapeutic strategy against a broad spectrum of fungal infections.

The incidence and prevalence of serious fungal diseases in Tunisia

With increasing concern about the negative health impact of fungal disease, there is a need to survey what is and is not known about the epidemiology of these infections in Tunisia. We have estimated the incidence and prevalence of the most serious fungal diseases in Tunisia for the first time. Using published literature from Tunisia, or if absent other countries, we have estimated the burden of life-threatening fungal infections and those causing significant morbidity, using deterministic modeling, based on populations at greatest risk. An estimated 250,494 (2.12% of the Tunisian population) are affected by a serious fungal disease annually. Invasive and chronic pulmonary aspergillosis are relatively common with 708 and 2090 patients affected, partly linked to the prevalence of chronic obstructive pulmonary disease (COPD). Fungal asthma (allergic bronchopulmonary aspergillosis and severe asthma with fungal sensitization) have an estimated prevalence of 38,264 (5.8% of the adult asthma population). Fungal keratitis probably affects 1,761 eyes annually, often leading to uniocular blindness. Candidaemia and Candida peritonitis probably affect at least 680 people annually, with a high mortality. Recurrent vulvovaginal candidiasis probably affects over 200,000 women. While fungal diseases are regularly diagnosed in Tunisia, epidemiological studies with denominators are uncommon. Some fungal diseases are poorly addressed with the current diagnostic portfolio, and surveillance is lacking. Studies on these diseases and the implementation of a national program of surveillance are required.

Pneumocystis jirovecii Pneumonia in HIV-Negative, Non-transplant Patients: Epidemiology, Clinical Manifestations, Diagnosis, Treatment, and Prevention

Purpose of Review

Pneumocystis jirovecii pneumonia (PJP) is an opportunistic fungal infection that is increasingly seen in HIV-negative patients with immune compromise due to other etiologies. We lack comprehensive clinical recommendations for this population.

Recent Findings

In non-HIV cases, PJP has a mortality rate of up to 50%, which is unacceptable despite the presence of safe and effective prophylaxis and therapy. Steroid use is one of the most common risk factors for disease development. New data suggests that lower doses of the preferred treatment regimen, TMP-SMX, may be equally effective for treatment while limiting side effects. While commonly used, the benefit of corticosteroids for the treatment of PJP has recently been called into question, with a recent multicenter cohort demonstrating no benefit among solid organ transplant recipients.

Summary

A high suspicion of PJP in individuals with pneumonia during immunosuppressant use is crucial. Therapeutic options are evolving to decrease potential side effects while maintaining efficacy in this highly morbid disease.

Pneumocystis murina lesions in lungs of experimentally infected Cd40l-/- mice

The Cd40l-/- mouse is a well-established model of X-linked hyper-immunoglobulin M (IgM) syndrome, an immunodeficiency disorder of human beings characterized by the lack of expression of the CD40 ligand (CD40L) on activated T-cells, predisposing to infections with opportunistic pathogens like Pneumocystis jirovecii. The aim of our study was to describe the pulmonary lesions in Cd40l-/- mice experimentally infected with Pneumocystis murina, in comparison with naturally infected severe combined immunodeficient (SCID) mice. Formalin-fixed paraffin-embedded lungs from 26 Cd40l-/-, 11 SCID, and 5 uninfected Cd40l-/- mice were examined by histology and immunohistochemistry for the presence of the pathogen and for leukocyte populations (CD3, CD4, CD45R/B220, CD8a, Iba-1, Ly-6G, CD206, MHC II, and NKp46/NCR1). Infection was confirmed by immunohistochemistry in 18/26 (69%) Cd40l-/- mice and in 11/11 (100%) SCID mice. Fourteen out of 26 (54%) Cd40l-/- mice had interstitial pneumonia. Twenty-three out of 26 (88%) Cd40l-/- mice had peribronchiolar/perivascular lymphoplasmacytic infiltrates, rich in B-cells and Mott cells. Acidophilic macrophage pneumonia was additionally found in 20/26 (77%) Cd40l-/- mice. Only 4/11 (36%) SCID mice had interstitial pneumonia, but no peribronchiolar/perivascular infiltrates or acidophilic macrophage pneumonia were observed in this strain. This study represents the first description of pulmonary histopathological lesions in Cd40l-/- mice infected with P. murina. We speculate that the singular characteristics of the inflammatory infiltrates observed in Cd40l-/- mice could be explained by the specific immune phenotype of the model.

Development of Highly Efficient Universal Pneumocystis Primers and Their Application in Investigating the Prevalence and Genetic Diversity of Pneumocystis in Wild Hares and Rabbits

Despite its ubiquitous infectivity to mammals with strong host specificity, our current knowledge about Pneumocystis has originated from studies of merely 4% of extant mammalian species. Further studies of Pneumocystis epidemiology across a broader range of animal species require the use of assays with high sensitivity and specificity. To this end, we have developed multiple universal Pneumocystis primers targeting different genetic loci with high amplification efficiency. Application of these primers to PCR investigation of Pneumocystis in free-living hares (Lepus townsendii, n = 130) and rabbits (Oryctolagus cuniculus, n = 8) in Canada revealed a prevalence of 81% (105/130) and 25% (2/8), respectively. Genotyping analysis identified five and two variants of Pneumocystis from hares and rabbits, respectively, with significant sequence divergence between the variants from hares. Based on phylogenetic analysis using nearly full-length sequences of the mitochondrial genome, nuclear rRNA operon and dihydropteroate synthase gene for the two most common variants, Pneumocystis in hares and rabbits are more closely related to each other than either are to Pneumocystis in other mammals. Furthermore, Pneumocystis in both hares and rabbits are more closely related to Pneumocystis in primates and dogs than to Pneumocystis in rodents. The high prevalence of Pneumocystis in hares (P. sp. 'townsendii') suggests its widespread transmissibility in the natural environment, similar to P. oryctolagi in rabbits. The presence of multiple distinct Pneumocystis populations in hares contrasts with the lack of apparent intra-species heterogeneity in P. oryctolagi, implying a unique evolution history of P. sp. 'townsendii' in hares.

Insights into copper sensing and tolerance in Pneumocystis species

Introduction

Pneumocystis species are pathogenic fungi known to cause pneumonia in immunocompromised mammals. They are obligate to their host, replicate extracellularly in lung alveoli and thrive in the copper-enriched environment of mammalian lungs. In this study, we investigated the proteome of Pneumocystis murina, a model organism that infects mice, in the context of its copper sensing and tolerance.

Methods and results

The query for copper-associated annotations in FungiDB followed by a manual curation identified only 21 genes in P. murina, significantly fewer compared to other clinically relevant fungal pathogens or phylogenetically similar free-living fungi. We then employed instrumental analyses, including Size-Exclusion Chromatography Inductively Coupled Plasma Mass Spectrometry (SEC-ICP-MS), Immobilized Metal Affinity Chromatography (IMAC), and Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS), to isolate and identify copper-binding proteins from freshly extracted organisms, revealing 29 distinct cuproproteins. The RNA sequencing (RNA-seq) analysis of P. murina exposed to various CuSO4 concentrations at three temporal intervals (0.5, 2, and 5 h) indicated that significant gene expression changes occurred only under the highest CuSO4 concentration probed (100 μM) and the longest exposure duration (5 h). This stimulus led to the upregulation of 43 genes and downregulation of 27 genes compared to untreated controls. Quantitative PCR (qPCR) confirmed the expression of four out of eight selected upregulated genes, including three assumed transcription factors (PNEG_01236, PNEG_01675, and PNEG_01730) and a putative copper transporter (PNEG_02609). Notably, the three applied methodologies - homology-based annotation, SEC-ICP-MS/IMAC/LC-MS/MS, and RNA-seq - yielded largely distinct findings, with only four genes (PNEG_02587, PNEG_03319, PNEG_02584, and PNEG_02989) identified by both instrumental methods.

Discussion

The insights contribute to the broader knowledge of Pneumocystis copper homeostasis and provide novel facets of host-pathogen interactions for extracellular pathogens. We suggest that future studies of Pneumocystis pathogenicity and copper stress survival should consider the entire spectrum of identified genes.

Nebulised pentamidine prophylaxis of pneumocystis pneumonia in adults accessing HIV services at royal free hospital, London

Receipt of nebulised pentamidine in people with HIV was audited to identify if individuals were appropriately receiving nebulised pentamidine, and whether national guidelines were being followed when prophylaxis was commenced and discontinued. Of 76 people with who received nebulised pentamidine, the main indication for starting nebulised pentamidine was a co-trimoxazole adverse drug reaction. Co-trimoxazole desensitization was not attempted before starting nebulised pentamidine. The main indication for stopping nebulised pentamidine prophylaxis was when immune reconstitution occurred. This single centre audit revealed that national guidelines were being followed in most cases. The lack of information regarding the reason for starting or stopping nebulised pentamidine prophylaxis, or detail of the clinician's concerns about potential poor adherence with oral regimens of prophylaxis as a reason for choosing nebulised pentamidine prophylaxis, identifies a need for improved documentation of clinicians' decision-making. Introduction of pharmacist-led interventions/alerts using patients' electronic records, similar to those used in primary care, would enable the specialist pharmacy team to identify when and if co-trimoxazole desensitization has been offered and discussed/declined before a clinician prescribes nebulised pentamidine as well as enabling identification of those in who pentamidine prophylaxis has been continued, despite "immune reconstitution".

Evaluation of analyte-specific reagents for the direct detection of Pneumocystis jirovecii

Pneumocystis jirovecii pneumonia (PJP) is a serious and sometimes fatal infection occurring in immunocompromised individuals. High-risk patients include those with low CD4 counts due to human immunodeficiency virus infection and transplant recipients. The incidence of PJP is increasing, and rapid detection of PJP is needed to effectively target treatment and improve patient outcomes. A common method used is an immunofluorescent assay (IFA), which has limitations, including labor costs, low sensitivity, and requirement for expert interpretation. This study evaluates the performance of the DiaSorin Molecular Pneumocystis jirovecii analyte-specific reagent (ASR) in a laboratory-developed test (LDT) for the direct detection of P. jirovecii DNA without prior nucleic acid extraction. Respiratory samples (n = 135) previously tested by IFA from 111 patients were included. Using a composite standard of in-house IFA and reference lab PJP PCR, the percent positive agreement for the LDT using the DiaSorin ASR was 97.8% (90/92). The negative percent agreement was 97.7% (42/43). The lower limit of detection of the assay was determined to be 1,200 copies/mL in bronchoalveolar lavage fluid. Analytical specificity was assessed using cultures of oropharyngeal flora and common respiratory bacterial and fungal pathogens. No cross-reactivity was observed. Our study suggests that the DiaSorin Pneumocystis ASR accurately detects P. jirovecii DNA and demonstrates improved sensitivity compared to the IFA method.

IMPORTANCE

Our study is unique compared to other previously published studies on the DiaSorin analyte-specific reagent (ASR) because we focused on microbiological diagnostic methods commonly used (immunofluorescent assay) as opposed to pathology findings or reference PCR. In addition, in our materials and methods, we describe the protocol for the use of the DiaSorin ASR as a singleplex assay, which will allow other users to evaluate the ASR for clinical use in their lab.

Slicing through the challenge of maintaining Pneumocystis in the laboratory

Pneumocystis jirovecii is a major fungal pathogen of humans that causes life-threatening lung infections in immunocompromised individuals. Despite its huge global impact upon human health, our understanding of the pathobiology of this deadly fungus remains extremely limited, largely because it is not yet possible to cultivate Pneumocystis in vitro, independently of the host. However, a recent paper by Munyonho et al. offers a major step forward (F. T. Munyonho, R. D. Clark, D. Lin, M. S. Khatun, et al., 2023, mBio 15:e01464-23, https://doi.org/10.1128/mbio.01464-23). They show that it is possible to maintain both the trophozoite and cyst forms of the mouse pathogen, Pneumocystis murina, in precision-cut lung slices for several weeks. Furthermore, they demonstrate that this offers the exciting opportunity to examine potential virulence factors such as possible biofilm formation as well as antifungal drug responses in the lung.

Characterization of the Pneumocystis jirovecii and Pneumocystis murina phosphoglucomutases (Pgm2s): a potential target for Pneumocystis therapy

Pneumocystis cyst life forms contain abundant β-glucan carbohydrates, synthesized using β-1,3 and β-1,6 glucan synthase enzymes and the donor uridine diphosphate (UDP)-glucose. In yeast, phosphoglucomutase (PGM) plays a crucial role in carbohydrate metabolism by interconverting glucose 1-phosphate and glucose 6-phosphate, a vital step in UDP pools for β-glucan cell wall formation. This pathway has not yet been defined in Pneumocystis. Herein, we surveyed the Pneumocystis jirovecii and Pneumocystis murina genomes, which predicted a homolog of the Saccharomyces cerevisiae major PGM enzyme. Furthermore, we show that PjPgm2p and PmPgm2p function similarly to the yeast counterpart. When both Pneumocystis pgm2 homologs are heterologously expressed in S. cerevisiae pgm2Δ cells, both genes can restore growth and sedimentation rates to wild-type levels. Additionally, we demonstrate that yeast pgm2Δ cell lysates expressing the two Pneumocystis pgm2 transcripts individually can restore PGM activities significantly altered in the yeast pgm2Δ strain. The addition of lithium, a competitive inhibitor of yeast PGM activity, significantly reduces PGM activity. Next, we tested the effects of lithium on P. murina viability ex vivo and found the compound displays significant anti-Pneumocystis activity. Finally, we demonstrate that a para-aryl derivative (ISFP10) with known inhibitory activity against the Aspergillus fumigatus PGM protein and exhibiting 50-fold selectivity over the human PGM enzyme homolog can also significantly reduce Pmpgm2 activity in vitro. Collectively, our data genetically and functionally validate phosphoglucomutases in both P. jirovecii and P. murina and suggest the potential of this protein as a selective therapeutic target for individuals with Pneumocystis pneumonia.

Estimated burden of fungal infections in Panama

Data published on Panamanian fungal disease are scarce, mostly case reports. To date, there is no paper that compiles the burden of fungal disease Here we estimate for the first time the incidence and prevalence of fungal diseases in Panama. Data on fungal disease were obtained from different search engines: PubMed, Google Scholar, Scielo and Lilacs. For population and at risk diseases, we used statistics from worldometer, UNAIDS, and WHO. Incidence, prevalence, and absolute numbers were calculated based on the population at risk. Panamanian population in 2022 was 4,429,739. We estimated that 85,530 (1.93 %) people suffer from fungal diseases. The most frequent fungal infection was recurrent Candida vaginitis (3285/100,000). There are 31,000 HIV-infected people in Panama and based on the number of cases not receiving anti-retroviral therapy (14,570), and previous reports of prevalence of opportunistic infections, we estimated annual incidences of 4.0/100,000 for cryptococcal meningitis, 29.5/100,000 for oral candidiasis, 23.1/100,000 for esophageal candidiasis, 29.5/100,000 for Pneumocystis pneumonia, 15.1/100,000, and for histoplasmosis. For chronic pulmonary aspergillosis (CPA) and fungal asthma we used data from Guatemala and Colombia to estimate COPD and asthma prevalence and WHO report for tuberculosis. We estimated annual incidences of 6.1/100,000 for invasive aspergillosis and prevalence of 31.5/100,000 for CPA, 60.2/100,000 for allergic bronchopulmonary aspergillosis, and 79.5/100,000 for severe asthma with fungal sensitisation. Other incidence estimates were 5.0/100,000 for candidaemia, 0.20/100,000 for mucormycosis, and 4.97/100,000 for fungal keratitis. Even though this report on burden of fungal disease is a forward step, more epidemiological studies to validate these estimates are needed.

Pneumocystis jirovecii pneumonia: a case report

INTRODUCTION AND IMPORTANCE

Pneumocystis jirovecii (PJP) pneumonia is a serious life-threatening condition in immunocompromised individuals and is often associated with human immunodeficiency virus (HIV) + patients. We describe a case of PJP pneumonia which provided a diagnostic challenge in a patient who presented with no known risk factors leading to a delay in initiation of appropriate antibiotic therapy.

CASE PRESENTATION

A 71-year-old previously healthy white/Caucasian male presented with subacute hypoxic respiratory failure due to multifocal pneumonia with diffuse bilateral ground glass opacities with consolidations despite prior treatment with antibiotics and steroids. He was admitted and started on intravenous broad-spectrum antibiotics but continued to deteriorate, eventually requiring intubation and transfer to the ICU. Bronchoscopy revealed PJP and treatment was initiated, but the patient developed refractory shock and multiorgan failure, and ultimately died. It was later discovered that he was HIV-1 positive.

CLINICAL DISCUSSION

PJP, as a potential cause of his presentation, was not considered given that our patient lacked any overt risk factors for PJP pneumonia. He continued to worsen despite broad spectrum antibiotic therapy and hence bronchoscopy was pursued. His clinical profile, in hindsight, was suspicious for PJP pneumonia and early PJP-directed antibiotic therapy may have prevented a fatal outcome, as in this case. There was an element of cognitive bias across multiple providers which may have contributed to the delay in treatment despite his rapid clinical decline while on conventional pneumonia treatment protocol. His diagnosis was later evident when his BAL-DFA grew PJP in addition to his low levels of CD4 and CD8 cells. He was found to be HIV-1 positive five days after his death; there was a delay in this diagnosis since all positive HIV tests from the hospital are reported as 'pending' until the presumptive positive sample goes to the Connecticut Department of Public Health State laboratory for the confirmatory test. PJP-targeted therapies were initiated later in our patient's hospital course when the infection had progressed to refractory septic shock with multiorgan failure and eventual death.

CONCLUSION

PJP pneumonia is a fatal disease if not recognized early in the course of illness, and the patient usually undergoes multiple antibiotic regimens before they are diagnosed and receive appropriate clinical care. The gold standard of diagnostic testing for PJP is by obtaining bronchial washings through a flexible bronchoscopy and the turnaround time for such results may take a few days to result. A significant proportion of patients may not have any overt risk factors of immunosuppression and early empiric treatment for PJP may be clinically appropriate as the delay in diagnosis may be associated with significant morbidity and mortality risk.

Targeting host tyrosine kinase receptor EphA2 signaling via small-molecule ALW-II-41-27 inhibits macrophage pro-inflammatory signaling responses to Pneumocystis carinii β-glucans

Pneumocystis jirovecii, the fungus that causes Pneumocystis jirovecii pneumonia (PJP), is a leading cause of morbidity and mortality in immunocompromised individuals. We have previously shown that lung epithelial cells can bind Pneumocystis spp. β-glucans via the EphA2 receptor, resulting in activation and release of proinflammatory cytokines. Herein, we show that in vivo Pneumocystis spp. β-glucans activation of the inflammatory signaling cascade in macrophages can be pharmacodynamically inhibited with the EphA2 receptor small-molecule inhibitor ALW-II-41-27. In vitro, when ALW-II-41-27 is administrated via intraperitoneal to mice prior to the administration of highly proinflammatory Saccharomyces cerevisiae β-glucans in the lung, a significant reduction in TNF-alpha release was noted in the ALW-II-41-27 pre-treated group. Taken together, our data suggest that targeting host lung macrophage activation via EphA2 receptor-fungal β-glucans interactions with ALW-II-41-27 or other EphA2 receptor kinase targeting inhibitors might be an attractive and viable strategy to reduce detrimental lung inflammation associated with PJP.

Extracellular vesicles from Pneumocystis carinii-infected rats impair fungal viability but are dispensable for macrophage functions

Pneumocystis spp. are host obligate fungal pathogens that can cause severe pneumonia in mammals and rely heavily on their host for essential nutrients. The lack of a sustainable in vitro culture system poses challenges in understanding their metabolism, and the acquisition of essential nutrients from host lungs remains unexplored. Transmission electron micrographs show that extracellular vesicles (EVs) are found near Pneumocystis spp. within the lung. We hypothesized that EVs transport essential nutrients to the fungi during infection. To investigate this, EVs from P. carinii- and P. murina-infected rodents were biochemically and functionally characterized. These EVs contained host proteins involved in cellular, metabolic, and immune processes as well as proteins with homologs found in other fungal EV proteomes, indicating that Pneumocystis may release EVs. Notably, EV uptake by P. carinii indicated their potential involvement in nutrient acquisition and a possibility for using engineered EVs for efficient therapeutic delivery. However, EVs added to P. carinii in vitro did not show increased growth or viability, implying that additional nutrients or factors are necessary to support their metabolic requirements. Exposure of macrophages to EVs increased proinflammatory cytokine levels but did not affect macrophages' ability to kill or phagocytose P. carinii. These findings provide vital insights into P. carinii and host EV interactions, yet the mechanisms underlying P. carinii's survival in the lung remain uncertain. These studies are the first to isolate, characterize, and functionally assess EVs from Pneumocystis-infected rodents, promising to enhance our understanding of host-pathogen dynamics and therapeutic potential.IMPORTANCEPneumocystis spp. are fungal pathogens that can cause severe pneumonia in mammals, relying heavily on the host for essential nutrients. The absence of an in vitro culture system poses challenges in understanding their metabolism, and the acquisition of vital nutrients from host lungs remains unexplored. Extracellular vesicles (EVs) are found near Pneumocystis spp., and it is hypothesized that these vesicles transport nutrients to the pathogenic fungi. Pneumocystis proteins within the EVs showed homology to other fungal EV proteomes, suggesting that Pneumocystis spp. release EVs. While EVs did not significantly enhance P. carinii growth in vitro, P. carinii displayed active uptake of these vesicles. Moreover, EVs induced proinflammatory cytokine production in macrophages without compromising their ability to combat P. carinii. These findings provide valuable insights into EV dynamics during host-pathogen interactions in Pneumocystis pneumonia. However, the precise underlying mechanisms remain uncertain. This research also raises the potential for engineered EVs in therapeutic applications.

Epidemiology, Clinical Characteristics, and Diagnostic Testing Practices for Pneumocystis Pneumonia-Associated Hospitalizations, United States, 2019-2022

Among 9196 hospitalizations involving Pneumocystis pneumonia, those without HIV had higher in-hospital mortality (24.3% vs 10.5%, P < .001) when compared with those with HIV. These findings underscore the continued importance of Pneumocystis pneumonia clinical awareness and the need for comprehensive prophylaxis guidance, particularly for certain patients without HIV who are immunosuppressed.

Analytical and clinical validation of multiplex droplet digital PCR assay for detecting pathogenic fungal infection in lungs

Pulmonary invasive fungal infection in immunocompromised hosts is difficult to diagnose, and current tools for diagnosis or monitoring of response to antifungal treatments have inherent limitations. Droplet digital PCR (ddPCR) has emerged as a promising tool for pulmonary pathogen detection with high sensitivity. This study presents a novel ddPCR panel for rapid and sensitive identification of pulmonary fungal pathogens. First, a ddPCR method for detecting three fungal genera, including Pneumocystis, Aspergillus, and Cryptococcus, was established and evaluated. Then, the clinical validation performance of ddPCR was compared with that of qPCR using 170 specimens, and the 6 specimens with inconsistent results were further verified by metagenomics next-generation sequencing, which yielded results consistent with the ddPCR findings. Finally, the area under the ROC curve (AUC) was used to evaluate the efficiency of ddPCR. While the qPCR identified 16 (9.41%) cases of Aspergillus and 6 (3.53%) cases of Pneumocystis, ddPCR detected 20 (11.76%) Aspergillus cases and 8 (4.71%) Pneumocystis cases. The AUC for Aspergillus, Cryptococcus, and Pneumocystis was 0.974, 0.998, and 0.975, respectively. These findings demonstrated that the ddPCR assay is a highly sensitive method for identifying pathogens responsible for invasive fungal pulmonary infections, and is a promising tool for early diagnosis.      .

Axenic Long-Term Cultivation of Pneumocystis jirovecii

Pneumocystis jirovecii, a fungus causing severe Pneumocystis pneumonia (PCP) in humans, has long been described as non-culturable. Only isolated short-term experiments with P. jirovecii and a small number of experiments involving animal-derived Pneumocystis species have been published to date. However, P. jirovecii culture conditions may differ significantly from those of animal-derived Pneumocystis, as there are major genotypic and phenotypic differences between them. Establishing a well-performing P. jirovecii cultivation is crucial to understanding PCP and its pathophysiological processes. The aim of this study, therefore, was to develop an axenic culture for Pneumocystis jirovecii. To identify promising approaches for cultivation, a literature survey encompassing animal-derived Pneumocystis cultures was carried out. The variables identified, such as incubation time, pH value, vitamins, amino acids, and other components, were trialed and adjusted to find the optimum conditions for P. jirovecii culture. This allowed us to develop a medium that produced a 42.6-fold increase in P. jirovecii qPCR copy numbers after a 48-day culture. Growth was confirmed microscopically by the increasing number and size of actively growing Pneumocystis clusters in the final medium, DMEM-O3. P. jirovecii doubling time was 8.9 days (range 6.9 to 13.6 days). In conclusion, we successfully cultivated P. jirovecii under optimized cell-free conditions in a 70-day long-term culture for the first time. However, further optimization of the culture conditions for this slow grower is indispensable.

The Diagnostic Accuracy of Metagenomic Next-Generation Sequencing in Diagnosing Pneumocystis Pneumonia: A Systemic Review and Meta-analysis

Background

Pneumocystis pneumonia (PCP) is a growing concern as the immunocompromised population expands. Current laboratory approaches are limited. This systematic review aimed to evaluate metagenomic next-generation sequencing (MNGS) tests' performance in detecting PCP.

Methods

Five databases were searched through December 19, 2022, to identify original studies comparing MNGS with clinically diagnosed PCP. To assess the accuracy, symmetric hierarchical summary receiver operating characteristic models were used.

Results

Eleven observational studies reporting 1442 patients (424 with PCP) were included. Six studies focused exclusively on recipients of biologic immunosuppression (none with HIV-associated immunosuppression). Six were exclusively on bronchoalveolar lavage, while 1 was on blood samples. The sensitivity of MGNS was 0.96 (95% CI, 0.90-0.99), and specificity was 0.96 (95% CI, 0.92-0.98), with negative and positive likelihood ratios of 0.02 (95% CI, 0.01-0.05) and 19.31 (95% CI, 10.26-36.36), respectively. A subgroup analysis of studies exclusively including bronchoalveolar lavage (BAL) and blood samples demonstrated a sensitivity of 0.94 (95% CI, 0.78-0.99) and 0.93 (95% CI, 0.80-0.98) and a specificity of 0.96 (95% CI, 0.88-0.99) and 0.98 (95% CI, 0.76-1.00), respectively. The sensitivity analysis on recipients of biologic immunosuppression showed a sensitivity and specificity of 0.96 (95% CI, 0.90-0.98) and 0.94 (95% CI, 0.84-0.98), respectively. The overall confidence in the estimates was low.

Conclusions

Despite the low certainty of evidence, MNGS detects PCP with high sensitivity and specificity. This also applies to recipients of biologic immunosuppression and tests performed exclusively on blood samples without the need for BAL. Further studies are required in individuals with HIV-associated immunosuppression.

Pneumocystis jirovecii pneumonia in intensive care units: a multicenter study by ESGCIP and EFISG

BACKGROUND

Pneumocystis jirovecii pneumonia (PJP) is an opportunistic, life-threatening disease commonly affecting immunocompromised patients. The distribution of predisposing diseases or conditions in critically ill patients admitted to intensive care unit (ICU) and subjected to diagnostic work-up for PJP has seldom been explored.

MATERIALS AND METHODS

The primary objective of the study was to describe the characteristics of ICU patients subjected to diagnostic workup for PJP. The secondary objectives were: (i) to assess demographic and clinical variables associated with PJP; (ii) to assess the performance of Pneumocystis PCR on respiratory specimens and serum BDG for the diagnosis of PJP; (iii) to describe 30-day and 90-day mortality in the study population.

RESULTS

Overall, 600 patients were included in the study, of whom 115 had presumptive/proven PJP (19.2%). Only 8.8% of ICU patients subjected to diagnostic workup for PJP had HIV infection, whereas hematological malignancy, solid tumor, inflammatory diseases, and solid organ transplants were present in 23.2%, 16.2%, 15.5%, and 10.0% of tested patients, respectively. In multivariable analysis, AIDS (odds ratio [OR] 3.31; 95% confidence interval [CI] 1.13-9.64, p = 0.029), non-Hodgkin lymphoma (OR 3.71; 95% CI 1.23-11.18, p = 0.020), vasculitis (OR 5.95; 95% CI 1.07-33.22, p = 0.042), metastatic solid tumor (OR 4.31; 95% CI 1.76-10.53, p = 0.001), and bilateral ground glass on CT scan (OR 2.19; 95% CI 1.01-4.78, p = 0.048) were associated with PJP, whereas an inverse association was observed for increasing lymphocyte cell count (OR 0.64; 95% CI 0.42-1.00, p = 0.049). For the diagnosis of PJP, higher positive predictive value (PPV) was observed when both respiratory Pneumocystis PCR and serum BDG were positive compared to individual assay positivity (72% for the combination vs. 63% for PCR and 39% for BDG). Cumulative 30-day mortality and 90-day mortality in patients with presumptive/proven PJP were 52% and 67%, respectively.

CONCLUSION

PJP in critically ill patients admitted to ICU is nowadays most encountered in non-HIV patients. Serum BDG when used in combination with respiratory Pneumocystis PCR could help improve the certainty of PJP diagnosis.

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.

Detection of Opportunistic Fungi from the Bronchoalveolar Lavage Specimens of Patients with Pulmonary Diseases

Background

Opportunistic fungi are a constantly evolving group of pathogens that become active when the immune system is compromised, begin to multiply, and soon overwhelm the weakened immune system. This study was performed to evaluate the number of opportunistic fungi in bronchoalveolar lavage (BAL) samples of patients with pulmonary diseases.

Materials and Methods

After receiving patients' consent and demographic forms, a total of 120 BAL samples were taken by a pulmonary physician. The etiologic agents were identified by standard morphological and molecular methods. Yeast cells were counted on culture media, and direct smears were precisely examined for the presence of yeasts elements, Pneumocystis, and filamentous fungi.

Results

In this study, 29 (24.1%) patients showed positive direct smears for yeast elements in their BAL samples. The mean colony count of yeasts was 42,000 (CFU/mL) on culture media. Six (5%) species of filamentous fungi, including three (2.5%) isolates of Penicillium species (P. variabile, P. glabrum, and P. thomii), two (1.67%) Aspergillus species (A. flavus and A. fumigatus), 1 case (0.83%) Pseudallescheria boydii were detected. Seven cases (5.83%) of Pneumocystis cysts were observed in the direct smears stained with Giemsa. Identification of all fungi confirmed by molecular or sequencing methods.

Conclusions

Due to the presence of a large number of fungi in the BAL samples and possible physical interference with the selected drugs for treatment, we draw the attention of pulmonologists to this important issue. Rapid diagnosis of fungal infections is essential to optimize treatments and outcomes.