Clinical characteristics and risk factors associated with Pneumocystis jirovecii infection in patients with solid tumors: study of thirteen-year medical records of a large cancer center.

BACKGROUND: Pneumocystis jirovecii pneumonia (PCP)-related risk factors among patients with solid tumors are not completely defined. Thus, we aimed to characterize PCP cases with underlying solid tumors, to highlight the factors contributing to its development besides the prolonged use of moderate-to-high dose corticosteroids. METHODS: We retrospectively reviewed the medical records of patients with solid tumors diagnosed with PCP between 2006 and 2018 at a cancer center in Tokyo, Japan. Demographic and clinical data were collected, which included malignancy types, total lymphocyte count, coexisting pulmonary disease, chemotherapy, radiation therapy, corticosteroid use, and PCP-attributable mortality. RESULTS: Twenty cases of PCP with solid tumors were documented in 151,718 patients and 788,914 patient-years. Lung cancer (n = 6, 30%) was the most common underlying tumor, followed by breast cancer (n = 3, 15%). Only six (30%) patients were taking a dosage of ≥20 mg prednisone equivalents daily for ≥4 weeks from the onset of PCP. Among the remaining 14 patients, seven (50%) had coexisting pulmonary diseases, 10 (71%) had received chemotherapy within 90 days prior to PCP diagnosis, seven (50%) had undergone chest radiation therapy before PCP diagnosis, seven (50%) had received only intermittent corticosteroids, and one (7%) received no corticosteroids. Mortality attributable to PCP was 40%. CONCLUSIONS: More than half of the patients were not taking a dosage of ≥20 mg prednisone equivalents daily for ≥4 weeks. Multiple other factors (e.g., lymphocytopenia, radiation to chest) may have potentially contributed to PCP in patients with solid tumors in a composite manner. We need to establish a method for estimating the likelihood of PCP taking multiple factors into account in this patient population.

[Pneumocystis jirovecii and quantitative PCR: Pneumonia or colonization?] / Pneumocytis jirovecii et PCR quantitative : pneumonie ou colonisation à Pneumocystis jirovecii ?

BACKGROUND: Quantitative PCR to detect Pneumocystis jirovecii (Pj) is a new tool for the diagnosis of Pneumocystis jirovecii pneumonia (PJP). The yield of this technique, in cases of low fungal burden, when the standard technique using immunofluorescence (IF) is negative, needs to be evaluated. METHODS: We retrospectively reviewed the charts of all patients with a positive PCR but negative IF test (PCR+/IF-) in bronchoalveolar lavage (BAL) fluid performed over one year. We used an algorithm based on underlying immunosuppression, clinical picture, thoracic CT scan appearances, existence of an alternative diagnosis and the patient's outcome on treatment. Using this, each case was classified as probable PJP, possible PJP or colonization. RESULTS: Among the 416 BAL performed, 48 (12%) were PCR+/IF- and 43 patients were analyzed. Patients were mostly male (56%) with a median age of 60 years. Thirty-five (84%) were immunocompromised: 4 (9%) HIV-infected patients, 26 (60%) with hematologic or solid organ cancer, 3 (7%) were renal transplant recipients. Seven (16%) were classified as probable PPJ and 9 (21%) as possible PJP. Patients with a probable or possible PJP were more frequently admitted to the ICU (P<0.02) and had higher risk of death (P<0.01) when compared to those with colonization. Median PCR levels were very low and were not different between PJP or colonized patients (P=0.23). CONCLUSIONS: Among patients with a positive Pj PCR in BAL but with negative IF, only 37% had probable or possible PJP and PCR could not discriminate PJP from colonization.

Surfactant protein-D modulation of pulmonary macrophage phenotype is controlled by S-nitrosylation.

Surfactant protein-D (SP-D) is a regulator of pulmonary innate immunity whose oligomeric state can be altered through S-nitrosylation to regulate its signaling function in macrophages. Here, we examined how nitrosylation of SP-D alters the phenotypic response of macrophages to stimuli both in vivo and in vitro. Bronchoalveolar lavage (BAL) from C57BL6/J and SP-D-overexpressing (SP-D OE) mice was incubated with RAW264.7 cells ± LPS. LPS induces the expression of the inflammatory genes Il1b and Nos2, which is reduced 10-fold by SP-D OE-BAL. S-nitrosylation of the SP-D OE-BAL (SNO-SP-D OE-BAL) abrogated this inhibition. SNO-SP-D OE-BAL alone induced Il1b and Nos2 expression. PCR array analysis of macrophages incubated with SP-D OE-BAL (±LPS) shows increased expression of repair genes, Ccl20, Cxcl1, and Vcam1, that was accentuated by LPS. LPS increases inflammatory gene expression, Il1a, Nos2, Tnf, and Ptgs2, which was accentuated by SNO-SP-D OE-BAL but inhibited by SP-D OE-BAL. The transcription factor NF-κB was identified as a target for SNO-SP-D by IPA, which was confirmed by Trans-AM ELISA in vitro. In vivo, SP-D overexpression increases the burden of infection in a Pneumocystis model while increasing cellular recruitment. Expression of iNOS and the production of NO metabolites were significantly reduced in SP-D OE mice relative to C57BL6/J. Inflammatory gene expression was increased in infected C57BL6/J mice but decreased in SP-D OE. SP-D oligomeric structure was disrupted in C57BL6/J infected mice but unaltered within SP-D OE. Thus SP-D modulates macrophage phenotype and the balance of multimeric to trimeric SP-D is critical to this regulation.

Primary infection by Pneumocystis induces Notch-independent Clara cell mucin production in rat distal airways.

Clara cells are the main airway secretory cells able to regenerate epithelium in the distal airways through transdifferentiating into goblet cells, a process under negative regulation of the Notch pathway. Pneumocystis is a highly prevalent fungus in humans occurring between 2 and 5 months of age, a period when airways are still developing and respiratory morbidity typically increases. Pneumocystis induces mucus hyperproduction in immunocompetent host airways and whether it can stimulate Clara cells is unknown. Markers of Clara cell secretion and Notch1 activation were investigated in lungs of immunocompetent rats at 40, 60, and 80 days of age during Pneumocystis primary infection with and without Valproic acid (VPA), a Notch inducer. The proportion of rats expressing mucin increased in Pneumocystis-infected rats respect to controls at 60 and 80 days of age. Frequency of distal airways Clara cells was maintained while mRNA levels for the mucin-encoding genes Muc5B and Muc5ac in lung homogenates increased 1.9 and 3.9 times at 60 days of infection (P. = 0.1609 and P. = 0.0001, respectively) and protein levels of the Clara cell marker CC10 decreased in the Pneumocystis-infected rats at 60 and 80 days of age (P. = 0.0118 & P. = 0.0388). CC10 and Muc5b co-localized in distal airway epithelium of Pneumocystis-infected rats at day 60. Co-localization of Muc5b and Ki67 as marker of mitosis in distal airways was not observed suggesting that Muc5b production by Clara cells was independent of mitosis. Notch levels remained similar and no transnucleation of activated Notch associated to Pneumocystis infection was detected. Unexpectedly, mucus was greatly increased at day 80 in Pneumocystis-infected rats receiving VPA suggesting that a Notch-independent mechanism was triggered. Overall, data suggests a Clara to goblet cell transdifferentiation mechanism induced by Pneumocystis and independent of Notch.

Intrinsic Programming of Alveolar Macrophages for Protective Antifungal Innate Immunity Against Pneumocystis Infection.

Invasive fungal infections, including Pneumocystis Pneumonia (PcP), remain frequent life-threatening conditions of patients with adaptive immune defects. While innate immunity helps control pathogen growth early during infection, it is typically not sufficient for complete protection against Pneumocystis and other human fungal pathogens. Alveolar macrophages (AM) possess pattern recognition molecules capable of recognizing antigenic and structural determinants of Pneumocystis. However, this pathogen effectively evades innate immunity to infect both immunocompetent and immunosuppressed hosts, albeit with differing outcomes. During our studies of mouse models of PcP, the FVB/N strain was identified as unique because of its ability to mount a protective innate immune response against Pneumocystis infection. In contrast to other immunocompetent strains, which become transiently infected prior to the onset of adaptive immunity, FVB/N mice rapidly eradicated Pneumocystis before an adaptive immune response was triggered. Furthermore, FVB/N mice remained highly resistant to infection even in the absence of functional T cells. The effector mechanism of innate protection required the action of functional alveolar macrophages, and the adoptive transfer of resistant FVB/N AMs, but not susceptible CB.17 AMs, conferred protection to immunodeficient mice. Macrophage IFNγ receptor signaling was not required for innate resistance, and FVB/N macrophages were found to display markers of alternative activation. IFNγ reprogrammed resistant FVB/N macrophages to a permissive M1 biased phenotype through a mechanism that required direct activation of the macrophage IFNγR. These results demonstrate that appropriately programmed macrophages provide protective innate immunity against this opportunistic fungal pathogen, and suggest that modulating macrophage function may represent a feasible therapeutic strategy to enhance antifungal host defense. The identification of resistant and susceptible macrophages provides a novel platform to study not only the mechanisms of macrophage-mediated antifungal defense, but also the mechanisms by which Pneumocystis evades innate immunity.

Genotyping of Pneumocystis jirovecii in colonized patients with various pulmonary diseases.

Pneumocystis jirovecii is an opportunistic fungus causing Pneumocystis pneumonia primarily in immunosuppressed patients. However, immunocompetent individuals may become colonized and, as asymptomatic carriers, serve as reservoirs of the pathogen. Moreover, these asymptomatic carriers are at higher risk of developing pneumonia if favorable conditions occur. This study aimed to determine the prevalence of P. jirovecii in patients with various pulmonary diseases and to characterize the genetic diversity of organisms circulating in the studied population. Bronchial washing specimens from 105 patients were tested for presence of P. jirovecii using nested polymerase chain reaction (PCR) targeting the mtLSU rRNA gene, as well as immunofluorescence microscopy. Multilocus sequence typing involving analysis of three loci-mtLSU rRNA, CYB, and SOD-was used for genotyping analysis. P. jirovecii DNA was detected in 17 (16.2%) patients. Amplification of the SOD locus was successful only in five cases (29.4% of the positive patients), while mtLSU rRNA and CYB were genotyped in all positive samples. Therefore, combined genotypes were identified based only on mtLSU rRNA and CYB loci. Eight different genotypes were identified, with Pj 1 and Pj 2 being the most prevalent (29.4% of patients each). There was no statistical correlation between these genotypes and demographic or clinical data; however, we found that infection with mutant CYB strains occurred only in patients diagnosed with lung cancer. Of the potential predictors examined, only immunosuppressive treatment was significantly associated with colonization. In conclusion, patients with various respiratory diseases, especially when immunosuppressed, are at risk of Pneumocystis colonization.

Pneumocystis-Driven Inducible Bronchus-Associated Lymphoid Tissue Formation Requires Th2 and Th17 Immunity.

Inducible bronchus-associated lymphoid tissue (iBALT) is an ectopic lymphoid structure composed of highly organized T cell and B cell zones that forms in the lung in response to infectious or inflammatory stimuli. Here, we develop a model for fungal-mediated iBALT formation, using infection with Pneumocystis that induces development of pulmonary lymphoid follicles. Pneumocystis-dependent iBALT structure formation and organization required CXCL13 signaling. Cxcl13 expression was regulated by interleukin (IL)-17 family members, as Il17ra-/-, Il17rb-/-, and Il17rc-/- mice failed to develop iBALT. Interestingly, Il17rb-/- mice have intact Th17 responses, but failed to generate an anti-Pneumocystis Th2 response. Given a role for Th2 and Th17 immunity in iBALT formation, we demonstrated that primary pulmonary fibroblasts synergistically upregulated Cxcl13 transcription following dual stimulation with IL-13 and IL-17A in a STAT3/GATA3-dependent manner. Together, these findings uncover a role for Th2/Th17 cells in regulating Cxcl13 expression and provide an experimental model for fungal-driven iBALT formation.

A candidate gene approach of the calcineurin pathway to identify variants associated with clinical outcomes in renal transplantation.

AIM: To investigate the potential influence of variants in genes involved in the calcineurin pathway on the efficacy and toxicity of calcineurin inhibitors in renal transplantation. MATERIALS & METHODS: Twenty-three polymorphisms in thirteen genes were tested in 381 renal transplant recipients receiving ciclosporin (n = 221) or tacrolimus (n = 160) and mycophenolate mofetil. Data were collected prospectively over the first year post-transplantation. RESULTS: Multivariate survival analyses revealed no genetic associations with biopsy proven acute graft rejection and serious infections. Donor-recipient Cytomegalovirus mismatch was the only variable associated with serious infection. CONCLUSION: This large exploratory study casts doubts on the potential interest of genetic biomarkers related to CNI pharmacodynamics but associations with other phenotypes in transplantation deserve further studies.

Granulomatous-lymphocytic interstitial lung disease and recurrent sinopulmonary infections in a patient with Good's syndrome.

Good's syndrome is a rare primary immunodeficiency associated with adult thymoma. Complications are mainly autoimmune manifestations and recurrent infections with encapsulated bacteria. Only one possible case of combined granulomatous-lymphocytic interstitial lung disease (GL-ILD) and Good's syndrome have been described earlier, but the patient died at the time of diagnosis. This is the first case of GL-ILD in Good's syndrome with a successful outcome. We present a case of a 43-year-old man with GL-ILD, who suffered from recurrent infections of Haemophilus influenzae and Pneumocystis jirovecii, with 8-year follow-up. After a thymectomy, he was diagnosed with Good's syndrome and GL-ILD. He was treated with prophylactic pivampicillin, quinolones and cephalosporins for his recurrent P. jirovecii and H. influenzae infections, an approach that proved unsuccessful due to resistance, with relapse after cessation. He was stabilised with oral diaminodiphenyl-sulfone for P. jirovecii and colistimethate-sodium inhalations for H. influenzae, which is a new approach to prophylactic treatment.

Dihydropteroate synthase gene mutation rates in Pneumocystis jirovecii strains obtained from Iranian HIV-positive and non-HIV-positive patients.

The dihydropteroate sulfate (DHPS) gene is associated with resistance to sulfa/sulfone drugs in Pneumocystis jirovecii. We investigated the DHPS mutation rate in three groups of Iranian HIV-positive and HIV-negative patients by polymerase chain reaction-restricted fragment length polymorphism analysis. Furthermore, an association between P. jirovecii DHPS mutations and strain typing was investigated based on direct sequencing of internal transcribed spacer region 1 (ITS1) and ITS2. The overall P. jirovecii DHPS mutation rate was (5/34; 14.7%), the lowest rate identified was in HIV-positive patients (1/16; 6.25%) and the highest rate was in malignancies patients (3/11; 27.3%). A moderate rate of mutation was detected in chronic obstructive pulmonary disease (COPD) patients (1/7; 14.3%). Most of the isolates were wild type (29/34; 85.3%). Double mutations in DHPS were detected in patients with malignancies, whereas single mutations at codons 55 and 57 were identified in the HIV-positive and COPD patients, respectively. In this study, two new and rare haplotypes were identified with DHPS mutations. Additionally, a positive relationship between P. jirovecii strain genotypes and DHPS mutations was identified. In contrast, no DHPS mutations were detected in the predominant (Eg) haplotype. This should be regarded as a warning of an increasing incidence of drug-resistant P. jirovecii strains.

Extra-pulmonary Pneumocystis jiroveci infection: a case report

In physical examination abdominal tenderness, gate disturbance and penile herpetic lesions were detected. Decreased disc height at T11-T12 level was detected in chest X-ray. Abdominal sonography and CT scan revealed hypo dense lesions in Lt left Lobe of liver and multiple hypo dense splenic and pancreatic lesions, ascitis, Lt left sided pleural effusion, thickening of jejuneal mucosa and edema of bowel wall. Vertebral body lesion and paravertebral abscess, bony calvarial involvement and adjacent extra axial brain lesion were observed in imaging were other findings. RNA analysis for HIV was positive. Vertebral lesion biopsy and aspiration of splenic lesion were performed and pathology revealed Pneumocystis jirovecii suggestive of extra pulmonary Pneumocystis carinii infection.

Comparative genomics of pneumocystis species suggests the absence of genes for myo-inositol synthesis and reliance on inositol transport and metabolism.

UNLABELLED: In the context of deciphering the metabolic strategies of the obligate pathogenic fungi in the genus Pneumocystis, the genomes of three species (P. carinii, P. murina, and P. jirovecii) were compared among themselves and with the free-living, phylogenetically related fission yeast (Schizosaccharomyces pombe). The underrepresentation of amino acid metabolism pathways compared to those in S. pombe, as well as the incomplete steroid biosynthesis pathway, were confirmed for P. carinii and P. jirovecii and extended to P. murina. All three Pneumocystis species showed overrepresentation of the inositol phosphate metabolism pathway compared to that in the fission yeast. In addition to those known in S. pombe, four genes, encoding inositol-polyphosphate multikinase (EC 2.7.1.151), inositol-pentakisphosphate 2-kinase (EC 2.7.1.158), phosphoinositide 5-phosphatase (EC 3.1.3.36), and inositol-1,4-bisphosphate 1-phosphatase (EC 3.1.3.57), were identified in the two rodent Pneumocystis genomes, P. carinii and P. murina. The P. jirovecii genome appeared to contain three of these genes but lacked phosphoinositide 5-phosphatase. Notably, two genes encoding enzymes essential for myo-inositol synthesis, inositol-1-phosphate synthase (INO1) and inositol monophosphatase (INM1), were absent from all three genomes, suggesting that Pneumocystis species are inositol auxotrophs. In keeping with the need to acquire exogenous inositol, two genes with products homologous to fungal inositol transporters, ITR1 and ITR2, were identified in P. carinii and P. murina, while P. jirovecii contained only the ITR1 homolog. The ITR and inositol metabolism genes in P. murina and P. carinii were expressed during fulminant infection as determined by reverse transcriptase real-time PCR of cDNA from infected lung tissue. Supplementation of in vitro culture with inositol yielded significant improvement of the viability of P. carinii for days 7 through 14. IMPORTANCE: Microbes in the genus Pneumocystis are obligate pathogenic fungi that reside in mammalian lungs and cause Pneumocystis pneumonia in hosts with weakened immune systems. These fungal infections are not responsive to standard antifungal therapy. A long-term in vitro culture system is not available for these fungi, impeding the study of their biology and genetics and new drug development. Given that all genomes of the Pneumocystis species analyzed lack the genes for inositol synthesis and contain inositol transporters, Pneumocystis fungi, like S. pombe, appear to be inositol auxotrophs. Inositol is important for the pathogenesis, virulence, and mating processes in Candida albicans and Cryptococcus neoformans, suggesting similar importance within the Pneumocystis species as well. This is the first report to (i) characterize genes in the inositol phosphate metabolism and transport pathways in Pneumocystis species and (ii) identify inositol as a supplement that improved the viability of P. carinii in in vitro culture.

Extra-pulmonary Pneumocystis jiroveci infection: a case report.

In physical examination abdominal tenderness, gate disturbance and penile herpetic lesions were detected. Decreased disc height at T11-T12 level was detected in chest X-ray. Abdominal sonography and CT scan revealed hypo dense lesions in Lt left Lobe of liver and multiple hypo dense splenic and pancreatic lesions, ascitis, Lt left sided pleural effusion, thickening of jejuneal mucosa and edema of bowel wall. Vertebral body lesion and paravertebral abscess, bony calvarial involvement and adjacent extra axial brain lesion were observed in imaging were other findings. RNA analysis for HIV was positive. Vertebral lesion biopsy and aspiration of splenic lesion were performed and pathology revealed Pneumocystis jirovecii suggestive of extra pulmonary Pneumocystis carinii infection.

Pneumocystis jirovecii can be productively cultured in differentiated CuFi-8 airway cells.

UNLABELLED: Although Pneumocystis jirovecii is a well-known and serious pathogen, all previous attempts to isolate, cultivate, and propagate this fungus have failed. This serious challenge in microbiology was addressed in the present study. We examined whether P. jirovecii could be cultured in a permanent three-dimensional air-liquid interface culture system formed by CuFi-8 cells, a differentiated pseudostratified airway epithelial cell line. Cultured pseudostratified cells were inoculated with bronchoalveolar fluid that had been confirmed to be positive for P. jirovecii using PCR. Five days later, the cells and basal medium were harvested and tested for P. jirovecii using quantitative PCR (qPCR), commercially available immunofluorescence detection assays, and Grocott staining of formalin-fixed, paraffin-embedded thin sections of infected-cell cultures. We successfully productively cultivated and propagated P. jirovecii from these P. jirovecii-positive bronchoalveolar lavage fluid (BALF) samples. Furthermore, we provide evidence that P. jirovecii induced cytopathic effects on lung epithelial cells and was even invasive in cell culture. To the best of our knowledge, the cell culture system developed herein represents the first methodology to enable molecular analyses of this pathogen's life cycle and further in vitro studies of P. jirovecii, such as assessments of drug sensitivity and resistance as well as investigations of the pathogen's stability against environmental factors and disinfectants. IMPORTANCE: This is the first report of the successful productive cultivation and propagation of Pneumocystis jirovecii, a human-pathogenic fungus of major clinical significance. These findings are groundbreaking because they will influence the field of diagnostic microbiology, facilitate the testing of antibiotics against P. jirovecii, and enable stability studies of this pathogen when exposed to the environmental factors and chemicals that hospitals are required to use for disinfection. Because productively culturing P. jirovecii has been attempted unsuccessfully for several decades, this study represents a breakthrough in this field.

MyD88 signaling regulates both host defense and immunopathogenesis during pneumocystis infection.

The immune response protects against Pneumocystis infection but is also a key component of Pneumocystis pneumonia (PcP)-related immunopathogenesis. Signaling through myeloid differentiation factor 88 (MyD88) is critical for activation of immune pathways downstream of TLRs and IL-1R. To determine whether MyD88 regulates normal host defense against Pneumocystis, nonimmunosuppressed wild-type (WT) and MyD88-deficient mice were infected. MyD88(-/-) mice had higher early Pneumocystis burdens than did WT mice but mounted an effective adaptive immune response and cleared Pneumocystis similarly to WT. However, MyD88(-/-) mice displayed a more intense and prolonged pulmonary immune response than did WT mice. To determine the role of MyD88 in the development of PcP-related immunopathogenesis, WT and MyD88(-/-) mice were rendered susceptible to PcP by depletion of CD4(+) T cells. At 4 wk postinfection, CD4-depleted WT and MyD88(-/-) mice harbored similar organism burdens, but MyD88(-/-) mice were protected from the PcP-related respiratory impairment observed in WT mice. Improved pulmonary physiology in MyD88(-/-) mice correlated with lower lung CCL2 levels and reduced cell recruitment. However, by 5 wk postinfection, the overall health of MyD88(-/-) mice began to deteriorate rapidly relative to WT, with accelerated weight loss, impaired lung function, and exacerbated alveolar inflammation. This physiological decline of MyD88(-/-) mice was associated with increased TNF-α and IFN-γ in the lung, and by the inability to control Pneumocystis burden. Thus, MyD88 is not required for resistance to Pneumocystis infection, but limits the adaptive immune response in immunocompetent mice. In the setting of active PcP, MyD88 signaling contributes to both immunopathogenesis and control of fungal burden.

Prevalence and genotype distribution of Pneumocystis jirovecii in Cuban infants and toddlers with whooping cough.

This study describes the prevalence and genotype distribution of Pneumocystis jirovecii obtained from nasopharyngeal (NP) swabs from immunocompetent Cuban infants and toddlers with whooping cough (WC). A total of 163 NP swabs from 163 young Cuban children with WC who were admitted to the respiratory care units at two pediatric centers were studied. The prevalence of the organism was determined by a quantitative PCR (qPCR) assay targeting the P. jirovecii mitochondrial large subunit (mtLSU) rRNA gene. Genotypes were identified by direct sequencing of mtLSU ribosomal DNA (rDNA) and restriction fragment length polymorphism (RFLP) analysis of the dihydropteroate synthase (DHPS) gene amplicons. qPCR detected P. jirovecii DNA in 48/163 (29.4%) samples. mtLSU rDNA sequence analysis revealed the presence of three different genotypes in the population. Genotype 2 was most common (48%), followed in prevalence by genotypes 1 (23%) and 3 (19%); mixed-genotype infections were seen in 10% of the cases. RFLP analysis of DHPS PCR products revealed four genotypes, 18% of which were associated with resistance to sulfa drugs. Only contact with coughers (prevalence ratio [PR], 3.51 [95% confidence interval {CI}, 1.79 to 6.87]; P = 0.000) and exposure to tobacco smoke (PR, 1.82 [95% CI, 1.14 to 2.92]; P = 0.009) were statistically associated with being colonized by P. jirovecii. The prevalence of P. jirovecii in infants and toddlers with WC and the genotyping results provide evidence that this population represents a potential reservoir and transmission source of P. jirovecii.

Growth and airborne transmission of cell-sorted life cycle stages of Pneumocystis carinii.

Pneumocystis organisms are airborne opportunistic pathogens that cannot be continuously grown in culture. Consequently, the follow-up of Pneumocystis stage-to-stage differentiation, the sequence of their multiplication processes as well as formal identification of the transmitted form have remained elusive. The successful high-speed cell sorting of trophic and cystic forms is paving the way for the elucidation of the complex Pneumocystis life cycle. The growth of each sorted Pneumocystis stage population was followed up independently both in nude rats and in vitro. In addition, by setting up a novel nude rat model, we attempted to delineate which cystic and/or trophic forms can be naturally aerially transmitted from host to host. The results showed that in axenic culture, cystic forms can differentiate into trophic forms, whereas trophic forms are unable to evolve into cystic forms. In contrast, nude rats inoculated with pure trophic forms are able to produce cystic forms and vice versa. Transmission experiments indicated that 12 h of contact between seeder and recipient nude rats was sufficient for cystic forms to be aerially transmitted. In conclusion, trophic- to cystic-form transition is a key step in the proliferation of Pneumocystis microfungi because the cystic forms (but not the trophic forms) can be transmitted by aerial route from host to host.

Typing of Pneumocystis jirovecii isolates from Iranian immunosuppressed patients based on the Internal Transcribed Spacer (ITS) region of the rRNA gene.

Since there have been no published molecular studies of Pneumocystis jirovecii isolates from Iranian patients, we investigated the genotypes of such isolates recovered from HIV-infected patients, those undergoing cancer chemotherapy and patients with chronic obstructive pulmonary disease (COPD). P. jirovecii typing, based on ITS1 and ITS2 sequence analysis, was performed on 34 isolates from Iranian immunosuppressed patients. In total, 44 genotypes were detected of which relative to ITS1, eight known genotypes (A, B, C, E, G, H, N and O) and one novel sequence were noted. Eight known genotypes (b, c, e, g, h, i, j and n) were also found with ITS2. The most frequent ITS1 and ITS2 genotypes were E (21/44, 47.7%) and g (22/44, 50%), respectively. From determined haplotypes, the four most frequent ones were Eg (11/44, 25%), Gg (5/44, 11.3%), Gi (4/44, 9.1%), Ei (3/44, 6.8%), and Hg (3/44, 6.8%). Two novel haplotypes (Hb and Hi) were also identified, along with mixed infections as seven (20.5%) patients were found to have more than one haplotype. It is suggested that novel haplotypes in Iranian patients may be generated through sexual recombination within the host.

The Pneumocystis Ace2 transcription factor regulates cell wall-remodeling genes and organism virulence.

Pneumocystis carinii (Pc) ß-glucans are major components of the organism cell wall; yet, the regulation of Pc cell wall genesis and remodeling is not well understood. Ace2 transcription factors, which are present in many fungi, regulate glucanases and other enzymes needed for cell wall remodeling. The cloning and heterologous expression of PcAce2 in ace2Δ Saccharomyces cerevisiae demonstrated that PcAce2 can restore the defective glucanase and endochitinase gene expression of the mutant as well as regulate cell wall ß-glucan biosynthetic genes. Furthermore, when a reconstructed yeast system was used, PcAce2 activated the transcription of the Pneumocystis gsc1 ß-glucan synthetase, confirming the activity of a Pc transcription factor on a native Pneumocystis promoter and gene for the first time. We further observed that Pneumocystis binding to host extracellular matrix proteins and lung epithelial cells induced the phosphorylation (activation) of the PcAce2 transcription factor. Finally, we present a novel method that confirms the role of PcAce2 in modulating organism virulence using ace2Δ Candida glabrata infection in neutropenic mice. Together, these results indicate that the adherence of Pc to lung matrix proteins and epithelial cells leads to the activation of the Ace2 transcription factor, which regulates cell wall degradation and biosynthesis genes that are required for cell wall remodeling.

Clinical significance of Pneumocystis jiroveci in patients with active tuberculosis.

Pneumocystis colonization has been associated with airway inflammation and obstruction. We conducted a retrospective cohort study to investigate the clinical significance of Pneumocystis in the airway of patients with active tuberculosis. Of the 108 respiratory specimens tested positive for M. tuberculosis by polymerase chain reaction (PCR), 11 (10.2%) were also positive for Pneumocystis by PCR. Compared with patients tested negative for Pneumocystis, those with Pneumocystis had a higher serum alanine transaminase level, a greater likelihood of requiring oxygen supplementation, and a worse 30-day mortality. The proportion of patients with chronic obstructive pulmonary disease was not significantly different between the 2 groups, but lung malignancy was more prevalent among patients with Pneumocystis. Multivariate analysis showed that Pneumocystis was independently associated with oxygen supplementation. Our study has shown an association between the detection of Pneumocystis in lower respiratory tract specimens and greater impairment of pulmonary function among patients with active tuberculosis.