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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., (© 2021. The Author(s).)

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., (Copyright © 2020. Published by Elsevier Masson SAS.)

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., Competing Interests: The authors have declared that no competing interests exist.

Despite the discovery of key pattern recognition receptors and CD4+ T cell subsets in laboratory mice, there is ongoing discussion of the value of murine models to reflect human disease. Pneumocystis is an AIDS-defining illness, in which risk of infection is inversely correlated with peripheral CD4+ T cell counts. Due to medical advances in the control of HIV, the current epidemiology of Pneumocystis infection is predominantly due to primary human immunodeficiencies and immunosuppressive therapies. To this end, we found that every human genetic immunodeficiency associated with Pneumocystis infection that has been tested in mice recapitulated susceptibility. For example, humans with a loss-of-function IL21R mutation are severely immunocompromised. We found that IL-21R, in addition to CD4+ T cell intrinsic STAT3 signaling, were required for generating protective antifungal class-switched antibody responses, as well as effector T cell-mediated protection. Furthermore, CD4+ T cell intrinsic IL-21R/STAT3 signaling was required for CD4+ T cell effector responses, including IL-22 production. Recombinant IL-22 administration to Il21r-/- mice induced the expression of a fungicidal peptide, cathelicidin antimicrobial peptide, which showed in vitro fungicidal activity. In conclusion, SPF laboratory mice faithfully replicate many aspects of human primary immunodeficiency and provide useful tools to understand the generation and nature of effector CD4+ T cell immunity.

A 69-year-old man with multiple liver metastases from sigmoid colon cancer received mFOLFOX6 plus cetuximab(Cmab) chemotherapy. A partial response was observed; hence, we performed an extended left hepatectomy, 3 partial liver resections, and a sigmoidectomy. After 4 courses of CapeOX, a recurrent lesion occurred between S8 and S7 of the liver, and we changed the regimen to FOLFIRI plus bevacizumab(BV). Three months later, he had Grade 3 febrile neutropenia and CT scan findings showed ground glass opacity in the superior lobes of both lungs. We diagnosed pneumocystis pneumonia(PCP)and administered steroids and trimethoprim/sulfamethoxazole. The signs of PCP thus improved. PCP during chemotherapy for gastrointestinal cancer is rarely reported, but recently it has increased.

Norway (Rattus norvegicus) and black rats (Rattus rattus) are common peridomestic species, yet little is known about wild rat ecology, including their natural diseases. We describe gross and histological lesions in the respiratory tract of a sample of 711 wild urban rats. A subset was examined for 19 distinct categories of histological lesions in the respiratory tract. Testing for known respiratory pathogens included serology and polymerase chain reaction (PCR) of lung samples. Grossly evident lesions were rare (8/711; 1%). Upper respiratory tract inflammation was present in 93 of 107 (87%) rats and included rhinitis, submucosal and periglandular lymphoplasmacytic tracheitis, and/or tracheal intraluminal necrotic debris and was significantly associated (P < .05) with the presence of cilia-associated respiratory bacillus (CARB), Mycoplasma pulmonis, and increased body mass (odds ratio [OR] = 1.09; 95% confidence interval [CI] = 1.05-1.14 per 10 g). Within the lungs, peribronchiolar and/or perivascular lymphoplasmacytic cuffs were present in 152 of 199 rats (76%) and were also significantly associated (P ≤ .02) with CARB, M. pulmonis, and increased body mass (OR = 1.20; 95% CI = 1.14-1.27 per 10 g). Rats were frequently coinfected with M. pulmonis and CARB, and lesions associated with these pathogens were histologically indistinguishable. Pneumocystis sp was detected in 48 of 102 (47%) rats using PCR but was not significantly associated with lesions. This description of pathology in the respiratory system of wild rats demonstrates that respiratory disease is common. Although the impact of these lesions on individual and population health remains to be investigated, respiratory disease may be an important contributor to wild rat morbidity and mortality., (© The Author(s) 2015.)

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., (2015 BMJ Publishing Group Ltd.)

Background: Despite antiretroviral therapy and trimethoprim-sulfamethoxazole (TMP-SMX) prophylaxis, Pneumocystis pneumonia remains an important serious opportunistic infection in HIV-infected persons. Pneumocystis (Pc) colonization in HIV-infected individuals and in HIV-uninfected smokers is associated with chronic obstructive pulmonary disease (COPD). We previously developed a nonhuman primate model of HIV infection and Pc colonization and demonstrated that Pc colonization correlated with COPD development. In the present study, we examined kinetics of COPD development in non-human primate and tested the effect of Pc burden reduction on pulmonary function by TMP-SMX treatment., Methods: Cynomolgus macaques (n = 16) were infected with simian/human immunodeficiency virus (SHIV89.6P), and natural Pc colonization was examined by nested polymerase chain reaction of serial bronchoalveolar lavage fluid and anti-Pc serology., Results: Eleven of 16 monkeys became Pc colonized by 16 weeks post simian-human immunodeficiency virus (SHIV) infection. Pc colonization of SHIV-infected monkeys led to progressive declines in pulmonary function as early as 4 weeks after Pc detection. SHIV-infected and Pc-negative monkeys maintained normal lung function. At 25 weeks post-SHIV infection, TMP-SMX treatment was initiated in 7 Pc-positive (Pc+) (TMP: 20 mg/kg and SMX: 100 mg/kg, daily for 48 weeks) and 5 Pc-negative (Pc-) monkeys. Four SHIV+/Pc+ remained untreated for the duration of the experiment. Detection frequency of Pc in serial bronchoalveolar lavage fluid (P < 0.001), as well as plasma Pc antibody titers (P = 0.02) were significantly reduced in TMP-SMX-treated macaques compared with untreated., Conclusions: Reduction of Pc colonization by TMP-SMX treatment did not improve pulmonary function, supporting the concept that Pc colonization results in early, permanent obstructive changes in the lungs of immunosuppressed macaques.

Pneumocystis carinii (Pc) β-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 β-glucan biosynthetic genes. Furthermore, when a reconstructed yeast system was used, PcAce2 activated the transcription of the Pneumocystis gsc1 β-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.

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., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Cutaneous Pneumocystis jirovecii infection is rare. It is thought that the disease emerges from a latent infection delivered via hematogenous and/or lymphatic dissemination from a primary lung infection in immunocompromised individuals. A 32-year-old human immunodeficiency virus-positive male was admitted for headache and vomiting. He was diagnosed with meningitis due to Cryptococcus neoformans and sputum tested positive for Pneumocystis. Six months later, he presented with a slightly crusted yellowish brown plaque and 2 similar but smaller papules with telangiectasia near the right angle of the mouth. Biopsy of the area featured histiocytes expanded by foamy cytoplasm as in a xanthoma except that the vacuoles were coarser. Special stains ultimately demonstrated the characteristic disks of Pneumocystis accompanied by a minor component of budding yeasts (Cryptococcus) in the same fields. This case illustrates the utility of adequate special stains in recognizing a mixed cutaneous infection, particularly in human immunodeficiency virus-positive patients, when microscopy presents an odd xanthoma-like lesion.

With increases in the immunocompromised patient population and aging of the HIV+ population, the risk of serious fungal infections and their complications will continue to rise. In these populations, infection with the fungal opportunistic pathogen Pneumocystis jirovecii remains a leading cause of morbidity and mortality. Infection with Pneumocystis (Pc) has been shown to be associated with the development of chronic obstructive pulmonary disease (COPD) in human subjects with and without HIV infection and in non-human primate models of HIV infection. In human studies and in a primate model of HIV/Pc co-infection, we have shown that antibody response to the Pc protein, kexin (KEX1), correlates with protection from colonization, Pc pneumonia, and COPD. These findings support the hypothesis that immunity to KEX1 may be critical to controlling Pc colonization and preventing or slowing development of COPD.

At the end of the 20th century the unique taxonomically enigmatic entity called Pneumocystis carinii was identified as a heterogeneous group of microscopic Fungi, constituted of multiple stenoxenic biological entities largely spread across ecosystems, closely adapted to, and coevolving in parallel with, mammal species. The discoveries and reasoning that led to the current conceptions about the taxonomy of Pneumocystis at the species level are examined here. The present review also focuses on the biological, morphological and phylogenetical features of Pneumocystis jirovecii, Pneumocystis oryctolagi, Pneumocystis murina, P. carinii and Pneumocystis wakefieldiae, the five Pneumocystis species described until now, mainly on the basis of the phylogenetic species concept. Interestingly, Pneumocystis organisms exhibit a successful adaptation enabling them to dwell and replicate in the lungs of both immunocompromised and healthy mammals, which can act as infection reservoirs. The role of healthy carriers in aerial disease transmission is nowadays recognized as a major contribution to Pneumocystis circulation, and Pneumocystis infection of nonimmunosuppressed hosts has emerged as a public health issue. More studies need to be undertaken both on the clinical consequences of the presence of Pneumocystis in healthy carriers and on the intricate Pneumocystis life cycle to better define its epidemiology, to adapt existing therapies to each clinical context and to discover new drug targets., (© 2010 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.)

We investigated the relationship of Pneumocystis colonization, matrix metalloprotease levels in sputum, and airway obstruction in a cohort of human immunodeficiency virus (HIV)-infected outpatients. Pneumocystis-colonized subjects had worse obstruction of airways and higher levels of matrix metalloprotease-12 in sputa, suggesting that Pneumocystis colonization may be important in HIV-associated chronic obstructive pulmonary disease.

The genus Pneumocystis comprises uncultured, highly diversified microfungal organisms able to attach specifically to type-I alveolar epithelial cells and to proliferate in pulmonary alveoli provoking severe pneumonitis. The pathogenic potential of Pneumocystis species, especially of the human-associated Pneumocystis jirovecii, has stimulated a growing interest in these peculiar microfungi. However, a comprehensive understanding of basic biology and pathogenic power of Pneumocystis organisms calls for their recognition as natural, complex entities, without reducing them to their pathogenic role. For many years, the entity named "Pneumocystis carinii" was considered like an anecdotal pulmonary pathogen able to cause pneumonia in immunosuppressed hosts. Only for the last years, marked genetic divergence was documented among the Pneumocystis strains of different mammals. Cross-infection experiments showed that Pneumocystis species are stenoxenous parasites. Mainly on the basis of the Phylogenetic Concept of Species, Pneumocystis strains were considered as genuine species. Five species were described: P. carinii and Pneumocystis wakefieldiae in rats, P. jirovecii in humans, Pneumocystis murina in mice, and Pneumocystis oryctolagi in rabbits. They also present distinctive phenotypic features. Molecular techniques have revealed a high prevalence of Pneumocystis colonization in wild mammals, probably resulting from active airborne horizontal and vertical (transplacental or aerial) transmission mechanisms. Cophylogeny is the evolutionary pattern for Pneumocystis species, which dwelt in the lungs of mammals for more than 100 million years. Consistently, Pneumocystis organisms exhibit successful adaptation to colonize the lungs of both immunocompromised and healthy hosts that can act as infection reservoir. Pneumocystis pneumonia, rarely reported in wild mammals, seems to be a rather unfrequent event. A larger spectrum of Pneumocystis infections related to the heterogeneous level of immune defence found in natural populations, is, however, expected. Pneumocystis infection of immunocompetent hosts emerges therefore as a relevant issue to human as well as animal health.

AIDS-associated otic pneumocystosis is rare. Of 14 cases documented mainly as case reports up to now, only 1 has been reported in the surgical pathology literature. We report 6 males, mean age of 32.3 years, with external auditory canal masses and otorrhea. Two biopsies contained a predominance of granulation tissue with a mixed inflammatory cell infiltrate and elusive foci of foamy exudate. In contrast, 4 biopsies demonstrated conspicuous angiocentric mantles of stippled, foamy exudate. Fibrin was noted in intravascular, perivascular, and intervascular locations. One biopsy demonstrated bordering of the foamy exudate by a palisaded granulomatous reaction, with adjacent discrete giant cell-containing granulomas. Special stains confirmed trophozoites and cysts within the foamy exudate. Review of 2 initial "nondiagnostic" biopsies confirmed granulation tissue and necrotic debris in which Pneumocystis jiroveci was identified in focal foamy exudate. After the diagnosis of otic pneumocystosis, all patients were initiated on trimethoprim-sulfamethoxazole. One patient also had dapsone. Two patients succumbed to pulmonary tuberculosis and 2 were lost to follow-up. One patient with pneumocystis pneumonia did not return for follow-up after 6 weeks. One patient experienced complete resolution of the mass on medical therapy, and is disease free for 4 years. Heightened recognition of the characteristic foamy exudate in an unconventional location remains the gold standard in the timely diagnosis of this eminently treatable disease. In all patients, otic pneumocystosis served as the sentinel of underlying HIV infection and AIDS.

Primary central nervous system T-cell lymphomas are rare and have to be differentiated from reactive lesions. It is therefore essential to use all possible tools to establish the diagnosis, including immunohistochemistry, molecular genetic analysis, and/or cytogenetic methods. In this paper we present the case of a primary cerebellar T-cell lymphoma in a 50-year-old man; a clonal T-cell receptor gene rearrangement was documented. After two cycles of methotrexate therapy the patient developed Pneumocystis carinii-induced pneumonia, dying 10 weeks after his diagnosis. The autopsy did not reveal any residual tumour.

Botryomycosis is an uncommon, chronic, granulomatous and/or suppurative, opportunistic infection affecting the skin and viscera, primarily caused by bacteria. The exact pathogenesis of this infection is not well understood. However, both the host's immune status and microbial infectivity have been implicated in the pathogenesis of this unusual clinical condition. To date, botryomycosis caused by a nonbacterial pathogen has not been reported in the literature. We report a case of cutaneous botryomycosis caused by combined Staphylococcus aureus and Pneumocystis carinii. Cutaneous P. carinii infection without pulmonary involvement is extremely rare.

Various polymerase chain reaction (PCR) amplification strategies have been described for detecting Pneumocystis jiroveci in clinical specimens. Different combinations of primer/target and platforms have been reported to yield varying PCR detection rates. PCR was evaluated on clinical specimens using internal transcribed spacer regions of the rRNA nested, dihydropteroate synthase single and nested, dihydrofolate reductase nested, major surface glycoprotein heminested, mitochondrial large subunit rRNA (mtLSUrRNA) single and nested, 18S rRNA 1-tube nested, and real-time 5S rRNA PCR. The most sensitive PCR was subsequently compared with routine diagnostic immunofluorescence (IF) microscopy. Discrepant PCR and IF results were resolved after review of clinical and histology/cytology records. Major discrepancies were observed among the methods investigated. mtLSUrRNA nested PCR was the most sensitive, produced less false-negative results, and displayed the highest degree of concordance with histology. Direct comparison of mtLSUrRNA nested PCR versus IF yielded low sensitivity and specificity, which were improved for PCR and lowered for IF on review of clinical and laboratory records.

Pneumocystis carinii is an opportunistic fungal pathogen that causes pneumonia (PCP) in immunocompromised individuals. Recent studies have demonstrated that the host's immune response is clearly responsible for the majority of the pathophysiological changes associated with PCP. P. carinii interacts closely with alveolar epithelial cells (AECs); however, the nature and pathological consequences of the epithelial response remain poorly defined. Monocyte chemotactic protein-1 (MCP-1) is involved in lung inflammation, immunity, and epithelial repair and is upregulated during PCP. To determine whether AECs are an important source of MCP-1 in the P. carinii-infected lung, in vivo and in vitro studies were performed. In situ hybridization showed that MCP-1 mRNA was localized to cells with morphological characteristics of AECs in the lungs of infected mice. In vitro studies demonstrated that P. carinii stimulated a time- and dose-dependent MCP-1 response in primary murine type II cells that was preceded by JNK activation. Pharmacological inhibition of JNK nearly abolished P. carinii-stimulated MCP-1 production, while ERK, p38 MAPK, and TNF receptor signaling were not required. Furthermore, delivery of a JNK inhibitory peptide specifically to pulmonary epithelial cells using a recombinant adenovirus vector blocked the early lung MCP-1 response following intratracheal instillation of infectious P. carinii. JNK inhibition did not affect P. carinii-stimulated production of macrophage inflammatory protein-2 in vitro or in vivo, indicating that multiple signaling pathways are activated in P. carinii-stimulated AECs. These data demonstrate that AECs respond to P. carinii in a proinflammatory manner that may contribute to the generation of immune-mediated lung injury.

Fitness of cell-mediated immunity is thought to depend on TCR diversity; however, this concept has not been tested formally. We tested the concept using JH(-/-) mice that lack B cells and have TCR Vbeta diversity <1% that of wild-type mice and quasimonoclonal (QM) mice with oligoclonal B cells and TCR Vbeta diversity 7% that of wild-type mice. Despite having a TCR repertoire contracted >99% and defective lymphoid organogenesis, JH(-/-) mice rejected H-Y-incompatible skin grafts as rapidly as wild-type mice. JH(-/-) mice exhibited T cell priming by peptide and delayed-type hypersensitivity, although these responses were less than normal owing either to TCR repertoire contraction or defective lymphoid organogenesis. QM mice with TCR diversity contracted >90%, and normal lymphoid organs rejected H-Y incompatible skin grafts as rapidly as wild type mice and exhibited normal T cell priming and normal delayed-type hypersensitivity reactions. QM mice also resisted Pneumocystis murina like wild-type mice. Thus, cell-mediated immunity can function normally despite contractions of TCR diversity >90% and possibly >99%.

Immune-mediated lung injury is an important component of Pneumocystis pneumonia (PcP)-related immunorestitution disease (IRD). However, the individual contribution of CD4(+) and CD8(+) T cells to the pathophysiology of IRD remains undetermined. Therefore, IRD was modeled in severe combined immunodeficient mice, and specific T cell depletion was used to determine how T cell subsets interact to affect the nature and severity of disease. CD4(+) cells were more abundant than CD8(+) cells during the acute stage of IRD that coincided with impaired pulmonary physiology and organism clearance. Conversely, CD8(+) cells were more abundant during the resolution phase following P. carinii clearance. Depletion of CD4(+) T cells protected mice from the acute pathophysiology of IRD. However, these mice could not clear the infection and developed severe PcP at later time points when a pathological CD8(+) T cell response was observed. In contrast, mice depleted of CD8(+) T cells efficiently cleared the infection but developed more severe disease, an increased frequency of IFN-gamma-producing CD4(+) cells, and a prolonged CD4(+) T cell response than mice with both CD4(+) and CD8(+) cells. These data suggest that CD4(+) T cells mediate the acute respiratory disease associated with IRD. In contrast, CD8(+) T cells contributed to neither lung injury nor organism clearance when CD4(+) cells were present, but instead served to modulate CD4 function. In the absence of CD4(+) cells, CD8(+) T cells produced a nonprotective, pathological immune response. These data suggest that the interplay of CD4(+) and CD8(+) T cells affects the ultimate outcome of PcP-related IRD.

As a result of improved diagnosis, treatment, and supportive care for HIV-infected patients, AIDS in developed countries has now become a chronic infection with prolonged survival time, but longterm complications are increasing contributors to morbidity and mortality. HIV-infected patients are at increased risk for the development of pulmonary complications, including chronic obstructive pulmonary disease (COPD); however, the mechanisms associated with this increased susceptibility have not been defined. Infectious agents may contribute to the development of COPD by upregulating inflammatory mediators in the lung that act in concert with cigarette smoke to promote lung pathology. Studies in human subjects and non-human primate models of AIDS suggest that the inflammatory response to asymptomatic carriage or colonization by the opportunistic pathogen, Pneumocystis sp. (Pc), is similar to that of COPD, which is characterized by influx of CD8+ T cells, neutrophils, and macrophages into the lungs. We have shown a high frequency of Pc colonization among asymptomatic HIV-infected subjects and in non-HIV infected subjects with COPD. To investigate the role of Pc in the progression of obstructive lung disease in HIV infections, we developed a non-human primate model of Pc colonizatoin and infection in simian immunodeficiency virus (SIV)-infected macaques. These animals develop a prolonged colonization state characterized by a persistent influx of CD8+ T cells and neutrophils, and local increases in IL-8, IFN-gamma, and TNF-alpha. SIV-infected Pc-colonized monkeys show progressive decline in pulmonary function compared to SIV-infected monkeys. We hypothesize that in the context of AIDS-immune dysfunction, Pc colonization induces inflammatory responses leading to changes in pulmonary function and architecture similar to that seen in emphysema. Information gained from these studies will lead to the development of interventions to prevent lung injury associated with Pc colonization and the development of HIV-associated COPD.

Pneumocystis pneumonia is a common component of the acquired immunodeficiency syndrome (AIDS) in the United States. Extrapulmonary pneumocystosis, however, is much less common. Rare cases have been reported in lymph nodes, bone marrow, spleen, pleura, gastrointestinal tract, liver, common bile duct, pancreas, skin, thyroid, and eye. A 39-yr-old man with history of chest wall injuries from gunshot and stabbing presented with multiple pleural masses clinically suspicious of metastatic deposits from an unknown primary. Fine-needle aspiration biopsy of the largest pleural mass revealed extrapulmonary pneumocystis, which led to the diagnosis of AIDS. Similar to the previous reports of pneumocystis mass lesions in extrapulmonary sites, the current case is associated with exuberant vascular proliferation and Langhans' giant cell reaction. Neovascularization and histiocytic influx from the newly formed blood vessels and Langhans' giant cell reaction seem to be a common tissue reaction to the massive deposition of pneumocystis organisms in extrapulmonary sites in patients with AIDS., (Copyright 2005 Wiley-Liss, Inc.)

A 62-year-old man with progressive cerebellar and brainstem dysfunction had gadolinium-enhancing lesions in basal ganglia and occipital lobe on MRI suggestive of primary CNS lymphoma (PCNSL). The patient, who had been treated with high-dose steroid hormones for several months, developed respiratory failure and expired before a histological diagnosis could be obtained. The postmortem examination showed Pneumocystis cariniiwas the cause of death. Pathology of the brain showed a necrotizing vasculopathy affecting the white matter of the cerebrum and cerebellum with involvement of the basal ganglia and the periventricular gray matter. Other organs such as liver, lung, and kidneys were spared. Necrotizing vasculopathy is a novel entity that should be considered in the differential diagnosis of PCNSL.

Surfactant protein A (SP-A), a member of the collectin family, selectively binds to Pneumocystis carinii and mediates interactions between pathogen and host alveolar macrophages in vitro. To test the hypothesis that mice lacking SP-A have delayed clearance of Pneumocystis organisms and enhanced lung injury, wild-type C57BL/6 (WT) and SP-A-deficient mice (SP-A(-/-)) with or without selective CD4(+)-T-cell depletion were intratracheally inoculated with Pneumocystis organisms. Four weeks later, CD4-depleted SP-A-deficient mice had developed a more severe Pneumocystis infection than CD4-depleted WT (P. carinii pneumonia [PCP] scores of 3 versus 2, respectively). Whereas all non-CD4-depleted WT mice were free of PCP, intact SP-A(-/-) mice also had evidence of increased organism burden. Pneumocystis infection in SP-A-deficient mice was associated histologically with enhanced peribronchial and/or perivascular cellularity (score of 4 versus 2, SP-A(-/-) versus C57BL/6 mice, respectively) and a corresponding increase in bronchoalveolar lavage (BAL) cell counts. Increases in SP-D content, gamma interferon, interleukin-4, interleukin-5, and tumor necrosis factor alpha in BAL fluid occurred but were attenuated in PCP-infected SP-A(-/-) mice compared to WT mice. There were increases in total BAL NO levels in both infected groups, but nitrite levels were higher in SP-A(-/-) mice, indicating a reduction in production of higher oxides of nitrogen that was also reflected in lower levels of 3-nitrotyrosine staining in the SP-A(-/-) group. We conclude that despite increases in inflammatory cells, SP-A-deficient mice infected with P. carinii exhibit an enhanced susceptibility to the organism and attenuated production of proinflammatory cytokines and reactive oxygen-nitrogen species. These data support the concept that SP-A is a local effector molecule in the lung host defense against P. carinii in vivo.

Pneumocystis causes pneumonia in immunodeficient hosts but also likely causes infection in healthy hosts. To characterize infection in healthy mice, we developed and validated a real-time polymerase chain reaction assay for quantitation of Pneumocystis carinii f. sp. muris. In healthy mice exposed to Pneumocystis-infected animals, organisms were first detected at 2-3 weeks, peaked at 5-6 weeks, and were cleared by 7-9 weeks. The peak organism load in healthy animals was 2-3 logs lower than that in immunodeficient animals. This approach should facilitate studies of anti-Pneumocystis immune mechanisms in healthy hosts and provide insights into the development of Pneumocystis pneumonia in immunodeficient hosts.

Objective: To establish a rat model for Pneumocystis carinii infection and to clone surface glycoprotein A (GpA) gene of Pneumocystis carini., Methods: Immunosuppression was induced in 5 rats with an immunosuppresion regimen consisting mainly of dexamethasone in a course of 2 weeks, after which pulmonary homogenates of rats infected with Pneumocystis carinii were fed to the immunosuppressed rats. Immunosuppression was maintained for approximately 4 weeks after the feeding to induce Pneumocystis pneumonia in the rats. GpA gene was subsequently amplified from the rats with pneumonia as confirmed by microscope and PCR detection, and was subcloned into T-vector for the transformation of Escherichia coli JM109 strain., Results: Pneumocystis carinii was detected by microscope and PCR detection in rats with immunosuppression. The length of PCR product was 319 bp as shown by agarose electrophoresis., Conclusion: The rat model of Pneumocystis carinii infection can be established by immunosuppression with dexamethasone and a single oral administration of the pathogen.

A 30-year-old man under treatment for acute leukemia died of Candida sepsis and Pneumocystis carinii pneumonia. A small granuloma containing Pneumocystis carinii was found in one optic nerve.

A case of the very early phase of Pneumocystis carinii pneumonia in a human immunodeficiency virus (HIV)-negative man with alcoholic hepatitis and cirrhosis treated with steroids is presented. A 40-year-old man with a 10-year history of alcohol abuse was admitted to hospital with jaundice, fever and macrohematuria. Laboratory examinations revealed neutrophilic leukocytosis and a serum bilirubin level of 13.9 mg/dL. The serum bilirubin level rose to 28.5 mg/dL over 1 month. Prednisolone administered orally for 10 days produced a slight improvement in the jaundice and fever. After an interval of a week, it was resumed and maintained for 22 days (total dose, 1555 mg) until the patient died of a massive hemorrhage from ruptured vessels of a gastric ulcer. An autopsy disclosed P. carinii pneumonia in the lower lobe of the left lung, cytomegalovirus infection in both lungs and the esophagus, and esophageal candidiasis. To our knowledge, this is the first report of P. carinii pneumonia together with cytomegalovirus infection in an HIV-negative alcoholic patient. The present case suggests that a rare opportunistic infection such as P. carinii pneumonia might be caused by treating cirrhosis and alcoholic hepatitis with corticosteroids, even if only for a relatively short period.

Pneumocystis carinii is primarily an opportunistic pathogen infecting patients with AIDS and other immunocompromised patients, and ordinarily does not affect immunocompetent persons. We report isolated P. carinii infection of bilateral adrenal glands in a non-immunocompromised adult male, leading to fatal Addisonian crisis. Diagnosis of P. carinii was established on the basis of cytopathology and microbiological tests, using conventional staining techniques and direct immunofluorescence on ultrasound-guided fine needle aspirates and trucut needle biopsy specimen from adrenal glands. P. carinii pneumonia and other fungal infections of the adrenal glands were excluded by appropriate tests. Absence of HIV infection was established by negative ELISA for HIV I and II antibodies and Western blot analysis at the time of presentation and 45 d later. Normal blood total leukocyte and CD4 lymphocyte counts and IgG and IgA levels confirmed the immunocompetent status of the patient. The patient improved with anti-Pneumocystis treatment and corticosteroid replacement, but succumbed to an episode of Addisonian crisis triggered by a diarrheal illness.

Objective: To examine the pathological changes in the liver of an AIDS patient with complicated infection of Pneumocystis carinii(PC)., Methods: A liver biopsy was made. The tissue was stained with HE, PAS, Giemsa, GMS, and acid-fast staining, and examined under light microscope and transmission electron microscope., Results: Granulomas (acid-fast negative) in the tissue and numerous pathogens (PAS positive) in hepatic sinusoids were detected. Giemsa and GMS staining and electron microscopy all confirmed that the pathogen was Pneumocystis carinii., Conclusion: The pathological findings revealed a diffuse extrapulmonary infection of Pneumocystis carinii in the patient of AIDS.

Histopathologic evaluation combined with a period of immunosuppression has been the standard procedure for detection of Pneumocystis carinii in commercial rat colonies. Variation in induction regimens and in the sensitivity of detection methods may result in underreporting of the presence of P. carinii in breeding colonies or delay its detection. In the present study, methylprednisolone and cyclophosphamide were evaluated for the ability to induce P. carinii infection in rats from an enzootically infected commercial barrier colony. The presence of P. carinii was detected by histopathologic methods and by amplification of a targeted region of the P. carinii thymidylate synthase gene by PCR over the 8-week study period. Sera taken from rats prior to either induction regimen were evaluated for the presence of P. carinii-specific antibodies by the immunoblotting technique. Few significant differences in ability to induce organism burden or in histopathology were observed between the two immunosuppressive regimens. However, a dramatic loss of weight over the study period was observed in rats treated with methylprednisolone but not in rats treated with cyclophosphamide. Although histopathologic changes attributable to P. carinii did not appear before 2 weeks with either immunosuppressant, the presence of the organism in these animals was detected by immunoblotting and PCR. Cyst scores and the intensities of the histopathologic lesions increased during the study period, but the number of rats exhibiting evidence of P. carinii infection did not change after week 3. These results suggest that use of the PCR method on postmortem lung tissue of rats without prior induction regimens or identification of anti-P. carinii antibodies in antemortem serum samples is a sufficiently sensitive method for detection of the presence of a P. carinii carrier state in rodent breeding colonies.

Background: Pneumocystis carinii (PC) otitis is a rare opportunistic infection of the acquired immunodeficiency syndrome (AIDS). Initially hearing loss and otalgia occur with thickening of the tympanic membrane and the bordering skin of the ear canal. Otorrhea, ear polyps, perforation of tympanic membrane, destruction of mastoidal bone, and participation of cranial nerves are observed. Diagnosis is established histologically. The treatment of the parasite is by trimethoprim-sulfamethoxazole combinations. The immunological situation seems to be better than in PC pneumonia. Due to the underlying immunological incompetence the infection can not be expected to limit itself. To prevent severe complications as sequestrating mastoiditis, early diagnosis and specific surgical and medical treatment are necessary.

Background: Ocular disease, especially the development of choroidal lesions, is a known extrapulmonary manifestation of Pneumocystis carinii infection in the acquired immune deficiency syndrome (AIDS). To our knowledge, conjunctival involvement due to P. carinii has not been described previously., Methods: The authors describe a 33-year-old homosexual male with AIDS in whom a large placoid, white lesion developed involving the tarsal conjunctiva of the right upper lid. Conjunctival malignancy was suspected and biopsies and swabs were taken. At this time, the patient had been receiving monthly aerosolized pentamidine prophylaxis for 18 months, and there was neither a history of pneumonia nor any clinical signs of disseminated infection due to P. carinii., Results: Histopathologic examination results of the conjunctival biopsy specimen showed a necrotic, frothy tissue surrounded by activated fibroblasts. Within this material, Gomori methenamine silver stains showed numerous round and cup-like cysts of P. carinii, confirming the diagnosis that had already been obtained by an indirect fluorescent-antibody stain of a conjunctival smear specimen., Conclusions: The presence of white placoid conjunctival lesions in a patient with AIDS may indicate an infection due to P. carinii. Conjunctival disease due to P. carinii widens the spectrum of AIDS-associated ophthalmic pneumocystosis.

Extrapulmonary involvement with Pneumocystis carinii has been described in 0.5%-2.5% of persons with AIDS. One hundred nine patients with AIDS and confirmed extrapulmonary pneumocystosis were identified, and seven of these patients (including our patients) had central nervous system (CNS) pneumocystosis. Of these seven patients, six had prior AIDS-related complications, and three had previous P. carinii pneumonia. Six patients had CNS symptoms, one of whom underwent a focal neurological examination. No cases were diagnosed before death. The involved sites were the cerebral cortex (2 patients), meninges (2), pituitary gland (1), putamen (1), and nonspecified locations (3). In two patients, organisms were seen around blood vessels, and in five patients there was concurrent neuropathology. In summary, CNS involvement with P. carinii usually occurs as a late complication of AIDS and probably represents hematogenous dissemination.

Objective: Pneumocystis carinii pneumonia is the most common and serious of the pulmonary complications of AIDS. Despite this, many basic aspects in the pathogenesis of HIV-associated P carinii pneumonia are unknown. We therefore undertook a light and electron microscopic study of transbronchial biopsy specimens to compare pathologic features of P carinii pneumonia and other HIV-related lung diseases., Design and Patients: Thirty-seven consecutive HIV-infected patients undergoing a diagnostic bronchoscopy., Results: P carinii pneumonia was characterized by an increase in inflammation, edema, exudate, fibrosts, type II pneumocyte proliferation, and cellular infiltration of the alveolar wall when compared with other lung diseases (all p < 0.05). Electron microscopy showed apposition of the trophozoite to the type I pneumocyte. Erosion of type I pneumocytes was observed in 13 of 15 patients with P carinii pneumonia, whereas none without P carinii pneumonia had this finding (p < 0.05). Erosion of the type II pneumocyte was not observed., Conclusion: Inflammation, interstitial fibrosis, and alveolar epithelial erosion are characteristic features of P carinii pneumonia. The changes may form the pathologic basis for the respiratory failure seen in patients with P carinii pneumonia. Electron microscopy did not show any diagnostie advantage over conventional light microscopy using routine stains.

Extrapulmonary infection with Pneumocystis carinii, although uncommon, is increasingly recognized. Use of aerosolized pentamidine versus a systemic medication is thought to be a contributing factor due to the low concentrations of drug that are incapable of suppressing systemic infection. Infection with P carinii has been reported in every organ system including the gastrointestinal system. A 28-year-old acquired immunodeficiency syndrome patient receiving prophylaxis with aerosolized pentamidine who presented with a solitary rectal ulcer is reported. Initial biopsy was characteristic of extrapulmonary P carinii infection, with numerous organisms present. Occasional cytomegalovirus inclusion bodies were noted which may have been a copathogen but which were not treated. Treatment with intravenous pentamidine resulted in documented eradication of P carinii and complete resolution of the ulcer. Although lower gastrointestinal pneumocystosis has been described without ulceration, this is the first description of rectal ulceration presenting as the initial manifestation of extrapulmonary pneumocystosis.