Peter D. Walzer

Pneumocystis carinii Pneumonia in the United States: Epidemiologic, Diagnostic, and Clinical Features

Analysis of 194 patients with confirmed Pneumocystis carinii pneumonia in the United States over a 3-year period revealed that P. carinii pneumonia occurred almost exclusively in the immunosuppressed host who had a serious underlying disease. The epidemiologic features of pneumocystis pneumonia primarily reflected those of the underlying disease. P. carinii was identified antermortem in 81% of the cases usually by biopsy or needle aspiration of the lung, procedures associated with considerable morbidity and morbidity and mortality. Laboratory identification of P. carinii was usually accurate, but errors resulting from fault staining tecnique occurred. Most patients had been ill less than 2 weeks with bilateral diffuse interstitial pneumonia. Leukopenia (white blood cell count less than or equal to 3,00/mm3) and probably severe hypoxia were negative prognostic factors. Although treatment with pentamidine was effective, the drug frequently cased adverse reactions, particularly impaired renal function, when given with other nephrotoxic agents.

Pneumocystis carinii: sequence from ribosomal RNA implies a close relationship with fungi

Pneumocystis carinii is the etiologic agent of a lethal pneumonia which occurs in patients with the acquired immune deficiency syndrome (AIDS) and other immunocompromised hosts. The basic biochemical and genetic characteristics of P. carinii are poorly understood and its taxonomic classification as a protozoan is uncertain. To address the taxonomic question, a method was developed for the extraction of total RNA from P. carinii. Denaturing agarose gel electrophoresis showed the two ribosomal RNA species of P. carinii to be similar in size to those of other lower eukaryotes, including Saccharomyces cerevisiae. Three portions of the small ribosomal RNA of P. carinii were sequenced by reverse transcription from oligonucleotide primers. Three hundred seventy-two nucleotides of sequence were obtained. The sequence derived from P. carinii RNA contained regions that previous phylogenetic studies have shown to be highly variable among species, as well as regions that are highly conserved. Comparison of the P. carinii sequence to corresponding sequences of organisms from other taxa showed the P. carinii sequence to be more similar to sequences from the fungi (Saccharomyces cerevisiae, Neurospora crassa, Candida albicans, and Cryptococcus diffuens) than to protozoan sequences. These data suggest that P. carinii is more closely related to fungi than to protozoa.

Diffuse pulmonary infiltrates in immunosuppressed patients. Prospective study of 80 cases.

Over a two year period, we studied prospectively 80 cases of diffuse pneumonia at Memorial Sloan-Kettering Cancer Center. In 72 per cent of these, the patient had leukemia or lymphoma. Diagnostic procedures consisted of extensive serologic testing for antibody to known respiratory pathogens, including the agent of Legionnaires disease, and culturing of biopsy specimens for bacteria, viruses, mycoplasmas and fungi. Of 44 cases in which open lung biopsy was performed, a specific cause was found in 61.4 per cent: Pneumocystis carinii in 38.6 per cent, other infections in 9.1 per cent and tumor involvement in 13.7 per cent. There were nonspecific pulmonary changes in 38.6 per cent. Of the 56 cases in which biopsy, autopsy or both were performed, a specific diagnosis was made in 69.7 per cent: P. carinii infection in 37.5 per cent and other infections in 12.5 per cent. In cases in which neither biopsy nor autopsy was performed, a specific infection was diagnosed in 33 per cent; no specific diagnosis was made in the remainder. One patient in the entire group had a significant antibody titer for Legionnaires disease. Although diagnostic in some cases, extensive serologic testing proved relatively unfruitful. Pneumocystosis was the most frequent diagnosis in this study. The cause of some cases remained obscure, even after lung biopsy.

Early Predictors of Mortality from Pneumocystis jirovecii Pneumonia in HIV-Infected Patients: 1985–2006

BACKGROUND Pneumocystis jirovecii pneumonia (PCP) remains the leading cause of opportunistic infection among human immunodeficiency virus (HIV)-infected persons. Previous studies of PCP that identified case-fatality risk factors involved small numbers of patients, were performed over few years, and often focused on patients who were admitted to the intensive care unit. OBJECTIVE The objective of this study was to identify case-fatality risk factors present at or soon after hospitalization among adult HIV-infected patients admitted to University College London Hospitals (London, United Kingdom) from June 1985 through June 2006. PATIENTS AND METHODS We performed a review of case notes for 494 consecutive patients with 547 episodes of laboratory-confirmed PCP. RESULTS Overall mortality was 13.5%. Mortality was 10.1% for the period from 1985 through 1989, 16.9% for the period from 1990 through June 1996, and 9.7% for the period from July 1996 through 2006 (P = .142). Multivariate analysis identified factors associated with risk of death, including increasing patient age (adjusted odds ratio [AOR], 1.54; 95% confidence interval [CI], 1.11-2.23; P = .011), subsequent episode of PCP (AOR, 2.27; 95% CI, 1.14-4.52; P = .019), low hemoglobin level at hospital admission (AOR, 0.70; 95% CI, 0.60-0.83; P < .001), low partial pressure of oxygen breathing room air at hospital admission (AOR, 0.70; 95% CI, 0.60-0.81; P < .001), presence of medical comorbidity (AOR, 3.93; 95% CI, 1.77-8.72; P = .001), and pulmonary Kaposi sarcoma (AOR, 6.95; 95% CI, 2.26-21.37; P = .001). Patients with a first episode of PCP were sicker (mean partial pressure of oxygen at admission +/- standard deviation, 9.3+/-2.0 kPa) than those with a second or third episode of PCP (mean partial pressure of oxygen at admission +/- standard deviation, 9.9+/-1.9 kPa; P = .008), but mortality among patients with a first episode of PCP (12.5%) was lower than mortality among patients with subsequent episodes of PCP (22.5%) (P = .019). No patient was receiving highly active antiretroviral therapy before presentation with PCP, and none began highly active antiretroviral therapy during treatment of PCP. CONCLUSIONS Mortality risk factors for PCP were identifiable at or soon after hospitalization. The trend towards improved outcome after June 1996 occurred in the absence of highly active antiretroviral therapy.

HIV-Associated Pneumocystis Pneumonia

During the past 30 years, major advances have been made in our understanding of HIV/AIDS and Pneumocystis pneumonia (PCP), but significant gaps remain. Pneumocystis is classified as a fungus and is host-species specific, but an understanding of its reservoir, mode of transmission, and pathogenesis is incomplete. PCP remains a frequent AIDS-defining diagnosis and is a frequent opportunistic pneumonia in the United States and in Europe, but comparable epidemiologic data from other areas of the world that are burdened with HIV/AIDS are limited. Pneumocystis cannot be cultured, and bronchoscopy with bronchoalveolar lavage is the gold standard procedure to diagnose PCP, but noninvasive diagnostic tests and biomarkers show promise that must be validated. Trimethoprim-sulfamethoxazole is the recommended first-line treatment and prophylaxis regimen, but putative trimethoprim-sulfamethoxazole drug resistance is an emerging concern. The International HIV-associated Opportunistic Pneumonias (IHOP) study was established to address these knowledge gaps. This review describes recent advances in the pathogenesis, epidemiology, diagnosis, and management of HIV-associated PCP and ongoing areas of clinical and translational research that are part of the IHOP study and the Longitudinal Studies of HIV-associated Lung Infections and Complications (Lung HIV).

Adoptive transfer of lymphocytes sensitized to the major surface glycoprotein of Pneumocystis carinii confers protection in the rat.

Pneumocystis carinii is a major opportunistic pathogen and a leading cause of morbidity in patients with AIDS. CD4+ cells have been shown to be important in host defenses against P. carinii, but the antigen(s) involved with this response have not been identified. We undertook the present study to determine whether the major surface glycoprotein (MSG) of P. carinii contains epitopes that can elicit a protective cellular immune response. Spleen cells and purified CD4+ cells isolated from Lewis rats, pulsed 1-4 d with MSG, and injected into corticosteroid-treated Lewis rats with pneumocystosis resulted in significant reduction in the P. carinii burden, as judged by organism quantitation and lung histology. The protective response demonstrated by the donor cells was dependent on previous exposure to P. carinii, cell concentration, and time of incubation with MSG. In addition, reconstitution with MSG-specific CD4+ cells resulted in an early hyperinflammatory response within the lungs of these animals with a high percentage of mortality. Thus, in this model, MSG can elicit an immune response mediated by CD4+ cells, which has a harmful as well as helpful effect on the host, and these responses occur despite the presence of corticosteroids.

Echinocandin treatment of pneumocystis pneumonia in rodent models depletes cysts leaving trophic burdens that cannot transmit the infection.

Fungi in the genus Pneumocystis cause pneumonia (PCP) in hosts with debilitated immune systems and are emerging as co-morbidity factors associated with chronic diseases such as COPD. Limited therapeutic choices and poor understanding of the life cycle are a result of the inability of these fungi to grow outside the mammalian lung. Within the alveolar lumen, Pneumocystis spp., appear to have a bi-phasic life cycle consisting of an asexual phase characterized by binary fission of trophic forms and a sexual cycle resulting in formation of cysts, but the life cycle stage that transmits the infection is not known. The cysts, but not the trophic forms, express β -1,3-D-glucan synthetase and contain abundant β -1,3-D-glucan. Here we show that therapeutic and prophylactic treatment of PCP with echinocandins, compounds which inhibit the synthesis of β -1,3-D-glucan, depleted cysts in rodent models of PCP, while sparing the trophic forms which remained in significant numbers. Survival was enhanced in the echincandin treated mice, likely due to the decreased β -1,3-D-glucan content in the lungs of treated mice and rats which coincided with reductions of cyst numbers, and dramatic remodeling of organism morphology. Strong evidence for the cyst as the agent of transmission was provided by the failure of anidulafungin-treated mice to transmit the infection. We show for the first time that withdrawal of anidulafungin treatment with continued immunosuppression permitted the repopulation of cyst forms. Treatment of PCP with an echinocandin alone will not likely result in eradication of infection and cessation of echinocandin treatment while the patient remains immunosuppressed could result in relapse. Importantly, the echinocandins provide novel and powerful chemical tools to probe the still poorly understood bi-phasic life cycle of this genus of fungal pathogens.

Immunosuppressed Surfactant Protein A–Deficient Mice Have Increased Susceptibility to Pneumocystis carinii Infection

Immunosuppressed Swiss Black mice deficient in surfactant protein A (SP-A(-/-)) and wild-type control mice (SP-A(+/+)) were exposed to Pneumocystis carinii by environmental exposure, intratracheal inoculation, and direct exposure to other infected animals. The frequency and intensity of P. carinii infection were significantly greater in the SP-A(-/-) mice by all 3 methods of exposure. P. carinii free of SP-A and alveolar macrophages were isolated from SP-A(-/-) mice and were tested in an in vitro attachment assay. Pretreatment of P. carinii with human SP-A resulted in a significant dose-dependent increase of the adherence of P. carinii to the macrophages. Thus, SP-A plays a role in host defense against P. carinii in vivo, perhaps by functioning as a nonimmune opsonin.

Activities of antifolate, antiviral, and other drugs in an immunosuppressed rat model of Pneumocystis carinii pneumonia.

The efficacy of antifolate, antiviral, and other drugs was compared in an experimental model of pneumocystosis. Sulfamethoxazole (SMX) administered alone in doses of greater than or equal to 60 mg/kg/day was highly effective in treatment and prophylaxis. Low (less than or equal to 15 mg/kg/day) doses of SMX showed limited, dose-related anti-Pneumocystis carinii activity in therapy but were more effective in prophylaxis. The dihydrofolate reductase (DHFR) inhibitors trimethoprim (TMP), pyrimethamine, and trimetrexate exhibited little anti-P. carinii activity when administered alone and did not enhance the efficacy of SMX; the effects of the DHFR inhibitors could not be related to the dose or the concentration in serum. These data suggested that the rat model is an excellent system for studying the anti-P. carinii activity of sulfonamides but is of limited value in studying DHFR inhibitors. The antiviral drugs azidothymidine, dideoxyinosine, inosine pranobex (Isoprinosine), amantadine, and acyclovir displayed little or no activity against P. carinii; however, azidothymidine did not impair the efficacy of SMX or TMP-SMX. These results supported the clinical practice of giving antiviral agents together with antifolate drugs to patients infected with human immunodeficiency virus and suggested that the beneficial effects of antiviral agents on the occurrence of pneumocystosis are due mainly to their effects on the virus or the host immune response. In contrast to the antiviral drugs, 9-deazainosine, a nucleoside analog with antiprotozoal properties, demonstrated marked activity against P. carinii which was related to dose and route of administration. These data raised the possibility that anti-P. carinii activity is a general property of purine nucleosides and suggested that further exploration of this class of compounds might lead to clinically useful agents.

Pneumocystis carinii: Growth variables and estimates in the A549 and WI-38 VA13 human cell lines

Recent studies indicate that rat Pneumocystis carinii can be propagated in the A549 cell line, an alveolar epithelioid cell line derived from human lung carcinoma. In the present study, growth of P. carinii was compared in the A549 cell line and the WI-38 VA13 subline 2RA, an SV40 transformed derivative of the human fetal fibroblast cell line with epithelioid morphology. Similar P. carinii growth occurred in both cell lines under optimal conditions, but the WI-38 VA13 cell line was usually more sensitive to changes in the culture system. Growth of P. carinii was affected by temperature, environmental gas mixture, motion of the cultures, and source and concentration of serum additives, but not by the presence of antibodies in the medium. A technique was developed for quantitating P. carinii in the lung inoculum which permitted analysis of P. carinii growth during the first 24 hr of culture. Inverted microscope and oil immersion phase-contrast microscopy were very helpful in monitoring the organisms stages of development and viability. Thus, this culture system should be helpful in establishing standard methodology for in vitro work with P. carinii.