NIH conference. Pneumocystis pneumonia: from bench to clinic

Pneumocystis Carinii Pneumonia in Adult Non-HIV Disorders

Pneumocystis carinii pneumonia (PCP) remains a serious infection in the immunocompromised host (in the absence of HIV infection) and presents significant management and diagnostic challenges to ICU physicians. Non-HIV PCP is generally abrupt in onset, and follows a fulminate course with high rates of hospitalization, ICT admission, respiratory failure, and requirement for intubation. Mortality is generally high, especially if mechanical ventilation is required. Non-invasive ventilatory support may be considered, although the rapid progression to respiratory failure often necessitates intubation at the time of presentation. Bronchoscopy is often required to establish the diagnosis, and empirical antimicrobial treatment specifically targeted to P. carinii should be initiated while awaiting confirmation. Adjunctive corticosteroids may accelerate recovery, although their use has not yet been established in non-HIV PCP. For the ICU physicians to diagnose PCP, the non-specific presentation of an acute febrile illness and respiratory distress with diffuse pulmonary infiltrates requires a high clinical index of suspician, familiarity with clinical conditions associated with increased risk for PCP, and a low threshold for bronchoscopy to establish the diagnosis.

Immunosuppression in patients with high-grade gliomas treated with radiation and temozolomide

PURPOSE

Patients with high-grade gliomas (HGG) routinely receive radiation, temozolomide, and glucocorticoids. As each of these is immunosuppressive, we conducted a prospective, multicenter study to follow CD4 counts over time and determine whether low CD4 counts were associated with adverse outcomes.

EXPERIMENTAL DESIGN

Patients with newly diagnosed HGG had CD4 counts drawn before initiating standard therapy and monthly thereafter for 1 year. Information on hospitalizations, infections, glucocorticoid use, survival, and cause of death were also collected.

RESULTS

Ninety-six evaluable patients were accrued [85% glioblastoma, median age of 57, median Karnofsky performance status (KPS) = 90]. The median CD4 count before radiation and temozolomide treatment was 664 cells/mm(3). The CD4 count nadir occurred 2 months after initiating therapy when 73% of patients had CD4 counts less than 300 cells/mm(3) and 40% had less than 200 cells/mm(3). CD4 counts remained low throughout the year of follow-up. Patients with CD4 counts less than 200 cells/mm(3)at 2 months had shorter survival than those with higher counts (median: 13.1 vs. 19.7 months, P = 0.002). Median survival was related to CD4 toxicity grades (I = 23.8 months, II = 19.7 months, III-IV = 13.1 months, P = 0.009). The adjusted HR for death attributable to 2-month CD4 count below 200 was 1.66 (P = 0.03). Eighty-eight percent of deaths resulted from disease progression, whereas only 2.5% were due to infection.

CONCLUSIONS

Severe reductions in CD4 counts in patients with newly diagnosed HGG treated with radiation and temozolomide treatment are common, treatment-related, long-lasting, and associated with early death from tumor progression.

Pneumocystis carinii: a fungus resistant to antifungal therapies - mechanisms of action of antipneumocystis drugs

Pneumocystis carinii is a pathogen that causes a potentially lethal pneumonia in patients with AIDS and other immunodeficiency states. This review discusses the mechanisms of action of four classes of antipneumocystis agents: inhibitors of ergosterol synthesis and function, 1,3-beta-glucan synthase inhibitors, antifolates and DNA binding agents. Investigations of P. carinii's biologic pathways affected by the antipneumocystis actions of each of these classes of agents has generated important insights into the organism's basic biology and supports the organism's classification as a fungus. In addition, this review discusses some recent P. carinii research and its potential impact on drug development.

Pneumocystis carinii pneumonia in HIV negative patients with primary brain tumors

BACKGROUND

Pneumnocystis carinii pneumonia (PCP) is an opportunistic infection with rather adverse outcomes. An unexpected increase in cases of PCP was noted in the brain tumor population at the Johns Hopkins Hospital (JHH) in 2000. This prompted the present review of the clinical features and risk factors for PCP in the human immunodeficiency virus (HIV) negative brain tumor population.

METHODS

The study was located at the JHH. A retrospective review of medical records was done to identify patients with discharge diagnosis of PCP from 1980 to 2001. Patients who were HIV positive were excluded. A detailed analysis was done of patients with brain tumors.

RESULTS

From 1980 to 2001, 468 cases of PCP were identified, diagnosed histologically or clinically, of which 110 were patients with an underlying malignancy. Of the 110 cases 15 were seen in the brain tumor population. Of these, 6 patients were seen in 2000 and one in early 2001. Three of these had primary central nervous system (CNS) lymphoma (PCNSL) on high dose methotrexate. Eight of the fifteen episodes (53.3%) were fatal despite institution of antibiotics and supportive therapy.

CONCLUSION

The incidence and mortality due to Pneumocystis carinii among the brain tumor population is increasing. While corticosteroids are known immunosupressants, prescribing patterns for these medications has not changed lately. However, high dose methotrexate is now being used in PCNSL and could be a complicating factor. Since effective prophylaxis exists, it should be considered in patients with brain tumors receiving high dose steroids, high dose methotrexate or with lymphopenia.

Pneumocystis carinii pneumonia in patients with and without HIV infection

Advances in the prevention and treatment of Pneumocystis carinii pneumonia in HIV infected patients have led to a decrease in the incidence and improved outcomes. Pneumocystis carinii pneumonia continues to be problematic in non-HIV infected immunocompromised patients.

PCR-based quantification of Pneumocystis carinii in in vitro systems

In many laboratories, PCR has become a routine method for the sensitive diagnosis of Pneumocystis carinii in patient samples. In contrast, quantification of fungal numbers in in vitro setups still largely relies on more conventional procedures such as histological stainings. These are time consuming and their applications are limited when dealing with small fungal numbers contaminated with tissue and cellular debris. This study presents a sensitive and rapid method for P. carinii quantification based on PCR analysis that can be easily integrated into standard detection procedures without requiring any major additional steps. P. carinii-specific PCR performed with total DNA extracted from both standard samples with known fungal numbers and experimental samples was quantified relative to PCR products of a standard concentration from a control plasmid added prior to DNA extraction. This measure controlled for variations in DNA extraction and PCR efficiency among the samples to be compared. The correlation between analyzed P. carinii-specific DNA and the actual fungal numbers employed was highly significant.

Unsuspected Pneumocystis carinii pneumonia at presentation of severe primary immunodeficiency

BACKGROUND

Pneumocystis carinii is an important pathogen in immunodeficiency but may be an unrecognised cause of respiratory compromise.

OBJECTIVES

To ascertain the incidence of P carinii pneumonia (PCP) at presentation of severe combined immunodeficiency (SCID), whether it had been diagnosed, and the effect of treatment on outcome.

SETTING

The supraregional paediatric bone marrow transplant unit for primary immunodeficiencies at Newcastle General Hospital.

METHODS

Retrospective case note review of infants referred with a diagnosis of SCID from 1992 to 1998.

RESULTS

Ten of 50 infants had PCP at presentation; only one was diagnosed before transfer. Eight were diagnosed by bronchoalveolar lavage and two by lung biopsy. In only one was P carinii identified in nasopharyngeal secretions. Five required ventilation for respiratory failure but all were successfully treated with co-trimoxazole and methylprednisolone with or without nebulised budesonide. Nine survived to bone marrow transplantation and four are long term survivors after bone marrow transplantation; no deaths were related to PCP.

CONCLUSIONS

PCP is a common presenting feature of SCID but is rarely recognised. Bronchoalveolar lavage or lung biopsy are needed for diagnosis. Treatment with co-trimoxazole is highly successful.

Molecular characterization of KEX1, a kexin-like protease in mouse Pneumocystis carinii

Expression screening of a Pneumocystis carinii-infected mouse lung cDNA library with specific monoclonal antibodies (mAbs) led to the identification of a P. carinii cDNA with extensive homology to subtilisin-like proteases, particularly fungal kexins and mammalian prohormone convertases. The 3.1 kb cDNA contains a single open reading frame encoding 1011 amino acids. Structural similarities to fungal kexins in the deduced primary amino acid sequence include a putative proenzyme domain delineated by a consensus autocatalytic cleavage site (Arg-Glu-Lys-Arg), conserved Asp, His, Asn and Ser residues in the putative catalytic domain, a hydrophobic transmembrane spanning domain, and a carboxy-terminal cytoplasmic domain with a conserved tyrosine motif thought to be important for localization of the protease in the endoplasmic reticulum and/or Golgi apparatus. Based on these structural similarities and the classification of P. carinii as a fungus, the protease was named KEX1. Southern blotting of mouse P. carinii chromosomes localized kex1 to a single chromosome of approximately 610 kb. Southern blotting of restriction enzyme digests of genomic DNA from P. carinii-infected mouse lung demonstrated that kex1 is a single copy gene. The function of kexins in other fungi suggests that KEX1 may be involved in the post-translational processing and maturation of other P. carinii proteins.

Use of adjunctive corticosteroids in severe adult non-HIV Pneumocystis carinii pneumonia

STUDY OBJECTIVE

To examine the use of adjunctive corticosteroids in cases of severe Pneumocystis carinii pneumonia (PCP) in non-HIV-infected adult patients.

DESIGN

Retrospective review of medical records.

SETTING

Tertiary care urban teaching hospital.

PATIENTS

Review identified 31 consecutive histologically confirmed primary cases of adult non-HIV-related PCP. Complete records were available for 30 patients, including 20 male and 10 female patients with a mean age of 58.3+/-15 years (+/-SD). Underlying conditions included organ transplantation (n=13), long-term immunosuppressive therapy (n=9), and chemotherapy for malignancy (n=8). All patients had documented PO2 <65 mm Hg or arterial oxygen saturation <90% on room air.

INTERVENTIONS

Following the identification of P carinii, in addition to trimethoprim-sulfamethoxazole or pentamidine therapy, 16 patients received increased steroids (> or =60 mg prednisone daily equivalent; increased high-dose steroid group), whereas 14 patients were maintained on a regimen of low doses (< or =30 mg prednisone equivalent daily) or had steroid therapy tapered (low-dose steroid group).

RESULTS

The increased high-dose steroid group demonstrated a shorter required duration for mechanical ventilation (6.3+/-6 days vs 18.0+/-21 days; p=0.047), a shorter duration of ICU admission (8.5+/-7 days vs 15.8+/-8 days; p=0.025), and a shorter duration of supplemental oxygen use (10.0+/-4 vs 32.2+/-33; p=0.05). The hospital duration to discharge for the nine survivors in each group favored the use of corticosteroids (15.4+/-5 days vs 36.3+/-33 days; p=0.077). Similar rates were observed for intubation (75% vs 57%; p=0.442) and in-hospital mortality (44% vs 36%; p=0.722).

CONCLUSIONS

These preliminary data suggest that high-dose adjunctive corticosteroids may accelerate recovery in cases of severe adult non-HIV PCP.

Antigenic properties of recombinant glycosylated and nonglycosylated Pneumocystis carinii glycoprotein A polypeptides expressed in baculovirus-infected insect cells

Since a continuous culture system is not yet available for the opportunistic fungal pathogen Pneumocystis carinii, obtaining suitable amounts of purified P. carinii antigens free of mammalian-host lung contaminants is difficult. Hence, production of recombinant antigen possessing epitopes found in native P. carinii antigens is critical for immunological studies. We utilized the baculovirus expression vector system (BEVS) in insect cells to determine whether B-cell epitopes present in the protein core of a native P. carinii surface glycoprotein were conserved in the recombinant polypeptide, and to investigate its glycosylation by insect cells. B-cell epitopes were retained, but the insect cells appeared to hyperglycosylate the recombinant protein.

Pneumocystis carinii pneumonia: the status of Pneumocystis biochemistry

Pneumocystis carinii pneumonia remains a prevalent opportunistic disease among immunocompromised individuals. Although aggressive prophylaxis has decreased the number of acute P. carinii pneumonia cases, many patients cannot tolerate the available drugs, and experience recurrence of the infection, which can be fatal. It is now generally agreed that the organism should be placed with the fungi, but the identification of extant fungal species representing its closest kins, remains debated. Most recent data indicate that P. carinii represents a diverse group of organisms. Since the lack of methods for the continuous subcultivation of this organism hampered P. carinii research, molecular cloning and nucleotide sequencing approaches led the way for understanding the biochemical nature of this pathogen. However, within the last 5 years, the development of improved protocols for isolating and purifying viable organisms from infected mammalian host lungs has enabled direct biochemical and metabolism studies on the organism. The protein moiety of the major high mol. wt surface antigen, represented by numerous isoforms, is encoded by different genes. These proteins are post-transcriptionally modified by carbohydrates and lipids. The organism has the shikimic acid pathway that leads to the formation of compounds which mammals cannot synthesise (e.g., folic acid), hence drugs that inhibit these pathways are effective against the pathogen. Ornithine decarboxylase has now been detected; rapid and complete depletion of polyamines occurs in response to difluoromethylornithine (DFMO). Instead of ergosterol (the major sterol of higher fungi), P. carinii synthesises distinct delta7, C-24-alkylated sterols. An unusual C32 sterol, pneumocysterol, has been identified in human-derived P. carinii. Another signature lipid discovered is cis-9,10-epoxy stearic acid. CoQ10, identified as the major ubiquinone homologue, is synthesised de novo by P. carinii. Atovaquone and other hydroxynaphthoquinone drugs with anti-P. carinii activity probably inhibit pathogen respiration as CoQ analogues. Unlike its effects on Plasmodium, atovaquone does not inhibit the P. carinii dihydroorotate dehydrogenase and pyrimidine metabolism.

Pneumocystis carinii pneumonia in Malawian children

Sixty children aged between 1 and 23 months admitted to Queen Elizabeth Central Hospital in Blantyre, Malawi for diagnosis of acute lower respiratory tract infections (ALRI) were investigated for laboratory diagnosis of Pneumocystis carinii pneumonia (PCP) by indirect immunofluorescence assay on nasopharyngeal secretions. P. carinii was found in five of the 60 children. Three PCP cases had AIDS. The clinical presentation of children with PCP was of little diagnostic value and all the children were infants. Arterial oxygen saturation was significantly lower in PCP cases. Of the five PCP cases, four died, indicating that the marked hypoxaemia was associated with poor prognosis. These results indicate that an immunofluorescence assay on nasopharyngeal secretions could be used for first-line diagnosis of PCP in Africa.

The role of alveolar macrophages in Pneumocystis carinii degradation and clearance from the lung

Although studies indicate that alveolar macrophages participate in host defense against Pneumocystis carinii, their role in organism degradation and clearance from the lung has not yet been established. We, therefore, quantified the uptake and degradation of 35S-labeled P. carinii by cultured macrophages, demonstrating significant degradation of P. carinii over 6 h. We further evaluated the role of macrophages in elimination of P. carinii from the living host. Rats received either intratracheal PBS, liposomal PBS (L-PBS), or liposomal dichloromethylene diphosphonate (L-Cl2MDP), a preparation which leads to selective depletion of macrophages. Over 72 h, L-Cl2MDP-treated animals had loss of > 85% of their alveolar macrophages. In contrast, L-PBS-treated rats had cellular differentials identical to rats receiving PBS. Macrophage-depleted rats and controls were next inoculated with P. carinii and organism clearance was determined after 24 h. P. carinii elimination was evaluated with both cyst counts and an ELISA directed against glycoprotein A (gpA), the major antigen of P. carinii. Both assays indicated that macrophage-depleted rats had substantial inpairment of P. carinii clearance compared to L-PBS- or PBS-treated rats. These data provide the first direct evidence that macrophages mediate elimination of P. carinii from the living host.

Pneumocystis carinii pneumonia

Pneumocystis carinii pneumonia (PCP) remains an important complication of AIDS. Advances have been made in establishing the taxonomy of the organism but the life cycle of the organism and pathogenetic mechanisms of disease remain obscure. In HIV patients the incidence of PCP has decreased because of widespread use of prophylaxis and survival of those with PCP has improved with use of adjunctive corticosteroid therapy. Less toxic drug therapies are still needed as well as better noninvasive diagnostic techniques.

Pneumonia and tuberculosis in pregnancy

Antepartum pneumonia requires prompt evaluation and empiric antimicrobial therapy. The choice of antimicrobial therapy depends on maternal risk factors, symptoms, and clinical presentation. Although laboratory studies such as culture and serology should be obtained, they may not always yield a specific etiologic agent. However, prompt empiric treatment and supportive care should lead to good maternal and fetal outcomes. Similarly, in most cases, proper diagnosis and treatment of TB during pregnancy yield good maternal and fetal outcomes. TB screening is essential for the growing population of individuals with HIV infection and recent immigrants from areas where tuberculosis is endemic.

Pneumocystis carinii and cytomegalovirus infections in severely ill, HIV-infected African infants

Unlike in the industrialized world, in which Pneumocystis carinii and cytomegalovirus (CMV) are major respiratory opportunistic organisms, the causes of severe pneumonia, which accounts for much of the mortality in HIV-infected infants in developing countries, are not known, although tuberculosis has been associated with HIV in adults. We report on post-mortem lung and liver biopsies obtained soon after death from 36 HIV-infected infants and 36 HIV-uninfected matched controls who had been admitted with severe pneumonia to an ICU. Nineteen of the HIV-infected infants were classified by WHO criteria as having AIDS and 17 'symptomatic HIV'. P. carinii and CMV were detected significantly more frequently in lung tissue from the AIDS patients (14 of 18 samples tested, p < 0.01; 14 of 18 samples tested, p < 0.01, respectively) as compared with matched controls. P. carinii was detected in two of 13 lung biopsies from symptomatic HIV infants, but in none of the controls. Lung tissue obtained from AIDS patients had P. carinii and CMV more frequently (p < 0.01, p < 0.01, respectively) than that from symptomatic HIV patients. CMV was also detected in excess in liver tissue from AIDS infants (five of 18 samples) as compared with that from symptomatic HIV (0 of 16; p = 0.03) and matched controls (two of 34; p = 0.04). Ante-mortem investigations revealed more CMV infections in AIDS patients (four of 19) than in matched controls (0 of 36; p < 0.01). Tuberculosis was detected in post-mortem lung tissue from only one patient with symptomatic HIV infection. The finding that pathogens (P. carinii, CMV) most frequently detected in seriously ill African infants with HIV/AIDS are similar to those in their counterparts from industrialized countries has implications for improved management in the former.

Pneumocystis pneumonia in brain tumor patients: risk factors and clinical features

We reviewed the clinical features and risk factors for Pneumocystis carinii pneumonia (PCP) in patients with brain tumors (BTs) seen at our institution between 1980 and 1992. Previously rare, this opportunistic infection appears to be increasing among HIV-negative cancer patients receiving immunosuppressive medications. Recent reports have noted PCP among BT patients receiving corticosteroids, and suggested that these patients are particularly likely to develop PCP when corticosteroids are tapered. Nine BT patients, eight with high-grade gliomas, experienced ten episodes of PCP. None were known HIV-positive. All were on dexamethasone (DXM) at PCP onset, and had continuously been receiving it for 47-398 days (median 69). Daily DXM dose at PCP onset ranged from 1-16 mg (median 9). Five episodes occurred in patients receiving a stable DXM dose and five during DXM taper. Nine episodes occurred in patients receiving chemotherapy. All patients had absolute lymphopenia at PCP onset, ranging from 80-900 x 10(6) lymphocytes/l (median 222 x 10(6)/l, normal > 1000 x 10(6). Three episodes were fatal despite appropriate antibiotic therapy. Unlike others, we did not find that corticosteroid taper predisposed to developing PCP. As in HIV, PCP in BT patients appears related to lymphopenia, in these patients attributable to use and duration of corticosteroids and in some cases cytotoxic chemotherapy. Effective prophylaxis exists and should be considered for lymphopenic patients and those requiring DXM for > five weeks.

Hematopoietic growth factor (G-CSF or GM-CSF) after salvage chemotherapy in refractory or relapsed adult de novo acute leukemia

Nineteen adults with primary refractory or relapsed acute leukemia (12 ALL and 7 ANLL) were treated with an intensive salvage chemotherapy (intermediate-dose ara-C, intermediate-dose methotrexate, vindesine, cyclophosphamide, mitoxantrone and prednisolone) followed by a hematopoietic growth factor (HGF), either granulocyte colony-stimulating factor (5 micrograms/kg) or granulocyte-macrophage colony-stimulating factor (10 micrograms/kg). Both were given from the day after chemotherapy ended and until the neutrophil count rose above 1 X 10(9)/l for three consecutive days. Eleven patients (58%, 95% CI 33% to 82%) achieved complete remission, and 15 courses of salvage therapy were given to these complete responders. In a historical control group that did not receive HGF, 23 out of 38 patients (60%, 95% CI 44% to 77%) achieved complete remission, and 27 courses of therapy were delivered to complete responders. Treatment with a HGF accelerated the recovery of neutrophils to 0.5 X 10(9)/l significantly, shortening it from a mean of 28 to 22 days (p = .0002), with no effect on platelet recovery. There were no differences in the rates of documented and fatal infections, which were relatively high in both groups. In the patients with ANLL, there was no evidence that HGF accelerated leukemic regrowth. We conclude that HGF accelerates neutrophilic recovery following intensive salvage chemotherapy for acute leukemia, although no reduction in documented infections was found. Many factors, including the small patient sample, may have contributed to this latter finding.

Pneumocystis carinii pneumonia in patients without acquired immunodeficiency syndrome: associated illness and prior corticosteroid therapy

OBJECTIVE

To determine the clinical spectrum of immunosuppressive conditions and systemic corticosteroid therapy associated with the development of Pneumocystis carinii pneumonia in a consecutive series of patients without acquired immunodeficiency syndrome (AIDS).

DESIGN

We retrospectively analyzed a consecutive series of 116 patients without AIDS who were assessed at Mayo Medical Center for a first episode of P. carinii pneumonia between 1985 and 1991.

METHODS

Medical records were examined to determine underlying immunosuppressive disorders, premorbid corticosteroid dosage and duration of therapy, associated infections, and subsequent respiratory failure and in-hospital mortality.

RESULTS

Conditions associated with a first episode of P. carinii pneumonia were hematologic malignant disorders (30.2%), organ transplantation (25.0%), inflammatory disorders (22.4%), solid tumors (12.9%), and miscellaneous conditions (9.5%). Regardless of the associated underlying disease, corticosteroids had been administered systemically in 105 patients (90.5%) within 1 month before the diagnosis of P. carinii pneumonia. The median daily corticosteroid dose was equivalent to 30 mg of prednisone; however, 25% of patients had received as little as 16 mg of prednisone daily. The median duration of corticosteroid therapy was 12 weeks before the development of pneumonia; however, P. carinii pneumonia developed after 8 weeks or less of corticosteroid therapy in 25% of these patients. Respiratory failure occurred in 43%, and in-hospital mortality was 34% for patients with P. carinii pneumonia in conditions other than AIDS.

CONCLUSION

Although these results do not suggest that premorbid administration of corticosteroids is the only factor that contributes to the development of P. carinii pneumonia in these patients, they show that, in this large consecutive series, systemic corticosteroid therapy, even in moderate doses, was administered to most patients during the month preceding the onset of P. carinii pneumonia. Consideration should be given to instituting P. carinii prophylaxis (when not contra-indicated) in patients for whom prolonged systemic corticosteroid therapy is prescribed.

Immunodiagnostic assays

The immune system is a complex interactive network. Defects in its function can be characterized broadly as being the result of actual deficiencies in the network or misdirection of normal immunologic functions. The assays that are available to detect deficiencies in the immunologic network barely scrape the surface of the possibilities. These assays primarily evaluate humoral immune function, but undetected defects in innate and cellular immunity are sure to exist. Although assays of humoral immunity have allowed the characterization of a number of immunodeficiency syndromes in horses, closer evaluation of the equine immune system using newer assays described in this text, as well as future assays yet to be developed are sure to determine new syndromes. Assays of misdirected immunologic functions have been limited to detection of misdirected antibody responses, but the dependence of antibody production on help from T cells could reflect an underlying defect of cellular immunity. Similar to immunodeficiency syndromes, misdirected responses of the innate and adaptive arms of immunity are sure to occur but will only be detected by more diligent surveillance of diseased horses and application of new immunodiagnostic technologies.

[Pneumocystis carinii infection disclosing untreated systemic lupus erythematosus]

Pneumocystis carinii pneumonia (PCP) is a well known opportunistic infection in Systemic Lupus Erythematosus (SLE) patients with lymphopenia and treated with corticosteroid or cytotoxics agents. We report a new case of PCP in an untreated SLE with severe lymphopenia. We discuss the origin of lymphopenia in SLE, lymphopenia as a risk factor of Pneumocystis carinii infection, and safety precautions to take.

Bronchoscopic diagnosis of pneumonia

Lower respiratory tract infections are characterized by significant morbidity and mortality but also by a relative inability to establish a specific etiologic agent on clinical grounds alone. With the recognized shortcomings of expectorated or aspirated secretions toward establishing an etiologic diagnosis, clinicians have increasingly used bronchoscopy to obtain diagnostic samples. A variety of specimen types may be obtained, including bronchial washes or brushes, protected specimen brushings, bronchoalveolar lavage, and transbronchial biopsies. Bronchoscopy has been applied in three primary clinical settings, including the immunocompromised host, especially human immunodeficiency virus-infected and organ transplant patients; ventilator-associated pneumonia; and severe, nonresolving community- or hospital-acquired pneumonia in nonventilated patients. In each clinical setting, and for each specimen type, specific laboratory protocols are required to provide maximal information. These protocols should provide for the use of a variety of rapid microscopic and quantitative culture techniques and the use of a variety of specific stains and selective culture to detect unusual organism groups.

Transthoracic needle aspiration in the study of pulmonary infections in patients with HIV

STUDY OBJECTIVE

To evaluate the safety and efficacy of transthoracic aspiration with an ultrathin needle in the microbiologic diagnosis of pulmonary infections in HIV-infected patients.

DESIGN

Retrospective review of cases.

SETTING

A 500-bed teaching hospital in Lleida, Spain.

PATIENTS

Forty-five HIV-infected patients admitted between March 1989 and March 1993 with clinical and roentgenographic evidence of pulmonary infection and without contraindications for transthoracic needle aspiration (TNA).

INTERVENTIONS

Forty-seven TNAs were performed in the emergency room (20) or during hospitalization (27). The TNA procedures were done without premedication and without fluoroscopic guidance. Specimens were processed using routine microbiologic and cytologic techniques; in addition, polymerase chain reaction (PCR) for Pneumocystis carinii was carried out since March 1992. Development of adverse effects was carefully evaluated.

RESULTS

The TNA was effective in 29 (62 percent) out of 47 procedures. The diagnosis was obtained for 14 of 15 patients with P carinii pneumonia, 8 out of 14 patients with bacterial pneumonia, and 4 out of 12 patients with tuberculosis. Other pathogens recovered were Nocardia asteroides, Cryptococcus neoformans, Rhodococcus equi, and Mycobacterium avium. No false-positive results were obtained. Pneumothorax developed in eight (17 percent) procedures, but only one procedure resulted in a pleural drainage; the incidence of other adverse effects was low and clinically irrelevant.

CONCLUSION

Our study suggests that TNA can be a useful technique in establishing the etiologic diagnosis of pulmonary infections in HIV-infected patients, with a good sensitivity, high specificity, and relatively low incidence of serious complications, with TNA appearing as a reliable alternative to more uncomfortable methods.

Molecular characterization of clustered variants of genes encoding major surface antigens of human Pneumocystis carinii

A 13-kb genomic fragment from human Pneumocystis carinii was cloned as repetitive DNA. The fragment contains a cluster of three related genes, each 3 kb in size, and the 5' end of a fourth gene. The predicted polypeptide of the first gene in the cluster comprises 1,030 amino acid residues with a total molecular mass of 116 kDa. The gene's predicted amino acid sequence bears 32% identity to predicted sequences of recently described gene fragments of ferret P. carinii, which encode an immunodominant surface glycoprotein (gpA) (P. J. Haidaris, T. W. Wright, F. Gigliotti, and C. G. Haidaris, J. Infect. Dis. 166:1113-1123, 1992), and 36% identity to the predicted sequence of a rat P. carinii major surface glycoprotein gene (msg) (J. A. Kovacs, F. Powell, J. C. Edman, B. Lundgren, A. Martinez, B. Drew, and C. W. Angus, J. Biol. Chem. 268:6034-6040). DNA hybridization showed that sequences related to the cloned msg genes reside on at least 12 chromosomes of human P. carinii at various degrees of multiplicity and/or homology. Affinity-purified antibodies with specificity to a fusion protein made from the human P. carinii msgI gene recognized two bands on a Western immunoblot containing total human P. carinii protein; they also recognized fusion proteins derived from the other two genes of the cluster. Monoclonal antibodies with reactivity to Msg of human P. carinii recognized fusion proteins produced from two msg genes. Fusion proteins were also recognized by sera from healthy humans and from patients. The msg genes are candidates for the development of immunotherapy and subunit vaccines for the treatment and prevention of P. carinii pneumonia.

A novel in situ model to study Pneumocystis carinii adhesion to lung alveolar epithelial cells

Pneumocystis carinii, an extracellular parasite thriving in the lungs of immunosuppressed mammals, is a major cause of death in AIDS patients in the USA. As a prelude to growth, the parasite adheres mostly to type I pneumocytes lining the alveolar spaces. The mechanism of adherence remains unknown, largely because of difficulties in isolating type I pneumocytes and maintaining them in vitro. As a first step to understand P. carinii adherence to its natural substrate, we developed an in situ method to directly study parasite binding to lung alveolar cells. We used formaldehyde-fixed paraffin-embedded sections of normal rat lung as substrate for adhesion. As in its binding to the lungs in vivo, P. carinii adhered preferentially to type I pneumocytes. Adherence was saturable, time and dose dependent, and selectively blocked by glycoconjugates, in particular bovine submaxillary mucin, fetuin, and asialofetuin, suggesting that it may be mediated by a lectin type of interaction. Further, IgG of rats with P. carinii pneumonia inhibited adherence, suggesting that it may react with parasite ligands involved in the recognition of type I cell receptors. Our results demonstrate the usefulness of the in situ model for studying the mechanisms of P. carinii adherence to alveolar cells. In addition, this method may be valuable for identifying neutralizing antibodies and drugs potentially useful for controlling the infection in vivo.

Danish AIDS patients 1988-1993: a recent decline in Pneumocystis carinii pneumonia as AIDS-defining disease related to the period of known HIV positivity

The frequency of PCP among adult Danish AIDS patients notified in 1988-93 was higher among patients tested HIV-positive less than 4 months prior to AIDS than among those known to be positive for > 1 year. Among the latter, the proportion with PCP decreased significantly over the period, from 45.3% in 1988 to 22.0% in 1993, while no such trend was found among patients tested positive for HIV less than 4 months before AIDS was diagnosed. The incidence of PCP as an AIDS-defining disease has decreased, most likely due to the use of PCP prophylaxis.

DNA amplification by the polymerase chain reaction to detect sub-clinical Pneumocystis carinii colonization in HIV-positive and HIV-negative male homosexuals with and without respiratory symptoms

Pneumocystis carinii colonization was studied in 90 men using the polymerase chain reaction. These comprised ten heterosexual controls; ten HIV-seronegative homosexual controls; 20 HIV-seropositive homosexuals with blood CD4 count > 400 x 10(6) l-1; 20 HIV-seropositive homosexuals with CD4 < 400 x 10(6) l-1; ten HIV-seropositive homosexuals with CD4 < 60 x 10(6) l-1 receiving PCP chemoprophylaxis; and 20 HIV-seropositive homosexuals with respiratory symptoms but without PCP. Induced sputum was obtained from all but the last group, who had bronchoalveolar lavage, and all specimens were tested for P. carinii using the polymerase chain reaction. The first four groups received no pneumocystis chemoprophylaxis, and all but the last group were asymptomatic. P. carinii colonization did not occur in the two control groups. P. carinii colonization rates were significantly different in the CD4 > 400, CD4 < 400, and CD4 < 60 groups (10%, 20%, and 40% respectively) (P < 0.025). Two patients (one each from CD4 < 400 and CD4 < 60) developed PCP 4-6 weeks after sputum induction, both had previously had high levels of P. carinii on sputum induction. Two patients from the CD4 < 400 group had high levels of P. carinii but did not develop PCP. In the symptomatic group, two subjects had low levels of P. carinii, but did not develop PCP. We have demonstrated P. carinii colonization in HIV-seropositive homosexuals in association with a low peripheral CD4 count. The polymerase chain reaction may be a useful technique for determining the need and efficacy of anti-pneumocystis chemoprophylaxis.

Leukotriene B4 and interleukin-8 in human immunodeficiency virus-related pulmonary disease

STUDY OBJECTIVE

To investigate the pathogenesis of lung injury in Pneumocystic carinii pneumonia and nonspecific interstitial pneumonitis (NIP), common pulmonary complications of human immunodeficiency virus (HIV) infection. The efficacy of corticosteroid therapy in P carinii pneumonia and the observation that bronchoalveolar lavage (BAL) neutrophilia predicts a poor prognosis support the premise that the lung injury of P carinii pneumonia is due to the host's inflammatory response to the infection.

DESIGN

In vitro measurements on previously collected BAL fluid samples.

SETTING

The Clinical Center of the National Institutes of Health, a research hospital and tertiary care referral center.

PATIENTS

Five normal volunteers, 5 asymptomatic HIV-positive patients, 10 HIV-positive patients with NIP (5 asymptomatic and 5 with respiratory symptoms), and 19 HIV-positive patients with P carinii pneumonia.

MEASUREMENTS AND RESULTS

BAL leukotriene B4 (LTB4), interleukin 8 (IL-8), and phospholipase A2 (PLA2) were measured. IL-8 and PLA2 were elevated in patients with P carinii pneumonia, and IL-8 correlated with BAL fluid absolute neutrophil count. LTB4, IL-8, and PLA2 levels were elevated in patients with NIP; LTB4 and PLA2 levels correlated with absolute neutrophil count, and IL-8 correlated with alveolar-arterial oxygen pressure difference. IL-8 was elevated in the asymptomatic HIV-positive patients, and there was a trend toward elevation of PLA2 in this group.

CONCLUSION

IL-8 appears to play a role in the pathogenesis of lung injury in P carinii pneumonia and may be the principal neutrophil chemotaxin in this disease; PLA2 may also be involved in the pathogenesis of P carinii pneumonia. Both LTB4 and IL-8 may be involved in the recruitment of neutrophils and subsequent lung injury of NIP. These data suggest that there are varying mechanisms by which inflammatory cells are recruited to the lung in different HIV-related lung diseases.

Development and characterization of a rapid screening assay for identifying antipneumocystis agents

We developed a rapid assay for screening of compounds with potential antipneumocystis activity on the basis of incorporation of [35S]methionine into proteins newly synthesized by Pneumocystis carinii. Unambiguous evidence that P. carinii synthesizes proteins in vitro was provided by immunoprecipitation studies demonstrating the incorporation of [35S]methionine into the major surface glycoprotein. Treatment with two clinically active antipneumocystis agents, atovaquone (10(-4) M) or pentamidine (10(-4) M), prevented this incorporation. Total [35S]methionine incorporation paralleled incorporation into the major surface glycoprotein, permitting rapid assessment of anti-P. carinii activity by scintillation counting. Treatment with pentamidine (1 x 10(-4) M), atovaquone, trimethoprim (1 x 10(-4) M)-sulfamethoxazole (7.9 x 10(-4) M), piritrexim (1 x 10(-7) M), RO11-8958 (1 x 10(-4) M), and amphotericin B (1 microgram/ml) resulted in a greater than 67% inhibition (P < 0.05) of [35S]methionine incorporation. No decrease in [35S]methionine incorporation was seen with dapsone (10(-5) M), trimethoprim (10(-4) M), recombinant mouse tumor necrosis factor (500 ng/ml), or gamma interferon. This rapid in vitro assay should be a useful adjunct in the development of new antipneumocystis agents.

Diagnostic utility of lactate dehydrogenase levels in patients receiving aerosolized pentamidine

Serum lactate dehydrogenase (LDH) levels are elevated in patients with Pneumocystis carinii pneumonia (PCP). In patients receiving aerosolized pentamidine (AP), PCP may be less severe and present with more localized radiographic infiltrates. We evaluated the diagnostic utility of the serum LDH level in 11 patients developing PCP while receiving AP. Serum LDH levels were increased 72.7 +/- 19.0 percent over mean baseline levels and 76.4 +/- 26 percent over the upper limit of normal value for our laboratory with the development of PCP. An elevated serum LDH value remains a useful diagnostic adjunct in the patient developing PCP while receiving AP. Isolated LDH values must be interpreted with caution given the potential for marked variability in the baseline LDH value.

Serum titres of Pneumocystis carinii antibody in health care workers caring for patients with AIDS

BACKGROUND

Pneumocystis carinii pneumonia was thought to occur from reactivation of latent infection, but recent studies with the polymerase chain reaction have failed to detect P carinii in normal subjects. If pneumocystis pneumonia is therefore caused by new infection the source and mode of transmission of P carinii remains unknown.

METHODS

Natural exposure to P carinii was detected by measuring antibodies by indirect immunofluorescence in 24 health care workers working continuously with patients with AIDS and 24 control health care workers exclusively treating elderly patients.

RESULTS

P carinii antibody titres were significantly higher in the health care workers exposed to AIDS than in the control group (median titre 1:32 v 1:16 respectively). Three control subjects had no antibodies compared with none of the subjects exposed to AIDS, and 10 of the 12 highest titres came from the exposed group.

CONCLUSIONS

Raised P carinii antibody titres in health care workers caring for patients with AIDS suggest that patients infected with HIV may be a potentially infectious source of P carinii for susceptible subjects.

Cost effectiveness of noninvasive oxygen saturation measurement during exercise for the diagnosis of Pneumocystis carinii pneumonia

We assessed (1) the sensitivity and specificity of exercise oxygen saturation measurement (EOS) for the diagnosis of Pneumocystis carinii pneumonia (PCP); and (2) the cost of introducing this indirect diagnostic test compared with that of standard diagnostic strategies for PCP. In a prospective study, 85 HIV-infected patients with suspected PCP underwent EOS, followed by induced sputum (IS) and bronchoalveolar lavage (BAL) if IS was negative for P. carinii. The prevalence of PCP was 0.22, the sensitivity of IS was 0.6, and its specificity was perfect. The cost ratios of IS to BAL and EOS to BAL were 0.1 and 0.2, respectively. A desaturation of three points was the best cutoff point, giving perfect sensitivity and a specificity of 0.77. The cost analysis showed that the introduction of EOS into diagnostic strategies for PCP is highly justified when the local prevalence is low. Exercise oxygen saturation measurement is simple and safe, and the results are available rapidly; its sensitivity is perfect and its specificity good. Its economic utility depends on its cost and the local prevalence of PCP in the test population.

The diagnosis of Pneumocystis carinii pneumonia by cytologic evaluation of Papanicolaou and Leishman-stained bronchoalveolar specimens in patients with the acquired immunodeficiency syndrome

The presence of foamy alveolar casts or flocculent material in Papanicolaou and Leishman-stained smears of bronchoalveolar lavage (BAL) fluid is said to be indicative of infection with Pneumocystis carinii. We have investigated the sensitivity and specificity of this method of diagnosing pneumocystis pneumonia in patients with the acquired immunodeficiency syndrome (AIDS). Patients (n = 114) with diffuse lung infiltrates were submitted to fibreoptic bronchoscopy and BAL. Seventy of them were patients with AIDS. The other 44 individuals were not infected by the human immunodeficiency virus (HIV). Pneumocystis carinii organisms were identified on Grocott's methenamine silver (GMS)-stained BAL smears in 30 patients with AIDS. Flocculent material was present in the Papanicolaou and Leishman-stained smears from all of these cases. Conversely, P. carinii were not seen on GMS-stained smears in the remaining 84 individuals with or without AIDS. No flocculent material was observed in Papanicolaou or Leishman-stained smears in these 84 patients. We concluded that the presence of flocculent material in Papanicolaou or Leishman-stained smears of BAL fluid is indicative of P. carinii pneumonia in patients with AIDS.

In situ hybridization analysis of developmental stages of Pneumocystis carinii that are transcriptionally active for a major surface glycoprotein gene

An abundant glycoprotein on the surface of Pneumocystis carinii, termed gpA or gp120, is thought to play a role in the interaction of this opportunistic pathogen with its host. Using RNA:RNA hybridization techniques, the in situ expression of gpA mRNA in developmental forms of the organism was investigated in a ferret model of P. carinii pneumonia. The results suggested that the relative abundance of gpA-specific mRNA was variable in different developmental stages of ferret P. carinii. P. carinii localized along the epithelial lining of alveoli were transcriptionally active. Immunocytochemical detection of gpA and Giemsa staining suggested that many of these organisms were trophic forms of P. carinii. While no detectable gpA mRNA signal was found in the majority of P. carinii cysts, a portion of identifiable cysts co-localized with significant levels of gpA mRNA signal. Differential staining of the cyst wall with Gomori's methenamine silver suggested that the transcriptionally active P. carinii cysts were the intermediate or precyst forms of the organism, while the cysts with no detectable mRNA signal were either mature or empty (excysted). Alveolar macrophages were observed surrounded by transcriptionally active organisms; however, no gpA-transcriptional activity was detected within macrophages. Taken together, the results suggest that transcription of gpA occurs in forms of P. carinii that are actively replicating, and in close proximity or contact with, alveolar epithelial cells.

Quantitative and qualitative comparison of DNA amplification by PCR with immunofluorescence staining for diagnosis of Pneumocystis carinii pneumonia

AIM

To compare the results of DNA amplification by the polymerase chain reaction (PCR) with immunofluorescence staining for detecting Pneumocystis carinii in bronchoalveolar lavage specimens taken from symptomatic HIV seropositive patients with suspected P carinii pneumonia (PCP).

METHODS

Bronchoalveolar lavage specimens were obtained from 28 symptomatic HIV seropositive patients. Specimens were examined for P carinii using immunofluorescence, and by DNA amplification with PCR to obtain results on gel electrophoresis (gel) and a more sensitive Southern hybridisation (blot) technique. Specimens positive by immunofluorescence and gel electrophoresis were serially diluted to a 10(-6) concentration and each dilution strength tested for P carinii using PCR to compare quantitatively immunofluorescence with PCR.

RESULTS

Of the 28 specimens analysed, 18 were negative for P carinii by both immunofluorescence and PCR, two were positive only by the blot technique of PCR, four were equivocally positive and four unequivocally positive by immunofluorescence. Three of the four equivocally positive patients tested by immunofluorescence were negative for P carinii by PCR, although one was positive by PCR (blot) technique. This patient had clinically confirmed PCP. Of the four unequivocally positive patients tested by immunofluorescence, three were gel and blot positive by PCR and had PCP clinically, but one was negative by both gel and blot techniques, although the patient certainly had PCP on clinical grounds. This patient had received nine days of treatment with high dose co-trimoxazole before bronchoalveolar lavage specimens were obtained. The three specimens positive by gel and blot techniques remained gel positive down to dilutions of between 10(-4) and 10(-6).

CONCLUSIONS

PCR results may become negative soon after starting treatment for PCP. Specimens should therefore be taken before, or soon after, starting treatment. PCR seems to be between 10(4) and 10(6) times more sensitive than immunofluorescence.

Reduction of pulmonary surfactant in patients with human immunodeficiency virus infection and Pneumocystis carinii pneumonia

We assessed qualitative and quantitative differences in surfactant lipid composition of bronchoalveolar lavage (BAL) fluid in patients with acquired immune deficiency syndrome (AIDS) and Pneumocystis carinii (PC) pneumonia. Five normal volunteers and 27 patients with human immunodeficiency virus (HIV) infection underwent BAL for evaluation of possible pulmonary infection. Bronchoalveolar lavage studies in eight patients were negative for PC organisms, and 19 were positive. Pneumocystis carinii pneumonia was graded (mild vs moderate to severe) by initial alveolar-arterial oxygen gradient. Bronchoalveolar lavage fluid was centrifuged, the lipids were extracted from the supernatant, and total lipid profiles of dephosphorylated glycerolipids were analyzed as trimethylsilylether derivatives by high temperature gas-liquid chromatography. Phospholipase A2 levels were determined using a radiolabeled E coli membrane method. Compared to the normal volunteers (109 +/- 13 micrograms/5 ml) and the PC negative group (107 +/- 13 micrograms/5 ml), total BAL lipid was reduced for both the mild PC pneumonia group (73 +/- 10 micrograms/5 ml) and the moderate to severe PC pneumonia group (46 +/- 4 micrograms/5 ml). There was a parallel reduction of diacylglycerol lipids: normal volunteers, 52 +/- 7 micrograms/5 ml; PC negative, 52 +/- 9 micrograms/5 ml; mild PC pneumonia, 35 +/- 7 micrograms/5 ml; and moderate to severe PC pneumonia, 15 +/- 2 micrograms/5 ml. Phospholipase A2 activity in moderate to severe PC pneumonia was twice that of the PC negative patients, and 30 times that for normals. The data demonstrate a marked diminution in surfactant glycerophospholipid in patients with AIDS and PC pneumonia and suggest a potential role for surfactant abnormality in the pathophysiology of this disease.

Application of DNA amplification to pneumocystosis: presence of serum Pneumocystis carinii DNA during human and experimentally induced Pneumocystis carinii pneumonia

Pneumocystis carinii pneumonia is a leading cause of morbidity and mortality in patients with the acquired immunodeficiency syndrome (AIDS). Much remains unknown about the basic biology of P. carinii and studies of this infection have been hampered by the lack of cultivation methods. We developed a sensitive and specific assay for P. carinii by utilizing DNA amplification of the P. carinii dihydrofolate reductase (DHFR) gene. By this method, P. carinii DNA was detected in the lungs of rats with experimentally induced P. carinii pneumonia 2 wk before the onset of histopathological changes. DNA amplification analysis of serum demonstrated that by 10 wk of corticosteroid treatment, 12 of 12 (100%) infected rats had circulating DHFR DNA. P. carinii DHFR DNA also was detected in the serum of patients with AIDS and active P. carinii pneumonia (12 of 14 sera collected prospectively). Patients with advanced AIDS but without a history of P. carinii pneumonia were negative by this assay (0 of 6 sera examined). Serum polymerase chain reaction may facilitate investigations into the natural history and epidemiology of P. carinii infection, provide insight into the pathogenesis of parasite dissemination, and offer a useful, noninvasive diagnostic test for the detection of human pneumocystosis.

Fungus-specific translation elongation factor 3 gene present in Pneumocystis carinii

Historically, Pneumocystis carinii pneumonia has been the most frequent cause of morbidity and mortality in patients with AIDS. Antiprotozoan drugs are effective in the treatment and prophylaxis of P. carinii pneumonia, which lends credence to the widely held view that P. carinii is a protozoan. However, recent genetic evidence suggests that P. carinii should be classified as a fungus. Translation elongation factor 3 (EF-3) is an essential, soluble translation component which is unique to fungal protein synthesis and is not required for protein synthesis in other eukaryotes. We have identified and isolated a gene for EF-3 from P. carinii, adding more evidence for this organism's assignment as a fungus.

Adjuvant corticosteroid therapy for Pneumocystis carinii pneumonia in AIDS patients

OBJECTIVE

To review published abstracts, case reports, and journal articles and evaluate data examining the use of systemic corticosteroids as adjuvant treatment for Pneumocystis carinii pneumonia (PCP) in patients with AIDS.

DATA SOURCES

Computerized online databases, peer-reviewed journals from January 1986 through September 1991, and personal communication with a National Institutes of Health correspondent.

STUDY SELECTION

The authors identified 13 reports pertinent to this review. By author consensus, five studies were selected for analysis based on sample size, controlled study design, and clinical outcome measures. Recommendations of an expert panel from the National Institutes of Health and the University of California also are discussed.

DATA EXTRACTION

Data are presented based on the methodologic strength of the studies reviewed. Studies are assessed on sample size, inclusion criteria, comparative cohort populations, specific patient outcome measures, and statistical analysis.

DATA SYNTHESIS

Results of the study analysis support the use of systemic corticosteroids as early adjunctive therapy for AIDS patients with moderate-to-severe PCP who have an initial arterial oxygen partial pressure of less than 70 mm Hg or an alveolar-arterial gradient greater than 35 mm Hg on room air. Improved outcomes included decreased mortality, respiratory failure, and deterioration of oxygenation. Data evaluated have shown that adjuvant corticosteroid therapy is most effective when initiated within 72 hours of beginning specific antipneumocystis therapy. A small, but sometimes significant, increased rate of infection in steroid-treated patients was noted.

CONCLUSIONS

Based on the literature reviewed, early systemic adjuvant corticosteroid therapy can benefit patients with moderate-to-severe AIDS-related PCP. The steroid regimen used in the largest controlled trial and recommended by the expert panel is prednisone 40 mg bid (days 1-5), then 40 mg/d (days 6-10), then 20 mg/d (days 1-21).

Pneumocystis carinii pneumonia after 40 years

Forty years ago, Pneumocystis carinii was identified by Czech researchers J. Vanĕk and O. Jírovec as the causative agent of interstitial plasma cell pneumonia in infants. At present, it is the commonest pulmonary pathogen in AIDS patients. This review summarizes the experience and latest data on the etiopathogenesis, pathology, clinical presentation, diagnosis and therapy of P. carinii pneumonia.

Pentamidine blocks the pathophysiologic effects of endotoxemia through inhibition of cytokine release

Pentamidine isethionate, an antiprotozoal agent with therapeutic value against Pneumocystis carinii pneumonia, has been used for over 30 years without a precise understanding of its mechanism of pharmacologic action. We have previously reported that pentamidine has the capacity to inhibit the release of cytokines from macrophages through a post-translational processing event. The present studies were undertaken to assess the ability of pentamidine to modulate the detrimental effects of murine endotoxemia, a disease with a pathophysiology clearly linked to host-produced cytokines. Under conditions where normal B6C3F1 mice succumbed to the lethal effects of endotoxin, mice pretreated with pentamidine were significantly protected from both mortality and loss of thermoregulatory control. The EC50 for protection from mortality by pentamidine was approximately 11.4 mg/kg. These observations correlated with decreased serum levels of tumor necrosis factor (TNF) and interleukin 6. Inhibition of cytokines was not manifested as part of a generalized inhibition of protein synthesis as demonstrated by the lack of significant modulation of serum albumin in pentamidine-treated animals. In addition to decreased serum concentrations of cytokines, lungs isolated from mice treated with both pentamidine and endotoxin exhibited a decreased release of TNF compared to lungs isolated from mice treated with vehicle and endotoxin. The lower levels of TNF released from lung tissue in pentamidine-treated mice correlated with a lesser degree of alveolar deterioration than was observed in vehicle-treated mice. These data indicate that following endotoxin administration, pentamidine has a protective and antiinflammatory role both systemically and in the lung and suggest that inhibition of inflammatory cytokines may be one mechanism operable in the therapeutic activity of the drug against P carinii pneumonia.