Deciphering Antifungal Drug Resistance in Pneumocystis jirovecii DHFR with Molecular Dynamics and Machine Learning

Drug resistance impacts the effectiveness of many new therapeutics. Mutations in the therapeutic target confer resistance; however, deciphering which mutations, often remote from the enzyme active site, drive resistance is challenging. In a series of Pneumocystis jirovecii dihydrofolate reductase variants, we elucidate which interactions are key bellwethers to confer resistance to trimethoprim using homology modeling, molecular dynamics, and machine learning. Six molecular features involving mainly residues that did not vary were the best indicators of resistance.

Primary prophylaxis of bacterial infections and Pneumocystis jirovecii pneumonia in patients with hematologic malignancies and solid tumors: 2020 updated guidelines of the Infectious Diseases Working Party of the German Society of Hematology and Medical Oncology (AGIHO/DGHO)

Hematologic and oncologic patients with chemo- or immunotherapy-related immunosuppression are at substantial risk for bacterial infections and Pneumocystis jirovecii pneumonia (PcP). As bacterial resistances are increasing worldwide and new research reshapes our understanding of the interactions between the human host and bacterial commensals, administration of antibacterial prophylaxis has become a matter of discussion. This guideline constitutes an update of the 2013 published guideline of the Infectious Diseases Working Party (AGIHO) of the German Society for Hematology and Medical Oncology (DGHO). It gives an overview about current strategies for antibacterial prophylaxis in cancer patients while taking into account the impact of antibacterial prophylaxis on the human microbiome and resistance development. Current literature published from January 2012 to August 2020 was searched and evidence-based recommendations were developed by an expert panel. All recommendations were discussed and approved in a consensus conference of the AGIHO prior to publication. As a result, we present a comprehensive update and extension of our guideline for antibacterial and PcP prophylaxis in cancer patients.

Characterization of Pneumocystis jirovecii pneumonia at three tertiary comprehensive hospitals in southern China

Due to the increasing use of immunosuppressant therapy, Pneumocystis jirovecii pneumonia (PJP) has become an emerging concern in human immunodeficiency virus (HIV)-negative patients. In this study, we conducted a retrospective study of 96 hospitalized patients with PJP from January 2015 to June 2019 at three tertiary comprehensive hospitals in Southern China. Information was collected regarding patient demographics, clinical manifestations, risk factors, laboratory analyses, radiological images, and treatment outcomes. PJP infection was most commonly found in middle-aged men. Kidney diseases (35.5%) and connective tissue diseases (38.7%) were the predominant risk factors for PJP. About half of the patients (48.4%) received glucocorticoid, immunosuppressant, and/or chemotherapy in a low dose or in a short-term (< 3 months). None of the patients had previously received trimethoprim-sulfamethoxazole (TMP-SMX) for PJP prophylaxis. All patients had two or more clinical manifestations (cough, dyspnea, fever, and chest pain). Biochemical investigations of CRP, ESR, PaO2, LDH, and KL-6 showed that over 90% of the patients exceeded the reference range of indicators. Our analyses revealed the dominant risk factors (HIV, kidney diseases, and connective tissue diseases) and the most consistent biochemical indicators (LDH, BG, and KL-6) for PJP. Moreover, early prophylaxis, diagnosis, and treatment should contribute to improve the survival of these PJP patients.

Pneumocystis jirovecii Pneumonia in Patients With Metastatic Prostate Cancer on Corticosteroids for Malignant Spinal Cord Compression: Two Case Reports and a Guideline Review

Pneumocystis jirovecii, formerly known as Pneumocystis carinii, is an atypical fungal pathogen best known for causing Pneumocystis jirovecii pneumonia (PCP). The epidemiology of PCP is changing such that patients without HIV infection now comprise the largest subset of individuals diagnosed with PCP. While those with hematologic malignancies and organ transplants are at greatest risk for non-HIV-related PCP, this review will focus on PCP in patients with solid tumors. They are at risk for PCP due to their chemotherapy regimens and use of steroids in the management of various complications of treatment, and possibly because of the immunosuppressive effect of the cancer itself. In particular, patients with solid tumors being treated for metastatic spinal cord compression are at great risk for PCP. Patients with solid tumors and PCP face greater mortality than those with HIV infection. Multiple reviews have attempted to describe the ideal regimen of corticosteroids for metastatic spinal cord compression, but there is little consensus. We present 2 cases of patients with metastatic spinal cord compression due to prostate cancer undergoing radiation therapy and treatment with corticosteroids. These cases highlight the difficulties in predicting the length of corticosteroid therapy and the dangers that patients face without appropriate prophylaxis. This article will also provide a review of the current guidelines for PCP prophylaxis in patients undergoing treatment for metastatic spinal cord compression. We recommend empiric treatment with trimethoprim-sulfamethoxazole or dapsone in those patients with a sulfa allergy in all patients with solid tumors when any high-dose steroids are started for the treatment of metastatic spinal cord compression. Further research is needed to assess the epidemiology of PCP in patients with solid tumors and additional trials are necessary to refine PCP prophylaxis.

SYTO-13, a Viability Marker as a New Tool to Monitor In Vitro Pharmacodynamic Parameters of Anti-Pneumocystis Drugs

While Pneumocystis pneumonia (PcP) still impacts the AIDS patients, it has a growing importance in immunosuppressed HIV-negative patients. To determine the anti-Pneumocystis therapeutic efficacy of new compounds, animal and in vitro models have been developed. Indeed, well-designed mouse or rat experimental models of pneumocystosis can be used to describe the in vivo anti-Pneumocystis activity of new drugs. In vitro models, which enable the screening of a large panel of new molecules, have been developed using axenic cultures or co-culture with feeder cells; but no universally accepted standard method is currently available to evaluate anti-Pneumocystis molecules in vitro. Thus, we chose to explore the use of the SYTO-13 dye, as a new indicator of Pneumocystis viability. In the present work, we established the experimental conditions to define the in vitro pharmacodynamic parameters (EC50, Emax) of marketed compounds (trimethoprim/sulfamethoxazole, pentamidine, atovaquone) in order to specifically measure the intrinsic activity of these anti-P. carinii molecules using the SYTO-13 dye for the first time. Co-labelling the fungal organisms with anti-P. carinii specific antibodies enabled the measurement of viability of Pneumocystis organisms while excluding host debris from the analysis. Moreover, contrary to microscopic observation, large numbers of fungal cells can be analyzed by flow cytometry, thus increasing statistical significance and avoiding misreading during fastidious quantitation of stained organisms. In conclusion, the SYTO-13 dye allowed us to show a reproducible dose/effect relationship for the tested anti-Pneumocystis drugs.

Clinical applications of pulmonary delivery of antibiotics

The treatment of infection typically involves administration of antibiotics by a systemic route, such as intravenous or oral. However, pulmonary infections can also be approached by inhalation of antibiotics as the infection is more directly accessible via the airways, making inhalation delivery essentially topical administration. This approach offers deposition of high antimicrobial concentrations directly at the site of infection but with a potentially reduced systemic exposure. This review covers the evidence for aerosolized antibiotics for the treatment of a number of conditions such as cystic fibrosis (CF), where it has become the standard of care for chronic infection, as well as non-CF bronchiectasis, non-tuberculous mycobacteria, and ventilator-associated infection where such therapy does not have an approved indication but has been used with increasing frequency.

Echinocandins--new antifungal agents

Over the past 10-15 years, the number of clinically available antifungal agents has increased substantially, due to rise in the number of invasive fungal infections, which are a real problem for specialists. Echinocandins are the new class of antifungal agents available for clinical use. This class comprises over 20 natural echinocandins and several semisynthetic ones. Natural echinocandins are not of clinical utility due to their toxicity and low water-solubility (which does not allow obtaining parenteral pharmaceutical forms), although they have good antifungal activity against Candida species. Consequently, semisynthetic echinocandins with minimal toxicity, good antifungal activity and high water-solubility were obtained. All echinocandins inhibit beta-1,3-glucan-synthase, an essential component of the fungal cell wall. Echinocandins exhibit potent antifungal activity against key pathogenic fungi, including Candida species, Aspergillus species and Pneumocystis carinii. The available echinocandins lack in vitro activity against Cryptococcus neoformans. The semisynthetic echinocandins have great advantages, among which low toxicity, fast antifungal activity, favorable pharmacokinetics that allow once-daily administration. The echinocandins recently available for clinical use are: caspofungin, micafungin and anidulafungin.

Post-diagnostic kinetics of the (1 → 3)-β-D-glucan assay in invasive aspergillosis, invasive candidiasis and Pneumocystis jirovecii pneumonia

The kinetics of serum (1 → 3)-β-d-glucan (BG) following the diagnosis of invasive fungal disease and administration of antifungal therapy are poorly characterized. It is unknown whether early BG changes have prognostic implications. We assessed the post-diagnostic kinetics of BG in patients with an initial serum BG ≥80 pg/mL and at least one additional post-diagnostic BG value in the setting of invasive aspergillosis (IA, n=69), invasive candidiasis (IC, n=40), or Pneumocystis jirovecii pneumonia (PCP, n = 18), treated with antifungal therapy. Clinical failure of antifungal therapy and mortality were assessed at 6 and 12 weeks, and Cox modelling was used to assess the hazard of initial BG and change in BG at 1 or 2 weeks for these outcomes. In patients with at least two BG values, median initial BG was >500 pg/mL (interquartile range (IQR) 168 to >500; range 80 to >500) in IA, 136 pg/mL (IQR 88 to >500; range 31 to >500) in IC and >500 pg/mL (IQR 235 to >500; range 86 to >500) in PCP. In patients with at least two BG values through to 1 week after diagnosis, overall 1-week decline in BG was 0 pg/mL (IQR 0-53) in IA, 0 (IQR - 65 to 12) in IC and 17 (IQR 0-82) in PCP. Most patients with BG values through 6 and 12 weeks had persistent levels >80 pg/mL. Initial BG and the early trajectory of BG were not predictive of 6-week or 12-week clinical failure or mortality. Whereas BG eventually declines in patients with IA, IC and PCP, it lacks prognostic value within a clinically meaningful time frame.

Cost-effectiveness analysis of diagnostic options for pneumocystis pneumonia (PCP)

Background

Diagnosis of Pneumocystis jirovecii pneumonia (PCP) is challenging, particularly in developing countries. Highly sensitive diagnostic methods are costly, while less expensive methods often lack sensitivity or specificity. Cost-effectiveness comparisons of the various diagnostic options have not been presented.

Methods and Findings

We compared cost-effectiveness, as measured by cost per life-years gained and proportion of patients successfully diagnosed and treated, of 33 PCP diagnostic options, involving combinations of specimen collection methods [oral washes, induced and expectorated sputum, and bronchoalveolar lavage (BAL)] and laboratory diagnostic procedures [various staining procedures or polymerase chain reactions (PCR)], or clinical diagnosis with chest x-ray alone. Our analyses were conducted from the perspective of the government payer among ambulatory, HIV-infected patients with symptoms of pneumonia presenting to HIV clinics and hospitals in South Africa. Costing data were obtained from the National Institutes of Communicable Diseases in South Africa. At 50% disease prevalence, diagnostic procedures involving expectorated sputum with any PCR method, or induced sputum with nested or real-time PCR, were all highly cost-effective, successfully treating 77–90% of patients at $26–51 per life-year gained. Procedures using BAL specimens were significantly more expensive without added benefit, successfully treating 68–90% of patients at costs of $189–232 per life-year gained. A relatively cost-effective diagnostic procedure that did not require PCR was Toluidine Blue O staining of induced sputum ($25 per life-year gained, successfully treating 68% of patients). Diagnosis using chest x-rays alone resulted in successful treatment of 77% of patients, though cost-effectiveness was reduced ($109 per life-year gained) compared with several molecular diagnostic options.

Conclusions

For diagnosis of PCP, use of PCR technologies, when combined with less-invasive patient specimens such as expectorated or induced sputum, represent more cost-effective options than any diagnostic procedure using BAL, or chest x-ray alone.

Pneumocystosis: a network survey in the Paris area 2003-2008

The aims of this network group were to collect epidemiological data of PcP cases in 14 hospitals in the Paris area and to determine the Di-Hydro Pteroate Synthase (DHPS) genotypes, genetic markers for possible sulfamide resistance. From January 1, 2003 to December 31, 2008, 993 (mean 166/year) PcP cases have been reported. Sixty-five percent of patients were HIV-positive. The median count of CD4 lymphocytes was 32/mm(3) (30 in HIV-positive patients, 152 in HIV-negative patients). In HIV-positive patients, PcP revealed the HIV infection in 39%. Among 304 PcP occurring in HIV known infected patients, no prophylaxis was prescribed for 64%; cotrimoxazole prophylaxis had been prescribed to 47 patients but only one of them had the right compliance. In HIV-negative patients (264), corticosteroids were prescribed in 59% and cytotoxic chemotherapies in 34%; 78% did not receive prophylaxis. One hundred sixty nine tumoral pathologies and 116 transplantations were notified. The mortality rate was 16% at day 14 (13% in HIV-positive patients, 26% in HIV-negative patients). Mutations in DHPS genes were detected in 18.5% of samples; 12.5% of patients were infected with several strains. The total annual number of cases has been stable for five years but the proportion of HIV-negative patients increased from 25% to 43%.

Sterol biosynthesis and sterol uptake in the fungal pathogen Pneumocystis carinii

Members of the fungal genus Pneumocystis colonize healthy mammalian hosts without causing apparent disease, but colonization in immunocompromised hosts may result in a potentially fatal pneumonia known as Pneumocystis pneumonia. Although Pneumocystis are fungi, this genus has characteristics that make it atypical among other fungi. Pneumocystis do not appear to synthesize the major fungal sterol, ergosterol, and biochemical analyses have shown that they utilize cholesterol rather than ergosterol as the bulk sterol. Pneumocystis carinii appears to scavenge exogenous sterols, including cholesterol, from its mammalian host. As a result, it has long been held that their ability to scavenge cholesterol from their hosts, and their inability to undergo sterol biosynthesis, makes them resistant to antifungal drugs that target ergosterol or ergosterol biosynthesis. However, genome scans and in vitro assays indicate the presence of sterol biosynthetic genes within the P. carinii genome, and targeted inhibition of these enzymes resulted in reduced viability of P. carinii, suggesting that these enzymes are functional within the organism. Heterologous expression of P. carinii sterol genes, along with biochemical analyses of the lipid content of P. carinii cellular membranes, have provided an insight into sterol biosynthesis and the sterol-scavenging mechanisms used by these fungi.

Antifungal and cytotoxic activity of withanolides from Acnistus arborescens

Three compounds were isolated from Acnistus arborescens, a tree commonly used in South and Central America in traditional medicine against several infectious diseases, some of which are caused by fungi. Bioassay-guided fractionation of a MeOH extract of leaves, based on its anti-Pneumocystis carinii activity, led to the isolation of compounds 1-3. Mono- and bidimensional NMR analyses enabled identification of two new withanolides, (20R,22R)-5beta,6beta-epoxy-4beta,12beta,20-trihydroxy-1-oxowith-2-en-24-enolide (1) and (20R,22R)-16beta-acetoxy-3beta,4beta;5beta,6beta-diepoxy-12beta,20-dihydroxy-1-oxowith-24-enolide (2), and withanolide D (3). Antifungal activity on 13 fungi responsible for human infections (five dermatophytes, one nondermatophyte mold, six yeasts, and Pneumocystis carinii) was examined. Cytotoxicity of these compounds was also evaluated in vitro.

Bisbenzamidines as antifungal agents. are both amidine functions required to observe an anti-Pneumocystis carinii activity?

A library of 19 novel 4-(4-phenylpiperazine-1-yl)benzamidines has been synthesized and evaluated in vitro against Pneumocystis carinii. Among these compounds, N-ethyl- and N-hexyl-4-(4-phenylpiperazine-1-yl)benzamidines emerged as the most promising compounds, with inhibition percentages at 10.0 µg/mL of 87% and 96%, respectively. Those compounds remained active at 0.1 µg/mL.

Imidazoquines as antimalarial and antipneumocystis agents

Peptidomimetic imidazolidin-4-one derivatives of primaquine (imidazoquines) recently displayed in vitro activity against blood schizonts of a chloroquine-resistant strain of Plasmodium falciparum. Preliminary studies with a subset of such imidazoquines showed them to both block transmission of P. berghei malaria from mouse to mosquito and be highly stable toward hydrolysis at physiological conditions. This prompted us to have deeper insight into the activity of imidazoquines against both Plasmodia and Pneumocystis carinii, on which primaquine is also active. Full assessment of the in vivo transmission-blocking activity of imidazoquines, in vitro tissue-schizontocidal activity on P. berghei-infected hepatocytes, and in vitro anti-P. carinii activity is now reported. All compounds were active in these biological assays, with generally lower activity than the parent drug. However, imidazoquines' stability against both oxidative deamination and proteolytic degradation suggest that they will probably have higher oral bioavailability and lower hematotoxicity than primaquine, which might translate into higher therapeutic indexes.

[Effects of Fructus Psoralea and Brucea javanica on the level of IL-2 and NK cell in rats infected with Pneumocystis carinii]

SD rat model of PCP was established by subcutaneous injection with dexamethasone. The treatment groups received Fructus Psoralea (FP, 10.0 mg/kg), Brucea javanica (BJ, 1.2 mg/kg) and a mixture of the two Chinese herbs(FP 5mg/kg, BJ 0.6 mg/kg) respectively. By means of detecting the level of IL-2 in sera and NK cells in spleens, the effect of FP and BJ on the level of IL-2 and NK cells in rats with Pneumocystis carinii pneumonia (PCP) was observed, with SMZco treatment group (TMP 50 mg/kg, SMZ 250 mg/kg) and groups of infected and normal rats as controls. Compared with the infected group, the level of IL-2(526.1 +/- 5.5) pg/ml and NK cells (27.1% +/- 0.8%) significantly increased in the FP group (P < 0.01), followed by the FP/BJ combination group [(314.7 +/- 6.7) pg/ml, 22.9% +/- 0.9%) (P < 0.05)], and BJ group [(285.4 +/- 6.1) pg/ml, 20.7% +/- l.0%) (P < 0.05)]. Chinese herbs Fructus Psoralea and Brucea javanica show an immune regulatory action on the PCP rats.

[Enzyme change in bronchoalveolar lavage fluid of pneumocystis pneumonia rats and the effect of garlicin treatment]

OBJECTIVE

To study the change of enzymes and effect of garlicin treatment on the change in bronchoalveolar lavage fluid (BALF) of rats with Pneumocystis carinii pneumonia (PCP).

METHODS

Wistar rats were injected intramuscularly continually with dexamethasone to establish the rat model of PCP. The experimental rats (group A) were injected intramuscularly with garlicin at a dose of 10 mg/(kg x d) for 5 days in the 3rd, 6th and 9th week respectively, and SMZ/TMP therapy group (B), PCP infected group (C) and normal group (D) were established as controls. Three days after the last treatment, the rats of all groups were killed and BALF was collected without contamination and enzymes AST, ALF, CHE, ALP, LDH, CK, CKMB, HBDH, AFU, 5'NT, ADA were examined.

RESULTS

The ALP level in group C [(573.41 +/- 350.63)U/L] was significantly higher than that in group D [(210.56 +/- 114.41) U/L] (q = 4.682, P < 0.01), group A [(392.07 +/- 217.57) U/L] (q = 3.851, P < 0.05), and group B [(325.21 +/- 180.65) U/L] (q = 4.380, P < 0.01); the level of CK, CKMB and 5'NT in group C [948.94 +/- 403.43, 489.47 +/- 254.46 and (6.76 +/- 3.11) U/L respectively] was higher than those in group D [426.22 +/- 319.00, 213.33 +/- 144.54 and (3.22 +/- 1.20) U/L] (q = 4.696, 3.784, 3.812, P< 0.05); there was no significant difference in the level of AST, ALT, CHE, LDH, HBDH, AFU and ADA among the four groups (F = 1.852, 0.958, 2.470, 1.423, 1.178, 1.342, 0.611, P > 0.05).

CONCLUSIONS

The level of ALP, CK, CKMB but the ALP level decreases distinctly after the garlicin and 5'NT increases evidently in BALF of PCP infected rats, but the ALP level decreases distinctly after the garlicin treatment.

Carbamate prodrugs of N-alkylfuramidines

The synthesis and evaluation of 2,5-bis[4-(N-ethoxycarbonyl-N'-isopropyl)amidinophenyl]furan, 2,5-bis[4-(N-2,2,2-trichloroethoxycarbonyl-N'-isopropyl)amidinophenyl]furan and 2,5-bis[4-(N-cyclopentyl-N'-2,2,2-trichloroethoxycarbonyl)amidinophenyl]furan as prodrugs of bis-N-alkylamidines are reported. The results show that the bis-2,2,2-trichloroethyl carbamates function effectively in a rat model for Pneumocystis pneumonia.

[Study on the changes of soluble intercellular adhesion molecule-1 level in sera of rats infected with Pneumocystis carinii]

OBJECTIVES

To examine sICAM-1 in Pneumocystis carinii pneumonia (PCP) and the effect of TMP-SMZ therapy on its level and on pathological and immunological changes in rats.

METHODS

50 female Wistar rats were randomly divided into normal group (N group), PCP model group (PCP group) and TMP-SMZ therapy group (SMZ group). 1 mg of dexamethasone was injected intramuscularly twice a week for rats in PCP and SMZ groups to induce PCP. Normal saline was injected for N group in the same way. When the infection was confirmed, TMP-SMZ was given to rats in SMZ group by 25 mg/(kg.d) for 5 days for 3 courses with an interval of 2 weeks. sICAM-1 in serum was detected by ELISA, and the pathological changes in lungs and liver and the Pc in alveoli of lungs were observed.

RESULTS

The level of sICAM-1 in PCP and SMZ groups at the 3rd week [(1.847+/-0.50) ng/ml, (1.787+/-0.59) ng/ml] was lower notably than that at 0 week [(2.407+/-0.81) ng/ml, [(2.478+/-0.59) ng/ml respectively] (P<0.05), and then increased gradually. It was significantly higher in PCP group at 9th week [(3.233+/-0.83) ng/ml] and at 12th week [(3.984+/-0.87) ng/ml] than that of 0 week (P<0.05). Its level in SMZ group at 12th week [(3.621+/-l.62) ng/ml] was also higher than that in 0 week [(2.478+/-0.59) ng/ml] (P<0.05). sICAM-1 level in both PCP and SMZ groups at 9th week and 12th week was higher than that of N group (P<0.05, P<0.01). There was no significant difference between SMZ and PCP groups at 9th week and 12th week (P>0.05).

CONCLUSION

The sICAM-1 level in rats was low but significantly increases after the induction of PCP.

Inhibitory Effect of Umbelliferone Aminoalkyl Derivatives on Oxidosqualene Cyclases fromS. cerevisiae,T. cruzi,P. carinii,H. sapiens, andA. thaliana: a Structure–Activity Study

Eighteen coumarin derivatives were tested as inhibitors of oxidosqualene cyclases (OSCs) from Saccharomyces cerevisiae, Trypanosoma cruzi, Pneumocystis carinii, Homo sapiens, and Arabidopsis thaliana, all expressed in an OSC-defective strain of S. cerevisiae.35 All the compounds have an aminoalkyl chain bound to an aromatic nucleus; unconventional synthetic procedures (microwave- and ultrasound-promoted reactions) were successfully used to prepare some of them. The most interesting structure-dependent difference in inhibitory activities was observed with an N-oxide group replacement of the tertiary amino group at the end of the side chain. An interesting species specificity also emerged: T. cruzi OSC was the least sensitive enzyme; P. carinii and A. thaliana OSCs were the most sensitive. The remarkable activities of three compounds on the T. cruzi enzyme and of five of them on the P. carinii enzyme suggest the present series as a promising compound family for the development of novel antiparasitic agents.

An Official ATS Workshop Summary: Recent advances and future directions in pneumocystis pneumonia (PCP)

Pneumocystis pneumonia (PCP) is a major cause of morbidity and mortality among immunocompromised persons, and it remains a leading acquired immune deficiency syndrome (AIDS)-defining opportunistic infection in human immunodeficiency virus (HIV)-infected individuals throughout the world. Pneumocystis has proven difficult to study, in part due to the lack of a reliable culture system for the organism. With the development of molecular techniques, significant advances in our understanding of the organism and the disease have been made over the past several years. These advances include an improved understanding of host-organism interactions and host defense, the development of noninvasive polymerase chain reaction (PCR)-based diagnostic assays, and the emerging data regarding the possible development of trimethoprim-sulfamethoxazole-resistant Pneumocystis. In addition, the recognition that patients without PCP may nevertheless be carriers of or colonized with Pneumocystis, and observations that suggest a role for Pneumocystis in the progression of pulmonary disease, combine to signal the need for a comprehensive and accessible review. In May 2005, the American Thoracic Society sponsored a one-day workshop, "Recent Advances and Future Directions in Pneumocystis Pneumonia (PCP)," which brought together 45 Pneumocystis researchers. The workshop included 21 presentations on diverse topics, which are summarized in this report. The workshop participants identified priorities for future research, which are summarized in this document.

Novel non-classical C9-methyl-5-substituted-2,4-diaminopyrrolo[2,3-d]pyrimidines as potential inhibitors of dihydrofolate reductase and as anti-opportunistic agents

Six novel C9-methyl-5-substituted-2,4-diaminopyrrolo[2,3-d]pyrimidines 18-23 were synthesized as potential inhibitors of dihydrofolate reductase (DHFR) and as anti-opportunistic agents. These compounds represent the only examples of 9-methyl substitution in the carbon-carbon bridge of 2,4-diaminopyrrolo[2,3-d]pyrimidines. The analogs 18-23 were synthesized in a concise eight-step procedure starting from the appropriate commercially available aromatic methyl ketones. The key step involved a Michael addition reaction of 2,4,6-triaminopyrimidine to the appropriate 1-nitroalkene, followed by ring closure of the nitro adducts via a Nef reaction. The compounds were evaluated as inhibitors of DHFR from Pneumocystis carinii (pc), Toxoplasma gondii (tg), Mycobacterium avium (ma) and rat liver (rl). The biological result indicated that some of these analogs are potent inhibitors of DHFR and some have selectivity for pathogen DHFR. Compound 23 was a two digit nanomolar inhibitor of tgDHFR with 9.6-fold selectivity for tgDHFR.

Absence of dihydropteroate synthase mutations in Pneumocystis jirovecii from Brazilian AIDS patients

Several studies from developed countries have documented the association between trimethoprim-sulfamethoxazole prophylaxis failure and mutations in the Pneumocystis jirovecii gene coding for dihydropteroate synthase (DHPS). DNA was extracted from Giemsa-stained smears of 70 patients with P. jirovecii pneumonia seen in Porto Alegre, Brazil, from 1997 to 2004. Successful PCR amplification of the DHPS locus was obtained in 57 of 70 cases (81.4%), including five cases (8.7%) that had used sulfa prophylaxis. No DHPS gene mutations were seen. These results suggest that DHPS mutations are currently as rare in Brazil as in other developing countries.

In vitro selection and in vivo efficacy of piperazine- and alkanediamide-linked bisbenzamidines against Pneumocystis pneumonia in mice

Bisbenzamidines, such as pentamidine isethionate, are aromatic dicationic compounds that are active against Pneumocystis and other microbes but are oftentimes toxic to the host. To identify potential anti-Pneumocystis agents, we synthesized bisbenzamidine derivatives in which the parent compound pentamidine was modified by a 1,4-piperazinediyl, alkanediamide, or 1,3-phenylenediamide moiety as the central linker. Several of the compounds were more active against P. carinii and less toxic than pentamidine in cytotoxicity assays. For this study, we evaluated nine bisbenzamidine derivatives representing a range of in vitro activities, from highly active to inactive, for the treatment of pneumocystosis in an immunosuppressed mouse model. Six of these in vitro-active compounds, 01, 02, 04, 06, 100, and 101, exhibited marked efficacies against infection at a dose of 10 mg/kg of body weight, and four compounds, 01, 04, 100, and 101, showed significant increases in survival versus that of untreated infected control mice. Compound 100 was highly efficacious against the infection at 20 mg/kg and 40 mg/kg, with > 1,000-fold reductions in burden, and resulted in improved survival curves versus those for pentamidine-treated mice (at the same doses). All six bisbenzamidine compounds that exhibited high in vitro activity significantly decreased the infection in vivo; two compounds, 12 and 102, with marked to moderate in vitro activities had slight or no activity in vivo, while compound 31 was inactive in vitro and was also inactive in vivo. Thus, the selection of highly active compounds from in vitro cytotoxicity assays was predictive of activity in the mouse model of Pneumocystis pneumonia. We conclude that a number of these bisbenzamidine compounds, especially compound 100, may show promise as new anti-Pneumocystis drugs.

Oral trimethoprim-sulphamethoxazole levels in stable HIV-infected children

BACKGROUND

Effective treatment of Pneumocystis jiroveci pneumonia (PCP) requires therapeutic serum concentrations of 5-10 microg/ml trimethoprim (TMP); consequently intravenous trimethoprim-sulphamethoxazole (TMP-SMZ) is recommended therapy. However, oral therapy is desirable as the intravenous route is costly, time-consuming, more difficult to administer and carries a risk of needlestick injury.

OBJECTIVE

To investigate whether therapeutic TMP levels for treatment of PCP can be attained with oral therapy in HIV-infected children.

METHODS

A prospective dose-escalation study was undertaken of serum TMP levels attained following oral doses of TMP of 5 mg/kg, 10 mg/kg or 20 mg/kg in stable HIV-infected children. Children who received a 20 mg/kg dose were randomised to get a second dose (5 or 10 mg/kg TMP) at 6 hours. TMP levels were measured at baseline, peak (3 hours), and trough (6 hours) using liquid chromatography. An additional TMP level was taken at 9 hours in those who received a second TMP dose.

RESULTS

Median (25th-75th percentile) peak serum TMP levels following a 5 mg/kg, 10 mg/kg or 20 mg/kg oral loading dose were 0.93 (0.5-1.5) microg/ml, 1.94 (1.4-2.2) microg/ml and 7.68 (6.1-7.8) microg/ml respectively. Peak TMP levels at 9 hours after a second TMP dose of 5 or 10 mg/kg were 6.98 (3.4-8.8) microg/ml and 9.25 (8.2-10.3) microg/ml respectively.

CONCLUSION

Therapeutic concentrations of TMP for treatment of P. jiroveci can be attained with an oral loading dose of 20 mg/kg and sustained with a second dose at 6 hours of either 5 mg or 10 mg/kg in stable HIV-infected children.

[Immunological regulation and treatment of Brucea javanica and Fructus Psoraleae on rats with Pneumocystis carinii pneumonia]

OBJECTIVE

To study the immunological regulation and treatment of Brucea javanica and Fructus Psoraleae, traditional Chinese medicine, on rats with Pneumocystis carinii pneumonia (PCP).

METHODS

Rats were injected subcutaneously by dexamethasone. When the rats got Pc infected, they were divided into two groups: rats in one group were treated with the mixture of Brucea javanica and Fructus Psoraleae and another group was used as infected control. Control with normal rats was also established. Observations were made on the number of cysts in lungs and the changes of CD4+ T cells, CD8+ T cells and TNF-alpha in the serum to demonstrate the immunological regulation and killing effect of the medicine on cysts in the infected rats.

RESULTS

The body weight of the rats treated with Brucea javanica and Fructus Psoraleae increased considerably than that of immunosuppressed rats and the normal control. The damaged lung got improved and repaired, and a significant cyst reduction was shown in the treated group. The CD4+ T cells, CD8+ T cells and level of TNF-alpha in serum also increased in the treated group significantly.

CONCLUSION

The mixture of Brucea javanica and fructus psoraleae plays an immunological regulation on rats with Pneumocystis carinii pneumonia and shows certain killing effect on the cysts.

[Pneumocystis pneumonia in newborns: a challenge in contemporary intensive care]

Pneumocystis jiroveci (P. jiroveci) is the etiological agent of pneumocystis pneumonia (PCP) in immunodeficient patients. The increased interest of clinicians in this particular pathogen during the past decade was prompted by rising numbers of patients with immunosuppression caused by AIDS, chemotherapy, or organ transplantation. Premature, seriously ill infants at intensive care units constitute a potential risk group for infection with P. jiroveci. Recent advances in medical sciences, owing mainly to developments in molecular biology, permitted the verification of the taxonomic position of pathogens and contributed to a better understanding of new aspects of pathophysiology and pathogenesis of PCP. It has been demonstrated that the genus Pneumocystis represents a heterogeneous group of opportunistic fungi exhibiting narrow host specificity. Pneumocystis jiroveci is the species which is specific for humans. The present paper outlines the clinical symptoms of PCP in infants, currently used diagnostic methods, and treatment procedures in PCP.

QSAR analysis of 2,4-diaminopyrido[2,3-d]pyrimidines and 2,4-diaminopyrrolo[2,3-d]pyrimidines as dihydrofolate reductase inhibitors

Dihydrofolate reductase (DHFR) plays a ubiquitous role in the biosynthesis of DNA, RNA and essential amino acid methionine, and exhibits potential application in the treatment and prophylaxis of AIDS-associated opportunistic microbial infections. In this study, a series of DHFR analogs of 2,4-diaminopyrido[2,3-d]pyrimidines and 2,4-diaminopyrrolo[2,3-d]pyrimidines were subjected to quantitative structure-activity relationship (QSAR) analysis. The results showed that the electronic properties, energy of lowest unoccupied molecular orbital (LUMO) and Z-component of dipole moment (DPL3) of the molecule could be explored to design the potent DHFR inhibitors. LUMO is indicative of pi-bonding interaction of species crucial for the electrophilicity of the molecules. This suggests that molecules are able to interact with electron-rich area at the receptor site. DPL3 is related to the molecular charge distribution in Z-component. These electronic parameters can be altered through the incorporation of electronegative groups. The QSAR study provides important structural insights for designing the potent DHFR inhibitors.

Design, synthesis, and antifolate activity of new analogues of piritrexim and other diaminopyrimidine dihydrofolate reductase inhibitors with omega-carboxyalkoxy or omega-carboxy-1-alkynyl substitution in the side chain

As part of a search for dihydrofolate reductase (DHFR) inhibitors combining the high potency of piritrexim (PTX) with the high antiparasitic vs mammalian selectivity of trimethoprim (TMP), the heretofore undescribed 2,4-diamino-6-(2',5'-disubstituted benzyl)pyrido[2,3-d]pyrimidines 6-14 with O-(omega-carboxyalkyl) or omega-carboxy-1-alkynyl groups on the benzyl moiety were synthesized and tested against Pneumocystis carinii, Toxoplasma gondii, and Mycobacterium avium DHFR vs rat DHFR. Three N-(2,4-diaminopteridin-6-yl)methyl)-2'-(omega-carboxy-1-alkynyl)dibenz[b,f]azepines (19-21) were also synthesized and tested. The pyridopyrimidine with the best combination of potency and selectivity was 2,4-diamino-5-methyl-6-[2'-(5-carboxy-1-butynyl)-5'-methoxy]benzyl]pyrimidine (13), with an IC(50) value of 0.65 nM against P. carinii DHFR, 0.57 nM against M. avium DHFR, and 55 nM against rat DHFR. The potency of 13 against P. carinii DHFR was 20-fold greater than that of PTX (IC(50) = 13 nM), and its selectivity index (SI) relative to rat DHFR was 85, whereas PTX was nonselective. The activity of 13 against P. carinii DHFR was 20 000 times greater than that of TMP, with an SI of 96, whereas that of TMP was only 14. However 13 was no more potent than PTX against M. avium DHFR, and its SI was no better than that of TMP. Molecular modeling dynamics studies using compounds 10 and 13 indicated a slight binding preference for the latter, in qualitative agreement with the IC(50) data. Among the pteridines, the most potent against P. carinii DHFR and M. avium DHFR was the 2'-(5-carboxy-1-butynyl)dibenz[b,f]azepinyl derivative 20 (IC(50) = 2.9 nM), whereas the most selective was the 2'-(5-carboxy-1-pentynyl) analogue 21, with SI values of >100 against both P. carinii and M. avium DHFR relative to rat DHFR. The final compound, 2,4-diamino-5-[3'-(4-carboxy-1-butynyl)-4'-bromo-5'-methoxybenzyl]pyrimidine (22), was both potent and selective against M. avium DHFR (IC(50) = 0.47 nM, SI = 1300) but was not potent or selective against either P. carinii or T. gondii DHFR.

Activity of Hoechst 33258 against Pneumocystis carinii f. sp. muris, Candida albicans, and Candida dubliniensis

Hoechst 33258 is a compound that binds nucleic acids. We report that Hoechst 33258 exhibits antimicrobial activity against Pneumocystis carinii f. sp. muris in a mouse model for P. carinii pneumonia and against Candida albicans and Candida dubliniensis in vitro. Relative to saline treatment, a 14-day, daily treatment of mice with 37.5 mg of Hoechst 33258/kg of body weight after inoculation with P. carinii reduced by about 100-fold the number of P. carinii organisms detected by either PCR or by microscopy after silver staining. For comparison, treatment based on a dose of 15 to 20 mg of the trimethoprim component in trimethoprim-sulfamethoxazole/kg reduced the number of P. carinii by about fourfold. In vitro inhibition of P. carinii group I intron splicing was observed with a 50% inhibitory concentration (IC50) of 30 microM in 2 or 4 mM Mg2+, suggesting RNA as a possible target. However, Hoechst 33258 inhibits growth of Candida strains with and without group I introns. IC50s ranged from 1 to 9 microM for strains with group I introns and were 12 and 32 microM for two strains without group I introns. These studies demonstrate that compounds that bind fungal nucleic acids have the potential to be developed as new therapeutics for Pneumocystis and possibly other fungi, especially if they could be directed to structures that are not present in mammalian cells, such as self-splicing introns.

Highly active anti-Pneumocystis carinii compounds in a library of novel piperazine-linked bisbenzamidines and related compounds

Trimethoprim-sulfamethoxazole and pentamidine isethionate have been used extensively for the prophylaxis and therapy of pneumonia caused by Pneumocystis jirovecii. Problems associated with toxicity and potential emerging resistance for both therapies necessitate the development of safe and effective analogs or new treatment strategies. In the present study, a library of 36 compounds was synthesized by using the pentamidine molecule as the parent compound modified by a 1,4-piperazinediyl moiety as the central linker to restrict conformation flexibility. The compounds were evaluated for anti-Pneumocystis carinii activity in a bioluminescent ATP-driven assay. Four of the compounds were highly active, with 50% inhibitory concentration (IC(50)) values of <0.01 microg/ml; four had very marked activity (IC(50) < 0.10 microg/ml); ten had marked activity (IC(50) < 1.0 microg/ml); nine had moderate activity (IC(50) < 10 microg/ml); one had slight activity (IC(50) = 34.1 microg/ml); and the remaining eight did not demonstrate activity in this assay system. The high level of activity was specifically associated with an alkyl chain length of five to six carbons attached to one of the nitrogens of the bisamidinium groups. None of the highly active compounds and only one of the very marked compounds exhibited any toxicity when evaluated in three mammalian cell lines. The strategy of substitution of 1,4-piperazine-linked bisbenzamidines produced compounds with the highest level of activity observed in the ATP assay and holds great promise for the development of efficacious anti-P. carinii therapy.

Dihydropteroate synthase gene mutations in Pneumocystis and sulfa resistance

We review studies of dihydropteroate synthase gene mutations in Pneumocystis jirovecii and summarize the evidence for resistance to sulfamethoxazole and dapsone.

Pneumocystis pneumonia (PCP) remains a major cause of illness and death in HIV-infected persons. Sulfa drugs, trimethoprim-sulfamethoxazole (TMP-SMX) and dapsone are mainstays of PCP treatment and prophylaxis. While prophylaxis has reduced the incidence of PCP, its use has raised concerns about development of resistant organisms. The inability to culture human Pneumocystis, Pneumocystis jirovecii, in a standardized culture system prevents routine susceptibility testing and detection of drug resistance. In other microorganisms, sulfa drug resistance has resulted from specific point mutations in the dihydropteroate synthase (DHPS) gene. Similar mutations have been observed in P. jirovecii. Studies have consistently demonstrated a significant association between the use of sulfa drugs for PCP prophylaxis and DHPS gene mutations. Whether these mutations confer resistance to TMP-SMX or dapsone plus trimethoprim for PCP treatment remains unclear. We review studies of DHPS mutations in P. jirovecii and summarize the evidence for resistance to sulfamethoxazole and dapsone.

Sulfa use, dihydropteroate synthase mutations, and Pneumocystis jirovecii pneumonia

Meta-analysis shows increased risk for DHPS mutations in patients exposed to sulfa prophylaxis for PCP, but clinical relevance of mutations is not known.

A systematic review was conducted to examine the associations in Pneumocystis jirovecii pneumonia (PCP) patients between dihydropteroate synthase (DHPS) mutations and sulfa or sulfone (sulfa) prophylaxis and between DHPS mutations and sulfa treatment outcome. Selection criteria included study populations composed entirely of PCP patients and mutation or treatment outcome results for all patients, regardless of exposure status. Based on 13 studies, the risk of developing DHPS mutations is higher for PCP patients receiving sulfa prophylaxis than for PCP patients not receiving sulfa prophylaxis (p < 0.001). Results are too heterogeneous (p < 0.001) to warrant a single summary effect estimate. Estimated effects are weaker after 1996 and stronger in studies that included multiple isolates per patient. Five studies examined treatment outcome. The effect of DHPS mutations on treatment outcome has not been well studied, and the few studies that have been conducted are inconsistent even as to the presence or absence of an association.

Iron chelator daphnetin against Pneumocystis carinii in vitro

BACKGROUND

Although there are several drugs and drug combinations for the treatment of Pneumocystis carinii (P. carinii) pneumonia, all drugs have the toxicity as well as low efficacy. Iron chelators have been proposed as a source of new drugs for combating these infections. We hypothesized that iron chelators would suppress the growth of P. carinii by deprivation of the nutritional iron required for growth. In this study, a short-term axenic culture system of P. carinii was established. Daphnetin (7,8-dihydroxycoumarin), a known iron chelator, was demonstrated to exhibit in vitro activity against P. carinii in this system.

METHODS

P. carinii organisms were obtained from the lungs of immunosuppressed rats. The culture system consisted of Iscove Dulbecco Eagle's Minimum Essential Medium (IMDM), supplemented with S-adenosyl-L-methionine, N-acetylglucosamine, putrescine, L-cysteine, L-glutamine, 2-mercaptoethanol, and fetal bovine serum, and was maintained at 37 degrees C, in 5% CO(2), 95% O(2), at the optimal pH of 8.0. The culture system was used to assess the effect of daphnetin on the proliferation of P. carinii organisms. The ultrastructures of the treated organisms were observed by transmission electron microscopy.

RESULTS

The number of cysts and trophozoites increased 8- to 9-fold and 11- to 12-fold, respectively, after 10 days of culture. Daphnetin was found to suppress the growth of P. carinii in a dose-dependent manner at concentrations between 1 micromol/L and 20 micromol/L. The inhibitory activity was suppressed by the chelation of daphnetin with ferrous sulfate in a 2:1 molar ratio, but it was not suppressed by mixing the culture medium with magnesium sulfate. Reduction of P. carinii numbers after treatment with daphnetin correlated with morphological changes in the organisms, as determined by transmission electron microscopy.

CONCLUSIONS

Daphnetin can suppress the growth of P. carinii in vitro. The efficacy of daphnetin in suppressing the the growth of P. carinii in vitro is related to its ability to chelate iron.

Preliminary in vitro studies on two potent, water-soluble trimethoprim analogues with exceptional species selectivity against dihydrofolate reductase from Pneumocystis carinii and Mycobacterium avium

2,4-Diamino-5-[3',4'-dimethoxy-5'-(5-carboxy-1-pentynyl)]benzylpyrimidine (6) and 2,4-diamino-5-[3',4'-dimethoxy-5'-(4-carboxyphenylethynyl)benzylpyrimidine (7) were synthesized from 2,4-diamino-5-(5'-iodo-3',4'-dimethoxybenzyl)pyrimidine (9) via a Sonogashira reaction with appropriate acetylenic esters followed by saponification, and were tested as inhibitors of dihydrofolate reductase (DHFR) from Pneumocystis carinii (Pc), Toxoplasma gondii (Tg), Mycobacterium avium (Ma), and rat in comparison with the widely used antibacterial agent 2,4-diamino-5-(3',4',5'-trimethoxybenzyl)pyrimidine (trimethoprim, TMP). The selectivity index (SI) for each compound was calculated by dividing its 50% inhibitory concentration (IC(50)) against rat DHFR by its IC(50) against Pc, Tg, or Ma DHFR. The IC(50) of 6 against Pc DHFR was 1.0 nM, with an SI of 5000. Compound 7 had an IC(50) of 8.2 nM against Ma DHFR, with an SI of 11000. By comparison, the IC(50) of TMP was 12000 nM against Pc, 300 nM against Ma, and 180000 against rat DHFR. The potency and selectivity values of 6 and 7 were not as high against Tg as they were against Pc or Ma DHFR, but nonetheless exceeded those of TMP. Because of the outstanding selectivity of 6 against Pc and of 7 against Ma DHFR, these novel analogues may be viewed as promising leads for further structure-activity optimization.

Pneumocystis pneumonia: an update

Pneumocystis pneumonia is a major cause of illness and death in immunocompromised hosts. The numbers of pneumocystis pneumonia cases in Thailand have increased each year from 1992 to 2000 and peaked in 2000 at 6,255 cases. The microbe that causes pneumocystis pneumonia in humans is called Pneumocystis jirovecii. Pneumocystis sp. was discovered nearly a century ago, but the knowledge of Pneumocystis sp. remained poorly understood, until the molecular biology techniques help scientists verify it fungus nature. In the past, Pneumocystis sp. was misclassified as protozoan due to its morphologic features. Later, it was reclassified as fungus due to DNA analysis. Cotrimaxazole, the combination of trimethoprim-sulfamethoxazole, is the drug of choice for treatment and prophylaxis of pneumocystis pneumonia. However, increasing evidence of mutations in the enzyme dihydropteroate synthase (DHPS), the target of sulfa drugs represent emergence of sulfa resistance.

Novel bisbenzamidines as potential drug candidates for the treatment of Pneumocystis carinii pneumonia

A series of pentamidine congeners has been synthesized and screened for their in vitro activity against Pneumocystis carinii. Among the tested compounds, bisbenzamidines linked by a flexible pentanediamide or hexanediamide chain (7 and 9) emerged as exceptionally potent agents that were more effective and less toxic than pentamidine in the assays described in this study.

[Genotypic resistance to sulfamide drugs among patients with Pneumocystis jiroveci pneumonia]

BACKGROUND AND OBJECTIVE

The absence of culture methods to recognize the presence of resistance to sulfa or sulfone drugs in Pneumocystis jiroveci has led to develop molecular techniques based on the identification of mutations in the dihydropteroate synthase gene (DHPS). The aim of this study was to determine the frequency of these mutations in our geographical area, since in Spain there is no information concerning this issue.

PATIENTS AND METHOD

The study included all Pneumocystis pneumonia cases identified in our hospital during two years. Diagnosis was made by nested PCR in bronchoalveolar lavage samples. DHPS-3 and DHPS-4 primers were used to amplify the DHPS gene and mutations associated with sulfa resistance were identified using a restriction fragment length polymorphism assay.

RESULTS

In 9 out of the 12 cases identified, DHPS could be amplified (75%) from which 3 (33.3%) showed some mutation linked to sulfa resistance.

CONCLUSIONS

In our area, we have found a relatively high frequency of pneumonia caused by P. jiroveci's strains with mutations associated with sulfa resistance.

Failure of Low‐Dose Atovaquone Prophylaxis againstPneumocystis jiroveciInfection in Transplant Recipients

Trimethoprim-sulfamethoxazole is the preferred agent for prophylaxis against Pneumocystis jiroveci pneumonia. Alternative agents are used in treating patients who do not tolerate this medication. We report 2 cases of prophylaxis failure in patients receiving low-dose atovaquone. We discuss the use of atovaquone as an alternative agent for prophylaxis in transplant recipients.

Use of dapsone in the treatment of Pneumocystis carinii pneumonia in a foal

A 6-month-old male Quarter Horse was evaluated for chronic respiratory tract disease. Diagnostic investigations revealed pulmonary inflammation; Pneumocystis carinii was detected within macrophages. Lymphocyte subpopulation phenotyping and immunoglobulin concentration analysis were performed and results suggested immune suppression. Trimethoprim-sulfamethoxazole administration was initiated; the colt was discharged but was reexamined 8 days later because of profuse diarrhea and endotoxemia. Bacterial culture of feces recovered Salmonella spp resistant to trimethoprim-sulfamethoxazole, and a diagnosis of antimicrobial-associated colitis was made. Bilateral fibrinous hypopyon developed and was treated with topical medication and intracameral injections of human recombinant tissue plasminogen activator. Dapsone (3 mg/kg [1.4 mg/lb], PO, q 24 h; dose extrapolated from human data) was administered for treatment of P carinii pneumonia (56-day treatment period). The colt recovered from the pneumonia and diarrhea. Dapsone may be a useful adjunct to traditional treatment for P carinii pneumonia in horses or as a sole medication for horses that cannot tolerate other treatments.