Eflornithine treatment of refractory Pneumocystis carinii pneumonia in patients with acquired immunodeficiency syndrome

Treatment of Pneumocystis jirovecii pneumonia in HIV-infected patients: a review

INTRODUCTION

Pneumocystis pneumonia is a potentially life-threatening pulmonary infection that occurs in immunocompromised individuals and HIV-infected patients with a low CD4 cell count. Trimethoprim-sulfamethoxazole has been used as the first-line agent for treatment, but mutations within dihydropteroate synthase gene render potential resistance to sulfamide. Despite advances of combination antiretroviral therapy (cART), Pneumocystis pneumonia continues to occur in HIV-infected patients with late presentation for cART or virological and immunological failure after receiving cART. Areas covered: This review summarizes the diagnosis and first-line and alternative treatment and prophylaxis for Pneumocystis pneumonia in HIV-infected patients. Articles for this review were identified through searching PubMed. Search terms included: 'Pneumocystis pneumonia', 'Pneumocystis jirovecii pneumonia', 'Pneumocystis carinii pneumonia', 'trimethoprim-sulfamethoxazole', 'primaquine', 'trimetrexate', 'dapsone', 'pentamidine', 'atovaquone', 'echinocandins', 'human immunodeficiency virus infection', 'acquired immunodeficiency syndrome', 'resistance to sulfamide' and combinations of these terms. We limited the search to English language papers that were published between 1981 and March 2017. We screened all identified articles and cross-referenced studies from retrieved articles. Expert commentary: Trimethoprim-sulfamethoxazole will continue to be the first-line agent for Pneumocystis pneumonia given its cost, availability of both oral and parenteral formulations, and effectiveness or efficacy in both treatment and prophylaxis. Whether resistance due to mutations within dihydropteroate synthase gene compromises treatment effectiveness remains controversial. Continued search for effective alternatives with better safety profiles for Pneumocystis pneumonia is warranted.

Co-infection of Mycobacterium tuberculosis and Pneumocystis jirovecii in the Iranian Patients With Human Immunodeficiency Virus

Background:

Based on the authors’ knowledge, there is no study on the co-infection of opportunistic agents such as Mycobacterium tuberculosis and Pneumocystis jirovecii in the lungs of Iranian patients with immunosuppression.

Objectives:

The current study aimed to show the rate of co-infection of M. tuberculosis and P. jirovecii in patients with Human Immunodeficiency Virus (HIV).

Patients and Methods:

Forty-five pulmonary samples were collected from 30 patients with HIV who also infected with Tuberculosis and Pneumonia. All of the patients were admitted to two university hospitals of Mycobacteriology and the Iranian HIV/AIDS research centers. DNA of P. jirovecii was detected using nested-Polymerase Chain Reaction (nested-PCR) assay.

Results:

All of the patients were male with the mean age of 32.95 ± 7.15 years. The mean of CD4 cell count was 109.25 cell/mm³. Of 30 patients with HIV, three (10%) were co-infected with M. tuberculosis and P. jirovecii. No other causes of pneumonia were found in those three patients and CD4 cell counts less than 50 cell/mm³ was reported.

Conclusions:

The results of the current study showed a high rate of co-infection of M. tuberculosis and P. jirovecii in the Iranian patients with HIV. As the immune system condition worsened, the probability of occurrence of Pneumocystis Pneumonia (PCP) increased. Therefore, more specific, most rapid and sensitive tests should be utilized for diagnosis of PCP in this group of patients.

Drug repurposing and human parasitic protozoan diseases

Parasitic diseases have an enormous health, social and economic impact and are a particular problem in tropical regions of the world. Diseases caused by protozoa and helminths, such as malaria and schistosomiasis, are the cause of most parasite related morbidity and mortality, with an estimated 1.1 million combined deaths annually. The global burden of these diseases is exacerbated by the lack of licensed vaccines, making safe and effective drugs vital to their prevention and treatment. Unfortunately, where drugs are available, their usefulness is being increasingly threatened by parasite drug resistance. The need for new drugs drives antiparasitic drug discovery research globally and requires a range of innovative strategies to ensure a sustainable pipeline of lead compounds. In this review we discuss one of these approaches, drug repurposing or repositioning, with a focus on major human parasitic protozoan diseases such as malaria, trypanosomiasis, toxoplasmosis, cryptosporidiosis and leishmaniasis.

Polyamine transport as a target for treatment of Pneumocystis pneumonia

Polyamine levels are greatly increased in alveolar macrophages (AMs) during Pneumocystis pneumonia (PCP), leading to increased production of H(2)O(2), which causes AMs to undergo apoptosis. One of the mechanisms by which polyamine levels in AMs are elevated is enhanced uptake of exogenous polyamines. In this study, the possibility of targeting polyamine uptake as a treatment for PCP was examined. Four anthracene- and one benzene-polyamine conjugates that are potential polyamine transport inhibitors, including N1-anthracen-9-ylmethyl-butane-1,4-diamine; N-(4-aminobutyl)-N-anthracen-9-ylmethylbutane-1,4-diamine; N-[4-(4-aminobutylamino)butyl]-N-anthracen-9-ylmethylbutane-1,4-diamine; N-(4-amino-butyl)-N'-(10-[[4-(4-amino-butylamino)butylamino]-methyl]anthracen-9-ylmethyl)butane-1,4-diamine (44-Ant-44); and benzene-polyamine conjugate N-(4-amino-butyl)-N'-(4-[[4-(4-amino-butylamino)butylamino]-methyl]benzyl)butane-1,4-diamine (44-Bn-44), were tested. Compounds 44-Ant-44 and 44-Bn-44 were found to have a very low toxicity to AMs in vitro and were evaluated for their therapeutic effect on PCP in vivo. Sprague-Dawley rats infected with P. carinii for 28 days were intranasally instilled with 50 microl of a 1 mM solution of 44-Bn-44 or 44-Ant-44 every 2 days. Twenty-one days after initiation of the treatment, three to five rats from each group were sacrificed and examined for lung pathology, organism burden, and apoptosis of AMs. Both 44-Bn-44 and 44-Ant-44 reduced organism burdens; however, only 44-Ant-44 decreased the severity of the infection with reduced lung inflammation, increased clearance of exudates, increased air space, and decreased apoptosis of AMs. 44-Ant-44 also significantly prolonged the survival of treated animals. These results suggest that polyamine uptake is a potential target for treatment of PCP.

Mechanism and tissue specificity of nicotine-mediated lung S-adenosylmethionine reduction

We previously reported that chronic nicotine infusion blocks development of Pneumocystis pneumonia. This discovery developed from our work demonstrating the inability of this fungal pathogen to synthesize the critical metabolic intermediate S-adenosylmethionine and work by others showing nicotine to cause lung-specific reduction of S-adenosylmethionine in guinea pigs. We had found nicotine infusion to cause increased lung ornithine decarboxylase activity (rate-controlling enzyme of polyamine synthesis) and hypothesized that S-adenosylmethionine reduction is driven by up-regulated polyamine biosynthesis. Here we report a critical test of our hypothesis; inhibition of ornithine decarboxylase blocks the effect of nicotine on lung S-adenosylmethionine. Further support is provided by metabolite analyses showing nicotine to cause a strong diversion of S-adenosylmethionine toward polyamine synthesis and away from methylation reactions; these shifts are reversed by inhibition of ornithine decarboxylase. Because the nicotine effect on Pneumocystis is so striking, we considered the possibility of tissue specificity. Using laser capture microdissection, we collected samples of lung alveolar regions (site of infection) and respiratory epithelium for controls. We found nicotine to cause increased ornithine decarboxylase protein in alveolar regions but not airway epithelium; we conclude that tissue specificity likely contributes to the effect of nicotine on Pneumocystis pneumonia. Earlier we reported that the full effect of nicotine requires 3 weeks of treatment, and here we show recovery is symmetrical, also requiring 3 weeks after treatment cessation. Because this time frame is similar to pneumocyte turnover time, the shift in polyamine metabolism may occur as new pneumocytes are produced.

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.

Pneumocystis carinii: genetic diversity and cell biology

As an important opportunistic pulmonary pathogen, Pneumocystis carinii has been the focus of extensive research over the decades. The use of laboratory animal models has permitted a detailed understanding of the host-parasite interaction but an understanding of the basic biology of P. carinii has lagged due in large part to the inability of the organism to grow well in culture and to the lack of a tractable genetic system. Molecular techniques have demonstrated extensive heterogeneity among P. carinii organisms isolated from different host species. Characterization of the genes and genomes of the Pneumocystis family has supported the notion that the family comprises different species rather than strains within the genus Pneumocystis and contributed to the understanding of the pathophysiology of infection. Many of the technical obstacles in the study of the organisms have been overcome in the past decade and the pace of research into the basic biology of the organism has accelerated. Biochemical pathways have been inferred from the presence of key enzyme activities or gene sequences, and attempts to dissect cellular pathways have been initiated. The Pneumocystis genome project promises to be a rich source of information with regard to the functional activity of the organism and the presence of specific biochemical pathways. These advances in our understanding of the biology of this organism should provide for future studies leading to the control of this opportunistic pathogen.

Dual pulmonary infection with Mycobacterium tuberculosis and Pneumocystis carinii in patients infected with human immunodeficiency virus

During a 22-month period, we identified 39 patients with human immunodeficiency virus (HIV) infection (mean CD4(+) count, 90 cells/mm(3)) who were hospitalized with pneumonia and who had sputum and/or other specimens that tested concurrently positive for both Mycobacterium tuberculosis and Pneumocystis carinii. The most common chest x-ray abnormality was a reticulonodular pattern or bilateral infiltrates (n=26). Serum lactate dehydrogenase levels were elevated in 17 (85%) of 20 of patients tested (mean value, 2208 U/L). Mean O(2) saturation and PO(2) were 89% and 64 mm Hg, respectively. A majority (24 patients [62%]) received both antituberculous and anti-PCP therapy (17 with steroids), and 22 improved. All ten patients who received no treatment for PCP improved and were discharged from the hospital, whereas 4 (80%) of the 5 persons who received no antituberculous treatment had a poor outcome (P<.001; OR=43). Patients with HIV or acquired immune deficiency syndrome may present with both TB and PCP; of the 2, TB seems to account for the most severe features of disease.

Pneumocystis carinii polyamine catabolism

DL-alpha-Difluoromethylornithine (DFMO) causes polyamines of the AIDS-associated opportunistic pathogen Pneumocystis carinii to diminish 15 times more rapidly than mammalian host cells. The proposed mechanism was that, unlike mammalian cells, P. carinii is unable to regulate polyamine catabolism when synthesis is blocked. To test this, the responses of the polyamine catabolic enzymes spermidine/spermine acetyltransferase (SSAT) and polyamine oxidase (PAO) were determined using a new high-performance liquid chromatography assay to measure the products of these enzymes. The specific activities in untreated Pneumocystis carinii were 1.78 +/- 0.5 pmol min(-1) mg protein(-1) for SSAT, similar to mammalian cells, and 6.42 +/- 0.8 pmol min(-1) mg protein(-1) for PAO, 19% of that of mammalian cells. DFMO treatment for 12 h caused reductions of only 11 and 4% in SSAT and PAO, respectively, despite polyamine reductions of 94, 96, and 90% for putrescine, spermidine, and spermine, respectively. The P. carinii SSAT K(m) value of 25 microM spermidine is 20% of that of mammalian cells, and the PAO K(m) value of 14 nM N(1)-acetylspermidine is 0.01% of that of mammalian cells. Acetylated polyamines continue to be lost from P. carinii even when exposed to DFMO. Collectively, these results support the hypothesis that P. carinii is unable to regulate polyamine catabolism.

Acute respiratory failure in the HIV-seropositive patient

Since approximately 40% to 65% of patients with AIDS will develop pulmonary disease, HIV-seropositive patients represent a large cohort of immunosuppressed individuals with the potential to progress to respiratory failure requiring mechanical ventilation and admission to the intensive care unit. This article reviews the cause, pathophysiology, diagnostic approach, and management of acute respiratory failure requiring mechanical ventilation in HIV-seropositive patients. Prognostic factors and survival rates for episodes of respiratory failure are also discussed. In addition, an overview of acute respiratory failure in pediatric AIDS patients is presented.

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.

Continuous infusion of DL-alpha-difluoromethylornithine and improved efficacy against a rat model of Pneumocystis carinii pneumonia

The rapid depletion of Pneumocystis carinii polyamines caused by in vitro exposure to DL-alpha-difluoromethylornithine (DFMO; also called eflornithine or Ornidyl) and the rapid repletion following removal of this drug suggested that the in vivo efficacy of DFMO against P. carinii pneumonia (PCP) may be limited by troughs in drug concentration resulting from the schedule of administration. This led to the prediction that, compared with the response to the standard animal protocol of administering DFMO in drinking water, the response of a rat model of PCP to DFMO would be lessened by bolus administration and improved by continuous infusion. These predictions were confirmed. Intraperitoneal bolus administration of up to 3 g of DFMO kg of body weight-1 was completely ineffective, although this dose has been shown to be effective when given in the drinking water. Conversely, continuous infusion improved the response against PCP seven- to ninefold over the response to drinking water administration. These findings suggest that, compared with the standard clinical investigational protocol for treatment of PCP with DFMO given in four divided daily doses, continuous infusion combined with monitoring of drug concentrations in plasma may improve efficacy and/or reduce the already low rate of adverse effects.

Polyamine content of Pneumocystis carinii and response to the ornithine decarboxylase inhibitor DL-alpha-difluoromethylornithine

Difluoromethylornithine (DFMO; eflornithine hydrochloride [Ornidyl]), a suicide inhibitor of the key polyamine biosynthesis enzyme ornithine decarboxylase (ODC), is effective in treating Pneumocystis carinii pneumonia, a common opportunistic infection associated with AIDS. Despite DFMO's specificity for ODC, the reason for its selective toxicity against P. carinii is unknown since both host and parasite are dependent on the same enzyme for polyamine biosynthesis. A new high-performance liquid chromatography method was used with P. carinii cells isolated from infected rat lungs to measure polyamine content, to confirm the presence of ODC, and to examine the effect of DFMO on polyamine concentrations. Putrescine, spermidine, and spermine were found to be present at 2.00 +/- 0.54, 1.26 +/- 0.51, and 1.59 +/- 0.91 nmol (mg of protein)-1, respectively, neither unusually high nor low values. ODC's specific activity was 79 +/- 11 pmol (mg of protein)-1 h-1, again not a remarkable value. However, the rates of both DFMO-induced polyamine depletion and subsequent repletion upon DFMO removal were unusually high. A 3-h exposure to 1 mM DFMO in vitro caused the depletion of putrescine, spermidine, and spermine to levels 12, 29, and 16%, respectively, of that of control cells. After DFMO removal and incubation for 1 h in serum-free media, polyamine levels returned to 78, 88, and 64%, respectively, of that of the control cells not exposed to DFMO. Since such depletions and repletions usually occur over periods of days rather than hours, these rapid changes may provide a clue to the selective action of DFMO against P. carinii and may guide the development of new compounds and an optimal drug administration schedule for DFMO.

Ornithine decarboxylase in Pneumocystis carinii and implications for therapy

Pneumocystis carinii pneumonia (PCP) can be treated with eflornithine (difluoromethylornithine, DFMO, Ornidyl), a competitive irreversible inhibitor of ornithine decarboxylase (ODC), a key enzyme for polyamine biosynthesis. Because ODC has been reported to be absent from P. carinii, it has been assumed that eflornithine affects P. carinii only indirectly, by affecting host polyamine biosynthesis. If this is true, then improvements in the selectivity of antipolyamine therapy for PCP would be limited. Since the presence of ODC in P. carinii is an important issue, a new search for this enzyme was made. Not only were initial assays negative, but P. carinii extract reduced the background catalytic action of pyridoxal-5'-phosphate, the coenzyme required by the enzyme. This suggested the presence of an inhibitor, which was further supported by the observation that a P. carinii extract could suppress a source of known ODC activity. The inhibitory activity could be removed by a desalting column or by dialysis, allowing detection of P. carinii ODC. Indirect evidence indicates that the inhibition is only apparent and is caused by unlabeled ornithine in the extract of P. carinii which interferes with the radiolabel-based assay system. P. carinii and host ODCs respond differently to changes in pH. P. carinii ODC is much less susceptible to inhibition by eflornithine than host ODC. The presence of ODC in P. carinii suggests that P. carinii ODC is the target of eflornithine and that P. carinii ODC may have sufficiently specific properties that inhibitors with improved selectivity against P. carinii ODC could be identified.

Pneumocystis carinii pneumonia in cancer patients

Concern has been arisen about the recently reported increasing incidence of PCP in patients with cancer and the potential transmissibility of this infection. Whether or not there is an increase in the incidence of P. carinii infections, PCP should be considered in the differential diagnosis of pulmonary infiltrates in bone marrow transplant recipients, in patients with hematologic neoplasms and in patients with primary or metastatic brain neoplasms. Intensity of immunosuppression plays a crucial role, especially long-term (> 2 months) corticosteroid treatment. PCP is usually manifested clinically during augmentation or during tapering of corticosteroid dose. Thus, if the chest radiograph of a high-risk patient shows diffuse infiltrates, bronchoscopy and bronchoalveolar lavage should be done immediately. Treatment options are the same as for the AIDS population, except that TMP-SMX is tolerated better in non-AIDS patients. The role of supportive care, including mechanical ventilation in such patients should not be underestimated. Oral therapy with dapsone-trimethoprim or with atovaquone, can be as effective as conventional therapy in mild disease, permitting treatment on an outpatient basis. PCP is often preventable and our understanding has improved about when prophylaxis should be initiated. In the future, the emergence of new technologies for diagnosis and of new agents for treatment and prophylaxis, will bring us closer to the goal of controlling this serious infection.

Ornithine decarboxylase as an enzyme target for therapy

Interest in ornithine decarboxylase (ODC) and the therapeutic effects of its inhibition with the consequent depletion of polyamine biosynthesis has been widespread since the late 1970s and 1980s. This review covers new information about the properties of ODC, recent findings with ODC inhibitors and a discussion of the mechanism of inactivation of ODC by eflornithine. Recent in vivo therapeutic approaches of ODC inhibition are also discussed including: cancer and cancer chemoprevention; autoimmune diseases; polyamines and the blood-brain barrier, ischemia and hyperplasia; the NMDA receptor and modulation by polyamines; hearing loss; African trypanosomiasis; Pneumocystis carinii pneumonia and Cryptosporidium in AIDS; and other infectious diseases/organisms.