Factors associated with Pneumocystis colonization and circulating genotypes in chronic obstructive pulmonary disease patients with acute exacerbation or at stable state and their homes

Pneumocystis jirovecii colonization is frequent during chronic obstructive pulmonary disease (COPD) and patients constitute potential contributors to its interhuman circulation. However, the existence of an environmental reservoir cannot be excluded. We assessed the prevalence and factors associated with Pneumocystis colonization during COPD, and studied circulation between patients and their domestic environment. Pneumocystis molecular detection and mtLSU genotyping were performed in oro-pharyngeal washes (OPW) sampled in 58 patients with COPD acute exacerbation, and in indoor dust, sampled in patients' homes using electrostatic dust collectors (EDCs). Lung and systemic inflammation was assessed. Pneumocystis carriage was evaluated in 28 patients after 18 months at stable state. Pneumocystis was detected in 11/58 OPWs during exacerbation (19.0%). Colonized patients presented a significantly lower body mass index, and higher serum IL-17 and CD62P. One patient presented positive detection of typable isolates in both OPW and EDC, with both isolates harboring mtLSU genotype 3. Pneumocystis genotype 1 was further detected in EDCs from three non-colonized patients and one colonized patient with non-typable isolate. Genotypes 1 and 2 were predominant in clinical isolates (both 42%), with genotype 3 representing 16% of isolates. Pneumocystis was detected in 3/28 patients at stable state (10.7%). These data suggest that Pneumocystis colonization could be facilitated by a lower BMI and be related to acute alteration of lung function during COPD exacerbation. It also suggests Th17 pathway and platelet activation could be involved in the anti-Pneumocystis response during colonization. Last, Pneumocystis detection in EDCs supports its potential persistence in indoor dust.

LAY SUMMARY

Chronic obstructive pulmonary disease patients tend to be more frequently colonized by Pneumocystis during exacerbation (19.0%) than at stable state (10.7%). Factors associated with colonization include lower BMI, higher IL-17, and CD62P. Pneumocystis detection in patients' dwellings suggests potential persistence in indoor dust.

Development and Evaluation of a Hybrid Course in Clinical Virology at a Faculty of Pharmacy in Lille, France

BACKGROUND

During their studies, pharmacy students must acquire the specific skills in clinical virology required for their subsequent professional practice. Recent experiments on teaching and learning in higher education have shown that hybrid courses strengthen the students' commitment to learning and enable high-quality knowledge acquisition.

OBJECTIVE

This study concerned the design and deployment of a hybrid course that combines face-to-face and Web-based instruction in clinical virology for fourth-year pharmacy students. The study's objectives were to (1) measure the students' level of involvement in the course, (2) gauge their interest in this type of learning, and (3) highlight any associated difficulties.

METHODS

The study included 194 fourth-year pharmacy students from the Lille Faculty of Pharmacy (University of Lille, Lille, France) between January and June 2017. The students followed a hybrid course comprising an online learning module and 5 tutorial sessions in which professional situations were simulated. The learning module and 3 online evaluation sessions were delivered via the Moodle learning management system. Each tutorial session ended with an evaluation. The number of Moodle log-ins, the number of views of learning resources, and the evaluation marks were recorded. The coefficient for the correlation between the marks in the online evaluation and those in the tutorials was calculated. The students' opinions and level of satisfaction were evaluated via a course questionnaire.

RESULTS

The course's learning resources and Web pages were viewed 21,446 and 3413 times, respectively. Of the 194 students, 188 (96.9%) passed the course (ie, marks of at least 10 out of 20). There was a satisfactory correlation between the marks obtained in the online evaluations and those obtained after the tutorials. The course met the students' expectations in 53.2% of cases, and 57.4% of the students stated that they were able to work at their own pace. Finally, 26.6% of the students stated that they had difficulty organizing their work around this hybrid course.

CONCLUSIONS

Our results showed that pharmacy students were strongly in favor of a hybrid course. The levels of attendance and participation were high. However, teachers must be aware that some students will encounter organizational difficulties.

Characterization of a Protein Phosphatase Type-1 and a Kinase Anchoring Protein in Plasmodium falciparum

With its multiple regulatory partners, the conserved Protein Phosphatase type-1 (PP1) plays a central role in many functions of the biology of eukaryotic cells, including Plasmodium falciparum. Here, we characterized a protein named PfRCC-PIP, as a major partner of PfPP1. We established its direct interaction in vitro and its presence in complex with PfPP1 in the parasite. The use of Xenopus oocyte model revealed that RCC-PIP can interact with the endogenous PP1 and act in synergy with suboptimal doses of progesterone to trigger oocyte maturation, suggesting a regulatory effect on PP1. Reverse genetic studies suggested an essential role for RCC-PIP since no viable knock-out parasites could be obtained. Further, we demonstrated the capacity of protein region containing RCC1 motifs to interact with the parasite kinase CDPK7. These data suggest that this protein is both a kinase and a phosphatase anchoring protein that could provide a platform to regulate phosphorylation/dephosphorylation processes.

Diffusion of Pneumocystis jirovecii in the surrounding air of patients with Pneumocystis colonization: frequency and putative risk factors

In a prospective bicentric study, Pneumocystis jirovecii excretion and diffusion was explored in air samples collected in the rooms occupied by 17 Pneumocystis-colonized patients. P. jirovecii DNA was detected by real-time PCR in the air collected from 3 patients' rooms (17.6%), with identical genotypes in corresponding clinical and air samples. Pneumocystis DNA was detected for 2/3 patients with autoimmune disease treated with corticosteroids versus 1/6 patients with hematologic disease and 0/5 kidney transplant recipients. These data confirm the possible excretion of the fungus by Pneumocystis-colonized patients and thus bring additional arguments for the prevention of airborne transmission in hospital wards.

In vitro coagulation triggers anti-Aspergillus fumigatus neutrophil response

AIM

To explore Aspergillus interactions with platelets in the blood, especially during clot formation.

MATERIALS & METHODS

Aspergillus fumigatus resting or swollen conidia, germlings or hyphae were inoculated into blood sampled into tubes with or without anticoagulant. Interactions were explored using microscopy, and chemokine levels were determined.

RESULTS

Anatomopathological examination of the clot revealed conidia and germlings colocalization with platelet aggregates, and neutrophil recruitment around aggregates. Transmission electron microscopy showed conidia and hyphae surrounded by neutrophils. Increased CCL5 and CXCL4 when conidia or germlings but not hyphae were added suggested they could be involved in neutrophil recruitment around aggregates.

CONCLUSION

These data suggest platelets could trigger coagulopathy and activate neutrophils during aspergillosis. They open up new perspectives for aspergillosis management.

Surfactant proteins, SP-A and SP-D, in respiratory fungal infections: their role in the inflammatory response

Pulmonary surfactant is a complex fluid that comprises phospholipids and four proteins (SP-A, SP-B, SP-C, and SP-D) with different biological functions. SP-B, SP-C, and SP-D are essential for the lungs’ surface tension function and for the organization, stability and metabolism of lung parenchyma. SP-A and SP-D, which are also known as pulmonary collectins, have an important function in the host’s lung immune response; they act as opsonins for different pathogens via a C-terminal carbohydrate recognition domain and enhance the attachment to phagocytic cells or show their own microbicidal activity by increasing the cellular membrane permeability. Interactions between the pulmonary collectins and bacteria or viruses have been extensively studied, but this is not the same for fungal pathogens. SP-A and SP-D bind glucan and mannose residues from fungal cell wall, but there is still a lack of information on their binding to other fungal carbohydrate residues. In addition, both their relation with immune cells for the clearance of these pathogens and the role of surfactant proteins’ regulation during respiratory fungal infections remain unknown. Here we highlight the relevant findings associated with SP-A and SP-D in those respiratory mycoses where the fungal infective propagules reach the lungs by the airways.

Relationship Between Pneumocystis carinii Burden and the Degree of Host Immunosuppression in an Airborne Transmission Experimental Model

To quantitatively assess the risk of contamination by Pneumocystis depending on the degree of immunosuppression (ID) of the exposed rat hosts, we developed an animal model, where rats went through different doses of dexamethasone. Then, natural and aerial transmission of Pneumocystis carinii occurred during cohousing of the rats undergoing gradual ID levels (receivers) with nude rats developing pneumocystosis (seeders). Following contact between receiver and seeder rats, the P. carinii burden of receiver rats was determined by toluidine blue ortho staining and by qPCR targeting the dhfr monocopy gene of this fungus. In this rat model, the level of circulating CD4(+) and CD8(+) T lymphocytes remained significantly stable and different for each dose of dexamethasone tested, thus reaching the goal of a new stable and gradual ID rat model. In addition, an inverse relationship between the P. carinii burden and the level of circulating CD4(+) or CD8(+) T lymphocytes was evidenced. This rat model may be used to study other opportunistic pathogens or even co-infections in a context of gradual ID.

Comparison of different blood compartments for the detection of circulating DNA using a rat model of Pneumocystis pneumonia

Pneumocystis is mostly found in the alveolar spaces, but circulation of viable organisms also occurs and suggests that the detection of DNA in blood could be used as a noninvasive procedure to improve the diagnosis of Pneumocystis pneumonia (PcP). In order to determine the optimal compartment for Pneumocystis DNA detection, we used a rat model of PcP and tested the presence of Pneumocystis with a quantitative mtLSU targeting real-time PCR in four blood compartments: whole blood, clot, serum and Platelet-Rich-Plasma (PRP). All samples from 4 Pneumocystis-free control rats were negative. Pneumocystis was detected in 79, 64, 57, and 57% of samples from 14 PcP rats, respectively, but DNA release was not related to pulmonary loads. These data confirm the potential usefulness of Pneumocystis DNA detection in the blood for PcP diagnosis and suggest that whole blood could be the most appropriate compartment for Pneumocystis detection.

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.

Initial data on the molecular epidemiology of cryptosporidiosis in Lebanon

Cryptosporidium spp. represent a major public health problem worldwide and infect the gastrointestinal tract of both immunocompetent and immunocompromised persons. The prevalence of these parasites varies by geographic region, and no data are currently available in Lebanon. To promote an understanding of the epidemiology of cryptosporidiosisin this country, the main aim of this study was to determine the prevalence Cryptosporidium in symptomatic hospitalized patients, and to analyze the genetic diversity of the corresponding isolates. Fecal specimens were collected in four hospitals in North Lebanon from 163 patients (77 males and 86 females, ranging in age from 1 to 88 years, with a mean age of 22 years) presenting gastrointestinal disorders during the period July to December 2013. The overall prevalence of Cryptosporidium spp. infection obtained by modified Ziehl-Neelsen staining and/or nested PCR was 11%, and children <5 years old showed a higher rate of Cryptosporidium spp. The PCR products of the 15 positive samples were successfully sequenced. Among them, 10 isolates (66.7%) were identified as C. hominis, while the remaining 5 (33.3%) were identified as C. parvum. After analysis of the gp60 locus, C. hominis IdA19, a rare subtype, was found to be predominant. Two C. parvum subtypes were found: IIaA15G1R1 and IIaA15G2R1. The molecular characterization of Cryptosporidium isolates is an important step in improving our understanding of the epidemiology and transmission of the infection.

What do Pneumocystis organisms tell us about the phylogeography of their hosts? The case of the woodmouse Apodemus sylvaticus in continental Europe and western Mediterranean islands

Pneumocystis fungi represent a highly diversified biological group with numerous species, which display a strong host-specificity suggesting a long co-speciation process. In the present study, the presence and genetic diversity of Pneumocystis organisms was investigated in 203 lung samples from woodmice (Apodemus sylvaticus) collected on western continental Europe and Mediterranean islands. The presence of Pneumocystis DNA was assessed by nested PCR at both large and small mitochondrial subunit (mtLSU and mtSSU) rRNA loci. Direct sequencing of nested PCR products demonstrated a very high variability among woodmouse-derived Pneumocystis organisms with a total number of 30 distinct combined mtLSU and mtSSU sequence types. However, the genetic divergence among these sequence types was very low (up to 3.87%) and the presence of several Pneumocystis species within Apodemus sylvaticus was considered unlikely. The analysis of the genetic structure of woodmouse-derived Pneumocystis revealed two distinct groups. The first one comprised Pneumocystis from woodmice collected in continental Spain, France and Balearic islands. The second one included Pneumocystis from woodmice collected in continental Italy, Corsica and Sicily. These two genetic groups were in accordance with the two lineages currently described within the host species Apodemus sylvaticus. Pneumocystis organisms are emerging as powerful tools for phylogeographic studies in mammals.

Complementation of a manganese-dependent superoxide dismutase-deficient yeast strain with Pneumocystis carinii sod2 gene

Manganese-dependent superoxide dismutase (MnSOD) is one of the key enzymes involved in the cellular defense against oxidative stress. Previously, the Pneumocystis carinii sod2 gene (Pcsod2) was isolated and characterized. Based on protein sequence comparison, Pcsod2 was suggested to encode a putative MnSOD protein likely to be targeted into the mitochondrion. In this work, the Pcsod2 was cloned and expressed as a recombinant protein in EG110 Saccharomyces cerevisiae strain lacking the MnSOD-coding gene (Scsod2) in order to investigate the function and subcellular localization of P. carinii MnSOD (PcMnSOD). The Pcsod2 gene was amplified by PCR and cloned into the pYES2.1/V5-His-TOPO(®) expression vector. The recombinant construct was then transformed into EG110 strain. Once its expression had been induced, PcMnSOD was able to complement the growth defect of EG110 yeast cells that had been exposed to the redox-cycling compound menadione. N-term sequencing of the PcMnSOD protein allowed identifying the cleavage site of a mitochondrial targeting peptide. Immune-colocalization of PcMnSOD and yeast CoxIV further confirmed the mitochondrial localization of the PcMnSOD. Heterologous expression of PcMnSOD in yeast indicates that Pcsod2 encodes an active MnSOD, targeted to the yeast mitochondrion that allows the yeast cells to grow in the presence of reactive oxygen species (ROS).

Histoplasma capsulatum and Pneumocystis spp. co-infection in wild bats from Argentina, French Guyana, and Mexico

Background

Histoplasma capsulatum and Pneumocystis organisms cause host infections primarily affecting the lung tissue. H. capsulatum is endemic in the United States of America and Latin American countries. In special environments, H. capsulatum is commonly associated with bat and bird droppings. Pneumocystis-host specificity has been primarily studied in laboratory animals, and its ability to be harboured by wild animals remains as an important issue for understanding the spread of this pathogen in nature. Bats infected with H. capsulatum or Pneumocystis spp. have been found, with this mammal serving as a probable reservoir and disperser; however, the co-infection of bats with both of these microorganisms has never been explored. To evaluate the impact of H. capsulatum and Pneumocystis spp. infections in this flying mammal, 21 bat lungs from Argentina (AR), 13 from French Guyana (FG), and 88 from Mexico (MX) were screened using nested-PCR of the fragments, employing the Hcp100 locus for H. capsulatum and the mtLSUrRNA and mtSSUrRNA loci for Pneumocystis organisms.

Results

Of the 122 bats studied, 98 revealed H. capsulatum infections in which 55 of these bats exhibited this infection alone. In addition, 51 bats revealed Pneumocystis spp. infection of which eight bats exhibited a Pneumocystis infection alone. A total of 43 bats (eight from AR, one from FG, and 34 from MX) were found co-infected with both fungi, representing a co-infection rate of 35.2% (95% CI = 26.8-43.6%).

Conclusion

The data highlights the H. capsulatum and Pneumocystis spp.co-infection in bat population’s suggesting interplay with this wild host.

Growth and airborne transmission of cell-sorted life cycle stages of Pneumocystis carinii

Pneumocystis organisms are airborne opportunistic pathogens that cannot be continuously grown in culture. Consequently, the follow-up of Pneumocystis stage-to-stage differentiation, the sequence of their multiplication processes as well as formal identification of the transmitted form have remained elusive. The successful high-speed cell sorting of trophic and cystic forms is paving the way for the elucidation of the complex Pneumocystis life cycle. The growth of each sorted Pneumocystis stage population was followed up independently both in nude rats and in vitro. In addition, by setting up a novel nude rat model, we attempted to delineate which cystic and/or trophic forms can be naturally aerially transmitted from host to host. The results showed that in axenic culture, cystic forms can differentiate into trophic forms, whereas trophic forms are unable to evolve into cystic forms. In contrast, nude rats inoculated with pure trophic forms are able to produce cystic forms and vice versa. Transmission experiments indicated that 12 h of contact between seeder and recipient nude rats was sufficient for cystic forms to be aerially transmitted. In conclusion, trophic- to cystic-form transition is a key step in the proliferation of Pneumocystis microfungi because the cystic forms (but not the trophic forms) can be transmitted by aerial route from host to host.

Evidence of airborne excretion of Pneumocystis carinii during infection in immunocompetent rats. Lung involvement and antibody response

To better understand the role of immunocompetent hosts in the diffusion of Pneumocystis in the environment, airborne shedding of Pneumocystis carinii in the surrounding air of experimentally infected Sprague Dawley rats was quantified by means of a real-time PCR assay, in parallel with the kinetics of P. carinii loads in lungs and specific serum antibody titres. Pneumocystis-free Sprague Dawley rats were intratracheally inoculated at day 0 (d0) and then followed for 60 days. P. carinii DNA was detected in lungs until d29 in two separate experiments and thereafter remained undetectable. A transient air excretion of Pneumocystis DNA was observed between d14 and d22 in the first experiment and between d9 and d19 in the second experiment; it was related to the peak of infection in lungs. IgM and IgG anti-P. carinii antibody increase preceded clearance of P. carinii in the lungs and cessation of airborne excretion. In rats receiving a second challenge 3 months after the first inoculation, Pneumocystis was only detected at a low level in the lungs of 2 of 3 rats at d2 post challenge and was never detected in air samples. Anti-Pneumocystis antibody determinations showed a typical secondary IgG antibody response. This study provides the first direct evidence that immunocompetent hosts can excrete Pneumocystis following a primary acquired infection. Lung infection was apparently controlled by the immune response since fungal burdens decreased to become undetectable as specific antibodies reached high titres in serum. This immune response was apparently protective against reinfection 3 months later.

BCG induces protection against Mycobacterium tuberculosis infection in the Wistar rat model

Our understanding of the correlation of Mycobacterium bovis Bacille Calmette-Guerin (BCG)-mediated immune responses and protection against Mycobacterium tuberculosis (Mtb) infection is still limited. We have recently characterized a Wistar rat model of experimental tuberculosis (TB). In the present study, we evaluated the efficacy of BCG vaccination in this model. Upon Mtb challenge, BCG vaccinated rats controlled growth of the bacilli earlier than unvaccinated rats. Histopathology analysis of infected lungs demonstrated a reduced number of granulomatous lesions and lower parenchymal inflammation in vaccinated animals. Vaccine-mediated protection correlated with the rapid accumulation of antigen specific CD4⁺ and CD8⁺ T cells in the infected lungs. Immunohistochemistry further revealed higher number of CD8⁺ cells in the pulmonary granulomas of vaccinated animals. Evaluation of pulmonary immune responses in vaccinated and Mtb infected rats by real time PCR at day 15 post-challenge showed reduced expression of genes responsible for negative regulation of Th1 immune responses. Thus, early protection observed in BCG vaccinated rats correlated with a similarly timed shift of immunity towards the Th1 type response. Our data support the importance of (i) the Th1-Th2 balance in the control of mycobacterial infection and (ii) the value of the Wistar rats in understanding the biology of TB.

Ploidy of cell-sorted trophic and cystic forms of Pneumocystis carinii

Once regarded as an AIDS-defining illness, Pneumocystis pneumonia (PcP) is nowadays prevailing in immunocompromised HIV-negative individuals such as patients receiving immunosuppressive therapies or affected by primary immunodeficiency. Moreover, Pneumocystis clinical spectrum is broadening to non-severely-immunocompromised subjects who could be colonized by the fungus while remaining asymptomatic for PcP, thus being able to transmit the infection by airborne route to susceptible hosts. Although the taxonomical position of the Pneumocystis genus has been clarified, several aspects of its life cycle remain elusive such as its mode of proliferation within the alveolus or its ploidy level. As no long-term culture model exists to grow Pneumocystis organisms in vitro, an option was to use a model of immunosuppressed rat infected with Pneumocystis carinii and sort life cycle stage fractions using a high-through-put cytometer. Subsequently, ploidy levels of the P. carinii trophic and cystic form fractions were measured by flow cytometry. In the cystic form, eight contents of DNA were measured thus strengthening the fact that each mature cyst contains eight haploid spores. Following release, each spore evolves into a trophic form. The majority of the trophic form fraction was haploid in our study. Some less abundant trophic forms displayed two contents of DNA indicating that they could undergo (i) mating/fusion leading to a diploid status or (ii) asexual mitotic division or (iii) both. Even less abundant trophic forms with four contents of DNA were suggestive of mitotic divisions occurring following mating in diploid trophic forms. Of interest, was the presence of trophic forms with three contents of DNA, an unusual finding that could be related to asymmetrical mitotic divisions occurring in other fungal species to create genetic diversity at lower energetic expenses than mating. Overall, ploidy data of P. carinii life cycle stages shed new light on the complexity of its modes of proliferation.

Experimental tuberculosis in the Wistar rat: a model for protective immunity and control of infection

Background

Despite the availability of many animal models for tuberculosis (TB) research, there still exists a need for better understanding of the quiescent stage of disease observed in many humans. Here, we explored the use of the Wistar rat model for the study of protective immunity and control of Mycobacterium tuberculosis (Mtb) infection.

Methodology/Principal Findings

The kinetics of bacillary growth, evaluated by the colony stimulating assay (CFU) and the extent of lung pathology in Mtb infected Wistar rats were dependent on the virulence of the strains and the size of the infecting inoculums. Bacillary growth control was associated with induction of T helper type 1 (Th1) activation, the magnitude of which was also Mtb strain and dose dependent. Histopathology analysis of the infected lungs demonstrated the formation of well organized granulomas comprising epithelioid cells, multinucleated giant cells and foamy macrophages surrounded by large numbers of lymphocytes. The late stage subclinical form of disease was reactivated by immunosuppression leading to increased lung CFU.

Conclusion

The Wistar rat is a valuable model for better understanding host-pathogen interactions that result in control of Mtb infection and potentially establishment of latent TB. These properties together with the ease of manipulation, relatively low cost and well established use of rats in toxicology and pharmacokinetic analyses make the rat a good animal model for TB drug discovery.

Pneumocystis: from a doubtful unique entity to a group of highly diversified fungal species

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

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.

Pneumocystis oryctolagisp. nov., an uncultured fungus causing pneumonia in rabbits at weaning: review of current knowledge, and description of a new taxon on genotypic, phylogenetic and phenotypic bases

The genus Pneumocystis comprises noncultivable, highly diversified fungal pathogens dwelling in the lungs of mammals. The genus includes numerous host-species-specific species that are able to induce severe pneumonitis, especially in severely immunocompromised hosts. Pneumocystis organisms attach specifically to type-1 epithelial alveolar cells, showing a high level of subtle and efficient adaptation to the alveolar microenvironment. Pneumocystis species show little difference at the light microscopy level but DNA sequences of Pneumocystis from humans, other primates, rodents, rabbits, insectivores and other mammals present a host-species-related marked divergence. Consistently, selective infectivity could be proven by cross-infection experiments. Furthermore, phylogeny among primate Pneumocystis species was correlated with the phylogeny of their hosts. This observation suggested that cophylogeny could explain both the current distribution of pathogens in their hosts and the speciation. Thus, molecular, ultrastructural and biological differences among organisms from different mammals strengthen the view of multiple species existing within the genus Pneumocystis. The following species were subsequently described: Pneumocystis jirovecii in humans, Pneumocystis carinii and Pneumocystis wakefieldiae in rats, and Pneumocystis murina in mice. The present work focuses on Pneumocystis oryctolagi sp. nov. from Old-World rabbits. This new species has been described on the basis of both biological and phylogenetic species concepts.

Molecular typing of Pneumocystis jirovecii found in formalin-fixed paraffin-embedded lung tissue sections from sudden infant death victims

Previous studies have provided histological evidence of an association between primary Pneumocystis infection and sudden infant death syndrome (SIDS). The aim of this work was to determine the species of clustered Pneumocystis organisms found in formalin-fixed paraffin-embedded (FFPE) lung tissue sections from Chilean sudden infant death (SID) victims. This approach needed first to optimize a DNA extraction method from such histological sections. For that purpose, the QIAamp DNA Isolation from Paraffin-Embedded Tissue method (Qiagen) was first tested on FFPE lung tissue sections of immunosuppressed Wistar rats inoculated with rat-derived PNEUMOCYSTIS: Successful DNA extraction was assessed by the amplification of a 346 bp fragment of the mitochondrial large subunit rRNA gene of the Pneumocystis species using a previously described PCR assay. PCR products were analysed by direct sequencing and sequences corresponding to Pneumocystis carinii were found in all the samples. This method was then applied to FFPE lung tissue sections from Chilean SID victims. Pneumocystis jirovecii was successfully identified in the three tested samples. In conclusion, an efficient protocol for isolating PCR-ready DNA from FFPE lung tissue sections was developed. It established that the Pneumocystis species found in the lungs of Chilean SID victims was P. jirovecii.

Expression and complexity of the PRT1 multigene family of Pneumocystis carinii

Pneumocystis carinii has a multigene family, PRT1, that encodes proteins with homology to KEX2-like proteases. PRT1 genes cluster with MSG genes near the telomeres and, like MSG, PRT1 proteins seem to be surface-expressed. The clustering of PRT1 and MSG genes suggested that expression of the two multigene families might be coordinated. Studying gene expression in P. carinii has been hampered by the lack of a culture system, and by lack of clonality in P. carinii populations in naturally infected rats, the host of this fungus. Heterogeneity can be reduced, however, by low-dose intratracheal inoculation, which can produce P. carinii populations dominated by organisms derived from a single progenitor. To study PRT1 expression, nude rats were inoculated with approximately 10 P. carinii each. The clonality of the P. carinii populations from inoculated rats was assessed by analysis of the UCS locus, a site in the genome that is known to be very heterogeneous in naturally infected rats, but nearly homogeneous in rats infected by low-dose intratracheal inoculation. Each of the populations had the same MSG gene at the UCS locus in at least 80 % of the organisms. To investigate PRT1 gene expression, RNA was amplified using primers that amplify numerous PRT1 genes. Seventy-four cloned cDNAs were sequenced, including at least 12 clones from each population of P. carinii. Many differently expressed PRT1 sequences were identified in each population, and a total of 45 different sequences were detected. However, the same PRT1 sequence was present in 15 of 74 plasmids and was found in 3 of the 5 P. carinii populations, suggesting that some PRT1 genes may be either more commonly expressed or expressed at a higher level. These data show that many members of the PRT1 gene family can be expressed in populations of P. carinii derived from few progenitors and suggest that the regulation of this family is different from that governing expression of the MSG gene family.

Potent genotoxic activity of benzo[a]pyrene coated onto hematite measured by unscheduled DNA synthesis in vivo in the rat

Since epidemiological studies have firmly implicated co-exposure to iron oxides and polycyclic aromatic hydrocarbons as a potential etiological factor involved in the excess mortality due to lung cancer in miners, experimental studies have been performed to investigate the role of iron particles in benzo[a]pyrene (B[a]P)-induced lung pathogenesis. In a previous study using the Comet assay in vivo in the rat, we demonstrated that iron particles enhanced B[a]P genotoxicity. To determine whether co-exposure (B[a]P/iron oxides) induces a real genotoxic activity or is only due to inhibition of DNA repair, the unscheduled DNA synthesis (UDS) assay was implemented in vivo in the rat. The UDS assay was used to measure DNA repair in two cell types (lung cells and hepatocytes) of OFA Sprague-Dawley rats, 24 h after endotracheal administration of a single dose of an iron oxide (hematite, Fe2O3) (0.75 mg), of B[a]P (0.75 mg) or of B[a]P (0.75 mg) coated on hematite particles (0.75 mg). No difference in UDS was observed in the two organs investigated in rats treated with iron oxide alone compared with control animals, while a significant increase in UDS was observed in lungs and liver of rats treated with B[a]P alone compared with control animals. The main finding was a significant increase in UDS observed in both lung and liver cells of rats treated with B[a]P coated on hematite when compared with those treated with B[a]P alone. The current study demonstrates (i) that iron particles did not inhibit UDS in lung cells and hepatocytes of OFA Sprague-Dawley treated rats with B[a]P coated on hematite and (ii) a potent genotoxic activity of co-exposure to B[a]P coated on hematite. Therefore, our data may contribute to explaining the excess mortality due to lung cancer in epidemiological studies and overall why exposure to B[a]P coated on Fe2O3 particles resulted in a higher tumor incidence in rodents compared with exposure to B[a]P alone.

Activation of the respiratory burst by Pneumocystis carinii. Efficiency of different antibody isotypes, complement, lung surfactant protein D, and mannan-binding lectin

The effect of opsonization of Pneumocystis carinii with different antibody classes, complement, mannan-binding lectin (MBL), and lung surfactant protein D (SP-D) on respiratory burst activation was studied. Antibodies were obtained by affinity chromatography, complement from a hypogammaglobulinaemic patient, and phagocytic cells from blood donors. Respiratory burst activation was measured by chemiluminescence (CL). With freshly isolated neutrophils the combination of antibodies and complement but not antibody alone, had opsonizing properties. With neutrophils cultured for 20 h, however, IgG increased the CL response. In macrophages P. carinii opsonized with IgG alone induced a CL response proportional to the antibody titre used. With IgA an effect, albeit lower, was also seen, whereas IgM alone was inefficient. The combined effect of antibodies and complement increased the response significantly for all three antibody classes, IgG and complement giving the largest response. Binding of MBL to P. carinii and Candida albicans was demonstrated; however, only the former stimulated activation of the respiratory burst. SP-D did not bind to either microorganism and had no effect on the respiratory burst. It is concluded that IgG, IgA and complement are important opsonizing factors in infections involving P. carinii. The relative importance varies with the type of phagocytic cell studied.

Therapeutic efficacies of GW471552 and GW471558, two new azasordarin derivatives, against pneumocystosis in two immunosuppressed-rat models

Two new azasordarins, GW471552 and GW471558, were studied in vivo for treatment of Pneumocystis carinii pneumonia. In the Wistar rat spontaneous pneumonia model, both azasordarins significantly reduced the number of P. carinii cysts per gram of lung homogenate when administered at 1 mg/kg of body weight twice a day for 10 days. In a nude rat inoculation model, both compounds showed therapeutic efficacy at 0.25 mg/kg twice a day for 10 days.

Pneumocystis carinii f. sp. hominis is not infectious for SCID mice

The infectious power of Pneumocystis carinii f. sp. hominis was explored by inoculating SCID mice intranasally with either P. carinii f. sp. hominis or P. carinii f. sp. muris isolates. Only mice inoculated with mouse parasites developed Pneumocystis pneumonia, as assessed by microscopy and PCR. These results suggest that humans do not contract pneumocystosis from animals.

Transmission of Pneumocystis carinii disease from immunocompetent contacts of infected hosts to susceptible hosts

Pneumocystis carinii organisms constitute a large group of heterogeneous atypical microscopic fungi that are able to infect immunocompromised mammals by an airborne route and to proliferate in their lungs, inducing Pneumocystis carinii pneumonia. This pneumonia remains a crucial epidemiological challenge, since neither the source of Pneumocystis carinii infection in humans nor the process by which humans become infected has been clearly established. Polymerase chain reaction (PCR) assays have shown that profoundly immunosuppressed patients without pneumocystosis can be subclinically infected with Pneumocystis. Other PCR-based studies have suggested that healthy immunocompetent hosts are not latent carriers of the parasite. However, recent reports have indicated that Pneumocystis carinii can persist for limited periods in the lungs of convalescent rats after recovery from corticosteroid-induced pneumocystosis, and also that immunocompetent mammals can be transiently parasitized by Pneumocystis carinii after close contact with hosts with Pneumocystis carinii pneumonia. Can transiently parasitized hosts be a source of infection for immunosuppressed hosts? In order to investigate this important clinical question, the ability of immunocompetent BALB/c mice, which were carrying subclinical levels of Pneumocystis carinii, to transmit the infection by the airborne route to highly susceptible, uninfected mice with severe combined immunodeficiency was studied. The results indicated that the immunocompetent mice, transiently parasitized by Pneumocystis carinii organisms after close contact with Pneumocystis carinii-infected mice, were able to transmit the infection to Pneumocystis carinii-free mice with severe combined immunodeficiency.

In vitro pharmacodynamic parameters of sordarin derivatives in comparison with those of marketed compounds against Pneumocystis carinii isolated from rats

Pneumocystis carinii pneumonia remains one of the most serious complications of immunosuppressed patients. In this study, the in vitro pharmacodynamic parameters of four sordarin derivatives (GM 191519, GM 237354, GM 193663, and GM 219771) have been evaluated by a new quantitative approach and compared with the commercially available drugs pentamidine, atovaquone, and trimethoprim-sulfamethoxazole (TMP-SMX). In vitro activities and in vivo therapeutic efficacies of sordarin derivatives against P. carinii were also evaluated. In vitro activity was determined by the broth microdilution technique, comparing the total number of microorganisms in treated and drug-free cultures by using Giemsa staining. The in vitro maximum effect (E(max)), the drug concentrations to reach 50% of E(max) (EC(50)), and the slope of the dose-response curve were then estimated by the Hill equation (E(max) sigmoid model). Sordarin derivatives were the most potent agents against P. carinii, with EC(50)s of 0.00025, 0.0007, 0.0043, and 0. 025 microg/ml for GM 191519, GM 237354, GM 193663, and GM 219771, respectively. The EC(50)s of pentamidine, atovaquone, and TMP-SMX were 0.025, 0.16, and 26.7/133.5 microg/ml, respectively. The results obtained with this approach showed GM 237354 and GM 191519 to be approximately 35- and 100-fold more active in vitro than pentamidine, the most active marketed compound. All sordarin derivatives tested were at least 5,000-fold more active in vitro than TMP-SMX. The three sordarin derivatives tested in vivo-GM 191519, GM 237354, and GM 219771-showed a marked therapeutic efficacy, defined as reduction of cyst forms per gram of lung. GM 191519 was the most potent (daily dose reducing 50% of the P. carinii burden in the lungs [ED(50)], 0.05 mg/kg/day) followed by GM 237354 and GM 219771 (ED(50)s, 0.30 and 0.49 mg/kg/day, respectively). Good agreement between in vitro parameters and in vivo outcome was obtained when P. carinii pneumonia in rats was treated with sordarin derivatives.

Animal models of pneumocystosis

As in vitro culture systems allowing to isolate Pneumocystis samples from patients or other mammal hosts are still not available, animal models have critical importance in Pneumocystis research. The parasite was reported in numerous mammals but P. carinii pneumonia (PCP) experimental models were essentially developed by using rats, mice, rabbits and ferrets. The rat treated with corticosteroids for 9-12 weeks is a useful PCP model. Like laboratory rats, conventional mice develop PCP after prolonged corticosteroid administration. The ferret (Mustela putorius furo) also develop PCP under corticosteroid regime. Whilst bronchoalveolar lavage (BAL) is really difficult to perform on live laboratory rodents, serial BAL sampling can be performed on live ferrets. Rabbits currently develop spontaneous PCP at weaning without corticosteroid administration. For this reason this model has been used for studying the host immune response as well as Pneumocystis-surfactant interactions. Pigs and horses also develop spontaneous PCP. Treated with corticosteroids, piglets develop extensive PCP and could be used as a non-rodent model. Pneumocystis was detected in many non-human primates. Primates could represent a source of parasites taxonomically related to P. carinii sp. f. hominis. Moreover, primates might be used as experimental hosts to human Pneumocystis. A marked variability of parasite levels among corticosteroid-treated animals and the fact that the origin of the parasite strain remains unknown, are important drawbacks of the corticosteroid-treated models. For these reasons, inoculated animal models of PCP were developed. The intratracheal inoculation of lung homogenates containing viable parasites in corticosteroid-treated non-latently infected rats resulted in extensive, reproducible Pneumocystis infections. Extensive PCP can be obtained within 5-7 weeks, whilst 9-12 weeks are needed in the classical model. The severe combined immunodeficiency (SCID) mouse inoculated by nasal route and the athymic nude rats intratracheally inoculated were used to test the infectivity of Pneumocystis samples coming from cultures or from different hosts. They were also used to test the anti-Pneumocystis activity of antimicrobial molecules.

Morphological and ultrastructural methods for Pneumocystis

Pneumocystis is a eukaryotic unicellular microorganism with marked fungal affinities. All known life cycle stages of this parasite were observed in the lung of mammals. The cystic forms of this microorganism may be observed microscopically by using stains with affinity for the components of their relatively thick cell wall. However, about 100 years ago they were observed for the first time thanks to panoptic stains which do not stain their cell wall. Methanol-Giemsa technique as well as Giemsa-like rapid stainings are often used to reveal vegetative or cystic forms of this parasite on air dried smears of clinical or experimental samples. For many years, hypotheses on its life cycle, which remains unknown, were based on transmission electron microscopy (TEM) studies. However, only for the last years progresses in the quality of fixation for TEM led to a better understanding of the Pneumocystis cell structure. In this chapter, strategies to reveal Pneumocystis organisms in clinical or experimental specimens by using light microscopy, as well as techniques allowing a good preparation of parasitic samples for TEM, are given and shortly discussed.

Current in vitro culture systems for Pneumocystis

Although Pneumocystis continuous culture systems have not yet been developed, efficient short-term in vitro methods allowing the production of infectious forms of Pneumocystis can now be employed. The quality of the inoculum will influence the in vitro development of P. carinii. For this reason, efficient extraction and cryopreservation techniques are considered in this section. In vitro growth and limited passage were obtained by inoculating freshly extracted parasites onto fibroblast- or epithelial-like cell monolayers cultivated in ordinary tissue culture flasks, culture plates, microcarrier beads or other culture devices. Cultures were usually maintained in an atmosphere of 5% CO2 at 35-37 degrees C. The results obtained in these different systems were surprisingly similar: the number of parasites increased about 6-10 times within the first 3-4 days post-inoculation, then remained stationary until day 7-14 and decreased rapidly. If passages were attempted, the growth decreased gradually and no growth was recorded after 2-3 passages. Proof of the in vitro Pneumocystis attachment to feeder cells has been furnished by electron microscopy. Two currently used feeder cell culture systems were selected in this subchapter. The first system is a co-culture of monolayer lung epithelial-like cells with Pneumocystis. After trypsin treatment and passage of cells with attached parasites to culture bottles containing fresh medium, 3 or more new culture bottles can be plated. A 2-4-fold increase in parasite number can be obtained but, interestingly, cultured parasites were more infectious to the nude rat than freshly extracted lung parasites. In the second system, the spinner flask culture method, Pneumocystis is cultivated on cell coated microbeads in slow stirring vessels, in order to exploit the beads' huge surface where microorganisms can transiently adhere and grow and from where they can be easily detached by simply leaving the beads to settle down. This culture system has ensured 10(8)-10(9) viable trophozoites in each harvest after 7-10 days of slow stirring incubation.

Evaluation of drug efficacy by using animal models or in vitro systems

The efficacy of most therapeutic and prophylactic protocols against Pneumocystis carinii pneumonia used in human patients has been tested in animal models, especially in the corticosteroid-treated rat. The advantages and drawbacks of this model have been examined in brief in Chapter 1 of this section. More recently, the nude rat, intratracheally inoculated with Pneumocystis, was used to test new anti-microbian molecules for their anti-Pneumocystis activity. In vitro systems, co-cultures of Pneumocystis with feeder cells as well as axenic cultures, were also used many times for drug screening. In this paper, the most used in vivo or in vitro drug screening systems are described. Moreover, as immunocompromised individuals, AIDS patients, especially, are often infected simultaneously by several infectious agents, a recent co-infection model is described.

Cultured rat and purified human Pneumocystis carinii stimulate intra- but not extracellular free radical production in human neutrophils

The production of free radicals in human neutrophils was studied in both Pneumocystis carinii derived from cultures of L2 rat lung epithelial-like cells and Pneumocystis carinii purified from human lung. Using the cytochrome C technique, which selectively measured extracellular superoxide generation, hardly any free radical production was observed after stimulation with cultured rat-derived P. carinii. A chemiluminescence technique, which separately measured intra- and extracellular free radical production, was subsequently employed to differentiate the free radical generation. It was established that 1) P. carinii stimulated intra- but not extracellular free radical production in human neutrophils, 2) opsonized cultured rat-derived P. carinii stimulated human neutrophils to a strong intracellular response of superoxide production, and 3) opsonized P. carinii, purified from human lung also stimulated human neutrophils to produce intracellular free radicals.

Different ultrastructural morphology of Pneumocystis carinii derived from mice, rats, and rabbits

Pneumocystis carinii (PC) is a fungus present in the lungs of many mammal species. Even though studies of the genome, the isoenzymes, and the antigens have proved some host-species-linked heterogeneity, the existence of distinct Pneumocystis species or subspecies has still not been accepted. Comparative studies of the ultrastructural morphology of pneumocysts derived from several host species may support evidence of host-species-linked heterogeneity. We have compared the ultrastructural morphology of pneumocysts derived from mice, rats, and rabbits. The density of membrane-limited electron-dense cytoplasmic granules was found to be higher in mouse-derived pneumocysts than in rabbit-derived pneumocysts, and furthermore the average diameter of the granules from mouse pneumocysts was larger than that of granules from rabbit-derived pneumocysts. The average diameter of the filopodia of mouse-derived pneumocysts was smaller than that of filopodia from rat-derived pneumocysts, which was smaller than that of filopodia from rabbit-derived pneumocysts. Globular electron-dense bulbous dilatations at the tip of the filopodia were described for the first time and they were only found on filopodia of mouse-derived pneumocysts. These distinct host-species-linked morphological differences of pneumocysts from mouse, rat, and rabbit may support previous biochemical data indicating the existence of different Pneumocystis species or subspecies.

Surfactant changes during experimental pneumocystosis are related to Pneumocystis development

Pneumocystosis-related surfactant changes have been reported in both humans and corticosteroid-treated experimental hosts. As corticosteroids induce an increase in pulmonary surfactant, some findings could be considered as controversial. The aim of this study was to investigate whether the surfactant composition changes during experimental pneumocystosis were related to the Pneumocystis development. In this work two corticosteroid-untreated animal models were used: rabbits, which develop spontaneous pneumocystosis at weaning; and severe combined immunodeficiency mice, which were intranasally inoculated with Pneumocystis carinii. Surfactant phospholipid and protein content was explored by bronchoalveolar lavage. The in vitro effect of surfactant on P. carinii growth was also explored. In the two models, the surfactant phospholipid/protein ratio was significantly increased, whereas parasite rates were low. This ratio decreases with the slope increase of the parasite growth curve. These early surfactant changes suggested that Pneumocystis proliferation requires alveolar lining fluid changes, and that normal surfactant is not suitable for parasite development. In this way, in vitro experiments presented here have revealed an inhibitory effect of synthetic or seminatural surfactants on the P. carinii growth. Further studies are needed to determine how Pneumocystis induces the reported early modifications of the surfactant, and why the parasite development is inhibited by pulmonary surfactant.

Surfactant changes during experimental pneumocystosis are related to Pneumocystis development

Pneumocystosis-related surfactant changes have been reported in both humans and corticosteroid-treated experimental hosts. As corticosteroids induce an increase in pulmonary surfactant, some findings could be considered as controversial. The aim of this study was to investigate whether the surfactant composition changes during experimental pneumocystosis were related to the Pneumocystis development. In this work two corticosteroid-untreated animal models were used: rabbits, which develop spontaneous pneumocystosis at weaning; and severe combined immunodeficiency mice, which were intranasally inoculated with Pneumocystis carinii. Surfactant phospholipid and protein content was explored by bronchoalveolar lavage. The in vitro effect of surfactant on P. carinii growth was also explored. In the two models, the surfactant phospholipid/protein ratio was significantly increased, whereas parasite rates were low. This ratio decreases with the slope increase of the parasite growth curve. These early surfactant changes suggested that Pneumocystis proliferation requires alveolar lining fluid changes, and that normal surfactant is not suitable for parasite development. In this way, in vitro experiments presented here have revealed an inhibitory effect of synthetic or seminatural surfactants on the P. carinii growth. Further studies are needed to determine how Pneumocystis induces the reported early modifications of the surfactant, and why the parasite development is inhibited by pulmonary surfactant.