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Recently light pollution has been one of the most dynamically increasing form of environmental pollution. Light, if it arrives at the wrong place, time, quantity and quality, is harmful to human health and the physical environment-not to mention that it is a mere waste of energy. The brightness of the sky above Pécs was measured by SQM-L instruments in 2011 and 2019. Maps of the different neighbourhoods with different levels of light pollution have been prepared. In addition, special VIIRS day/night band satellite images were also analysed using QGIS software. Our investigations coincided with the modernization of street lighting in the city. The impact of LED illuminators installed along main roads in Pécs was observed locally.

Antibody responses against lytic and latent Kaposi sarcoma (KS)-associated herpesvirus antigens were investigated in patients with KS, multicentric Castleman disease (MCD), and primary effusion lymphoma. Antibodies against the lytic antigen K8.1 were 5-fold higher in patients with MCD than those with KS, whereas antibodies to the sum of latent antigens v-cyclin and LANA were 27-fold higher in patients with KS, compared with patients with MCD (P < 001). The sum of anti-v-cyclin and anti-LANA antibody titers discriminated patients with KS from those with MCD and KS with 93% sensitivity and 83% specificity. These results suggest that antibody responses to lytic and latent KS-associated herpesvirus antigens differ in these diseases. [ABSTRACT FROM AUTHOR]

2009 marks the 100th anniversary of the first description of Pneumocystis, an organism that was ignored for much of its first 50 years but that has subsequently been recognized as an important pathogen of immunocompromised patients, especially patients infected with human immunodeficiency virus (HIV). We present a patient with chronic lymphocytic leukemia who died from Pneumocystis pneumonia (PCP) despite appropriate anti-Pneumocystis therapy. Although substantial advances in diagnosis, treatment, and prevention of PCP have decreased its frequency and improved prognosis, PCP continues to be seen in both HIV-infected patients and patients receiving immunosuppressive medications. Pneumocystis species comprise a family of fungi, each of which appears to be able to infect only 1 host species. Pneumocystis has a worldwide distribution. Immunocompetent hosts clear infection without obvious clinical consequences. Pneumocystis has been identified in patients with other diseases such as chronic obstructive pulmonary disease, although its clinical impact is uncertain. Immunocompromised patients develop disease as a consequence of reinfection and possibly reactivation of latent infection. In patients with HIV infection, the CD4 count is predictive of the risk for developing PCP, but such reliable markers are not available for other immunocompromised populations. In the majority of patients with PCP, multiple Pneumocystis strains can be identified using recently developed typing techniques. Because Pneumocystis cannot be cultured, diagnosis relies on detection of the organism by colorimetric or immunofluorescent stains or by polymerase chain reaction. Trimethoprim-sulfamethoxazole is the preferred drug regimen for both treatment and prevention of PCP, although a number of alternatives are also available. Corticosteroids are an important adjunct for hypoxemic patients. [ABSTRACT FROM AUTHOR]

Background. Intermittent interleukin (IL)-2 administration to human immunodeficiency virus (HIV)-infected patients leads to CD4(+) T cell expansions. The factors potentially affecting these expansions were investigated in the present study.Methods. A matched (for baseline CD4(+) T cell count) case-control study was designed. Nonresponders (NRs) were defined as patients with a /=50% increase in CD4(+) T cell count at week 24. Immunophenotype, Ki67 and forkhead box protein P3 (FoxP3) expression, and T cell receptor excision circle (TREC) measurements in T cells were evaluated at weeks 0 and 24 in both groups.Results. Control subjects and NRs did not differ significantly at baseline in age, viral load, CD4(+) T cell count, nadir CD4(+) T cell count, or CD8(+) T cell count. At week 0, NRs had lower TREC levels per 1x106 T cells and higher levels of T cell proliferation and activation than did control subjects. At week 24, both groups experienced decreases in T cell proliferation and increases in CD25 and FoxP3 expression on CD4(+) T cells, with TREC levels per 1x106 CD4(+) T cells decreasing significantly only in control subjects.Conclusions. Increased immune activation can adversely affect CD4(+) T cell expansions after IL-2 administration. Despite the lack of expansion, other evidence of IL-2-induced biological activity was observed. This article is in the public domain, and no copyright is claimed. [ABSTRACT FROM AUTHOR]

Over the past 10 years, in conjunction with the broad availability of potent antiretroviral regimens, the care of human immunodeficiency virus (HIV)-infected patients has shifted from prevention and treatment of opportunistic infections and malignancies to management of the metabolic and related complications associated with HIV infection and its treatment. Metabolic disorders, including lipodystrophy, dyslipidemia, and insulin resistance, occur at a high rate in HIV-infected individuals receiving highly active antiretroviral therapy (HAART). These disorders are associated with increased risk of cardiovascular disease and have become an important cause of morbidity and mortality in HIV-infected patients. Herein, we present the case of a patient with HIV infection who responded well to HAART but developed multiple complications potentially related to this therapy. This article reviews the clinical characteristics of the metabolic and skeletal disturbances observed in HIV infection and discusses strategies for their management. [ABSTRACT FROM AUTHOR]

Objective: To determine if physical examination can identify avascular necrosis of the hip (AVN) in asymptomatic HIV-infected patients.Design: Prospective, blinded population studyResults: Ten of the 176 patients were positive for AVN by MRI. Four subjects had unilateral disease and six had bilateral disease. Five hips (1.4%) in four patients were indeterminate. We evaluated physical examination maneuvers both singly and in combination. Tests done singly generally provided a higher degree of specificity (67-92%) but sensitivities were lower (0-50%) with all p-values S0.08. Positive predictive values based on physical exam, were <17% and negative predictive values were >90% for any single test. Combining all tests gave a high sensitivity (88%) and negative predictive value (98%), but low specificity (34%) and positive predictive value (6%) with p = 0.10. Only two of 16 hips with positive MRI findings showed no abnormalities when all tests were combinedConclusions: This study establishes the limited usefulness of a detailed physical examination of the hip early in the course of AVN. Patients who test negative on physical exam are unlikely to have AVN positive by MRI. Positive findings on physical examination of the hip may help identify patients who need further evaluation by MRI based on overall clinical suspicion. [ABSTRACT FROM AUTHOR]

CD40-CD40 ligand interactions are critical for controlling Pneumocystis infection. However, which CD40-expressing cell populations are important for this interaction have not been well defined. We used a cohousing mouse model of Pneumocystis infection, combined with flow cytometry and quantitative polymerase chain reaction, to examine the ability of different populations of cells from C57BL/6 mice to reconstitute immunity in CD40 knockout mice. Unfractionated splenocytes, as well as purified B cells, were able to control Pneumocystis infection, while B cell-depleted splenocytes and unstimulated bone marrow-derived dendritic cells were unable to control infection in CD40 knockout mice. Pneumocystis antigen-pulsed bone marrow-derived dendritic cells showed early but limited control of infection. Additional findings were consistent with recent studies that suggested a role for antigen presentation by B cells; specifically, by using cells from immunized animals, B cells were able to present Pneumocystis antigens to induce proliferation of T cells. Thus, CD40 expression by B cells appears necessary for robust immunity to Pneumocystis., Competing Interests: Potential conflicts of interest. All authors: No reported conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest., (Published by Oxford University Press on behalf of Infectious Diseases Society of America 2024.)

Background: Limited data are available describing the effects of SARS-CoV-2 breakthrough infections on the plasma proteome., Methods: PCR-positive SARS-CoV-2 patients, enrolled in a natural history study, underwent analysis of the plasma proteome. A prospective cohort of 66 unvaccinated and 24 vaccinated persons with different degrees of infection severity were evaluated acutely (within 40 days of symptom onset), and at three and ten months. Comparisons based on vaccination status alone and unsupervised hierarchical clustering were performed. A second cohort of vaccinated Omicron patients were evaluated acutely and at ten months., Results: Acutely, unvaccinated patients manifested overexpression of proteins involved in immune and inflammatory responses, while vaccinated patients exhibited adaptive immune responses without significant inflammation. At three and ten months, only unvaccinated patients had diminished but sustained inflammatory (C3b, CCL15, IL17RE) and immune responses (DEFA5,TREM1). Both groups had underexpression of pathways essential for cellular function, signaling, and angiogenesis (AKT1, MAPK14, HSPB1) across phases. Unsupervised clustering, based on protein expression, identified four groups of patients with variable vaccination rates demonstrating that additional clinical factors influence the plasma proteome. The proteome of vaccinated Omicron patients did not differ from vaccinated pre-Omicron patients., Conclusions: Vaccination attenuates the inflammatory response to SARS-CoV-2 infection across phases. However, at ten months after symptom onset, changes in the plasma proteome persist in both vaccinated and unvaccinated individuals, which may be relevant to post-acute sequelae of SARS-CoV-2 and other viral infections associated with post-acute infection syndromes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Huapaya, Gairhe, Kanth, Tian, Demirkale, Regenold, Sun, Lynch, Luo, Forsberg, Dewar, Rehman, Li, Krack, Kuruppu, Aboye, Barnett, Strich, Davey, Childs, Chertow, Kovacs, Torabi-Parizi and Suffredini.)

CD4+ T cells are critical to control of Pneumocystis infection, and Cxcr6 has been shown to be upregulated in these cells during infection, but the roles of CD4 and Cxcr6 in this setting are undefined. To explore this, mice deficient in CD4 or Cxcr6 expression were utilized in a co-housing mouse model that mimics the natural route of Pneumocystis infection. Organism load and anti-Pneumocystis antibodies were assayed over time, and immunohistochemistry, flow cytometry, and quantitative PCR were used to characterize host immune responses during infection. CD4 was found to be necessary for clearance of Pneumocystis murina, though partial control was seen in it's absence; based on ThPOK expression, double negative T cells with T helper cell characteristics may be contributing to this control. Using a Cxcr6 deficient mouse expressing gfp, control of infection in the absence of Cxcr6 was similar to that in heterozygous control mice. It is noteworthy that gfp + cells were seen in the lungs with similar frequencies between the 2 strains. Interferon-ɣ and chemokine/ligands Cxcr3, Cxcl9, and Cxcl10 increased during P. murina infection in all models. Thus, CD4, but not Cxcr6, is needed for clearance of P. murina infection., Competing Interests: Declaration of competing interest The authors have no conflicting financial interests., (Published by Elsevier Masson SAS.)

In order to assess homeostatic mechanisms in the lung after COVID-19, changes in the protein signature of bronchoalveolar lavage from 45 patients with mild to moderate disease at three phases (acute, recovery, and convalescent) are evaluated over a year. During the acute phase, inflamed and uninflamed phenotypes are characterized by the expression of tissue repair and host defense response molecules. With recovery, inflammatory and fibrogenic mediators decline and clinical symptoms abate. However, at 9 months, quantified radiographic abnormalities resolve in the majority of patients, and yet compared to healthy persons, all showed ongoing activation of cellular repair processes and depression of the renin-kallikrein-kinin, coagulation, and complement systems. This dissociation of prolonged reparative processes from symptom and radiographic resolution suggests that occult ongoing disruption of the lung proteome is underrecognized and may be relevant to recovery from other serious viral pneumonias., Competing Interests: Declaration of interests The authors declare no competing interests., (Published by Elsevier Inc.)

Converting triplet dioxygen into a powerful oxidant is fundamentally important to life. The study reported herein quantitatively examines the formation of a well-characterized, reactive, O 2 -derived thiolate ligated Fe III -superoxo using low-temperature stopped-flow kinetics. Comparison of the kinetic barriers to the formation of this species via two routes, involving either the addition of (a) O 2 to [Fe II (S 2 Me2 N 3 (Pr,Pr))] (1) or (b) superoxide to [Fe III (S 2 Me2 N 3 (Pr,Pr))] + (3) is shown to provide insight into the mechanism of O 2 activation. Route (b) was shown to be significantly slower, and the kinetic barrier 14.9 kJ mol -1 higher than route (a), implying that dioxygen activation involves inner-sphere, as opposed to outer sphere, electron transfer from Fe(ii). H-bond donors and ligand constraints are shown to dramatically influence O 2 binding kinetics and reversibility. Dioxygen binds irreversibly to [Fe II (S 2 Me2 N 3 (Pr,Pr))] (1) in tetrahydrofuran, but reversibly in methanol. Hydrogen bonding decreases the ability of the thiolate sulfur to stabilize the transition state and the Fe III -superoxo, as shown by the 10 kJ mol -1 increase in the kinetic barrier to O 2 binding in methanol vs. tetrahydrofuran. Dioxygen release from [Fe III (S 2 Me2 N 3 (Pr,Pr))O 2 ] (2) is shown to be 24 kJ mol -1 higher relative to previously reported [Fe III (S Me2 N 4 (tren))(O 2 )] + (5), the latter of which contains a more flexible ligand. These kinetic results afford an experimentally determined reaction coordinate that illustrates the influence of H-bonding and ligand constraints on the kinetic barrier to dioxygen activation an essential step in biosynthetic pathways critical to life., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

SUMMARYEvery human being is presumed to be infected by the fungus Pneumocystis jirovecii at least once in his or her lifetime. This fungus belongs to a large group of species that appear to exclusively infect mammals, with P. jirovecii being the only one known to cause disease in humans. The mystery of P. jirovecii origin and speciation is just beginning to unravel. Here, we provide a review of the major steps of P. jirovecii evolution. The Pneumocystis genus likely originated from soil or plant-associated organisms during the period of Cretaceous ~165 million years ago and successfully shifted to mammals. The transition coincided with a substantial loss of genes, many of which are related to the synthesis of nutrients that can be scavenged from hosts or cell wall components that could be targeted by the mammalian immune system. Following the transition, the Pneumocystis genus cospeciated with mammals. Each species specialized at infecting its own host. Host specialization is presumably built at least partially upon surface glycoproteins, whose protogene was acquired prior to the genus formation. P. jirovecii appeared at ~65 million years ago, overlapping with the emergence of the first primates. P. jirovecii and its sister species P. macacae , which infects macaques nowadays, may have had overlapping host ranges in the distant past. Clues from molecular clocks suggest that P. jirovecii did not cospeciate with humans. Molecular evidence suggests that Pneumocystis speciation involved chromosomal rearrangements and the mounting of genetic barriers that inhibit gene flow among species., Competing Interests: The authors declare no conflict of interest.

A subset of antiretroviral therapy-treated persons with human immunodeficiency virus (HIV), referred to as immunological nonresponders (INRs), fails to normalize CD4+ T-cell numbers. In a case-control study involving 26 INRs (CD4 < 250 cells/µL) and 25 immunological responders (IRs; CD4 ≥ 250 cells/µL), we evaluated the potential contribution of transcriptionally competent defective HIV-1 proviruses to poor CD4+ T-cell recovery. Compared to the responders, the INRs had higher levels of cell-associated HIV RNA (P = .034) and higher percentages of HLA-DR+ CD4+ T cells (P < .001). While not encoding replication-competent viruses, the RNA transcripts frequently encoded HIV-1 Gag-p17 and Nef proteins. These transcripts and/or resulting proteins may activate pathway(s) leading to the immunological nonresponse phenotype., Competing Interests: Potential conflicts of interest . J. A. K. and H. C. L. are investigators on a clinical trial of pembrolizumab being conducted under a Cooperative Research and Development Agreement between the NIH and Merck Sharp & Dohme Corp. J. A. K. is a principal investigator of a Cooperative Research and Development Agreement between the NIH and Matinas BioPharma Holdings, Inc to develop encochleated medications. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (Published by Oxford University Press on behalf of Infectious Diseases Society of America 2024.)

Despite its ubiquitous infectivity to mammals with strong host specificity, our current knowledge about Pneumocystis has originated from studies of merely 4% of extant mammalian species. Further studies of Pneumocystis epidemiology across a broader range of animal species require the use of assays with high sensitivity and specificity. To this end, we have developed multiple universal Pneumocystis primers targeting different genetic loci with high amplification efficiency. Application of these primers to PCR investigation of Pneumocystis in free-living hares ( Lepus townsendii , n = 130) and rabbits ( Oryctolagus cuniculus , n = 8) in Canada revealed a prevalence of 81% (105/130) and 25% (2/8), respectively. Genotyping analysis identified five and two variants of Pneumocystis from hares and rabbits, respectively, with significant sequence divergence between the variants from hares. Based on phylogenetic analysis using nearly full-length sequences of the mitochondrial genome, nuclear rRNA operon and dihydropteroate synthase gene for the two most common variants, Pneumocystis in hares and rabbits are more closely related to each other than either are to Pneumocystis in other mammals. Furthermore, Pneumocystis in both hares and rabbits are more closely related to Pneumocystis in primates and dogs than to Pneumocystis in rodents. The high prevalence of Pneumocystis in hares ( P. sp. ' townsendii ') suggests its widespread transmissibility in the natural environment, similar to P. oryctolagi in rabbits. The presence of multiple distinct Pneumocystis populations in hares contrasts with the lack of apparent intra-species heterogeneity in P. oryctolagi , implying a unique evolution history of P. sp. ' townsendii ' in hares.

Centromeres are constricted chromosomal regions that are essential for cell division. In eukaryotes, centromeres display a remarkable architectural and genetic diversity. The basis of centromere-accelerated evolution remains elusive. Here, we focused on Pneumocystis species, a group of mammalian-specific fungal pathogens that form a sister taxon with that of the Schizosaccharomyces pombe , an important genetic model for centromere biology research. Methods allowing reliable continuous culture of Pneumocystis species do not currently exist, precluding genetic manipulation. CENP-A, a variant of histone H3, is the epigenetic marker that defines centromeres in most eukaryotes. Using heterologous complementation, we show that the Pneumocystis CENP-A ortholog is functionally equivalent to CENP-A Cnp1 of S. pombe . Using organisms from a short-term in vitro culture or infected animal models and chromatin immunoprecipitation (ChIP)-Seq, we identified CENP-A bound regions in two Pneumocystis species that diverged ~35 million years ago. Each species has a unique short regional centromere (<10 kb) flanked by heterochromatin in 16-17 monocentric chromosomes. They span active genes and lack conserved DNA sequence motifs and repeats. These features suggest an epigenetic specification of centromere function. Analysis of centromeric DNA across multiple Pneumocystis species suggests a vertical transmission at least 100 million years ago. The common ancestry of Pneumocystis and S. pombe centromeres is untraceable at the DNA level, but the overall architectural similarity could be the result of functional constraint for successful chromosomal segregation.IMPORTANCE Pneumocystis species offer a suitable genetic system to study centromere evolution in pathogens because of their phylogenetic proximity with the non-pathogenic yeast S. pombe , a popular model for cell biology. We used this system to explore how centromeres have evolved after the divergence of the two clades ~ 460 million years ago. To address this question, we established a protocol combining short-term culture and ChIP-Seq to characterize centromeres in multiple Pneumocystis species. We show that Pneumocystis have short epigenetic centromeres that function differently from those in S. pombe ., Competing Interests: The authors declare no conflict of interest.

Pet dogs are a valuable natural animal model for studying relationships between primary immunodeficiencies and susceptibility to Pneumocystis and other opportunistic respiratory pathogens. Certain breeds, such as the Cavalier King Charles Spaniel, are over-represented for Pneumocystis pneumonia (PCP), suggesting the presence of a primary immunodeficiency in the breed. Here, we report the discovery of a CARMIL2 nonsense variant in three Cavalier King Charles Spaniel dogs with either PCP (n = 2) or refractory Bordetella pneumonia (n = 1). CARMIL2 encodes a protein that plays critical roles in T-cell activation and other aspects of immune function. Deleterious CARMIL2 variants have recently been reported in human patients with PCP and other recurrent pneumonias. In addition to opportunistic respiratory infection, the affected dogs also exhibited other clinical manifestations of CARMIL2 deficiencies that have been reported in humans, including early-onset gastrointestinal disease, allergic skin disease, mucocutaneous lesions, abscesses, autoimmune disorders, and gastrointestinal parasitism. This discovery highlights the potential utility of a natural canine model in identifying and studying primary immunodeficiencies in patients affected by PCP.

Background: Once-weekly isoniazid with rifapentine (HP) for 3 months is a recommended treatment for latent tuberculosis infection in persons with HIV. HP reduces exposures of certain antiretroviral medications, resulting in limited options for the concomitant use of these therapies. Here, we examined the pharmacokinetics (PK), safety, and tolerability of darunavir/cobicistat with HP., Methods: This was an open-label, fixed sequence, two-period crossover study in persons without HIV. Participants received darunavir 800 mg/cobicistat 150 mg once-daily alone for 4 days, then continued darunavir/cobicistat once-daily for days 5-19 with HP coadministration on days 5, 12, and 19. Intensive PK assessments were performed on days 4, 14, and 19. PK parameters were determined using noncompartmental methods. Geometric mean ratios with 90% confidence intervals (CIs) were calculated and compared between phases using mixed-effects models., Results: Thirteen participants were enrolled. Two withdrew after day 4, and one withdrew after day 14. Of the 3 withdrawals, 2 were attributed to drug-related adverse events. Darunavir area under the concentration-time curve, maximum concentrations (Cmax), and concentrations at 24 hours postdose (C24h) were reduced by 71%, 41%, and 96% ∼48-72 hours after HP administration (day 14), respectively, and 36%, 17%, and 89% with simultaneous HP administration (day 19), respectively. On day 14, 45% of the predose and 73% of C24h concentrations were below the darunavir EC50 (0.055 µg/mL)., Conclusions: Darunavir exposures were significantly decreased with HP coadministration. Temporal relationships between HP coadministration and the extent of induction or mixed inhibition/induction of darunavir metabolism were apparent. Coadministration of darunavir/cobicistat with 3HP should be avoided., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Pneumocystis jirovecii pneumonia (PCP) is one of the most frequent opportunistic infections in people with HIV (PWH). However, there are limited data on long-term outcomes of PCP in the antiretroviral therapy (ART) era., Methods: We conducted a secondary analysis of 2 prospective studies on 307 PWH, 81 with prior PCP, with a median follow-up of 96 weeks. Laboratory data were measured at protocol-defined intervals. We reviewed clinically indicated chest computerized tomography imaging in 63 patients with prior PCP at a median of 58 weeks after PCP diagnosis and pulmonary function tests (PFTs) of patients with (n = 10) and without (n = 14) prior PCP at a median of 18 weeks after ART initiation., Results: After 96 weeks of ART, PWH with prior PCP showed no significant differences in laboratory measurements, including CD4 count, when compared with those without prior PCP. Survival rates following ART initiation were similar. However, PWH with prior PCP had increased evidence of restrictive lung pathology and diffusion impairment in PFTs. Furthermore, on chest imaging, 13% of patients had bronchiectasis and 11% had subpleural cysts. Treatment with corticosteroids was associated with an increased incidence of cytomegalovirus disease (odds ratio, 2.62; P = .014)., Conclusions: PCP remains an important opportunistic infection in the ART era. While it did not negatively affect CD4 reconstitution, it could pose an increased risk for incident cytomegalovirus disease with corticosteroid treatment and may cause residual pulmonary sequelae. These findings suggest that PCP and its treatment may contribute to long-term morbidity in PWH, even in the ART era., Competing Interests: Potential conflicts of interest. The authors: no reported conflicts of interest., (Published by Oxford University Press on behalf of Infectious Diseases Society of America 2023.)

Background: Data on cellular immune responses in persons with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection following vaccination are limited. The evaluation of these patients with SARS-CoV-2 breakthrough infections may provide insight into how vaccinations limit the escalation of deleterious host inflammatory responses., Methods: We conducted a prospective study of peripheral blood cellular immune responses to SARS-CoV-2 infection in 21 vaccinated patients, all with mild disease, and 97 unvaccinated patients stratified based on disease severity., Results: We enrolled 118 persons (aged 50 years [SD 14.5 years], 52 women) with SARS-CoV-2 infection. Compared to unvaccinated patients, vaccinated patients with breakthrough infections had a higher percentage of antigen-presenting monocytes (HLA-DR+), mature monocytes (CD83+), functionally competent T cells (CD127+), and mature neutrophils (CD10+); and lower percentages of activated T cells (CD38+), activated neutrophils (CD64+), and immature B cells (CD127+CD19+). These differences widened with increased disease severity in unvaccinated patients. Longitudinal analysis showed that cellular activation decreased over time but persisted in unvaccinated patients with mild disease at 8-month follow-up., Conclusions: Patients with SARS-CoV-2 breakthrough infections exhibit cellular immune responses that limit the progression of inflammatory responses and suggest mechanisms by which vaccination limits disease severity. These data may have implications for developing more effective vaccines and therapies. Clinical Trials Registration. NCT04401449., Competing Interests: Potential conflicts of interest. All authors: No reported conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (Published by Oxford University Press on behalf of Infectious Diseases Society of America 2023.)

Background: Toxoplasmic encephalitis (TE) is a life-threatening complication of people with human immunodeficiency virus (PWH) with severe immunodeficiency, especially those with a CD4 + T-cell count <100 cells/µL. Following a clinical response to anti- Toxoplasma therapy, and immune reconstitution after initiation of combination antiretroviral therapy (ART), anti- Toxoplasma therapy can be discontinued with a low risk of relapse., Methods: To better understand the evolution of magnetic resonance imaging (MRI)-defined TE lesions in PWH receiving ART, we undertook a retrospective study of PWH initially seen at the National Institutes of Health between 2001 and 2012, who had at least 2 serial MRI scans. Lesion size and change over time were calculated and correlated with clinical parameters., Results: Among 24 PWH with TE and serial MRI scans, only 4 had complete clearance of lesions at the last MRI (follow-up, 0.09-5.8 years). Of 10 PWH off all anti- Toxoplasma therapy (median, 3.2 years after TE diagnosis), 6 had persistent MRI enhancement. In contrast, all 5 PWH seen in a pre-ART era study who were followed for >6 months had complete clearance of lesions. TE lesion area at diagnosis was associated with the absolute change in area ( P < .0001)., Conclusions: Contrast enhancement can persist even when TE has been successfully treated and anti- Toxoplasma therapy has been stopped, highlighting the need to consider diagnostic alternatives in successfully treated patients with immune reconstitution presenting with new neurologic symptoms., Competing Interests: Potential conflicts of interest. All authors: No reported conflicts., (Published by Oxford University Press on behalf of Infectious Diseases Society of America 2023.)

Pneumocystis spp. are thought to adapt to the lungs of potentially all mammals. However, the full host range, fungal burden and severity of infection are unknown for many species. In this study, lung tissue samples originating from 845 animals of 31 different families of eight mammal orders were screened by in situ hybridization (ISH) using a universal 18S rRNA probe for Pneumocystis , followed by hematoxylin and eosin (H&E) staining for determining histopathological lesions. A total of 216 (26%) samples were positive for Pneumocystis spp., encompassing 36 of 98 investigated mammal species, with 17 of them being described for the first time for the presence of Pneumocystis spp. The prevalence of Pneumocystis spp. as assessed by ISH varied greatly among different mammal species while the organism load was overall low, suggesting a status of colonization or subclinical infection. Severe Pneumocystis pneumonia seemed to be very rare. For most of the Pneumocystis -positive samples, comparative microscopic examination of H&E- and ISH-stained serial sections revealed an association of the fungus with minor lesions, consistent with an interstitial pneumonia. Colonization or subclinical infection of Pneumocystis in the lung might be important in many mammal species because the animals may serve as a reservoir.

Pneumocystis is a fungal pathogen that can cause pneumonia in immunosuppressed hosts and subclinical infection in immunocompetent hosts. Mucosal-associated invariant T (MAIT) cells are unconventional lymphocytes with a semi-invariant T-cell receptor that are activated by riboflavin metabolites that are presented by the MHC-1b molecule MR1. Although Pneumocystis can presumably synthesize riboflavin metabolites based on whole-genome studies, the role of MAIT cells in controlling Pneumocystis infection is unknown. We used a co-housing mouse model of Pneumocystis infection, combined with flow cytometry and qPCR, to characterize the response of MAIT cells to infection in C57BL/6 mice, and, using MR1 -/- mice, which lack MAIT cells, to examine their role in clearing the infection. MAIT cells accumulated in the lungs of C57BL/6 mice during Pneumocystis infection and remained at increased levels for many weeks after clearance of infection. In MR1 -/- mice, Pneumocystis infection was cleared with kinetics similar to C57BL/6 mice. Thus, MAIT cells are not necessary for control of Pneumocystis infection, but the prolonged retention of these cells in the lungs following clearance of infection may allow a more rapid future response to other pathogens.

Herein, we examine the electronic and geometric structural properties of O 2 -derived aliphatic thiolate-ligated Fe-peroxo, Fe-hydroxo, and Fe(IV) oxo compounds. The latter cleaves strong C-H bonds (96 kcal mol -1 ) on par with the valine C-H bond cleaved by isopencillin N synthase (IPNS). Stopped-flow kinetics studies indicate that the barrier to O 2 binding to [Fe II (S Me2 N 4 (tren))] + ( 3 ) is extremely low ( E a = 36(2) kJ mol -1 ), as theoretically predicted for IPNS. Dioxygen binding to 3 is shown to be reversible, and a superoxo intermediate, [Fe III (S Me2 N 4 (tren))(O 2 )] + ( 6 ), forms in the first 25 ms of the reaction at -40 °C prior to the rate-determining ( E a = 46(2) kJ mol -1 ) formation of peroxo-bridged [(S Me2 N 4 (tren))Fe(III)] 2 (μ-O 2 ) 2+ ( 7 ). A log( k obs ) vs log([Fe]) plot for the formation of 7 is consistent with the second-order dependence on iron, and H 2 O 2 assays are consistent with a 2:1 ratio of Fe/H 2 O 2 . Peroxo 7 is shown to convert to ferric-hydroxo [Fe III (S Me2 N(tren))(OH)] + ( 9 , g ⊥ = 2.24, g ∥ = 1.96), the identity of which was determined via its independent synthesis. Rates of the conversion 7 → 9 are shown to be dependent on the X-H bond strength of the H-atom donor, with a k H / k D = 4 when CD 3 OD is used in place of CH 3 OH as a solvent. A crystallographically characterized cis thiolate-ligated high-valent iron oxo, [Fe IV (O)(S Me2 N 4 (tren))] + ( 11 ), is shown to form en route to hydroxo 9 . Electronic structure calculations were shown to be consistent with 11 being an S = 1 Fe(IV)═O with an unusually high ν Fe-O stretching frequency at 918 cm -1 in line with the extremely short Fe-O bond (1.603(7) Å).

Background: Pneumocystis jirovecii is an opportunistic fungus that causes Pneumocystis pneumonia (PCP) in immunocompromised hosts. Over an 11-month period, we observed a rise in cases of PCP among kidney-transplant recipients (KTR), prompting an outbreak investigation., Methods: Clinical and epidemiologic data were collected for KTR diagnosed with PCP between July 2019 and May 2020. Pneumocystis strain typing was performed using restriction fragment length polymorphism analyses and multilocus sequence typing in combination with next-generation sequencing. A transmission map was drawn, and a case-control analysis was performed to determine risk factors associated with PCP., Results: Nineteen cases of PCP in KTR were diagnosed at a median of 79 months post-transplantation; 8 received monthly belatacept infusions. Baseline characteristics were similar for KTR on belatacept versus other regimens; the number of clinic visits was numerically higher for the belatacept group during the study period (median 7.5 vs 3). Molecular typing of respiratory specimens from 9 patients revealed coinfection with up to 7 P. jirovecii strains per patient. A transmission map suggested multiple clusters of interhuman transmission. In a case-control univariate analysis, belatacept, lower absolute lymphocyte count, non-White race, and more transplant clinic visits were associated with an increased risk of PCP. In multivariate and prediction power estimate analyses, frequent clinic visits was the strongest risk factor for PCP., Conclusions: Increased clinic exposure appeared to facilitate multiple clusters of nosocomial PCP transmission among KTR. Belatacept was a risk factor for PCP, possibly by increasing clinic exposure through the need for frequent visits for monthly infusions., (© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

Reported herein is the structural, spectroscopic, redox, and reactivity properties of a series of iron complexes containing both a π-donating thiolate, and π-accepting N -heterocycles in the coordination sphere, in which we systematically vary the substituents on the N -heterocycle, the size of the N -heterocycle, and the linker between the imine nitrogen and tertiary amine nitrogen. In contrast to our primary amine/thiolate-ligated Fe(II) complex, [Fe II (S Me2 N 4 (tren))] + ( 1 ), the Fe(II) complexes reported herein are intensely colored, allowing us to visually monitor reactivity. Ferrous complexes with R = H substituents in the 6-position of the pyridines, [Fe II (S Me2 N 4 (6-H-DPPN)] + ( 6 ) and [Fe II (S Me2 N 4 (6-H-DPEN))(MeOH)] + ( 8-MeOH ) are shown to readily bind neutral ligands, and all of the Fe(II) complexes are shown to bind anionic ligands regardless of steric congestion. This reactivity is in contrast to 1 and is attributed to an increased metal ion Lewis acidity assessed via aniodic redox potentials, E p,a , caused by the π-acid ligands. Thermodynamic parameters (ΔH, ΔS) for neutral ligand binding were obtained from T -dependent equilibrium constants. All but the most sterically congested complex, [Fe II (S Me2 N 4 (6-Me-DPPN)] + ( 5 ), react with O 2 . In contrast to our Mn(II)-analogues, dioxygen intermediates are not observed. Rates of formation of the final mono oxo-bridged products were assessed via kinetics and shown to be inversely dependent on redox potentials, E p,a , consistent with a mechanism involving electron transfer., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Although atovaquone is effective in treating and preventing Pneumocystis pneumonia (PCP), its use is limited by nonlinear absorption and adverse events. The current study was undertaken to examine the activity of encochleated atovaquone (eATQ), a novel lipid-crystal nanoparticle formulation, in a mouse model of PCP. eATQ 100-200 mg was superior to commercially available atovaquone at 14 days in decreasing total Pneumocystis nuclei and asci. eATQ plus anidulafungin reduced nuclei significantly better than commercial atovaquone plus anidulafungin. eATQ is a novel formulation of atovaquone that warrants further evaluation for treatment and prevention of PCP., (Published by Oxford University Press for the Infectious Diseases Society of America 2020.)

Superoxide (O 2 •- ) is a toxic radical, generated via the adventitious reduction of dioxygen (O 2 ), which has been implicated in a number of human disease states. Nonheme iron enzymes, superoxide reductase (SOR) and superoxide dismutase (SOD), detoxify O 2 •- via reduction to afford H 2 O 2 and disproportionation to afford O 2 and H 2 O 2 , respectively. The former contains a thiolate in the coordination sphere, which has been proposed to prevent O 2 •- oxidation to O 2 . The work described herein shows that, in contrast to this, oxidized thiolate-ligated [Fe III (S Me2 N 4 (tren)(THF)] 2+ ( 1 ox -THF ) is capable of oxidizing O 2 •- to O 2 . Coordinating anions, Cl - and OAc - , are shown to inhibit dioxygen evolution, implicating an inner-sphere mechanism. Previously we showed that the reduced thiolate-ligated [Fe II (S Me2 N 4 (tren))] + ( 1 ) is capable of reducing O 2 •- via a proton-dependent inner-sphere mechanism involving a transient Fe(III)-OOH intermediate. A transient ferric-superoxo intermediate, [Fe III (S Me2 N 4 (tren))(O 2 )] + ( 3 ), is detected by electronic absorption spectroscopy at -130 °C in the reaction between 1 ox -THF and KO 2 and shown to evolve O 2 upon slight warming to -115 °C. The DFT calculated O-O (1.306 Å) and Fe-O (1.943 Å) bond lengths of 3 are typical of ferric-superoxo complexes, and the time-dependent DFT calculated electronic absorption spectrum of 3 reproduces the experimental spectrum. The electronic structure of 3 is shown to consist of two antiferromagnetically coupled ( J calc = -180 cm -1 ) unpaired electrons, one in a superoxo π*(O-O) orbital and the other in an antibonding π*(Fe(d yz )-S(p y )) orbital.

The work described herein demonstrates the exquisite control that the inner coordination sphere of metalloenzymes and transition-metal complexes can have on reactivity. We report one of few crystallographically characterized Mn-peroxo complexes and show that the tight correlations between metrical and spectroscopic parameters, established previously by our group for thiolate-ligated RS-Mn(III)-OOR complexes, can be extended to include an alkoxide-ligated RO-Mn(III)-OOR complex. We show that the alkoxide-ligated RO-Mn(III)-OOR complex is an order of magnitude more stable ( t 1/2 298 K = 6730 s, k obs 298 K = 1.03 × 10 -4 s -1 ) than its thiolate-ligated RS-Mn(III)-OOR derivative ( t 1/2 293 K = 249 s, k 1 293 K = 2.78 × 10 -3 s -1 ). Electronic structure calculations provide insight regarding these differences in stability. The highest occupied orbital of the thiolate-ligated derivative possesses significant sulfur character and π-backdonation from the thiolate competes with π-backdonation from the peroxo π * (O-O). DFT-calculated Mulliken charges show that the Mn ion Lewis acidity of alkoxide-ligated RO-Mn(III)-OOR (+0.451) is greater than that of thiolate-ligated RS-Mn(III)-OOR (+0.306), thereby facilitating π-backdonation from the antibonding peroxo π*(O-O) orbital and increasing its stability. This helps to explain why the photosynthetic oxygen-evolving Mn complex, which catalyzes O-O bond formation as opposed to cleavage, incorporates O- and/or N-ligands as opposed to cys S-ligands.

Pneumocystis jirovecii, the fungal agent of human Pneumocystis pneumonia, is closely related to macaque Pneumocystis. Little is known about other Pneumocystis species in distantly related mammals, none of which are capable of establishing infection in humans. The molecular basis of host specificity in Pneumocystis remains unknown as experiments are limited due to an inability to culture any species in vitro. To explore Pneumocystis evolutionary adaptations, we have sequenced the genomes of species infecting macaques, rabbits, dogs and rats and compared them to available genomes of species infecting humans, mice and rats. Complete whole genome sequence data enables analysis and robust phylogeny, identification of important genetic features of the host adaptation, and estimation of speciation timing relative to the rise of their mammalian hosts. Our data reveals insights into the evolution of P. jirovecii, the sole member of the genus able to infect humans.

The addition of tert -butyl hydro-peroxide ( t BuOOH) to two structurally related Mn II complexes containing N,N -bis-(6-methyl-2-pyridyl-meth-yl)ethane-1,2-di-amine (6-Me-DPEN) and N,N -bis-(6-methyl-2-pyridyl-meth-yl)propane-1,2-di-amine (6-Me-DPPN) results in the formation of high-valent bis-oxo complexes, namely di-μ-oxido-bis-{[ N , N -bis-(6-methyl-2-pyridylmeth-yl)ethane-1,2-di-amine]-manganese(II)}( Mn - Mn ) bis-(tetra-phenyl-borate) dihydrate, [Mn(C 16 H 22 N 4 ) 2 O 2 ](C 24 H 20 B) 2 ·2H 2 O or {[Mn IV (N 4 (6-Me-DPEN))] 2 ( μ -O) 2 }(2BPh 4 )(2H 2 O) ( 1 ) and di-μ-oxido-bis-{[ N , N -bis-(6-methyl-2-pyridylmeth-yl)propane-1,3-di-amine]-manganese(II)}( Mn - Mn ) bis-(tetra-phenyl-borate) diethyl ether disolvate, [Mn(C 17 H 24 N 4 ) 2 O 2 ](C 24 H 20 B) 2 ·2C 4 H 10 O or {[Mn IV (N 4 (6-MeDPPN))] 2 ( μ -O) 2 }(2BPh 4 )(2Et 2 O) ( 2 ). Complexes 1 and 2 both contain the 'diamond core' motif found previously in a number of iron, copper, and manganese high-valent bis-oxo compounds. The flexibility in the propyl linker in the ligand scaffold of 2 , as compared to that of the ethyl linker in 1 , results in more elongated Mn-N bonds, as one would expect. The Mn-Mn distances and Mn-O bond lengths support an Mn IV oxidation state assignment for the Mn ions in both 1 and 2 . The angles around the Mn centers are consistent with the local pseudo-octa-hedral geometry., (© Coggins et al. 2020.)

Previous studies have shown that Pneumocystis binds to pneumocytes, but the proteins responsible for binding have not been well defined. Mucins are the major glycoproteins present in mucus, which serves as the first line of defence during airway infection. MUC1 is the best characterised membrane-tethered mucin and is expressed on the surface of most airway epithelial cells. Although by electron microscopy Pneumocystis primarily binds to type I pneumocytes, it can also bind to type II pneumocytes. We hypothesized that Pneumocystis organisms can bind to MUC1 expressed by type II pneumocytes. Overexpression of MUC1 in human embryonic kidney HEK293 cells increased Pneumocystis binding, while knockdown of MUC1 expression by siRNA in A549 cells, a human adenocarcinoma-derived alveolar type II epithelial cell line, decreased Pneumocystis binding. Immunofluorescence labelling indicated that MUC1 and Pneumocystis were co-localised in infected mouse lung tissue. Incubation of A549 cells with Pneumocystis led to phosphorylation of ERK1/2 that increased with knockdown of MUC1 expression by siRNA. Pneumocystis caused increased IL-6 and IL-8 secretion by A549 cells, and knockdown of MUC1 further increased their secretion in A549 cells. Taken together, these results suggest that binding of Pneumocystis to MUC1 expressed by airway epithelial cells may facilitate establishment of productive infection., (Published 2020. This article is a U.S. Government work and is in the public domain in the USA.)

Environmental exposure has a significant impact on human health. While some airborne fungi can cause life-threatening infections, the impact of environment on fungal spore dispersal and transmission is poorly understood. The democratization of shotgun metagenomics allows us to explore important questions about fungal propagation. We focus on Pneumocystis , a genus of host-specific fungi that infect mammals via airborne particles. In humans, Pneumocystis jirovecii causes lethal infections in immunocompromised patients if untreated, although its environmental reservoir and transmission route remain unclear. Here, we attempt to clarify, by analyzing human exposome metagenomic data sets, whether humans are exposed to different Pneumocystis species present in the air but only P. jirovecii cells are able to replicate or whether they are selectively exposed to P. jirovecii Our analysis supports the latter hypothesis, which is consistent with a local transmission model. These data also suggest that healthy carriers are a major driver for the transmission.

Pneumocystis , a major opportunistic pathogen in patients with a broad range of immunodeficiencies, contains abundant surface proteins encoded by a multicopy gene family, termed the major surface glycoprotein (Msg) gene superfamily. This superfamily has been identified in all Pneumocystis species characterized to date, highlighting its important role in Pneumocystis biology. In this report, through a comprehensive and in-depth characterization of 459 msg genes from 7 Pneumocystis species, we demonstrate, for the first time, the phylogeny and evolution of conserved domains in Msg proteins and provide a detailed description of the classification, unique characteristics, and phylogenetic relatedness of five Msg families. We further describe, for the first time, the relative expression levels of individual msg families in two rodent Pneumocystis species, the substantial variability of the msg repertoires in P. carinii from laboratory and wild rats, and the distinct features of the expression site for the classic msg genes in Pneumocystis from 8 mammalian host species. Our analysis suggests multiple functions for this superfamily rather than just conferring antigenic variation to allow immune evasion as previously believed. This study provides a rich source of information that lays the foundation for the continued experimental exploration of the functions of the Msg superfamily in Pneumocystis biology. IMPORTANCE Pneumocystis continues to be a major cause of disease in humans with immunodeficiency, especially those with HIV/AIDS and organ transplants, and is being seen with increasing frequency worldwide in patients treated with immunodepleting monoclonal antibodies. Annual health care associated with Pneumocystis pneumonia costs ∼$475 million dollars in the United States alone. In addition to causing overt disease in immunodeficient individuals, Pneumocystis can cause subclinical infection or colonization in healthy individuals, which may play an important role in species preservation and disease transmission. Our work sheds new light on the diversity and complexity of the msg superfamily and strongly suggests that the versatility of this superfamily reflects multiple functions, including antigenic variation to allow immune evasion and optimal adaptation to host environmental conditions to promote efficient infection and transmission. These findings are essential to consider in developing new diagnostic and therapeutic strategies.

A disease of more than 39.6 million people worldwide, HIV-1 infection has no curative therapy. To date, one man has achieved a sterile cure, with millions more hoping to avoid the potential pitfalls of lifelong antiretroviral therapy and other HIV-related disorders, including neurocognitive decline. Recent developments in immunotherapies and gene therapies provide renewed hope in advancing efforts toward a sterilizing or functional cure. On the horizon is research concentrated in multiple separate but potentially complementary domains: vaccine research, viral transcript editing, T-cell effector response targeting including checkpoint inhibitors, and gene editing. Here, we review the concept of targeting the HIV-1 tissue reservoirs, with an emphasis on the central nervous system, and describe relevant new work in functional cure research and strategies for HIV-1 eradication., (This is a work of the U.S. Government and is not subject to copyright protection in the United States. Foreign copyrights may apply.)

Herein we quantitatively investigate how metal ion Lewis acidity and steric properties influence the kinetics and thermodynamics of dioxygen binding versus release from structurally analogous Mn-O 2 complexes, as well as the barrier to Mn peroxo O-O bond cleavage, and the reactivity of Mn oxo intermediates. Previously we demonstrated that the steric and electronic properties of Mn III -OOR complexes containing N-heterocyclic (N Ar ) ligand scaffolds can have a dramatic influence on alkylperoxo O-O bond lengths and the barrier to alkylperoxo O-O bond cleavage. Herein, we examine the dioxygen reactivity of a new Mn II complex containing a more electron-rich, less sterically demanding N Ar ligand scaffold, and compare it with previously reported Mn II complexes. Dioxygen binding is shown to be reversible with complexes containing the more electron-rich metal ions. The kinetic barrier to O 2 binding and peroxo O-O bond cleavage is shown to correlate with redox potentials, as well as the steric properties of the supporting N Ar ligands. The reaction landscape for the dioxygen chemistry of the more electron-rich complexes is shown to be relatively flat. A total of four intermediates, including a superoxo and peroxo species, are observed with the most electron-rich complex. Two new intermediates are shown to form following the peroxo, which are capable of cleaving strong X-H bonds. In the absence of a sacrificial H atom donor, solvent, or ligand, serves as a source of H atoms. With TEMPOH as sacrificial H atom donor, a deuterium isotope effect is observed ( k H / k D = 3.5), implicating a hydrogen atom transfer (HAT) mechanism. With 1,4-cyclohexadiene, 0.5 equiv of benzene is produced prior to the formation of an EPR detected Mn III Mn IV bimetallic species, and 0.5 equiv after its formation.

BACKGROUNDHIV-infected patients with poor virologic control and multidrug-resistant virus have limited therapeutic options. The current study was undertaken to evaluate the safety, immunologic effects, and antiviral activity of peripheral lymphocytes transferred from an elite controller, whose immune system is able to control viral replication without antiretroviral medications, to an HLA-B*2705-matched progressor.METHODSApproximately 22 billion cells were collected from an elite controller by lymphapheresis and infused within 6 hours into a recipient with a preinfusion CD4+ T cell count of 10 cells/μL (1%) and HIV plasma viral load of 114,993 copies/mL.RESULTSDonor cells were cleared from the recipient's peripheral blood by day 8. A transient decrease in viral load to 58,421 (day 3) was followed by a rebound to 702,972 (day 6) before returning to baseline values by day 8. The decreased viral load was temporally associated with peak levels of donor T cells, including CD8+ T cells that had high levels of expression of Ki67, perforin, and granzyme B. Notably, recipient CD8+ T cells also showed increased expression of these markers, especially in HIV-specific tetramer-positive cells.CONCLUSIONThese results suggest that the adoptive transfer of lymphocytes from an HIV-infected elite controller to an HIV-infected patient with progressive disease may be able to perturb the immune system of the recipient in both positive and negative ways.TRIAL REGISTRATIONClinicalTrials.gov NCT00559416.FUNDINGIntramural Research Programs of the US NIH Clinical Center and the National Institute of Allergy and Infectious Diseases (NIAID); the National Cancer Institute.

In order to shed light on metal-dependent mechanisms for O-O bond cleavage, and its microscopic reverse, we compare herein the electronic and geometric structures of O 2 -derived binuclear Co(III)- and Mn(III)-peroxo compounds. Binuclear metal peroxo complexes are proposed to form as intermediates during Mn-promoted photosynthetic H 2 O oxidation, and a Co-containing artificial leaf inspired by nature's photosynthetic H 2 O oxidation catalyst. Crystallographic characterization of an extremely activated peroxo is made possible by working with substitution-inert, low-spin Co(III). Density functional theory (DFT) calculations show that the frontier orbitals of the Co(III)-peroxo compound differ noticeably from the analogous Mn(III)-peroxo compound. The highest occupied molecular orbital (HOMO) associated with the Co(III)-peroxo is more localized on the peroxo in an antibonding π*(O-O) orbital, whereas the HOMO of the structurally analogous Mn(III)-peroxo is delocalized over both the metal d-orbitals and peroxo π*(O-O) orbital. With low-spin d 6 Co(III), filled t 2g orbitals prevent π-back-donation from the doubly occupied antibonding π*(O-O) orbital onto the metal ion. This is not the case with high-spin d 4 Mn(III), since these orbitals are half-filled. This weakens the peroxo O-O bond of the former relative to the latter.

Glucan is the major cell wall component of Pneumocystis cysts. In the current study, we have characterized Pneumocystis Bgl2 (EC 3.2.1.58), an enzyme with glucanosyltransferase and β-1,3 endoglucanase activity in other fungi. Pneumocystis murina, Pneumocystis carinii, and Pneumocystis jirovecii bgl2 complementary DNA sequences encode proteins of 437, 447, and 408 amino acids, respectively. Recombinant P. murina Bgl2 expressed in COS-1 cells demonstrated β-glucanase activity, as shown by degradation of the cell wall of Pneumocystis cysts. It also cleaved reduced laminaripentaose and transferred oligosaccharides, resulting in polymers of 6 and 7 glucan residues, demonstrating glucanosyltransferase activity. Surprisingly, confocal immunofluorescence analysis of P. murina-infected mouse lung sections using an antibody against recombinant Bgl2 showed that the native protein is localized primarily to the trophic form of Pneumocystis in both untreated mice and mice treated with caspofungin, an antifungal drug that inhibits β-1,3-glucan synthase. Thus, like other fungi, Bgl2 of Pneumocystis has both endoglucanase and glucanosyltransferase activities. Given that it is expressed primarily in trophic forms, further studies are needed to better understand its role in the biology of Pneumocystis., (Published by Oxford University Press for the Infectious Diseases Society of America 2019.)

Herein, we describe an alkyl thiolate-ligated iron complex that reacts with dioxygen to form an unprecedented example of an iron superoxo (O 2 •- ) intermediate, [Fe III (S 2 Me2 N 3 (Pr,Pr))(O 2 )] (4), which is capable of cleaving strong C-H bonds. A cysteinate-ligated iron superoxo intermediate is proposed to play a key role in the biosynthesis of β-lactam antibiotics by isopenicillin N-synthase (IPNS). Superoxo 4 converts to a metastable putative Fe(III)-OOH intermediate, at rates that are dependent on the C-H bond strength of the H atom donor, with a kinetic isotope effect ( k H / k D = 4.8) comparable to that of IPNS ( k H / k D = 5.6). The bond dissociation energy of the C-H bonds cleaved by 4 (92 kcal/mol) is comparable to C-H bonds cleaved by IPNS (93 kcal/mol). Both the calculated and experimental electronic absorption spectra of 4 are comparable to those of the putative IPNS superoxo intermediate, and are shown to involve RS - → Fe-O 2 •- and O 2 •- → Fe charge transfer transitions. The π-back-donation by the electron-rich alkyl thiolate presumably facilitates this reactivity by increasing the basicity of the distal oxygen. The frontier orbitals of 4 are shown to consist of two strongly coupled unpaired electrons of opposite spin, one in a superoxo π*(O-O) orbital, and the other in an Fe(d xy ) orbital.