Evolving Concepts of Pneumocystis Epidemiology, Host Specificity and Evolution

A special issue of Journal of Fungi (ISSN 2309-608X). This special issue belongs to the section "Fungal Pathogenesis and Disease Control".

Deadline for manuscript submissions: 31 July 2024 | Viewed by 7522

Special Issue Editors

Critical Care Medicine Department, NIH Clinical Center, National Institutes of Health (NIH), Bethesda, MD, USA
Interests: epidemiology and molecular biology of fungal pathogens; antigenic variation and immune evasion; host-pathogen interactions; drug resistance; molecular diagnosis; Pneumocystis

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Guest Editor
Critical Care Medicine Department, NIH Clinical Center, National Institutes of Health (NIH), Bethesda, MD, USA
Interests: mycology with focus on human pathogens; evolutionary cell biology; population genetics; host-pathogen interaction

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Guest Editor
Institute of Pathology, Department of Pathobiology, University of Veterinary Medicine Vienna, Vienna, Austria
Interests: pathology of infectious diseases with focus on viral, bacterial, and fungal infections of the respiratory tract of the pig; Pneumocystis in various mammal species; modern diagnostic methods in veterinary pathology

Special Issue Information

Dear Colleagues,

The WHO recently sounded the alarm, highlighting the rising threat of medically significant invasive fungal diseases worldwide, and released a list of 19 priority fungal pathogens, including Pneumocystis jirovecii, targeted for increased research. Since its first discovery in 1909, our understanding of Pneumocystis has undergone a dramatic evolution, including its taxonomic classification from a single protozoan species to a fungus of multiple species, its host range from only a few mammal species with no specificity to hundreds of mammal species with high specificity, and its pathogenic role from an obscure pathogen to a prominent cause of life-threatening pneumonia in immunocompromised patients.

Empowered by recent advances in genetics and genomics, our knowledge of Pneumocystis continues to evolve in various aspects, particularly in epidemiology, host specificity, and evolution. Some key evolving developments include frequent outbreaks of Pneumocystis pneumonia in transplant recipients, widespread colonization or subclinical infection in immunocompetent and immunodeficient hosts, growing incidence of coinfection of multiple Pneumocystis strains or species in the same host species, reduced host specificity of Pneumocystis among closely related host species, and discordant evolution of some Pneumocystis species with their host species.

The aim of this Special Issue is to foster and integrate scholarly contributions characterizing the new trend of Pneumocystis epidemiology in humans and animals (including laboratory, domesticated, and wild animals), demonstrating the changing pattern and molecular basis of host specificity of Pneumocystis and exploring the evolutionary dynamics of Pneumocystis from different host species.

Dr. Liang Ma
Dr. Ousmane H. Cissé
Dr. Christiane Weissenbacher-Lang
Guest Editors

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Keywords

  • Pneumocystis
  • epidemiology
  • host specificity
  • species evolution

Published Papers (4 papers)

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Research

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11 pages, 1058 KiB  
Article
A Novel CARMIL2 Immunodeficiency Identified in a Subset of Cavalier King Charles Spaniels with Pneumocystis and Bordetella Pneumonia
by Emily L. Coffey, Liang Ma, Ousmane H. Cissé, Joseph A. Kovacs, Katie M. Minor, Antti Sukura, Patrizia Danesi, Steven G. Friedenberg, Jonah N. Cullen, Christiane Weissenbacher-Lang, Julie C. Nadeau, Amber M. Graham, Martin N. Granick, Natalie K. Branson, Kyle C. Branson, Barbara Blasi, Casandra M. Jacobs and Eva Furrow
J. Fungi 2024, 10(3), 198; https://doi.org/10.3390/jof10030198 - 05 Mar 2024
Viewed by 1165
Abstract
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 [...] Read more.
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. Full article
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33 pages, 2574 KiB  
Article
Meta-Analysis and Systematic Literature Review of the Genus Pneumocystis in Pet, Farm, Zoo, and Wild Mammal Species
by Christiane Weissenbacher-Lang, Anna Grenl and Barbara Blasi
J. Fungi 2023, 9(11), 1081; https://doi.org/10.3390/jof9111081 - 04 Nov 2023
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Abstract
A systematic literature search on Pneumocystis in 276 pet, farm, zoo, and wild mammal species resulted in 124 publications originating from 38 countries that were analyzed descriptively and statistically, for which inclusion and exclusion criteria were exactly defined. The range of recorded Pneumocystis [...] Read more.
A systematic literature search on Pneumocystis in 276 pet, farm, zoo, and wild mammal species resulted in 124 publications originating from 38 countries that were analyzed descriptively and statistically, for which inclusion and exclusion criteria were exactly defined. The range of recorded Pneumocystis prevalence was broad, yet in half of the citations a prevalence of ≤25% was documented. Prevalence was significantly dependent on the method used for Pneumocystis detection, with PCR revealing the highest percentages. Pet animals showed the lowest median Pneumocystis prevalence, followed by farm, wild, and zoo animals. In contrast, pet and farm animals showed higher proportions of high-grade infection levels compared to zoo and wild mammals. Only in individual cases, all of them associated with severe Pneumocystis pneumonia, was an underlying immunosuppression confirmed. Acquired immunosuppression caused by other diseases was frequently discussed, but its significance, especially in highly immunosuppressive cases, needs to be clarified. This meta-analysis supported a potential influence of the social and environmental factors of the host on Pneumocystis transmission in wildlife, which must be further elucidated, as well as the genetic diversity of the fungus. Full article
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Review

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33 pages, 2203 KiB  
Review
Trends in the Epidemiology of Pneumocystis Pneumonia in Immunocompromised Patients without HIV Infection
by Ting Xue, Xiaomei Kong and Liang Ma
J. Fungi 2023, 9(8), 812; https://doi.org/10.3390/jof9080812 - 31 Jul 2023
Cited by 4 | Viewed by 2930
Abstract
The increasing morbidity and mortality of life-threatening Pneumocystis pneumonia (PCP) in immunocompromised people poses a global concern, prompting the World Health Organization to list it as one of the 19 priority invasive fungal diseases, calling for increased research and public health action. In [...] Read more.
The increasing morbidity and mortality of life-threatening Pneumocystis pneumonia (PCP) in immunocompromised people poses a global concern, prompting the World Health Organization to list it as one of the 19 priority invasive fungal diseases, calling for increased research and public health action. In response to this initiative, we provide this review on the epidemiology of PCP in non-HIV patients with various immunodeficient conditions, including the use of immunosuppressive agents, cancer therapies, solid organ and stem cell transplantation, autoimmune and inflammatory diseases, inherited or primary immunodeficiencies, and COVID-19. Special attention is given to the molecular epidemiology of PCP outbreaks in solid organ transplant recipients; the risk of PCP associated with the increasing use of immunodepleting monoclonal antibodies and a wide range of genetic defects causing primary immunodeficiency; the trend of concurrent infection of PCP in COVID-19; the prevalence of colonization; and the rising evidence supporting de novo infection rather than reactivation of latent infection in the pathogenesis of PCP. Additionally, we provide a concise discussion of the varying effects of different immunodeficient conditions on distinct components of the immune system. The objective of this review is to increase awareness and knowledge of PCP in non-HIV patients, thereby improving the early identification and treatment of patients susceptible to PCP. Full article
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9 pages, 653 KiB  
Review
Lung Epithelial Cell Line Immune Responses to Pneumocystis
by Theodore J. Kottom, Eva M. Carmona and Andrew H. Limper
J. Fungi 2023, 9(7), 729; https://doi.org/10.3390/jof9070729 - 06 Jul 2023
Viewed by 1387
Abstract
Pneumocystis sp. are fungal pathogens and members of the Ascomycota phylum. Immunocompetent individuals can readily eliminate the fungus, whereas immunocompromised individuals can develop Pneumocystis jirovecii pneumonia (PJP). Currently, over 500,000 cases occur worldwide, and the organism is listed on the recently released WHO [...] Read more.
Pneumocystis sp. are fungal pathogens and members of the Ascomycota phylum. Immunocompetent individuals can readily eliminate the fungus, whereas immunocompromised individuals can develop Pneumocystis jirovecii pneumonia (PJP). Currently, over 500,000 cases occur worldwide, and the organism is listed on the recently released WHO fungal priority pathogens list. Overall, the number of PJP cases over the last few decades in developed countries with the use of highly effective antiretroviral therapy has decreased, but the cases of non-HIV individuals using immunosuppressive therapies have significantly increased. Even with relatively effective current anti-Pneumocystis therapies, the mortality rate remains 30–60% in non-HIV patients and 10–20% during initial episodes of PJP in HIV/AIDS patients. Although the role of alveolar macrophages is well studied and established, there is also well-established and emerging evidence regarding the role of epithelial cells in the immune response to fungi. This mini review provides a brief overview summarizing the innate immune response of the lung epithelium and various continuously cultured mammalian cell lines to Pneumocystis. Full article
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