The Cryptococcus gattii species complex: Unique pathogenic yeasts with understudied virulence mechanisms

Primary cutaneous cryptococcosis - History, concepts, clinical and therapeutic update

Cryptococcosis is a disease caused by fungi of the genus Cryptococcus, with the species Cryptococcus neoformans and Cryptococcus gattii being recognized as pathogenic. Cutaneous cryptococcosis can be classified as "secondary", developing from a previous systemic disease, or, on the contrary, "primary", resulting from transcutaneous inoculation of the agent. It can also be classified as "disseminated cutaneous cryptococcosis", when there is an associated systemic disease, or "localized", when it is restricted to the skin. This article uses the term "primary cutaneous cryptococcosis" because it is the most widely used and already established in the literature. Historically, the first report of a possible case of primary cutaneous cryptococcosis (PCC) occurred in 1950 by Gancy WM and was published in the Archives of Dermatology and Syphilology. Subsequently, the rare and sporadic reports in the following decades were reviewed and reported in the 1985 publication by Baes & van Cutsen. However, the unequivocal acceptance of the existence of PCC as a distinct disease only occurred in 2003 with the publication by Neville S et al. of the French Cryptococcosis Study Group. The fundamental criterion established to consider it as PCC was the proven absence of systemic disease, whether pulmonary, in the CNS or other location at the time of diagnosis of the cutaneous condition, characterized by a single lesion and, mostly, in an exposed area. These and other clinical criteria, diagnostic confirmation, and therapeutic choice are discussed in detail in the full text.

Quantitative MRI of a Cerebral Cryptococcoma Mouse Model for In Vivo Distinction between Different Cryptococcal Molecular Types

The controversially discussed taxonomy of the Cryptococcus neoformans/Cryptococcus gattii species complex encompasses at least eight major molecular types. Cerebral cryptococcomas are a common manifestation of cryptococcal neurological disease. In this study, we compared neurotypical symptoms and differential neurovirulence induced by one representative isolate for each of the eight molecular types studied. We compared single focal lesions caused by the different isolates and evaluated the potential relationships between the fungal burden and properties obtained with quantitative magnetic resonance imaging (qMRI) techniques such as diffusion MRI, T2 relaxometry and magnetic resonance spectroscopy (MRS). We observed an inverse correlation between parametric data and lesion density, and we were able to monitor longitudinally biophysical properties of cryptococcomas induced by different molecular types. Because the MRI/MRS techniques are also clinically available, the same approach could be used to assess image-based biophysical properties that correlate with fungal cell density in lesions in patients to determine personalized treatments.

The WHO fungal priority pathogens list: a crucial reappraisal to review the prioritisation

In October, 2022, WHO published the first fungal priority pathogen list, which categorised 19 fungal entities into three priority groups (critical, high, and medium), for prioritisation of research efforts. The final ranking was determined via multiple criteria decision analysis, considering both research and development needs and perceived public health importance. In this Personal View, we discuss the positioning of the fungal pathogens, namely, Mucorales, Candida spp, Histoplasma spp, Coccidioides and Paracoccidioides spp, Fusarium spp, eumycetoma causative agents, Talaromyces marneffei, and Pneumocystis jirovecii, while expressing concerns about potential disparities between the WHO fungal priority pathogen list ranking and the actual disease burden associated with these pathogens. Finally, we propose a revised prioritisation list that also considers the regional disparities in the burden of fungal diseases.

"We've got to get out"-Strategies of human pathogenic fungi to escape from phagocytes

Human fungal pathogens are a deadly and underappreciated risk to global health that most severely affect immunocompromised individuals. A virulence attribute shared by some of the most clinically relevant fungal species is their ability to survive inside macrophages and escape from these immune cells. In this review, we discuss the mechanisms behind intracellular survival and elaborate how escape is mediated by lytic and non-lytic pathways as well as strategies to induce programmed host cell death. We also discuss persistence as an alternative to rapid host cell exit. In the end, we address the consequences of fungal escape for the host immune response and provide future perspectives for research and development of targeted therapies.

Models for Inducing Experimental Cryptococcosis in Mice

Cryptococcus neoformans and Cryptococcus gattii are the predominant etiological agents of cryptococcosis, a particularly problematic disease in immunocompromised individuals. The increased clinical use of immunosuppressive drugs, the inherent ability of Cryptococcus species to suppress and evade host immune responses, and the emergence of drug-resistant yeast support the need for model systems that facilitate the design of novel immunotherapies and antifungals to combat disease progression. The mouse model of cryptococcosis is a widely used system to study Cryptococcus pathogenesis and the efficacy of antifungal drugs in vivo. In this chapter, we describe three commonly used strategies to establish cryptococcosis in mice: intranasal, intratracheal, and intravenous inoculations. Also, we discuss the methodology for delivering drugs to mice via intraperitoneal injection.