Pediatric Cryptococcal Lymphadenitis in the Absence of AIDS: Case Report and Literature Review

Use of Clinical Isolates to Establish Criteria for a Mouse Model of Latent Cryptococcus neoformans Infection

The mechanisms of latency in the context of C. neoformans infection remain poorly understood. Two reasons for this gap in knowledge are: 1) the lack of standardized criteria for defining latent cryptococcosis in animal models and 2) limited genetic and immunological tools available for studying host parameters against C. neoformans in non-murine models of persistent infection. In this study, we defined criteria required for latency in C. neoformans infection models and used these criteria to develop a murine model of persistent C. neoformans infection using clinical isolates. We analyzed infections with two clinical C. neoformans strains, UgCl223 and UgCl552, isolated from advanced HIV patients with cryptococcal meningitis. Our data show that the majority of C57BL/6 mice infected with the clinical C. neoformans isolates had persistent, stable infections with low fungal burden, survived beyond 90 days-post infection, exhibited weight gain, had no clinical signs of disease, and had yeast cells contained within pulmonary granulomas with no generalized alveolar inflammation. Infected mice exhibited stable relative frequencies of pulmonary immune cells during the course of the infection. Upon CD4+ T-cell depletion, the CD4DTR mice had significantly increased lung and brain fungal burden that resulted in lethal infection, indicating that CD4+ T-cells are important for control of the pulmonary infection and to prevent dissemination. Cells expressing the Tbet transcription factor were the predominant activated CD4 T-cell subset in the lungs during the latent infection. These Tbet-expressing T-cells had decreased IFNγ production, which may have implications in the capacity of the cells to orchestrate the pulmonary immune response. Altogether, these results indicate that clinical C. neoformans isolates can establish a persistent controlled infection that meets most criteria for latency; highlighting the utility of this new mouse model system for studies of host immune responses that control C. neoformans infections.

Dormancy in Cryptococcus neoformans: 60 years of accumulating evidence

Cryptococcus neoformans is an opportunistic yeast that is present worldwide and interacts with various organisms. In humans, it is responsible for cryptococcosis, a deadly invasive fungal infection that represents around 220,000 cases per year worldwide. Starting from the natural history of the disease in humans, there is accumulating evidence on the capacity of this organism to enter dormancy. In response to the harsh host environment, the yeast is able to adapt dramatically and escape the vigilance of the host's immune cells to survive. Indeed, the yeast exposed to the host takes on pleiotropic phenotypes, enabling the generation of populations in heterogeneous states, including dormancy, to eventually survive at low metabolic cost and revive in favorable conditions. The concept of dormancy has been validated in C. neoformans from both epidemiological and genotyping data, and more recently from the biological point of view with the characterization of dormancy through the description of viable but nonculturable cells.

Abdominal Lymphonodular Cryptococcosis in an Immunocompetent Child

We describe our experience with an apparently immunocompetent child presenting with pyrexia of unknown origin without focal signs. Investigations revealed lymphadenopathy at lung hila, mesentery, and porta hepatis. The child had received at least two months of empiric antituberculous therapy (ATT) before she came to us. A CT-guided biopsy revealed granulomatous inflammation. PAS stain showed yeasts which stained blue with Alcian blue, suggesting C. neoformans.

A Rare Case of Primary Supraclavicular Lymphadenitis due to Cryptococcus Neoformans in an HIV Infected Patient

Cryptococcosis caused by encapsulated yeast Cryptococcus neoformans most commonly presents as disease of the central nervous system. Cryptococcus is a non-mycelial budding yeast found in soil, pigeon droppings and their nesting places. The three 'classic' virulence factors of cryptococci are: polysaccharide capsule, melanin production and growth at 37°C. Here, we present a rare case of cryptococcosis affecting left supraclavicular lymph node in a Human Immunodeficiency virus (HIV) infected individual. Culture of fine needle aspirate of the lymph node yielded Cryptococcus neoformans which was identified by standard microbiological techniques. Meyer's mucicarmine stain imparted a typical rose burgundy colour to the capsule. Unusual characteristics of the isolate included poorly developed capsule and the presence of yeast in chains resembling pseudo-hyphae. This case highlights the importance of microbiological techniques for diagnosis and prompt treatment of cryptococcosis.