Fungal Cell Gigantism during Mammalian Infection

The interaction between fungal pathogens with the host frequently results in morphological changes, such as hyphae formation. The encapsulated pathogenic fungus Cryptococcus neoformans is not considered a dimorphic fungus, and is predominantly found in host tissues as round yeast cells. However, there is a specific morphological change associated with cryptococcal infection that involves an increase in capsule volume. We now report another morphological change whereby gigantic cells are formed in tissue. The paper reports the phenotypic characterization of giant cells isolated from infected mice and the cellular changes associated with giant cell formation. C. neoformans infection in mice resulted in the appearance of giant cells with cell bodies up to 30 µm in diameter and capsules resistant to stripping with γ-radiation and organic solvents. The proportion of giant cells ranged from 10 to 80% of the total lung fungal burden, depending on infection time, individual mice, and correlated with the type of immune response. When placed on agar, giant cells budded to produce small daughter cells that traversed the capsule of the mother cell at the speed of 20–50 m/h. Giant cells with dimensions that approximated those in vivo were observed in vitro after prolonged culture in minimal media, and were the oldest in the culture, suggesting that giant cell formation is an aging-dependent phenomenon. Giant cells recovered from mice displayed polyploidy, suggesting a mechanism by which gigantism results from cell cycle progression without cell fission. Giant cell formation was dependent on cAMP, but not on Ras1. Real-time imaging showed that giant cells were engaged, but not engulfed by phagocytic cells. We describe a remarkable new strategy for C. neoformans to evade the immune response by enlarging cell size, and suggest that gigantism results from replication without fission, a phenomenon that may also occur with other fungal pathogens

The Combination of Iron and Copper Increases Pathogenicity and Induces Proteins Related to the Main Virulence Factors in Clinical Isolates of Cryptococcus neoformans var. grubii

In fungi, metals are associated with the expression of virulence factors. However, it is unclear whether the uptake of metals affects their pathogenicity. This study aimed to evaluate the effect of iron/copper in modulating pathogenicity and proteomic response in two clinical isolates of C. neoformans with high and low pathogenicity. Methods: In both isolates, the effect of 50 µM iron and 500 µM copper on pathogenicity, capsule induction, and melanin production was evaluated. We then performed a quantitative proteomic analysis of cytoplasmic extracts exposed to that combination. Finally, the effect on pathogenicity by iron and copper was evaluated in eight additional isolates. Results: In both isolates, the combination of iron and copper increased pathogenicity, capsule size, and melanin production. Regarding proteomic data, proteins with increased levels after iron and copper exposure were related to biological processes such as cell stress, vesicular traffic (Ap1, Vps35), cell wall structure (Och1, Ccr4, Gsk3), melanin biosynthesis (Hem15, Mln2), DNA repair (Chk1), protein transport (Mms2), SUMOylation (Uba2), and mitochondrial transport (Atm1). Increased pathogenicity by exposure to metal combination was also confirmed in 90% of the eight isolates. Conclusions: The combination of these metals enhances pathogenicity and increases the abundance of proteins related to the main virulence factors

Cryptococcus neoformans can form titan-like cells in vitro in response to multiple signals

Cryptococcus neoformans is an encapsulated pathogenic yeast that can change the size of the cells during infection. In particular, this process can occur by enlarging the size of the capsule without modifying the size of the cell body, or by increasing the diameter of the cell body, which is normally accompanied by an increase of the capsule too. This last process leads to the formation of cells of an abnormal enlarged size denominated titan cells. Previous works characterized titan cell formation during pulmonary infection but research on this topic has been hampered due to the difficulty to obtain them in vitro. In this work, we describe in vitro conditions (low nutrient, serum supplemented medium at neutral pH) that promote the transition from regular to titan-like cells. Moreover, addition of azide and static incubation of the cultures in a COenriched atmosphere favored cellular enlargement. This transition occurred at low cell densities, suggesting that the process was regulated by quorum sensing molecules and it was independent of the cryptococcal serotype/species. Transition to titan-like cell was impaired by pharmacological inhibition of PKC signaling pathway. Analysis of the gene expression profile during the transition to titan-like cells showed overexpression of enzymes involved in carbohydrate metabolism, as well as proteins from the coatomer complex, and related to iron metabolism. Indeed, we observed that iron limitation also induced the formation of titan cells. Our gene expression analysis also revealed other elements involved in titan cell formation, such as calnexin, whose absence resulted in appearance of abnormal large cells even in regular rich media. In summary, our work provides a new alternative method to investigate titan cell formation devoid the bioethical problems that involve animal experimentation

Cryptococcus neoformans Capsular Enlargement and Cellular Gigantism during Galleria mellonella Infection

We have studied infection of Cryptococcus neoformans in the non-vertebrate host Galleria mellonella with particular interest in the morphological response of the yeast. Inoculation of C. neoformans in caterpillars induced a capsule-independent increase in haemocyte density 2 h after infection. C. neoformans manifested a significant increase in capsule size after inoculation into the caterpillar. The magnitude of capsule increase depended on the temperature, being more pronounced at 37°C than at 30°C, which correlated with an increased virulence of the fungus and reduced phagocytosis at 37°C. Capsule enlargement impaired phagocytosis by haemocytes. Incubation of the yeast in G. mellonella extracts also resulted in capsule enlargement, with the polar lipidic fraction having a prominent role in this effect. During infection, the capsule decreased in permeability. A low proportion of the cells (<5%) recovered from caterpillars measured more than 30 µm and were considered giant cells. Giant cells recovered from mice were able to kill the caterpillars in a manner similar to regular cells obtained from in vivo or grown in vitro, establishing their capacity to cause disease. Our results indicate that the morphological transitions exhibited by C. neoformans in mammals also occur in a non-vertebrate host system. The similarities in morphological transitions observed in different animal hosts and in their triggers are consistent with the hypothesis that the cell body and capsular responses represent an adaptation of environmental survival strategies to pathogenesis

LA U INVESTIGA: Revista Científica. Facultad Ciencias de la Salud. Volumen 3. Número 1

Los ámbitos de investigación expuestos en este número corresponden a salud, educación, comunicación; temática relacionados íntimamente con la problemática social, que trata de visibilizarla a través de la difusión científica. Desde una visión de caso clínico, como son aquellos artículos investigados en los centros asistenciales del país; o de análisis colectivo evidente en los artículos elaborados por académicos de la Universidad Técnica del Norte.• Adenoma pleomorfo metastásico a mama y pulmón. • Evaluación clínica y atención temprana de la potencialidad cerebromotriz innata en los recién nacidos vivos con factores de riesgo neonatal del hospital general San Vicente de Paúl. • Embarazo ectopico cervical a proposito de un caso • Ganglio centinela en cáncer de mama uso de azul patente en unidades de segundo nivel. • Morbimortalidad en recién nacidos pretérminos menores de 36 semanas, hospital IESS Ibarra año 2014. • Ruptura esplénica asociada con preeclampsia severa presentacion de un caso. • Enfermedad de Addison de etiología tuberculosa: presentación de caso clínico. • Estado de la independencia funcional en personas con discapacidad del cantón Otavalo. • Síntesis analítica sobre las bondades medicinales de la jícama (smallanthus sonchifolius) 2015. • Prevención de infecciones puerperales con Churiyuyo (kalanchoe pinnata), una experiencia de las parteras tradicionales en Napo Ecuador. • Valoración de las habilidades comunicativas en la relación fisioterapeuta paciente. • Objeto de aprendizaje móvil en el aula, para estudiantes de la carrera de Nutrición y salud comunitaria, Universidad Técnica del Norte. • Infecciones de vías urinarias asociadas a catéter vesical en mujeres embarazadas. Hospital San Vicente de Paúl, 2015. • Proceso enfermero en la satisfacción de las necesidades básicas en usuario colecistectomizado. • Satisfacción laboral de los profesionales de enfermerí

La renovación de la palabra en el bicentenario de la Argentina : los colores de la mirada lingüística

El libro reúne trabajos en los que se exponen resultados de investigaciones presentadas por investigadores de Argentina, Chile, Brasil, España, Italia y Alemania en el XII Congreso de la Sociedad Argentina de Lingüística (SAL), Bicentenario: la renovación de la palabra, realizado en Mendoza, Argentina, entre el 6 y el 9 de abril de 2010. Las temáticas abordadas en los 167 capítulos muestran las grandes líneas de investigación que se desarrollan fundamentalmente en nuestro país, pero también en los otros países mencionados arriba, y señalan además las áreas que recién se inician, con poca tradición en nuestro país y que deberían fomentarse. Los trabajos aquí publicados se enmarcan dentro de las siguientes disciplinas y/o campos de investigación: Fonología, Sintaxis, Semántica y Pragmática, Lingüística Cognitiva, Análisis del Discurso, Psicolingüística, Adquisición de la Lengua, Sociolingüística y Dialectología, Didáctica de la lengua, Lingüística Aplicada, Lingüística Computacional, Historia de la Lengua y la Lingüística, Lenguas Aborígenes, Filosofía del Lenguaje, Lexicología y Terminología

Papel de los cambios morfológicos en la virulencia de "Cryptococcus neoformans"

Cryptococcosisis is an infectious disease caused by yeasts from the gender Cryptococcus, being C. neoformans and C. gattii the species more offenly isolated. Cryptococcus neoformans is a cosmopolitan environmental pathogen of major concern among HIV patients which has a significant incidence in developing areas. Cryptococcus neoformans blastoconidia or desiccated spores are inhaled and can cause pneumonia and meningitis in immunosuppressed individuals. Its sibling species, Cryptococcus gattii, is more restricted to tropical areas and infects principally immunocompetent individuals and causes mainly pneumonia. Cryptococcus interaction with the host has been widely studied for its capacity to modulate the immune response, replicate within macrophages, disseminate from the lungs to the central nervous system, and/or stay in a latent state for years. The main cryptococcal virulence factors are a polysaccharide capsule and melanin accumulation, although this yeast has also other traits, such as urease and phospholipases that confer adaptation to the host. Morphogenesis is a common feature among fungal pathogens. Cryptococcus neoformans does not form filaments nor pseudohyphae. However, during infection, this yeast undergoes cellular changes which result in the appearance of different cellular types. These changes are: 1) Capsule enlargement; and 2) Significant growth of the whole cell, which leads to the formation of “Giant/Titan” cells. However, the molecular mechanisms involved in the regulation of these processes are not known..

Candida parapsilosis, Candida orthopsilosis, and Candida metapsilosis virulence in the non-conventional host Galleria mellonella

The incidence of fungal infections due to C. parapsilosis and closely related cryptic species (-psilosis complex) has increased in the last few years, but differences in virulence among these species have not been widely studied. Fifteen clinical isolates of C. parapsilosis, C. orthopsilosis, and C. metapsilosis, including the type strains, were used to evaluate their virulence in Galleria mellonella larvae. Fluctuations in the hemocyte density and in the phagocytic activity were also tested. Differences in the median survival for these species were demonstrated at 37 °C (2.6 ± 1.02, 2.3 ± 0.92, and 4.53 ± 1.65 d for C. parapsilosis, C. orthopsilosis, and C. metapsilosis, respectively). Galleria mellonella hemocytes phagocytosed C. metapsilosis strains more effectively than did for C. orthopsilosis and C. parapsilosis (P < 0.05). The phagocytosis rate was lower for C. parapsilosis than for C. orthopsilosis (P < 0.05). The hemocyte density was increased in larvae infected with C. metapsilosis compared with those infected with C. parapsilosis or C. orthopsilosis (P < 0.05). Moreover, in vitro studies of virulence factors such as pseudohyphae production and hydrolytic enzyme secretion showed that the capability of C. metapsilosis strains to produce those virulence factors was reduced. Infections due to -psilosis complex species produced tissue damage in G. mellonella and pseudohyphae could be also observed during infection with C. parapsilosis

Candida parapsilosis

The incidence of fungal infections due to C. parapsilosis and closely related cryptic species (-psilosis complex) has increased in the last few years, but differences in virulence among these species have not been widely studied. Fifteen clinical isolates of C. parapsilosis, C. orthopsilosis, and C. metapsilosis, including the type strains, were used to evaluate their virulence in Galleria mellonella larvae. Fluctuations in the hemocyte density and in the phagocytic activity were also tested. Differences in the median survival for these species were demonstrated at 37 °C (2.6 ± 1.02, 2.3 ± 0.92, and 4.53 ± 1.65 d for C. parapsilosis, C. orthopsilosis, and C. metapsilosis, respectively). Galleria mellonella hemocytes phagocytosed C. metapsilosis strains more effectively than did for C. orthopsilosis and C. parapsilosis (P&lt;0.05). The phagocytosis rate was lower for C. parapsilosis than for C. orthopsilosis (P&lt;0.05). The hemocyte density was increased in larvae infected with C. metapsilosis compared with those infected with C. parapsilosis or C. orthopsilosis (P&lt;0.05). Moreover, in vitro studies of virulence factors such as pseudohyphae production and hydrolytic enzyme secretion showed that the capability of C. metapsilosis strains to produce those virulence factors was reduced. Infections due to -psilosis complex species produced tissue damage in G. mellonella and pseudohyphae could be also observed during infection with C. parapsilosis. </p