Cell wall proteins of Sporothrix schenckii as immunoprotective agents

Fungal Glycosidases in Sporothrix Species and Candida albicans

Glycoside hydrolases (GHs) are enzymes that participate in many biological processes of fungi and other organisms by hydrolyzing glycosidic linkages in glycosides. They play fundamental roles in the degradation of carbohydrates and the assembly of glycoproteins and are important subjects of studies in molecular biology and biochemistry. Based on amino acid sequence similarities and 3-dimensional structures in the carbohydrate-active enzyme (CAZy), they have been classified in 171 families. Members of some of these families also exhibit the activity of trans-glycosydase or glycosyl transferase (GT), i.e., they create a new glycosidic bond in a substrate instead of breaking it. Fungal glycosidases are important for virulence by aiding tissue adhesion and colonization, nutrition, immune evasion, biofilm formation, toxin release, and antibiotic resistance. Here, we review fungal glycosidases with a particular emphasis on Sporothrix species and C. albicans, two well-recognized human pathogens. Covered issues include a brief account of Sporothrix, sporotrichosis, the different types of glycosidases, their substrates, and mechanism of action, recent advances in their identification and characterization, their potential biotechnological applications, and the limitations and challenges of their study given the rather poor available information.

Cutaneous disseminated sporotrichosis associated with diabetes: A case report and literature review

BACKGROUND

Cutaneous disseminated sporotrichosis (CDS), also called hematogenous sporotrichosis, is a rare condition that usually affects immunocompromised patients. The current work presents the case of a woman with diabetes mellitus associated with CDS.

CASE PRESENTATION

A 59-year-old woman with diabetes mellitus presented with a two-year history of ulcerated rashes on the left ankle and both sides of the jaw. Physical examination revealed three annular areas of erythematous and raised plaque with an ulcer over the left ankle and both sides of the jaw. Based on laboratory findings, elevated blood glucose concentration and decreased white cell count were observed. Sporothrix globosa was identified in the mycological culture of biopsied tissue from the three lesions and this was confirmed by DNA sequencing. The skin lesions healed after two-month itraconazole therapy.

CONCLUSIONS

Diabetes is a risk factor for disseminated sporotrichosis, which may be induced by hematogeneous spread, repeated inoculation, or autoinoculation. This study raises awareness among clinicians, with regard to the notion that people with possibly altered immune function are potentially vulnerable to severe clinical forms of sporotrichosis.

Current Progress on Epidemiology, Diagnosis, and Treatment of Sporotrichosis and Their Future Trends

Sporotrichosis, a human and animal disease caused by Sporothrix species, is the most important implantation mycosis worldwide. Sporothrix taxonomy has improved in recent years, allowing important advances in diagnosis, epidemiology, and treatment. Molecular epidemiology reveals that S. brasiliensis remains highly prevalent during the cat-transmitted sporotrichosis outbreaks in South America and that the spread of S. brasiliensis occurs through founder effects. Sporothrix globosa and S. schenckii are cosmopolitan on the move, causing major sapronoses in Asia and the Americas, respectively. In this emerging scenario, one-health approaches are required to develop a creative, effective, and sustainable response to tackle the spread of sporotrichosis. In the 21st century, it has become vital to speciate Sporothrix, and PCR is the main pillar of molecular diagnosis, aiming at the detection of the pathogen DNA from clinical samples through multiplex assays, whose sensitivity reaches remarkably three copies of the target. The treatment of sporotrichosis can be challenging, especially after the emergence of resistance to azoles and polyenes. Alternative drugs arising from discoveries or repositioning have entered the radar of basic research over the last decade and point to several molecules with antifungal potential, especially the hydrazone derivatives with great in vitro and in vivo activities. There are many promising developments for the near future, and in this review, we discuss how these trends can be applied to the Sporothrix-sporotrichosis system to mitigate the advance of an emerging and re-emerging disease.

The Role of Macrophages in the Host's Defense against Sporothrix schenckii

The role of immune cells associated with sporotrichosis caused by Sporothrix schenckii is not yet fully clarified. Macrophages through pattern recognition receptors (PRRs) can recognize pathogen-associated molecular patterns (PAMPs) of Sporothrix, engulf it, activate respiratory burst, and secrete pro-inflammatory or anti-inflammatory biological mediators to control infection. It is important to consider that the characteristics associated with S. schenckii and/or the host may influence macrophage polarization (M1/M2), cell recruitment, and the type of immune response (1, 2, and 17). Currently, with the use of new monocyte-macrophage cell lines, it is possible to evaluate different host-pathogen interaction processes, which allows for the proposal of new mechanisms in human sporotrichosis. Therefore, in order to contribute to the understanding of these host-pathogen interactions, the aim of this review is to summarize and discuss the immune responses induced by macrophage-S. schenckii interactions, as well as the PRRs and PAMPs involved during the recognition of S. schenckii that favor the immune evasion by the fungus.

Proteomic analysis of Sporothrix schenckii cell wall reveals proteins involved in oxidative stress response induced by menadione

Sporotrichosis is an emergent subcutaneous mycosis that is a threat to both humans and other animals. Sporotrichosis is acquired by the traumatic implantation of species of the Sporothrix genus. Added to the detoxification systems, pathogenic fungi possess different mechanisms that allow them to survive within the phagocytic cells of their human host during the oxidative burst. These mechanisms greatly depend from the cell wall (CW) since phagocytic cells recognize pathogens through specific receptors associated to the structure. To date, there are no studies addressing the modulation of the expression of S. schenckii CW proteins (CWP) in response to reactive oxygen species (ROS). Therefore, in this work, a proteomic analysis of the CW of S. schenckii in response to the oxidative agent menadione (O₂•^-) was performed. Proteins that modulate their expression were identified which can be related to the fungal survival mechanisms within the phagocyte. Among the up-regulated CWP in response to the oxidative agent, 13 proteins that could be involved in the mechanisms of oxidative stress response in S. schenckii were identified. The proteins identified were thioredoxin1 (Trx1), superoxide dismutase (Sod), GPI-anchored cell wall protein, β-1,3-endoglucanase EglC, glycoside hydrolase (Gh), chitinase, CFEM domain protein, glycosidase crf1, covalently-linked cell wall protein (Ccw), 30 kDa heat shock protein (Hsp30), lipase, trehalase (Treh), fructose-bisphosphate aldolase (Fba1) and citrate synthase (Cs). The identification of CWP that modulates their expression in response to superoxide ion (O₂•^-) in S. schenckii is a useful approach to understand how the fungus defends itself against ROS, in order to evade the phagocytic cells from the host and cause the infection.

Antifungal activity of different molecular weight chitosans against planktonic cells and biofilm of Sporothrix brasiliensis

Sporotrichosis, caused by Sporothrix schenckii complex species, is the most prevalent subcutaneous mycosis in many areas of Latin America. Chitosan has been used as an antifungal agent; however the effects of the molecular weight (MW) of chitosan (i.e. high (HMW), medium (MMW) and low (LMW) molecular weight chitosan) on S. brasiliensis has not been well described, particularly on biofilms. Effects on the planktonic form activity of S. brasiliensis were quantified by broth microdilution, while anti-biofilm activity was quantified by measuring metabolic activity via XTT (2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide and biomass formation (crystal violet). The molecular weight of chitosan modulated its effect on the planktonic form of S. brasiliensis, presenting lower MIC values for LMW chitosan. With regards both the adhesive and mature phases of biofilm, the LMW chitosan reduced biomass and metabolic activity most effectively. This study confirms the effects of the molecular weight and deacetylation degree of chitosan on its antifungal properties for potentially pathogenic fungi.

Morphological changes and phagocytic activity during the interaction of human neutrophils with Sporothrix schenckii: An in vitro model

Histopathological studies of human sporotrichosis lesions show pyogenic and granulomatous processes in which polymorphonuclear neutrophils (PMNs) play a central role. Few studies regarding the events associated with the interaction of human PMNs with Sporothrix schenckii have been made despite their importance in the clinical manifestations of the disease. In this study, human PMNs were co-cultured with conidia or yeast cells of S. schenckii to compare the phagocytic activity and morphological changes that could provide a clearer insight into the role of these phagocytes in the initial phase of sporotrichosis. PMNs showed increased cell size and separation of the nuclear lobes after phagocytosis. Through Scanning Electron Microscopy (SEM) analysis, an increase in cells with flattened filaments and vesicles on their surface was observed. Phagocytosed conidia showed a significant increase in width and size. The phagocytic activity was greater against yeasts than with conidia, but the viability of both S. schenckii cellular morphotypes was not drastically affected even after 2 h of co-culture. In conclusion, morphological changes in PMNs suggest that S. schenckii induces processes that may favor proinflammatory events. These phagocytes show a high ability to bind or ingest S. schenckii cells without affecting their viability. Morphological changes recorded in ingested conidia, suggest that this fungus could make the dimorphic switching in PMNs.

Sporothrix schenckii Cell Wall Proteins-Stimulated BMDCs Are Able to Induce a Th1-Prone Cytokine Profile In Vitro

Sporotrichosis is a subcutaneous mycosis affecting humans and other animals. The disease can be acquired by accidental inoculation of the fungus through the skin or through the respiratory system. Sporotrichosis can also be transmitted through bites or scratches by infected cats and more rarely by other animals (zoonotic transmission). Conventional antifungal therapy is especially inefficient in immunocompromised patients, who tend to develop the most severe forms of the disease, thus prompting the search for alternative therapies. Given their antigen-presenting properties, dendritic cells (DCs) have been used in both prophylactic and therapeutic vaccination strategies. Hence, this study aims to assess the use of DCs as a prophylactic tool in sporotrichosis by evaluating the immune profile induced by Sporothrix schenckii cell wall proteins (SsCWP)-stimulated, bone-marrow-derived DCs (BMDCs). Mouse BMDCs were stimulated with SsCWP for 24 h and analyzed for the surface expression of costimulatory molecules and TLR-4, as well as for the secretion of proinflammatory cytokines and IL-10. Following that, activated BMDCs were cocultured with splenocytes for 72 h and had the same cytokines measured in the supernatant. SsCWP-stimulated BMDCs showed higher expression of CD80, CD86, and CD40, but not TLR-4, and higher secretion of IL-6, IL-17A, and TNF. On the other hand, higher levels of IFN-γ, IL-10, and IL-2 were found in the supernatants of the coculture as compared with the BMDCs alone; TNF secretion was almost completely abrogated, whereas IL-6 was only partially inhibited and IL-17A was unaffected. Our results thus suggest that SsCWP-stimulated BMDCs are able to induce a Th1-prone cytokine profile which is known to be protective against other fungal diseases. This result could lead to studies which evaluate the development of prophylactic and/or therapeutic DC-based tools against sporotrichosis.

Immunity and Treatment of Sporotrichosis

Species of the Sporothrix complex are the etiological agents of sporotrichosis, an important subcutaneous mycosis with several clinical forms and an increasing incidence around the world that affects humans and other mammals. The immunological mechanisms involved in the prevention and control of this mycosis are not entirely understood. Many reports have suggested that cell-mediated immunity has an essential role in the development of the disease, being the primary response controlling it, while only recent data supports that the humoral response is essential for the appropriate control. This mycosis is a challenge for diagnosis since the culture and isolation of the organism are time-consuming and complicated; reasons that have led to the study of fungus antigenic molecules capable of generating a detectable humoral response. The treatment for this disease includes the use of several antifungal drugs like itraconazole, amphotericin B, caspofungin, fluconazole, and the combination between them among others such as the extract of Vismia guianensis.

Immunopathogenesis of Human Sporotrichosis: What We Already Know

Sporotrichosis is a subacute/chronic mycosis caused by dimorphic fungus of the genus Sporothrix. This mycosis may affect both human and domestic animals and in the last few years, the geographic dispersion and increase of sporotrichosis worldwide has been observed. The occurrence of cases related to scratching/bites of domestic felines have increased, characterizing the disease as predominantly a zoonosis. In humans, sporotrichosis mainly involves the cutaneous tegument of infected patients, but other tissues may also present the infection. The main forms of clinical presentation are lymphocutanous sporotrichosis (LC) and fixed sporotrichosis (F). Although less common, mucosal, cutaneous disseminated, and extracutaneous forms have also been described. Multiple factors from the fungus and host can play a role in driving the clinical evolution of sporotrichosis to benign or severe disease. In this review, we discuss the immunopathological aspects involved in human sporotrichosis. Putting together the two branches of knowledge—host immune response and fungal evading mechanisms—we may perceive new possibilities in understanding the fungus–host interaction in order to be in a position to go further in the control of sporotrichosis.

Sporotrichosis: an update on epidemiology, etiopathogenesis, laboratory and clinical therapeutics

In the late 90's there was a change in both the route of transmission and the people at risk for sporotrichosis. This zoonotic cat-man alternative transmission route elicited changes in strategies to control the epidemic. There was a progressive increase in the number of cases involving especially children and the elderly. In addition to becoming hyperendemic, uncommon clinical pictures like immunoreactive clinical presentations or severe systemic cases have emerged. New species were identified and classified through molecular tools using more virulent clinical isolates, like S. brasiliensis, compared to the environmental isolates. Likewise, different species of Sporothrix have been associated with different geographic regions. The serological and molecular techniques are used as an auxiliary tool for the diagnosis and/or for species identification, although the isolation and the identification of Sporothrix spp. in clinical specimen is still the gold standard. Currently sporotrichosis epidemics requires the knowledge of the epidemiological-molecular profile to control the disease and the specific treatment. Itraconazole, potassium iodide, terfinafine, and amphotericin B are the available drugs in Brazil to treat sporotrichosis. The drug of choice, its posology, and treatment duration vary according to the clinical presentation, the Sporothrix species, and host immune status. New treatment choices, including a vaccine, are being developed; nevertheless, more clinical trials are required to confirm its efficacy.

Clinical features of 10 cases of eyelid sporotrichosis in Jilin Province (Northeast China)

OBJECTIVE

Sporotrichosis is a common subcutaneous mycosis caused by an infection with dimorphic fungus Sporothrix schenckii. We present a series of patients with eyelid sporotrichosis and study the clinical and histopathological presentation, microbiology, treatment options, and outcome.

METHODS

A retrospective case-series study of patients with a clinical diagnosis of eyelid sporotrichosis. Records were examined to obtain information regarding patient demographics, presenting symptoms and signs, histopathological examination, microbiology, management, and outcomes.

RESULTS

Ten patients (4 men, 6 women; mean age 46.5 years, range 3-81 years) were included. Based on their clinical manifestations, eyelid sporotrichosis was classified into 3 major forms: (i) fixed cutaneous (6/10 cases), (ii) lymphocutaneous (3/10 cases), and (iii) eyelid abscess (1/10 cases). All the cases were treated with a terbinafine 12-week regimen. Nodules, papules, and abscesses regressed after treatment. No recurrence was discovered after a 12-week follow-up.

CONCLUSIONS

Eyelid sporotrichosis has typical features of clinical manifestations. Histopathological examination and tissue culture are helpful for diagnosis. Confirmed cases normally require long-term systematic treatment with antifungal agents, but surgical removal is normally unnecessary.

Involvement of major components from Sporothrix schenckii cell wall in the caspase-1 activation, nitric oxide and cytokines production during experimental sporotrichosis

Sporotrichosis is a chronic infection caused by the dimorphic fungus Sporothrix schenckii, involving all layers of skin and the subcutaneous tissue. The role of innate immune toll-like receptors 2 and 4 in the defense against this fungus has been reported, but so far, there were no studies on the effect of cell wall major components over the cytosolic oligo-merization domain (NOD)-like receptors, important regulators of inflammation and responsible for the maturation of IL-1β and IL-18, whose functions are dependents of the caspase-1 activation, that can participate of inflammasome. It was evaluated the percentage of activation of caspase-1, the production of IL-1β, IL-18, IL-17, IFN-γ and nitric oxide in a Balb/c model of S. schenckii infection. It was observed a decreased activity of caspase-1 during the fourth and sixth weeks of infection accompanied by reduced secretion of the cytokines IL-1β, IL-18 and IL-17 and high production of nitric oxide. IFN-γ levels were elevated during the entire time course of infection. This temporal reduction in caspase-1 activity coincides exactly with the reported period of fungal burden associated with a transitory immunosuppression induced by this fungus and detected in similar infection models. These results indicate the importance of interaction between caspase-1, cytokines IL-1β and IL-18 in the host defense against S. schenckii infection, suggesting a participation the inflammasome in this response.