Taenia taeniaeformis in rat favors protracted skin lesions caused by Sporothrix schenckii infection: Dectin-1 and IL-17 are dispensable for clearance of this fungus

We occasionally found that cestode Taenia taeniaeformis in rats favored Sporothrix schenckii infection and survival, causing protracted cutaneous lesions. In this study, we compared the pathology and cytokines profile of rats co-infected with the two pathogens and infected with S. schenckii alone to explore underlying mechanisms. In the co-infection group, there was high expression of β-glucan receptor Dectin-1 in the cutaneous lesions and no multinucleated giant cells, but in the S. schenckii infection group the opposite was observed. Cytokines profiles demonstrated an expected finding that IL-4, commonly expressed in helminth and fungus infection, is undetectable in the two infection groups. In the single fungal infection group, cytokines IFN-γ, IL-10 and IL-17 kept increasing in the first few weeks of infection to a peak which was followed by gradual decrease. This study showed that Dectin-1 and IL-17, which were believed to be the major anti-fungus mechanisms, are Th2 independent and dispensable for clearance of S. schenckii infection, suggesting that S. schenckii has a different molecular recognition pattern and evokes anti-infection mechanisms other than Dectin-1 and IL-17.

Development of an enzyme-linked immunosorbent assay for the serodiagnosis of several clinical forms of sporotrichosis

We performed a serological study with sera from 92 patients with confirmed sporotrichosis registered between 1999 and 2004 in two hospitals in Rio de Janeiro State, Brazil. The clinical presentation of sporotrichosis was distributed as follows: lymphocutaneous, 67%; fixed cutaneous, 23%; disseminated cutaneous, 8%; and extracutaneous, 2%. Sera were assayed by ELISA against a cell wall antigen of Sporothrix schenckii, SsCBF, that we have previously described. The cross-reactivity was determined with 77 heterologous sera. The serological test showed a sensitivity of 90% and a global efficiency of 86%. A group of 55 patients with several clinical presentations of sporotrichosis was clinically and serologically followed-up for at least 6 months. We observed by ELISA data a decrease in the antibody serum titers which correlated with the progress in healing. An HIV-positive patient with meningeal sporotrichosis was serologically followed-up for over 2 years. Serum and cerebrospinal fluid specimens were examined and significant antibodies levels against the antigen SsCBF were detected. Our results strongly suggest that this serological test is valuable for the differential diagnosis and follow-up of all clinical forms of sporotrichosis.

Effect of genetic modificationsby selection for immunological toleranceon fungus infection in mice

Two strains of mice genetically selected for extreme phenotypes of immunological tolerance to ovalbumin, susceptible (TS) and resistant (TR), were experimentally infected with Sporothrix schenckii. The objective was to observe whether the genetic modifications produced by the selection might be associated with interstrain differences in adaptive immune and innate responses to infection. Therefore, we evaluated the LD(50), CFU, phagocytic index, fungicidal activity, pro-inflammatory cytokines, specific antibody titres, and the delayed-type hypersensitivity reactivity. TR mice were tenfold more susceptible to infection than TS mice, as shown by LD(50) (5 x 10(6) conidia i.v.). In TS mice, the resistance was a consequence of the tissue fungal load reduction, consistent specific T-cell-mediated immunity, and tumour necrosis factor (TNF)-alpha activity at onset of infection. In TR mice, these responses were not precociously detected. Therefore, the absence of CD4(+) T-cell response in the first week of infection might explain the non-clearance of pathogen in TR mice. However, TR mice did show an increase in TNF level and delayed-type hypersensitivity response after the first week post-infection; there was also expansion and increase in granulomatous foci and CFU in the spleen. The expansion of granulomatous foci and the increase in TNF-alpha and tissue fungal load to damaging levels induced severe tissue destruction, general failure of the organs, cachexy and death in TR mice. The results show that genetic selection for extreme phenotypes of immunological tolerance also modified the responses to S. schenckii infection.

Virulence of Sporothrix schenckii conidia and yeast cells, and their susceptibility to nitric oxide

The involvement of nitric oxide (NO) in macrophage (M phi) fungicidal activity against Sporothrix schenckii, and the relationship between NO susceptibility and the differential virulence of conidia and yeast cells, were investigated. Confirming a previously reported correlation between the length of time in culture and virulence of S. schenckii, conidia isolated from 12-day mycelial cultures (Ss-12) were less virulent to mice than conidia from 7-day cultures (Ss-7) or yeast cells. Indicative of NO production, infected animals showed a significant increase in serum levels of nitrite that was lower in mice infected with Ss-12 than in mice infected with Ss-7 or yeast. Stimulation of murine M phi with interferon-gamma (IFN-gamma) induced NO production and inhibition of fungal growth. The cytotoxic activity of M phi against Ss-12 was significantly greater than against Ss-7 or yeast cells, the highly virulent fungal forms. The addition of NO synthase inhibitors abrogated M phi cytotoxic activity against all fungal forms. The phagocytic activity of M phi against Ss-7 was significantly lower than against Ss-12 or yeast cells. Although the ingestion of fungal cells triggered the oxidative burst in M phi, the fungicidal activity was not altered in the presence of superoxide dismutase (SOD) and catalase. In addition, Ss-12 and yeast cells were more susceptible than Ss-7 to the direct fungicidal activity of the NO donors S-nitroso-N-acetyl-DL-penicillamine (SNAP), S-nitrosoglutathione (GSNO) and 3-morpholinosydnonimine (SIN-1). The results of this study indicate that NO is a key cytotoxic mediator involved in the murine M phi defence against S. schenckii, and that the virulence of Ss-7, Ss-12 and yeast cells may be related to a differential susceptibility to NO.

Fatal fungaemia due to Sporothrix schenckii

A clinical case is reported of a 78-year-old male with antecedents of diabetes and alcoholism who was hospitalized because he showed cutaneous lesions on the face and extremities suggesting cutaneous tuberculosis, but after a first histological study cutaneous leishmaniasis was erroneously diagnosed. Because of some unusual characteristics of the patient, the skin biopsies were carefully re-examined, as well as blood smears, which revealed elongated yeast form-like cells suggestive of Sporothrix schenckii. The diagnosis was confirmed when the fungus grew in mice and in Sabouraud cultures inoculated with blood samples from the patient. It is recommended that Sp. schenckii is included in the differential diagnosis of ulcerative cutaneous lesions in patients from Mexican humid areas.

Microbiology and potential virulence of Sporothrix cyanescens, a fungus rarely isolated from blood and skin

Sporothrix cyanescens has been recovered from blood and a finger lesion at several medical centers in the United States. The morphology and physiology of these and three additional isolates were studied. S. cyanescens was distinguished from S. schenckii and S. fungorum by white to lavender colonial pigmentation and from S. schenckii also by the formation of secondary conidia. All isolates of S. cyanescens grew well at 37 degrees C, were cycloheximide susceptible, strongly urease positive, and benomyl resistant, failed to hydrolyze starch, and were inhibited by sodium chloride in vitro at a concentration of greater than or equal to 12%. Study of S. cyanescens in a murine model by using intravenous inoculation failed to demonstrate an invasive pathogenic potential. The validity of the transfer of S. cyanescens to the new genus Cerinosterus Moore is discussed.

Subpopulation of lymphocytes in the infiltrate of experimental sporotrichosis

Lymphocyte subpopulations of dermal infiltrated cells on experimental sporotrichosis of guinea pigs was performed. According to Tan's method, infected sites were incubated with collagenase and then mechanically disaggregated. The liberated cells were used for determination of lymphocytes subpopulation. The predominance of B cells was present on the inoculated site, compare with blood from control and inoculated animals. Thus, the present result suggests the important role of humoral immunity in the development of sporotrichosis lesion.