Experimental cutaneous sporotrichosis

Molecular Components of the Sporothrix schenckii Complex that Induce Immune Response

Sporotrichosis is a fungal disease caused by the Sporothrix schenckii complex that includes species such as S. brasiliensis, S. schenckii sensu stricto, S. globosa, S. luriei, S. mexicana, and S. pallida, which exhibit different potentially antigenic molecular components. The immune response of susceptible hosts to control infection and disease caused by these fungi has been little studied. Besides, the fungus-host interaction induces the activation of different types of immune response. This mini-review analyzes and discusses existing reports on the identification and functional characterization of molecules from species of the S. schenckii complex with clinical relevance, and the mechanisms that mediate the type and magnitude of the immune response in experimental models in vivo and in vitro. This knowledge is expected to contribute to the development of protective and therapeutic strategies against sporotrichosis and other mycoses.

Involvement of CD4+ T cells and macrophages in acquired protection against infection with Sporothrix schenckii in mice

The cell-mediated immune response against infection with Sporothrix schenckii was investigated in vivo and in vitro. Following primary infection, mice were protected against a secondary subcutaneous inoculation with S. schenckii as determined by the local growth of fungi, and subcutaneously immunized mice were able to survive a lethal intravenous infection. Protection could be transferred to naive congenitally athymic nude mice using lymph node cells taken from immune mice. When immune lymph node cells had CD4+ cells depleted by antibody plus complement, the ability to transfer protection was significantly reduced. Treatment of mice with carrageenan, a macrophage blocker, before and after secondary inoculation abolished protection. An in vitro system, using either immune lymph node cells alone or macrophages alone, failed to kill the organism. However, inhibition of fungal growth was observed when both immune lymph node cells and macrophages were combined. Growth inhibition in vitro was reduced after depletion of CD4+ cells but not CD8+ cells. Addition of anti-interferon (IFN)-gamma monoclonal antibodies (MAb) also reduced growth inhibition. By using reverse transcription-polymerase chain reaction (RT-PCR) analysis, it was shown that immune lymph node cells expressed message for IFN-gamma, tumour necrosis factor (TNF)-alpha and interleukin (IL)-10 after stimulation with heat-killed S. schenckii. These results suggest that acquired immunity against S. schenckii is expressed mainly by macrophages activated by CD4+ T cells.

Role of cell-mediated immunity in the resistance to experimental sporotrichosis in mice

Congenitally athymic nude (nu/nu) mice showed higher sensitivity to intratestical infection of Sporothrix schenckii than phenotypically normal littermates (nu/+). Active immunization with viable cells enhanced the resistance to intravenous (i.v.) infection of this fungus in BALB/c mice. Nu/nu mice transferred with immune spleen cells acquired the enhancement of resistance to the infection with S. schenckii, but not ones with normal spleen cells. Pre-treatment of OK-432 (Picibanil), one of the macrophage activating agents, enhanced resistance to i.v. infection of this fungus in BALB/c mice. On the other hand, pretreatment of carrageenan, one of the macrophage inhibitors, impaired the resistance. This fungus was intracellularly killed by peritoneal macrophage from OK-432 treated or immunized mice but not by those from normal mice in vitro. These results suggest that activated macrophage, that was mediated by T cells, play an important role in the resistance to S. schenckii in mice.

A diffusion chamber technique for testing of antifungal drugs against Sporothrix schenckii in vivo

Growth of the yeast form of Sporothrix schenckii (ATCC 14804) was determined in diffusion chambers with 0.45 and 3.0 micron pore size over a period of 24 to 192 h after subcutaneous implantation into mice. Numbers of S. schenckii in 0.45 micron chambers increased significantly by 192 h when inocula of 10(3) and 10(5) colony forming units were implanted. In chambers with a pore size of 3.0 microns, only a slight decrease of fungal growth occurred, although host cells readily passed the filter membrane and phagocytosed yeast-form cells. The activities of amphotericin B, ketoconazole, itraconazole, ICI 153.066, vibunazole and potassium iodide against S. schenckii in implanted chambers were determined in terms of their effects on S. schenckii. ICI 153.066, ketoconazole, itraconazole and amphotericin B significantly reduced the numbers of reisolated S. schenckii in both types of chambers. There was a slight activity with vibunazole but none with potassium iodide.

Fixed cutaneous sporotrichosis: unusual histopathology following intralesional corticosteroid administration

The fixed cutaneous type of sporotrichosis is difficult to diagnose because clinical lesions are variable in appearance and the cells of Sporothrix schenckii are usually scarce in skin biopsy specimens. We have described two patients with lesions of fixed cutaneous sporotrichosis that resembled other inflammatory skin conditions and were treated with intralesional corticosteroids. Subsequent skin biopsies from these lesions demonstrated an unusually large number of yeast cells.