Therapy of systemic histoplasmosis in immunosuppressed mice with the triazole D0870

Efficacy of ravuconazole in treatment of systemic murine histoplasmosis

Ravuconazole (RCZ) was evaluated for efficacy in comparison to fluconazole (FCZ) and itraconazole (ITZ) in murine models of disseminated histoplasmosis. All regimens tested prolonged survival (P < 0.05 to 0.0001). At equivalent doses of 50 mg/kg of body weight, RCZ and ITZ were equally effective and RCZ was more effective than FCZ (P = 0.02). Clearance of fungal burden from the livers and spleens of mice showed RCZ and ITZ at doses of 50 mg/kg to be efficacious but not curative. These data indicate that RCZ should be studied further.

Efficacy of interferon-gamma and amphotericin B for the treatment of systemic murine histoplasmosis

The number of cases of systemic histoplasmosis has increased substantially in recent years, and improved therapy is needed. We examined the efficacy of immunomodulation with interferon (IFN)-gamma alone or in combination with a suboptimal regimen of amphotericin B for the treatment of primary systemic murine histoplasmosis. In the first study, BALB/c mice were infected with Histoplasma capsulatum G217B and treated with 10(5) U of IFN given every other day either preinfection and postinfection or only postinfection, alone or in combination with amphotericin B. IFN alone given subcutaneously (s.c.) postinfection prolonged survival over untreated controls (P < 0.01), whereas intravenous (i.v.) administration was ineffective. All combination regimens and amphotericin B alone significantly prolonged survival (P < 0.0001). The combination regimens of amphotericin B and IFN i.v. (pre- and postinfection) or IFN s.c. (postinfection) reduced the fungal burden in the liver and spleen; the latter regimen had superior efficacy in the spleen (P < 0.05) to either amphotericin B or IFN alone. After infection with a low-challenge inoculum, IFN given s.c. (pre- and postinfection) alone caused a significant reduction in fungal burden in the spleen (P < 0.001). In an acutely lethal model, combination regimens of IFN s.c. or i.v. and amphotericin B again prolonged survival (P < 0.01-0.001), with amphotericin B plus IFN given s.c. (pre- and postinfection) superior to all regimens (P < 0.05-0.01). This regimen also showed enhanced efficacy in causing the reduction of fungal burden in the spleen (P < 0.05). These results indicate that IFN in combination with AmB shows enhanced efficacy in the treatment of systemic histoplasmosis and support the potential utility of IFN as an adjunctive therapy.

Experimental histoplasmosis in mice treated with anti-murine interferon-gamma antibody and in interferon-gamma gene knockout mice

Histoplasma capsulatum is an important fungal pathogen in immunocompromised hosts, including AIDS patients. Experimental evidence suggests interferon-gamma (IFN) plays a role in host defense against H. capsulatum. In these studies we sought to demonstrate the importance of IFN in innate resistance to systemic histoplasmosis. The possible exacerbation of infection in BALB/c mice was assessed by administering 200 microg of hamster anti-IFN antibody prior to infection with H. capsulatum (2 x 10(6) yeasts, i.v.) and by comparing the severity of infection between BALB/c IFN gene knockout mice (GKO) and congenic control animals. In two separate studies, we found that anti-IFN treatment caused a dramatic loss of resistance to lethal infection and resulted in earlier mortality of IFN-depleted animals compared with normal IgG or no treatment (P<0.001). GKO mice were significantly (P<0.001) more susceptible to lethal infection than were control animals, and histological studies corroborated this. These studies clearly demonstrate that IFN is a vital part of the host's innate resistance to systemic infection with H. capsulatum and provide an additional rationale for studying IFN as an immunomodulatory therapeutic for the treatment of this disease.

Murine models of blastomycosis, coccidioidomycosis, and histoplasmosis

Animal models have contributed much to the knowledge of fungal infections and their corresponding therapeutic treatments. This is true for animal models of the primary fungal pathogens, Blastomyces dermatitidis, Coccidioides immitis, and Histoplasma capsulatum. This review gives a brief background of human diseases associated with these organisms and describes the development, details, and utility of murine models of blastomycosis, as well as coccidioidomycosis and histoplasmosis.