Murine Candidiasis Research Articles

Efficacy evaluation of a novel submicron amphotericin B emulsion in murine candidiasis

A submicron amphotericin B (AmB) sterile emulsion with a mean droplet size of approximately 100 nm was prepared. The emulsion was stable at 4 degrees C over a period of 4 months. The acute toxicity results showed that the maximum tolerated dose of the AmB emulsion was 2.0 mg kg-1 as compared to 0.5 mg kg-1 for a commercial deoxycholate suspension, Fungizone. Efficacy evaluations of submicron AmB emulsion compared to Fungizone were performed in a murine candidiasis model using either a single or a multiple daily dose administration of 0.4 mg kg-1. Survival (100%) was observed up to 15-18 days post-infection in mice treated with AmB emulsion or Fungizone, while all control non-treated animals had died after 9 days in both single and multi-treatment experiments. Survival (50%) was obtained after 35 days in the single treatment, and 40 days in the multi-treatment, experiment with AmB emulsion, while treatment with Fungizone gave 50% survival after 15 and 20 days, respectively. The overall results indicate that in murine candidiasis, treatment with AmB submicron emulsion was more effective than Fungizone, suggesting a potential therapeutic application.

Biological properties of aureobasidin A, a cyclic depsipeptide antifungal antibiotic.

Aureobasidin A (AbA) is a novel cyclic depsipeptide antifungal antibiotic. The antifungal activity of AbA was studied in vitro and in vivo in comparison with clinically effective antifungal agents, amphotericin B and fluconazole. AbA was highly active in vitro against many pathogenic fungi, including Candida albicans, Cryptococcus neoformans, Blastomyces dermatitidis and Histoplasma capsulatum. The activity was superior to amphotericin B in most cases. AbA exhibited fungicidal action toward growing cultures of C. albicans. It was highly tolerated by mice and showed good efficacy in the treatment of murine systemic candidiasis when given orally or subcutaneously. AbA's fungicidal action in mice with candidiasis was more effective than fluconazole and amphotericin B.

Activity of MS-8209, a nonester amphotericin B derivative, in treatment of experimental systemic mycoses.

The in vitro and in vivo toxicities and activities of MS-8209, a new hydrosoluble amphotericin B (deoxycholate-amphotericin B [D-AmB]; Fungizone) derivative, were studied. In vitro, MS-8209 was less toxic than AmB against renal tubular cells in primary culture and less active against Candida albicans and Cryptococcus neoformans. However, at 10-fold the AmB concentration, MS-8209 in vitro antifungal activity paralleled that of AmB. Fifty-percent lethal doses of MS-8209 and D-AmB in OF1 noninfected mice were 26 and 2.3 mg/kg, respectively. Therapeutic efficacy of MS-8209 was assessed in murine candidiasis, cryptococcosis, and aspergillosis. In each model of infection, we determined the maximum tolerated dosages of MS-8209 and D-AmB, i.e., the dosage inducing less than 15% mortality due to toxicity; the efficacies of MS-8209 and D-AmB at their respective maximum tolerated dosages were compared. In candidiasis, MS-8209 (15 mg/kg) significantly increased the survival time compared with D-AmB (0.5 mg/kg). Both compounds were equally effective at reducing CFU counts in the kidney. MS-8209 was the most effective agent for increasing the survival time in cryptococcal meningoencephalitis and for reducing CFU counts in spleen, brain, and lung during both cryptococcal pneumonia and meningoencephalitis. In aspergillosis, MS-8209 and D-AmB similarly prolonged the survival of treated mice compared with controls. These results show that when MS-8209 and D-AmB were used at the maximum tolerated dosage, MS-8209 was as effective as or more effective than D-AmB for the treatment of systemic mycoses. These findings warrant further experiments to study the pharmacokinetic properties and toxicity of MS-8209 under conditions of chronic administration.

Immunoregulatory role of different t cell subsets in murine candidiasis

Immunoregulatory role of different t cell subsets in murine candidiasis

Neutralizing antibody to interleukin 4 induces systemic protection and T helper type 1-associated immunity in murine candidiasis.

An interleukin 4 (IL-4)-specific monoclonal antibody (mAb) was administered to mice infected systemically with the yeast Candida albicans, and the animals were monitored for mortality, development of delayed-type hypersensitivity, production of antibodies of different isotypes, release of IL-2, IL-4, IL-6, and interferon gamma (IFN-gamma) in vitro by splenic CD4+ lymphocytes, and levels of IL-4 and IFN-gamma mRNA in these cells. Neutralization of IL-4 by three weekly injections of mAb in several independent experiments resulted in an overall cure rate of 81% versus 0% of controls. Cure was associated with efficient clearance of the yeast from infected organs and histologic evidence of disease resolution, detection of strong T helper type 1 (Th1) responses, and establishment of long-lasting protective immunity. Soon after infection, and as a result of the first or second injection of mAb, there was a decrease in IL-4 mRNA in CD4+ cells, which was accompanied by an increase in the levels of IFN-gamma-specific transcripts. Our data thus indicate that the production of IL-4 by Th2 cells may limit Th1-associated protective immunity in murine candidiasis.

Antigen-specific cytolysis of infected cells in murine candidiasis.

Immune L3T4+ and Lyt-2+ lymphocytes play an important role in the acquired resistance of mice to challenge with virulent Candida albicans, and release macrophage-activating cytokines in response to yeast cells in vitro. To determine whether antigen (Ag)-specific cytotoxic T lymphocytes are generated during fungal infection, purified L3T4+ and Lyt-2+ lymphocytes from immunized mice were cultured in the presence of syngeneic accessory cells, Candida Ag, and IL-2. Yeast-infected bone marrow macrophages and peritoneal exudate neutrophils were used as target cells in a standard 51Cr release assay. Ag-specific, MHC-unrestricted lysis of infected macrophages was evident with immune Lyt-2+ cells after 5-10 days in culture. Under the same experimental conditions, the cytotoxic activity of L3T4+ cells was negligible, but its expression could be induced by the addition of anti-CD3 antibody. Culturing immune Lyt-2+ cells for shorter periods of time (1-2 days) resulted in preferential lysis of infected neutrophils. In addition, at limiting effector cell numbers, Ag-specific MHC-restricted lymphocytes with cytotoxic activity to infected macrophages could be identified. We suggest that C. albicans infection stimulates multiple cytotoxic T-cell precursors with varying recognition stringency, which may have an important role in antifungal resistance in vivo.

Th1 and Th2 cytokine secretion patterns in murine candidiasis: association of Th1 responses with acquired resistance

Two chemically mutagenized agerminative variants of Candida albicans were used to immunize mice against challenge with highly virulent cells of the parent strain. Although both mutants (Vir- 3 and Vir- 13) resulted in nonlethal infection and could be recovered from mouse organs for many days after the intravenous inoculation of 10(7) to 10(6) cells, significant protection to systemic challenge with virulent C. albicans was induced by only one (Vir- 3) of the two variants. Anticandidal resistance in Vir- 3-infected mice was associated with the occurrence in vivo of strong delayed-type hypersensitivity to Candida antigen, detection in vitro of highly fungicidal effector macrophages, and presence in the serum of a large proportion of Candida-reactive antibodies of the immunoglobulin G2a isotype. Bulk cultures of purified CD4+ lymphocytes from mice infected with either mutant were compared for their ability to produce gamma interferon (IFN-gamma), interleukin-2 (IL-2), IL-4, and IL-6 in vitro. After stimulation with specific antigen, CD4+ cells from Vir- 3-immunized mice released large amounts of the Th1-specific cytokines, IFN-gamma and IL-2, at a time when CD4+ cells from Vir- 13-infected mice predominantly secreted the characteristic Th2 cytokines, IL-4 and IL-6. These results were confirmed by quantitative analysis of cytokine-producing Th1 and Th2 cells. In addition, only mice infected with Vir- 3 displayed a high frequency of CD8+ cells with the potential for in vitro lysis of yeast-primed bone marrow macrophages. Purified CD4+ cells from Vir- 3-infected mice, but not a mixture of these cells with CD4+ lymphocytes from mice infected with Vir- 13, could adoptively transfer delayed-type hypersensitivity reactivity onto naive mice. Taken together, these data suggest that both Th1 and Th2 CD4+ lymphocytes may be activated during experimental C. albicans infection in mice.

Treatment of murine invasive candidiasis with amphotericin B and cilofungin: evidence for enhanced activity with combination therapy

The in vivo interactions of cilofungin, an echinocandin antifungal agent, and amphotericin B, a polyene derivative, in a murine model of disseminated candidiasis have been investigated. While single therapy with either drug alone prolonged survival of infected mice, kidney colony counts were not appreciably reduced. In contrast, combination therapy, especially at higher doses of both drugs, resulted in significant prolongation of survival and suppression of growth of yeast cells in the kidneys. Combination therapy of experimental candidiasis with cilofungin and amphotericin B did not result in antagonism; rather, additive or synergistic effects were seen. Future preclinical work with other echinocandin and polyene derivatives should include studies evaluating the in vivo interactions of both classes of compounds.

TH1 and TH2 cytokines in murine candidiasis: [formula omitted] Dept.Experimental Medicine and Biochemical Sciences, Microbiology section, University of Perugia, ITALY

TH1 and TH2 cytokines in murine candidiasis: [formula omitted] Dept.Experimental Medicine and Biochemical Sciences, Microbiology section, University of Perugia, ITALY

Interactions of amphotericin B and SCH 39304 in the treatment of experimental murine candidiasis: lack of antagonism of a polyene-azole combination

Mice infected intravenously with Candida albicans were treated with SCH 39304, a new triazole antifungal compound, amphotericin B, or both. Two dose levels of each drug were evaluated in an attempt to identify potential helpful or harmful effects on survival and kidney colony counts. Contrary to theoretical predictions, combination therapy was not antagonistic and some additive or synergistic effects were observed. The results obtained in this study suggest that antagonism between polyene and azole antifungal drugs is not inevitable and that additive or synergistic effects may be possible.

Macrophage colony-stimulating factor in murine candidiasis: serum and tissue levels during infection and protective effect of exogenous administration

Serum and tissue concentrations of the macrophage-specific colony-stimulating factor (CSF-1) and the number of CSF-1-responsive cells in bone marrow were investigated in mice chronically infected with a low-virulence strain of the opportunistic zoopathogenic yeast Candida albicans. CSF-1 levels in serum, brain, kidney, liver, and lung were significantly increased shortly after infection and remained elevated during the 2 weeks preceding the onset of specific T cell-dependent immunity. The number of monocytic precursor cells was also increased in the bone marrow of infected mice. When macrophages from naive donors were exposed in vitro to purified murine CSF-1, their anticandidal activity in vitro appeared to be enhanced. CSF-1 was also administered in vivo to prospective recipients of a lethal C. albicans challenge. The results showed that the factor could effectively potentiate the animals' resistance to the yeast, as shown by increased survival times and reduced recovery of viable C. albicans from the organs of the CSF-1-treated mice. Therefore, the present data suggest that CSF-1 is likely to contribute to early resistance to fungal infection and could be successfully exploited in experimental models of antifungal immunotherapy.

Murine candidiasis: Sex differences in the severity of tissue lesions are not associated with levels of serum C3 and C5

Mice deficient in the fifth component of complement are known to be extremely susceptible to lethal challenge with Candida albicans. However, male mice, that have significantly higher concentrations of serum C5 than females, were markedly more susceptible to infection. This difference was observed in both susceptible (CBA/H) and resistant (BALB/c) mice. Levels of serum C3 likewise showed no correlation with susceptibility.

Murine candidiasis: Susceptibility is associated with the induction of T cell‐mediated, strain‐specific autoreactivity

Inbred mice can be classified as susceptible or resistant to systemic infection with the yeast Candida albicans by histopathological evaluation of tissue lesions. Candida-specific memory T cell responses generated by resistant BALB/c mice are vigorous and sustained, whereas those displayed by susceptible CBA/H mice are weak. When spleen cells from immune mice were activated by culture with candida antigens in vitro, and injected into syngeneic and allogeneic recipients in the absence of further antigenic stimulation, cells from CBA/H mice induced a specific inflammatory response only in CBA/H recipients. In contrast, cells from immune BALB/c mice showed no specific activity. The effector cells were identified as T cells of the cytotoxic/suppressor subclass (CD4-, CD8+); and analysis in various F1 hybrid mice showed that reactivity was expressed only in animals carrying CBA/H genes. The data thus indicate that susceptibility to C. albicans infection is associated with the induction of a T cell subpopulation that has the potential to react specifically against unmodified self antigens expressed by the susceptible strain.

Comparative effects of cilofungin and amphotericin B on experimental murine candidiasis

The effectiveness of cilofungin (LY121019, referred to hereafter as LY), a lipopeptide, was studied in a murine candidiasis model. CD-1 mice (5 weeks old) were injected intravenously with 3 x 10(5) Candida albicans yeast cells. Intraperitoneal LY or amphotericin B (AmB) therapy was begun 4 days after infection and was continued daily for 2 weeks. LY and AmB were compared at 62.5, 6.25, and 0.625 mg/kg per day, with the LY dose split into two treatments per day. Mice were observed for 30 days postinfection, and survivors were necropsied. AmB at 62.5 mg/kg per day was lethal in the absence of infection. Cumulative mortality for infected controls was 94% (17 of 18). Survival of mice treated with the control diluent for LY was the same as survival with no treatment. Survival after 0.625 mg of LY per kg per day was the same as that of the controls, and 6.25 or 62.5 mg of LY per kg per day was significantly superior. AmB treatment at 0.625 or 6.25 mg/kg per day was protective and superior to the same LY doses. Atrophied kidneys were common in AmB-treated mice, and mice treated with 6.25 mg of AmB per kg per day appeared ill during therapy. The number of CFU recovered from kidneys and spleens of surviving mice reflected the same relationships between drugs and doses as those described for mortality. C. albicans was not cleared from the kidneys of mice in any group, and only in the 6.25-mg/kg-per-day AmB treatment group was not detectable C. albicans found in the spleens. These data indicate that LY or AmB suppresses candida infection but neither is curative in this model.

Murine candidiasis: Cell‐mediated immune responses correlate directly with susceptibility and resistance to infection

Cell-mediated immune responses were evaluated after immunization in two inbred mouse strains, CBA/H and BALB/c, that are respectively susceptible and resistant to infection with the yeast Candida albicans. Local immune responses, as measured by leucocytic infiltration into the draining lymph node, were similar; however, both delayed-type hypersensitivity responses and candida-specific lymphocyte proliferation in vitro were significantly stronger in the resistant strain. The response was controlled by genes mapping outside the major histocompatibility complex. A possible explanation for the down regulation of the immune response in CBA/H mice is discussed.

Liposome-encapsulated amphotericin B in the treatment of experimental murine candidiasis.

The efficacy of liposome-encapsulated amphotericin B in treating experimental murine candidiasis was compared with that of the commercially available amphotericin B (Fungizone). The LD50 of liposomal amphotericin B in ddY mice exceeded 10.0 mg/kg while that of Fungizone was 3.0 mg/kg. Experimental candidiasis was induced by injecting a clinical isolate of Candida albicans strain 0925-107-01, through the tail vein. With the injection of 1.7 x 10(6) colony forming units, the number of colonies in the kidneys remained between 2.1 x 10(5) and 1.2 x 10(6), whereas the number of colonies in blood, liver, spleen, lungs and heart decreased rapidly. Histological examination revealed severe pyelonephritis with fungal infiltration and a mild invasion of the heart, lungs, liver and spleen. The survival rate of mice with experimental candidiasis treated with Fungizone at a dose of 0.8 mg/kg was 50% (the maximum tolerated dose without acute lethality), whereas all mice treated with the liposomal amphotericin B at a dose of 5.0 mg/kg were alive even 42 days after the inoculation (p less than 0.01). Using liposome as a carrier for amphotericin B decreased this drug's systemic toxicity making it possible to administer doses higher than feasible with the commercial preparation and thus obtaining better therapeutic efficacy.

Treatment of experimental murine candidiasis with liposome-encapsulated amphotericin B

Multilamellar liposomes composed of phosphatidyl choline, phosphatidic acid and cholesterol at a molar ratio of 4:1:4 were prepared so as to entrap a solution of amphotericin B (AMB) and its efficacy in the treatment of murine systemic candidiasis were studied. There were marked differences in susceptibility to systemic candidiasis among several strains of mice. The number of cultivable Candida albicans increased remarkably in the kidney up to 6.4 X 10(5) c.f.u./g, but not so marked in the lung, when challenged i.v. with 3.7 X 10(5) fungal cells into a relatively resistant strain BALB/C mice. Liposome-encapsulated amphotericin B (L-AMB) permitted larger doses of AMB to be administered without the occurrence of the acute anaphylaxis-like and subacute toxicity as expressed by a decreased renal function. The mice treated with a single injection of 4 mg/kg of L-AMB showed the prolonged survival after challenge. The results obtained showed that the use of liposomes as a drug delivery system for AMB would improve significantly the therapeutic efficacy of the antibiotic against candidiasis.

Effect of attachment of anticandidal antibody to the surfaces of liposomes encapsulating amphotericin B in the treatment of murine candidiasis.

The effect produced by antibody specific to Candida albicans when attached to liposomes containing amphotericin B was studied in vivo. Liposomal amphotericin B bearing specific immunoglobulin (LAMB-Ab) was compared with the unencapsulated drug (fAMB) and other liposomal amphotericin B formulations in the short-term survival (21 days) of mice with disseminated candidiasis. Both the treatment and prophylaxis of the murine model of candidiasis were explored in these trials. LAMB-Ab increased survival rates in the model more than other liposomal preparations containing amphotericin B. Liposomal amphotericin B compounds as a group prolonged survival over fAMB. Liposomal preparations used for comparison included liposomes with attached nonspecific antibody (LAMB-Ab-), liposomes without antibody (LAMB), and liposomes with unattached specific antibody (LAMB+).

Scanning electron microscopy of epidermal adherence and cavitation in murine candidiasis: a role for Candida acid proteinase.

Adherence of blastoconidia to epidermal corneocytes is an early event in Candida colonization and infection of the skin. Pathogenic species adhere more avidly than nonpathogenic species, transform to hyphal growth, and invade the stratum corneum of the skin. Adherence was studied by scanning electron microscopy of experimental murine cutaneous Candida infections, using six species of Candida. Candida albicans and C. stellatoidea blastoconidia, applied to newborn mouse skin, adhered to the stratum corneum in greater numbers than other species tested, acquired fibrils and strands of amorphous mucinlike material ("cohesin") between spores and the corneocyte cell surface, formed cavitations in the corneocyte surface, and invaded the corneocyte envelope by hyphal growth at sites distant to the point of blastoconidia attachment. Other species showed little or no adherence, colonization, or cavitation of the corneocyte surface, except C. tropicalis, which showed intermediate results. Pepstatin, an inhibitor of Candida acid proteinase, did not alter adherence or cohesion formation, but inhibited formation of corneocyte cavitations about adherent blastoconidia, suggesting that this enzyme may facilitate adherence/invasion events on skin. Depletion of surface lipids did not alter the formation of cohesin material or the adherence process. Adherence and invasion of epithelium by pathogenic Candida species include the interaction of blastoconidia with an epithelial surface cohesin material that participates in the adherence process. Candida acid proteinase, a keratinolytic enzyme, may participate in the cavitation process of the corneocyte surface by C. albicans.

Effect of nucleotide restriction and supplementation on resistance to experimental murine candidiasis.

The influence of dietary nucleotides on susceptibility to candidiasis in mice was studied using two criteria: animal survival and recovery of viable Candida albicans organisms from the kidney and spleen. One-month-old mice were placed on one of five diets with varying nucleotide content. The results show that mice maintained on a nucleotide-free diet (NF) exhibit a significantly decreased mean survival time and a significantly increased viable organism recovery in the spleen following intravenous injection of graded inocula of C. albicans compared to mice fed diets containing RNA or uracil as a nucleotide source.