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Biomedical subjects

F Bistoni

Publications and source records attributed to F Bistoni.

At least 127 records · Page 7Linked to original sources
PubMed1993

Tetanus toxin selectively impairs anti-tumoral but not anti-microbial macrophage-mediated effector functions.

The present study was designed to establish the susceptibility of macrophage-mediated effector functions to tetanus toxin (TT). Using the murine macrophage cell line, GG2EE, generated in vitro by v-raf/v-myc oncogenes, we have previously provided evidence that TT selectively inhibits interferon gamma (IFN-gamma), but not basal, lysozyme activity. Here we show that while neither phagocytic nor candidacidal activities are affected by TT treatment, antitumoral activity is significantly impaired after exposure to TT. This phenomenon, which is dose-dependent, is fully ascribed to the holotoxin, as heat inactivated TT, C or A-B fragments result ineffective. Furthermore, C but not A-B fragment competes with TT in abrogating its inhibitory effects. Overall, these data indicate that TT is not a broad-spectrum, down-regulating signal on macrophage-mediated functions, thus implying that its toxic action is exerted on specific molecular targets.

Animals↗
PubMed1993

Protective effect of picolinic acid on mice intracerebrally infected with lethal doses of Candida albicans.

We have studied the effects of picolinic acid (PLA), a product of tryptophan degradation, on mouse susceptibility to intracerebral infection with Candida albicans. We show that intraperitoneal administration of PLA significantly enhances the median survival time of mice inoculated with the lethal challenge. Furthermore, intracerebral administration of this agent induces a protective state against the local lethal infection, the phenomenon depending upon the administration schedule and doses of PLA employed. According to survival data, yeast growth in the brain as well as yeast colonization of the kidneys are drastically reduced in PLA-treated mice compared with those for untreated controls. Northern (RNA) blot analysis of brain tissues demonstrates that mRNA levels specific for tumor necrosis factor and interleukin 1 are augmented and induced, respectively, after inoculation of PLA. These results indicate that PLA has a protective effect likely involving elicitation of a cytokine response in vivo against fungal infections.

Animals↗
PubMed1993

Differential host susceptibility to intracerebral infections with Candida albicans and Cryptococcus neoformans.

To investigate the immune defense mechanisms employed against fungi in the brain, mice were experimentally infected by intracerebral inoculation of Candida albicans or Cryptococcus neoformans. Parameters such as median survival time and numbers of yeast cells in the brains were assessed for naive and immunomodulated mice. We found that no mice survived either C. albicans or C. neoformans challenge at doses of > or = 10(6) yeast cells per mouse. However, when the inoculum size was decreased (< or = 10(5) yeast cells per mouse), C. albicans was no longer lethal (100% survival), whereas 100 and 70% of the mice still succumbed to challenge doses of 10(4) and 10(3) C. neoformans yeast cells, respectively. Pharmacological manipulation and transfer experiments revealed that the myelomonocytic compartment had a minor role against C. neoformans but was deeply involved in the control of intracerebral C. albicans infection. By counting the number of yeast cells in the brains of naive and immunomodulated animals, we established that, unlike C. albicans, C. neoformans remained essentially in the brain, where massive colonization and damage occurred whether naive or immunomodulated defense mechanisms were employed by the host. Overall, these data suggest that the differential role of the myelomonocytic compartment, together with the diverse tropisms of the two fungi, can explain the different development and outcome of intracerebral C. albicans and C. neoformans infections.

Animals↗
PubMed1993

Toxic effects of tetanus toxin on GG2EE macrophages: prevention of gamma interferon-mediated upregulation of lysozyme-specific mRNA levels.

By using a nonneuronal cell system, evidence has previously been provided that tetanus toxin (TT) intoxication occurs in macrophages, impairing their secretory activity as well as their antitumoral activity. In particular, both secreted and total lysozyme (LZM) activities are reduced by TT treatment, provided that GG2EE macrophages have been preexposed to gamma interferon (IFN-gamma). In an attempt to provide insight into the molecular mechanisms underlying this phenomenon, we focused our attention on the levels of LZM-specific transcripts. GG2EE macrophages preexposed to IFN-gamma exhibited augmented levels of LZM-specific mRNA. Such an effect was detected 1 h after removal of IFN-gamma, peaked at 3 h, and gradually decreased with time in culture. Exposure of IFN-gamma-pretreated GG2EE macrophages to TT resulted in the prevention of the IFN-gamma-mediated upregulation of LZM mRNA levels. The phenomenon was mediated by the holotoxin (> or = 1 micrograms/ml) and abrogated by preexposure of the macrophages to the C fragment of TT. Protein kinase C (PKC) and Ca(2+)-calmodulin-dependent PK were likely involved in the IFN-gamma-mediated upregulation of LZM mRNA levels and biological activity, as assessed by PK inhibitors. Furthermore, PK inhibitors mimicked TT in impairing LZM activity of GG2EE macrophages, thus suggesting that impairment of PKC and/or the Ca(2+)-calmodulin-dependent PK pathway(s) may be one of the events involved in TT intoxication of macrophages.

Animals↗
PubMed1993

Natural killer cells do not play a dominant role in CD4+ subset differentiation in Candida albicans-infected mice.

The effects of in vivo administration of monoclonal antibodies against NK-1.1-bearing cells on the early production of gamma interferon (IFN-gamma) in vitro and development of Th1-associated immunity were studied in mice infected with a live vaccine strain of Candida albicans. At 1 and 4 days postinfection, natural killer (NK) cell-enriched fractions from the spleens of antibody-treated mice displayed a dramatic reduction in 5E6+ lymphocytes and negligible anti-YAC-1 cytotoxic activity in vitro. Nevertheless, the frequency of IFN-gamma-producing cells in those fractions was reduced by less than half, on average, by anti-NK-1.1 treatment in vivo. In addition, the antibody-treated and infected mice demonstrated unchanged T helper cell responses, as measured by yeast-specific footpad reactions, resistance to reinfection, occurrence of antibodies of different isotypes, and production in vitro of interleukin-2 (IL-2), IFN-gamma, IL-4, and IL-10 by CD4+ cells. Therefore, although NK cells may contribute to early IFN-gamma production in Candida-vaccinated mice, these cells apparently do not play a dominant role in the qualitative development of yeast-specific T helper responses.

Animals↗
PubMed1993

Inhibition of candidacidal activity of polymorphonuclear cells by alveolar macrophage-derived factor from lung cancer patients.

Culture supernatants of alveolar macrophages (AM) from lung cancer patients are able to inhibit the candidacidal activity of polymorphonuclear cells (PMN) in vitro. This phenomenon is ascribed to a factor secreted in the culture medium by unstimulated AM from tumor-bearing patients, but not from normal subjects. The inhibitor does not apparently affect the phagocytic activity of PMN, but the superoxide release during phagocytosis is significantly impaired when cells are pretreated with supernatants containing the factor. The secretion of the inhibitor seems to be restricted to the pulmonary compartment of lung cancer patients, since culture supernatants of peripheral blood monocytes (PBM) from the same subjects are not capable of depressing the candidacidal activity of PMN. The AM-derived factor is not inactivated after exposure to heat (60 degrees C) and when supernatants are analyzed by HPLC, the inhibitory activity is recovered in the fractions corresponding to a low molecular weight (800 D). In conclusion, AM from lung cancer patients are able to produce a factor capable of inhibiting the antimicrobial activity of PMN. This could account, at least in part, for the enhanced susceptibility to local infections observed in lung cancer patients.

Biological Factors↗
PubMed1993

Mechanism of intracellular candidacidal activity mediated by calcium ionophore in human alveolar macrophages.

In the present study, we investigated the effect of in vitro treatment with calcium ionophore (A23187) on candidacidal activity of human alveolar macrophages (AM) from normal subjects. In vitro incubation of AM with A23187 results in a significant dose-dependent enhancement of candidacidal activity. The availability of Ca2+ and Mg2+ ions in the culture medium is crucial for phagocytosis and killing to occur, but appears irrelevant for the binding between Candida albicans and AM. Enhancement of the killing effect mediated by A23187 does not correlate with increased phagocytic activity; in fact, the availability of ions is required for the phagocytic event, but an increase of cations does not correlate with enhancement of this activity. On the contrary, the augmentation of killing activity correlates with increased production of superoxide anion. Moreover, soluble material endowed with candidacidal activity has been extracted from cytoplasmic granules of AM both unstimulated and following A23187 treatment in vitro. Indeed, the granules extracted contain cationic proteases and, when isolated from stimulated cells, appear to be significantly more cytotoxic for C. albicans with respect to those obtained from unstimulated AM. In conclusion, the results reported here show that the phagocytic and killing events are ion dependent and the enhancement of intracellular candidacidal activity mediated by A23187 in AM is correlated with an augmented anti-Candida activity of cation-activated proteases.

Adult↗
PubMed1992

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.

Animals↗
PubMed1992

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.

Animals↗
PubMed1992

Involvement of the Th1 subset of CD4+ T cells in acquired immunity to mouse infection with Trypanosoma equiperdum.

Heat- or merthiolate-inactivated Trypanosoma equiperdum was administered to recipient mice that were subsequently challenged with viable inocula of the same stabilate. Only mice inoculated with merthiolate-killed parasites were completely protected from a challenge inoculum of 10(3) trypanosomes, an effect that was abolished by prior immunosuppression of mice. Immune sera from protected animals contained high levels of interferon (IFN)-gamma and specific IgG2a antibodies. Spleen cells from these mice produced high amounts of interleukin (IL)-2 and IFN-gamma in vitro in response to specific antigen or concanavalin A, whereas splenocytes from mice receiving heat-killed parasites produced high amounts of IL-6. In contrast, the production of tumor necrosis factor (TNF)-alpha and colony-stimulating activity (CSA) was not significantly different in mice receiving either killed parasite preparation. The protection in immunized mice was associated with the detection of strong delayed-type hypersensitivity (DTH) to T. equiperdum antigens, an effect that could be adoptively transferred onto naive recipients by specifically immune CD4+ lymphocytes. These results suggest that the development of protective immunity in mice to T. equiperdum by our immunization protocol may involve the activity of helper/DTH T cells, particularly those of the Th1 subset.

Animals↗
PubMed1992

Candida albicans hyphal form enhances tumor necrosis factor mRNA levels and protein secretion in murine ANA-1 macrophages.

We have demonstrated that Candida albicans in its hyphal form (H-Candida) acts as a stimulating agent in the cloned macrophage population ANA-1. Both tumor necrosis factor (TNF) mRNA levels and secreted biological activity augment in ANA-1 macrophages exposed to H-Candida. Such effects are observed at an effector-to-target cell ratio of 1:1 and occur after 1 and 3 hr of coincubation, respectively. The phenomenon is independent of the metabolic status of the fungus, since viable as well as heat-killed H-Candida are comparable in inducing TNF mRNA levels. The extent and kinetics of H-Candida-mediated effects are similar to those observed following exposure of ANA-1 macrophages to lipopolysaccharide (LPS). This implies that C. albicans in its hyphal form is a potent macrophage modulator; whether it acts through the same mechanism(s) as LPS remains to be elucidated.

Animals↗
PubMed1992

Drug-induced modulation of IL-2 production in experimental murine trypanosomiasis.

In this study we evaluated the effects of N-acetyl-cysteine and indomethacin in restoring IL-2 producing ability in vitro of splenocytes from mice infected with Trypanosoma equiperdum. Spleen cells from these mice were found to produce significantly lower levels of interleukin-2 (IL-2) in response to mitogen stimulation than spleen cells from uninfected control mice. This was accompanied by considerable suppression of IL-2-receptor expression, which was not attributable to the elimination of a particular T-cell subset. Impairment of IL-2 production was not due to a primary defect in L3T4+ T-cells, but rather to the presence of both adherent and non-adherent suppressor cells that apparently acted via prostaglandin-independent and dependent mechanisms. In fact, the IL-2-producing ability of lymphocytes from infected mice could be efficiently restored by in vitro exposure to N-acetyl-cysteine or indomethacin.

Acetylcysteine↗
PubMed1992

Course of primary candidiasis in T cell-depleted mice infected with attenuated variant cells.

Anti-CD4, anti-CD8, or anti-interferon-gamma (IFN-gamma) antibodies or combinations of them were administered in the early stages of chronic infection of mice with a Candida albicans live vaccine strain, and the animals were monitored for course of primary infection, development of delayed-type hypersensitivity, resistance to reinfection, production of interleukin 2 (IL-2) and IFN-gamma in vitro by splenic lymphocytes, and levels of IL-2 and IFN-gamma transcripts in these cells. CD4+ cell and IFN-gamma depletion resulted in the development of fatal candidiasis by the attenuated yeast vaccine. In contrast, either treatment alone modified the course but not the outcome of primary infection, though each prevented the development of resistance to reinfection. Our data thus indicate that both IFN-gamma and CD4+ cells participate in resistance to primary infection with attenuated yeast cells and are critical in the induction of persistent systemic anticandidal immunity.

Animals↗
PubMed1992

Gamma interferon modifies CD4+ subset expression in murine candidiasis.

A single injection of monoclonal antibody to gamma interferon administered in conjunction with a live Candida albicans yeast cell vaccine resulted in the detection of nonprotective Th2 rather than protective Th1 responses and altered the early expression of interleukin 4 and gamma interferon mRNA in CD4+ cells.

Animals↗
PubMed1992

Early differential molecular response of a macrophage cell line to yeast and hyphal forms of Candida albicans.

The dimorphic transition of Candida albicans from the yeast (Y-Candida) to the hyphal (H-Candida) form is a complex event; the relevance of this transition in fungal pathogenicity is still poorly understood. By using a cloned macrophage cell line (ANA-1), we questioned whether the interaction between macrophages and Y-Candida or H-Candida could affect specific cell functions, i.e., tumor necrosis factor and lysozyme production. We found that ANA-1 macrophages selectively responded to H-Candida with increased tumor necrosis factor and downregulated lysozyme, as assessed by measurement of relative mRNA levels and secreted biological activities. The H-Candida-mediated effects were (i) dependent upon the ratio between ANA-1 macrophages and H-Candida, (ii) detectable after 1 h of coincubation, and (iii) accomplished without fungal ingestion. Conversely, Y-Candida, which was found inside the ANA-1 macrophages, did not affect tumor necrosis factor and lysozyme production, nor did it prevent the macrophage response to other stimuli. Overall, these results indicate that a macrophage can distinguish between Y-Candida and H-Candida and that only the latter is able to modulate specific functions. H-Candida is recognized and probably processed as an extracellular target. The possible implication of macrophages as autocrine and paracrine regulatory cells during Candida infections is discussed.

Animals↗
PubMed1992

Experimental model of intracerebral infection with Cryptococcus neoformans: roles of phagocytes and opsonization.

A murine model of intracerebral (i.c.) infection with Cryptococcus neoformans in which naive mice receiving an i.c. fungal inoculation developed a severe disease has been established. The effect was strictly dependent on the number of microorganisms injected and evolved as lethal meningoencephalitis. Murine susceptibility to i.c. infection with C. neoformans was enhanced by treatment with chloroquine and colchicine, agents known to greatly affect the host phagocytic compartment. Furthermore, the life spans of both naive and drug-treated mice were significantly augmented when opsonized fungi were injected. Therefore, phagocyte-mediated mechanisms are likely involved in local resistance to i.c. infection with C. neoformans. Further support for this conclusion was supplied by in vitro data showing that microglial cells were proficient anticryptococcal effectors, provided opsonized microorganisms were used.

Animals↗