Biomedical subjects

F Bistoni

Publications and source records attributed to F Bistoni.

At least 37 records · Page 2Linked to original sources

PubMed2000

Influence of interferon-gamma administration on the severity of experimental group B streptococcal arthritis.

OBJECTIVE: To assess the effect of interferon-gamma (IFNgamma) administration on the evolution of systemic infection and septic arthritis induced by group B streptococci (GBS) in mice. METHODS: CD1 mice were inoculated intravenously with arthritogenic strain 1/82 of type IV GBS. Exogenous murine IFNgamma or anti-IFNgamma monoclonal antibodies were administered intravenously either 2 hours (-2 hours) before or 18 hours after infection with 1 x 10(7) GBS. Mice were monitored daily for survival and for signs of arthritis. In a subsequent set of experiments, mice were killed at selected times for examination of bacterial clearance, joint histopathology, and cytokine production. RESULTS: Mortality in mice treated with IFNgamma at -2 hours was 100%, compared with 20% in those treated at 18 hours and with 40% in controls. As indicated by the arthritis score, mice treated with IFNgamma at -2 hours developed early and more severe arthritis, whereas those treated at 18 hours had milder arthritis compared with infected controls. Less severe joint pathology in the mice treated with IFNgamma at 18 hours correlated with low levels of interleukin-6 (IL-6) and IL-1beta and a low bacterial load in the joints, whereas rapid onset and worsening of articular lesions in those treated at -2 hours corresponded to early and sustained levels of IL-6. CONCLUSION: The findings of this study demonstrate that the effects mediated by IFNgamma on GBS-induced arthritis may be detrimental or beneficial, depending on the time of administration of IFNgamma in relation to infection with the antigen.

Animals↗

PubMed2000

Involvement of platelets in experimental mouse trypanosomiasis: evidence of mouse platelet cytotoxicity against Trypanosoma equiperdum.

Platelets play an important role in the human response to parasites. Trypanosoma equiperdum, a parasite that has the horse as its natural host, is able to induce infection in mice and thus it may represent a simple model for studying the role of platelets in the development of a parasitosis. Although several aspects of the murine response to T. equiperdum infection have been clarified, the precise mechanism of killing of the parasite is still unclear. We have studied the involvement of blood platelets in experimental murine infection with T. equiperdum. Infected mice show a progressive decrease of the number of circulating platelets. The production of thromboxane A2 (TxA2) by platelets stimulated with collagen decreases progressively with the progression of T. equiperdum infection, compatible with in vivo platelet activation or with a possible antagonistic effect by trypanosomes on the production of TxA2. Finally, mouse platelets exert in vitro a direct parasitocidal activity on T. equiperdum at ratios >/=20:1. Complement fractions do not enhance platelet trypanocidal activity, whereas IgM fractions do, at least in short-term coincubation experiments. Our data show that platelets are involved in experimental murine T. equiperdum infection and confirm that platelet parasitocidal activity is a generalized phenomenon in mammals.

Analysis of Variance↗

PubMed2000

Dysregulation in IL-12 secretion by neutrophils from HIV-infected patients.

It is generally believed that neutrophils from HIV-infected patients are functionally competent, but several studies have shown impairment in neutrophil fungal killing and cytokine production. In this study we evaluated the ability of neutrophils from healthy donors and HIV-infected patients to produce IL-12 in response to stimulation with Candida albicans, lipopolysaccharide (LPS) and Cryptococcus neoformans (acapsular and encapsulated), with and without MoAb opsonization. Neutrophils from healthy donors secreted IL-12 in response to LPS or C. albicans but not in response to encapsulated or acapsular C. neoformans, regardless of MoAb opsonization. Surprisingly, neutrophils from HIV-infected patients demonstrated constitutive IL-12 production, although these cells were not responsive to LPS stimulation. The inability of MoAb to C. neoformans capsular polysaccharide to promote IL-12 production by neutrophils excludes phagocytosis and/or CD16 cross-linking in this process, and distinguishes neutrophils from monocytes. Our results provide additional evidence for cytokine dysregulation in neutrophils from HIV-infected patients. Furthermore, the IL-12 response of neutrophils and monocytes to CD16 stimulation appears to be different, suggesting differences in the role of these phagocytic cells during the inflammatory response.

AIDS-Related Opportunistic Infections↗

PubMed2000

Host immune reactivity determines the efficacy of combination immunotherapy and antifungal chemotherapy in candidiasis.

In immunocompetent mice with candidiasis, successful therapy with amphotericin B and fluconazole relies on the induction of protective, T helper (Th) type 1 responses, an effect potentiated by concomitant interleukin (IL)-4 neutralization. To assess the therapeutic efficacy of combined treatments with antifungals and immunomodulators in conditions of immunosuppression, leukopenic or neutropenic mice with disseminated candidiasis were treated with amphotericin B or fluconazole alone or in combination with soluble IL-4 receptor (sIL-4R) or recombinant (r) IL-12 or IL-10 neutralizing monoclonal antibodies. We found that (1) the synergistic effect of sIL-4R and antifungals is retained in immunocompromised mice; (2) synergism with amphotericin B was superior to that with fluconazole, particularly in leukopenic mice; (3) rIL-12 synergized with fluconazole in neutropenic mice; and (4) IL-10 neutralization was always of limited efficacy. This study indicates that the therapeutic efficacy of antifungals is differentially potentiated by cytokines or cytokine antagonists and is influenced by host immune reactivity.

Amphotericin B↗

PubMed2000

Early induction of interleukin-12 by human monocytes exposed to Cryptococcus neoformans mannoproteins.

Interleukin-12 (IL-12) production by human monocytes stimulated with mannoproteins (MPs) of Cryptococcus neoformans was investigated. The results reported show that secreted or cell-associated MPs induce an early and significant production of IL-12. MPs show different capabilities to quantitatively affect IL-12 production; MP2, an 8. 2-kDa MP purified from the culture supernatant of C. neoformans, appears to be the most potent stimulator. Cytochalasin B inhibits both internalization and IL-12 induction by MP. In addition, a drastic reduction of IL-12 was observed when monocytes were cultured in the absence of normal human serum or treated with soluble mannan. Early production of IL-12 promotes early secretion of gamma interferon by T cells but does not influence the magnitude of the MP-induced lymphoproliferative response. Overall our results identify cryptococcal antigens responsible for rapid and potent induction of IL-12 in monocytes. MPs appear to regulate IL-12 secretion by internalization via the endocytic pathway and by interaction with monocyte receptors or serum factors.

Cryptococcus neoformans↗

PubMed2000

Interleukin 18 restores defective Th1 immunity to Candida albicans in caspase 1-deficient mice.

Caspase 1, formerly designated interleukin 1beta (IL-1beta)-converting enzyme, processes pro-IL-1beta and pro-IL-18 to yield active cytokines that play a pivotal role in inflammation and cell activation. We show here the effect of caspase 1 deficiency on the inflammatory and adaptive immune responses to the fungus Candida albicans. Caspase 1 deficiency did not affect susceptibility to primary systemic infection with the fungus, as revealed by survival and fungal growth. However, Th1-mediated resistance to reinfection was greatly impaired in caspase 1-deficient mice, and this correlated with low-level production of IL-12 and gamma interferon. Early in infection, production of these cytokines and that of tumor necrosis factor alpha, IL-6, and, interestingly, IL-1beta occurred normally in caspase 1-deficient mice, while that of IL-18 was severely impaired. Exogenous administration of IL-18, more than IL-12, restored the Th1-mediated resistance to the infection. We conclude that, while caspase 1 is not indispensable for release of mature IL-1beta in candidiasis, the caspase 1-dependent production of IL-18 may represent an important and novel pathway for the expression of sustained Th1 reactivity to the fungus.

Animals↗

PubMed2000

Two conserved amino acid motifs mediate protein targeting to the micronemes of the apicomplexan parasite Toxoplasma gondii.

The micronemal protein 2 (MIC2) of Toxoplasma gondii shares sequence and structural similarities with a series of adhesive molecules of different apicomplexan parasites. These molecules accumulate, through a yet unknown mechanism, in secretory vesicles (micronemes), which together with tubular and membrane structures form the locomotion and invasion machinery of apicomplexan parasites. Our findings indicated that two conserved motifs placed within the cytoplasmic domain of MIC2 are both necessary and sufficient for targeting proteins to T. gondii micronemes. The first motif is based around the amino acid sequence SYHYY. Database analysis revealed that a similar sequence is present in the cytoplasmic tail of all transmembrane micronemal proteins identified so far in different apicomplexan species. The second signal consists of a stretch of acidic residues, EIEYE. The creation of an artificial tail containing only the two motifs SYHYY and EIEYE in a preserved spacing configuration is sufficient to target the surface protein SAG1 to the micronemes of T. gondii. These findings shed new light on the molecular mechanisms that control the formation of the microneme content and the functional relationship that links these organelles with the endoplasmic reticulum of the parasite.

Amino Acid Motifs↗

PubMed2000

Cytokines in candidiasis and aspergillosis.

Both innate and T helper (Th) immunity play a central role in fungal infections. A bi-directional influence exists between the two compartments of the immune system, mainly occurring through cytokine production. On the one hand, protective Th1 or nonprotective Th2 cells mediate resistance or susceptibility to disseminated and localized fungal infections by secreting cytokines with activating or deactivating signals for effector phagocytic cells. On the other hand, cells of the innate immune system regulate the development of antifungal T helper responses by producing directive cytokines, such as interleukin (IL)-12 and IL-10. In experimental models of Candida albicans and Aspergillus fumigatus infections, the administration or neutralization of selective cytokines and the use of cytokine-deficient mice have revealed the existence of a hierarchical pattern of cytokine mediated regulation of antifungal Th cell development and effector function. A finely regulated balance of directive cytokines, rather than the relative absence of opposing cytokines, appears to be required for optimal development and maintenance of protective Th1 reactivity to fungi. Thus, it is conceivable that some cytokines may have beneficial or deleterious effects on infection, depending on the dose and timing of endogenous production or exogenous administration. A better understanding of the different, sometimes unexpected, roles of cytokines is required for their use in prophylaxis and therapy of fungal infections, either alone or in combination with antifungal agents.

Animals↗

PubMed2000

In vitro study of the efficacy of a two-way connection with disinfectant in the prevention of peritonitis.

A new connection system for continuous ambulatory peritoneal dialysis (CAPD) has been established, and its efficacy in preventing microbial contamination of the peritoneal cavity has been tested in vitro. The system consists of a Y-shaped channel formed in the bottom of a Plexiglas cup. The Luer-lock shaped ends of the Y-shaped channel are designed to host the connectors from the drainage bag, the catheter transfer set, and the bag of fresh dialysate. Because the connectors from the catheter transfer set and the fresh bag are located at the inner surface of the cup bed, and because the cup is filled with disinfectant during the entire exchange procedure, all at-risk steps are continuously protected by disinfectant (that is, removal of the caps from the connectors, connection and disconnection, replacement of the caps). Still, because the patient could inadvertently extract and contaminate one of the two connectors (although such a possibility is unlikely), the disinfecting efficacy of the system was tested in vitro. Despite contamination with various micro-organisms at the highest possible concentrations, all tests showed negative bacterial growth, thus confirming the absolute efficacy of the system in preventing exogenous transluminal peritonitis.

Bacteria↗

PubMed1999

Differential effector and secretory functions of microglial cell lines derived from BCG-resistant and -susceptible congenic mouse strains.

Using congenic strains of mice susceptible (bcg(s)) or resistant (bcg(r)) to BCG, murine microglial cell lines, RR4.R (BCG-resistant) and RR8.S (BCG-susceptible), were established in vitro. Comparative studies revealed that, although phagocytic to a similar extent, RR4.R cells were more active than RR8.S cells in terms of antimycobacterial activity. Interestingly, cells of resistant genotype secreted more nitric oxide, TNF-alpha and IL-12, but less IL-6, than susceptible cells, when stimulated with IFN-gamma alone or in combination with lipopolysaccharide. Nevertheless, no significant differences were observed between the two cell lines in terms of IL-1 beta or IL-10 secretion, or on assessment of cytokine production following exposure to a massive dose of lipopolysaccharide. Overall, these data provide the first evidence that resistant/susceptible genotype influences antimycobacterial activity, NO and cytokine production in microglial cells, the prototype of cerebral macrophages.

Animals↗

PubMed1999

The A-domain and the thrombospondin-related motif of Plasmodium falciparum TRAP are implicated in the invasion process of mosquito salivary glands.

Sporozoites from all Plasmodium species analysed so far express the thrombospondin-related adhesive protein (TRAP), which contains two distinct adhesive domains. These domains share sequence and structural homology with von Willebrand factor type A-domain and the type I repeat of human thrombospondin (TSP). Increasing experimental evidence indicates that the adhesive domains bind to vertebrate host ligands and that TRAP is involved, through an as yet unknown mechanism, in the process of sporozoite motility and invasion of both mosquito salivary gland and host hepatocytes. We have generated transgenic P.berghei parasites in which the endogenous TRAP gene has been replaced by either P.falciparum TRAP (PfTRAP) or mutated versions of PfTRAP carrying amino acid substitutions or deletions in the adhesive domains. Plasmodium berghei sporozoites carrying the PfTRAP gene develop normally, are motile, invade mosquito salivary glands and infect the vertebrate host. A substitution in a conserved residue of the A-domain or a deletion in the TSP motif of PfTRAP impairs the sporozoites' ability to invade mosquito salivary glands. Notably, midgut sporozoites from these transgenic parasites are still able to infect mice. Midgut sporozoites carrying a mutation in the A-domain of PfTRAP are motile, while no gliding motility could be detected in sporozoites with a TSP motif deletion.

Animals↗

PubMed1999

Antibody to capsular polysaccharide enhances the function of neutrophils from patients with AIDS against Cryptococcus neoformans.

OBJECTIVE: To determine the contribution of anti-glucuronoxylomannan monoclonal antibody (MAb18B7) to the fungicidal capacity of polymorphonuclear leukocytes (PMNL) from HIV-infected patients towards Cryptococcus neoformans. DESIGN: Killing activity and superoxide anion generation were evaluated in the presence or absence of MAb18B7 in an in vitro system. METHODS: Killing activity was determined by colony forming unit inhibition assay. Superoxide generation was measured in the presence or absence of zymosan, C. neoformans, or Candida albicans. CD16, CD32, and CD64 molecules on PMNL were evaluated by cytofluorometric analysis. RESULTS: MAb18B7 strongly influenced the phagocytic and killing activities against encapsulated C. neoformans and consistently enhanced superoxide anion generation. Expression of CD16, and to a lesser extent CD64, on PMNL was required for MAb18B7-induced superoxide generation. By blocking CD16 and CD64 molecules with anti-CD16 and anti-CD64 MAb, a significant down-regulation of MAb18B7-induced fungicidal activity was observed. CONCLUSIONS: Our results demonstrate that MAb18B7 selectively enhances the killing mechanisms of PMNL from HIV-infected patients against encapsulated C. neoformans. The availability of CD16 and CD64 molecules on PMNL plays a critical role.

Adult↗

PubMed1999

Granulocyte-macrophage colony-stimulating factor and fluconazole enhance anti-cryptococcal activity of monocytes from AIDS patients.

OBJECTIVE: To investigate the effect of human recombinant granulocyte-macrophage colony-stimulating factor (hrGM-CSF) and fluconazole on anti-cryptococcal activity of monocytes from AIDS patients and normal subjects. DESIGN: The effect of GM-CSF and fluconazole on fungistatic and fungicidal activity of monocytes was studied in an in vitro system. METHODS: Monocytes were treated in vitro with hrGM-CSF and fluconazole or either agent alone for 24 or 48 h, and fungistatic and fungicidal activity was evaluated in a colony-forming unit inhibition assay. CD11b/CD18 expression in monocytes was measured by flow cytometry analysis. Superoxide anion generation by peripheral blood monocytes was measured in the presence of pre-opsonized zymosan. RESULTS: Defective antifungal capacity of monocytes from AIDS patients was observed. GM-CSF treatment of monocytes from AIDS patients increased fungistatic activity, and the combination of hrGM-CSF and fluconazole resulted in fungicidal activity. The mechanisms involved in the GM-CSF-mediated effect appeared to be mediated by (i) enhancement of phagocytic activity, (ii) increase of superoxide anion generation, and (iii) upregulation of CD11b/CD18 expression on the monocyte surface. CONCLUSIONS: Our data highlight the effect of GM-CSF on anti-cryptococcal activity of human monocytes and show a synergistic effect of GM-CSF with fluconazole, suggesting a new therapeutic strategy in the treatment of cryptococcosis.

Acquired Immunodeficiency Syndrome↗

PubMed1999

Tetanus toxin impairs accessory and secretory functions in interferon-gamma-treated murine macrophages.

Tetanus neurotoxin (TT), a product of microbial origin, acts as a zinc endopeptidase on vesicle-associated membrane proteins (VAMP). We have demonstrated that TT displays inhibitory effects on secretory and accessory functions in the murine macrophage (Mphi) cell line GG2EE. Nitric oxide (NO) secretion was decreased when interferon (IFN)-gamma-pretreated GG2EE Mphis were coincubated with a fungal costimulus (SMP200) and TT. When heat-inactivated TT was used this effect was not evident. The TT-mediated phenomenon was dose-dependent and specific since, under the same experimental conditions, it did not affect interleukin-6 or tumor necrosis factor-alpha secretion. Furthermore, IFN-gamma-induced major histocompatibility complex class II molecule expression and GG2EE accessory function, assessed by SMP200-stimulated lymphoproliferation, were also inhibited by TT. Such inhibition was incomplete, in line with our previous results showing that TT partially cleaves VAMP proteins in murine Mφ.

Animals↗

PubMed1999

Differential effects of iron load on basal and interferon-gamma plus lipopolysaccharide enhance anticryptococcal activity by the murine microglial cell line BV-2.

Here we evaluated the influence of intracellular iron levels on the constitutive and interferon (IFN)-gamma plus lipopolysaccharide (LPS) enhanced anticryptococcal activity by the murine microglial cell line BV-2. We demonstrated that iron loading via ferric nitrilotriacetate (FeNTA) resulted in a significant increase in the constitutive levels of anticryptococcal activity, while the enhancing effects by IFN-gamma plus LPS were prevented. Accordingly, a major increase was observed in the levels of thiobarbituric reactive substance (TBARS) produced upon iron loading under basal conditions, whereas IFN-gamma plus LPS treatment, that per se did not affect TBARS production, prevented by about 50% the enhancement otherwise occurring in response to iron loading. The potential involvement of multiple effector system and their relation to intracellular iron will be discussed.

Animals↗

PubMed1999

Neutrophils from patients with advanced human immunodeficiency virus infection have impaired complement receptor function and preserved Fcgamma receptor function.

Interleukin (IL)-8 production by human polymorphonuclear leukocytes (PMNL) to Cryptococcus neoformans is related to complement activation. Generation of the bioactive fragments C3a and C5a is responsible for IL-8 release. IL-8 production was analyzed in response to C. neoformans by PMNL from persons with early- and late-stage (>400 and <200 CD4 cells/mm3, respectively) human immunodeficiency virus (HIV) infection who were at high risk for cryptococcosis. IL-8 release by PMNL from persons with early-stage infection and from healthy donors was similar; however, PMNL from persons with late-stage HIV infection had significantly impaired IL-8 production, which correlated with reduced IL-8 response to C3a and C5a proteins and decreased CD88 expression. Addition of murine monoclonal antibody (MAb) 18B7 promoted phagocytosis and restored IL-8 release consistent with integrity of FcgammaRIII. These results provide evidence for a selective defect in CD88 expression on PMNL from persons with late-stage HIV infection. However, Fcgamma receptor expression in PMNL appears to be intact and allows MAb to glucuronoxylomannan to positively influence PMNL function.

Adult↗

PubMed1999

Interleukin-4 causes susceptibility to invasive pulmonary aspergillosis through suppression of protective type I responses.

Aspergillus fumigatus, an opportunistic fungal pathogen, causes multiple allergic and nonallergic airway diseases. Invasive pulmonary aspergillosis (IPA) is a nonallergic, life-threatening disease of immunocompromised patients. In a murine model of IPA, interleukin (IL)-4-deficient (IL-4-/-) BALB/c mice were used to examine the role of IL-4 in lung pathology and immune responses. IL-4-/- mice were more resistant than wild-type mice to infection caused by multiple intranasal injections of viable A. fumigatus conidia. Resistance was associated with decreased lung inflammatory pathology, impaired T helper (Th)-2 responses (including lung eosinophilia), and an IL-12-dependent Th1 response. In contrast, development of host-detrimental antifungal Th2 cells occurred in IL-12-/- and interferon-gamma-/- mice and in IL-4-/- mice when subjected to IL-12 neutralization. These results demonstrate that IL-4 renders mice susceptible to infection with A. fumigatus by inhibition of protective Th1 responses. IL-4 appears to have a distinct role in the pathogenesis of allergic and nonallergic lung diseases caused by the fungus.

Animals↗

PubMed1999

A new azole derivative of 1,4-benzothiazine increases the antifungal mechanisms of natural effector cells.

The most widely used drug for treatment of candidiasis is fluconazole (FCZ). Recently, a new derivative of 1,4-benzothiazine, compound FS5, was developed. FS5 had an appreciable protective effect against murine candidiasis. The present study was designed to dissect the antifungal mechanisms triggered by FS5 and to establish whether this compound could enhance the antimicrobial abilities of natural effector cells. The results show that intraperitoneal injection of FS5 in mice (i) induced an increase in circulating neutrophil levels comparable to that observed in FCZ-treated mice; (ii) enhanced phagocytosis and the killing activities of macrophages (Mphis) isolated from the spleen or peritoneal cavity, with the latter effect correlating with induction of nitric oxide synthesis and production by Mphis; and (iii) increased the levels of expression and synthesis of tumor necrosis factor alpha. These results suggest that the compound-induced synthesis of antimicrobial and proinflammatory molecules by heterogeneous Mphi populations is part of the beneficial effect of FS5 exerted against murine candidiasis.

Animals↗