Biomedical subjects

D Pietrella

Publications and source records attributed to D Pietrella.

At least 19 recordsLinked to original sources

PubMed2001

Interdependency of interleukin-10 and interleukin-12 in regulation of T-cell differentiation and effector function of monocytes in response to stimulation with Cryptococcus neoformans.

We previously demonstrated that the principal component of capsular material of Cryptococcus neoformans, glucuronoxylomannan (GXM), induces interleukin-10 (IL-10) secretion from human monocytes. Here we report that encapsulation of the yeast with GXM is able to down-regulate interleukin-12 (IL-12) production by monocytes that would normally occur in the absence of encapsulation. This phenomenon appeared to be the result of inhibition of the phagocytic process by encapsulation with GXM as well as of negative signals such as IL-10 secretion produced by interaction of GXM with leukocytes. Decreased secretion of IL-12 correlated with decreased release of gamma interferon (IFN-gamma) from T cells, suggesting a role for encapsulation with GXM in hindering a T helper type 1 (Th1) response. This is supported by the ability of encapsulation with GXM to limit increased expression of B7-1 costimulatory molecules that otherwise might limit IL-10 secretion. Endogenous IL-10 played a critical role in modulatory activity associated with encapsulation with GXM. Blocking IL-10 with monoclonal antibody to IL-10 resulted in increased (i) IL-12 secretion, (ii) IFN-gamma release from T cells, and (iii) killing of C. neoformans by monocytes. These results suggest that encapsulation with GXM limits development of a protective Th1-type response, an inhibitory process in which IL-10 plays a critical role. Scavengers of GXM and/or IL-10 could be useful in a protective Th1-type response in patients with cryptococcosis.

Antigens, CD↗

PubMed2001

Cytotoxic T lymphocyte antigen costimulation influences T-cell activation in response to Cryptococcus neoformans.

The kinetics of cytotoxic T lymphocyte antigen 4 (CTLA-4) expression on T cells responding to Cryptococcus neoformans and its role in regulating the T-cell response were examined. Using peripheral blood mononuclear cells stimulated with encapsulated or acapsular C. neoformans we showed that (i) the encapsulated strain augmented CTLA-4 expression on the T-cell surface while the acapsular strain was a weaker modulator, (ii) CTLA-4 molecules were rapidly up-regulated after the addition of encapsulated C. neoformans, (iii) CTLA-4 was up-regulated predominantly in CD4+ T cells responding to C. neoformans, and (iv) blockage of CTLA-4 with (Fab')2 of monoclonal antibody to CTLA-4 induced T-cell proliferation that paralleled the enhancement of interleukin-2 and gamma interferon production. These results suggest that capsular material, the major virulence factor of C. neoformans, promotes synthesis and expression of CTLA-4 molecules predominantly in CD4+ T cells. CTLA-4-mediated deactivation is due not to lack of costimulation but to specific recognition of CTLA-4 for B7 molecules. This appears to be a new mechanism by which C. neoformans may elude the host immune response.

Abatacept↗

PubMed2001

Role of mannoprotein in induction and regulation of immunity to Cryptococcus neoformans.

Our previous observations showed that mannoprotein (MP) induces early and massive production of interleukin-12 (IL-12) in vitro. This study was designed to investigate whether this phenomenon could be applied in vivo and to determine the biological significance of MP in Cryptococcus neoformans infection. The results reported here show that MP treatment induces IL-12 secretion by splenic macrophages and IL-12 p40 mRNA in the brain. During C. neoformans infection, MP reinforced IL-12 and IFN-gamma secretion that coincided with enhanced antifungal activity of natural effector cells, early resolution of the inflammatory process, and clearance of fungal load from the brain. These studies show that MP is a key inflammatory mediator that induces a protective immune response against C. neoformans infection. This information can be used to facilitate the design of a rational approach to manipulate the immune response to C. neoformans.

Animals↗

PubMed2000

Normalization of anti-cryptococcal activity and interleukin-12 production after highly active antiretroviral therapy.

OBJECTIVE: To investigate the effect of highly active antiretroviral treatment (HAART) on antifungal and secretory functions of polymorphonuclear leukocytes (PMNL) from HIV-infected patients with high viral load. DESIGN: Antifungal activity, oxygen-dependent mechanisms and interleukin (IL)-12 secretion were evaluated in PMNL from HIV-infected patients before and 3 months after commencing HAART. METHODS: PMNL antifungal activity was evaluated by effects on fungal colony-forming units. Superoxide anion (O2-) production was determined by superoxide dismutase reduction and IL-12 was determined by enzyme-linked immunosorbent assay in supernatant fluids of PMNL cultured for 18 h. RESULTS: PMNL from HIV-infected patients showed dysregulation of antimicrobial and secretory functions. A selective defect in antimicrobial activity against encapsulated Cryptococcus neoformans correlated with baseline O2- overproduction, which drastically decreased upon microbial stimulation. Similarly, constitutive secretion of IL-12 was blocked by exposure to microbial products. PMNL analysed after 3 months of HAART showed restoration of antimicrobial activity against encapsulated C. neoformans, reduction in O2- formation by unstimulated cells and restoration of oxidative burst after appropriate stimulation, and reduction of IL-12 hypersecretion. CONCLUSIONS: PMNL from HIV-infected patients with high viral load have impaired function; HAART normalizes antimicrobial and secretory activities. The effects of HAART on innate immunity provide new prospects for reduction of HAART-mediated opportunistic infections.

Adult↗

PubMed2000

Interleukin-12 counterbalances the deleterious effect of human immunodeficiency virus type 1 envelope glycoprotein gp120 on the immune response to Cryptococcus neoformans.

The mechanism involved in the envelope glycoprotein gp120-induced Th2 response to Cryptococcus neoformans was investigated. Peripheral blood mononuclear cells (PBMC) from healthy donors were treated with human immunodeficiency virus gp120 and an encapsulated or acapsular strain of C. neoformans in the presence or absence of glucuronoxylomannan, the major capsular polysaccharide. gp120 inhibited early and late production of interleukin (IL)-12 by PBMC. This reduction paralleled IL-10 induction and inhibited translocation of CD40 to the surface of monocytes. Flow cytometric analysis revealed that gp120 down-regulated the expression of IL-12 receptor beta2 subunit on T cells responding to C. neoformans. Because the IL-12/IL-12 receptor beta2 subunit pathway is critical for the Th1 differentiation process, underexpression demonstrates that gp120 contributes to Th2 bias. Exogenous IL-12 added simultaneously with gp120 up-regulated interferon-gamma secretion and limited IL-4 production. These results suggest that gp120 limits the Th1 response to C. neoformans and that exogenous IL-12 could offset this effect.

CD40 Antigens↗

PubMed2000

T lymphocyte and monocyte interaction by CD40/CD40 ligand facilitates a lymphoproliferative response and killing of Cryptococcus neoformans in vitro.

This study explored the role of CD40 / CD40 ligand (CD40L) in the induction of a lymphoproliferative response and killing of Cryptococcus neoformans in vitro. In our experimental system, monocytes exposed to C. neoformans were used as antigen-presenting cells (APC) and co-cultured with autologous T cells. The results showed that CD40 / CD40L strongly regulated the blastogenic response of T cells to C. neoformans. The fungus up-regulated CD40 expression on APC. An acapsular strain appeared to be a better inducer than an encapsulated strain. Time course experiments showed optimal regulation of CD40 expression at 48 h of incubation. Blocking the interaction of CD40 on APC with CD40L on T cells using mAb to CD40L resulted in a significant inhibition of IFN-gamma production. The anti-cryptococcal activity of monocytes was greatly influenced by the CD40 / CD40L interaction, and a positive correlation was found between nitric oxide secretion and enhanced killing of C. neoformans. Finally, the CD40 / CD40L interaction was critical for induction of optimal secretion of pro-inflammatory cytokines such as TNF-alpha and IL-1beta. These results indicate an important role for CD40 / CD40L interaction in inducing activation of T cells. Such cell-to-cell contact promotes anti-cryptococcal activity as well as secretion of pro-inflammatory cytokines by monocytes.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1999

HIV type 1 envelope glycoprotein gp120 induces development of a T helper type 2 response to Cryptococcus neoformans.

OBJECTIVE: To analyse the contribution of HIV type 1 envelope glycoprotein gp120 to regulation of a T-cell response to Cryptococcus neoformans. DESIGN: Monocytes treated with recombinant gp120 and exposed to C. neoformans were used as antigen presenting cells (APC) in coculture with autologous T lymphocytes. METHODS: Costimulatory and major histocompatibility complex class II molecules were evaluated on APC by flow cytometry analysis. T-cell proliferation was determined as 3H thymidine incorporation. Cytokine production was analysed by enzyme-linked immunosorbent assay. RESULTS: gp120 had multiple effects on APC and the T-cell response including: (i) up-regulation of major histocompatibility complex class II antigens on the APC surface resulting from both redistribution of molecules from the intracellular pool and synthesis of new molecules; (ii) up-regulation of B7-2 molecules on the APC surface; (iii) altered T-cell proliferation; and (iv) promotion of interleukin-4 and inhibition of interferon-gamma synthesis and release. CONCLUSIONS: These data indicate that gp120 alters the normal T-cell response to C. neoformans, promoting a T-helper type 2 response. The altered T-cell response produced by gp120 may play an important role in the pathogenesis of cryptococcosis in the patient with AIDS.

Antigens, Fungal↗

PubMed1999

Specific activated T cells regulate IL-12 production by human monocytes stimulated with Cryptococcus neoformans.

IL-12 production mediated by a T cell-independent and/or T cell-dependent pathway was investigated in human monocytes responding to Cryptococcus neoformans. The data of this study showed that: 1) appreciable levels of IL-12 were observed when freshly isolated monocytes were exposed to acapsular C. neoformans or Candida albicans and secretion occurred within 24-48 h of incubation; 2) monocytes alone were poor producers of IL-12 when stimulated with encapsulated C. neoformans; 3) the presence of specific anti-glucuronoxylomannan mAb favored IL-12 secretion and Fc cross-linking could play a role; 4) monocytes were able to secrete consistent levels of IL-12 when cultured with activated T cells responding to C. neoformans; 5) the maximum secretion of IL-12 was observed at 5-7 days of culture and was strongly regulated by the presence of endogenous IFN-gamma; and 6) the interaction between CD40 on monocytes and CD40 ligand on activated T lymphocytes responding to C. neoformans played a critical role in IL-12 secretion. These data highlight the mechanisms of IL-12 production by human monocytes exposed to C. neoformans, indicating a possible biphasic secretion of IL-12, dependent on the direct effect of fungal insult, and characterized by consistent secretion of IL-12 that is dependent on the interaction of CD40 with the CD40 ligand expressed on activated T cells responding to C. neoformans.

Antibodies, Monoclonal↗

PubMed1999

B7 costimulatory ligand regulates development of the T-cell response to Cryptococcus neoformans.

The contribution of B7 molecules to the induction and maintenance of the T-cell response to the human pathogenic fungus Cryptococcus neoformans was investigated. T-cell activation by C. neoformans was regulated by B7 molecules. This costimulatory signal was necessary for initiation and maintenance of the T-cell response, through early and late requirements for B7-CD28 interaction. Blocking B7-2 inhibited the normal T-cell proliferative response. This inhibition was due, in part, to a reduced capability of T cells to produce interleukin-2 (IL-2). In contrast, the same T-cell population produced more interferon-gamma. Suppression of the normal lymphoproliferation and IL-2 secretion responses to encapsulated C. neoformans by antibodies to B7 was largely reversed by addition of the monoclonal antibody 2H1, that is reactive with the major capsular polysaccharide, glucuronoxylomannan. Overall, our data indicate that B7 molecules play a critical role in T-cell activation by C. neoformans and suggest that appropriate manipulation could drive T helper type 1 cell development.

Antibodies, Monoclonal↗

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↗

PubMed1998

Cryptococcus neoformans differently regulates B7-1 (CD80) and B7-2 (CD86) expression on human monocytes.

To induce a specific response in primary resting T cells, two signals must be provided by antigen-presenting cells (APC). The first antigen-specific signal is mediated by formation of the T cell receptor major histocompatibility complex molecule ternary complexes. The second signal is delivered by interaction of either B7-1 or B7-2 expressed by APC with CD28 or CTLA-4 on T cells. In this study, we examined the modulation of B7-1 and B7-2 molecules on human monocytes exposed to encapsulated or acapsular Cryptococcus neoformans or Candida albicans. In our experimental system, C. albicans or acapsular C. neoformans are able to induce B7-1 expression while the encapsulated yeast is a poor stimulator. A modest increase of B7-2 expression was also observed after monocyte treatment with acapsular C. neoformans or C. albicans, while the encapsulated yeast was ineffective in inducing B7-2 molecules. Kinetic analysis showed the maximum expression of B7-1 after 24 to 48 h. Addition of the opsonic IgG1 mAb 2H1 to monocytes and C. neoformans significantly increased B7-1, but not B7-2, expression. The contribution of B7-1 and B7-2 co-stimulatory (CS) molecules to cryptococcal-specific T cell activation was analyzed and a substantial inhibition of T cell proliferation was observed. In this study we provide the first demonstration of fungal interference in the regulation of CS molecules. Our results suggest a potential mechanism for poor inflammatory responses observed in C. neoformans infections.

Antigen Presentation↗

PubMed1998

Cryptococcus neoformans and Candida albicans regulate CD4 expression on human monocytes.

This study examined the capability of Candida albicans and Cryptococcus neoformans to modulate CD4 expression on human monocytes. C. albicans and an acapsular strain of C. neoformans induced higher levels of CD4 expression than encapsulated strains. Purified glucuronoxylomannan did not regulate CD4 expression on monocytes, but down-regulation of CD4 expression compared with stimulation by acapsular C. neoformans alone was observed when glucuronoxylomannan was used in combination with acapsular C. neoformans. The ability of opsonic factors to facilitate fungal-mediated CD4 overexpression suggests that binding or internalization (or both) of the yeast cells is a critical event. Protein synthesis was required, excluding redistribution of the intracellular pool of CD4 receptors to the cellular surface as the sole possible mechanism. Results demonstrate a new effect of fungi on professional phagocytic cells and raise the possibility that modulation of CD4 could influence gp120-mediated human immunodeficiency virus entry.

CD4 Antigens↗

PubMed1998

Human immunodeficiency virus type 1 envelope protein gp120 impairs intracellular antifungal mechanisms in human monocytes.

The key to success of fungal opportunistic pathogens in the immunocompromised host is related to survival inside phagocytic cells, which represent the first line of defense against microorganisms. The contribution of human immunodeficiency virus-1 recombinant envelope protein gp120 on effector functions of peripheral blood monocytes (PBM) against Candida albicans was investigated. gp120 binds CD4 receptors on PBM while not affecting the access of the fungus into the lysosome compartment. However, gp120 reduces the antifungal capacity of PBM. This phenomenon correlates with impaired oxygen-dependent antimicrobial machinery and reduced ability of phagolysosome acidification. The maintenance of phagolysosomal pH at approximately 6.2 restricts antimicrobial properties of the enzyme that work at a low pH, as evidenced by reduced antifungal capability of lysosomal protein extracted from gp120-treated PBM. These findings highlight gp120 perturbation of intracellular antimicrobial mechanisms of phagocytic cells and suggest a new aspect for gp120 in impairing immune functions.

AIDS-Related Opportunistic Infections↗

PubMed1998

Involvement of C3a and C5a in interleukin-8 secretion by human polymorphonuclear cells in response to capsular material of Cryptococcus neoformans.

In a previous paper we demonstrated that human polymorphonuclear cells (PMN) in the presence of normal human serum (NHS) secrete proinflammatory cytokines in response to Cryptococcus neoformans or its major capsular component, glucuronoxylomannan (GXM). The hypothesis that activation of the complement system could be responsible for the observed phenomenon is supported by the fact that encapsulated and acapsular C. neoformans isolates are activators of the complement system and, in particular, large encapsulated isolates are powerful activators. In the present study we demonstrate that (i) interleukin-8 (IL-8) release in response to acapsular or encapsulated strains of C. neoformans is significantly reduced in the presence of heat-inactivated serum rather than NHS and is completely abrogated in the absence of human serum; (ii) GXM-induced IL-8 release is strictly dependent on the presence of NHS, is inhibited by specific antibodies to either C3a and C5 complement components, and is completely abrogated by the combined use of these antibodies; (iii) the addition of purified C3a and C5a directly stimulates IL-8 release by PMN; and (iv) monoclonal antibody to GXM in combination with GXM or encapsulated C. neoformans potentiates IL-8 release by PMN. These data shed light on the mechanism involved in GXM-induced IL-8 secretion by PMN, provide an additional potential role for complement in the control of C. neoformans infections, and suggest a complex interplay between the complement system, humoral immunity, and cytokine regulation.

Cells, Cultured↗

PubMed1997

Monocyte dysfunction in patients with acquired immunodeficiency syndrome (AIDS) versus Cryptococcus neoformans.

In the present study we investigated the response of monocytes from AIDS patients, susceptible to cryptococcosis (<200 CD4 cells/microl), against Cryptococcus neoformans. Different patterns of response were observed in these cells compared to cells from healthy donors. In particular, fungicidal activity versus this fungus was impaired; this phenomenon could be due to the difficulty of monocytes to internalize C. neoformans in the presence of an intact complement system. Impairment of complement receptor type 3 and direct involvement of this receptor in phagocytosis of C. neoformans were found in monocytes from AIDS patients, which may account for the difficulty in phagocytosis of the fungus. Also, superoxide anion production was dramatically reduced in monocytes from AIDS patients. An increase of spontaneous tumor necrosis factor (TNF) production was evidenced after in vitro addition of C. neoformans. However, this did not activate the antifungal capacity of monocytes from AIDS patients. Moreover, cryptococcus-laden monocytes from AIDS patients were able to induce only a weak response of autologous T-lymphocytes. Hence, monocyte dysfunction could play a part in the progression of cryptococcosis in AIDS.

Acquired Immunodeficiency Syndrome↗

PubMed1996

Inhibition of fungicidal activity of polymorphonuclear leukocytes from HIV-infected patients by interleukin (IL)-4 and IL-10.

OBJECTIVE: To investigate the effect of human recombinant interleukin (hrIL)-4 or hrIL-10 on the functional status of polymorphonuclear leukocytes (PMNL) from normal subjects and HIV-infected patients. DESIGN: In an in vitro system we studied the effect of hrIL-4 or hrIL-10 on phagocytosis, fungicidal activity and superoxide anion production by PMNL. METHODS: PMNL were treated in vitro with hrIL-4 or hrIL-10 or their combination for 6 h and then candidacidal activity was evaluated in a colony-forming unit inhibition assay. Superoxide anion generation by PMNL was measured in the presence or absence of preopsonized zymosan or Candida albicans. RESULTS: Treatment in vitro with hrIL-4 or hrIL-10 of PMNL for 6 h was able to impair candidacidal activity of neutrophils in both normal or HIV-infected patients. The inhibitory effect was time- and dose-dependent and was more evident in PMNL from HIV-infected subjects, and reflected in these latter cells a decrease of superoxide anion generation. The impairment of candidacidal activity in PMNL from HIV-infected patients was accompanied by survival of the yeasts shown by budding formation into phagosomic organelles of cytokine-treated PMNL. CONCLUSIONS: Our data highlight new biological effects of IL-4 and IL-10 evidenced by suppressed effector function of neutrophils; this phenomenon is emphasized in HIV-infected patients suggesting a role for these cytokines in mediating increased susceptibility to microbial infection during AIDS progression.

Adult↗

PubMed1995

Beneficial effect of recombinant human granulocyte colony-stimulating factor on fungicidal activity of polymorphonuclear leukocytes from patients with AIDS.

The effect of recombinant human granulocyte colony-stimulating factor (rhG-CSF) administration on the functional status of polymorphonuclear leukocytes (PMNL) in neutropenic AIDS patients was investigated. PMNL destructive activity against Candida albicans or encapsulated or acapsular Cryptococcus neoformans was significantly impaired with respect to control subjects before rhG-CSF treatment. After subcutaneous administration of rhG-CSF (5 micrograms/kg), neutrophil counts increased 3- to 11-fold in 24 h and returned to baseline within 96 h. PMNL fungicidal activity showed significant enhancement 48-72 h after rhG-CSF administration that decreased to baseline within 96 h. Enhanced rhG-CSF-mediated destructive activity strictly correlated with augmented superoxide anion production by PMNL. These findings suggest that therapeutic use of rhG-CSF at appropriate schedules in neutropenic AIDS patients could decrease the risk of infection or, in association with antibiotic therapy, more rapidly resolve the occurring infections.

Acquired Immunodeficiency Syndrome↗

PubMed1995

Downregulation by cryptococcal polysaccharide of tumor necrosis factor alpha and interleukin-1 beta secretion from human monocytes.

The regulation by Cryptococcus neoformans encapsulation of interleukin 1 beta (IL-1 beta) and tumor necrosis factor alpha (TNF-alpha) production by human monocytes was investigated. By using encapsulated and acapsular C. neoformans, we demonstrated that both strains induce cytokine production, although the acapsular strain was a better stimulator than the thinly encapsulated strain. The cytokine levels produced by cells stimulated by the two strains were lower and followed a different kinetic than those stimulated by lipopolysaccharide (LPS). Purified capsular polysaccharide inhibits TNF-alpha secretion induced by LPS or acapsular C. neoformans. In contrast, no regulator effect on IL-1 beta was observed when LPS was used. The secretory response of these cytokines follows different pathways of macrophage activation; in fact, complete inhibition of TNF-alpha does not affect IL-1 beta production and vice versa. These data indicate that purified capsular polysaccharide of C. neoformans could contribute to the in vivo progress of cryptococcosis by suppressing cytokine production of macrophages and suggest that a therapeutic approach to address the suppressive effect of cryptococal polysaccharide could be devised.

Adult↗