Reaction kinetics and targeting to cellular glutathione S-transferase of the glutathione peroxidase mimetic PhSeZnCl and its D,L-polylactide microparticle formulation.

Catalytic properties and cellular effects of the glutathione peroxidase (GPx)-mimetic compound PhSeZnCl or its d,l-lactide polymer microencapsulation form (M-PhSeZnCl) were investigated and compared with the prototypical Se-organic compounds ebselen and diselenide (PhSe)2. PhSeZnCl was confirmed to catalyze the ping-pong reaction of GPx with higher Vmax than ebselen and (PhSe)2, but the catalytic efficiency calculated for the cosubstrates glutathione (GSH) and H2O2, and particularly the high reactivity against thiols (lowest KM for GSH in the series of test molecules), suggested poor biological applicability of PhSeZnCl as a GPx mimetic. Cytotoxicity of PhSeZnCl was demonstrated in various cancer cell lines via increased reactive oxygen species (ROS) generation, depletion of intracellular thiols, and induction of apoptosis. Experiments carried out in GSH S-transferase P (GSTP)-overexpressing K562 human erythroleukemia cells and in GSTP1-1-knockout murine embryonic fibroblasts (MEFs) demonstrated that this cytosolic enzyme represents a preferential target of the redox disturbances produced by this Se-compound with a key role in controlling H2O2 generation and the perturbation of stress/survival kinase signaling. Microencapsulation was adopted as a strategy to control the thiol reactivity and oxidative stress effects of PhSeZnCl, then assessing applications alternative to anticancer. The uptake of this "depowered" GPx-mimetic formulation, which occurred through an endocytosis-like mechanism, resulted in a marked reduction of cytotoxicity. In MCF-7 cells transfected with different allelic variants of GSTP, M-PhSeZnCl lowered the burst of cellular ROS induced by the exposure to extracellular H2O2, and the extent of this effect changed between the GSTP variants. Microencapsulation is a straightforward strategy to mitigate the toxicity of thiol-reactive Se-organic drugs that enhanced the antioxidant and cellular protective effects of PhSeZnCl. A mechanistic linkage of these effects with the expression pattern and signaling properties of GSTP . This has overcome the GPx-mimetic paradigm proposed for Se-organic drugs with a more pragmatic concept of GSTP signaling modulators.

Microparticle-loaded neonatal porcine Sertoli cells for cell-based therapeutic and drug delivery system.

Neonatal porcine Sertoli cells (NPSC) are immune privileged cells showing innate phagocytic and antibacterial activities. NPSC have been shown capable of immunoaltering the body's response and possess lung homing capacity. These properties encourage investigation of NPSC as functional components of cell-based therapeutic protocols to treat lung infections and related complications. In this work, for the first time, NPSC were tailored to carry an antibiotic drug loaded into poly(d,l lactic) acid microparticles (MP). A loading protocol was developed, which afforded 30% drug uptake and high stability over time, with little or no effects on NPSC viability, morphology, reactive oxygen species production and DNA integrity. FSH receptor integrity, and TGFß (transforming growth factor ß) and AMH (anti-Müllerian hormone) expressions were unchanged after 1month of cryopreservation. Protein tyrosine kinase activation due to phagocytosis may have had resulted in changes in inhibin B expression. The activity of MP-loaded or NPSC alone against Pseudomonas aeruginosa was maintained throughout 1month of storage. NPSC couple an innate antibacterial activity with the capacity to embody drug loaded MP. We showed for the first time that engineered NPSC can be cryopreserved with no loss of their basic properties, thereby possibly representing a novel approach for cell-based therapeutic and drug delivery system.

Ag/AgCl nanoparticle decorated layered double hydroxides: synthesis, characterization and antimicrobial properties.

A layered double hydroxide (LDH) surface was employed as a substrate for growing silver nanoparticles (NPs). An efficient method to produce stable silver/silver chloride nanoparticles supported on the ZnAl-LDH surface was developed. NPs of AgCl were grown on the ZnAl-LDH surface by using AgNO3 as the silver source. The ZnAl-LDH in chloride form acts as a nucleating agent, and depending on the pH of the LDH dispersion, AgClNPs with different dimensions were obtained. In particular AgClNPs with a diameter of 60 nm were formed at pH 5. The AgClNPs supported on LDH sheets were partially reduced by different reducing agents (NaBH4 and formaldehyde) resulting in a Ag/AgCl-LDH nanocomposite. The silver chloride and silver NP dimensions were evaluated by X-ray powder diffraction, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). UV-Vis spectra of the samples upon reduction showed a band centred at 415 nm due to the surface plasmon resonance of silver nanoparticles with a diameter of about 10 nm, in agreement with the TEM analysis. The AgCl-LDH and Ag/AgCl-LDH nanocomposites, subjected to antimicrobial tests, exhibited good antimicrobial activity against both Gram-negative (Pseudomonas aeruginosa) and Gram-positive (Staphylococcus epidermidis and S. aureus) bacteria and yeast (Candida albicans). The nanocomposites were also studied for their ability to release silver by obtaining release curves, under conditions of antibacterial assays. Finally, the nanocomposites antibacterial behavior, as a function of time, was investigated by performing time-kill experiments using S. aureus and Candida albicans.

A purified capsular polysaccharide markedly inhibits inflammatory response during endotoxic shock.

Capsular material of the opportunistic fungus Cryptococcus neoformans is composed mainly of a polysaccharide named glucuronoxylomannan (GXM). In this study, the effects of GXM were analyzed in an in vivo experimental system of lipopolysaccharide (LPS)-induced shock. Endotoxic shock was induced in mice by a single intraperitoneal injection of LPS from Escherichia coli. GXM treatment reduced the mortality of mice at early stages. Mice treated with LPS alone showed markedly increased plasma levels of tumor necrosis factor alpha (TNF-α), interleukin-1ß (IL-1ß), and IL-6, whereas mice that were also treated with GXM showed significantly lower plasma levels of these cytokines. This effect was related to a marked suppression of Akt and IκBα activation. Importantly, the inhibitory effect of GXM on proinflammatory cytokine secretion was reproduced by treatment with wortmannin, an inhibitor of the Akt transcription pathway. Our results indicate that GXM has a beneficial effect on endotoxic shock, resulting in a significant increase in the rate of survival by dampening the hyperinflammatory response.

The presence of capsule in Cryptococcus neoformans influences the gene expression profile in dendritic cells during interaction with the fungus.

The aim of this investigation was to study the effect of polysaccharide capsule on the gene expression in dendritic cells (DC) during their interaction with Cryptococcus neoformans. To this end, we used an encapsulated virulent strain of C. neoformans and a cap59 gene-disrupted acapsular avirulent strain derived from the same genetic background. DC were exposed to encapsulated and acapsular C. neoformans strains for 4 h and 18 h, and their transcriptional profiles were analyzed using the Affymetrix mouse gene chip U74Av2. A large number of DC genes were up-regulated after treatment with the acapsular strain. In particular, we observed the up-regulation of the genes involved in DC maturation, such as cell surface receptors, cytokines, and chemokines (interleukin-12 [IL-12], IL-2, IL-1alpha, IL-1beta, IL-6, IL-10, tumor necrosis factor alpha, CCR7, CCL17, CCL22, CCL3, CCL4, CCL7, and CXCL10), membrane proteins, and the genes involved in antigen processing and presentation as well as cell cycle or apoptosis. The chemokine gene expression data were confirmed by real-time reverse transcription-PCR, while the expression of cytokine genes was correlated with their secretion. A completely different pattern of gene expression was observed for DC treated with an encapsulated strain of C. neoformans. In particular, no significant induction was observed in the expression of the genes mentioned above. Moreover, a number of genes, such as those coding for chemokines, were down-regulated. These results suggest that the polysaccharide capsule shrouding the cell wall of C. neoformans plays a fundamental role in inducing DC response, highlighting the molecular basis of the true nature of immune silencing exerted by capsular material.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.