Function of region I and II adhesive motifs of Plasmodium falciparum circumsporozoite protein in sporozoite motility and infectivity

The circumsporozoite protein of Plasmodium falciparum contains two conserved motifs (regions I and II) that have been proposed to interact with mosquito and vertebrate host molecules in the process of sporozoite invasion of salivary glands and hepatocytes, respectively. To study the function of this protein we have replaced the endogenous circumsporozoite protein gene of Plasmodium berghei with that of P. falciparum and with versions lacking either region I or region II. We show here that P. falciparum circumsporozoite protein functions in rodent parasite and that P. berghei sporozoites carrying the P. falciparum CS gene develop normally, are motile, invade mosquito salivary glands, and infect the vertebrate host. Region I-deficient sporozoites showed no impairment of motility or infectivity in either vector or vertebrate host. Disruption of region II abolished sporozoite motility and dramatically impaired their ability to invade mosquito salivary glands and infect the vertebrate host. These data shed new light on the role of the CS protein in sporozoite motility and infectivity.

Multicenter comparative evaluation of six commercial systems and the national committee for clinical laboratory standards m27-a broth microdilution method for fluconazole susceptibility testing of Candida species

Fluconazole susceptibility among 800 clinical Candida isolates (60% C. albicans) and two control strains (C. krusei ATCC 6258 and C. parapsilosis ATCC 22019) was tested with the NCCLS M27-A method (gold standard) and six commercial products (Candifast, disk, Etest, Fungitest, Integral System Yeasts, and Sensititre YeastOne). Results were classified as susceptible, susceptible-dose dependent, or resistant using M27-A breakpoints or, for Fungitest, Integral System Yeasts, and Candifast, as susceptible, intermediate, or resistant, according to the manufacturers' instructions. Concordance with NCCLS M27-A results was analyzed with the chi(2) test. Intra- and interlaboratory reproducibility was also evaluated. NCCLS M27-A (90.1%), Etest (93.1%), Sensititre YeastOne (93.1%), disk (96.7%), Fungitest (92.6%), Integral System Yeasts (40.6%), and Candifast (6.0%) classified the indicated percentages of C. albicans isolates as susceptible. Among non-C. albicans strains, the percentages of susceptible isolates were as follows: NCCLS M27-A, 74.0%; Etest, 83.8%; Sensititre YeastOne, 64.1%; disk, 60.6%; Fungitest, 76.6%; Integral System Yeasts, 28.3%; and Candifast, 27.4%. All methods except Candifast and Integral System Yeasts showed good agreement with NCCLS M27-A results for both C albicans and non-C. albicans isolates. Intralaboratory reproducibility was excellent for NCCLS M27-A, Etest, Sensititre YeastOne, disk, and Fungitest (88 to 91%). Similar results emerged from the interlaboratory reproducibility evaluation. Our findings indicate that some commercial methods can be useful for fluconazole susceptibility testing of clinical Candida isolates. Those characterized by a lack of medium standardization and/or objective interpretative criteria should be avoided. Particular caution is necessary when testing is being done for clinical and epidemiological purposes.

Modulation of C5aR expression on human neutrophils by encapsulated and acapsular Cryptococcus neoformans

Cryptococcus neoformans and cryptococcal surface polysaccharides influenced C5aR expression on human polymorphonuclear neutrophils (PMN). Encapsulated and acapsular strains produced dramatically different effects. Treatment of PMN with acapsular cryptococci up-regulated C5aR expression; whereas treatment with encapsulated cells suppressed C5aR expression. Glucuronoxylomannan (GXM), the principal constituent of the cryptococcal capsule, was responsible for such inhibition. Increased C5aR expression following treatment with acapsular cryptococci was accompanied by increased binding of C5a to PMN, increased superoxide production in response to stimulation with C5a, and an increased chemotactic response to C5a. Conversely, decreased C5aR expression following treatment with encapsulated cryptococci or acapsular cryptococci that had been pretreated with GXM was accompanied by decreased binding of C5a to PMN and a decreased chemotactic response to C5a. Our results raise the possibility that the down-regulation of C5aR expression by encapsulated cryptococci might alter PMN function at the site of cryptococcal infection.

Multicenter comparison of three different analytical systems for evaluation of DNA banding patterns from Cryptococcus neoformans

The enormous improvement of molecular typing techniques for epidemiological and clinical studies has not always been matched by an equivalent effort in applying optimal criteria for the analysis of both phenotypic and molecular data. In spite of the availability of a large collection of statistical and phylogenetic methods, the vast majority of commercial packages are limited by using only the unweighted pair group method with arithmetic mean algorithm to construct trees and by considering electrophoretic pattern only as migration distances. The latter method has serious drawbacks when different runs (separate gels) of the same molecular analysis are to be compared. This work presents a multicenter comparison of three different systems of banding pattern analysis on random amplified polymorphic DNA, (GACA)(4), and contour-clamped homogeneous electric field patterns from strains of Cryptococcus neoformans var. neoformans isolated in different clinical and geographical situations and a standard Saccharomyces cerevisiae strain employed as an outgroup. The systems considered were evaluated for their actual ability to(i) recognize identities, (ii) define complete differences (i.e., the ability to place S. cerevisiae out of the C. neoformans cluster), and (iii) estimate the extent of similarity among different strains. The ability to cluster strains according to the patient from which they were isolated was also evaluated. The results indicate that different algorithms do indeed produce divergent trees, both in overall topology and in clustering of individual strains, thus suggesting that care must be taken by individual investigators to use the most appropriate procedure and by the scientific community in defining a consensus system.

Regulatory role of interleukin-10 in experimental group B streptococcal arthritis

Intravenous inoculation of CD-1 mice with 10(7) CFU of type IV group B Streptococcus (GBS) results in a high incidence of diffuse septic arthritis, associated with high levels of systemic and local production of interleukin-1beta (IL-1beta) and IL-6. In this study, the role of the anti-inflammatory cytokine IL-10 in the evolution of GBS systemic infection and arthritis was evaluated. IL-10 production was evident in sera and joints of GBS-infected mice. Neutralization of endogenous IL-10 by administration of anti-IL-10 antibodies (1 mg/mouse) at the time of infection resulted in worsening of articular lesions and 60% mortality associated with early sustained production of IL-6, IL-1beta, and tumor necrosis factor alpha (TNF-alpha). The effect of IL-10 supplementation was assessed by administering IL-10 (100, 200, or 400 ng/mouse) once a day for 5 days, starting 1 h after infection. Treatment with IL-10 had a beneficial effect on GBS arthritis, and there was a clear-cut dose dependence. The decrease in pathology was associated with a significant reduction in IL-6, IL-1beta, and TNF-alpha production. Histological findings showed limited periarticular inflammation and a few-cell influx in the articular cavity of IL-10-treated mice, confirming clinical observations. In conclusion, this study provides further information concerning the role of IL-10 in regulating the immune response and inflammation and calls attention to the potential therapeutic use of IL-10 in GBS arthritis.

Anti-Candida albicans properties of novel benzoxazine analogues

We previously reported that azole 1,4-benzothiazine derivatives have appreciable anti-Candida activity. In this study, we synthesized 1,4-benzoxazine analogues and examined their possible antifungal activity to further analyze the structure-activity relationships. Results of in vitro and in vivo experiments showed that 1,4-benzoxazine analogues show appreciable antifungal activity. In particular, they have significant capability to cure mice systemically infected with a lethal challenge of Candida albicans, as indicated by increased survival time paralleling reduction of colony forming units. Moreover, 1,4-benzoxazine derivatives also showed immunomodulating activity, as indicated by a significant increase of interleukin-12 and interferon-gamma production by splenocytes and reinforcement of a T helper type 1 protective immune response to C. albicans. In conclusion, the results demonstrate that replacement of sulfur by oxygen may improve immune response against C. albicans infection.

Antibody to Cryptococcus neoformans capsular glucuronoxylomannan promotes expression of interleukin-12Rbeta2 subunit on human T cells in vitro through effects mediated by antigen-presenting cells

The results reported herein show that T cells responding to encapsulated Cryptococcus neoformans cells had reduced expression of interleukin-12 receptor beta2 (IL-12Rbeta2) in comparison to those responding to non-encapsulated cells. This suggested that encapsulation with glucuronoxylomannan (GXM), the principal constituent of the C. neoformans polysaccharide antiphagocytic capsule, inhibited expression of the IL-12Rbeta2 subunit on T cells responding to cryptococcal antigens. Addition of GXM-binding monoclonal antibody (mAb) overcame this effect by promoting IL-12Rbeta2 expression and by decreasing IL-1R expression on T cells. This effect may be a consequence of mAb-induced changes on antigen-presenting cells (APC) that are closely related to increased phagocytosis. Blocking of phagocytosis with monoiodacetic acid (MIA) precluded up-regulation of B7 expression on APC and was associated with diminished IL-12Rbeta2 expression on T cells. The observed effects on T cells were interpreted as a consequence of increased APC function due to enhanced phagocytosis. These findings suggest a mechanism by which specific antibody can promote the polarization of the cellular immune response towards a Th1-like response and thus contribute to an enhanced cellular immune response against C. neoformans.

The beneficial effect of interleukin-12 on arthritis induced by group B streptococci is mediated by interferon-gamma and interleukin-10 production

OBJECTIVE

To assess the effect of interleukin-12 (IL-12) 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 IL-12 was administered intraperitoneally 18 hours or 5 days after infection with 1 x 10(7) GBS, at doses ranging from 0.5 to 2.5 microg per mouse. 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, histopathologic changes in the joints, and cytokine production.

RESULTS

IL-12 administration before the onset of clinical signs had a beneficial effect on GBS-induced arthritis and was clearly dose-dependent. The 2.5-microg dose per mouse totally prevented death from GBS-induced arthritis. The decrease in pathology was associated with a reduction of the bacterial burden and a change in the cytokine profile. In particular, systemic and joint levels of interferon-gamma (IFN gamma) and IL-10 significantly increased in mice treated with IL-12, whereas a decrease in IL-6 and IL-1 beta production was observed. The beneficial effects of IL-12, in terms of the incidence and severity of articular lesions, were reversed by coadministration of anti-IFN gamma or anti-IL-10-neutralizing antibodies.

CONCLUSION

The findings of this study demonstrate that IL-12 is important in controlling the cytokine production that leads to the evolution of GBS-induced experimental arthritis. The amelioration of articular lesions is mostly attributable to IL-12-induced IFN gamma, but with a relevant participation of IL-12-induced IL-10.

Differential microbial clearance and immunoresponse of Balb/c (Nramp1 susceptible) and DBA2 (Nramp1 resistant) mice intracerebrally infected with Mycobacterium bovis BCG (BCG)

In mice, the gene encoding Nramp1 (natural resistance-associated protein 1) exists in two allelic forms, differing for a point mutation. According to Nramp1 genotype, extensive literature documents a clear-cut distinction of inbred strains in two non-overlapping groups that phenotypically express resistance (Nramp1r) and susceptibility (Nramp1s) to systemic infections. Here, we provide evidence that Nramp1r (DBA/2) and Nramp1s (Balb/c) mice differently handle intracerebral infection with Mycobacterium bovis BCG. Distinct trends of microbial clearance from the brain and also different patterns of local immune responses occur, thus arguing on the involvement of Nramp1 gene product on the accomplishment of cerebral anti-mycobacterial defenses.

Antigen Microarrays for Serodiagnosis of Infectious Diseases

Background: Progress in robotic printing technology has allowed the development of high-density nucleic acid and protein arrays that have increased the throughput of a variety of assays. We generated protein microarrays by printing microbial antigens to simultaneously determine in human sera antibodies directed against Toxoplasma gondii, rubella virus, cytomegalovirus (CMV), and herpes simplex virus (HSV) types 1 and 2 (ToRCH antigens).

Methods: The antigens were printed on activated glass slides with high-speed robotics. The slides were incubated first with serum samples and subsequently with fluorescently labeled secondary antibodies. Human IgG and IgM bound to the printed antigens were detected by confocal scanning microscopy and quantified with internal calibration curves. Both microarrays and commercial ELISAs were utilized to detect serum antibodies against the ToRCH antigens in a panel of characterized human sera.

Results: The detection limit (mean + 2 SD) of the microarray assay was 0.5 pg of IgG or IgM bound to the slides. Within-slide, between-slide, and between-batch precision profiles showed CVs of 1.7–18% for all antigens. Overall, >80% concordance was obtained between microarray assays and ELISAs in the classification of sera; for T. gondii, CMV, and HSV1, concordance exceeded 90%.

Conclusions: The microarray is a suitable assay format for the serodiagnosis of infectious diseases and can be easily optimized for clinical use. The ToRCH assay performs equivalently to ELISA and may have potentially important advantages in throughput, convenience, and cost.

Antigen microarrays for serodiagnosis of infectious diseases

BACKGROUND

Progress in robotic printing technology has allowed the development of high-density nucleic acid and protein arrays that have increased the throughput of a variety of assays. We generated protein microarrays by printing microbial antigens to simultaneously determine in human sera antibodies directed against Toxoplasma gondii, rubella virus, cytomegalovirus (CMV), and herpes simplex virus (HSV) types 1 and 2 (ToRCH antigens).

METHODS

The antigens were printed on activated glass slides with high-speed robotics. The slides were incubated first with serum samples and subsequently with fluorescently labeled secondary antibodies. Human IgG and IgM bound to the printed antigens were detected by confocal scanning microscopy and quantified with internal calibration curves. Both microarrays and commercial ELISAs were utilized to detect serum antibodies against the ToRCH antigens in a panel of characterized human sera.

RESULTS

The detection limit (mean + 2 SD) of the microarray assay was 0.5 pg of IgG or IgM bound to the slides. Within-slide, between-slide, and between-batch precision profiles showed CVs of 1.7-18% for all antigens. Overall, >80% concordance was obtained between microarray assays and ELISAs in the classification of sera; for T. gondii, CMV, and HSV1, concordance exceeded 90%.

CONCLUSIONS

The microarray is a suitable assay format for the serodiagnosis of infectious diseases and can be easily optimized for clinical use. The ToRCH assay performs equivalently to ELISA and may have potentially important advantages in throughput, convenience, and cost.

Rapid methods to extract DNA and RNA from Cryptococcus neoformans

Extraction of nucleic acids from the pathogenic yeast Cryptococcus neoformans is normally hampered by a thick and resistant capsule, accounting for at least 70% of the whole cellular volume. This paper presents procedures based on mechanical cell breakage to extract DNA and RNA from C. neoformans and other capsulated species. The proposed system for DNA extraction involves capsule relaxation by means of a short urea treatment and bead beating. These two steps allow a consistent extraction even from strains resistant to other procedures. Yield and quality of DNA obtained with the proposed method were higher than those obtained with two earlier described methods. This protocol can be extended to every yeast species and particularly to those difficult to handle for the presence of a capsule. RNA purification is accomplished using an original lysing matrix and the FastPrep System (Bio101) after a preliminary bead beating treatment. Yields range around 1 mg RNA from 15 ml overnight culture (10(9) cells), RNA appears undegraded, making it suitable for molecular manipulations.

Microbial growth and air pollution in carbonate rock weathering. Preliminary results of a in situ experimental study

Preliminary results on limestone weathering caused by air pollution and microbial colonization are presented in this study. Outdoor exposure experimental assays were performed on Scaglia limestone samples. Samples were exposed in two areas in Perugia (Italy) that differ for degree of urban air pollution. At different times of exposure, ranging from 1 to 12 months, microbial contamination and textural modifications of sampled surfaces were evaluated by microbiological procedures, X-ray diffraction, and scanning electron microscopy. After one year of exposure a significant fungal colonization and the presence of weathering products (i.e. gypsum) were detected on sampled surfaces.

The handing over of foundlings in the early XIX century: an unpublished study on the medical and social problems of newborn babies abandoned in the hospital of Città di Castello

The problems of illegitimate births in the early XIX century. The newborn babies were abandoned at the "Rota" of the hospital. The handing over of the newborn babies to the Rota avoided their being left with unknown persons, who, attracted by infant cries from a bundle in front of a Church or Convent, might be unreliable though compassionate. The hospital was the safest place for the babies as it provided immediate care but only after their souls had been given priority. First baptism and then medical care. For concealment the parents' names were not revealed. The baby was handed over by friends or well-wishers, a midwife or a neighbour that took interest in the baby receiving the required attention.

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.

Impaired antifungal effector activity but not inflammatory cell recruitment in interleukin-6-deficient mice with invasive pulmonary aspergillosis

A murine model of infection, in which immunocompetent or immunosuppressed interleukin-6-deficient (IL-6(-/-)) mice were infected intranasally with Aspergillus fumigatus conidia and were monitored for parameters of fungal colonization and innate and adaptive immunity, was used to assess the role of IL-6 in invasive pulmonary aspergillosis (IPA). The results indicate that IL-6(-/-) mice were more susceptible than wild-type mice to IPA. Susceptibility was associated with increased inflammatory pathology, decreased antifungal effector functions of phagocytes, and impaired development of protective type 1 responses. Exposure to exogenous IL-6 restored antifungal effector activity.

Evidence of microevolution in a clinical case of recurrent Cryptococcus neoformans meningoencephalitis

The aim of this study was to examine three serial isolates of Cryptococcus neoformans from a patient with AIDS for genotypical and phenotypical characteristics. The isolates were obtained during a first episode of cryptococcosis (simultaneous sampling of blood and cerebrospinal fluid) and after a relapse 3 years later (sampling of cerebrospinal fluid). Pulsed-field gel electrophoresis and random amplification of polymorphic DNA revealed that the blood isolate 1525 (first episode) was different from the two cerebrospinal fluid isolates (1526, first episode; 1782, relapse), yet the cerebrospinal fluid isolates were indistinguishable from each other regardless of the analysis performed. Phenotypical studies showed that isolate 1782 had significantly improved resistance to phagocytosis and killing by monocytes and polymorphonuclear cells and an altered efficacy in evoking cytokine response (augmentation of tumour necrosis factor-alpha, interleukin [IL]-1beta, IL-10, and interferon-gamma, decrease of IL-12). Interestingly, capsule size and antifungal drug resistance remained unchanged, while production of phospholipase and protease was consistently enhanced in the 1782 isolate with respect to the 1525 and 1526 isolates. In conclusion, in serial Cryptococcus neoformans isolates from a patient with AIDS, phenotypical changes but not molecular changes were documented, thus supporting the role of microevolution as a pathogenetic mechanism(s) for persistence/reactivation of fungal organisms.

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.

Defective antifungal T-helper 1 (TH1) immunity in a murine model of allogeneic T-cell-depleted bone marrow transplantation and its restoration by treatment with TH2 cytokine antagonists

Patients undergoing full haplotype-mismatched hematopoietic transplantations may experience severe intractable invasive fungal infections. To verify whether an imbalanced production of T-helper 1 (TH1) and TH2 cytokines may be responsible for susceptibility to fungal infections, C3H/HeJ (H-2(k)) recipient mice were lethally irradiated, received transplantations with T-cell-depleted allogeneic bone marrow (BM) cells from mice of H-2(d) haplotype, and were infected with Candida albicans. At different time-points after transplantation, mice were assessed for pattern of TH cytokine production and susceptibility to infection. The results show that a long-term, donor-type chimerism was achieved as early as 2 weeks after BM transplantation (BMT), at the time when high-level production of TH2 cytokines (interleukin-4 [IL-4] and IL-10) and impaired production of TH1 cytokines (interferon-gamma [IFN-gamma] and IL-12] were observed. At this time, mice were highly susceptible to both disseminated and mucosal infections, as indicated by decreased survival, uncontrolled fungal growth, and failure to develop protective TH1 immunity. However, a predominant production of TH1 cytokines was observed by week 5 after BMT, at the time when mice developed donor-type protective TH1 responses and were resistant to infections. Therapeutic ablation of IL-4 or IL-10 greatly increased resistance to candidiasis. These results indicate that a dysregulated production of TH cytokines occurs in mice undergoing T-cell-depleted allogeneic BMT. The transient predominant production of TH2 cytokines over that of IL-12 impaired the ability of mice to develop antifungal TH1 resistance, an activity that could be efficiently restored upon treatment with TH2 cytokine antagonists.

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.

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.

S100B expression in and effects on microglia

We evaluated the intracellular and extracellular biological role of S100B protein with respect to microglia. S100B, which belongs to the multigenic family of Ca2+-binding proteins, is abundant in astrocytes where it is found diffusely in the cytoplasm and is associated with membranes and cytoskeleton constituents. S100B protein is also secreted by astrocytes and acts on these cells to stimulate nitric oxide secretion in an autocrine manner. However, little is known about the relationship between S100B and microglia. To address this issue, we used primary microglia from newborn rat cortex and the BV-2 microglial cell line, a well-established cell model for the study of microglial properties. S100B expression was assessed by immunofluorescence in primary microglia and by RT-PCR, Western blotting, and immunofluorescence in BV-2 cells. S100B was found in microglia in the form of a filamentous network as well as diffusely in the cytoplasm and associated with intracellular membranes. S100B relocated around phagosomes during BV-2 phagocytosis of opsonized Cryptococcus neoformans. Furthermore, interferon-gamma (IFN-gamma) treatment caused cell shape changes and redistribution of S100B, and downregulation of S100B mRNA expression in BV-2 cells. Treatment of BV-2 cells with nanomolar to micromolar amounts of S100B resulted in increased IFN-gamma-induced expression of inducible nitric oxide synthase mRNA as well as nitric oxide secretion. Taken together, these data suggest a possible role for S100B in the accomplishment/regulation of microglial cell functions.

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.