A TH1-TH2-like switch in candidiasis: new perspectives for therapy

Response of Symptomatic Persistent Chronic Disseminated Candidiasis to Corticosteroid Therapy in Immunosuppressed Pediatric Patients: Case Study and Review of the Literature

BACKGROUND

Chronic disseminated candidiasis (CDC) is a severe invasive fungal infection principally observed during neutrophil recovery in patients with acute leukemia treated with intensive chemotherapy. Its pathophysiology remains unclear. We describe the management of 6 children with symptomatic CDC who did not respond to antifungal therapy.

METHODS

The databases of the hematology-oncology departments of 2 tertiary pediatric medical centers were searched for all patients diagnosed with CDC from 2003 to 2015, who responded to corticosteroids after failing antifungal therapy. Clinical, laboratory and radiologic data were collected.

RESULTS

Six patients (3 women, 3 men; 9-18 years of age) met the study criteria. Underlying diseases were acute lymphoblastic leukemia (n = 3) and large B-cell lymphoma, acute myeloid leukemia and severe aplastic anemia (n = 1 each). Presenting symptoms/signs of CDC were fever in all cases, with abdominal or chest pain, and/or mucositis. Candida infection was identified in blood cultures in 4 patients and in bronchoalveolar lavage fluid in one. In the absence of response to antifungal agents (4-50 days from CDC diagnosis), prednisone 2 mg/kg/day or equivalent was administered. CDC-attributable clinical symptoms resolved in 4 patients within 6-19 days; one patient required an additional nonsteroidal anti-inflammatory agent. Abnormalities on imaging decreased or disappeared within 5 months to 2 years in 4 patients.

CONCLUSIONS

In children with persistent symptomatic CDC, despite adequate antifungal therapy, administration of corticosteroids may yield rapid resolution of symptoms and decreased inflammatory markers. In patients who do not respond to steroids, the addition of a nonsteroidal anti-inflammatory drug should be considered.

Immunomodulatory efficacy of ethanol extract of propolis on tumor-bearing mice with disseminated candidiasis

OBJECTIVE

This study was aimed at investigating the effect of propolis on immunosurveillance by measuring the levels of serum interleukin (IL)-4, IL-10, IL-17, tumor necrosis factor (TNF)-α and interferon (IFN)-γ in tumor-bearing mice with disseminated candidiasis.

METHODS

The ethanol extract of propolis was selected for this study. Balb/C female mice were infected with Candida albicans (C. albicans) and inoculated with spontaneous mouse mammary tumor (SMMT). The serum levels of tissue inhibitor of metalloproteinase-1(TIMP-1) were assessed by enzyme- linked immunosorbent assay (ELISA). Mice were treated daily with propolis solution (100mg/kg, 0.1 mL, orally) for 3 days before IV challenge with C. albicans and SC challenge with SMMT and continued for 10 days. The rates of survival and tumor growth of understudy mice were investigated as well. The levels of TNF-α, IFN-γ, IL-4, IL-10 and IL-17 cytokines in culture supernatants were determined by ELISA.

RESULTS

The mean tumor size was significantly increased in tumor-bearing mice infected with C. albicans (16.98 ± 0.49 mm(2)) as compared to other mice groups (P<0.05). The results showed a significant decline of IL-4 and IL-10 levels after propolis administration to tumor-bearing mice infected with C. albicans (53.41 pg/mL, 156.81 pg/mL and 63.45 pg/mL) (P < 0.05). The increment of TNF-α (433.85 pg/mL) and IFN-γ (120.43 pg/mL) levels were also observed.

CONCLUSION

Data revealed that propolis has remarkable immunomodulatory effect, which provides a scientific validation for the popular use of this natural substance, and further investigation will help to understand propolis usefulness during immunosuppressive conditions.

Hybrid phage displaying SLAQVKYTSASSI induces protection against Candida albicans challenge in BALB/c mice

The polymorphic fungus Candida albicans (C. albicans) can live as an aggressive pathogen and cause many diseases in hosts, for which no effective vaccine exists. The secreted aspartyl proteinase 2 (Sap2) plays a protective role in systemically infected BALB/c mice. Protective cellular immune responses can be preferentially induced when antigens are displayed on small particles. Therefore, the emphasis is placed on developing new phage vaccine to inhibit C. albicans infection. In this study, the ability of the hybrid phage displaying the epitope SLAQVKYTSASSI and recombinant protein of Sap2 (rSap2) for inducing immune protective responses against C. albicans infection was evaluated by lymphoproliferative assay, to gather cytokine and antibody measurements in BALB/c mice. Our results showed that, strong cellular and humoral immune responses were induced in a mouse model immunized with hybrid phage or rSap2. Furthermore, the protection against lethal challenge with C. albicans was observed in mice vaccinated hybrid phage without adjuvant. These findings demonstrate that the hybrid phage displaying the epitope SLAQVKYTSASSI might be a potential vaccine against C. albicans infections.

Antagonistic effect of Candida albicans and IFNγ on E-cadherin expression and production by human primary gingival epithelial cells

Caused mainly by Candida albicans, oropharyngeal candidiasis is the most common oral complication associated with HIV disease worldwide. Host defenses against C. albicans essentially fall into two categories: specific immune mechanisms and local oral mucosal epithelial cell defenses. Since oral mucosa is the first line of defense in the form of a physical barrier against C. albicans invasion, and since epithelial cells are involved in anti-Candida innate immunity through different cytokines, we wanted to determine whether C. albicans alters E-cadherin expression and production, and whether interferon-γ (INFγ), a TH1 cytokine, is involved in the anti-Candida defense. Using primary human gingival epithelial cells, we demonstrated that C. albicans significantly decreased E-cadherin mRNA expression and protein production. This effect was basically obtained at later infective periods (24 and 48h). Interestingly, when IFNγ was added to C. albicans infected epithelial cell cultures, it prevented the side effect of C. albicans on E-cadherin mRNA expression and protein production and deposition. All together, these results suggested concomitant interactions between oral epithelial cells and IFNγ against C. albicans infection.

It only takes one to do many jobs: Amphotericin B as antifungal and immunomodulatory drug

“Amphotericin B acts through pore formation at the cell membrane after binding to ergosterol” is an accepted dogma about the action mechanism of this antifungal, and this sentence is widely found in the literature. But after 60 years of investigation, the action mechanism of Amphotericin B is not fully elucidated. Amphotericin B is a polyene substance that is one of the most effective drugs for the treatment of fungal and parasite infections. As stated above, the first mechanism of action described was pore formation after binding to the ergosterol present in the membrane. But it has also been demonstrated that AmB induces oxidative damage in the cells. Moreover, amphotericin B modulates the immune system, and this activity has been related to the protective effect of the molecule, but also to its toxicity in the host. This review tries to provide a general overview of the main aspects of this molecule, and highlight the multiple effects that this molecule has on both the fungal and host cells.

Cytokine gene polymorphisms and the outcome of invasive candidiasis: a prospective cohort study

BACKGROUND

 Candida bloodstream infections cause significant morbidity and mortality among hospitalized patients. Although clinical and microbiological factors affecting prognosis have been identified, the impact of genetic variation in the innate immune responses mediated by cytokines on outcomes of infection remains to be studied.

METHODS

 A cohort of 338 candidemia patients and 351 noninfected controls were genotyped for single-nucleotide polymorphisms (SNPs) in 6 cytokine genes (IFNG, IL10, IL12B, IL18, IL1β, IL8) and 1 cytokine receptor gene (IL12RB1). The association of SNPs with both candidemia susceptibility and outcome were assessed. Concentrations of pro- and antiinflammatory cytokines were measured in in vitro peripheral blood mononuclear cell stimulation assays and in serum from infected patients.

RESULTS

 None of the cytokine SNPs studied were associated with susceptibility to candidemia. Persistent fungemia occurred in 13% of cases. In the multivariable model, persistent candidemia was significantly associated with (odds ratio [95% confidence interval]): total parenteral nutrition (2.79 [1.26-6.17]), dialysis dependence (3.76 [1.46-8.64]), and the SNPs IL10 rs1800896 (3.45 [1.33-8.93]) and IL12B rs41292470 (5.36 [1.51-19.0]). In vitro production capacity of interleukin-10 and interferon-γ was influenced by these polymorphisms, and significantly lower proinflammatory cytokine concentrations were measured in serum from patients with persistent fungemia.

CONCLUSIONS

 Polymorphisms in IL10 and IL12B that result in low production of proinflammatory cytokines are associated with persistent fungemia in candidemia patients. This provides insights for future targeted management strategies for patients with Candida bloodstream infections.

Antimicrobial decapeptide KSL-W attenuates Candida albicans virulence by modulating its effects on Toll-like receptor, human β-defensin, and cytokine expression by engineered human oral mucosa

We investigated the toxicity of synthetic antimicrobial decapeptide KSL-W on normal human gingival epithelial cell cultures, its effect on Candida albicans adhesion and growth, and the activation of epithelial cell innate immunity. Our results indicate that KSL-W had no toxic effect on cell adhesion or growth, suggesting its safe use with human cells. Pre-treating C. albicans with KSL-W attenuated the yeast's virulence as demonstrated by its reduced adhesion and growth on engineered human oral mucosa epithelium and the subsequent decreased expression of some innate defense molecules by targeted epithelial cells. Indeed, the expression of Toll-like receptors and human β-defensins was reduced in tissues infected with KSL-W-treated Candida. Proinflammatory cytokine secretion (IL-1β and IL-6) by the epithelial cells was also regulated by KSL-W in a manner similar to that of antifungal molecule amphotericin B. These findings therefore show that KSL-W is safe for use with human cells and is able to attenuate Candida virulence by modulating its effects on host innate immunity. This study proposes the potential application of KSL-W peptide as an alternative antifungal agent.

In vitro efficacy of nisin Z against Candida albicans adhesion and transition following contact with normal human gingival cells

AIM

To investigate the nisin Z innocuity using normal human gingival fibroblast and epithelial cell cultures, and its synergistic effect with these gingival cells against Candida albicans adhesion and transition from blastospore to hyphal form.

METHODS AND RESULTS

Cells were cultured to 80% confluence and infected with C. albicans in the absence or presence of various concentrations of nisin Z. Our results indicate that only high concentrations of nisin Z promoted gingival cell detachment and differentiation. Determination of the LD(50) showed that the fibroblasts were able to tolerate up to 80 microg ml(-1) for 24 h, dropping thereafter to 62 mug ml(-1) after 72 h of contact, compared to 160 microg ml(-1) after 24 h, and 80 microg ml(-1) after 72 h recorded by the gingival epithelial cells which displayed a greater resistance to nisin Z. The use of nisin Z even at low concentration (25 microg ml(-1)) at appropriate concentrations with gingival cells significantly reduced C. albicans adhesion to gingival monolayer cultures and inhibited the yeast's transition.

CONCLUSION

These findings show that when used at non-toxic levels for human cells, nisin Z can be effective against C. albicans adhesion and transition and may synergistically interact with gingival cells for an efficient resistance against C. albicans.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study suggests the potential usefulness of nisin Z as an antifungal agent, when used in an appropriate range.

Cell mediated immunity to fungi: a reassessment

Protective immunity against fungal pathogens is achieved by the integration of two distinct arms of the immune system, the innate and adaptive responses. Innate and adaptive immune responses are intimately linked and controlled by sets of molecules and receptors that act to generate the most effective form of immunity for protection against fungal pathogens. The decision of how to respond will still be primarily determined by interactions between pathogens and cells of the innate immune system, but the actions of T cells will feed back into this dynamic equilibrium to regulate the balance between tolerogenic and inflammatory responses. In the last two decades, the immunopathogenesis of fungal infections and fungal diseases was explained primarily in terms of Th1/Th2 balance. Although Th1 responses driven by the IL-12/IFN-gamma axis are central to protection against fungi, other cytokines and T cell-dependent pathways have come of age. The newly described Th17 developmental pathway may play an inflammatory role previously attributed to uncontrolled Th1 responses and serves to accommodate the seemingly paradoxical association of chronic inflammatory responses with fungal persistence in the face of an ongoing inflammation. Regulatory T cells in their capacity to inhibit aspects of innate and adaptive antifungal immunity have become an integral component of immune resistance to fungi, and provide the host with immune defense mechanisms adequate for protection, without necessarily eliminating fungal pathogens which would impair immune memory--or causing an unacceptable level of tissue damage. The enzyme indoleamine 2,3-dioxygenase and tryptophan metabolites contribute to immune homeostasis by inducing Tregs and taming overzealous or heightened inflammatory responses.

Fonsecaea pedrosoi infection induces differential modulation of costimulatory molecules and cytokines in monocytes from patients with severe and mild forms of chromoblastomycosis

The host defense mechanism in chromoblastomycosis has not been thoroughly investigated. It has been suggested that cell-mediated immunity in patients with long-standing chromoblastomycosis is somehow impaired. As a result, these individuals became unable to develop an efficient immune reaction. Many studies have shown that monocyte-derived macrophages exhibit critical activities in immunity to microorganisms. Moreover, the ability of cells from the monocytic lineage to process and present antigens, to produce cytokines, and to provide costimulatory signals confirms their pivotal role in the initiation of specific immune responses. In the present study, it was observed that monocytes from patients with a severe form of disease had a higher production of IL-10 and a lower expression of HLA-DR and costimulatory molecules when stimulated with specific antigen or LPS. Immune modulation with recombinant IL-12 or anti-IL-10 can restore the antigen-specific Th1-type immune response in chromoblastomycosis patients by up-regulating HLA-DR and costimulatory molecules in monocytes. Therefore, our data show that monocytes from patients with different clinical forms of chromoblastomycosis present distinct phenotypic and functional profiles. This observation suggests possible mechanisms that control the T cell response and influence their role in the development of pathology.

beta-Glucan of Candida albicans cell wall causes the subversion of human monocyte differentiation into dendritic cells

The functional consequences of treating human monocytes with purified and chemically characterized Candida albicans beta-glucan -- a major microbial pathogen associated molecular pattern -- on their differentiation into dendritic cells (DC) were investigated. We show here that beta-glucan-treated monocytes differentiated into mature DC (Glu-MoDC) with altered phenotype and functional behavior, similarly to DC derived from C. albicans germ-tubes-infected monocytes (Gt-MoDC). They failed to express CD1a and to up-regulate CD80 and DR molecules. Moreover, they produced IL-10 but not IL-12 and primed naive T cells without inducing their functional polarization into effector cells. Since C. albicans beta-glucan is a mixture of both beta-(1,3) and beta-(1,6) glucan, we investigated their relative contribution by the use of non-Candida beta-glucan structural analogs. We found that high molecular weight (MW) glucans beta-(1,6) pustulan and beta-(1,3) curdlan totally mimicked the effect of C. albicans beta-glucan, while the low MW beta-(1,3) glucan laminarin did not have any effect. Because beta-glucan is a common constituent of all fungi and is abundantly released in vivo during systemic fungal infection, this novel effect of beta-glucan has potential implications for host-parasite relationship in candidiasis and other mycoses. In particular, our data suggest that beta-glucan could bias noninfected, bystander monocytes, thus aggravating the general immunodeficiency, predisposing to systemic fungal infection.

Immunoregulatory activity by daucosterol, a β-sitosterol glycoside, induces protective Th1 immune response against disseminated Candidiasis in mice

In the present study, we investigated immunomodulatory effect of daucosterol, a beta-sitosterol glycoside, against disseminated candidiasis caused by Candida albicans. Results showed that direct interaction of daucosterol with C. albicans yeast cells resulted in no growth-inhibition by in vitro susceptibility analysis. In contrast, mice given daucosterol (DS) intraperitoneally before intravenous challenge with live C. albicans yeast cells survived longer than DS-untreated control mice against disseminated candidiasis (P<0.05). By assessment of the fungal CFU in kidneys, DS-treated mice before the challenge developed about 81% fewer kidney CFU than untreated controls. This protection was removable by pretreatment of mice with anti-CD4+ antibody before the DS-treatment and challenge with the yeast. However, the protection was transferable by the CD4+ T cells from DS-treated mice not infected with the yeast. ELISA analysis revealed there were predominant production of IFNgamma and IL-2 cytokines as compared to IL-4, and IL-10 productions in DS-treated mice. By treatment of DS-given mice with anti-mouse IFNgamma, the protection was also abolished. Our studies show that DS protects mice against disseminated candidiasis by the CD4+ Th1 immune response.

Cellular immune response of patients with chromoblastomycosis undergoing antifungal therapy

One of the most characteristic features of the chromoblastomycosis is its unresponsiveness to treatment. In order to analyzed whether during therapy could be observed a change of cellular immune response pattern, we evaluated the production of IL-10, TNF-alpha and IFN-gamma, as well as proliferation of peripheral blood mononuclear cell (PBMC) from patients in different periods of chemotherapy treatment. Our results showed that after 6 months of treatment cells from patients proliferated to fungal antigens and produced a significant level of IFN-gamma. However, after 1 year of treatment a low proliferation of T cells and production of IFN-gamma accompanied by an increase of IL-10 were observed when compared with 6 months of treatment.

Ginsenoside Rg1 helps mice resist to disseminated candidiasis by Th1 type differentiation of CD4+ T cell

Ginsenosides, the most important component isolated from Panax ginseng, exhibits a variety of biological activities. Particularly, ginsenoside Rg1 is known to have various immune-modulating activities such as increase of immune activity of T helper (Th) cells. In this present work, we investigated the effect of the Rg1 on Candida albicans growth. Results showed that direct interaction of the Rg1 to C. albicans yeast cells resulted in no growth inhibition as tested by agar diffusion susceptibility method. Reversely, mice given the Rg1 intraperitoneally (i.p.) before intravenous (i.v.) challenge with live C. albicans yeast cells protected the mice to experimental disseminated candidiasis. By kidney candidal CFU (colony forming unit) determination, the disease severity of the Rg1-treated mice was confirmed far less than Rg1-untreated control mice. The protection was transferable by CD4+ T cells (RGCD4T) isolated from Rg1-treated mice. ELISA analysis revealed that there were cytokine inductions of IFNgamma, IL-2, IL-4 and IL-10 from the RGCD4T, demonstrating the Th1-lineage development of predominant IFNgamma and IL-2 production. Anti-mouse IFNgamma antibody treatment of Rg1-treated mice abolished the protection to disseminated disease. Our studies show that ginsenoside Rg1 helps the host resists disseminated candidiasis by the CD4(+) T cell-mediated immune response led from a Th1-dominant cytokine response.

Control, immunoregulation, and expression of innate pulmonary host defenses against Aspergillus fumigatus

The innate host defense system (IHDS) against Aspergillus fumigatus includes dedicated phagocytic cells (peripheral blood monocytes, monocyte derived macrophages, pulmonary alveolar macrophages, neutrophils, myeloid dendritic cells and natural killer cells), cytokines, chemokines, toll-like receptors, and antimicrobial peptides. During the past decade, the advances in the field of the IHDS have been enormous, allowing a better understanding of the immunopharmacological control, immunoregulation, and expression of innate host defense molecules against Aspergillus fumigatus.

Prophylactic vaccination with phage-displayed epitope of C. albicans elicits protective immune responses against systemic candidiasis in C57BL/6 mice

Epitope LKVIRK on 47 kDa of heat shock protein (Hsp) 90 of Candida albicans, corresponding to residues 386-391 of the Hsp90, is recognized by patients recovering from invasive candidiasis. The efficacy of hybrid phage displaying epitope LKVIRK in the N-terminal region of the major coat protein (pVIII) in inducing anti-invasive candidiasis immune response was studied in C57BL/6 mice. Indirect phage-ELISA results demonstrated that the mice immunized with hybrid phage had significantly higher titers of epitope LKVIRK-specific serum IgG as compared to those immunized with heat-killed C. albicans (HK-CA). C57BL/6 mice immunized either with hybrid phage or with wild-type phage also developed significant levels of delayed-type hypersensitivity (DTH) response and splenocyte proliferation, as well as with HK-CA. In addition, high levels of IFN-gamma in the CD4(+) splenocytes from phage-immunized mice were detected as well during 1 week post-inoculation. Furthermore, mice immunized with hybrid phage acquired a resistance to systemic C. albicans infection as confirmed by fewer C. albicans cells in the kidneys, and had a longer lifespan compared to control groups following intravenous challenge with C. albicans. These results indicate that hybrid phage displaying epitope LKVIRK may serve as a potential vaccine conferring a resistance to systemic candidiasis.

Prospects for dendritic cell vaccination against fungal infections in hematopoietic transplantation

Dendritic cells (DCs) are uniquely able to initiate and control the immune response to fungi. DCs function at three levels in the manipulation of the immune response to these pathogens. First, they mount an immediate or innate response to them, for example, by producing inflammatory mediators upon capture and phagocytosis; second, through these preceding innate functions, they decode the fungus-associated information and translate it in qualitatively different Th responses, and third, they are key in containing and dampening inflammatory responses by tolerization through the induction of regulatory T cells (Treg). DCs sense fungi in a morphotype-specific manner, through the engagement of distinct recognition receptors ultimately affecting cytokine production and costimulation. Both myeloid and plasmacytoid murine and human DCs phagocytose fungi and undergo functional maturation in response to them. However, their activation program for cytokine production was different, being IL-12 mainly produced by myeloid DCs and IL-12, IL-10 and IFN-alpha mainly produced by plasmacytoid DCs. This resulted in a distinct ability for T cell priming, being Th1, Th2, and Treg differently activated by the different DC subsets. The ability of fungus-pulsed DCs to prime for Th1 and Th2 cell activation upon adoptive transfer in vivo correlated with the occurrence of resistance and susceptibility to the infections, respectively. Antifungal protective immunity was also induced upon adoptive transfer of DCs transfected with fungal RNA. The efficacy was restricted to DCs transfected with RNA from yeasts or conidia but not with RNA from fungal hyphae. The effect was fungus-specific, as no cross-protection was observed upon adoptive transfer of DCs pulsed with either fungal species. The infusion of fungus-pulsed or RNA-transfected DCs accelerated the recovery of functional antifungal Th1 responses in mice with allogeneic hematopoietic stem cell transplantation (HSCT) and affected the outcome of the infections. As the ability of phagocytose fungi was defective in peripheral DCs from patients with HSCT, soon after the transplant, our findings suggest that the adoptive transfer of DCs may restore immunocompetence in HSCT by contributing to the educational program of T cells. Thus, the remarkable functional plasticity of DCs in response to fungi can be exploited for the deliberate targeting of cells and pathways of cell-mediated immunity in response to fungal vaccines.

Cytokines and lymphocyte proliferation in patients with different clinical forms of chromoblastomycosis

Chromoblastomycosis is a chronic, often debilitating, suppurative, granulomatus mycosis of the skin and subcutaneous tissues beginning after inoculation trauma. It occurs world-wide, but is more frequently observed in tropical countries such as Brazil. The disease is usually insidious, and the lesions increase slowly but progressively, not responding to the usual treatments and quite often reappearing. The host defense mechanism in chromoblastomycosis has not been extensively investigated. Some studies have focused on fungus-host interaction, showing a predominantly cellular immune response, with the activation of macrophages involved in fungus phagocytosis. Although phagocytosis did occur, death of fungal cells was rarely observed. The ability of Fonsecaea pedrosoi to produce secreted or cell wall-associated melanin-like components, protects against destruction by host immune cells in vitro. Until now, the T cell immune response in chromoblastomycosis is undefined. In the present work, it was shown that, in patients with the severe form of the disease, predominant production of IL-10 cytokine, low levels of IFN-gamma and inefficient T cell proliferation were induced. In contrast, in patients with a mild form of the disease, predominant production of IFN-gamma cytokine, low levels of IL-10 and efficient T cell proliferation were observed.

A Crucial Role for Tryptophan Catabolism at the Host/Candida albicansInterface

By mediating tryptophan catabolism, the enzyme indoleamine 2,3-dioxygenase (IDO) has a complex role in immunoregulation in infection, pregnancy, autoimmunity, transplantation, and neoplasia. We hypothesized that IDO might affect the outcome of the infection in mice infected with Candida albicans by virtue of its potent regulatory effects on inflammatory and T cell responses. IDO expression was examined in mice challenged with the fungus along with the consequences of its blockade by in vivo treatment with an enzyme inhibitor. We found that IDO activity was induced at sites of infection as well as in dendritic cells and effector neutrophils via IFN-gamma- and CTLA-4-dependent mechanisms. IDO inhibition greatly exacerbated infection and associated inflammatory pathology as a result of deregulated innate and adaptive/regulatory immune responses. However, a role for tryptophan catabolism was also demonstrated in a fungus-autonomous fashion; its blockade in vitro promoted yeast-to-hyphal transition. These results provide novel mechanistic insights into complex events that, occurring at the fungus/pathogen interface, relate to the dynamics of host adaptation to the fungus. The production of IFN-gamma may be squarely placed at this interface, where IDO activation probably exerts a fine control over fungal morphology as well as inflammatory and adaptive antifungal responses.

Toll-like receptor 2 is dispensable for acquired host immune resistance to Candida albicans in a murine model of disseminated candidiasis

Previous work by our group showed that Toll-like receptor 2 (TLR2) is essential for activation of innate immunity, playing a major role in the response of macrophages to Candida albicans, triggering cytokine and chemokine expression, and therefore TLR2 -/- mice are more susceptible to systemic primary candidiasis. In this work, we used a murine model of systemic C. albicans infection, in which resistance to reinfection with virulent wild-type cells is induced by prior exposure of mice to a low-virulence agerminative strain of C. albicans (primary sublethal infection), to study the influence of TLR2 gene deletion on (i) the ability to develop an acquired resistance upon vaccination; (ii) the development of the acquired humoral response; and (iii) the production of Th1 cytokines IFN-gamma, IL-12 and TNF-alpha. Our results indicate that, although TLR2 -/- mice have a very impaired production of Th1 cytokines compared with control mice, they are equally capable of mounting a specific humoral response to the fungus and developing a vaccine-induced resistance.

Common polymorphisms in critical genes of innate immunity do not contribute to the risk for chronic disseminated candidiasis in adult leukemia patients

Chronic disseminated candidiasis is a serious fungal infection in immunocompromised patients, particularly those undergoing therapy for acute leukemia. Coordination between innate and adaptive immune system is critical to resistance or susceptibility to Candida infection. In order to investigate possible genetic contribution to chronic disseminated candidiasis of key molecules in the innate immune pathway, we performed a case control study using the candidate gene approach. Forty subjects with chronic disseminated candidiasis and 50 controls without chronic disseminated candidiasis but an underlying diagnosis of leukemia were enrolled in the Helsinki University Central Hospital during the period 1980-1998. Candidate genes were selected for analysis based upon the following criteria: a common polymorphism (>5% frequency) and existence a priori of clinical and biological data suggesting a role for the variant in the pathogenesis of chronic disseminated candidiasis. Six genes were selected from critical microbicidal and innate immune pathways, including three low-affinity Fcgamma receptors (FCGR2A, FCGR3A and FCGR3B), chitotriosidase (CHIT1), p22-phox NADPH oxidase (CYBA), and mannose binding lectin (MBL2). There was no statistically significant association of susceptibility to chronic disseminated candidiasis with the polymorphisms in this study. Common variants in the six studied genes most likely do not contribute to the risk for chronic disseminated candidiasis in patients with acute leukemia.

The safety of interferon-?-1b therapy for invasive fungal infections after hematopoietic stem cell transplantation

BACKGROUND

The restoration of normal immune responses, especially of the T-helper type 1 immune response, is an important predictor of fungal infection outcome in patients with malignant disease who undergo hematopoietic stem cell transplantation (HSCT). The authors sought to evaluate the safety of adjuvant recombinant interferon-gamma-1b as an immune-modulatory therapy HSCT recipients.

METHODS

Thirty-two patients received interferon-gamma-1b after undergoing HSCT at the author's institution between 1998 and 2003. A retrospective analysis was undertaken after obtaining permission from the Institutional Review Board.

RESULTS

Twenty-six of 32 patients (81%) received allogeneic stem cell grafts. All but 1 patient received interferon-gamma-1b and antifungals to treat infections; the other patients received interferon-gamma-1b to promote autologous graft-versus-tumor effect. Interferon-gamma-1b usually was administered at a dose of 50 mug subcutaneously every other day. The median duration (+/- standard deviation) of interferon-gamma-1b therapy was 6+/-6.5 doses (range, 1-29 doses), and the median cumulative dose was 487+/-453 mug (range, 35-2175 microg). During therapy with interferon-gamma-1b, fever was common (n=9 patients; 28%). In 1 patient (3%), new-onset lymphocytopenia occurred but resolved after cytokine therapy was discontinued; there were no interferon- gamma-1b-related episodes of neutropenia, thrombocytopenia, anemia, or liver dysfunction. Interferon-gamma-1b therapy did not precipitate or exacerbate acute or chronic graft-versus-host disease (GVHD). In fact, in 2 of 7 patients (29%) with acute GVHD and in 3 of 10 patients (30%) with chronic GVHD, significant improvements in GVHD were noted during therapy with interferon-gamma-1b. Among the 26 patients with aspergillosis, 14 patients (54%) died. However, 5 of 10 patients (50%) with presumed pulmonary aspergillosis, 3 of 9 patients (33%) with probable pulmonary aspergillosis, 1 of 2 patients (50%) with definite pulmonary aspergillosis, and 3 of 5 patients (60%) with disseminated aspergillosis responded to antifungals and adjuvant interferon-gamma-1b.

CONCLUSIONS

Recombinant interferon-gamma-1b was tolerated without serious adverse reactions in HSCT recipients. A large, prospective, randomized study will be needed to evaluate the efficacy of this cytokine in high-risk HSCT recipients who have invasive mycoses.

Candida albicans and Streptococcus salivarius modulate IL-6, IL-8, and TNF-alpha expression and secretion by engineered human oral mucosa cells

We investigated the involvement of oral epithelial cells via two cytokines (IL-6 and TNF-alpha) and one chemokine (IL-8) in local defences against live yeast (Candida albicans) and bacteria (Streptococcus salivarius) using an engineered human oral mucosa model. We report that the yeast changed from the blastospore to the hyphal form and induced significant tissue disorganization at later contact periods (24 and 48 h) compared to the bacteria. However, this effect did not reduce the viability or total number of epithelial cells. Gene activation analyses revealed that IL-6, IL-8 and TNF-alpha mRNA levels rose in tissues in contact with live C. albicans or S. salivarius. Gene activation was followed by an upregulation of protein secretion. IL-6 levels were higher after contact with C. albicans than with S. salivarius. IL-8 levels after contact with S. salivarius were higher than with C. albicans. Our study suggests that S. salivarius is more efficient at inducing proinflammatory mediator release than C. albicans. These results provide additional evidence for the contribution of oral epithelial cells to the inflammatory response against fungi and bacteria.

CD28 induces immunostimulatory signals in dendritic cells via CD80 and CD86

Bidirectional signaling along the B7-CTLA-4 coreceptor pathway enables reciprocal conditioning of T cells and dendritic cells. Although T cells can instruct dendritic cells to manifest tolerogenic properties after CTLA-4 engagement of B7, such a B7-mediated signaling is not known to occur in response to CD28. Here we show that mouse dendritic cells were induced by soluble CD28 to express interleukin 6 and interferon-gamma. Production of interleukin 6 required B7-1 (CD80), B7-2 (CD86) and p38 mitogen-activated protein kinase and prevented interferon-gamma-driven expression of immunosuppressive tryptophan catabolism. In vivo, an adjuvant activity of soluble CD28 was demonstrated as enhanced T cell-mediated immunity to tumor and self peptides and protection against microbial and tumor challenge. Thus, different ligands of B7 can signal dendritic cells to express functionally distinct effector responses.

Dendritic cell-based vaccination against opportunistic fungi

Efficient responses to the different forms of fungi require different mechanisms of immunity. Dendritic cells (DCs) are uniquely able to decode the fungus-associated information and translate it in qualitatively different T helper (Th) immune responses, in vitro and in vivo. DCs sense fungi in a morphotype-specific manner, through the engagement of distinct recognition receptors ultimately affecting cytokine production and costimulation. Adoptive transfer of different types of DCs activates protective and non-protective Th cells as well as regulatory T cells and affects the outcome of the infections. DCs transfected with fungal RNA also restore antifungal resistance in hematopoietic transplantation. Thus, the remarkable functional plasticity of DCs in response to fungi can be exploited for the deliberate targeting of cells and pathways of cell-mediated immunity in response to fungal vaccines.

Reconstitution dynamics of plasmacytoid and myeloid dendritic cell precursors after allogeneic myeloablative hematopoietic stem cell transplantation

Dendritic cells (DCs) are fundamental for immunity. We investigated reconstitution of plasmacytoid DC (PDC) and myeloid DC (My-DC) precursors in the first 2 months after allogeneic hematopoietic stem cell transplantation (Allo-HSCT). Circulating DCs were monitored from the earliest phase of hematopoietic reconstitution in 43 children given standard therapy to prevent graft-versus-host disease (GVHD) and either treated or untreated with granulocyte colony-stimulating factor (G-CSF) after HSCT. In patients without GVHD, both My-DCs and PDCs reached consistently high absolute values during the initial phase. Time of engraftment did not differ between My-DCs and PDCs, regardless of administration of G-CSF. Treatment with G-CSF (1) accelerated early recovery of My-DC absolute numbers; (2) was associated with lower numbers of both My-DCs and PDCs in the later phase; and (3) significantly reduced the proportion of interleukin-12 (IL-12)-secreting cells. In some patients who developed acute GVHD, we found high numbers of circulating DC precursors during the early phase of this complication. However, treatment with steroids invariably induced rapid decrease of PDCs. Altogether, these data provide an evaluation of DC release after Allo-HSCT, indicate that postgrafting administration of G-CSF impairs the appearance of IL-12-producing DCs, and suggest that DC homeostasis may be disrupted at onset of GVHD.

In vitro analyses of tissue structure and interleukin-1β expression and production by human oral mucosa in response to Candida albicans infections

Clinical and experimental observations suggest that oral epithelial cells play a key role in host defenses against candidal infections through cytokines and chemokines. We thus attempted to determine whether oral epithelial cells convey IL-1beta as a pro-inflammatory cytokine in response to Candida albicans infections. We created engineered human oral mucosa (EHOM), put them in contact with live and heat-inactivated C. albicans (10(5) yeast/cm2), and measured the expression of IL-1beta mRNA and protein. Tissue structure and C. albicans morphology were also evaluated. Only live C. albicans modulated IL-1beta expression and secretion. IL-1beta mRNA expression significantly increased during the early stages of infection and decreased during the later stages. The modulatory effect of C. albicans on IL-1beta expression was confirmed by the fact that increased amounts of inactive IL-1beta (33 kDa) were detected early during the infection which then dropped dramatically. There was a significant and time-dependent increase in the amount of the active form of IL-1beta (17 kDa) secreted into the supernatant by epithelial cells infected with live C. albicans. Histological features revealed damage to infected tissues (separation of epithelial cells, edema, vacuolization, reduction in thickness) compared to uninfected ones. Morphological analyses showed that C. albicans changed from a blastospore to a hyphal form at later infection periods. This transformation was very pronounced at 8 and 24 h post-infection. These results provide additional evidence for the contribution of oral epithelial cells to local defenses against exogenous stimulations such as C. albicans infections.

Immunity to fungal infections

The topic of immunity to fungal infections is of interest to a wide range of disciplines, from microbiology to immunology. It is of particular interest in terms of therapy of HIV-infected individuals, and patients with cancer or individuals who have received transplants. Understanding the nature and function of the immune response to fungi is an exciting challenge that might set the stage for new approaches to the treatment of fungal diseases, from immunotherapy to vaccines. The past decade has witnessed the development of a wide range of new approaches to elucidate events that occur at the host-fungus interface.

Dendritic cells and fungi

Fungi comprise a group of microorganisms that in the past 20 years has become increasingly important as a cause of human disease. Few fungi are professional but instead opportunistic pathogens, and some fungi can even act as allergens. Dendritic antigen-presenting cells function as a link between innate and adaptive immunity and are therefore important in recognition of pathogens. Effective defense requires the host to discriminate between different pathogens to induce an appropriate response. Signaling from different groups of microbes can be mediated via the Toll-like receptors (TLRs), leading to activation of conserved host defense signaling pathways that control the expression of a variety of immune response genes. Different dendritic cells (DCs) express different patterns of recognition molecules, which indicate that they are more or less efficient when responding to certain pathogens. DCs have an important role in the induction of cell-mediated immune responses to fungi, and the studies reviewed here show that fungi, or possibly fungi-derived factors, provide a powerful activation stimulus to DCs, resulting in DC maturation with upregulation of co-stimulatory molecules and production of cytokine patterns leading to different T cell responses. The possibility of using ex vivo-generated DCs as therapeutic tools for restoring anti-fungal immunity is a challenge for the future.

NK cells mediate increase of phagocytic activity but not of proinflammatory cytokine (interleukin-6 [IL-6], tumor necrosis factor alpha, and IL-12) production elicited in splenic macrophages by tilorone treatment of mice during acute systemic candidiasis

The participation of NK cells in the activation of splenic macrophages or in resistance to systemic candidiasis is still a matter of debate. We had previously reported that there is a correlation between natural killer cell activation and resistance to systemic candidiasis. In those experiments we had used tilorone to boost NK cell activity in mice. Here we show a mechanism elicited by tilorone in splenic macrophages which could explain their effect on mouse survival during acute disseminated Candida albicans infection. The results demonstrate that tilorone treatment elicits, by a direct effect, the production of proinflammatory cytokines (interleukin-6 [IL-6], tumor necrosis factor alpha [TNF-alpha], and IL-12) by splenic macrophages. In addition, it increases the capacity of splenic macrophages to phagocytize C. albicans through activation of NK cells. We also demonstrate that the presence of NK cells is essential for maintaining a basal level of phagocytic activity, which characterizes splenic macrophages of naïve control mice. The results demonstrate that it is possible to identify two phenotypically and functionally peculiar cell populations among splenic macrophages: (i). cells of the "stimulator/secretor phenotype," which show high levels of major histocompatibility complex (MHC) class II surface expression, are poorly phagocytic, and synthesize the proinflammatory cytokines IL-6, TNF-alpha, and IL-12, and (ii). cells of the "phagocytic phenotype," which express low levels of MHC class II molecules, are highly phagocytic, and do not secrete proinflammatory cytokines.

Salivary cytokine profiles in the immunocompetent individual with Candida-associated denture stomatitis

Cell-mediated immunity conferred by CD4+ T helper cells is considered the predominant host defense against mucosal Candida infections, with Thelper (Th1)-type responses associated with resistance to infection and Th2-type responses associated with susceptibility to infection. Oropharyngeal candidiasis, the most common oral opportunistic infection in HIV-infected persons, is associated with a Th2-type cytokine profile in saliva. To obtain more direct evidence for a role of salivary cytokines in susceptibility to oropharyngeal candidiasis during immunosuppression, we evaluated Th1/Th2-type cytokines in the saliva of those with denture stomatitis, a form of oropharyngeal candidiasis not related to immunosuppression. Results showed that HIV-negative denture wearers with and without denture stomatitis demonstrated a mixed Th1/Th2 cytokine profile with no significant differences found between the groups. These results suggest that a local Th cytokine dichotomy in saliva is not associated with susceptibility to denture stomatitis in immunocompetent persons.

Cytokines in immunodeficient patients with invasive fungal infections: an emerging therapy

Immune response is the major contributor to host defense against opportunistic fungal infections such as candidiasis, aspergillosis and other rare infections. A number of cytokines have been developed and studied in vitro for activity against fungal pathogens. The most studied among them in relation to fungal infections are granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF) and interferon-gamma (IFN-gamma). The fields where these cytokines have been predominantly studied or where they may need more study are primary immunodeficiencies of the phagocytic cells, neonatal age, human immunodeficiency virus infection and cancer-related conditions such as neutropenia and hemopoietic cell transplantation. In this review, the in vitro, experimental animal and clinical data of cytokines are summarized in relation to invasive candidiasis, aspergillosis and emerging fungal infections. Cytokine administration to patients together with antifungal agents, as well as transfusion of cytokine-upgraded phagocytes, are promising immunotherapeutic modalities for further research.

Candida albicans infection enhances immunosuppression induced by cyclophosphamide by selective priming of suppressive myeloid progenitors for NO production

Systemic infections caused by fungi after cytoreductive therapies are especially difficult to deal with in spite of currently available antimicrobials. However, little is known about the effects of fungi on the immune system of immunosuppressed hosts. We have addressed this by studying the in vitro T cell responses after systemic infection with Candida albicans in cyclophosphamide-treated mice. After cyclophosphamide treatment, a massive splenic colonization of the spleens, but not lymph nodes, by immature myeloid progenitor (Ly-6G(+)CD11b(+))cells is observed. These cells are able to suppress proliferation of T lymphocytes via a nitric oxide (NO)-dependent mechanism. Systemic infection with a sublethal dose of C. albicans did not cause immunosuppression per se but strongly increased NO-dependent suppression in cyclophosphamide-treated mice, by selective priming of suppressive myeloid progenitors (Ly-6G(+)CD11b(+)CD31(+)CD40(+)WGA(+)CD117(low/-)CD34(low/-)) for iNOS protein expression. The results indicate that systemic C. albicans infection can augment the effects of immunosuppressive therapies by promoting functional changes in immunosuppressive cells.

Inhibitory effects of whole and parotid saliva on immunomodulators

Based on the presence of cytokines in whole saliva and their association with resistance and susceptibility to infectious disease, the present study was designed to evaluate the diagnostic potential of a large panel of cytokines and chemokines in saliva. Despite the endogenous presence of Th1/Th2 and pro-inflammatory cytokines and several chemokines in whole and parotid saliva of most individuals tested, the detection of known concentrations of several recombinant cytokines and chemokines was inhibited immediately following their addition to each type of saliva. In contrast, purified immunoglobulins were unaffected by either whole or parotid saliva. Further studies revealed that the inhibition of immunoreactivity involved sequestration of the majority of cytokines affected and degradation of chemokines. These results suggest that absolute concentrations of cytokines/chemokines may not be fully detectable in saliva. Therefore, the diagnostic value of any cytokine/chemokine is questionable and should be evaluated independently as such.

Dendritic cells pulsed with fungal RNA induce protective immunity to Candida albicans in hematopoietic transplantation

Immature myeloid dendritic cells (DC) phagocytose yeasts and hyphae of the fungus Candida albicans and induce different Th cell responses to the fungus. Ingestion of yeasts activates DC for production of IL-12 and Th1 priming, while ingestion of hyphae induces IL-4 production and Th2 priming. In vivo, generation of antifungal protective immunity is induced upon injection of DC ex vivo pulsed with Candida yeasts but not hyphae. In the present study we sought to determine the functional activity of DC transfected with yeast or hyphal RNA. It was found that DC, from either spleens or bone marrow, transfected with yeast, but not hyphal, RNA 1) express fungal mannoproteins on their surface; 2) undergo functional maturation, as revealed by the up-regulated expression of MHC class II Ags and costimulatory molecules; 3) produce IL-12 but no IL-4; 4) are capable of inducing Th1-dependent antifungal resistance when delivered s.c. in vivo in nontransplanted mice; and 5) provide protection against the fungus in allogeneic bone marrow-transplanted mice, by accelerating the functional recovery of Candida-specific IFN-gamma-producing CD4(+) donor lymphocytes. These results indicate the efficacy of DC pulsed with Candida yeasts or yeast RNA as fungal vaccines and point to the potential use of RNA-transfected DC as anti-infective vaccines in conditions that negate the use of attenuated microorganisms or in the case of poor availability of protective Ags.

Downregulation of IFN-gamma production in patients with recurrent vaginal candidiasis

BACKGROUND

Recurrent vaginal candidiasis (RVC) is an important health problem with unknown pathogenesis. Although impairment of the T-cell response is associated with persistent or recurrent candidiasis, data on immunologic responses in patients with RVC are controversial.

OBJECTIVES

To evaluate the T-cell response in patients with RVC and the ability of cytokines and cytokine antagonists to modulate IFN-gamma production in cultures stimulated with Candida albicans antigens.

METHODS

Participants in the study included 13 patients with RVC and 7 control women with sporadic candidiasis. Cytokines were determined by ELISA in supernatants of mononuclear cells with C albicans, purified protein derivative, or tetanus toxoid antigen.

RESULTS

IFN-gamma production was absent or low in 11 of 13 women (84.6%) with RVC. Absent or low IFN-gamma production was specific to C albicans antigens (189 +/- 389 pg/mL), because high IFN-gamma levels were found in cultures stimulated with purified protein derivative (739 +/- 774 pg/mL) or tetanus toxoid antigens (1085 +/- 546 pg/mL). Monoclonal antibody anti-IL-10 enhanced IFN-gamma levels (750 +/- 753 pg/mL), and IL-10 suppressed this cytokine production in patients with sporadic candidiasis.

CONCLUSIONS

Mononuclear cells from patients with RVC stimulated with C albicans antigen have low or absent IFN-gamma production. IL-10 plays an important role in downregulation of the T-cell response in these patients.

Invasive candidiasis stimulates hepatocyte and monocyte production of active transforming growth factor beta

Candida albicans is an opportunistic fungal pathogen and a major cause of morbidity and mortality in patients with compromised immune function. The cytokine response to tissue invasion by C. albicans can influence the differentiation and function of lymphocytes and other mononuclear cells that are critical components of the host response. While the production of transforming growth factor beta (TGF-beta) has been documented in mice infected with C. albicans and is known to suppress phagocyte function, the cellular source and role of this cytokine in the pathogenesis of systemic candidiasis are not well understood. We have investigated the source of production of TGF-beta by immunohistochemical studies in tissue samples from patients with an uncommon complication of lymphoreticular malignancy, chronic disseminated candidiasis (CDC), and from a neutropenic-rabbit model of CDC. Liver biopsy specimens from patients with documented CDC demonstrated intense staining for extracellular matrix-associated TGF-beta1 within inflammatory granulomas, as well as staining for TGF-beta1 and TGF-beta3 within adjacent hepatocytes. These results correlate with the immunolocalization of TGF-beta observed in livers of infected neutropenic rabbits, using a neutralizing antibody that recognizes the mature TGF-beta protein. Human peripheral blood monocytes incubated with C. albicans in vitro release large amounts of biologically active TGF-beta1. The data demonstrate that local production of active TGF-betas by hepatocytes and by infected mononuclear cells is a component of the response to C. albicans infection that most probably contributes to disease progression in the immunocompromised host.

Host immune reactivity and antifungal chemotherapy: the power of being together

Fungal infections, particularly those in immunocompromised hosts, have been a major therapeutic challenge over recent decades. The difficulty in diagnosing invasive infections, together with the emergence of unusual opportunistic pathogens and a pathogen shift in the spectrum of the causative organisms, have greatly hampered the effectiveness of antifungal therapy. Knowledge of the immunoregulation of fungal infections may provide new insights for therapeutic interventions. The appreciation of the importance of T helper cells and cytokines in the overall coordination of the effector immune response to fungi has offered novel opportunities to manipulate these processes and to alter the outcome of fungal infections while improving the therapeutic efficacy of antifungal drugs. Cytokine and cytokine antagonists, alone or in combination with antifungals, have the potential to overcome the specific defects of host immune reactivity predisposing to fungal infections. The current challenge lies in translating much of the information obtained in experimental and preclinical studies into therapeutic strategies providing prospects for the ultimate treatment of fungal infections.

Comparison of pathogenesis and host immune responses to Candida glabrata and Candida albicans in systemically infected immunocompetent mice

Cytokine-mediated host defense against Candida glabrata infection was compared to that against C. albicans, using immunocompetent murine models of systemic candidiasis. The pathogenesis of infection was evaluated morphologically and by culture of target organs, while the kinetics of induction of cytokine mRNAs and corresponding proteins were determined in kidneys by real-time reverse transcription-PCR and cytokine-specific murine enzyme-linked immunosorbent assays, respectively. Systemic infection with C. glabrata resulted in a chronic, nonfatal infection with recovery of organisms from kidneys, while intravenous inoculation with C. albicans resulted in rapid mortality with logarithmic growth of organisms in kidneys and recovery of C. albicans from the spleen, liver, and lungs. Survival of C. glabrata-infected mice was associated with rapid induction of mRNAs and corresponding immunoreactive proteins for the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha), interleukin-12 (IL-12), and gamma interferon (IFN-gamma) and the lack of induction of protein for the anti-inflammatory cytokine IL-10. In contrast, mortality in C. albicans-infected mice was associated with induction of mRNA and corresponding protein for IL-10 but delayed (i.e., TNF-alpha) or absent (i.e., IL-12 and IFN-gamma) induction of immunoreactive proinflammatory cytokines. Mice were subsequently treated with cytokine-specific neutralizing monoclonal antibodies (MAbs) to TNF-alpha, IL-12, or IFN-gamma, and the effect on growth of C. glabrata in kidneys was assessed. Neutralization of endogenous TNF-alpha resulted in a significant increase in C. glabrata organisms compared to similarly infected mice administered an isotype-matched control MAb, while neutralization of endogenous IL-12 or IFN-gamma had no significant effect on C. glabrata replication. These results demonstrate that in response to intravenous inoculation of C. glabrata, immunocompetent mice develop chronic nonfatal renal infections which are associated with rapid induction of the proinflammatory cytokines TNF-alpha, IL-12, and IFN-gamma. Furthermore, TNF-alpha plays a key role in host defense against systemic candidiasis caused by either C. glabrata or C. albicans, as the absence of endogenous TNF-alpha activity was associated with enhanced tissue burden in both infection models.

Postgrafting administration of granulocyte colony-stimulating factor impairs functional immune recovery in recipients of human leukocyte antigen haplotype-mismatched hematopoietic transplants

In human leukocyte antigen haplotype-mismatched transplantation, extensive T-cell depletion prevents graft-versus-host disease (GVHD) but delays immune recovery. Granulocyte colony-stimulating factor (G-CSF) is given to donors to mobilize stem cells and to recipients to ensure engraftment. Studies have shown that G-CSF promotes T-helper (Th)-2 immune deviation which, unlike Th1 responses, does not protect against intracellular pathogens and fungi. The effect of administration of G-CSF to recipients of mismatched hematopoietic transplants with respect to transplantation outcome and functional immune recovery was investigated. In 43 patients with acute leukemia who received G-CSF after transplantation, the engraftment rate was 95%. However, the patients had a long-lasting type 2 immune reactivity, ie, Th2-inducing dendritic cells not producing interleukin 12 (IL-12) and high frequencies of IL-4- and IL-10-producing CD4(+) cells not expressing the IL-12 receptor beta(2) chain. Similar immune reactivity patterns were observed on exposure of donor cells to G-CSF. Elimination of postgrafting administration of G-CSF in a subsequent series of 36 patients with acute leukemia, while not adversely affecting engraftment rate (93%), resulted in the anticipated appearance of IL-12-producing dendritic cells (1-3 months after transplantation versus > 12 months in transplant recipients given G-CSF), of CD4(+) cells of a mixed Th0/Th1 phenotype, and of antifungal T-cell reactivity in vitro. Moreover, CD4(+) cell counts increased in significantly less time. Finally, elimination of G-CSF-mediated immune suppression did not significantly increase the incidence of GVHD (< 15%). Thus, this study found that administration of G-CSF to recipients of T-cell-depleted hematopoietic transplants was associated with abnormal antigen-presenting cell functions and T-cell reactivity. Elimination of postgrafting administration of G-CSF prevented immune dysregulation and accelerated functional immune recovery.