Differential cytokine production and Toll-like receptor signaling pathways by Candida albicans blastoconidia and hyphae

Toll-like receptors (TLR) are crucial for an efficient antifungal defense. We investigated the differential recognition of blastoconidia and hyphae of Candida albicans by TLRs. In contrast to Candida blastoconidia, which stimulated large amounts of gamma interferon (IFN-gamma), the tissue-invasive Candida hyphae did not stimulate any IFN-gamma by human peripheral blood mononuclear cells (PBMC) or murine splenic lymphocytes. After stimulation with blastoconidia, the production of IFN-gamma was TLR4 dependent, as shown by the significantly decreased IFN-gamma production in anti-TLR4-treated PBMC and in splenic lymphocytes from TLR4-defective ScCr mice. In addition, peritoneal macrophages from ScCr mice produced less tumor necrosis factor alpha (TNF-alpha) than macrophages of control mice did when stimulated with Candida blastoconidia, but not with hyphae, indicating that TLR4-mediated signals are lost during hyphal germination. In contrast, macrophages from TLR2 knockout mice had a decreased production of TNF-alpha in response to both Candida blastoconidia and hyphae. Candida hyphae stimulated production of interleukin-10 through TLR2-dependent mechanisms. In conclusion, TLR4 mediates proinflammatory cytokine induction after Candida stimulation, whereas Candida recognition by TLR2 leads mainly to anti-inflammatory cytokine release. TLR4-mediated proinflammatory signals are lost during germination of Candida blastoconidia into hyphae. Phenotypic switching during germination may be an important escape mechanism of C. albicans, resulting in counteracting host defense.     

Invasive phenotype of Candida albicans affects the host proinflammatory response to infection

Candida albicans is a major opportunistic pathogen in immunocompromised patients. Production of proinflammatory cytokines by host cells in response to C. albicans plays a critical role in the activation of immune cells and final clearance of the organism. Invasion of host cells and tissues is considered one of the virulence attributes of this organism. The purpose of this study was to investigate whether the ability of C. albicans to invade host cells and tissues affects the proinflammatory cytokine responses by epithelial and endothelial cells. In this study we used the invasion-deficient RIM101 gene knockout strain DAY25, the highly invasive strain SC5314, and highly invasive RIM101-complemented strain DAY44 to compare the proinflammatory cytokine responses by oral epithelial or endothelial cells. Using a high-throughput approach, we found both qualitative and quantitative differences in the overall inflammatory responses to C. albicans strains with different invasive potentials. Overall, the highly invasive strains triggered higher levels of proinflammatory cytokines in host cells than the invasion-deficient mutant triggered. Significant differences compared to the attenuated mutant were noted in interleukin-1alpha (IL-1alpha), IL-6, IL-8, and tumor necrosis factor alpha in epithelial cells and in IL-6, growth-related oncogene, IL-8, monocyte chemoattractant protein 1 (MCP-1), MCP-2, and granulocyte colony-stimulating factor in endothelial cells. Our results indicate that invasion of host cells and tissues by C. albicans enhances the host proinflammatory response to infection.     

Recombinant human antibody single chain variable fragments reactive with Candida albicans surface antigens.

A combinatorial phage display library expressing human immunoglobulin heavy and light chain variable regions was used to identify phage clones capable of binding to the surface of Candida albicans blastoconidia. Single chain antibody variable fragments (scFv) derived from three clones detected C. albicans antigens by indirect immunofluorescence assay (IFA), enzyme-linked immunosorbent assay (ELISA), and Western blotting. The antigens detected were conserved among different strains of C. albicans and several other Candida species. Two scFv clones detected antigens specifically expressed by C. albicans blastoconidia; the third detected antigens in both blastoconidia and filamentous forms of C. albicans. The antigens containing the epitopes recognized by all three scFv could be extracted from blastoconidia by dithiothreitol, suggesting attachment to the cell wall via sulfhydryl bonds. Epitope detection by the scFv was sensitive to treatment of C. albicans blastoconidia with sodium periodate, but not proteinase K, indicating the cognate epitopes were composed of carbohydrate. Antigenic determinants for each of the three scFv were detected by immunohistochemical staining of skin sections from a model of cutaneous candidiasis, demonstrating expression in vivo. Through selection for the ability to bind intact organisms, the phage display system provides a means to rapidly identify monoclonal binding ligands to Candida surface antigens. Being entirely human, mature antibodies generated from the scFv have potential utility in the treatment of candidiasis.     

Mechanisms of the proinflammatory response of endothelial cells to Candida albicans infection

Endothelial cells can influence significantly the host inflammatory response against blood-borne microbial pathogens. Previously, we found that endothelial cells respond to in vitro infection with Candida albicans by secreting interleukin 8 (IL-8) and expressing E-selectin, intercellular adhesion molecule 1 (ICAM-1), and vascular cell adhesion molecule 1 (VCAM-1). We have now examined the mechanisms mediating this endothelial cell response. We determined that C. albicans stimulated endothelial cells to synthesize tumor necrosis factor alpha (TNF-alpha), which in turn induced these infected cells to secrete IL-8 and express E-selectin by an autocrine mechanism. Expression of VCAM-1 was mediated not only by TNF-alpha but also by IL-1alpha and IL-1beta, all of which were synthesized by endothelial cells in response to C. albicans. These three cytokines remained primarily cell associated rather than being secreted. Candidal induction of ICAM-1 expression was independent of TNF-alpha, IL-1alpha, and IL-1beta. These observations demonstrate that different proinflammatory endothelial cell responses to C. albicans are induced by distinct mechanisms. A clear understanding of these mechanisms is important for therapeutically modulating the endothelial cell response to C. albicans and perhaps other opportunistic pathogens that disseminate hematogenously.     

Critical role for serum opsonins and complement receptors CR3 (CD11b/CD18) and CR4 (CD11c/CD18) in phagocytosis of Francisella tularensis by human dendritic cells (DC): uptake of Francisella leads to activation of immature DC and intracellular survival of the bacteria

Francisella tularensis is one of the most infectious human pathogens known. Although much has been learned about the immune response of mice using an attenuated live vaccine strain (LVS) derived from F. tularensis subspecies holarctica (Type B), little is known about the responses of human monocyte-derived immature dendritic cells (DC). Here, we show that optimal phagocytosis of LVS by DC is dependent on serum opsonization. We demonstrate that complement factor C3-derived opsonins and the major complement receptors expressed by DC, the integrins CR3 (CD11b/CD18) and CR4 (CD11c/CD18), play a critical role in this adhesion-mediated phagocytosis. LVS induced proinflammatory cytokine production and up-regulation of costimulatory surface proteins (CD40, CD86, and MHC Class II) on DC but resisted killing. Once taken up, LVS grew intracellularly, resulting in DC death. DC maturation and cytokine production were induced by direct contact/phagocytosis of LVS or interaction with soluble products of the bacteria, and enhanced activation was seen when LVS was pretreated with serum. Sonicated LVS and supernatants from LVS cultures were potent activators of DC, but LVS LPS failed to activate DC maturation or cytokine production. Serum-treated LVS rapidly induced (within 6 h) a number of cytokines including IL-10, a potent suppressor of macrophage functions and down-regulator of Th1-like responses and the Th1 response inducer IL-12. These results suggest that the simultaneous production of an activating (IL-12, IL-1beta, and TNF-alpha) and a suppressing (IL-10) cytokine profile could contribute to the immunopathogenesis of tularemia.     

Cytokine production and dermatophytosis]

The characteristic pathological feature of dermatomycosis is numerous neutrophilic infiltrates within the epidermis. However, the precise mechanism of this infiltration remains unknown. In this study, interleukins 1 beta, 6, and 8, monocyte chemotactic protein-1 (MCP-1), and tumor necrosis factor (TNF)-alpha levels in the medium where keratinocytes were co-cultured with Candida albicans, Malassezia and Trichophyton mentagrophytes, were determined by enzyme-linked immunosorbent assays (ELISAs) in order to estimate the effect of these fungi on the cytokine production from human keratinocytes. The IL-8 level in the supernatants increased with 1 to 14 hours of co-culture in response to live C. albicans, but the other cytokines were undetectable. Furthermore, the mRNA of IL- 8 in keratinocytes was also confirmed to increased. This data suggested that C. albicans directly induce interleukin 8 production from human keratinocytes without activated macrophages. The IL-6, IL-8, and TNF-alpha levels in the culture supernatants increased with 1 to 24 hours of co-culture with keratinocytes and Malassezia species but the MCP-1 level was undetectable. The IL-8 and TNF-alpha levels in the culture supernatants increased with 1 to 24 hours of co-culture with keratinocytes and Trichophyton mentagrophytes but the other cytokine levels were undetectable. The ELISA analysis of cytokine production by human keratinocytes will provide useful information in understanding the pathogenesis of dermatomycosis.     

Candida-specific Th1-type responsiveness in mice with experimental vaginal candidiasis.

The role of systemic cell-mediated immunity (CMI) as a host defense mechanism in the vagina is poorly understood. Using a murine pseudoestrus model of experimental vaginal candidiasis, we previously found that animals given a vaginal inoculum of viable Candida albicans blastoconidia acquired a persistent vaginal infection and developed Candida-specific delayed-type hypersensitivity (DTH) responses. The present study was designed to characterize the peripheral CMI reactivity generated from the vaginal infection in mice and to determine whether pseudoestrus is a prerequisite for the induction of peripheral CMI reactivity. Mice treated or not treated with estrogen and given a vaginal inoculum of C. albicans blastoconidia were examined for 4 weeks for their vaginal Candida burden and peripheral CMI reactivity, including DTH responsiveness and in vitro Th1 (interleukin-2 [IL-2], gamma interferon [IFN-gamma]/Th2 (IL-4, IL-10)-type lymphokine production in response to Candida antigens. Results showed that although mice not treated with estrogen before being given a vaginal inoculum of C. albicans blastoconidia developed only a short-lived vaginal infection and harbored significantly fewer Candida CFU in the vagina compared with those given estrogen and then infected; DTH reactivity was equivalent in both groups. In vitro measurement of CMI reactivity further showed that lymph node cells from both estrogen- and non-estrogen-treated infected mice produced elevated levels of IL-2 and IFN-gamma in response to Candida antigens during the 4 weeks after vaginal inoculation. In contrast, lymph node cells from the same vaginally infected mice showed no IL-10 production and only small elevations of IL-4 during week 4 of infection. These results suggest that mice with experimental vaginal candidiasis develop predominantly Th1-type Candida-specific peripheral CMI reactivity and that similar patterns of Th1-type reactivity occur in mice regardless of the persistence of infection and the estrogen status of the infected mice.     

Expression of extracellular acid proteinase by proteolytic Candida spp. during experimental infection of oral mucosa.

We traced an acid proteinase from Candida spp. in the initial stages of the pathogenesis of the mycosis. On infection of human buccal mucosa, proteinase antigens were detected by immuno-scanning electron microscopy on the surface of adhering blastoconidia and invading filamentous cells of C. albicans serotype A. Proteinase antigens were also present on blastoconidia of C. albicans serotype B, but were missing on filamentous cells of this serotype. Proteolytic isolates of C. tropicalis behaved like C. albicans serotype A. An isolate of C. parapsilosis did not express the proteinase antigen under conditions of this study. After infection of mucosa, culture medium of C. albicans or C. tropicalis showed a time-dependent accumulation of acid proteolytic activity, indicating that the visualized antigens represent active proteinase. No such activity was detected in the medium of C. parapsilosis. Preliminary experiments with the proteinase inhibitor pepstatin A revealed an 89% reduction of mucosal adherence of C. albicans (serotype A). These results suggest that Candida proteinase is involved in fungal attachment. The pattern of adherence reflects the differential expression of secretory proteinase by different candidal strains.     

Immunoregulation in experimental murine candidiasis: specific suppression induced by Candida albicans cell wall glycoprotein.

Immune regulation in candidiasis is inferred from studies of both human and animal infection, with a suppressive role suggested for cell wall polysaccharide. To study the immunosuppressive potential of Candida albicans in a murine model, whole blastoconidia or purified cell wall components of C. albicans were tested for their effects on the development of acquired immune responses by superimposing a pretreatment regimen upon an established immunization protocol. CBA/J or BALB/cByJ mice were pretreated twice intravenously with 100 micrograms of mannan (MAN), 100 or 200 micrograms of glycoprotein (GP), or 5 X 10(7) heat-killed C. albicans blastoconidia, followed 1 week later by an immunization protocol of two cutaneous inoculations of viable C. albicans blastoconidia given 2 weeks apart. Delayed hypersensitivity (DTH) to GP or to a membrane-derived antigen, B-HEX, was tested 7 days after the second inoculation, and lymphocyte stimulation was tested with mitogens and Candida antigens after 12 days. To assess protection, mice were challenged intravenously with viable C. albicans blastoconidia 14 days after the second cutaneous inoculation and sacrificed 28 days later for quantitative culture of kidneys and brains. Sera were obtained for enzyme-linked immunosorbent assays at selected intervals. Pretreatment with GP resulted in specific in vivo suppression of DTH to GP but not to B-HEX antigen and specific in vitro suppression of lymphocyte stimulation to GP but not to other Candida antigens or mitogens. MAN and heat-killed C. albicans blastoconidia had no such effects. GP pretreatment also diminished the protective effect of immunization against challenge, demonstrable in the brain, while not altering significantly the production of antibody in response to infection. Contrary to clinical evidence, MAN was not immunosuppressive in this model, and in fact, the immunosuppressive potential of GP, which is composed largely of MAN, was found to be dependent upon the presence of its heat-labile protein moiety.     

Differential regulation of inflammatory cytokine secretion by human dendritic cells upon Chlamydia trachomatis infection

Chlamydia trachomatis is an obligate intracellular gram-negative bacterium responsible for a wide spectrum of diseases in humans. Both genital and ocular C. trachomatis infections are associated with tissue inflammation and pathology. Dendritic cells (DC) play an important role in both innate and adaptive immune responses to microbial pathogens and are a source of inflammatory cytokines. To determine the potential contribution of DC to the inflammatory process, human DC were infected with C. trachomatis serovar E or L2. Both C. trachomatis serovars were found to infect and replicate in DC. Upon infection, DC up-regulated the expression of costimulatory (B7-1) and cell adhesion (ICAM-1) molecules. Furthermore, chlamydial infection induced the secretion of interleukin-1beta (IL-1beta), IL-6, IL-8, IL-12p70, IL-18, and tumor necrosis factor alpha (TNF-alpha). The mechanisms involved in Chlamydia-induced IL-1beta and IL-18 secretion differed from those of the other cytokines. Chlamydia-induced IL-1beta and IL-18 secretion required infection with viable bacteria and was associated with the Chlamydia-induced activation of caspase-1 in infected host cells. In contrast, TNF-alpha and IL-6 secretion did not require that the Chlamydia be viable, suggesting that there are at least two mechanisms involved in the Chlamydia-induced cytokine secretion in DC. Interestingly, an antibody to Toll-like receptor 4 inhibited Chlamydia-induced IL-1beta, IL-6, and TNF-alpha secretion. The data herein demonstrate that DC can be infected by human C. trachomatis serovars and that chlamydial components regulate the secretion of various cytokines in DC. Collectively, these data suggest that DC play a role in the inflammatory processes caused by chlamydial infections.     

Exogenous farnesol interferes with the normal progression of cytokine expression during candidiasis in a mouse model

Candida albicans, a dimorphic fungus composed of yeast and mycelial forms, is the most common human fungal pathogen. Th1 cytokines such as interleukin-2 (IL-2), gamma interferon (IFN-gamma), and tumor necrosis factor alpha (TNF-alpha), which are induced by macrophage IL-12, are critical to resistance against systemic candidiasis, while Th2 cytokines such as IL-4 and IL-5 are less critical. Farnesol is a quorum-sensing molecule produced by C. albicans that controls the formation of mycelia but is also a virulence factor. To determine whether farnesol enhances the virulence of C. albicans by modulating the production of Th1 and Th2 cytokines, mice were pretreated with farnesol prior to intravenous infection with a sublethal dose of farnesol-producing C. albicans. Production of IL-2, IL-4, IL-5, TNF-alpha, IFN-gamma, and IL-12 was evaluated by bead-array flow cytometry and enzyme-linked immunosorbent assay. Mice exhibited an elevation in serum TNF-alpha levels at 48 h and an elevation in IFN-gamma and IL-12 levels at 6 to 12 h after infection with C. albicans. Pretreatment with farnesol significantly reduced the elevation of both IFN-gamma and IL-12 but not TNF-alpha. In contrast, mice pretreated with farnesol exhibited an unexpected elevation in IL-5 levels. To determine whether farnesol has a direct effect on macrophage production of IL-12, peritoneal macrophages were pretreated with farnesol prior to stimulation with IFN-gamma plus lipopolysaccharide (LPS). Farnesol inhibited production of both IL-12 p40 and p70 from IFN-gamma/LPS-stimulated macrophages. Therefore, the role of farnesol in systemic candidiasis is likely due to its ability to inhibit the critical Th1 cytokines IFN-gamma and IL-12 and perhaps to enhance a Th2 cytokine, IL-5.     

Candida albicans triggers interleukin-8 secretion by oral epithelial cells

Oropharyngeal candidiasis is a frequent opportunistic infection associated with immunocompromised hosts. Candida albicans is the principal species responsible for this infection. Production of interleukin-8 (IL-8), by oral epithelial cells can be expected to play a major role in the recruitment and activation of professional phagocytes at the infected site. The purpose of this study was to determine whether C. albicans triggers secretion of IL-8 by oral epithelial cells in vitro and investigate mechanisms of host cell-fungal interactions that trigger such responses. Oral epithelial cell lines (SCC4, SCC15, and OKF6/TERT-2) as well as primary gingival epithelial cells were used. Epithelial cells were cocultured with C. albicans, strains SC5314, ATCC28366 or ATCC32077, for 24-48 hr, and supernatants were analyzed for IL-8 content by ELISA. A germination-deficient mutant (efg1/efg1 cph1/cph1), otherwise isogenic to strain SC5314, was used to assess the requirement for germination in triggering IL-8 responses. In order to ascertain whether direct contact of yeast with host cells is required to trigger cytokine production, epithelial cells were separated from yeast using cell culture inserts. To test whether IL-8 secretion is dependent on IL-1alpha activity, epithelial cells were challenged with viable C. albicans in the presence or absence of neutralizing anti-IL-1alpha antibody or IL-1ra, and IL-8 secretion was measured in the supernatants. All cell lines and primary cultures responded to C. albicans with an increase in IL-8 secretion. IL-8 responses were contact-dependent, strain-specific, required yeast viability and germination into hyphae, and were in part autoregulated by IL-1alpha.     

Evidence for the presence of collagenous domains in Candida albicans cell surface proteins.

Rabbit polyclonal antibodies (PAbs) directed towards the amino-terminal cysteine-rich 7S domain (PAb anti-7S), the major internal collagenous domain (PAb anti-type IV), and the C-terminal noncollagenous region (PAb anti-NC1) of the type IV collagen molecule were probed by indirect immunofluorescence against Candida albicans blastoconidia and germinated blastoconidia. Most nongerminating cells and mother blastoconidia from which germ tubes originated showed strong fluorescence when PAb anti-7S was used, whereas with PAb anti-type IV, fluorescence was found almost exclusively on the surface of filamentous forms. A patched fluorescent pattern rather than a homogenous confluent fluorescence was observed in all cases. No fluorescent cells were observed with PAb anti-NC1. By Western immunoblotting, PAb anti-type IV cross-reacted primarily with a polypeptide of 37 kDa present in wall extracts obtained from intact cells of both growth forms by treatment with beta-mercaptoethanol, whereas PAb anti-7S recognized a major 58-kDa antigen also present in both extracts, along with some other high-molecular-mass (> 106-kDa) polydisperse species present only in the material released from blastoconidia with beta-mercaptoethanol. No reactive bands were observed when PAb anti-NC1 was used as a probe in Western immunoblotting experiments. The sensitivities or resistances to collagenase digestion of the different polypeptides that cross-reacted with PAbs anti-type IV and anti-7S suggest the existence of cell wall components in C. albicans that contain epitopes that mimic the collagenous domains of the type IV collagen molecule.     

Ureaplasma urealyticum modulates endotoxin-induced cytokine release by human monocytes derived from preterm and term newborns and adults

We previously observed that Ureaplasma urealyticum respiratory tract colonization in infants with a birth weight of < or =1,250 g was associated with increases in the tracheal aspirate proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha) and interleukin-8 (IL-8) relative to the counterregulatory cytokine IL-6 during the first week of life (A. M. Patterson, V. Taciak, J. Lovchik, R. E. Fox, A. B. Campbell, and R. M. Viscardi, Pediatr. Infect. Dis. J. 17:321-328, 1998). We hypothesized that U. urealyticum alters the host immune response in the presence of a coinflammatory stimulus (e.g., bacterial infection or hyperoxia) by shifting the balance of cytokine expression towards the proinflammatory cytokines. To test this hypothesis, we compared the release of TNF-alpha, IL-8, IL-6, and IL-10 in vitro by unstimulated and U. urealyticum (with or without lipopolysaccharide [LPS])-stimulated human monocytes from adult peripheral blood and from term and preterm cord blood. U. urealyticum alone and in combination with LPS induced concentration- and development-dependent changes in cytokine release. In vitro inoculation with low-inoculum U. urealyticum (10(3) color-changing units [CCU]) (i) partially blocked the LPS-stimulated IL-6 release by all cells and reduced LPS-stimulated IL-10 release by preterm cells, (ii) stimulated TNF-alpha and IL-8 release by preterm cells, and (iii) augmented LPS-stimulated TNF-alpha release in all cells. In preterm cells, high-inoculum U. urealyticum (10(6) CCU) (i) stimulated TNF-alpha and IL-8, but not IL-6 or IL-10, release and (ii) augmented LPS-stimulated TNF-alpha and IL-8 release. High-inoculum U. urealyticum (i) stimulated release of all four cytokines in term cells and IL-8 release in adult cells and (ii) augmented LPS-induced TNF-alpha, IL-10, and IL-8 release in term cells but did not significantly affect LPS-induced cytokine release in adult cells. We speculate that U. urealyticum enhances the proinflammatory response to a second infection by blocking expression of counterregulatory cytokines (IL-6 and IL-10), predisposing the preterm infant to prolonged and dysregulated inflammation, lung injury, and impaired clearance of secondary infections.     

Rapid killing of monocytes in vitro by Candida albicans yeast cells.

To study the interaction between Candida albicans blastoconidia and human phagocytes, we incubated peripheral leukocytes with fungi for 1 h at 37 degrees C and stained the cells with fluorescent vital stains ethidium bromide (EB) and fluorescein diacetate. Fungi that had been phagocytosed showed little staining; however, some leukocytes containing blastoconidia exhibited nuclear staining with EB, even though their cell membranes showed no signs of penetration by fungi. The number of EB-positive leukocytes was related to viability of the yeast cells and the temperature at which they were maintained before use. Because efforts to quantitate EB-positive leukocytes microscopically were frustrated by cell aggregation, we labeled the leukocytes with 51Cr and measured isotope release. We determined that leukocytes incubated with viable fungi released significantly more isotope than cells incubated alone or with killed blastoconidia. Furthermore, 51Cr release correlated directly with concentration of fungi in the assay, time of incubation, and temperature at which fungi were maintained before use. Using a number of isolates of C. albicans and several other species of Candida, we found that all exhibited cytotoxic activity against leukocytes, but the level of activity varied among organisms. Finally, we depleted or enriched peripheral leukocytes for specific cell populations and determined that only monocytes released more 51Cr after incubation with viable blastoconidia. Blastoconidia can lyse phagocytic cells through germination and penetration of cell membranes within 1 to 2 h, but the cytotoxic phenomenon we describe occurs within 15 to 30 min after yeast cells have been phagocytosed. Therefore, this capacity may represent a more immediate response by blastoconidia against phagocytosis and killing by monocytes.     

Cytokine and Chemokine Production by Human Oral and Vaginal Epithelial Cells in Response to Candida albicans

Oropharyngeal and vaginal candidiases are the most common forms of mucosal fungal infections and are primarily caused by Candida albicans, a dimorphic fungal commensal organism of the gastrointestinal and lower female reproductive tracts. Clinical and experimental observations suggest that local immunity is important in host defense against candidiasis. Accordingly, cytokines and chemokines are present at the oral and vaginal mucosa during C. albicans infections. Since mucosal epithelial cells produce a variety of cytokines and chemokines in response to microorganisms and since C. albicans is closely associated with mucosal epithelial cells as a commensal, we sought to identify cytokines and/or chemokines produced by primary oral and vaginal epithelial cells and cell lines in response to C. albicans. The results showed that proinflammatory cytokines were produced by oral and/or vaginal epithelial cells at various levels constitutively with considerable interleukin-1alpha (IL-1alpha) and tumor necrosis factor alpha, but not IL-6, produced in response to C. albicans. In contrast, Th1-type (IL-12 and gamma interferon) and Th2-type-immunoregulatory (IL-10 and transforming growth factor beta) cytokines and the chemokines monocyte chemoattractant protein 1 and IL-8 were produced in low to undetectable concentrations with little additional production in response to C. albicans. Taken together, these results indicate that cytokines and chemokines are variably produced by oral and vaginal epithelial cells constitutively, as well as in response to C. albicans, and are predominated by proinflammatory cytokines.     

Lipooligosaccharide and polysaccharide capsule: virulence factors of Neisseria meningitidis that determine meningococcal interaction with human dendritic cells

In this work we analyzed the roles of meningococcal lipooligosaccharide (LOS) and capsule expression in the interaction of Neisseria meningitidis with human dendritic cells (DC). Infection of DC with serogroup B wild-type meningococci induced a strong burst of the proinflammatory cytokines and chemokines tumor necrosis factor alpha, interleukin-6 (IL-6), and IL-8. In contrast, a serogroup B mutant strain lacking LOS expression barely led to cytokine induction, demonstrating that meningococcal LOS is the main mediator of the proinflammatory response in human DC. Sialylation of meningococcal LOS did not influence cytokine secretion by DC. However, we found the phagocytosis of N. meningitidis by human DC to be inhibited by LOS sialylation. In addition, the expression of the meningococcal serogroup A, B, and C capsules dramatically reduced DC adherence of N. meningitidis and phagocytosis to some extent. Hence, LOS sialylation and capsule expression are independent mechanisms protecting N. meningitidis from the phagocytic activity of human DC.