Immune responses induced by heat killed Saccharomyces cerevisiae: a vaccine against fungal infection

Heat-killed Saccharomyces cerevisiae (HKY) used as a vaccine protects mice against systemic aspergillosis and coccidioidomycosis. Little is known about the immune response induced by HKY vaccination, consequently our goal was to do an analysis of HKY-induced immune responses involved in protection. BALB/c mice were vaccinated subcutaneously 3 times with HKY, a protective reagent, and bronchoalveolar lavage fluid, spleen, lymph nodes, and serum collected 2-5 weeks later. Cultured spleen or lymph node cells were stimulated with HKY. Proliferation of HKY-stimulated spleen or lymph node cells was tested by Alamar Blue reduction and flow cytometry. Cytokines from lymphocyte supernatants and antibody to glycans in serum collected from HKY-vaccinated mice were measured by ELISA. The results show that HKY promoted spleen cell and lymph node cell proliferation from HKY-vaccinated mice but not from PBS-vaccinated control mice (all P<0.05). Cytokine measurement showed HKY significantly promoted IFNγ, IL-6 and IL-17A production by spleen cells and lymph node cells (all P<0.05 and P<0.01, respectively). Cytokine production by HKY-stimulated cells from PBS-vaccinated mice was lower than those from HKY-vaccinated (P<0.05). Cytokines in BAL from HKY-vaccinated were higher, 1.7-fold for IFNγ and 2.1-fold for TNFα, than in BAL from PBS-vaccinated. Flow cytometry of lymphocytes from HKY-vaccinated showed 52% of CD3(+) or 56% of CD8(+) cells exhibited cell division after stimulation with HKY, compared to non-stimulated controls (26 or 23%, respectively) or HKY-stimulated cells from PBS-vaccinated (31 or 34%). HKY also induced antibody against Saccharomyces glucan and mannan with titers 4- or 2-fold, respectively, above that in unvaccinated. Taken together, the results suggested that HKY vaccination induces significant and specific Th1 type cellular immune responses and antibodies to glucan and mannan.

Production of IL-6, in contrast to other cytokines and chemokines, in macrophage innate immune responses: effect of serum and fungal (Blastomyces) challenge

Murine peritoneal macrophages, after adherence and establishment in culture in vitro in the presence of medium containing fetal bovine serum (FBS) for 20 h, then cultured for 20 h, produced several cytokines. If, in the second 20 h period, a fungus (heat-killed Blastomyces, HK-Bd) was introduced, a more complex pattern of cytokine (particularly TNF) and chemokine production ensued. The cytokine production, assayed by antibody array and also quantitation in supernatants, was depressed (particularly TNF) by the addition of mouse serum to these cultures, with the exception of IL-6. Macrophages could be cultured in the presence or absence of serum during the initial 20 h adherence and establishment period, enabling study of the effect of serum factors. In the absence of serum, with or without fungal stimulation, cytokine and chemokine production was more restricted, largely to TNF and IL-6. The addition of mouse serum [corrected] resulted in marked depression of TNF and enhancement of IL-6. The combination of HK-Bd and mouse serum resulted in more IL-6 production than either component alone. The enhancement of IL-6 by mouse serum was concentration-dependent and maximal at 8 h. The effects of fungus or serum on macrophage production of cytokines were similar in an outbred and an inbred mouse strain. The larger repertoire of cytokine production in the macrophages that had been cultured longer (20 h+20 h) in serum may be related to maturation of cell receptors. IL-6 production in vivo in response to fungal-serum complexes could affect pathogenesis by opposing the host defense modulation by proinflammatory cytokines or by modulating the destructive effects of inflammation on host tissues.

IL-12 induction of resistance to pulmonary blastomycosis

BACKGROUND

Why severity varies in blastomycosis outbreaks remains unresolved. In experimental pulmonary blastomycosis, susceptibility varied in mouse strains. In susceptible BALB/c the response is Th-2, in immunized, resistance is associated with Th-1. Can susceptibility be redirected by IL-12? Methods, results: BALB/c bronchoalveolar and peritoneal macrophages (PM) were shown deficient in IL-12 production in response to IFN-gamma+LPS. High dose IL-12 (1 microg, subcutaneously) treatment of BALB/c infected intranasally with Blastomyces resulted in enhanced survival (P<0.008). Since IL-12 was poorly tolerated, a new protocol for infected mice, IL-12 0.1 or 0.3 microg, every other day, resulted in minimal toxicity; almost all treated mice survived (P<0.002 vs. controls). When lungs of surviving mice were cultured, the 0.1 microg regimen resulted in fewer (P<0.02) cfu. For weeks after treatment, in vitro IFN-gamma treatment enabled PM Blastomyces killing. After infection spleen cells from IL-12 treated mice produced 4-fold more IFN-gamma and 3-fold less IL-10 in response to Blastomyces. IL-10 abrogated activation of macrophages by IFN-gamma for enhanced Blastomyces killing.

CONCLUSIONS

A proper IL-12 treatment protocol induces resistance (survival and decreased growth in lungs), low toxicity, macrophage responsiveness to IFN-gamma for killing Blastomyces, up-regulation of IFN-gamma and down-regulation of IL-10 production.

Effect of lung surfactant collectins on bronchoalveolar macrophage interaction with Blastomyces dermatitidis: inhibition of tumor necrosis factor alpha production by surfactant protein D

Alveolar surfactant modulates the antimicrobial function of bronchoalveolar macrophages (BAM). Little is known about the effect of surfactant-associated proteins in bronchoalveolar lavage fluid (BALF) on the interaction of BAM and Blastomyces dermatitidis. We investigated BALF enhancement or inhibition of TNF-alpha production by BAM stimulated by B. dermatitidis. BAM from CD-1 mice were stimulated with B. dermatitidis without or with normal BALF, surfactant protein A-deficient (SP-A-/-) or surfactant protein D-deficient (SP-D-/-) BALF, or a mixture of SP-A-/- and SP-D-/- BALF. An enzyme-linked immunosorbent assay was used to measure tumor necrosis factor alpha (TNF-alpha) in culture supernatants. BALFs were standardized in protein concentration. BAM plus B. dermatitidis (BAM-B. dermatitidis) TNF-alpha production was inhibited > or = 47% by BALF or SP-A-/- BALF (at 290 or 580 microg of protein/ml, P < 0.05 to 0.01); in contrast, SP-D-/- BALF did not significantly inhibit TNF-alpha production. If SP-A-/- BALF was mixed in equal amounts with SP-D-/- BALF, TNF-alpha production by BAM-B. dermatitidis was inhibited (P < 0.01). Finally, pure SP-D added to SP-D-/- BALF inhibited TNF-alpha production by BAM-B. dermatitidis (P < 0.01). B. dermatitidis incubated with BALF and washed, plus BAM, stimulated 63% less production of TNF-alpha than did unwashed B. dermatitidis (P < 0.05). SP-D was detected by anti-SP-D antibody on BALF-treated unwashed B. dermatitidis in an immunofluorescence assay (IFA). The BALF depleted by a coating of B. dermatitidis lost the ability to inhibit TNF-alpha production (P < 0.05). 1,3-beta-Glucan was a good stimulator of BAM for TNF-alpha production and was detected on B. dermatitidis by IFA. beta-Glucan incubated with BALF inhibited the binding of SP-D in BALF to B. dermatitidis as demonstrated by IFA. Our data suggest that SP-D in BALF binds beta-glucan on B. dermatitidis, blocking BAM access to beta-glucan, thereby inhibiting TNF-alpha production. Thus, whereas BALF constituents commonly mediate antimicrobial activity, B. dermatitidis may utilize BALF constituents, such as SP-D, to blunt the host defensive reaction; this effect could reduce inflammation and tissue destruction but could also promote disease.

Inhibitor kappaB and nuclear factor kappaB in granulocyte-macrophage colony-stimulating factor antagonism of dexamethasone suppression of the macrophage response to Aspergillus fumigatus conidia

BACKGROUND

The dexamethasone (DEX) immunosuppressive effect on macrophage killing activity and cytokine production in response to Aspergillus fumigatus conidia is antagonized by granulocyte-macrophage colony-stimulating factor (GM-CSF). The molecular mechanism is unknown. We postulated that this antagonism is mediated by inhibitor kappaB (I kappaB) induction by DEX and is opposed by acceleration of I kappaB degradation by GM-CSF with or without conidia stimulation, with corresponding effects on translocation and activation of nuclear factor kappa B (NF-kappaB).

METHODS

We studied 2 types of cells, resident peritoneal macrophages from CD-1 mice and the murine macrophage RAW264.7 cell line. Cells were unstimulated or stimulated with conidia and simultaneously treated with DEX, GM-CSF, or DEX plus GM-CSF, for 2-4 hours. I kappaB degradation and NF-kappaB activation were assessed by Western blot.

RESULTS

Macrophages stimulated with conidia alone increased NF-kappaB translocation. DEX increased I kappaB levels in cytoplasm and blocked translocation of NF-kappaB to the nucleus in unstimulated and conidia-stimulated macrophages. Conversely, GM-CSF decreased I kappaB levels. GM-CSF reversed the effect of DEX on I kappaB levels. NF-kappaB levels were minimal in DEX-treated macrophage nuclear extracts, compared with those from GM-CSF-treated and GM-CSF plus DEX-treated macrophages.

CONCLUSION

GM-CSF can reverse the DEX immunosuppressive effect by enhancing I kappaB degradation and promoting NF-kappaB translocation. This would allow macrophage production of proinflammatory cytokines, facilitating resistance to aspergillosis.

Susceptibility to pulmonary blastomycosis in young compared to adult mice: immune deficiencies in young mice

The immunological basis for differences in resistance to pulmonary blastomycosis between young (3 to 4-week-old) and adult (7 to 8-week-old) CD-1 mice is unknown. We assessed whether there were differences in fungicidal activity of phagocytes and Th-1 lymphocyte cytokine production. The fungicidal activity of young bronchoalveolar macrophages (BAM) (20%) against Blastomyces dermatitidis (Bd) was comparable to killing by adult BAM (25%). However, IFN-gamma enhanced the killing by adult BAM (from 30 to 69%) to a greater extent than BAM from young animals (from 20 to 30%). Killing of Bd by young peritoneal macrophages (PM) (46%) and adult PM (42%) was similar, and the enhancement of cells of both by IFN-gamma was similar. TNFalpha production by young macrophages (BAM or PM), when cocultured with Bd for 18 h, was half of TNFalpha secreted by adult macrophages. We found that polymorphonuclear neutrophils (PMN) from young mice had deficient fungicidal activity against Bd (37%) compared with adult PMN (80%). Interferon-gamma (IFN-gamma) treatment increased PMN killing of Bd by PMN of young animals from 37 to 80%. In an assessment of innate responses, we found spleen cells from young mice produced three-fold less IFN-gamma and three-fold less IL-2 than adult spleen cells in response to 1 microg/ml concanavalin A (Con A). The young spleen cells also produced more NO, which we demonstrated reduced Con A-induced proliferation. These in vitro results demonstrate several immunological deficiencies in cells from young mice and these deficiencies correlate with susceptibility. In a pilot reconstitution experiment in pulmonary blastomycosis, treatment of infected young mice with IFN-gamma (18.5 x 10(3) U, s.c.) on days 0, 1, and 2 significantly increased survival.

Immunological basis for susceptibility and resistance to pulmonary blastomycosis in mouse strains

The immunological basis for a >10-fold resistance of outbred CD-1 mice compared to inbred BALB/c mice to pulmonary blastomycosis was investigated. Bronchoalveolar macrophages (BAM) from CD-1 mice killed yeast cells of Blastomyces dermatitidis (Bd) by 25% and this increased to 59% when activated by IFN-gamma. In contrast, BAM from BALB/c mice lacked significant killing (5%) of Bd but could be activated by IFN-gamma for enhanced killing (19%). Peritoneal macrophages (PM) from CD-1 mice had significant fungicidal activity for Bd (43%) and this increased to 63% with IFN-gamma treatment. By contrast, PM from BALB/c mice did not significantly kill Bd (14%) but were activated by IFN-gamma for significant killing (24%). Fungicidal activity of peripheral blood polymorphonuclear neutrophils (PMN) from CD-1 (87%) was greater than that of BALB/c (75%) (P<0.05). Macrophage inflammatory protein-1alpha (MIP-1alpha) production by BAM from BALB/c was significantly less than that from CD-1 in response to co-culture with Bd. IFN-gamma production by CD-1 spleen cells in response to concanavalin A (Con A, 1microg/ml) was 8-fold greater than that by BALB/c spleen cells. In contrast, BAM and PM from BALB/c mice in co-culture with Bd secreted several-fold more TNFalpha than BAM or PM from CD-1 mice. IL-2 production by BALB/c spleen cells in response to Con A was 3- to 4-fold greater than that by CD-1 spleen cells. Depressed IL-2 production by Con A stimulated CD-1 spleen cells correlated with depressed proliferative responses. Resistance of CD-1 mice to pulmonary blastomycosis correlates with enhanced fungicidal activity of BAM, PM, PMN, and IFN-gamma production by Con A stimulated spleen cells, compared to BALB/c mice. Consistent with the in vitro enhancement of effector cell function by IFN-gamma, in vivo therapy with IFN-gamma significantly (P<0.0001) improved survival of BALB/c mice with pulmonary blastomycosis.

Interaction between conidia, lung macrophages, immunosuppressants, proinflammatory cytokines and transcriptional regulation

The immunosuppressive effect of dexamethasone (DEX) on macrophage killing activity and cytokine production in response to Aspergillus fumigatus conidia is antagonized by granulocyte-macrophage colony-stimulating factor (GM-CSF). However, the intersection of signaling pathways and the molecular mechanism of this antagonism remain to be defined. We postulated that DEX inhibition of NF-kappaB was opposed by induction of IkappaB kinases (IKK) by GM-CSF + conidia stimulation, degradation of IkappaB, and release of nuclear factor kappa B (NF-kappaB). This hypothesis was tested using resident peritoneal macrophages from CD-1 mice and the murine macrophage RAW 264.7 cell line. Macrophages were unstimulated or stimulated with A. fumigatus conidia and simultaneously treated with DEX, GM-CSF or DEX + GM-CSF for 2 4 hours. IkappaB degradation in cytoplasmic extracts and translocation of NF-kappaB in nuclear extracts was measured by Western blot analysis. This showed GM-CSF reverses the immunosuppressive effect of DEX by enhancing the degradation of IkappaB and promoting the translocation of NF-kappaB to the nucleus. This would allow the production of proinflammatory cytokines by macrophages, facilitating resistance to A. fumigatus.

Fungicidal activity of human peripheral blood leukocytes againstParacoccidioides brasiliensisyeast cells

Although epidemiological findings suggest that normal humans are resistant to Paracoccidioides brasiliensis infection, the host defense mechanisms against this fungus have not been fully understood. Here we examined human leukocytes for antifungal activity against yeast cells of this fungus, using an improved mycological culture medium with high plating efficiency for the yeast cell. In an attempt to minimize the impairment of leukocyte activities during the isolation process, leukocytes removed by centrifugation from a buffy coat of peripheral blood were used in the antifungal assay without further fractionation. The leukocytes thus prepared effectively killed P. brasiliensis yeast cells within the first 4 h of co-culture. Adding interferon-gamma (37 ng/ml), granulocyte-macrophage colony-stimulating factor (5 ng/ml), interleukin (IL)-1beta (12 ng/ml), or IL-4 (12 ng/ml) to the assay system enhanced the leukocyte antifungal (growth inhibitory) activity by 48 h. By contrast, addition of IL-8 (50 ng/ml) impaired the leukocyte activity. Tumor-necrosis factor-alpha (50 ng/ml) or IL-10 (25 ng/ml) had no effect in this respect. Dexamethasone (1 micromol/l) reduced the antifungal activity of leukocytes. This is the first demonstration that human leukocytes are able to effectively kill yeast cells of P. brasiliensis.

Combined action of micafungin, a new echinocandin, and human phagocytes for antifungal activity against Aspergillus fumigatus

Micafungin, a new echinocandin, inhibits fungal cell wall beta-glucan synthesis. We postulated micafungin and host phagocytic cells could act together in damaging fungi. Using the metabolic XTT assay, micafungin alone (0.01 and 0.10 microg/ml) inhibited Aspergillus fumigatus germlings by 48% and 61%, respectively. Polymorphonuclear neutrophils (PMNs) inhibited germlings by 53%. Micafungin at 0.01 or 0.10 microg/ml and PMNs resulted in additive inhibition, 82% and 99%, respectively. Monocyte-derived macrophage (MDM) monolayers inhibited germling growth by 66%; micafungin (0.01 or 0.10 microg/ml) alone inhibited by 32% and 42%, respectively. MDMs and micafungin (0.01 or 0.10 microg/ml) caused an additive inhibition of growth, 85% and 95%, respectively. Hyphae were generated by incubation of conidia for 24 h with or without micafungin. PMNs alone, added to hyphae, inhibited growth by 19% in the subsequent 20 h. Hyphae generated in the presence of micafungin (0.10 microg/ml) and subsequently cultured with micafungin for 24 h inhibited growth by 64%. PMNs plus micafungin resulted in 82% inhibition. Monocytes alone inhibited hyphal growth by only 5%. Hyphae produced in the presence of micafungin (0.01 microg/ml) and incubated again with micafungin for 24 h inhibited growth by 47%; combination with monocytes resulted in 62% inhibition. These data indicate that micafungin inhibits growth of tissue forms of A. fumigatus, and phagocytes and micafungin together have an additive effect. These findings support the thesis that the greater efficacy of micafungin in vivo compared with in vitro could be due to combined effect of phagocytic cells and micafungin.

Synergistic antifungal effect of fluconazole and human polymorphonuclear leukocytes on Paracoccidioides brasiliensis: effect of interferon-gamma and granulocyte-macrophage colony-stimulating factor

To better understand the in vivo efficacy of fluconazole (FCZ), we investigated the possible synergy of fungistatic FCZ with human polymorphonuclear leukocytes (PMN) against Paracoccidioides brasiliensis (Pb). The effect of interferon-gamma (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in this system was also studied. For this purpose, FCZ, PMN, PMN + FCZ, PMN + IFN-gamma, PMN + IFN-gamma + FCZ, PMN + GM-CSF and PMN + GM-CSF + FCZ were co-cultured with Pb and the cfu of Pb was measured. The antifungal effect of FCZ on yeast cells of Pb was concentration-dependent. At 0.1 microg ml(-1), FCZ had no effect on the growth of Pb. At 0.2 microg ml(-1) FCZ showed a growth-inhibitory effect on three isolates of Pb in a long-term (120 h) assay, and at 0.6 microg ml(-1) or higher FCZ was fungicidal. Fungistatic concentration of FCZ (0.4 microg ml(-1)) acted synergistically with fungistatic PMN for killing isolate Bt-4 during the first 24 h of co-culture. Moreover, IFN-gamma and GM-CSF substantially enhanced the synergistic antifungal effect of PMN and FCZ. These findings provide a better understanding of why FCZ is more efficacious in in vivo models of paracoccidioidomycosis than is predicted by in vitro susceptibility tests.

Regulation by granulocyte-macrophage colony-stimulating factor and/or steroids given in vivo of proinflammatory cytokine and chemokine production by bronchoalveolar macrophages in response to Aspergillus conidia

Production of the proinflammatory cytokines interleukin (IL)-1 alpha and tumor necrosis factor (TNF)-alpha and of the chemotactic chemokine macrophage inflammatory protein (MIP)-1 alpha by bronchoalveolar macrophages (BAMs) from mice in response to Aspergillus conidia was tested after in vivo administration of saline, dexamethasone, cortisone acetate, granulocyte-macrophage colony-stimulating factor (GM-CSF), or a combination. Dexamethasone suppressed production of IL-1 alpha, TNF-alpha, and MIP-1 alpha; GM-CSF reduced secretion slightly but antagonized dexamethasone suppression when the two were given in combination. Cortisone acetate gave results similar to dexamethasone, but cortisone acetate suppression of BAM responses lasted 7 days, > or = 4 days longer than dexamethasone suppression. The effect of GM-CSF on cortisone acetate suppression lasted at least 7 days. GM-CSF could promote resistance to conidia by maintaining proinflammatory responses.

Regulation of bronchoalveolar macrophage proinflammatory cytokine production by dexamethasone and granulocyte-macrophage colony-stimulating factor after stimulation by Aspergillus conidia or lipopolysaccharide

There is substantial evidence that local production of proinflammatory cytokines are very important in host resistance to aspergillosis. Dexamethasone (DEX) down-regulates production of these cytokines by stimulated bronchoalveolar macrophages (BAM) and constitutes a risk factor for aspergillosis. Granulocyte-macrophage colony-stimulating factor (GM-CSF) antagonizes DEX suppression of antifungal activity by BAM. Here we investigated the possibility that GM-CSF could antagonize DEX down-regulation of interleukin (IL)-1alpha and tumour necrosis factor (TNF)-alpha production by stimulated BAM. Control BAM responded to increasing numbers of conidia of Aspergillus fumigatus with increasing production of IL-1 and TNF. DEX (10(-7)M) significantly suppressed IL-1 and TNF production by BAM+conidia. Although GM-CSF did not enhance IL-1 or TNF production by BAM+conidia, GM-CSF significantly antagonized DEX suppression of IL-1 cytokine production. For comparative purposes, lipopolysaccharide (LPS, 1 microg/ml) was used to stimulate BAM in experiments similar to the above. In contrast to the findings with conidia, GM-CSF enhanced the production of IL-1 (5-fold) and TNF (1.5-fold) by LPS treated BAM. DEX suppression of cytokine production by BAM+LPS was modestly but significantly antagonized by GM-CSF. Moreover, differences between regulation of IL-1 and TNF production by BAM+conidia or LPS and peritoneal macrophages (PM)+conidia or LPS were documented. Finally, the anti-inflammatory cytokine IL-10 was minimally produced by BAM + conidia or LPS, but IL-10 was produced by PM + conidia or LPS. In summary, these data indicate that the risk factor for aspergillosis associated with DEX could be lessened in the pulmonary compartment with GM-CSF. On the other hand, desired effects of DEX could be maintained in other compartments.

Protection of peritoneal macrophages by granulocyte/macrophage colony-stimulating factor (GM-CSF) against dexamethasone suppression of killing of Aspergillus, and the effect of human GM-CSF

Murine peritoneal macrophages in vitro could kill Aspergillus fumigatus conidia, and this activity could be suppressed with dexamethasone. Treatment with granulocyte/macrophage colony-stimulating factor (GM-CSF) alone did not boost killing, but GM-CSF treatment concurrently with dexamethasone reversed the dexamethasone suppression. Both recombinant human and recombinant murine GM-CSF were equivalent in this activity, even though the human reagent reportedly does not stimulate differentiation of murine stem cells. Recombinant human GM-CSF could also reverse dexamethasone suppression of bronchoalveolar macrophage conidiacidal activity. Sequential studies with peritoneal macrophages indicated that recombinant human GM-CSF pretreatment also blocked dexamethasone suppression, but the GM-CSF treatment given after dexamethasone did not block the suppressive effect. Recombinant human GM-CSF did not boost spleen cell proliferation to a mitogenic stimulus, and did not reverse dexamethasone suppression of proliferation. These studies suggest GM-CSF treatment prior to and concurrent with steroid immunosuppression may ameliorate the steroid effect on tissue macrophage antifungal activity, but does not affect steroid suppression of T-cell immunity.

Effect of granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor on polymorphonuclear neutrophils, monocytes or monocyte-derived macrophages combined with voriconazole against Cryptococcus neoformans

The antifungal activity of voriconazole (VCZ) was tested against Cryptococcus neoformans (Cn) with and without the addition of polymorphonuclear neutrophils (PMN), monocytes or monocyte-derived macrophages (MDM) in vitro. Human effector cells with and without the addition of VCZ were incubated with Cn for 24 h. PMN, mono and MDM alone resulted in 61%, 34% and 23% inhibition of Cn, respectively (n = 3, P<0.01). VCZ at 0.01 and 0.05 microg ml(-1) alone resulted in 48% inhibition and 19% killing (n = 6). The addition of VCZ at 0.01 and 0.05 microg ml(-1) to human effector cells enhanced killing of Cn by 51% and 71% for the PMN, 41% and 58% for the mono, and 14% and 34% for the MDM, respectively. The addition of either granulocyte colony-stimulating factor (G-CSF) or granulocyte-macrophage colony stimulating factor (GM-CSF) significantly enhanced the ability of human effector cells to kill Cn. G-CSF and GM-CSF plus PMN resulted in 47% and 46% killing, respectively; GM-CSF plus monocytes or MDM resulted in 31% or 22% killing, respectively. G-CSF and GM-CSF further enhanced the collaborative killing effect of human effector cells and VCZ. At 0.01 and 0.05 microg ml(-1) of VCZ, G-CSF or GM-CSF enhanced PMN killing to 92% and 93% or 87% and 94%, respectively. GM-CSF enhanced both mono and MDM with VCZ at 0.01 and 0.05 microg ml(-1) in killing Cn to 62% and 86%, and 61% and 84%, respectively. These results suggest that VCZ would have good efficacy in the treatment of Cn infection in humans. Furthermore, VCZ would have enhanced efficacy in clinical settings where either G-CSF or GM-CSF was being used.

Protection of bronchoalveolar macrophages by granulocyte-macrophage colony-stimulating factor against dexamethasone suppression of fungicidal activity for Aspergillus fumigatus conidia

The objectives of this study were to: (i) see if granulocyte macrophage colony-stimulating factor (GM-CSF) could protect bronchoalveolar macrophages (BAM) against suppression by dexamethasone (DEX) and (ii) test the combined effect of GM-CSF and DEX on lymphocyte responses. Murine BAM killed Aspergillus fumigatus conidia by 33 +/- 4% (mean +/- SD) in a 2.5-h assay, unaffected by GM-CSF treatment. Killing by BAM treated with DEX (10(-7) M) for 48 h in vitro was reduced to 13 +/- 6%; however, if GM-CSF (500 U ml(-1)) was present during DEX treatment of BAM, killing of conidia (33 +/- 2%) by BAM was preserved. By contrast, DEX suppression of lymphocyte responses to concanavalin A was maintained during co-culture with GM-CSF. In sequence treatment experiments, initial treatment of BAM with GM-CSF protected against subsequent treatment with DEX. When macrophages were pretreated with DEX, GM-CSF could reverse suppression even when added subsequently, provided DEX treatment was discontinued. These data suggest that it may be possible to suppress lymphocyte responses with DEX, yet at the same time maintain BAM defenses with GM-CSF against pulmonary infections by conidia of A. fumigatus.

In vivo GM-CSF prevents dexamethasone suppression of killing of Aspergillus fumigatus conidia by bronchoalveolar macrophages

Dexamethasone (DEX) is a potent immunosuppressive agent used in the treatment of several disorders. However, despite its beneficial effects, DEX puts patients at risk for opportunistic infections, especially pulmonary aspergillosis. Previously we reported that in vitro granulocyte-macrophage colony-stimulating factor (GM-CSF) blocks the immunosuppressive action of DEX on bronchoalveolar macrophages (BAMs). Here we report that BAMs freshly isolated from mice treated intraperitoneally with DEX for 24 h had significantly (P<0.01) reduced killing of conidia, i.e., 15 +/- 5% conidia killed by BAMs from DEX-treated mice versus 35 +/- 3% by BAMs from mice given saline, 38 +/- 5% by BAMs from mice given GM-CSF, and 39 +/- 1% by BAMs from mice given both DEX and GM-CSF. On the other hand, in another compartment GM-CSF could not block the DEX reduction of spleen weight and spleen cellularity. Unlike GM-CSF, granulocyte colony-stimulating factor did not block DEX suppression of BAMs. GM-CSF given 24 h before DEX resulted in blocking of DEX suppression of BAM conidiacidal activity. However, when DEX was given 24 h before GM-CSF, DEX suppression of BAM was not reversed. These data show that GM-CSF in vivo blocks the in vivo immunosuppressive effects of DEX on BAM killing of conidia and suggest a potential use of GM-CSF in patients at risk for aspergillosis due to immunosuppressive DEX treatment.

Effects of granulocyte-macrophage colony stimulating factor (GM-CSF) in vivo on cytokine production and proliferation by spleen cells

GM-CSF is a potent stimulator of haematopoietic cells as well as some functions of granulocytes and macrophages. GM-CSF has many clinical uses; however, little is known about the effects of GM-CSF treatment in vivo on the responses of tissue lymphocytes in terms of secretion of Th-1 and Th-2 cytokines. We investigated this issue by measuring the responses of spleen cells from mice 24 h after treatment i.p. with saline or rmGM-CSF. GM-CSF at 16.7-50.0 microg/kg significantly increased (P < 0.01) spleen cellularity 2-2.5-fold and enhanced proliferative responses of non-stimulated (no mitogen) as well as concanavalin A (Con A)-stimulated spleen cells. Secretion of IFN-gamma by Con A (2.5 microg/ml)-stimulated spleen cells was significantly (P < 0.01) increased from 1.8 microg/ml by control spleen cells to 5.2 microg/ml by GM-CSF spleen cells. IL-10 production was greater (0.25 microg/ml, P < 0.05) by Con A-stimulated spleen cells from GM-CSF-treated mice compared to control spleen cells (0.06 microg/ml). By contrast, there were no significant differences in IL-4 production by Con A-stimulated spleen cells from the different groups. These results show that GM-CSF treatment increases spleen cellularity and primes lymphocytes for enhanced responses. The enhanced production of Th-1 cytokines by primed lymphocytes may partially explain the beneficial role of in vivo administration of GM-CSF in several clinical situations.

Combined treatment: antifungal drugs with antibodies, cytokines or drugs

To improve present results with antifungal drugs, modulation of the host immune response is being explored. Human phagocytes of various lineages work cooperatively in vitro with antifungal drugs to inhibit or kill fungal pathogens, and this activity is augmented by several recombinant cytokines. Monoclonal antibodies against the cryptococcal capsule have been shown to act as an adjunct in enhancing the outcome of cryptococcosis in animal models. This approach is now being pursued in systematic clinical trials. In experimental candidiasis, several manipulations of the immune system, via administration of cytokines, gene deletion or antibodies to cytokines, have been shown to significantly affect survival and fungal clearance in vivo. This approach has already been demonstrated to be of benefit with recombinant human granulocyte-colony stimulating factor adjunct therapy of human candidiasis. Combining antifungal drugs of different classes may enhance their therapeutic effect.

The interaction of human monocytes, monocyte-derived macrophages, and polymorphonuclear neutrophils with caspofungin (MK-0991), an echinocandin, for antifungal activity against Aspergillus fumigatus

The collaboration between human effector cells and caspofungin (MK-0991), a 1,3-beta-D glucan synthase inhibitor, was studied for antifungal activity against Aspergillus fumigatus. Caspofungin was co-cultured for 24h with either human monocytes (Monos), monocyte-derived macrophages (MDM), or polymorphonuclear neutrophils (PMN) against germlings of A. fumigatus and antifungal activity assessed using the XTT metabolic assay. Caspofungin at 0.1 micorg/ml and 0.05 microg/ml or Monos alone against germlings caused significant inhibition. Microscopically this was correlated with less growth and stunted malformed hyphae. The addition of caspofungin at 0.1 microg/ml and 0.05 microg/ml to the monocyte cultures increased antifungal activity. The inhibition of the combination was significantly greater than drug alone (P <.01) and Monos alone (P <.01). MDM against Aspergillus germlings inhibited hyphal growth. The combination of caspofungin at 0.1 microg/ml and 0.05 microg/ml to the macrophage cultures increased antifungal activity. The growth inhibition by the combination was significantly greater than drug alone (P <.01) and MDM alone (P <.01). There was no significant interference with or enhancement of PMNs and caspofungin. These data support the activity of caspofungin against A. fumigatus in vitro, and indicates a cooperative activity with human effector cells. This suggests caspofungin in vivo would have increased efficacy as it combines with host defenses against A. fumigatus.

Isolation and characterisation of an anticryptococcal protein in human cerebrospinal fluid

An earlier study reported that human cerebrospinal fluid (CSF) has fungistatic activity for Cryptococcus neoformans. The present study reports that molecular sieve fractionation of concentrated CSF yielded three protein peaks, one of which (p2) had anticryptococcal activity. On a DEAE-Sephacel anion-exchange column the active molecular sieve peak (p2) gave two peaks that contained anticryptococcal activity. The first (DEAE-1) eluted with 0.1 M NaCl and the second (DEAE-2) eluted with 0.2 M NaCl in buffer. Fungistatic activity of DEAE-1 was reversed by FeCl3. Moreover, FeCl3 reversed inhibition of C. neoformans growth by CSF. In contrast, activity of DEAE-2 was not reversed by FeCl3, indicating that inhibition was produced by an iron-independent mechanism. Immunoblot assays showed that transferrin was present in DEAE-1 but not in DEAE-2, whereas albumin was present in DEAE-2 but not in DEAE-1. On NuPAGE, DEAE-1 protein migrated as a single band corresponding to transferrin and DEAE-2 protein gave a single band corresponding to albumin. In control experiments, human serum albumin subjected to the same isolation protocol acquired anticryptococcal activity similar to that of DEAE-2. Therefore, CSF albumin (DEAE-2) activity was associated with the isolation protocol. These data indicate that transferrin, present in or isolated from CSF, sequesters trace amounts of ferric iron, inhibits growth of C. neoformans and acts as an innate defence mechanism.

Influence of human sera on the in vitro activity of the echinocandin caspofungin (MK-0991) against Aspergillus fumigatus

There have been several reports that the activity of echinocandin antifungal agents is not affected or decreased in the presence of human sera. It is known that these drugs are bound >80% in animal and human sera. The activity of the echinocandin caspofungin (MK-0991), a 1,3-beta-D-glucan synthase inhibitor, against Aspergillus fumigatus with and without human sera was studied. Conidia of A. fumigatus in microtest plate wells formed germlings after overnight culture in RPMI 1640. Caspofungin was then added with or without serum, and the germlings were incubated at 37 degrees C for 24 h. Human serum (5%) in RPMI 1640 alone did not significantly inhibit the growth of A. fumigatus in vitro. Caspofungin in RPMI 1640 exhibited dose-dependent inhibition, with concentrations of 0.1 and 0.05 microg/ml inhibiting 24.9% +/- 10.4% and 11.7% +/- 3.6%, respectively (n = 10; P < 0.01). The addition of 5% human serum to caspofungin at 0.1 or 0.05 microg/ml increased the inhibition to 78.6% +/- 5.8% or 58.3% +/- 19.2%, respectively (n = 10; P < 0.01 versus controls and versus the drug without serum). Lower concentrations of serum also potentiated drug activity. The effect of human sera was further seen when using caspofungin that had lost activity (e.g., by storage) against A. fumigatus at 0.1 microg/ml. Inactive caspofungin alone demonstrated no significant inhibition of hyphal growth, whereas the addition of 5% human serum to the inactive drug showed 83% +/- 16.5% inhibition (n = 5; P < 0. 01). The restoration of activity of caspofungin was seen at concentrations as low as 0.05% human serum. In contrast to prior reports, this study suggests that human serum acts synergistically with caspofungin to enhance its inhibitory activity in vitro against A. fumigatus.

Correlation of susceptibility of immature mice to fungal infection (blastomycosis) and effector cell function

Immature mice are highly susceptible to blastomycosis, which is similar to other mycoses and has parallels in humans. The murine susceptibility is noteworthy in that it persists beyond the development of resistance to other, nonfungal pathogens and the maturation of most immune functions. As the susceptibility to blastomycosis appeared to be related to an early event after infection, primary effector cell function was studied. We found that peritoneal inflammatory cells, enriched for neutrophils, from immature (3-week-old) mice killed nonphagocytizable Blastomyces dermatitidis cells less (25%) than did cells from mature (8-week) mice (70%) (P<0.01), a defect intrinsic to the neutrophils. This correlated with an impaired immature cell oxidative burst. Killing of phagocytizable Candida albicans was not significantly different, 73 versus 87%. Thioglycolate-elicited cells were more impaired; killing of B. dermatitidis was insignificant, and killing of C. albicans was more impaired in immature (16% killing) than in mature (45%) cells (P<0.02). Peripheral blood neutrophils from mature animals killed B. dermatitidis (41%) more than did those from immature animals (10%) (P<0.02); C. albicans was killed efficiently by both. Resting or activated peritoneal macrophages from both types of animals showed no differences in B. dermatitidis killing. These results suggest that the susceptibility of immature mice is related at least in part to the depressed capacity of their neutrophils to kill B. dermatitidis.

Characterization of an anticryptococcal protein isolated from human serum

Human serum at low concentrations inhibits the growth of Cryptococcus neoformans in vitro. Fractionation of serum yielded a purified inhibitory protein with a molecular mass of approximately 81.8 kDa, a pI of approximately 6.2, and an amino acid sequence that matched that of human transferrin. The inhibitory activity and that of apotransferrin and 5% human serum were reversed by 10 microM freshly prepared FeCl(3).

Antifungal activity of cerebrospinal fluid against Cryptococcus neoformans and Candida species

The effect of human cerebrospinal fluid (CSF) on the growth of Cryptococcus neoformans and Candida species was tested in RPMI-1640. CSF alone was highly fungistatic for both yeasts and inhibited growth in a concentration-dependent manner. Unlike human serum, CSF did not collaborate with fluconazole for killing C. neoformans. Molecular sieve fractionation of CSF on a G-200 Sephadex column yielded a highly antifungal fraction with a molecular weight around 66 kDa. On SDS-PAGE this fraction migrated as a major and a minor band corresponding to the mobility of bovine serum albumin. These novel findings suggest that CSF contains a factor(s) that provides resistance to the growth of C. neoformans or Candida species.

Isolation of a human serum protein that inhibits the growth of Cryptococcus neoformans

Human serum at 5 to 10% (v/v) in tissue culture medium RPMI-1640, inhibits the growth of Cryptococcus neoformans by 80 to 93%. Serum fractionated on molecular sieve columns (Sephadex G-200) yielded an active protein fraction. This fraction at 100 micrograms protein/ml inhibited the growth of C. neoformans by 54%. When an active G-200 fraction was applied to a dye affinity column (Affi-Gel Blue) the fraction with inhibitory activity was bound by the column and was eluted with 1.4 M NaCl in 0.1 M phosphate buffer (pH 7.4). The bound fraction at 62.5 micrograms protein/ml inhibited C. neoformans growth by 82%. On native polyacrylamide gel electrophoresis (Nu-PAGE) the bound fraction migrated as a major and a minor band. Under the reducing conditions of sodium dodecyl sulfate (SDS)-PAGE the bound fraction yielded 4 prominent bands with MW ranging from 175 kDa to 45 kDa. Purification of the active Sephadex G-200 peak was achieved using an anion exchange column (DEAE-Sephacel). Protein eluted with 0.1 M NaCl had strong anticryptococcal activity (12.5 micrograms/ml, 79% inhibition), which in SDS-PAGE migrated as a single band with an approximate MW of 85 kDA. This protein appears important in natural host resistance to C. neoformans and polymorphisms or deficiencies may have epidemiologic and diagnostic relevance.

Human defenses against Cryptococcus neoformans: an update

Cryptococcus neoformans var. neoformans is an opportunistic fungal pathogen, especially in AIDS patients, and is found world-wide. On the other hand, Cryptococcus neoformans var. gatti (CN-g) is restricted to an association with two species of Eucalyptus trees. Alveolar macrophages (AM) constitute the first line of defense to Cryptococcus neoformans and offers some resistance. The inflammatory response to Cryptococcus neoformans with an influx of neutrophils and monocytes affords a second line of defense. Secretion of proinflammatory monokines by human AM is now being defined. The inflammatory phagocytes are efficient in killing Cryptococcus neoformans and offer strong resistance. T and B cell responses to infection, a third line of defense, results in production of lymphokines (IFNg, etc.) and specific antibodies. Enhancement of lymphocyte responses by IL-12 and IL-18 to Cryptococcus neoformans infection appears to be critical. Susceptibility of AIDS patients to Cryptococcus neoformans is associated with low CD4+ T cell counts and likely reduced efficacy of the second line of defense.

Resistance to Coccidioides immitis in mice after immunization with recombinant protein or a DNA vaccine of a proline-rich antigen

Two inbred strains of mice (BALB/c and C57BL/6) were vaccinated with either recombinant expression protein of a Coccidioides immitis spherule-derived proline-rich antigen (rPRA) in monophosphoryl lipid A-oil emulsion adjuvant or a DNA vaccine based on the same antigen. Four weeks after vaccination, mice were infected intraperitoneally with arthroconidia. By 2 weeks, groups of mice receiving saline or plasmids with no PRA insert exhibited significant weight loss, and quantitative CFUs in the lungs ranged from 5.9 to 6.4 log10. In contrast, groups of mice immunized with either rPRA or DNA vaccine had significantly smaller pulmonary fungal burdens, ranging from 3.0 to 4.5 log10 fewer CFUs. In vitro immunologic markers of lymphocyte proliferation and gamma interferon (IFN-gamma) release after splenocytes were stimulated with rPRA correlated with protection. Also, plasma concentrations of rPRA-specific total immunoglobulin G (IgG), IgG1, and IgG2a showed increases in vaccinated mice. These studies expand earlier work by demonstrating protection in mice which differ in H-2 background, by using an adjuvant that is potentially applicable to human use, and by achieving comparable protections with a DNA-based vaccine. Our in vitro results substantiate a Th1 response as evidenced by IFN-gamma release and increased IgG2a. However, IgG1 was also stimulated, suggesting some Th2 response as well. PRA is a promising vaccine candidate for prevention of coccidioidomycosis and warrants further investigation.

Collaboration of human phagocytes with LY 303366 for antifungal activity against Aspergillus fumigatus

LY 303366, an inhibitor of 1, 3-beta-D-glucan synthase, was tested alone, or in co-culture with neutrophils or monocytes, for antifungal activity against Aspergillus fumigatus using the XTT metabolism assay. LY 303366 at 0.1 mg/L for 48 h significantly inhibited growth by conidia in a microtest plate XTT assay system. Inhibition was similar if the drug was removed after only 24 h. Microscopically this correlated with less growth and stunted malformed hyphae. LY 303366 (0.1 mg/L) also inhibited the further growth of germlings (43%) in a 24 h assay. Antifungal activity of neutrophils against 24 h control hyphal growth was limited at an effector: target ratio of 400:1. In co-cultures of neutrophils plus drug with hyphal growth from 24 h LY 303366 cultures the antifungal activity was additive. Neutrophils had a similar additive effect even if the drug were not present (i.e. when germinating conidia were pretreated with drug). Under conditions where monocytes did not have significant antifungal activity against hyphae, they collaborated with LY 303366 for significantly increased inhibition from 38% by LY 303366 alone to 67% by co-culture. Thus, LY 303366 has activity against germinating or germinated conidia of Aspergillus, human effector cells act co-operatively with LY 303366, and LY 303366 can sensitize germinating conidia for damage by host cells.

Anticryptococcal activity of voriconazole against Cryptococcus neoformans var. gatti vs var. neoformans: comparison with fluconazole and effect of human serum

Voriconazole (VCZ), a new wide-spectrum antifungal triazole currently in development, was tested for activity against Cryptococcus neoformans (CN) var. gattii and var. neoformans in RPMI-1640 (RPMI) or RPMI plus human serum. In RPMI VCZ was 10-fold more inhibitory than FCZ for both varieties of CN. In the presence of human serum neither VCZ nor FCZ had enhanced activity against CN var. gattii. By contrast, both VCZ and FCZ had significantly increased activity in the presence of serum against CN var. neoformans. The lack of serum-enhancing activity for VCZ or FCZ against CN var. gattii may reflect the in vivo situation and predict less efficacy in CN var. gattii infections.

Development of macrophage anticryptococcal activity in vitro is dependent on endogenous M-CSF

We previously showed that nonactivated resident murine peritoneal macrophages (PM) from five strains (e.g., BALB/c) have C'-dependent fungistasis for Cryptococcus neoformans in 24-h coculture, but not CD-1 PM unless culture time was extended or M-CSF treatment was used. We studied effect of a rat IgG1 monoclonal (m) antibody (Ab) to murine M-CSF receptor on this anticryptococal activity. Culture of BALB/c PM with mAb, diluted 1:10, prechallenge reduced fungistasis from 58 to 21% (P < 0.01), whereas further 10-fold dilutions did not. Moreover, M-CSF pretreatment (5000 U/ml) significantly enhanced fungistasis (to 85%), whereas adding mAb 1:10 or 1:100 reduced that (to 58 and 77%, respectively, P < 0.01). In 48-h culture CD-1 PM had 39% fungistasis, reduced to 0% by mAb, M-CSF treatment of CD-1 PM increased fungistasis to 72%, which was reduced to 13 or 58% (P < 0. 001) by 1:10 or 1:100 mAb, respectively. Complete blocking by mAb of CD-1 PM activity was consistent with lack of measurable early endogenous CD-1 M-CSF production. Increasing exogenous M-CSF could overcome the inhibition by mAb (64% fungistasis BALB/c PM reduced to 11% with inhibition by mAb or increased to 94% with 5000 U/ml M-CSF; 37% with both mAb and M-CSF, 51% with mAb and 10,000 U/ml; P < 0.05, 5000 U/ml + mAb vs 10,000 U/ml + mAb). Moreover, rabbit Ab to M-CSF significantly reduced anticryptococcal activity of untreated BALB/c macrophages. In summary, development of PM fugistatic activity is dependent on endogenous M-CSF, since it is blocked by anti-receptor mAb (as is exogenous M-CSF stimulation) or anti-M-CSF Ab, and macrophages of the mouse strain with delayed activity had no measurable early M-CSF production.

Activity of voriconazole combined with neutrophils or monocytes against Aspergillus fumigatus: effects of granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor

Voriconazole (VCZ) was tested for antifungal activity against Aspergillus fumigatus hyphae alone or in combination with neutrophils or monocytes. Antifungal activity was measured as percent inhibition of hyphal growth in assays using the dye MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] or XTT [2, 3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxa nilide ]. With both assays, VCZ inhibited hyphal growth at concentrations of <1 microgram/ml and was almost as active as amphotericin B. VCZ (0.6 microgram/ml) was sporicidal, as was amphotericin B (0.4 microgram/ml). With both the MTT and XTT assays, neutrophils alone inhibited hyphae; when combined with VCZ, there was additive activity. Both granulocyte colony-stimulating factor- and granulocyte-macrophage colony-stimulating factor (GM-CSF)-treated polymorphonuclear neutrophils (PMN) had enhanced inhibition of hyphal growth. Moreover, such treatment of PMN also enhanced the collaboration of PMN with VCZ. Monocytes inhibited hyphal growth. When VCZ was combined with monocytes or monocytes were treated with GM-CSF, inhibition was significantly increased, to similar levels. However, the combination of VCZ with GM-CSF treatment of monocytes did not significantly increase the high-level inhibition by monocytes with either agent alone.

Damage to yeast cells of Cryptococcus neoformans by voriconazole and fluconazole: a culture and microscopic study

A systematic cultural, cytological and microscopic study of voriconazole (VCZ) and fluconazole (FCZ) damage to Cryptococcus neoformans over time was made. When haemocytometer counts were compared with colony-forming units (cfu) viability decreased with increased drug concentration and prolonged treatment time up to 48 h. Percentage viability by vital staining correlated with cfu. Concentrations of VCZ were found to be 10-fold more potent than FCZ. At 72 h, percentage viability increased in cultures with lower drug concentrations, indicating outgrowth of surviving yeast cells. Drug treatment resulted in a cytological change in a large percentage of yeast cells characterized by a large central vacuole easily observed microscopically. Vital staining showed that there was no direct relationship between cytological changes and non-viability. These novel findings add a new approach for studying the antifungal action of VCZ and FCZ against C. neoformans and provide a new perspective on their antifungal action.

Effect of granulocyte-macrophage colony-stimulating factor on candidacidal activity of neutrophils, monocytes or monocyte-derived macrophages and synergy with fluconazole

The effect of in-vitro granulocyte-macrophage colony-stimulating factor (GM-CSF) treatment of neutrophils, monocytes or monocyte-derived macrophages (MDM) on candidacidal activity was tested. Synergy of effector cells with fluconazole (FCZ) for enhanced killing was also investigated. Incubation of neutrophils with GM-CSF 0.67 microg/L plus Candida albicans Sh27 for 24 h significantly increased candidacidal activity (36% versus 74%). Synergy with FCZ for killing was also significantly increased from 93% to 97% when neutrophils were incubated with GM-CSF. Monocytes cultured with GM-CSF and C. albicans for 24 h had significantly increased fungistatic activity compared to controls and synergy with FCZ for killing was significantly enhanced from 40% to 59%. Monocytes cultured for 3 days with GM-CSF had increased fungistatic activity compared to control MDM and showed synergy with FCZ for significantly enhanced killing (46%) compared to control MDM (12%).