Stimulation of macrophages by Bacillus firmus: production of nitric oxide and cytokines

Immunomodulatory properties of subcellular fractions of a G+ bacterium, Bacillus firmus

Mucosal immunization with non-living antigens usually requires the use of an adjuvant. The adjuvant activity of Bacillus firmus in the mucosal immunization of mice was described by our laboratory previously. In the present study, subcellular localization of B. firmus activities was followed. After mechanical disintegration, subcellular components of bacterium were fractionated by differential centrifugation and salting out. Bacterial cell walls, cytoplasmic membrane fraction, soluble cytoplasmic proteins, and ribosomal fractions were isolated. Their effect on the mouse immune system was studied. Lymphocyte proliferation and immunoglobulin formation in vitro were stimulated by bacterial cell wall (BCW), cytoplasmic membrane (CMF), and ribosomal fractions. BCW and CMF increased antibody formation after intratracheal immunization of mice with influenza A and B viruses, and increased protection against subsequent infection with influenza virus. The BCW fraction even induced intersubtypic cross-protection: Mice immunized with A/California/7/04 (H3N2) + BCW were resistant to the infection by the highly pathogenic A/PR/8/34 (H1N1) virus.

Adjuvant effect of Bacillus firmus on the expression of cytokines and toll-like receptors in mouse nasopharynx-associated lymphoid tissue (NALT) after intranasal immunization with inactivated influenza virus type A

Due to the persisting threat of development of new highly pathogenic influenza A subtypes, a mucosal vaccination which would induce a potent and cross-protective reaction is desirable. We succeeded in mucosal immunization of mice with an inactivated influenza A virus by using delipidated Bacillus firmus (DBF) as adjuvant. The mechanism of adjuvant effect was followed in NALT by comparing the response after intranasal immunization by inactivated influenza virus type A (H1N1) alone, adjuvant alone (DBF), or by a mixture of virus+DBF. Expression of selected gene groups was tested via qPCR at 7 different time-points: cytokines (IL-2, IFN-γ, IL-4, IL-6, and IL-10), type I interferons (IFN-α4, IFN-α11, IFN-α12, and IFN-β), toll-like receptors (TLR2, TLR3, TLR7, and TLR9), iNOS and CCR7. Intranasally administered DBF and the mixture of virus+DBF induced an elevated expression of IFN-γ, IL-6 and IL-10 cytokines, type I interferons, iNOS, and pDC markers in NALT. Multimarker qPCR data was analyzed by relative quantification and by principal component analysis. DBF has been shown to be a very efficient adjuvant for the stimulation of innate immunity after IN immunization. DBF accelerated, increased, and prolonged the antiviral response.

Immunomodulatory effects ofBacillus firmus on mouse peritoneal cellsin Vitro

The effect of nonpathogenic G+ bacterium B. firmus (BF) on stimulation of mouse peritoneal cells in vitro was evaluated by testing nitric-oxide-synthesis induction and cytokine formation. The reactivity was compared of peritoneal cells from two inbred mouse strains, C57B1/6 and BALB/c, which differ in their immunological reactivity. Peritoneal macrophages from C57B1/6 produced more nitric oxide after a 1-d cultivation with inactivated BF than those of BALB/c mice. In both strains, production can be further increased by adding exogenous IFN-gamma to the culture. There were no significant differences between peritoneal cells of these two mouse strains in cytokine production after optimal in vitro stimulation with BF. BF effectively activated peritoneal cells for the production of TNF-alpha, IL-1beta and IL-10, delipidated bacterium (DBF) being more efficient than BF in induction of IL-10 and TNF-alpha. On the other hand, BF had only small effect on IFN-gamma production and no detectable effect on IL-12 production. Macrophage activation by BF/DBF can represent one of the mechanisms responsible for previously described immunomodulatory activity of BF.

Adjuvant effect ofBacillus firmus in intranasal immunization of guinea pigs with inactivated type B influenza virus

Intranasal immunization of guinea pigs with inactivated type B influenza virus plus inactivated Bacillus firmus as an adjuvant compared to the virus alone yields higher titers of serum hemagglutination-inhibiting antibodies and virus-neutralizing antibodies. This phenomenon could be useful in standard serology, especially in the preparation of immune sera against highly pathogenic strains for in vitro diagnosis.

Antileishmanial activity and immune modulatory effects of tannins and related compounds on Leishmania parasitised RAW 264.7 cells

The antileishmanial and immunomodulatory potencies of a total of 67 tannins and structurally related compounds were evaluated in terms of extra- and intra-cellular leishmanicidal effects and macrophage activation for release of nitric oxide (NO), tumour necrosis factor (TNF) and interferon (IFN)-like activities. Their effects on macrophage functions were further assessed by expression analysis (iNOS, IFN-alpha, IFN-gamma, TNF-alpha, IL-1, IL-10, IL-12, IL-18). With few exceptions, e.g., caffeic acid derivatives, these polyphenols revealed little direct toxicity for extracellular promastigote Leishmania donovani or L. major strains. In contrast, many polyphenols appreciably reduced the survival of the intracellular, amastigote parasite form in vitro. Upon activation, e.g., by immune response mediators such as IFN-gamma, macrophages may transform from permissive host to leishmanicidal effector cells. Our data from functional bioassays suggested that the effects of polyphenols on intracellular Leishmania parasites were due to macrophage activation rather than direct antiparasitic activity. Gene expression analyses not only confirmed functional data, they also clearly showed differences in the response of infected macrophages when compared to that of noninfected cells. Conspicuously, infected macrophages showed augmented and prolonged activation of host defense mechanisms, indicating that parasitised macrophages were exquisitely predisposed or "primed" to react to activating molecules such as polyphenols. This promotive effect may be of special benefit, e.g., stimulation of the non-specific immune system selectively at the site of infection and when needed. Although these data provide the basis for an immunological concept of plant polyphenols for their beneficial effects in various infectious conditions, in vivo experiments are essential to prove the therapeutic benefits of polyphenolic immunomodulators.

Intratracheal and intranasal immunization with ovalbumin conjugated withBacillus firmus as a carrier in mice

Inactivated Bacillus firmus (BF), G+ nonpathogenic bacterium of the external environment, was coupled to ovalbumin (OVA) and used in immunization experiments as antigen carrier. Balb/c mice were immunized thrice intra-tracheally and intra-nasally with conjugates of OVA and BF. Surprisingly, administration of OVA-BF conjugates inhibited anti-OVA IgG response in both sera and mucosal secretions if compared to an exposure to OVA alone. The suppression of antigen-specific antibody production was accompanied by promotion of TH1 phenotype.

Immune response after adjuvant mucosal immunization of mice with inactivated influenza virus

Satisfactory mucosal immunity in the respiratory tract is very important for protection against influenza. It can be achieved only by mucosal immunization. Mucosal vaccination with inactivated influenza virus may not be sufficiently effective and suitable adjuvants are therefore sought. We tested intratracheal immunization of mice with inactivate B type influenza virus in a mixture with formolized G+ bacterium Bacillus firmus, whose adjuvant effects have previously been documented in another system. The treatment resulted in a marked increase of both systemic and mucosal antibody response in IgG and IgA classes. Stimulation of T lymphocytes after adjuvant immunization was very mild, no proliferation taking place after specific stimulation with antigen in vitro. However, slightly increased systemic (spleen) and local (lungs) production of cytokines without perceptible Th1/Th2 polarization was determined. B. firmus is an efficient adjuvant in respiratory tract immunization while with subcutaneous immunization it lowers the antibody response.

Role of T cells in the adjuvant effect of Bacillus firmus on the immune system of mice: intranasal and intratracheal immunization study with ovalbumin

Functions of T cells were determined after intranasal and intratracheal immunization of mice with ovalbumin (Ova) and Bacillus firmus (Bf), a Gram-positive nonpathogenic bacterium of the external environment, or delipidated Bf (dBf) as adjuvants, with the aim to elucidate the mechanism of support of Ova-specific antibody production caused by Bf that had been observed in an identical experiment. Neither Bf nor dBf in a mixture with Ova stimulated Ova-specific T-cell response tested as antigen-specific blast transformation. By contrast, a mild polyclonal stimulation was observed in splenocytes from mice given dBf. In vitro incubation of splenocytes with 100 micrograms (but not 10 micrograms) of Bf or dBf led to a highly significant inhibition of proliferation below the control level in all groups of animals. Supernatants of splenocyte cultures were further tested for cytokine production. IL-10 and IFN-gamma were released after in vitro challenge with dBf and in some cases also with Bf. Analysis of sera demonstrated that administration of Ova + adjuvant brought about an increase in anti-Ova IgG1, IgG2a and IgG2b whereas treatment with Ova alone caused a rise in IgG1 only. The role of Bf or dBf in the enhancement of antigen-specific antibody production could be in influencing macrophages and inducing cytokine milieu composed of IL-10, IFN-gamma and other factors that leads to a bystander stimulation of specifically activated Ova-B cell receptor (Ova-BCR)-bearing cells.

Immunostimulatory effect of Bacillus firmus on mouse lymphocytes

Bacillus firmus (a Gram-positive nonpathogenic and harmless bacterium), was shown to be a strong polyclonal activator of mouse B lymphocytes as estimated by ELISA testing of Ig concentrations in culture supernatants after incubation of BALB/c mouse splenocytes with inactivated bacillus. Synthesis of all main Ig classes and all IgG subclasses was stimulated in vitro, the considerable effect on IgA formation being the most interesting feature. B cell stimulation was T cell dependent, as was demonstrated by the effect of B. firmus on all Ig isotypes and by comparison of lymphocyte response of nu/nu mice and heterozygous nu/+ mice. The effect of B. firmus on splenocyte proliferation was stimulatory or suppressive depending on the dose of the bacterium. Increased synthesis of IFN-gamma and IL-10 (detected by ELISA in splenocyte culture supernatants) showed probable stimulation of Th1 and Th2 subpopulations. Considering the stimulatory effect on IgA formation and macrophage stimulation, B. firmus seems to be a prospective mucosal adjuvant and/or probiotic.

Differential effect of Bacillus firmus on immune response and enterocyte brush-border enzyme levels in BALB/c and B10.BR mice

A nonpathogenic bacterium of external environment possessing remarkable immunomodulatory activity, Bacillus firmus (BF) inactivated with formaldehyde, was given intragastrically to two genetically different mouse strains BALB/c (H-2d) and B10.BR/SnPh (B10.BR, H-2k) reared in conventional (CV) and B10.BR strain also in germ-free (GF) conditions. Repeated intragastric administration of BF (500 micrograms every other day over two weeks, starting at the age of 3 months) significantly enhanced intestinal IgA levels in CV BALB/c mice but did not affect intestinal IgA in CV B10.BR mice. In GF B10.BR mice, IgG levels in sera and intestinal washings increased after BF administration compared to CV B10.BR mice. In CV BALB/c mice, specific activity of enterocyte brush-border enzymes (lactase, gamma-glutamyltransferase, alkaline phosphatase) decreased after BF treatment; sucrase (sucrose alpha-glucosidase) activity was not affected. On the other hand, in B10.BR mice, specific activity of gamma-glutamyltransferase and dipeptidyl peptidase IV were higher after administration of BF in both CV and GF groups relative to untreated controls. The activities of lactase and glucoamylase (glucan 1,4-alpha-glucosidase) were significantly stimulated only in the group of GF B10.BR mice treated with formolized BF. The stimulation of immunoglobulin production after BF treatment was accompanied by changes in the levels of enterocyte brush-border enzymes; this responsiveness to BF treatment was genetically regulated.

Proanthocyanidins and related compounds: antileishmanial activity and modulatory effects on nitric oxide and tumor necrosis factor-alpha-release in the murine macrophage-like cell line RAW 264.7

A series of 17 proanthocyanidins and structurally related compounds was tested for activity against Leishmania donovani amastigotes and promastigotes in vitro. Most of the polyphenols significantly inhibited the intracellular survival of L. donovani amastigotes (EC50 0.8-10.6 nM) when compared with the antileishmanial drug Pentostam (EC50 10.6 nM), but all were inactive against the extracellular form (EC50 7.8 to >86 nM). Noteworthy is that all compounds exhibited only moderate or no cytotoxicity against the murine host cells (EC50 7.8 to >56 nM; >25 microg/ml). These polyphenols were further evaluated for immunomodulatory effects on macrophage functions, including release of nitric oxide (NO), tumor necrosis factor-alpha (TNF) and interferon (IFN)-like properties using several functional assays. The results showed that all compounds induced murine RAW 264.7 cells only moderately to release NO (7-26 microM) relative to the reference stimulus IFN-gamma/LPS (119 microM). The TNF-inducing potential of the polyphenols producing 50% lysis in murine L929 cells ranged from absent to 138 U/ml at the host cell subtoxic concentration of 50 microg/ml. The highest TNF-inducing activity was associated with those flavan-3-ols with galloyl groups (98-127 U/ml). For proanthocyanidins, it appeared that an increase in the flavanyl chain length did not enhance the induction of TNF-release (32-86 U/ml and below detection limits for oligomers and polymers, respectively). With interferon-like activities, phylloflavan and a prodelphinidin polymer showed appreciable cytoprotective effects, as reflected by the inhibition of the cytopathic effect of encephalomyocarditis virus on L929 fibroblast cells (38 and 36 U/ml, respectively). All remaining compounds displayed only negligible or moderate protective effects at subtoxic concentrations up to 25 microg/ml (<5 to 12 U/ml). These results indicate that proanthocyanidins and related compounds have favorable antileishmanial activity in vitro and might be considered as beneficial immunological response modifiers provided there are no bioavailability problems.

Enhanced systemic and mucosal antibody responses to a model protein antigen after intranasal and intratracheal immunisation using Bacillus firmus as an adjuvant

Bacillus firmus, a non-pathogenic Gram positive (G+) bacterium of the external environment was investigated for immunomodulatory properties. It stimulated an increase in anti-ovalbumin IgG in sera, bronchoalveolar lavages and intestinal washings after both intranasal (i.n.) and intratracheal (i.t.) immunisation, and enhanced anti-ovalbumin IgA in intestinal secretions and in bronchoalveolar lavage fluid after i.n. or i.t. immunisation, respectively. The immunomodulatory effect of B. firmus on antibody formation was antigen specific.