Enhanced resistance of mice against influenza virus infection after local administration of glycoprotein extracts from Klebsiella pneumoniae

Klebsiella pneumoniae alleviates influenza-induced acute lung injury via limiting NK cell expansion

A protective effect induced by bacterial preinfection upon a subsequent lethal influenza virus infection has been observed, but the underlying immune mechanisms have not yet been fully elucidated. In this study, we used a mouse model of Klebsiella pneumoniae preinfection to gain insight into how bacterial preinfection influences the subsequent lethal influenza virus infection. We found that K. pneumoniae preinfection significantly attenuated lung immune injury and decreased mortality during influenza virus infection, but K. pneumoniae-specific immunity was not involved in this cross-protection against influenza virus. K. pneumoniae preinfection limited NK cell expansion, which was involved in influenza-induced immune injury and death. Furthermore, K. pneumoniae preinfection could not control NK cell expansion and death during influenza virus infection in Rag1(-/-) mice, but adoptive transfer of T cells from wild-type mice was able to restore this protective effect. Our data suggest that the adaptive immune response activated by bacterial infection limits the excessive innate immune response induced by a subsequent influenza infection, ultimately protecting mice from death.

Roles of adjuvant and route of vaccination in antibody response and protection engendered by a synthetic matrix protein 2-based influenza A virus vaccine in the mouse

Background

The M2 ectodomain (M2e) of influenza A virus (IAV) strains that have circulated in humans during the past 90 years shows remarkably little structural diversity. Since M2e-specific antibodies (Abs) are capable of restricting IAV replication in vivo but are present only at minimal concentration in human sera, efforts are being made to develop a M2e-specific vaccine. We are exploring a synthetic multiple antigenic peptide (MAP) vaccine and here report on the role of adjuvants (cholera toxin and immunostimulatory oligodeoxynucleotide) and route of immunization on Ab response and strength of protection.

Results

Independent of adjuvants and immunization route, on average 87% of the M2e-MAP-induced Abs were specific for M2e peptide and a variable fraction of these M2e(pep)-specific Abs (average 15%) cross-reacted with presumably native M2e expressed by M2-transfected cells. The titer of these cross-reactive M2e(pep-nat)-specific Abs in sera of parenterally immunized mice displayed a sigmoidal relation to level of protection, with EC₅₀ of ~20 μg Ab/ml serum, though experiments with passive M2e(pep-nat) Abs indicated that serum Abs did not fully account for protection in parenterally vaccinated mice, particularly in upper airways. Intranasal vaccination engendered stronger protection and a higher proportion of G2a Abs than parenteral vaccination, and the strength of protection failed to correlate with M2e(pep-nat)-specific serum Ab titers, suggesting a role of airway-associated immunity in protection of intranasally vaccinated mice. Intranasal administration of M2e-MAP without adjuvant engendered no response but coadministration with infectious IAV slightly enhanced the M2e(pep-nat) Ab response and protection compared to vaccination with IAV or adjuvanted M2e-MAP alone.

Conclusion

M2e-MAP is an effective immunogen as ~15% of the total M2e-MAP-induced Ab response is of desired specificity. While M2e(pep-nat)-specific serum Abs have an important role in restricting virus replication in trachea and lung, M2e-specific T cells and/or locally produced Abs contribute to protection in upper airways. Intranasal vaccination is preferable to parenteral vaccination, presumably because of induction of local protective immunity by the former route. Intranasal coadministration of M2e-MAP with infectious IAV merits further investigation in view of its potential applicability to human vaccination with live attenuated IAV.

The immunomodulating glycoprotein extract from Klebsiella pneumoniae RU 41740 exerts a suppressive effect on human monocyte death by apoptosis

Programmed cell death or apoptosis is a physiological cell suicide process that can be suppressed by survival factors. Monocytes undergo rapid apoptosis in culture, unless signalled by cytokines or the bacterial lipopolysaccharide LPS. We have investigated the effect on monocyte apoptosis of the immunostimulating agent RU 41740 (Biostim), a glycoprotein extract from the Klebsiella pneumoniae K2O1 strain that is used for the prevention of recurrent infections. RU 41740, as LPS, strongly enhanced monocyte survival in vitro, an effect related to apoptosis suppression. RU 41740 at concentration ranging from 1 ng/ml to 10 microg/ml prevented apoptosis induced both by survival factor deprival and by gamma-irradiation. Our observation suggests that enhancement of monocyte survival may represent a component of the reported immunostimulating effect of this compound.

Determination of the antiinfectious activity of RU 41740 (Biostim) as an example of an immunomodulator

Evaluation of the anti-infectious activity of an immunomodulator performed either in vitro or in vivo in animals as in humans must answer three questions: what are the targets? what models should be used to study the mechanism of action? what methodology should be selected for the assessment of therapeutic benefit? In the case of RU 41470 (Biostim), an immunomodulator with a known structure and of biological origin affects immunocompetent cells and two essential mediators: II1 and CSF. Because of multiple interactions between anti-infectious, anti-inflammatory and anti-allergic responses, as well as the pleiotropism of mediators, there exists no absolute predictive index of activity in vivo and, independently of models of immune deficiency, experimental infections are a particularly useful pharmacological model for study of the anti-infectious activity of any immunomodulator. In this model, RU 41470 tested by oral, intraperitoneal and aerosol administration, proved to be active regardless of the type of infectious agent for extracellular bacteria, intracellular bacteria, viruses or yeasts. Because of special local features of anti-infectious defences (pulmonary, cutaneous), the target organ must be identified when studying mechanism of action. RU 41740 stimulates the metabolic activities of alveolar macrophage and the target organ is the respiratory tract. From a clinical pharmacology standpoint, stimulation of different immune components has been investigated with RU 41470 at different dosages, using double-blind versus placebo designs. Target pathology, regardless of severity, includes a risk of infection and the existence of an immunological deficiency. Chronic bronchitis is a reference pathology since patients are subject to episodes of infection, resulting in acute decompensation and contributing to worsening of the ventilatory obstructive disorder. Clinical efficacy in terms of anti-infectious prophylaxis must be evaluated by a strict methodological approach: randomized double-blind placebo-controlled trials with prolonged follow-up. RU 41470 is effective in prophylaxis of respiratory infections in chronic bronchitis (reduction in the number of respiratory infections, their duration and in antibiotic consumption) and in prophylaxis of respiratory tract infections in children over one year old. Clinicians faced with the perplexity of the mechanism of action of immunomodulators and their number are preoccupied above all by the response which such an anti-infectious immunomodulator can offer in a context of clinical reality.(ABSTRACT TRUNCATED AT 400 WORDS)

Klebsiella pneumoniae glycoprotein RU-41740 enhances resistance of mice against Mycoplasma arthritidis-induced arthritis

The effect of a purified glycoprotein extract from Klebsiella pneumoniae with non-specific immunostimulating properties (RU 41740) on the development and course of mycoplasma arthritis was investigated. Male A/J mice aged 2-3 months were given RU-41740 either intraperitoneally (i.p.) or orally prior to injection with Mycoplasma arthritidis. RU-41740 injected i.p. at 0.1 mg kg-1 or given orally at 1 mg kg-1 prior to the infection and subsequently on alternate days enhanced the resistance of mice to mycoplasma arthritis (P less than 0.001). Doses of 1 mg kg-1 i.p. or 10 mg kg-1 orally did not modify the course of the arthritis significantly, probably due to immunosuppressive factors from monocytes. It is suggested that RU-41740 protects the mice by stimulating macrophages. This immunostimulant might prove useful in the treatment of mycoplasma diseases, especially in the immunocompromised host.

A skin suction blister model in hairless rats: application to the study of anti-inflammatory and immunomodulatory drugs

A suction blister model was developed in the hairless rat, in order to study the effects of various agents on the migration of polymorphonuclear leukocytes (PMN). A standardized abrasion, a suction blister, was formed by applying negative pressure to the skin and then separating the epidermis from the dermis. A migration chamber containing serum as the chemoattractant was placed over the wound. After 6 h of migration, the cells in the chamber were harvested, counted and identified. We evaluated PMN migration after treating the animals with active compounds: niflumic acid, and anti-inflammatory drug, and RU 41740, an immunomodulator. This in vivo model provided reproducible data and could be used to study further the functional properties of PMN. In addition, because this assay can also be used in man, a drug found to be effective in the animal system could then be tested for its activity in man.

The effect of Biostim (RU-41740) on the expression of cytokine mRNAs in murine peritoneal macrophages in vitro

The immunomodulatory agent Biostim (RU-41740) was investigated for its ability to induce the expression of cytokine mRNAs in murine peritoneal macrophages in vitro. Northern blot analysis showed that in quiescent macrophage populations, both IL-1 alpha and IL-1 beta mRNA levels were dramatically increased in response to 1 microgram/ml Biostim. Dot-blot analysis showed that in quiescent macrophage populations the expression of mRNAs for IL-1 alpha, IL-1 beta, IL-6 and TNF-alpha could be elevated by concentrations of Biostim as low as 1-10 pg/ml, detectable after 3 h exposure. In parallel experiments LPS was effective only at the higher concentration of 10 ng/ml. Time-course analysis showed that the expression of these cytokine mRNAs was transient, peaking after 1-3 h; only transcripts of IL-1 beta were detectable after 23 h exposure. No effects were seen on the expression of actin, a high-turnover housekeeping gene. We propose that this type of analysis represents a sensitive, specific and reproducible method for assessing the ability of drugs and chemicals to modulate the expression of cytokines that play a pivotal role in the induction of the immune response.

Immunological activities of RU-41740, a glycoprotein extract from Klebsiella pneumoniae. III. Role of LPS-like and LPS-non-related molecules

RU-41740, a glycoprotein complex extracted from Klebsiella pneumoniae, is an immunomodulating agent which acts on B cells and macrophages. It has been shown that RU-41740 is composed mainly of two macromolecular fractions, F1, having an LPS-related structure, and P1, with a proteoglycan structure. In the present paper, the effects of these molecules on B cells and on IL-1 and tumour necrosis factor (TNF), production by macrophages were compared. Data reveal that both fractions were mitogenic for murine B cells and induced IL-1 and TNF production by macrophages. The LPS-like fraction (F1) was sensitive to polymyxin B and was unable to activate macrophages and spleen cells from LPS non-responder mice. The P1 fraction was mitogenic for B cells and induced the production of IL-1 and TNF activities by macrophages from LPS non-responder C3H/HeJ mice. The cytotoxic activity was due to TNF alpha, since treatment with anti-TNF alpha antiserum abrogated the lytic activity of supernatants from stimulated macrophages. The differences observed between P1 and F1 fractions in terms of sensitivity to polymyxin B and activity towards C3H/HeJ spleen cells and macrophages suggest that the two structurally distinct molecules isolated from RU-41740 could act at different sites on immunocompetent cells.

Increase in the number and the phagocytic function of guinea pig pulmonary and peritoneal macrophages following oral administration of RU 41740, a glycoprotein extract from Klebsiella pneumoniae

RU 41740 (Biostim) which is a purified glycoprotein extract from Klebsiella pneumoniae, is an orally active non-specific immunostimulant. In guinea pigs, 8 days after a 7 days oral administration of RU 41740 (10 or 100 mg/kg/day), an increase in the cell population of the pulmonary and peritoneal cavities was observed, especially in that of the macrophages. RU 41740 also enhanced the phagocytic activity of both the alveolar and peritoneal macrophages, when their chemotactic activity was not significantly modified. This increase in the number of pulmonary macrophages and the stimulation of their phagocytic function might explain the protective effect afforded by the oral administration of Biostim against respiratory infections in patients with chronic bronchitis.

In vitro modulation of human monocytes functions by RU 41740 (Biostim)

The in vitro effects of RU 41740, a mixture of two glycoproteins extracted from K. pneumoniae and possessing immunomodulatory activity, on human monocyte's cytotoxic activity, migratory capacity and monokine production were investigated. Exposure to RU 41740 in nanogram concentrations was associated with rapid increases in IL-1 and TNF production and marked augmentation in the monocytes' killing of TNF-sensitive targets, whereas killing of TNF-insensitive targets required longer exposures to microgram concentrations of this drug. Using otherwise effective treatment conditions, RU 41740 did not directly affect monocyte's spontaneous and FMLP-induced migration. The possible role of mononuclear cells stimulation and increased production of effector and regulatory monokines in the immunomodulatory activity of this product is addressed.

Enhancement of bronchoalveolar cell recovery and stimulation of alveolar macrophage chemiluminescence and resistance to influenza virus after treatment with RU 41821 aerosol

Aerosol treatment with RU 41821, a glycoprotein extract from Klebsiella pneumoniae, was tested in mice for its effect on the kinetics of the induction of bronchoalveolar cells (i.e., alveolar macrophages, monocytes, lymphocytes, and polymorphonuclear leukocytes). RU 41821 led to an increase in the total number of bronchoalveolar cells. The largest increase was observed for polymorphonuclear leukocytes, and more moderate increases occurred in the numbers of alveolar macrophages, monocytes, and lymphocytes. The alveolar macrophages recruited in response to RU 41821 were activated, as indicated by luminol-dependent chemiluminescence in response to stimulation by opsonized zymosan. The effects of five RU 41821 aerosol treatments and those of a single treatment were further examined in vivo by aerosol infection of mice inoculated with a mouse-pathogenic influenza virus. The maximum protective effect was obtained after five once-a-day treatments and was correlated with the largest increase in the total number of bronchoalveolar cells.

RU-41740 (K. pneumoniae glycoprotein) enhances resistance to experimental candidiasis and stimulates phagocytic functions

RU-41740, a purified glycoprotein extract from Klebsiella pneumoniae, (which is an efficient non-specific immune activator in a broad spectrum of in vitro and in vivo reactions) was administered either orally or parenterally in the mouse. It enhanced the resistance of mice to candidiasis, both in terms of survival rate and a decrease in viable yeast cell recovery in kidneys. The drug administered at 0.1 mg or 1 mg/kg augmented 4-fold the mean survival time (MST) of animals infected with 1 to 2 X 10(6) Candida albicans, both by the intraperitoneal and the intravenous route. The effect of the orally administered drug was less striking but nonetheless present. At 10 mg/kg, the MST of infected animals increased about 2-fold. In vitro, in the presence or absence of zymosan, the drug at 10 or 100 micrograms/ml was able to stimulate the phagocytic process of elicited mouse peritoneal cells (65% polymorphonuclear cells, 35% macrophages) and human peripheral blood cells (95% polymorphonuclear cells, 5% monocytes) in terms of activated oxygen species production. The involvement of polymorphonuclear cells in the mechanisms of natural resistance to C. albicans infection led us to discuss the role of these cells as targets for the drug.

Effects of RU 41740 aerosol treatment on mouse bronchoalveolar cells, and protection afforded against influenza virus infection

RU 41740, an immunomodulating compound extracted from Klebsiella pneumoniae, was previously shown to enhance mice resistance to bacterial and viral lung infections. To explore lung defense mechanisms, we studied the influence of RU 41740 aerosol treatment on the bronchoalveolar cell populations. Five successive daily RU 41740 aerosol treatments induced a large accumulation of leukocytes in the lungs 4h after the last treatment. Polymorphonuclear leukocytes predominated. The numbers of lymphocytes and monocytes rose significantly. A single RU 41740 aerosol treatment significantly raised the number of polymorphonuclears only. A luminol-dependent chemiluminescence assay was used to test the effect of RU 41740 on the opsonized zymosan induced response of alveolar macrophages. In vitro, addition of RU 41740 enhanced this chemiluminescence. After a single RU 41740 aerosol treatment of mice, the chemiluminescence of purified alveolar macrophages from these mice increased significantly. The protective effect of five daily RU 41740 aerosol treatments against influenza virus infection was believed to be due to the great intensity of the cellular response and the polymorphonuclear influx. The alveolar macrophage activation observed might also explain the enhanced resistance of mice to influenza virus infection.

Effects exerted by RU 41740 on oxidative metabolism and migration of rat polymorphonuclear leukocytes collected after induction of one acute non specific inflammatory reaction

The activity of RU 41740, a glycoprotein extract from Klebsiella pneumoniae, endowed with immuno-modulating properties, has been investigated on polymorphonuclear (PMN) leukocyte functions. This report deals with the effect of RU 41740 on oxidative metabolism (assessed by chemiluminescence, 02 consumption and O2- production) and on chemotaxis and random migration (using agarose and Boyden chamber techniques). PMNs were collected from the rat pleural cavity after induction of one acute inflammatory reaction (pleurisy induced by injection of a suspension of calcium pyrophosphate crystals). Experiments were performed in parallel after in vivo treatment or incubation in vitro. RU 41740 enhanced PMN oxidative metabolism and inhibited PMN chemotaxis while random migration was only affected using agarose assay at high concentration. This effect on PMN migration was observed with at least two attractants. These observations have been obtained either after incubation in vitro or administration in vivo. The minimal effective dose was 1 mg/kg in vivo and 0.1 microgram/ml in vitro. These data suggest that RU 41740 acts directly on PMN membrane receptors.

The effect of Biostim (RU 41.740) on natural killer activity in different mouse organs

The effect of Biostim, a mixture of two glycoproteins extracted from K. pneumoniae, on NK activity in lung, blood and spleen was investigated in mice. Marked increases in NK-cytotoxicity for YAC-1 targets were found after single or repeated administrations of this compound by the i.p. or the oral route in the absence of increases of serum IFN. The highest increases in NK activity were found in lymphoid cells recovered from the lung, active treatments with Biostim significantly increasing the proportion of both target-binding cells and lytic conjugate-forming NK cells. In addition to increasing the rate of clearance from lung and spleen of in vivo-injected radiolabelled YAC-1 cells, short (3 h) exposures to Biostim in vitro augmented the NK-cytotoxicity of murine and human cells. By showing that NK cells can also be a target of Biostim, these results can contribute to a better understanding of the mode of action of this immunomodulator.

Immunostimulation of blood monocyte function by RU 41.740 (Biostim) in patients with chronic bronchitis

RU 41.740 (Biostim), a glycoprotein extract from Klebsiella pneumoniae, which is effective in heightening resistance to experimental infections in animals, was examined with regard to influence on human blood monocyte function in vitro after administration to patients with chronic bronchitis in a randomized, double-blind clinical trial. Twelve patients were given Biostim orally (seven patients received 8 mg daily and five patients received 2 mg daily) while eight patients received placebo. In the Biostim group monocyte phagocytosis increased from 1.4 yeast cells per monocyte before therapy to 3.1 yeast cells per monocyte after 1 month (P less than 0.05) with no further increase after 3 months. Monocyte candidacidal activity increased in the Biostim group from 51% before therapy to 69% after 1 month (P less than 0.05) with a decrease to 57% after 3 months. As expected, placebo had no significant effect on monocyte functions. There was no difference between the improvement in the high dose vs the low dose group. These results suggest that Biostim exerts part of its immunostimulatory property by stimulating blood monocyte antimicrobial function.

Modulation of murine hemopoiesis by repeated injections of a glycoprotein extract from Klebsiella pneumoniae

RU 41740, an immunomodulating agent extracted from the cell wall of Klebsiella pneumoniae, was tested for its ability to modulate hemopoiesis in mice treated intraperitoneally for ten days. In such conditions, a moderate anemia could be observed, which was rapidly reversible after the end of treatment. This anemia may partly result from a decrease of bone marrow erythroid colony forming units (CFU-E), this being incompletely compensated by the intrasplenic erythropoiesis. Moreover, the amount of granulocytes and their progenitors, i.e. granulocyte/macrophage colony forming cells (GM-CFC), increased both in the bone marrow and spleen. It is proposed that this effect of RU 41740 on granulopoiesis, which could explain the better resistance to infections in treated animals as observed elsewhere, is partly related to an increase of colony stimulating activity (CSA).