Immunomodulation by bacterial fractions

Trehalolipid biosurfactants from nonpathogenic Rhodococcus actinobacteria with diverse immunomodulatory activities

Actinobacteria of the genus Rhodococcus produce trehalolipid biosurfactants with versatile biochemical properties and low toxicity. In recent years, these biosurfactants are increasingly studied as possible biomedical agents with expressed immunological activities. Applications of trehalolipids from Rhodococcus, predominantly cell-bound, in biomedicine are also attractive because their cost drawback could be less significant for high-value products. The review summarizes recent findings in immunomodulatory activities of trehalolipid biosurfactants from nonpathogenic Rhodococcus and related actinobacteria and compares their biomedical potential with well-known immunomodifying properties of trehalose dimycolates from Mycobacterium tuberculosis. Molecular mechanisms of trehalolipid interactions with immunocompetent cells are also discussed.

Cytokines: monitors of disease severity for the clinic

BACKGROUND

Cytokines communicate between the cells of the immune system and its targets to maintain homeostasis after injury or pathogenic events. They are involved in almost any pathological situation imaginable.

OBJECTIVE

To verify the importance of cytokines as biomarkers in current preclinical (aetiopathogenic, development of new therapies) and clinical studies (diagnosis, disease severity, prognosis and response to therapy).

METHOD/RESULTS

A Medline search with the query 'cytokine' AND 'biomarker' AND a variable for a variety of biomedical fields, followed by deeper-level searches, demonstrated the immense popularity of cytokines as biomarkers in almost any biomedical field.

CONCLUSION

As cytokines are not disease-specific they do not serve as single diagnostic biomarkers. The strength of the cytokines resides in monitoring disease severity, prognosis and response to treatment.

Effect of breast milk of healthy and allergic mothers on in vitro stimulation of cord blood lymphocytes

Maternal milk has beneficial effects on the development and function of the newborn's immune system. Whether the milk of allergic mother has the same effects as the milk of healthy mothers is not yet quite clear. To contribute to the characterization of its immunomodulatory action, we tested the effect of milk of healthy and allergic mothers on the proliferation and immunoglobulin formation in cultures of cord blood mononuclear leucocytes (CBML) of newborns of healthy and allergic mothers. CBML proliferation was tested by (3)H-thymidine incorporation, IgM, IgG and IgA production by reverse ELISPOT. CBML response was examined in unstimulated cultures and after stimulation with polyclonal activators in the presence or absence of colostrum or milk. The cells of children of allergic mothers have a significantly higher proliferative activity than those of children of healthy mothers. Maternal colostrum/milk in high doses markedly suppresses cell proliferation after stimulation with polyclonal activators, whereas lower milk doses in the cultures have no such effect and exert a rather stimulatory action. Immunoglobulin production by cord blood lymphocytes is also different in the two groups of children. Low basal immunoglobulin formation is increased after stimulation with a strong polyclonal activator of B cells--Bacillus firmus, CBML of children of allergic mothers produce more IgA than those of children of healthy mothers. The stimulated production of all immunoglobulin classes in cells of children of healthy mothers is still enhanced by colostrum/milk. Children of allergic mothers show a markedly increased production of only IgM and IgA. The effect of healthy and allergic colostrum and milk on cell proliferation and immunoglobulin production is similar. The lymphocytes of children of allergic mothers differ from the lymphocytes of children of healthy mothers in their proliferative activity and the ability to form immunoglobulin already at birth.

Where do the immunostimulatory effects of oral proteolytic enzymes (‘systemic enzyme therapy’) come from? Microbial proteolysis as a possible starting point

Enteric-coated proteolytic enzyme preparations like Wobenzym and Phlogenzym are widely used for the so-called 'systemic enzyme therapy' both in humans and animals. Numerous publications reveal that oral proteolytic enzymes are able to stimulate directly the activity of immune competent cells as well as to increase efficiency of some of their products. But origins of the immunostimulatory effects of oral proteolytic enzymes are still unclear. The hypothesis described here suggests that it may be proteolysis of intestinal microorganisms that makes the immune competent cells to work in the immunostimulatory manner. The hypothesis was largely formed by several scientific observations: First, microbial lysis products (lipopolysaccharides, muropeptides and other peptidoglycan fragments, beta-glucans, etc.) are well known for their immunostimulatory action. Second, a normal human being hosts a mass of intestinal microorganisms equivalent to about 1 kg. The biomass (mainly due to naturally occurring autolysis) continuously supplies the host's organism with immunostimulatory microbial cell components. Third, the immunostimulatory effects resulting from the oral application of exogenously acting antimicrobial (lytic) enzyme preparations, such as lysozyme and lysosubtilin, are likely to be a result of the action of microbial lysis products. Fourth, cell walls of most microorganisms contain a considerable amount of proteins/peptides, a possible target for exogenous proteolytic enzymes. In fact, several authors have already shown that a number of proteases possess an ability to lyse the microbial cells in vitro. Fifth, the pretreatment of microbial cells (at least of some species) in vitro with proteolytic enzymes makes them more sensitive to the lytic action of lysozyme and, otherwise, pretreatment with lysozyme makes them more susceptible to proteolytic degradation. Sixth, exogenous proteases, when in the intestines, may participate in final steps of food-protein digestion. The resulting food-borne peptides have recently been shown to be potential activators of microbial autolysis. The main question that needs to be answered in order to verify the hypothesis is whether oral proteases are able (and to what extent) to lyse/mediate lysis of intestinal microorganisms in situ. Methods based on up-to-date molecular biology techniques to allow investigation of the influence of exogenous proteases on microbial lysis processes in vivo (in the intestines) need to be developed. Research testing of this hypothesis may have an important impact in development of novel preparations for the systemic enzyme therapy.

Non-specific immunity-enhancing effects of tryptic casein hydrolysate versus Fermosorb for treatment/prophylaxis of newborn calf colibacillosis

The effects of treatment/prophylaxis of newborn calf colibacillosis with tryptic casein hydrolysate (TCH), recently shown to be a novel type of antimicrobial acting through stimulation of the microbial autolytic system, versus an authorized veterinary drug, Fermosorb, were evaluated. Both products showed similar high therapeutic and prophylactic efficacies, but hematological indices and daily weight gain of cured/protected animals were better with TCH. The differences in hemoglobin and hematocrit levels, total protein, gamma-globulin and sulfhydryl group quantities, bactericidal and lysozyme activities as well as daily weight gain at the end of treatment/prophylaxis were statistically significant (P<0.05-0.000005). Statistically significant differences (P<0.05-0.0005) in favor of TCH were also observed when bactericidal activity, total protein quantity of serum as well as daily weight gain of the animals were compared on the 90th day after birth. We conclude that TCH acts not only as an antimicrobial, but also as an immunostimulant (and growth promoter). The immunostimulatory activity of TCH most probably derives from a synergistic action of bioactive peptides encrypted in the preparation itself and the cell wall fragments resulting from microbial autolysis induction.

Comparative studies on Polyferm and Fermosorb, two oral (ferment + sorbent) - type preparations designed for therapy/prophylaxis of intestinal infections in animal neonates

Polyferm and Fermosorb are oral acid resistant antimicrobial enzyme preparations designed specifically for therapy/prophylaxis of intestinal infections in animal neonates. Both are authorized for use throughout the former Soviet Union, but until now only Fermosorb is being applied on a large scale. The comparative studies on these two preparations, described in this paper, were carried out in order to find differences between the preparations. Characteristics that were compared included stability of the preparations in acidic environment as well as in storage (in vitro studies), and their efficacy for the treatment and prophylaxis of colibacillosis in newborn calves (in vivo studies). Results of in vitro studies revealed that proteolytic enzymes of Polyferm (as well as lytic enzymes of Fermosorb) were suitably (and in a very similar magnitude) protected from the influence of the acidic environment. The complete enzyme activity retention period in storage at room temperature of Polyferm and Fermosorb was equally high (5 years). In vivo studies performed on 2000 calves revealed that both preparations were highly effective and, although the efficacy of Polyferm was a bit lower than that of Fermosorb (93.6% vs. 95.0%, 94.6% vs. 95.8% for therapy and prophylaxis of colibacillosis, respectively), no statistically significant differences in the number of Polyferm vs. Fermosorb cured/protected animals were found. It is concluded that there were no reasons, other than the lack of supportive advertising materials, that might impede the utility of Polyferm.

Immunomodulatory properties of Nocardia lysozyme digest (NLD) in complement normal and C5-deficient mice

The constantly increasing number of substances with adjuvant activity outpaces the elucidation of their mode of action. This problem is of great importance as the immunomodulatory action of an adjuvant is time- and route-dependent, which implies that administration at a different moment or site may result in a reduced immune response. In the present work the possibility to achieve dual effect (stimulatory or inhibitory) is regarded in the light of the complement system. The object of the study is a preparation obtained by lysozyme digestion of Nocardia opaca cell walls (NLD). According to the results, the administration of NLD to mice (i.p. at a daily dose of 0.5 mg kg-1) during 3 days prior to the antigen resulted in an inhibition of serum antibody level against sheep red blood cells (SRBC) and lipopolysaccharide (LPS). At the same time, the preparation stimulated the antibody response to SRBC if it was applied after the antigen. The ability of NLD to ensure protection against experimental infection with Klebsiella pneumoniae was comparatively studied in complement-normal mice (strain ICR) and in C5-deficient mice (strain DBA/2). Firstly, it was established that complement-deficient mice were more resistant to infection than complement-normal. Secondly, the preparation expressed a protective effect in C5-deficient animals; nevertheless the inoculation was done s.c. or i.v. The departure of the infection depended on the rate of opsonization of K. pneumoniae. Under certain conditions NLD can provoke excessive C3 activation, which might aggravate the course of the infection. The preparation augmented the host response to second challenge with K. pneumoniae of complement-normal and C5-deficient mice.

Occurrence and specificity of human natural and in vitro induced antibodies to Nocardia opaca antigens

Nocardia opaca, a Gram-positive bacterium, is a potent source of immunostimulatory substances. Screening of sera of adult human donors revealed that all sera tested contained antibodies reactive with isolated Nocardia fractions (Nocardia delipidated cell mitogen, NDCM; Nocardia lysozyme digest, NLD; Nocardia water-soluble mitogen, NWSM; and fraction B). The respective values of reciprocal titres for IgM and IgG were in the range of 100 to 12,800, and 10 to 320 for IgA antibody isotypes, when NLD or fraction B were used as antigens in enzyme-linked immunosorbent assay (ELISA) tests. The level of antibodies directed to NDCM, a potent polyclonal B cell activator, was found to be the lowest. In vitro spontaneous as well as NDCM-induced production of antibodies to NDCM by human peripheral blood lymphocytes involved mainly the IgM class. Western-blot analysis demonstrated that antibodies in normal human sera react with nocardial antigens of molecular mass approximately 60, 40, 20 and 15-10 kDa. The same antigens were also recognized by rabbit and mouse hyperimmune sera, also confirming the immundominancy of these nocardial antigens in other species. The presence of anti-nocardia antibodies in human sera and their production by both stimulated and non-stimulated lymphocytes points to the natural sensitization of humans either by ubiquitous no-cardial components or by cross-reactive bacterial or food antigens.

Correlation between inhibited alternative complement activity and the protective effect induced by Nocardia lysozyme digest (NLD) during Klebsiella pneumoniae infection in mice

Nocardia lysozyme digest (NLD) was administered intraperitoneally (i.p.) at a dose of 500 micrograms/kg to normal and immunosuppressed mice for 3 consecutive days prior to inoculation with Klebsiella pneumoniae. A protective effect was observed when the pathogen was injected subcutaneously and intravenously, as opposed to an aggravating effect obtained in the case of intraperitoneal inoculation The i.p. administration of NLD partially restored the immunosuppression caused by cyclophosphamide but did not change cobra venom-induced deterioration of the infection. The results obtained could be regarded as a consequence of the lowered alternative pathway serum complement activity and the crucial role of the diminished level of complement in the peritoneal cavity.