Oral administration of a bacterial immunomodulator enhances murine intestinal lamina propria and Peyer's patch lymphocyte traffic to the lung: possible implications for infectious disease prophylaxis and therapy

Prevention of New Respiratory Episodes in Children with Recurrent Respiratory Infections: An Expert Consensus Statement

In healthy infants and young children, the development of respiratory tract infections (RTIs) is extremely common. In this paper, we present an international consensus of the available approaches for the prevention of recurrent RTIs in children, including the atopic/allergic ones as well as those with asthma. Few convincing measures for reducing the frequency and clinical relevance of recurrent respiratory episodes in RTI-prone children have been developed until now. Among the most recently suggested measures, immunotherapy is attractive, but only for OM-85 is there a sufficient number of well-conducted clinical trials confirming efficacy in RTIs prevention with an adequate safety profile. In the case of probiotics, it is not clear which bacteria can offer the best results and which dosage and schedule of administration are the most effective. The problems of dosage and the schedule of administration are not solved also for vitamin D, despite some promising efficacy results. While we wait for new knowledge, the elimination or reduction as much as possible of the environmental factors that favor RTIs, vaccination when available and/or indicated, and the systematic application of the traditional methods for infection prevention, such as hand washing, remain the best measures to prevent recurrent infections in RTI-prone children.

Viral infections and wheezing-asthma inception in childhood: is there a role for immunomodulation by oral bacterial lysates?

Severe and recurrent infections of the respiratory tract in early childhood constitute major risk factors for the development of bronchial hyper-responsiveness and obstructive respiratory diseases in later life. In the first years of life, the vast majority of respiratory tract infections (RTI) leading to wheezing and asthma are of a viral origin and severity and recurrence are the consequence of a greater exposure to infectious agents in a period when the immune system is still relatively immature. Therefore, boosting the efficiency of the host immune response against viral infections seems to be a rational preventative approach. In the last decades it has been demonstrated that living in farm environments, i.e. early-life exposure to microbes, may reduce the risk of allergic and infectious disorders, increasing the immune response efficacy. These findings have suggested that treatment with bacterial lysates could promote a nonspecific immunomodulation useful in the prevention of recurrent RTIs and of wheezing inception and persistence. Experimental and clinical studies showing the reduction of RTI frequency and severity in childhood and elucidating the involved mechanisms can support this hypothesis.

Effect of the Lactococcus Lactis 11/19-B1 Strain on Atopic Dermatitis in a Clinical Test and Mouse Model

Some lactic acid bacteria (LAB) are known to improve atopic dermatitis (AD) through the regulation and stimulation of the host immune system. In this study, we found that ingestion of yogurt containing Lactococcus lactis 11/19-B1 strain (L. lactis 11/19-B1) daily for 8 weeks significantly improved the severity scoring of atopic dermatitis (SCORAD) system score from 38.8 ± 14.4 to 24.2 ± 12.0 in children suffering from AD. We tried to identify which LAB species among the five species contained in the test yogurt contributed to the improvement in AD pathology using an AD mouse model induced by repeated application of 1-fluoro-2, 4-dinitrobenzene (DNFB). AD-like skin lesions on the dorsal skin and ear were most improved by L. lactis 11/19-B1 intake among the five LAB species. In addition, analysis of CD4+ T cell subsets in Peyer’s patches (PPs) and cervical lymph nodes (CLNs) indicated that the intake of L. lactis 11/19-B1 generally suppressed all subsets related to inflammation, i.e., Th1, Th2 and Th17, instead of activating the suppressive system, Treg, in the AD mouse model. Histological observations showed ingestion of L. lactis 11/19-B1 significantly suppressed severe inflammatory findings, such as inflammatory cell filtration, epidermal erosion and eosinophil infiltration. These results suggest that the immunomodulatory effects of L. lactis 11/19-B1 contribute to improvements in AD pathology.

Oral ingestion of lactic-acid bacteria by rats increases lymphocyte proliferation and interferon-γ production

The effect of feeding lactic-acid bacteria on indices of functions of lymphocytes obtained from Peyer's patches, peripheral blood and spleen from inbred Wistar-Furth rats were studied. Rats were fed on purified diets supplemented with 350 g milk or yoghurt/kg diet for 4 weeks. At the end of the feeding period, immune cells from the three sites were isolated and proliferation, interferon-γ production and lymphocyte subset composition were studied. Rats consuming yoghurt had a greater in vitro proliferative response to yoghurt bacteria in the three lymphoid compartments, a greater interferon-γ production in response to bacteria and concanavalin A in Peyer's patches and spleen, and a greater number of Peyer's patches B lymphocytes than milk-fed rats. Macrophage and T lymphocyte proportions and lymphocyte subset composition in the three sites were unaffected by yoghurt. These results indicate that feeding live bacteria contained in yoghurt may interact with the intestinal immune system, and influence the systemic immune system.

Efficacy of a polyvalent bacterial lysate in children with recurrent respiratory tract infections

Respiratory tract infections (RTIs) are the most frequent infections in humans, particularly in children. In addition to intervention, increasing interest is focusing on immunomodulatory therapy for recurrent RTIs, which indicate a reduced defense capacity of the respiratory mucosa. LW 50020, an oral immunomodulator that contains the antigens of seven bacteria common in RTIs, has reduced the number, duration, and severity of RTIs in children and adults. This 56-week placebo-controlled, double-blind study in 188 children investigated whether the efficacy of the standard schedule (immunization cycle + one booster cycle) would be enhanced by additional booster cycles. Efficacy and safety over the long term were also assessed. The rate of infection was reduced by 50% with the standard schedule and could not be further decreased by two consecutive booster cycles. With both schedules, this reduction was sustained during a 28-week treatment-free observation period that followed the 28-week treatment period. The number of adverse drug reactions was low, and all were transient, expected, and nonserious. These results confirm that LW 50020 is an effective and safe strategy for RTIs.

Treatment of recurrent respiratory tract infections with a polyvalent bacterial lysate: results of an open, prospective, multinational study

This multicenter, open study, carried out in 14 countries in Europe, Latin America, and Asia, recruited 4965 patients suffering from recurrent respiratory tract infections to investigate the safety and acceptability of the oral bacterial lysate immunomodulator LW 50020. Patients remained in the study for 4 months (two 4-week courses of LW 50020 separated by a 28-day treatment-free interval and follow-up). The incidence of all adverse events was 7.2%; that of adverse drug reactions was 0.6%. Adverse drug reactions were mild to moderate and not more frequent in the large subgroup of patients (77%) with a known history of allergies or underlying respiratory diseases; however, the incidence of adverse events in this subgroup was twofold higher than in the study population as a whole, probably indicating a generally increased vulnerability to disease. No clinically relevant changes in laboratory variables followed treatment. Comparison of the first study period (first course of LW 50020 and drug-free interval) with the second study period (second course of LW 50020 and follow-up) showed an overall reduction of at least 50% in the number, severity, and duration of respiratory tract infections, the number of antibiotic and symptomatic treatments, and the number of days absent from school or work. Tolerability and acceptability were assessed as good or very good in 99% of patients who completed the study.

An experimental prime-boost regimen leading to HIV type 1-specific mucosal and systemic immunity in BALB/c mice

Induction of mucosal as well as systemic immunity to HIV-1 is considered to have high priority in current concepts of future AIDS vaccines. Here we show that the desired immune responses can be elicited by an experimental prime-boost regimen consisting of mucosal (intragastric) application of a recombinant vaccinia virus carrying the HIV-1 env gene (vSC25), followed by parenteral (intradermal) immunization with the recombinant HIV-1 glycoprotein 160 (rgp160). Following intragastric immunization of mice with vSC25 in combination with the mucosal adjuvant cholera toxin (CT), HIV-1 env-specific IgA was secreted by B cells of Peyer's patches and the lamina propria. Moreover, mucosal (intragastric and intranasal) application of vSC25 (both in presence or absence of CT) induced a long-lasting, HIV-1 env-specific systemic cytotoxic T cell response. Subsequent intradermal boosters with rgp160 led to HIV-1-specific T cell memory and serum antibodies.

Larynx-associated lymphoid tissue (LALT) in young children

BACKGROUND

Mucosa-associated lymphoid tissue (MALT) plays a central role in mucosal immunity. Whereas the characteristics and function of MALT in the intestine are well established, almost nothing is known about MALT in the larynx.

METHODS

In this study we examined the morphology and the lymphocyte subset composition of MALT in the larynges of children who had died of sudden infant death or various defined traumatic or nontraumatic causes.

RESULTS

Organized lymphoid tissue was found in the supraglottic parts of the larynx in nearly 80% of the children in both groups. This lymphoid tissue showed all morphological signs of MALT, such as typical lymphoid follicles with germinal centers, infiltration of the overlying epithelium by lymphocytes, and high endothelial venules (HEV). Thus we will use the term LALT (larynx-associated lymphoid tissue) to refer to this tissue. The lymphoid follicles of LALT contained mainly B lymphocytes with some CD4+ lymphocytes in the germinal centers. Remarkably, T lymphocytes of both subset types and B lymphocytes were observed in comparable numbers in the parafollicular area.

CONCLUSIONS

We assume that LALT is a physiological structure of the larynx in young children. The morphology and the distribution of lymphocyte subsets are similar to those of MALT in the human gut. LALT may be a regular part of the mucosal immune system in young children with the role of respiratory inductive site for mucosal immunity.

Stimulating effect of an oral polybacterial immunomodulator on the proliferative activity of guinea pig lymphocytes

A preparation for the prophylaxis and treatment of inflammations of oral mucosa and parodont Dentavax (D) was investigated in guinea pigs. Animals were given orally D for 5 consecutive days and a month later the procedure was repeated. On day 3, 10, 21, and 28 after immunization and reimmunization lymphoproliferative responses to PHA, rIL-2, LPS and D were measured by the radiometric blast transformation assay in peripheral blood, spleen, mesenteric lymph nodes (MLN) and Peyer's patches (PP). The percentage of cells entering S and G2/M-phases of cell cycle was assessed by the flow cytometric DNA analysis. A correlation in proliferative activity of cells after in vitro stimulation with PHA and LPS has been established by both methods. Peak values of lymphocyte stimulation were found on day 10, especially after the second administration of D in all organs tested, mainly in MLNs and spleen. Electron-microscopic studies demonstrated an extensive development of the endoplasmatic reticulum in plasmatic cells from spleen, PPs, mesenteric, bronchial and inguinal lymph nodes. The results obtained may be considered a proof of the immunostimulating effect of Dentavax.

The use of the lipophilic fluorochrome CM-DiI for tracking the migration of lymphocytes

In this study we examined the new cell dye CM-DiI for tracking the migration of lymphocytes from blood to lymph. This lipophilic marker intercalates in the plasma membrane like the PKH dyes and older DiI derivatives. The stability and intensity of staining achieved with these dyes is better than most other fluorochromes or radioisotopes, yet they are poorly soluble in aqueous solutions, which can make staining difficult, and they are not fixable in tissue sections. CM-DiI is reported to have increased water solubility and it can be fixed using traditional aldehyde fixatives, making it feasible to detect labeled cells in histological sections. To determine the suitability of CM-DiI as a lymphocyte marker, a labeling protocol was developed. We tested the ability of stained cells to recirculate in vivo. Following the intravenous injection of CM-DiI positive cells, their recovery in lymph over 40 h was comparable to that of cells labeled with other fluorochromes or radioisotopes. The kinetics of recirculation were also very similar, as labeled cells were detectable in lymph within 4 h of injection, and the peak percentage of labeled cells in lymph was generally observed between 20-30 h. We also confirmed that CM-DiI is retained in the lymphocyte membrane following routine paraffin processing. Thus CM-DiI does not appear to alter the process of lymphocyte recirculation, and it should be a useful marker for tracking these cells.

Preparation and characterization of poly-(D,L-lactide-co-glycolide) and poly-(L-lactic acid) microspheres with entrapped pneumotropic bacterial antigens

Poly-(lactide-co-glycolide) microspheres with entrapped antigen have shown considerable promise as controlled release vaccines. To enhance the immunomodulatory effect of LW 50020, a bacterial lysate of seven common respiratory pathogens used perorally as an immunomodulator, we prepared poly-(D,L-lactide-co-glycolide) (PLG) and poly-(L-lactic acid) (PLA) microspheres with entrapped immunomodulator by solvent evaporation or solvent extraction double emulsion techniques. Physical properties, such as particle size, LW 50020 entrapment rate, antigen release patterns and morphological characteristics were investigated. All preparations displayed a high degree of antigen loading up to 95%, whereas size, surface morphology and antigen release patterns were significantly influenced by the method of preparation and the polymer components used. Solvent evaporation microspheres are porous particles from 0.8 micron to 2.0 microns in diameter, that show a rapid antigen release for PLG, and a moderate antigen release for PLA microspheres within 33 days. Solvent extraction microspheres have proven to be particles from 1.1 microns to 5.0 microns in diameter showing a smooth surface and a medium antigen release rate over 33 days. SDS-PAGE and immunoblotting of extracted antigen confirmed that the molecular weight and antigenicity of the immunomodulator remained unaltered by the entrapment procedure.

Enhancement of anti-Shigella lipopolysaccharide (LPS) response by addition of the cholera toxin B subunit to oral and intranasal proteosome-Shigella flexneri 2a LPS vaccines

Addition of the cholera toxin B subunit to oral and intranasal proteosome-Shigella flexneri 2a lipopolysaccharide vaccines improved their immunogenicities. Enhancement of anti-O-Shigella immunoglobulin A levels was most evident in lung lavages following oral immunization and in lung and intestinal fluids when suboptimal doses were used with either immunization route.

A novel and sensitive method for the detection of secreted cell products using time-resolved fluorescence

A new test has been developed for the quantitative detection of products secreted from isolated cells, based on the use of lanthanide- rather than enzyme-linked streptavidin. Used as a label, europium (Eu3+) can be measured with high sensitivity by time-resolved fluorescence. The main advantages of this assay are both an increased sensitivity and measuring range of cell released substances, when compared to the standard "wet" ELISA. Thus, the immunoglobulin secretion rate of 10(5) splenocytes could be easily measured by time-resolved fluoroimmunoassay (TR-FIA), while it remained below the detection limit of the 'wet' ELISA. In contrast to the classical ELISPOT test, this assay does not detect single antibody secreting cells (ASC), but would be useful for precise quantification of secreted cell products, such as immunoglobulins, cytokines, growth factors.

Protective effects of orally administered, Klebsiella-containing bacterial lysates in mice

The efficacy, as oral vaccines, of hepta- and mono-valent, Klebsiella-containing bacterial lysates and a number of control preparations was tested in mice. The preparations were administered during two periods of four days each, interrupted by an interval of 3 days. Fourteen days after the first dose, the animals were challenged either intraperitoneally (i.p.; peritonitis/sepsis model) or intranasally (i.n.; pneumonia model). Animals treated with low doses of Klebsiella lysate, in the form of either a 7-valent lysate or a Klebsiella monolysate, showed enhanced survival in both the peritonitis/sepsis and the pneumonia models. Hexa- and tetra-valent preparations without Klebsiella were not protective in the models tested. Furthermore, it was found that the protection is accompanied by priming for Klebsiella-specific IgG responsiveness (probably at the T cell level) and by significant IgA anti-Klebsiella serum antibody levels in about one third of the animals. The oral efficacy of Klebsiella-containing lysates suggests the presence of an adjacent component that directs Klebsiella antigen(s) to follow a selective intestinal pathway which renders them immunogenic. The identity of this component is under investigation.