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

Salmonella infections: immune and non-immune protection with vaccines

Salmonella enterica in poultry remains a major political issue. S. enterica serovar Enteritidis, particularly, remains a world-wide problem. Control in poultry by immunity, whether acquired or innate, is a possible means of containing the problem. Widespread usage of antibiotics has led to the emergence of multiple antibiotic-resistant bacteria. This problem has indicated an increasing requirement for effective vaccines to control this important zoonotic infection. An attempt is made in the present review to explain the relatively poor success in immunizing food animals against these non-host-specific Salmonella serotypes that usually produce food-poisoning, compared with the success obtained with the small number of serotypes that more typically produce systemic "typhoid-like" diseases. New examinations of old problems such as the carrier state and vertical transmission, observed with S. Pullorum, is generating new information of relevance to immunity. Newer methods of attenuation are being developed. Live vaccines, if administered orally, demonstrate non-specific and rapid protection against infection that is of biological and practical interest. However, from the point of view of consumer safety, there is a school of thought that considers inactivated or sub-unit vaccines to be the safest. The benefits of developing effective killed or sub-unit vaccines over the use of live vaccines are enormous. Recently, there have been significant advances in the development of adjuvants (e.g. microspheres) that are capable of potent immuno-stimulation, targeting different arms of the immune system. The exploitation of such technology in conjunction with the ongoing developments in identifying key Salmonella virulence determinants should form the next generation of Salmonella sub-unit vaccines for the control of this important group of pathogens. There are additional areas of concern associated with the use of live vaccines, particularly if these are generated by genetic manipulation.

Rapid protection of gnotobiotic pigs against experimental salmonellosis following induction of polymorphonuclear leukocytes by avirulent Salmonella enterica

Oral inoculation of 5-day-old gnotobiotic pigs with Salmonella enterica serovar Typhimurium strain F98 resulted in severe enteritis and invasive disease. Preinoculation 24 h earlier with an avirulent mutant of Salmonella enterica serovar Infantis (1326/28) completely prevented disease for up to 14 days (when the experiment was terminated). S. enterica serovar Infantis colonized the alimentary tract well, with high bacterial counts in the intestinal lumen but with almost no invasion into the tissues. Unprotected pigs had high S. enterica serovar Typhimurium counts in the intestines, blood, and major nonintestinal organs. Recovery of this strain from the blood and major organs in S. enterica serovar Infantis-protected pigs was substantially reduced despite the fact that intestinal counts were also very high. Protection against disease thus did not involve a colonization exclusion phenomenon. Significant (P < 0.05) infiltration of monocytes/macrophages was observed in the submucosal regions of the intestines of both S. enterica serovar Infantis-protected S. enterica serovar Typhimurium-challenged pigs and unprotected S. enterica serovar Typhimurium-challenged pigs. However, only polymorphonuclear neutrophils (PMNs) were observed throughout the villus, where significant (P < 0.05) numbers infiltrated the lamina propria and the subnuclear and supranuclear regions of the epithelia, indicating that PMN induction and positioning following S. enterica serovar Infantis inoculation was consistent with rapid protection against the challenge strain. Similarly, in vitro experiments using a human fetal intestinal epithelial cell line (INT 407) demonstrated that, although significantly (P < 0.05) fewer S. enterica serovar Infantis than S. enterica serovar Typhimurium organisms invaded the monolayers, S. enterica serovar Infantis induced an NF-kappaB response and significantly (P < 0.05) raised interleukin 8 levels and transmigration of porcine PMN. The results of this study suggest that attenuated Salmonella strains can protect the immature intestine against clinical salmonellosis by PMN induction. They also demonstrate that PMN induction is not necessarily associated with clinical symptoms and/or intestinal pathology.

Effect of an immunomodulating agent, RU 414740, on polymorphonuclear responsiveness after burn injury

An impairment of polymorphonuclear leukocyte (PMN) functions has been described following burn trauma. It was thus of interest to investigate the effect of RU 41740, an agent known to stimulate these cells, on rat PMN functions after burn injury. In the present study the responsiveness to classical stimuli of PMN from untreated burned rats was approximately 40% lower than healthy control values. In vitro treatment with RU 41740 increased oxidative metabolism of PMNs from burned and healthy rats. The effect was dose-related but was most striking in the case of PMNs from healthy rats. Significant differences were obtained with concentrations higher than 1 micrograms/ml for healthy rats but only 10 micrograms/ml for burned rats. In vivo treatment with RU 41740 also led to an enhancement of PMN oxidative metabolism on both burned and healthy rats. The maximal effective dose was 10 mg/kg/day in both cases. In contrast, 25 and 50 mg/kg/day doses inhibited PMN oxidative metabolism.

Increased expression of C3b and C3bi receptors on human neutrophils and monocytes induced by a glycoprotein extract from Klebsiella pneumoniae (RU41740)

RU41740 is a glycoprotein extract from Klebsiella pneumoniae with immunomodulating properties under different experimental conditions. In particular the compound is able to stimulate several functions of human phagocytes in vitro and ex vivo. Using monoclonal antibodies and flow cytometry, in this work we assessed the effect of RU41740 on surface expression of receptors for C3b (CR1) and C3bi (CR3) in human phagocytic cells in vitro. The incubation of whole blood with varying RU41740 concentrations led to a dose-dependent increase in surface expression of CR1 and CR3 on both neutrophils and monocytes when compared with control samples incubated in buffer alone. The maximal drug-induced enhancement of complement receptors was: 291% +/- 13.4% for CR1 and 265% +/- 8.5% for CR3 in neutrophils; 117% +/- 4.5% for CR1 and 98% +/- 4.1% for CR3 in monocytes. These peak effects were observed using RU41740 at a final concentration of 10 micrograms/ml and were similar to those induced by optimal concentrations of the activating compound N-formyl-methionyl-leucyl-phenylalanine (10(-7)M). Polymyxin B did not modify the RU41740-induced enhancement of CR1 and CR3 expression on phagocytes, suggesting no role for endotoxin in this activity. These results define, at least in part, the mechanism of action of RU41740 on human phagocytes in vitro and could be relevant to in vivo events during RU41740 treatment.

In vitro and in vivo effects produced by the immunomodulating agent RU 41740 on human polymorphonuclear leukocytes in the elderly

The activity of RU 41740, a glycoprotein extract from Klebsiella pneumoniae has been investigated on some polymorphonuclear (PMN) functions. Chemotaxis, random migration and oxidative metabolism (assessed by chemiluminescence, O2 consumption and O2- generation) were studied in parallel. PMN were collected from adult and aged human volunteers. Experiments were performed either in vitro or in vivo in a double blind placebo assay. In both PMN populations RU 41740 enhanced oxidative metabolism either in in vivo or in vitro experiments. However, a higher and dose-related activity was observed on PMN collected from the younger subjects whereas maximal effective concentration was reached earlier with PMN collected from aged subjects. RU 41740 did not modify random migration but inhibited chemotaxis of PMN collected from the younger population in a dose-related manner. These data corroborated previous results observed on PMN collected from various animal species and suggested an interaction of RU 41740 on PMN membrane. Moreover drug-induced macrophage and lymphocyte stimulation might also explain, at least in part, the in vivo effects described in this study. Thus RU 41740 could partly account for the protective effects exerted against bacterial and fungal infections through its activity on PMN functions.

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 and ex vivo effect of RU41740 on human polymorphonuclear leukocyte function

We investigated the effect of RU41740, a glycoprotein extracted from Klebsiella pneumoniae and possessing immunomodulating properties, on human neutrophil functions in vitro and ex vivo. Our in vitro results showed that RU41740 increased complement- and Fc receptor-dependent phagocytosis. Moreover, the drug enhanced the oxidative metabolism (assessed by chemiluminescence) both in resting and stimulated cells; in the latter case the RU41740-induced enhancement was observed when neutrophils were stimulated with opsonized particles of N-formyl-methionyl-leucyl-phenylalanine (FMLP) but not when phorbol myristate acetate was used. Using otherwise effective experimental conditions, RU41740 did not affect spontaneous or FMLP-induced neutrophil migration. For the ex vivo experience we tested neutrophils of ten elderly subjects with a previously demonstrated phagocytic defect. These subjects were treated orally with RU41740 at a daily dose of 2 mg for 1 week during the first month, and of 1 mg for 1 week in the second month. In this population, RU41740 was able to restore the impaired phagocytic activity and to induce a significant increase of spontaneous chemiluminescence (CL); stimulated CL was also positively influenced. These effects on neutrophils provide new explanatory bases for the immunostimulatory activity of RU41740.