Effect of a modified terrilytin on ampicillin pharmacokinetics in experimental peritonitis

The effect of modified terrilytin, a new enzyme of the microbial origin on the pharmacokinetics of ampicillin in experimental peritonitis was studied on 16 pubertal rabbits. Peritonitis was caused by laparotomy and administration of a 15 per cent fecal suspension into the abdominal cavity. The drugs were injected intramuscularly: the enzyme in a dose of 5 PU/kg and the antibiotic in a dose of 10 mg/kg. The ampicillin levels in the blood and peritoneal exudate were determined with the agar-diffusion method. The specimens were collected 30 minutes, 1, 1.5 and 2 hours after administration of the drugs. The animals were divided into 2 groups: control (not treated with the enzyme) and experimental. An increase in the antibiotic levels in the blood and peritoneal exudate by 50--54 per cent was observed. The maximum increase was recorded 30 minutes after simultaneous administration of the drugs.     

The number of immunologically activated cells after repeated immunization (A mathematical model)

Using a mathematical model, the effect of the dose of antigen and of the rate of its elimination on the number of immunologically activated cells, derived from a single immunocompetent cell, that are prepared for the change into antibody-producing cells under the condition that further antigenic stimulus takes place, was studied. The following results were obtained under certain assumptions that are explained and discussed in our present work: (1) The shape of the dependence of the number of immunologically activated cells afterk-fold immunization on the immunizing dose and the rate of elimination of antigen was established. (2) In studies on the influence of the magnitude of a single antigen dose on the readiness for the secondary reaction (expressed as the number of immunologically activated cells present at the time of injection of the secondary antigen dose), we found that with increasing antigen dose the number of immunologically activated cells increases until it reaches its peak at the optimum antigen dose; then a decrease starts to occur. The range of doses of antigen causing approximately similar (and high) readiness for the secondary response is broader with antigens that are eliminated faster from the organism. (3) A method for the estimation of the optimum dose of antigen and of the number of persisting immunologically activated cells after this antigen dose is presented. This method can be used provided certain knowledge concerning the particular experimental system is available.     

Treatment of anthrax infection with combination of ciprofloxacin and antibodies to protective antigen of Bacillus anthracis

Currently there is no effective treatment for inhalational anthrax beyond administration of antibiotics shortly after exposure. There is need for new, safe and effective treatments to supplement traditional antibiotic therapy. Our study was based on the premise that simultaneous inhibition of lethal toxin action with antibodies and blocking of bacterial growth by antibiotics will be beneficial for the treatment of anthrax. In this study, we tested the effects of a combination treatment using purified rabbit or sheep anti-protective antigen (PA) antibodies and the antibiotic ciprofloxacin in a rodent anthrax model. In mice infected with a dose of Bacillus anthracis Sterne strain corresponding to 10 LD(50), antibiotic treatment with ciprofloxacin alone only cured 50% of infected animals. Administration of anti-PA IgG in combination with ciprofloxacin produced 90-100% survival. These data indicate that a combination of antibiotic/immunoglobulin therapy is more effective than antibiotic treatment alone in a rodent anthrax model.     

Pharmacokinetics and pharmacodynamics of DSTA4637A: A novel THIOMAB™ antibody antibiotic conjugate against Staphylococcus aureus in mice

DSTA4637A, a novel THIOMAB? antibody antibiotic conjugate (TAC) against Staphylococcus aureus (S. aureus), is currently being investigated as a potential therapy against S. aureus infections. Structurally, TAC is composed of an anti-S. aureus antibody linked to a potent antibiotic, dmDNA31. The goal of the current study was to characterize the pharmacokinetics (PK) of TAC in mice, assess the effect of S. aureus infection on its PK, and evaluate its pharmacodynamics (PD) by measuring the bacterial load in various organs at different timepoints following TAC treatment. Plasma concentrations of 3 analytes, total antibody (TAb), antibody-conjugated dmDNA31 (ac-dmDNA31), and unconjugated dmDNA31, were measured in these studies. In non-infected mice (target antigen absent), following intravenous (IV) administration of a single dose of TAC, systemic concentration-time profiles of both TAb and ac-dmDNA31 were bi-exponential and characterized by a short distribution phase and a long elimination phase as expected for a monoclonal antibody-based therapeutic. Systemic exposures of both TAb and ac-dmDNA31 were dose proportional over the dose range tested (5 to 50 mg/kg). In a mouse model of systemic S. aureus infection (target antigen present), a single IV dose of TAC demonstrated PK behavior similar to that in the non-infected mice, and substantially reduced bacterial load in the heart, kidney, and bones on 7 and 14 d post dosing. These findings have increased our understanding of the PK and PK/PD of this novel molecule, and have shown that at efficacious dose levels the presence of S. aureus infection had minimal effect on TAC PK.     

The effect of Bordetella pertussis lymphocytosis-promoting factor (LPF) on antibody response in mice: its enhancing and suppressive effects

The effect of lymphocytosis-promoting factor (LPF) on antibody response in mice was estimated under different sets of experimental conditions. Four- and 6-week-old mice were intravenously inoculated with LPF. Three days later these mice were inoculated either intraperitoneally or intravenously with sheep red blood cell (SRBC) or human serum albumin (HSA) as an antigen. The adjuvant effect of LPF was demonstrated on antibody response in 6-week old mice to intraperitoneally inoculated SRBC but not to intravenously-inoculated one. When 4-week-old mice were immunized, hemagglutinin production in response to intraperitoneally inoculated SRBC was not enhanced by LPF. In addition, a rather suppressive effect of LPF at a comparatively high dose was demonstrated on hemagglutinin production in response to intravenously inoculated SRBC. Anti-HSA production was enhanced by inoculation of LPF in any combination of the mouse age and the route of antigen administration. These findings indicate that the adjuvant effect of LPF on antibody response in mice depends upon experimental conditions: the age of mice, the quality of antigen and the route of antigen administration used for immunization.     

Antibiotic growth promoter olaquindox increases pathogen susceptibility in fish by inducing gut microbiota dysbiosis

Low dose antibiotics have been used as growth promoters in livestock and fish. The use of antibiotics has been associated with reduced pathogen infections in livestock. In contrast, antibiotic growth promoter has been suspected of leading to disease outbreaks in aquaculture. However, this phenomenon is circumstantial and has not been confirmed in experimental conditions. In this study,we showed that antibiotic olaquindox increased the susceptibility of zebrafish to A. hydrophila infection. Olaquindox led to profound alterations in the intestinal microbiota of zebrafish, with a drastic bloom of Enterobacter and diminishing of Cetobacterium. Moreover, the innate immune responses of zebrafish were compromised by olaquindox(P0.05). Transfer of microbiota to GF zebrafish indicated that while the immuo-suppression effect of olaquindox is a combined effect mediated by both OLA-altered micro biota and direct action of the antibiotic(P0.05), the increased pathogen susceptibility was driven by the OLA-altered microbiota and was not dependent on direct antibiotic effect. Taken together, these data indicate that low level of OLA induced gut microbiota dysbiosis in zebrafish, which led to increased pathogen susceptibility.     

Performance and caecal adaptation of turkeys to diets without or with antibiotic and with different levels of mannan-oligosaccharide

A study on turkeys was conducted to evaluate the administration of different levels of mannan-oligosaccharide (MOS) (0.1, 0.25 and 0.5%) to a diet without or with an antibiotic (Flavomycin, 8?mg/kg feed). The growth performance as well as caecal development and metabolism indicators of turkeys after 8 weeks of experimental feeding were estimated. No interactions were noted between the contents of antibiotic and MOS in the diet in any of the parameters examined. During 8 weeks of experimental feeding, the feed intake as well as feed conversion ratio were similar in all experimental groups. The turkeys fed a control diet (without MOS) supplemented with antibiotic were the heaviest, but there were no statistical differences between groups. Depending on dietary dose, MOS had a different influence on caecal digesta parameters. The medium level of dietary MOS (0.25%) resulted in the highest caecal pH, dry matter and protein concentrations as well as the bacterial glycolytic activity (including β-glucuronidase). Compared to other dietary treatments, the highest amount of MOS (0.5%) reduced ammonia concentration and enhanced volatile fatty acids concentration, especially of acetate and butyrate, in the caecal digesta. The medium level of dietary MOS caused a significant enhancement of propionate, iso-butyrate and iso-valerate concentrations in the digesta. The antibiotic addition to a diet resulted in a lack of birds' response.     

Performance and caecal adaptation of turkeys to diets without or with antibiotic and with different levels of mannan-oligosaccharide

A study on turkeys was conducted to evaluate the administration of different levels of mannan-oligosaccharide (MOS) (0.1, 0.25 and 0.5%) to a diet without or with an antibiotic (Flavomycin, 8 mg/kg feed). The growth performance as well as caecal development and metabolism indicators of turkeys after 8 weeks of experimental feeding were estimated. No interactions were noted between the contents of antibiotic and MOS in the diet in any of the parameters examined. During 8 weeks of experimental feeding, the feed intake as well as feed conversion ratio were similar in all experimental groups. The turkeys fed a control diet (without MOS) supplemented with antibiotic were the heaviest, but there were no statistical differences between groups. Depending on dietary dose, MOS had a different influence on caecal digesta parameters. The medium level of dietary MOS (0.25%) resulted in the highest caecal pH, dry matter and protein concentrations as well as the bacterial glycolytic activity (including beta-glucuronidase). Compared to other dietary treatments, the highest amount of MOS (0.5%) reduced ammonia concentration and enhanced volatile fatty acids concentration, especially of acetate and butyrate, in the caecal digesta. The medium level of dietary MOS caused a significant enhancement of propionate, iso-butyrate and iso-valerate concentrations in the digesta. The antibiotic addition to a diet resulted in a lack of birds' response.     

Protective action of rifampicin in experimental rabies infection of albino mice

The paper presents the results of the experimental study of the action of rifampicin on the process of rabies infection in albino mice contaminated with 1-10 LD50 of the fixed rabies virus. Exposure to rifampicin in doses of 250 and 500 micrograms/mouse (35-70 mg/kg) resulted in survival of 66.7 and 83.4 per cent of the animals respectively while in the controls it did not exceed 16.6 and 25.0 per cent. The average life-span of the albino mice treated with the antibiotic increased 1.6-2.4-fold in comparison with the controls. The chemotherapeutic index of rifampicin representing the ratio of the maximum tolerance dose to the minimum dose providing the protective action was equal to 20. The protective action was observed either after administration of the antibiotic according to the treatment-and-prophylaxis scheme or after administration of its 2- or 3-fold dose once a day immediately after the contamination.     

Preclinical toxicological study of the new antibiotic eremomycin. Chronic toxicity and effect on intrauterine development of rats

Toxicity of eremomycin was studied after its multiple parenteral administration to albino rats, guinea pigs and dogs in doses equivalent by the body surface to the daily doses for humans i. e. 1 and 3 g. The antibiotic was administered for 1 to 6 months. Tolerance of the antibiotic by the dogs after intravenous and intramuscular administration was satisfactory. In some animals there were observed an insignificant increase in the activity of alanine aminotransferase and a rise in the level of urea in blood serum. Pathomorphological examination of the internal organs of the albino rats and dogs showed that in high doses the antibiotic could have a damaging effect on the kidneys and epithelium of the gastrointestinal tract. The level of the damages depended on the dose of the antibiotic and duration of its use. The damages induced by eremomycin were reversible. It had no marked effect on the peripheral blood count, coagulation system and erythrocyte resistance. In the tested doses the antibiotic had no unfavourable effect on the hearing function in the experiments with guinea pigs. Studies with rats revealed that eremomycin had no teratogenic effect. A slightly pronounced embryotoxic action was observed only after using the antibiotic in doses exceeding more than 12 times the approximate therapeutic dose.     

Surface display of the 20-kDa N-terminal fragment of anthrax protective antigen based on attenuated recombinant <Emphasis Type="Italic">Bacillus anthracis</Emphasis>

Extracellular antigen 1 (EA1), a major component of the Bacillus anthracis surface layer (S-layer), was used as a fusion partner for the expression of heterologous antigen. A recombinant B. anthracis strain was constructed by integrating a translational fusion harboring the DNA fragments encoding the cell wall–targeting domain of the S-layer protein EA1 and the 20-kDa N-terminal fragment of anthrax protective antigen (PA20) into the chromosome. A thermosensitive plasmid expressing Cre recombinase was introduced at a permissive temperature to remove the antibiotic marker. Cre recombinase action at the loxP sites excised the spectinomycin resistance cassette. The final derivative strains were analyzed by sodium dodecyl sulfate–polyacrylamide gel electrophoresis, Western blot analysis, and immunofluorescence analysis. PA20 was successfully expressed on the S-layer of the recombinant antibiotic marker-free strain. Guinea pigs were immunized with the attenuated recombinant B. anthracis strain, and the bacilli elicited a humoral response to PA20. This antibiotic marker-free strain and the correlative experiment method may have potential applications for the generation of a live attenuated anthrax vaccine.     

Study of trans-placental transport of methylamphotericin B in albino rats after intravenous administration]

Transplacental penetration of amphotericin B, an methyl derivative, was studied on rats after its intravenous administration. Microbiological and radioisotopic methods were used. When the microbiological method was applied the drug was administered on days 16 to 20 or on day 20 of pregnancy in a dose of 4 mg/kg. For extraction of the antibiotic dimethylformamide was added to the substrates. The labeled antibiotic was administered in a dose of 3.3 mg/kg on days 6 to 16 and on day 20 of pregnancy. It was noted that the antibiotic accumulated in the placenta. The accumulation was more pronounced after antibiotic use in the course doses. A significant part of the antibiotic was in the placenta in the bound state. The methyl derivative amphotericin B was not detected microbiologically in the umbilical cord serum, fetal organs and amniotic fluid. Neither was it detected by extraction with ++dimethylformamide. The labeled antibiotic was neither detected in the amniotic fluid and fetal organs during the whole observation period. Therefore, the methyl derivative amphotericin B did not penetrate through the placental barrier either in the free or bound state. The direct teratogenic action of amphotericin B, a methyl derivative, after its intravenous administration to female rats is likely possible.     

Distribution and binding of oxytetracycline in the body of immunized animals]

Distribution and binding of oxytetracycline in immunized animals at various periods of immunogenesis (5, 10, 15, 20, 30 and 90 days after vaccination) were studied on rabbits, using dry live brucellosis vaccine, strain 19 as the antigen. The results of the study showed that immunological reconstruction of the macroorganism, its protective forces had a definite effect on the character of distribution, absorption and levels of oxytetracycline, as well as the processes of the antibiotic binding in the organism. The changes were indirect dependence on the immunogenesis periods: at the beginning of immunogenesis there was some increase in the antibiotic levels, as well as increased binding of the drug in the organs where reconstruction, activation and hyperplasia of the lymphoreticular cells occurred. During the productive phase of the antigen formation the antibiotic levels were 1,5-2 times lower, however, the processes of the antibiotic binding were more pronounced in the organs, where immunocompetent cells and antibodies were synthesized. During extinction of immunogenesis reduction of the initial antibiotic levels was recorded. Therefore, the changes directly depended on the periods of immunogenesis.     

T细胞记忆的理论研究

基于CD8⁺ T记忆细胞的线性和逆线性分化假说分别建立了数学模型,并研究了各种T细胞亚类的动力学.发现在优化剂量抗原入侵的条件下,两个模型均能产生记忆,并可较好地模拟实验结果.通过进一步模拟发现CD8⁺ T细胞记忆与抗原的存在紧密相关,再次证实了抗原在维持T细胞记忆中的作用.另外还讨论了记忆细胞寿命的问题.认为逆线性假说具有更强的反应性和记忆性.     

Cerulenin is a potent inhibitor of antigen processing by antigen-presenting cells

Cerulenin is an antibiotic that inhibits eukaryotic lipid and sterol synthesis and blocks lipid modification of proteins. The effect of cerulenin on the ability of accessory cells to present antigen to T cells was investigated. This antibiotic strongly inhibits the ability of accessory cells to present antigen to murine T-T hybrids. This effect is observed for multiple distinct antigens including L-glutamic acid60-L-alanine30-L-tyrosine10, bovine insulin, L-glutamic acid56-L-lysine35-L-phenylalanine9, and ovalbumen. Presentation by both macrophage and B lymphoblastoid cell lines is inhibited. The ability to effectively pulse these cells with antigen is inhibited but not the ability of these same cells to present antigen that they have previously processed. Furthermore, this inhibition is selective as it can occur without significant inhibition of the antigen-presenting cell protein or DNA synthesis. Cerulenin does not inhibit antigen uptake or catabolism as assessed with labeled antigen. By these criteria this drug is shown to interfere with an antigen-processing step. The ability of cerulenin to block processing was compared with other known inhibitors. Although cerulenin was effective with all antigens tested, at least one inhibitor was not. Taken together, these results suggest that the effect of cerulenin may define a distinct step in antigen processing and provides evidence that some other processing events are not universally required. The ability of cerulenin to interfere with antigen processing is discussed in the context of the known actions of this antibiotic and events of antigen processing and presentation.     

Effect of tetracycline on arylamidase activity in the liver of rabbits of different age

The effect of chlortetracycline on activity of the liver aryl amidases was studied. The antibiotic was used in a dose of 15 mg/kg for 6 days. It was noted that the use of chlortetracycline resulted in increased activity of the liver aryl amidases in young and old animals. In mature rabbits the aryl amidase activity under the experimental conditions lowered.     

Trichinella spiralis: strong antibody response to a 49 kDa newborn larva antigen in infected rats

In this work, we analyzed the kinetics of anti-Trichinella spiralis newborn larva (NBL) antibodies (Ab) and the antigenic recognition pattern of NBL proteins and its dose effects. Wistar rats were infected with 0, 700, 2000, 4000 and 8000 muscle larvae (ML) and bled at different time intervals up to day 31 post infection (p.i.). Ab production was higher with 2000 ML dose and decreased with 8000, 4000 and 700 ML. Abs were not detected until day 10, peaked on day 14 for the 2000 ML dose and on day 19 for the other doses and thereafter declined slowly from 19 to 31 days p.i. In contrast, Abs to ML increased from day 10, peaked on day 19 and remained high until the end of the study. Abs bound strongly at least to three NBL components of 188, 205 and 49 kDa. NBL antigen of 188 and 205 kDa were recognized 10-26 days p.i. and that of 49 kDa from day 10 to day 31 p.i. A weak recognition towards antigens of 52, 54, 62 and 83 kDa was also observed during the infection. An early recognition of 31, 43, 45, 55, 68 and 85 kDa ML antigens was observed whereas the response to those of 43, 45, 48, 60, 64 and 97 kDa (described previously as TSL-1 antigens) occurred late in the infection. A follow-up of antigen recognition up to day 61 with the optimal immunization dose (2000 ML) evidenced a decline of Ab production to the 49 kDa NBL antigen 42 days p.i., which suggested antigenic differences with the previously reported 43 kDa ML antigen strongly recognized late in the infection. To analyze the stage-specificity of the 49 kDa NBL antigen, polyclonal antibodies (PoAb) were obtained in rats immunized with 49 kDa NBL antigen. PoAb reacted strongly with the 49 kDa NBL component in NBL total soluble extract but no reactivity was observed with soluble antigen of the other T. spiralis stages. Albeit with less intensity, the 49 kDa component was also recognized by PoAb together with other antigens of 53, 97 and 107 kDa, in NBL excretory-secretory products (NBL-ESP). Thus, our results reveal differences in the kinetics of anti-NBL and ML Ab responses. While anti-NBL Abs declined slowly from day 19 until the end of the experiment, Abs to ML antigen remained high in the same period. It is remarkable the optimal Ab response to NBL antigens with 2000 ML infective dose and the reduced number of NBL antigens identified throughout the experimental T. spiralis infection, standing out the immunodominant 49 kDa antigen. Interestingly, this antigen, which was prominently expressed in NBL somatic proteins, was also detected in NBL-ESP.     

Experimental Chagas' disease: I. Study of different immunization conditions in the infection course]

In previous works it has been demonstrated that Balb/c albino mice immunized with Trypanosoma rangeli developed cellular and humoral immune response to Tripanosoma cruzi. Moreover, the immunized animals were protected against lethal infection by virulent T. cruzi trypomastigotes. In fact, immunized mice had significantly lower parasitemias and longer survival than controls. To go further in this experimental model, the aim of the present work was to analyze the effect of the number of antigenic stimuli and the conservation of the antigen on the effectiveness of protective effect. For that purpose, three different immunization schedules injecting T. rangeli epimastigotes fixed with glutaraldehide and emulsified with Saponin (SAP) as adjuvant were assayed. Different lots of mice which received only phosphate buffer saline or SAP were used as controls. In another set of experiments the conservation of the antigen during 90 days at 4 degrees C was studied. In all the experiments mice were infected with 100 trypomastigotes of T. cruzi, Tulahuén strain. The parasitemias were analyzed on 13th, 16th and 21st post infection days, and the survival until the 60th day. The results revealed that one dose of antigen was inadequate to give an effective protection. On the other hand, mice immunized with 2 and 3 dose showed a significant decrease of parasitemia with regard to controls (p < 0.001 - p < 0.0001) and the survival were markedly increased. Likewise, the antigen kept during 90th days at 4 degrees C showed similar protective efficacy than fresh antigen. Both of these experimental groups showed significant differences with respect to control animals in parasitemia (p < 0.05 - p > 0.01) and survival (p < 0.01). In conclusion, the results of this work showed that in the experimental conditions assayed, the immunization with T. rangeli trigger and adequate immune response when mice received at least two antigenic stimuli. Likewise, it is interesting to point out the stability of the antigenic preparation during at least 90th days.     

Brugia malayi: detection of parasite antigen in sera from infected jirds

Sera from Brugia malayi-infected jirds were demonstrated to contain a heat-stable, 95- to 105-kDa parasite antigen by immunoblot with rabbit antibody to the parasite and with a monoclonal antibody that binds to phosphorylcholine. This antigen is a major component of B. malayi adult worm excretory/secretory antigen, and it is present in lavage fluid obtained from ip-infected animals. The antigen was detected by enzyme immunoassay in all sera collected from jirds 9-54 weeks after sc injection with 100 or 300 infective larvae (L3). Parasite antigen titers were higher in animals infected with the higher L3 dose. Antiphosphorylcholine antibodies were present in jird sera for the first 12 weeks after larval injection, but thereafter, antibody titers decreased to undetectable levels. Parasite antigen was not detected by immunoblot or enzyme immunoassay in sera from 21 human subjects with B. malayi microfilaremia. Antigen may be cleared from human sera by antiphosphorylcholine antibodies, which were present in all sera tested. The practical significance of B. malayi antigen detection in the jird is that it provides a sensitive means of noninvasively monitoring the status of infection in this important experimental filariasis model.     

Optimal combined use of rifampicin and immunomodulator of microbial origin in experimental Q-Rickettsia infection

Multifactorial analysis of the combined use of rifampicin and an immunomodulator of the microbial origin, such as peptidoglycan, was performed on a model of experimental Q fever in albino mice. On the basis of the experimental results, statistic polynomial models describing the weight of the murine spleens and the titers of the complement-binding antibodies were designed. It was shown that the action of the immunomodulator and antibiotic was highly synergistic with respect to the chemotherapeutic activity and antibody titers. The preventive use of the immunomodulator yielded a 30-fold decrease in a rifampicin therapeutic dose. The use of the immunomodulator also provided a pronounced immunomodulating effect with respect to humoral immunity. Nomographs for optimizing the dose-time parameters of the antibacterial and immunomodulating therapy were plotted.