Effects of Cyclophosphamide on Visceral Leishmaniasis in the Mouse*

SYNOPSIS Cyclophosphamide (Cy), 125 or 200 mg/kg body weight, injected intraperitoneally (i.p.) into BALB/c mice one day before infection with amastigotes of Leishmania donovani, by the 8th day postinfection caused a significant decrease in the mean numbers of parasites in spleens and livers when compared to mice injected with phosphate buffered saline (PBS). When 125 mg/kg was injected into chronically infected mice (on day 34 of infection), however, within 2 days (day 36) mean parasite levels in both the spleens and livers were statistically greater than in PBS-treated controls. Similarly, when a series of 6 Cy injections, 50 mg/kg each, was injected over a period of 8 days during the chronic stage of infection, the mean parasite levels in both spleens and livers were significantly increased over those of PBS-treated controls. Druing the chronic stage of infection, Cy injections suppressed the immunity to superinfection. Neither plasma nor parasitized peritoneal macrophages obtained from Cy-treated mice, when compared to PBS-treated mice, differed in their respective capacities to influence the growth of intracellular amastigote of L. donovani in vitro. Passive transfer of hyperimmune mouse serum could not reverse the immunosuppressive effects of Cy upon chronic leishmaniasis in the mouse. It is suggested that neither readily demonstrable anti-leishmanial humoral factors nor “immune” macrophages per se, plays a major role in acquired immunity to leishmaniasis in the mouse.     

The adaptive potential of a survival artist: characterization of the in vitro interactions of Toxoplasma gondii tachyzoites with di-cationic compounds in human fibroblast cell cultures

The impact of di-cationic pentamidine-analogues against Toxoplama gondii (Rh- and Me49-background) was investigated. The 72 h-growth assays showed that the arylimidamide DB750 inhibited the proliferation of tachyzoites of T. gondii Rh and T. gondii Me49 with an IC(50) of 0·11 and 0·13 μM, respectively. Pre-incubation of fibroblast monolayers with 1 μM DB750 for 12 h and subsequent culture in the absence of the drug also resulted in a pronounced inhibiton of parasite proliferation. However, upon 5-6 days of drug exposure, T. gondii tachyzoites adapted to the compound and resumed proliferation up to a concentration of 1·2 μM. Out of a set of 32 di-cationic compounds screened for in vitro activity against T. gondii, the arylimidamide DB745, exhibiting an IC(50) of 0·03 μM and favourable selective toxicity was chosen for further studies. DB745 also inhibited the proliferation of DB750-adapted T. gondii (IC(50)=0·07 μM). In contrast to DB750, DB745 also had a profound negative impact on extracellular non-adapted T. gondii tachyzoites, but not on DB750-adapted T. gondii. Adaptation of T. gondii to DB745 (up to a concentration of 0·46 μM) was much more difficult to achieve and feasible only over a period of 110 days. In cultures infected with DB750-adapted T. gondii seemingly intact parasites could occasionally be detected by TEM. This illustrates the astonishing capacity of T. gondii tachyzoites to adapt to environmental changes, at least under in vitro conditions, and suggests that DB745 could be an interesting drug candidate for further assessments in appropriate in vivo models.     

Antimalarial activity of endoperoxide compound 6-(1,2,6,7-tetraoxaspiro[7.11]nonadec-4-yl)hexan-1-ol

Plasmodium falciparum, the major causative parasite for the disease, has acquired resistance to most of the antimalarial drugs used today, presenting an immediate need for new antimalarial drugs. Here, we report the in vitro and in vivo antimalarial activities of 6-(1,2,6,7-tetraoxaspiro[7.11]nonadec-4-yl)hexan-1-ol (N-251) against P. falciparum and Plasmodium berghei parasites. The N-251 showed high antimalarial potencies both in the in vitro and the in vivo tests (EC₅₀ 2.3 × 10⁻⁸ M; ED₅₀ 15 mg/kg (per oral)). The potencies were similar to that of artemisinin in vitro and greater than artemisinin's activity in vivo (p.o.). In addition, N-251 has little toxicity: a single oral administration at 2000 mg/kg to a rat gave no health problems to it. Administration of N-251 to mice bearing 1% of parasitemia (per oral 68 mg/kg, 3 times a day for 3 consecutive days) resulted in a dramatic decrease in the parasitemia: all the 5 mice given N-251 were cured without any recurrence, with no diarrhea or weight loss occurring in the 60 days of experiment. N-251 deserves more extensive clinical evaluation, desirably including future trials in the human.     

Combination therapy using the cyclooxygenase-2 inhibitor Parecoxib and radioimmunotherapy in nude mice with small peritoneal metastases of colonic origin

Background: Inhibition of the COX-2 enzyme has been shown to have a radiosensitizing effect in epithelial cancers. The aim of this study was to investigate whether the efficacy of radioimmunotherapy (RIT) using ¹³¹I-labeled anti-CEA monoclonal antibody MN-14 could be enhanced by co-administration of the selective COX-2 inhibitor Parecoxib in mice with small volume (1–3 mm) peritoneal carcinomatosis of colonic origin. Methods: First, the efficacy of 14 daily injections of Parecoxib monotherapy (0 – 0.2 – 1.0 – 5.0 – 25.0 mg/kg) was determined in mice with intraperitoneal LS174T xenografts. Second, the influence of Parecoxib (1.0 or 5.0 mg/kg) on the biodistribution of ¹²⁵I-MN-14 was assessed. Finally, the efficacy of RIT alone [125 μCi ¹³¹I-MN-14/mouse ≈ 1/4 of the maximal tolerated dose (MTD)] was compared with that of Parecoxib monotherapy and RIT combined with daily injections of Parecoxib (1.0 or 5.0 mg/kg). Results: Parecoxib had no measurable antitumor effect up to the highest dose level (25 mg/kg). Parecoxib had no effect on the uptake of ¹²⁵I-MN-14 in the intraperitoneal tumor xenografts or on normal tissue distribution. Median survival of the control mice and the mice treated with Parecoxib monotherapy (1.0 or 5.0 mg/kg) was 48.5 days, 52 days and 52 days (P=0.47). RIT alone significantly delayed the growth of the intraperitoneal xenografts resulting in a median survival of 87 days (P<0.0001). Mice treated with RIT + Parecoxib at 1.0 or 5.0 mg/kg had a median survival of 73.5 days and 76 days, respectively, which was not statistically different from survival after RIT alone (P=0.15). Conclusion: The COX-2 inhibitor Parecoxib does not enhance the therapeutic efficacy of RIT of experimental small volume peritoneal carcinomatosis of colonic origin.     

Blastogenic responsiveness of spleen cells fromLegionella pneumophila-infected mice immunosuppressed with cyclophosphamide

Although guinea pigs are highly susceptible to experimental infection withLegionella pneumophila, mice are considered resistant. In the present study it was found that, although untreated mice resisted lethal infection with up to 10⁷ L. pneumophila, mice treated with three divided doses of cyclophosphamide became 10–100 times more susceptible. Injection of mice with 150 mg cyclophosphamide/kg body weight 96 and 48h prior to and on the same day as intraperitoneal challenge with graded dose ofL. pneumophila resulted in markedly increased lethality. Approximately half of the mice pretreated with cyclophosphamide succumbed to 10⁶ legionellae within 4–10 days after infection, and all treated animals given 10⁷ bacteria died. Legionellae were readily recovered from spleen, lymph nodes, and liver of surviving mice 4–10 days after infection, but not thereafter. Sensitization of mice with Legionella antigen was evident by the lymphocyte blastogenic test in vitro, by use of spleen cells at various times after infection. Mice given graded doses ofL. pneumophila evinced enhanced responsiveness to either formalin-killed whole cell vaccine, cell-free sonicate, or purified outer membrane antigen when tested in vitro on days 3 and 5. Peak responses generally occurred 20–35 days after infection. Mice given none or one dose of cyclophosphamide and injected with legionellae showed enhanced responses on day 5 of culture in vitro, a time when spleen cells from control nonsensitized animals showed much lower responses. Surviving mice given three doses of cyclophosphamide had lower blastogenic responses, generally as low as that occurring with spleen cells from nonsensitized animals. Thus suppression of immune responses of mice by cyclophosphamide substantially increased susceptibility toL. pneumophila and depressed blastogenic responsiveness.     

Echinococcus granulosus:An Intraperitoneal Diffusion Chamber Model of Secondary Infection in Mice

Breijo, M., Spinelli, P., Sim, R.B., and Ferreira, A. M. 1998.Echinococcus granulosus:An intraperitoneal diffusion chamber model of secondary infection in mice.Experimental Parasitology90, 270–276. The present work describes a new experimental model of secondary infection which allows, through the recovery of the parasite together with its localin vivoenvironment, examination of the local nonadaptive immune response of the infected host and the differentiation of the parasite from protoscoleces to cysts. In this model we administered protoscoleces within silicone diffusion chambers, previously implanted into the peritoneal cavities of mice. The process of designing the model involved, first, determination of the optimal time postimplantation to infect the mice and, second, evaluation of the parasite's ability to establish infection within the chambers. The optimal time for infection was considered to be after the inflammation caused by implantation of the chambers had subsided. Our results showed that by day 20 postsurgery, three parameters used as indications of inflammation (complement C3, serum amyloid P protein, and polymorphonuclear cells in the peritoneum and in the chamber contents) had reverted to their normal levels. In our study of parasite differentiation, we found that 2–3% of the total number of parasites inoculated into the chambers were recovered as viable cysts after 100 days. Throughout the infection period, the population of parasites recovered was heterogeneous; certain parasite morphologies that have not been described previously were observed. In conclusion, the use of intraperitoneal diffusion chambers offers a potential tool for investigating thein vivodifferentiation process of secondary cysts ofEchinococcus granulosusin mice and the early local interactions between host and parasite during this process.     

Infectivity, growth, development and pathology of Echinostoma caproni (Trematoda) in the golden hamster

Laboratory hamsters (Mesocricetus auratus) were experimentally infected with 75 ± 15 metacercarial cysts of Echinostoma caproni. Worms were recovered from days 7 to 89 post-infection with eight to 90 (average 37) parasites in the small intestine. Worm wet weights averaged 0.85 mg at 10 days, 1.8 mg at 17 days, 3.4 mg at 45 days, and 7.7 mg at 89 days; average dry weights for the identical days were, 0.15, 0.30, 0.70 and 2.2 mg, respectively. The average body area of worms fixed in hot (80°C) alcohol-formalin-acetic acid was 0.21 mm² on day 3, 4.9 mm² on day 10, and 17.7 mm² on day 42. Clinical signs in some hamsters included progressive unthriftiness and watery diarrhea. Gross examination revealed enlarged lymphatic nodules along the length of the small intestine. The histopathological responses of hamsters to the parasite showed erosion of the intestinal villi with lymphocytic infiltration being the primary response; hemorrhagic areas were also observed in the villi.     

Synergistic induction of lymphokine (IL-2)-activated killer activity by IL-2 and the polysaccharide lentinan,and therapy of spontaneous pulmonary metastases

Summary Spleen cells of C57BL/6N mice bearing lung metastases were induced to the cytotoxic state by subcutaneous injection of recombinant human interleukin-2 (IL-2) at a minimum dose of 5×10⁴ U/mouse three times a day for 3 consecutive days. A single intraperitoneal injection of lentinan alone at concentrations of up to 10 mg/kg body weight did not render spleen cells cytotoxic to P-29 cells, but a combination of subthreshold doses of these agents (5×10⁴ U/ml IL-2 and 5 mg/kg lentinan) induced significant in vivo lymphokine-activated killer activity in spleen cells of tumor-bearing mice. Similarly, spleen cells from mice treated i.p. with lentinan became cytotoxic on in vitro treatment with IL-2. The in vitro responsiveness of spleen cells to IL-2 was maximal 3 days after i.p. injection of lentinan. Synergism between IL-2 and lentinan was also observed in mice bearing spontaneous lung micrometastases: neither IL-2 (<5×10⁴ U/mouse) nor lentinan (<2.5 mg/kg) alone had a therapeutic effect, but multiple injections of IL-2 with a single injection of lentinan resulted in significant inhibition of spontaneous pulmonary metastases. From these results we conclude that IL-2 and lentinan in combination are more effective than either one alone for inducing destruction of pulmonary metastases.     

Artificial Infections of Pneumocystis carinii in the SCID Mouse and their Use in the In Vivo Evaluation of Antipneumocystis Drugs

A model for the in vivo evaluation of antipneumocystis drugs has been developed in SCID mice infected intratracheally with cryopreserved mouse-derived Pneumocystis carinii. The development of a highly reproducible fatal P. carinii pneumonia occured within 10 weeks (mean survival time ± SEM = 72.2 ± 1.2 days). Continuous administration of dexamethasone (2 mg/liter in the drinking water) exacerbated the rate of onset of severe P. carinii pneumonia (mean survival time ± SEM = 63 ± 1.3 days) in SCID mice. The number of cysts per g of lung homogenate (homogenate counts) were maximal with an inoculum of 20,000 cysts at 6 weeks post infection. Homogenate counts correlated with infection scores (graded assessments of immunofluorescent cysts on lung impression smears) suggesting that infection scoring accurately and rapidly reflects the severity of P. carinii pneumonia in SCID mice. These studies led to the development of a drug screening protocol in which Pneumocystis-free female SCID mice (20–25 g) were started on dexamethasone 7 days prior to IT inoculation with a single dose of 20,000 cysts. Drugs were evaluated either for: a) prophylaxis (continuously from day 1 post infection) or b) treatment (from day 21 post infection) until day 42 post infection, when all mice were killed and infection scores determined. Co-trimoxazole (at 250 mg sulfamethoxazole + 50 mg trimethoprim/kg/day) given in the drinking water was found to be highly effective in both the prophylaxis and treatment of mouse P. carinii pneumonia. Co-trimoxazole remained very effective in the prophylaxis P. carinii pneumonia in the SCID mouse at 125 mg sulfamethoxazole + 25 mg trimethoprim/kg/day p.o. and showed some enhancement of efficacy over sulfamethoxazole alone at 125 mg/kg/day p.o., suggesting limited synergy between sulfamethoxazole and trimethoprim. The results presented provide confirmation of the usefulness and predictability of the model.     

Efficacy of ponazuril in vitro and in preventing and treating Toxoplasma gondii infections in mice

Toxoplasma gondii is an important apicomplexan parasite of humans and other warm-blooded animals. Ponazuril is a triazine anticoccidial recently approved for use in horses in the United States. We determined that ponazuril significantly inhibited T. gondii tachyzoite production (P < 0.05) at 5.0, 1.0, or 0.1 microg/ml in African green monkey kidney cells. We used outbred female CD-1 mice to determine the efficacy of ponazuril in preventing and treating acute toxoplasmosis. Each mouse was subcutaneously infected with 1,000 tachyzoites of the RH strain of T. gondii. Mice were weighed daily, and ponazuril was administered orally in a suspension. Mice given 10 or 20 mg/kg body weight ponazuril 1 day before infection and then daily for 10 days were completely protected against acute toxoplasmosis. Relapse did not occur after prophylactic treatments were stopped. Toxoplasma gondii DNA could not be detected in the brains of these mice using polymerase chain reaction (PCR). One hundred percent of mice treated with 10 or 20 mg/kg ponazuril at 3 days after infection and then daily for 10 days were protected from fatal toxoplasmosis. Sixty percent of mice treated with 10 mg/kg ponazuril at 6 days after infection and 100% of mice treated with 20 mg/kg or 50 mg ponazuril 6 days after infection and then daily for 10 days were protected from fatal toxoplasmosis. Relapse did not occur after treatments were stopped. Toxoplasma gondii DNA was detected in the brains of some, but not all, of these mice using PCR. The results demonstrate that ponazuril is effective in preventing and treating toxoplasmosis in mice. It should be further investigated as a safe and effective treatment for this disease in animals.     

Chemotherapy of Second Stage Human African Trypanosomiasis: Comparison between the Parenteral Diamidine DB829 and Its Oral Prodrug DB868 in Vervet Monkeys

Human African trypanosomiasis (HAT, sleeping sickness) ranks among the most neglected tropical diseases based on limited availability of drugs that are safe and efficacious, particularly against the second stage (central nervous system [CNS]) of infection. In response to this largely unmet need for new treatments, the Consortium for Parasitic Drug Development developed novel parenteral diamidines and corresponding oral prodrugs that have shown cure of a murine model of second stage HAT. As a rationale for selection of one of these compounds for further development, the pharmacokinetics and efficacy of intramuscular (IM) active diamidine 2,5-bis(5-amidino-2-pyridyl)furan (DB829; CPD-0802) and oral prodrug2,5-bis[5-(N-methoxyamidino)-2-pyridyl]furan (DB868) were compared in the vervet monkey model of second stage HAT. Treatment was initiated 28 days post-infection of monkeys with T. b. rhodesiense KETRI 2537. Results showed that IM DB829 at 5 mg/kg/day for 5 consecutive days, 5 mg/kg/day every other day for 5 doses, or 2.5 mg/kg/day for 5 consecutive days cured all monkeys (5/5). Oral DB868 was less successful, with no cures (0/2) at 3 mg/kg/day for 10 days and cure rates of 1/4 at 10 mg/kg/day for 10 days and 20 mg/kg/day for 10 days; in total, only 2/10 monkeys were cured with DB868 dose regimens. The geometric mean plasma Cmax of IM DB829 at 5 mg/kg following the last of 5 doses was 25-fold greater than that after 10 daily oral doses of DB868 at 20 mg/kg. These data suggest that the active diamidine DB829, administered IM, should be considered for further development as a potential new treatment for second stage HAT.     

Effects of cysteamine onPseudomonas infections in mice

A non-lethal dose of cysteamine — a radioprotective agent — when administered intraperitoneally was demonstrated to increase the susceptibility of mice to infection byPseudomonas aeruginosa. At numbers of cells (about 10⁶) which killed 30–40 per cent of the untreated mice, the intraperitoneal treatment with 5 mg per day of cysteamine raised the mortality to 60 per cent. In contrast, the presence of 10 mg/ml of cysteamine in drinking water appeared to give some protection against the same number ofPseudomonas cells for the first three days after infection, but increased the susceptibility when the oral treatment was prolonged beyond three days. Such effects could have some significance in the study of sulfhydryl compounds as radioprotective agents.     

Antibiotic Treatment in Mice Infected with Japanese Borrelia garinii: Efficacy of Ceftriaxone for Eradicating the Infection Induced by Ixodes persulcatus Tick Bites

We compared the efficacy of three antibiotics (ceftriaxone, erythromycin and clarithromycin) against Borrelia garinii infection in mice. The nymphal ticks of Ixodes persulcatus infected with the strain JEM6 of Japanese B. garinii were allowed to feed on female C3H mice. The mice were treated with each of the antibiotics for 5 consecutive days 1, 3, or 7 weeks after tick detachment. The doses of antibiotics per day were as follows: 5 mg intraperitoneal injection of ceftriaxone, 2 mg intraperitoneal injection of erythromycin and 1 mg peroral administration of clarithromycin. The infection status in treated mice was monitored by culturing their earlobes, hearts and urinary bladders in BSK II medium. Ceftriaxone eliminated borreliae completely; however, a recurrence of infection was observed in mice treated with erythromycin and clarithromycin.     

Dissemination of extracellular and intracellular Toxoplasma gondii tachyzoites in the blood flow

Toxoplasma gondii is an intracellular parasite. It has been thought that T. gondii can disseminate throughout the body by circulation of tachyzoite-infected leukocytes (intracellular parasite) in the blood flow. However, a small number of parasites exist as free extracellular tachyzoites in the blood flow (extracellular parasite). It is still controversial whether the extracellular parasites in the blood flow disseminate into the peripheral tissues. In this study, we evaluated the dissemination efficiency of the extracellular and intracellular parasites in the blood flow using GFP-expressing transgenic parasite (PLK/GFP) and DsRed Express-expressing transgenic parasite (PLK/RED). When PLK/GFP and PLK/RED tachyzoites were injected, as intracellular and extracellular forms respectively, at the same time into the tail vein of a mouse, many disseminated green fluorescent PLK/GFP tachyzoites were observed in the lung, the spleen, the liver and the brain. However, only a few red fluorescent PLK/RED tachyzoites were detected in these organs. When PLK/GFP and PLK/RED tachyzoites were injected in the opposite manner, that is, as extracellular and intracellular forms respectively, the majority of tachyzoites in these tissues were PLK/RED tachyzoites. Collectively, these results indicate that intracellular tachyzoites mainly disseminate throughout the body and that extracellular tachyzoites hardly contribute to parasite dissemination.     

Stage conversion of Toxoplasma gondii RH parasites in mice by treatment with atovaquone and pyrrolidine dithiocarbamate

The mouse-virulent RH strain of Toxoplasma gondii is generally considered to have lost its cyst-forming capacity, and conversion of RH tachyzoites into cysts in non-immune mice has previously been shown exclusively following early treatment with sulfadiazine (SDZ). We here describe the development of tissue cysts in mice infected with RH strain parasites and treated with atovaquone (ATO) combined with pyrrolidine dithiocarbamate (PDTC). Groups of Swiss-Webster mice infected intraperitoneally (i.p.) with 10(2) RH tachyzoites were treated with 5, 25 and 100 mg of ATO/kg per day alone or combined with PDTC at 250 mg/kg per day from day 1 postinfection (p.i.) for 14 days. A total of 19 mice survived the 6-week observation period. Of these, brain cysts were recovered in nine (47%), with burdens ranging from 50 to 3120 (mean +/- S.D. = 622 +/- 963). All cyst-harboring mice had high specific IgG antibody levels (1:10,240-1:40,960, corresponding to 500-2000 IU/ml), as did one mouse in which cysts were not demonstrated, which was therefore included in the group of mice with residual infection. Bioassay performed to test the infectivity of these cysts produced acute lethal toxoplasmosis following i.p. inoculation in all instances (100%), and importantly, following peroral inoculation in four (29%). The recovered tachyzoites were highly infectious. In addition, significantly elevated interferon gamma (IFN-gamma) in the treated mice which developed residual infection compared with any group of infection-free (treated or subinoculated) mice, indicates immunological control of the parasite in the latent form. In conclusion, early treatment of mice infected with T. gondii RH tachyzoites with ATO and PDTC induces conversion into tissue cysts, thus providing a new model for studying the mechanism(s) of T. gondii stage conversion.     

In vitro effects of arylimidamides against Besnoitia besnoiti infection in Vero cells

The in vitro effects of 4 arylimidamides (DB811, DB786, DB750 and DB766) against the proliferative tachyzoite stage of the apicomplexan parasite Besnoitia besnoiti were investigated. These four compounds had been shown earlier to exhibit in vitro activities in the nanomolar range against the related apicomplexans Neospora caninum and Toxoplasma gondii. Real-time-PCR was used to assess B. besnoiti intracellular proliferation in vitro. Preliminary assessment by light microscopy identified DB811 and DB750 as the most promising compounds, while DB786 and DB766 were much less effective. Three-day-growth assays and quantitative real-time PCR was used for IC50 determination of DB811 (0.079 μM) and DB750 (0.56 μM). Complete growth inhibition was observed at 1.6 μM for DB 811 and 1.7 μM for DB750. However, when infected cultures were treated for 14 days, proliferation of parasites occurred again in cultures treated with DB750 from day 4 onwards, while the proliferation of DB811-treated tachyzoites remained inhibited. Electron microscopy of B. besnoiti-infected fibroblast cultures fixed and processed at different time-points following the initiation of drug treatments revealed that DB811 exerted a much higher degree of ultrastructural alterations compared to DB750. These results show that arylimidamides such as DB811 could potentially become an important addition to the anti-parasitic arsenal for food animal production, especially in cattle.     

Anti‐infectious activity of synbiotics in a novel mouse model of methicillin‐resistant Staphylococcus aureus infection

The anti‐infectious activity of synbiotics against methicillin‐resistant Staphylococcus aureus (MRSA) infection was evaluated using a novel lethal mouse model. Groups of 12 mice treated with multiple antibiotics were infected orally with a clinical isolate of MRSA at an inoculum of 10⁸ CFU on day 7 after starting the antibiotics. A dose of 400 mg/kg 5‐fluorouracil (5‐FU) was injected intraperitoneally on day 7 after the infection. A dose of 10⁸ CFU Bifidobacterium breve strain Yakult and 10 mg of galactooligosaccharides (GOS) were given orally to mice daily with the antibiotic treatment until day 28. The intestinal population levels of MRSA in the mice on multiple antibiotics were maintained stably at 10⁸ CFU/g of intestinal contents after oral MRSA infection and the subsequent 5‐FU treatment killed all the mice in the group within 14 days. B. breve administration saved most of the mice, but the synbiotic treatment saved all of the mice from lethal MRSA infection. The synbiotic treatment was effective for the treatment of intestinal infection caused by four MRSA strains with different toxin productions. There was a large difference among the six Bifidobacteria strains that were naturally resistant to the antibacterial drugs used. B. breve in combination with GOS is demonstrated to have valuable preventive and curative effects against even fatal MRSA infections.     

Prophylactic and Therapeutic Potential of Acetyl‐l‐carnitine against Acetaminophen‐Induced Hepatotoxicity in Mice

Prophylactic and therapeutic effects of acetylcarnitine against acetaminophen‐induced hepatotoxicity were studied in mice. To evaluate the prophylactic effects of acetylcarnitine, mice were supplemented with acetylcarnitine (2 mmol/kg/day per oral (p.o.) for 5 days) before a single dose of acetaminophen (350 mg/kg intraperitoneal (i.p.)). Animals were sacrificed 6 h after acetaminophen injection. Acetaminophen significantly increased the markers of liver injury, hepatic reactive oxygen species, and nitrate/nitrite, and decreased hepatic glutathione (GSH) and the antioxidant enzymes. Acetylcarnitine supplementation resulted in reversal of all biochemical parameters toward the control values. To explore the therapeutic effects of acetylcarnitine, mice were given a single dose of acetylcarnitine (0.5, 1, and 2 mmol/kg p.o.) 1.5 h after acetaminophen. Animals were sacrificed 6 h after acetaminophen. Acetylcarnitine administration resulted in partial reversal of liver injury only at 2 mmol/kg p.o. At equimolar doses, N‐acetylcystiene was superior as therapeutic agent to acetylcarnitine. However, acetylcarnitine potentiated the effect of N‐acetylcystiene in the treatment of acetaminophen toxicity.     

Periodic appearance of a predominant variant antigen type during a chronic Giardia lamblia infection in a mouse model

Giardia lamblia (syn. Giardia duodenalis, Giardia intestinalis) infections are associated with continuous antigenic variation of the parasite which is mediated by the parasite's major surface antigen, named variant surface protein. Offspring mice and corresponding mothers were infected with G. lamblia clone GS/M-83-H7 (expressing variant surface protein H7) and various parameters of this infection were assessed in a long-term follow-up investigation. Our experimentation revealed that variant surface protein H7-type trophozoites were replaced by new variant-type trophozoites during the early stage of infection (around day 8 p.i.), but the original variant-type re-emerged at at least two time-points during the later stages of infection (at days 22 and 42 p.i.). Such periods of variant surface protein H7-type trophozoite re-expansion were accompanied by transient production of intestinal IgA against variant-specific epitopes on a 314-aa N-terminal region of variant surface protein H7. At late stages of infection (between days 42 and 200 p.i.), most mice produced intestinal IgA against both variant surface protein H7 and other antigens of the parasite. At these stages, infection seemed to be resolved in most mice, but occasional reappearance of relatively high (at day 64 p.i.) or at least detectable (at days 80 and 120 p.i.) amounts of intestinal parasites indicated that G. lamblia GS/M-83-H7 infections in mice may enter into a latent chronic phase which is interrupted by sporadic breakthroughs of parasite growth.