Immunization of mice with gamma-irradiated intramuscularly injected schistosomula of Schistosoma mansoni

The parameters involved in the induction of resistance against Schistosoma mansoni by injection of irradiated, artificially transformed schistosomula were studied in mice. Single intramuscular injections of 500 schistosomula exposed to radiation doses in the range 2.3 to 160 krad. resulted in significant protection (in the range 20 to 50% as assessed by reduced worm burdens) against a challenge infection administered at intervals from 3 to 24 weeks post-vaccination. However, schistosomula irradiated with 20 krad. consistently resulted in better protection than those exposed to either higher or lower radiation doses despite the persistence of stunted adults from the infections irradiated with 2.3 krad. Vaccination with 40 krad. schistosomula resulted in significant protection in terms of reduced worm and tissue egg burdens and increased survival following lethal challenge. Varying the number of irradiated schistosomula, the frequency and route of their administration, the site of challenge and the strain of host all failed to enhance the level of resistance. However, percutaneously applied, irradiated cercariae were found to be more effective in stimulating resistance (60%) than intramuscularly injected, irradiated schistosomula (40%).     

Evaluation of the anthelmintic effects of artesunate against experimental Schistosoma mansoni infection in mice using different treatment protocols

The therapeutic effects of artesunate against experimental Schistosoma mansoni infection in mice were analyzed. Previous studies showed that artesunate is highly effective against S. japonicum infection, but the action of this drug against S. mansoni remained uncovered. The present study examines the optical conditions for artesunate against S. mansoni and evaluates the effects of inhibiting the sexual maturation of adult worms. Mice infected with S. mansoni were orally administered with artesunate according to different schedules. Four consecutive administrations of 300 mg/kg of artesunate at 2-week intervals conferred almost total protection without the development of pathological lesions in the liver. The significant reduction in the number of eggs produced by surviving worms and the status of egg maturation suggested that artesunate inhibits sexual maturation. Electron microscopy revealed that artesunate caused morphological damage, especially on the worm tegument. Artesunate was also very effective in iron-deficient mice. Furthermore, the efficacy of artesunate was equal to or better than that of artemether against S. japonicum infection. Considering that artemether is more toxic, artesunate is currently one of the most efficient drugs against immature S. mansoni.     

Effect of artemether administered alone or in combination with praziquantel to mice infected with Plasmodium berghei or Schistosoma mansoni or both

The artemisinins have become key drugs for the treatment and control of malaria, particularly within artemisinin-based combination therapies. Since the artemisinins also exhibit antischistosomal properties, their use in areas where malaria and schistosomiasis are co-endemic may have an effect on both diseases and co-infection might alter drug efficacy. We assessed the antimalarial and antischistosomal efficacies of artemether in mice infected with Plasmodium berghei or Schistosoma mansoni or both parasites concurrently. Three oral doses of 400 mg/kg artemether at 14-day intervals reduced total and female S. mansoni worm burdens by 98.7-100%, regardless of a concurrent P. berghei infection. When four daily doses of 55 mg/kg artemether were administered, which is a standard treatment schedule to cure P. berghei-infected mice, significantly lower total and female S. mansoni worm burden reductions were observed (73.1-89.2%). Artemether, administered at both of the above-mentioned treatment schemes, showed excellent antimalarial efficacy with no indications of delayed clearance of P. berghei or recrudescence, also in mice co-infected with S. mansoni. Co-infection with P. berghei had no effect on S. mansoni worm burden reductions following artemether-praziquantel combinations. Our findings point to the need for epidemiological studies in areas where malaria and schistosomiasis co-exist and where artemisinin-based combination therapies are introduced, since artemisinin-based combination therapies as part of a malaria control package may have ancillary benefits against schistosomiasis.     

Effectiveness of anticonvulsants in mice exposed to mixed gamma-neutron radiations

The effectiveness of four anticonvulsants was tested in male CF1 mice exposed to 500-, 1000-, and 10,000-rad doses of mixed gamma-neutron radiations. Prevention of the hind leg extensor component of a maximal convulsion induced by electroshock was selected as the end point for effective anticonvulsant activity of diphenylhydantoin, phenobarbital, and mephenytoin. Prevention of convulsions induced by pentylenetetrazol was the end point of effective anticonvulsant activity of trimethadione. The effectiveness of the drugs was evaluated by comparing the ED50's to the ED50 value for unirradiated controls. The anticonvulsants tested by electroshock showed a tendency toward increasing effectiveness after 500- and 1000-rad doses of radiation and a significantly increased effectiveness following 10,000 rads. Trimethadione effectiveness in irradiated mice was similar to that in unirradiated controls at all doses and times tested.     

Sedimentation Analysis of DNA from Irradiated and Unirradiated L Cells

DNA, released from unirradiated mouse L-cells gently lysed in a thin layer of 2% sucrose on top of an alkaline sucrose gradient, was found to sediment in a narrow band with a sedimentation coefficient of about 500S. Exposure of cells to increasing doses of X-rays (89-712 rads) continuously reduced the DNA sedimentation velocity until, after about 890 rads, the DNA appeared in a narrow peak with a sedimentation coefficient of approximately 180S. As the dose given to cells was increased beyond 890 rads, the sedimentation coefficient of the DNA released continued to decrease and the sedimentation profiles now broadened in a manner consistent with the random production of single-strand breaks in the DNA. The DNA released from unirradiated cells (500S) is thought to be loosely aggregated and only partially single stranded. It is presumed that cells exposed to low doses of radiation release DNA with marked reductions in sedimentation coefficient because single-strand breaks produced in the DNA aid the alkaline denaturation process. By using the system to be described, it has been possible to demonstrate DNA repair (rejoining of X-ray-induced single-strand breaks) during postirradiation incubation of cells given doses as low as 400 rads.     

Lower faecal egg excretion in chemically-induced diabetic mice infected with Schistosoma mansoni due to impaired egg maturation

The effect of streptozotocin-induced diabetes mellitus was studied in mice infected with Schistosoma mansoni. Faecal egg excretion was lower in diabetic mice but worm load and total amount of eggs in the intestine tissue were equal to the control group. Evaluation of an oogram showed a great number of immature dead eggs and a low number of mature eggs in diabetic mice. It was therefore concluded that faecal egg excretion was lower in diabetic mice due to impaired egg maturation.     

Excretory-secretory product of fasciola hepatica worm protects against Schistosoma mansoni infection in mice

The objective of this study was to evaluate the protective immunity of excretory-secretory products of Fasciola hepatica (FhES) worm against S.mansoni infection in mice. Evaluation of FhES antigen was through measuring worm burden, ova count, granuloma size and frequency as well as the histopathological picture of the liver. The study was extended to determine the level of free radical scavengers; lipid peroxide, glutathione (GSH), vitamin C, vitamin E, catalase and superoxide dismutase (SOD). Liver function enzymes such as aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) were also taken into consideration. Four groups of eight mice each were selected for this study. Group 1 served as control group. Group 2: normal healthy mice vaccinated with FhES product. Group 3: S.mansoni infected mice for 2 months and group 4: infected mice pre-vaccinated with FhES antigen. Vaccination schedule comprised of a single subcutaneous injection of FhES antigen emulsified with Freund's complete adjuvant in a dose 0.5 mg protein/mouse, followed by intraperitoneal injections of the same antigen without adjuvant in 3 doses/week for 3 successive weeks. The total antigen inoculation was 5 mg protein/mouse. The present results revealed a drastic change in all the measured parameters after S.mansoni infection and a noticeable improved level after vaccination with FhES antigen. It can be concluded that FhES antigen succeeded to protect mice against schistosomiasis by a significant reduction in worm burden, ova count, granuloma size and number, improvement in the histopathological architecture of the liver as well as amelioration in the antioxidant levels under investigation.     

Schistosoma mansoni: chemotherapy of infections of different ages

Mice were treated with potassium antimony tartrate, hycanthone, oxamniquine, niridazole, or praziquantel at different times after infection with Schistosoma mansoni. The rate of cure was assessed by perfusion of surviving worms approximately 4 weeks after treatment, and the percentage reduction in worm burden was estimated relative to the number of adult worms perfused from control mice, comparably infected but untreated. All six drugs were relatively inactive against S. mansoni between 3 and 4 weeks after infection when compared with treatment at 5 to 6 weeks. However, the drugs differed in the patterns of cure they achieved in the 2-week period after administration of cercariae and in the period around the onset of patency. Worms that had been subjected to amoscanate or hycanthone in the third week after infection showed evidence of this as adults in having a reduced fecundity. Factors such as worm or host physiology, or host immune status may have had roles in the outcome of chemotherapy at different stages of maturation of S. mansoni.     

Praziquantel, a new board-spectrum antischistosomal agent.

Praziquantel, (2-cyclohexylcarbonyl)-1,2,3,6,7,11b-hexa-hydro-2H pyrazino[2,1a]isoquinolin-4-one, belongs to a new series of antischistosomal compounds. The results of a detailed study of the efficacy of praziquantel on Schistosoma mansoni in mice, Mastomys and Syrian hamsters are described. Praziquantel is effective after oral and all parenteral routes of administration tested. The amount of praziquantel required to achieve parasite reductions of at least 95% depends on the host species and on the routes and schedules of administration. Total doses range from 200--1,000 mg/kg in mice and from 100--500 mg/kg for Mastomys and hamsters. In all three species, splitting of the total dose into 3 or more fractional doses given within 1 day approximately doubles the efficacy over that achieved after a single oral administration of the same total dose. A single subcutaneous dose is only slightly more effective, whilst a single intramuscular injection in olive oil is about twice as effective as a single oral administration. Praziquantel is very effective against the invading stages and slightly less against schistosomules up to an age of 7 days. It is less effective against 2- to 4-week-old juveniles, but is effective again against 5-week-old and older schistosomes. Praziquantel is equally effective against both sexes of S. mansoni. It is less effective against unpaired and therefore juvenile female worms, but fully effective against single male worms. The efficacy of praziquantel on S. mansoni in mice is not influenced by the strain or the sex of the host, the worm burden or the age of the infection. Considering all data available, praziquantel promises to be a very potent antischistosomal drug.     

Regeneration of CFUs in the marrow of mice exposed to 300 rads after having recovered from 950 rads.

Exposure to 950 rads 60Co radiation has been reported to cause long-lasting damage to the hematopoietic stroma (HS), although the size of the CFUs population recovers to pre-irradiation levels. In these studies HS damage was detected only after subcutaneously implanting the femurs of the irradiated mice into syngeneic hosts. To exclude the possibility that what was considered to be HS damage was merely caused by artifacts due to the process of implantation in a new host, we compared the rate of regeneration of CFUs in mice which had recovered from 950 rads prior to receiving 300 rads 60Co radiation (950 + 300 rads group) with that of mice which received only 300 rads (0 + 300 rads group). The CFUs population in the 950 + 300 rads group grew exponentially for 2 weeks at a rate which did not differ significantly from that of CFUs in the 0 + 300 rads group. However, the rate of CFUs growth reached a plateau before full recovery was achieved in contrast to that in the 0 + 300 rads mice. We therefore conclude that the incomplete regeneration of CFUs in the marrows of 950 + 300 rads mice was most likely caused by X-irradiation-induced damage to the HS rather than damage to the inherent repopulating potential of the CFUs per se.     

Early variations of host thyroxine and interleukin-7 favor Schistosoma mansoni development

Schistosoma mansoni induces, in the vertebrate host, cutaneous production of interleukin-7 (IL-7), which is beneficial for parasite establishment and development. Infection of mice deficient in IL-7 expression leads to parasite dwarfism. Because similar findings were previously described in hypothyroid mice, this study aimed to elucidate the potential link between IL-7 and thyroid hormones (THs), using several models including hypo- and hyperthyroid mice, modified either transiently or constitutively. Mice treated with thyroxine led to increased worm numbers and development of giant worms, whereas an iodine-deficient diet reduced parasite maturation, egg laying, and liver pathology. Conversely, mice genetically deficient for either of the nuclear TH receptors displayed normal worm development despite modifications in hormone levels, suggesting that thyroxine action is mediated through host receptors. In addition, no modification of antibody titers has been evidenced in thyroxine-treated mice, whereas antibody levels were altered in transgenic animals. These observations suggest that the immune system is not likely to be involved in the modifications of parasite development reported in this study. Interestingly, concomitant treatment with IL-7 and thyroxine had a synergistic effect, leading to recovery of very large worms, thus raising questions about the complexity of interactions between IL-7 and metabolic hormones.     

REGENERATION OF CFUs IN THE MARROW OF MICE EXPOSED TO 300 RADS AFTER HAVING RECOVERED FROM 950 RADS

Exposure to 950 rads ⁶⁰Co radiation has been reported to cause long-lasting damage to the hematopoietic stroma (HS), although the size of the CFUs population recovers to pre-irradiation levels. In these studies HS damage was detected only after subcutaneously implanting the femurs of the irradiated mice into syngeneic hosts. To exclude the possibility that what was considered to be HS damage was merely caused by artifacts due to the process of implantation in a new host, we compared the rate of regeneration of CFUs in mice which had recovered from 950 rads prior to receiving 300 rads ⁶⁰Co radiation (950 + 300 rads group) with that of mice which received only 300 rads (0 + 300 rads group). The CFUs population in the 950 + 300 rads group grew exponentially for 2 weeks at a rate which did not differ significantly from that of CFUs in the 0 + 300 rads group. However, the rate of CFUs growth reached a plateau before full recovery was achieved in contrast to that in the 0 + 300 rads mice. We therefore conclude that the incomplete regeneration of CFUs in the marrows of 950 + 300 rads mice was most likely caused by X-irradiation-induced damage to the HS rather than damage to the inherent repopulating potential of the CFUs per se.     

Attenuation of a radiation-induced conditioned taste aversion after the development of ethanol tolerance

An attempt to reduce a radiation-induced conditioned taste aversion (CTA) was undertaken by rendering animals tolerant to ethanol. Ethanol tolerance, developed over 5 days, was sufficient to block a radiation-induced taste aversion, as well as an ethanol-induced CTA. Several intermittent doses of ethanol, which did not induce tolerance but removed the novelty of the conditioning stimulus, blocked an ethanol-induced CTA but not the radiation-induced CTA. A CTA induced by doses of radiation up to 500 rads was attenuated. These data suggest that radioprotection developing in association with ethanol tolerance is a result of a physiological response to the chronic presence of ethanol not to the ethanol itself.     

Do mice genetically selected for resistance to oral tolerance provide selective advantage for Schistosoma mansoni infection?

A highly evolved relationship exists between the parasitic flatworm Schistosoma mansoni and its vertebrate hosts that include the use of host immune signals by parasites. The S. mansoni infection was studied in two strains of mice genetically selected, over 18 generations of assortative mating, for extreme phenotypes of susceptibility (TS) and resistance (TR) to immunological tolerance. The objective was to observe whether the different host genetic backgrounds affected the outcome of experimental schistosomiasis. Fecal egg excretion, tissue egg count, worm recovery, and adult worm morphology and morphometry were monitored throughout the period of infection. TR mice presented total fecal egg excretion and thickness of tegument in adult male worms significantly higher than TS mice. Therefore, the comparative analysis of mice with extreme phenotypes of immunological response turns out to be useful in host-parasite relationship studies. Our results suggest that the TR mouse immunological profile provides a more favorable environment for the development of S. mansoni.     

The Effect of Radiation-Induced Mutations on the Fitness of Drosophila Populations

The change in frequencies of D. melanogaster and D. simulans in competition experiments was used to measure the effect of radiation on the fitness of a population. A dose of 250 or 500 rads given to the males of highly inbred lines of D. simulans at the beginning of competition and every three weeks thereafter increased the relative frequency of the irradiated population. If the dose was increased to 1000 rads, the deleterious effects of radiation became too great a burden on the population, and the frequency of the irradiated population decreased. From these results it was concluded that below certain doses the introduction of radiation-induced mutations into a highly homozygous population would increase the fitness of the population.     

Regulation of cell-mediated cytotoxicity. II. Synergism of two types of thymus dependent cells in vivo.

Sublethal (500 rads) doses of radiation given to mice before the intravenous injection of allogeneic spleen cells induced the development of an increased cell-mediated cytotoxicity (CMC) of the recipients' spleen cells. The effector cells from the irradiated animals were shown to carry the θ alloantigenic marker and to be capable of transferring adoptive immunity in vivo. On the other hand, irradiation of mice with the same dose before the administration of skin or tumor allografts induced a suppression of CMC. The response of irradiated mice treated with tumor allografts was restored with small numbers of spleen or lymph node cells from syngeneic or semi-allogeneic F₁ hybrid donors. With the use of the appropriate cytotoxic alloantisera, it was demonstrated that the majority of the effector cells generated in the spleens of mice restored with semiallogeneic cells were of host origin. These results demonstrate that the precursors of the cytotoxic lymphocytes are radioresistant and indicate that for their stimulation some radiosensitive T cells are necessary to amplify their reaction to nonlymphoid allografts. Allogeneic lymphoid cells, on the other hand, supply a stimulus which does not require the intervention of such amplifier cells. In this case, irradiation induces a stronger CMC response probably by inactivating radiosensitive cells with suppressor activity.     

Isolation and partial characterization of an antigen shared between Schistosoma mansoni, Fasciola hepatica, and Biomphalaria glabrata

An antigen was isolated and partially characterized from adult Schistosoma mansoni which immunologically cross-reacted with Fasciola hepatica and Biomphalaria glabrata, a schistosome intermediate snail host. The antigen was isolated from a solubilized freeze-thaw preparation containing 0.5% Triton X-100 by passage through a CNBr-activated Sepharose 4B column coupled with rabbit IgG prepared against a homogenate of B. glabrata hepatopancreas. The eluted antigen (designated as SMw-53P) stained with Coomassie Brilliant Blue R250, but not with Nile Blue A or periodic acid-Schiff's stains. The antigen did not bind to a Concanavalin A affinity column. SMw-53P was determined to have a molecular weight of 53,000 daltons by SDS-polyacrylamide gel electrophoresis. Western blotting, using sera from mice infected with S. mansoni, revealed the presence of the antigen in whole worm preparations of both S. mansoni and F. hepatica. The serodiagnostic potential of the antigen was evaluated by ELISA utilizing sera from S. mansoni-infected mice, or rabbits injected with homogenates of F. hepatica or S. mansoni whole worm, or B. glabrata hepatopancreas. SMw-53P was shown to strongly react with all antisera, but not normal mouse or rabbit sera. These data suggest a limited value for the antigen for the specific immunodiagnosis of schistosomiasis mansoni, but do suggest a possible potential as a general screening tool for detecting trematode infections. Further studies regarding the antigen's potential as a vaccine are indicated.     

Bge snail cell-line antigens: ineffectiveness as antischistosomal vaccine in mice.

Mice and rabbits were immunized with antigens derived from Bge cells, Biomphalaria glabrata hemolymph, or Schistosoma mansoni. Antisera from mice given molluscan antigens did not form immunoprecipitates with soluble antigen from adult worms, but their binding to surfaces of sporocysts, cercariae, and schistosomules suggests the presence of cross-reacting determinants. In vitro, cell-mediated immune responses to Bge antigens were not demonstrable in infected nor in immunized mice. Mice immunized with Bge cell-line antigens and challenged with S. mansoni cercariae showed no reduction in worm burden when compared with control mice.     

Study of the mechanism of Corynebacterium parvum antitumour activity: Protective effect in mice submitted to sublethal doses of irradiation

Summary The antitumour activity of C. parvum against two different tumours, a lymphosarcoma grafted in XVII mice and a mammary carcinoma grafted in C₃H mice, was a radiosensitive phenomenon. A dose of X-rays as low as 100 rads was sufficient to abrogate the C. parvum-induced protection. The duration of this inhibition increased with augmentation of the X-ray dose. The stimulation of macrophage-phagocytic activity induced by C. parvum was not inhibited by a dose of 500 rads. A chronological parallelism has been demonstrated in the recovery of the C. parvum antitumour effect and the restoration of antibody responsiveness after the suppression of these two activities by 500 rads of X-rays in the case of the C₃H mice grafted with mammary carcinoma cells. No such concomitant recovery has been observed in XVII mice. In these mice, the recovery of C. parvum antitumour activity took place before the restoration of antibody responsiveness.