Worm Reduction Rate Research Articles

Development of a Streptococcus gordonii vaccine strain expressing Schistosoma japonicum Sj-F1 and evaluation of using this strain for intranasal immunization in mice

Schistosomiasis is a worldwide parasitic disease. Currently, chemotherapy is the main effective method to treat schistosomiasis; however, it does not prevent reinfection. No effective vaccine is currently available to prevent schistosomiasis. Sj-F1 (GenBank accession number AY261995) is a novel gene that was discovered through screening adult Schistosoma japonicum worm cDNA library with female S. japonicum antigen-immunized sera. Streptococcus gordonii, a normal inhabitant of the human oral cavity, has been a prime candidate in recent investigations toward developing a live oral vaccine vector. One of the approaches for the surface expression of heterologous antigens in S. gordonii is to surface-localize them with the M6 protein from Streptococcus pyogenes. Here, we develop a recombinant S. gordonii strain that expresses the M6-Sj-F1 fusion protein on the bacterial surface. Intranasal immunization in mice with such M6-Sj-F1-expressing S. gordonii bacteria induced strong serum IgG, serum IgA, and saliva IgA against Sj-F1. The results of protective immunity against a challenge with cercariae of S. japonicum showed statistically significant protection following this treatment, with a worm reduction rate of 21.45% and an egg reduction rate of 34.77%. Our data indicate that the described M6-Sj-F1-expressing S. gordonii is highly immunogenic and can partially protect mice from challenge infection with S. japonicum. Intranasal immunization with recombinant S. gordonii may be an alternative to developing a novel S. japonicum vaccine in a safe, effective, and feasible way.

Efficacy of tribendimidine against Angiostrongylus cantonensis infection in the mice

Angiostrongyliasis, also known as eosinophils meningitis, is caused by Angiostrongylus cantonensis parasites in the human central nervous system. Currently, the drug of choice for treatment of angiostrongyliasis is albendazole, but dead worm lysis causes severe inflammatory response, which leads to central nervous system damage. Tribendimidine, a broad-spectrum anti-helmintic drug developed in China, is a derivative of amidantel. This study was designed to test the efficacy of tribendimidine against A. cantonensis in mice. We treated 65 infected female BALB/c mice with tribendimidine or albendazole by oral route. We observed that tribendimidine at doses of 50, 100 and 200mg/kg/day was effective, and the worm reduction rates were 54.8%,77.4%, and 100% compared with the control group. In addition, the therapeutic effect of early tribendimidine treatment (7days post-infection [PI]) was better than the late treatment (14days PI), in comparison with the albendazole group (20mg/kg/day). The index of therapeutic efficacy included body weight, neurological function, survival time, worm reduction, mRNA levels of proinflammatory cytokines in brain tissue, histopathological examination and electron microscopy scanning. The results showed that tribendimidine could kill the larvae of A. cantonensis in the mice model, and the worm's body wall was observed to be damaged. After treatment with tribendimidine, the survival conditions such as body weight and neurological function were improved, and brain inflammation was reduced in infected mice. This study showed a strong efficacy of tribendimidine against A. cantonensis and provided suitable alternative treatments to further explore its potential use in treatment of human angiostrongyliasis.

Identification and Characterization of Paramyosin from Cyst Wall of Metacercariae Implicated Protective Efficacy against Clonorchis sinensis Infection

Human clonorchiasis has been increasingly prevalent in recent years and results in a threat to the public health in epidemic regions, motivating current strategies of vaccines to combat Clonorchis sinensis (C. sinensis). In this study, we identified C. sinensis paramyosin (CsPmy) from the cyst wall proteins of metacercariae by proteomic approaches and characterized the expressed recombinant pET-26b-CsPmy protein (101 kDa). Bioinformatics analysis indicated that full-length sequences of paramyosin are conserved in helminthes and numerous B-cell/T-cell epitopes were predicted in amino acid sequence of CsPmy. Western blot analysis showed that CsPmy was expressed at four life stages of C. sinensis, both cyst wall proteins and soluble tegumental components could be probed by anti-CsPmy serum. Moreover, immunolocalization results revealed that CsPmy was specifically localized at cyst wall and excretory bladder of metacercaria, as well as the tegument, oral sucker and vitellarium of adult worm. Both immunoblot and immunolocalization results demonstrated that CsPmy was highly expressed at the stage of adult worm, metacercariae and cercaria, which could be supported by real-time PCR analysis. Both recombinant protein and nucleic acid of CsPmy showed strong immunogenicity in rats and induced combined Th1/Th2 immune responses, which were reflected by continuous high level of antibody titers and increased level of IgG1/IgG2a subtypes in serum. In vaccine trials, comparing with control groups, both CsPmy protein and DNA vaccine exhibited protective effect with significant worm reduction rate of 54.3% (p<0.05) and 36.1% (p<0.05), respectively. In consistence with immune responses in sera, elevated level of cytokines IFN-γ and IL-4 in splenocytes suggested that CsPmy could induce combined cellular immunity and humoral immunity in host. Taken together, CsPmy could be a promising vaccine candidate in the prevention of C. sinensis regarding its high immunogenicity and surface localization.

The investigation of protective concomitant immunity in murine schistosomiasis mansoni

The present study was conducted mainly to establish a new concomitant immunity model to Schistosoma mansoni in mice and assess its effects on the resistance of mice to a challenge infection with a possibility of using as a diagnostic marker. Three groups (A, B and C) of BALB/c mice were infected with a single dose of S. mansoni cercariae obtained from infected Biomphalaria glabrata snail. The group A mice were used as infected control group. The group B mice were intraperitoneally injected with allylthiourea (ATU) 22 days post-primary infection then they were challenged 3 weeks post-ATU treatment. The group C mice were challenged with the same number of cercariae 6 weeks post-primary infection. Perfusion of all mice was done 9 weeks after infection in order to obtain worm burdens. The livers of all mice were obtained for parasitological and pathological assessments. Our results showed that the group B mice had a 29.11% worm reduction rate, 25.37% liver egg reduction rate, and 37.48% granuloma size reduction rate compared to their respective controls. While the group C mice showed superior results and had a 54.66% worm reduction rate, 41.45% liver egg reduction rate, and 51.76% granuloma size reduction rate. It was concluded that these results described novel imaging methods that permit visualization of live schistosomes within their living hosts and may have important implications not only for epidemiological and diagnostic investigations, but also in designing control programs for schistosomiasis including anti-schistosome vaccine.

Identification and molecular characterization of a novel signaling molecule 14-3-3 epsilon in Clonorchis sinensis excretory/secretory products

Increasing evidence shows that 14-3-3 proteins are involved in many biology events in addition to signal transduction. Extensive investigations on structural and biochemical features of these signaling molecules have implied their importance in the biological process. In the present study, we have identified and characterized the 14-3-3 epsilon (Cs14-3-3) in Clonorchis sinensis that causes human clonorchiasis. Recombinant protein was expressed in Escherichia coli (E. coli) and identified by MALDI-TOF/TOF. Immunoblot results revealed that Cs14-3-3 was a component of excretory/secretory products. Ligand blot assay indicated that 14-3-3 epsilon could bind C. sinensis MAPKAPK 2 in a nonphosphorylation-dependent manner. This protein could be detected at four stages of the life cycle by RT-PCR experiments and immunolocalization showed that Cs14-3-3 was extensively distributed in C. sinensis, especially at the outer surface and the sucker of adult worm and cyst wall of metacercaria. Taken together, 14-3-3 epsilon might play some roles in the development of the parasites. In addition, Cs14-3-3 epsilon should be addressed for the diagnostic value in C. sinensis infection in consideration of high sensitivity and specificity. As an immune stimulus, C. sinensis 14-3-3 epsilon was found to provoke a Th1/Th2 balanced immune response by inducing high levels of both IgG1 and IgG2a. Recombinant Cs14-3-3 conferred effective protection both in worm reduction rate and egg reduction rate, suggesting that the signaling molecule Cs14-3-3 was a promising vaccine candidate against C. sinensis infection.

IL-18 enhances protective effect in mice immunized with a Schistosoma japonicum FABP DNA vaccine

Two recombinant plasmids, pVAX/SjFABP and pVAX/mIL-18 containing Schistosoma japonicum 14 kDa fatty acid binding protein (SjFABP) and murine IL-18, were constructed and evaluated for their ability to induce immune responses and to protect against S. japonicum challenge in mice. Mice were intramuscularly immunized twice at three-weekly intervals, and challenged with S. japonicum cercariae at 4 weeks after the last vaccination. All animals vaccinated with pVAX/SjFABP alone or plus pVAX/mIL-18 developed specific anti-SWAP ELISA antibody and T lymphocyte proliferation. Co-injection of pVAX/mIL-18 significantly increased the production of IFN-γ and IL-2 compared with pVAX/SjFABP alone, indicating that IL-18 enhances the Th1-dominant immune response. The challenge experiment showed that co-injection of plasmid encoding IL-18 significantly enhances protective effect against S. japonicum infection, as demonstrated by worm reduction rates and the hepatic egg reduction rates 45 days post-challenge. These results indicated that IL-18 may become a novel vaccine adjuvant for development of vaccines against schistosomiasis.

Expression profile, localization of an 8-kDa calcium-binding protein from Schistosoma japonicum (SjCa8), and vaccine potential of recombinant SjCa8 (rSjCa8) against infections in mice

Researches on genes expressed in a cercarial stage-specific manner may help us understand the molecular events and functions during schistosome invasion of skin. A genomic clone encoding 8-kDa calcium-binding protein (SjCa8) specifically expressed in cercariae and skin-stage schistosomulum (transformed within 3 h) was obtained from cercariae. Recombinant protein was expressed in vector pET32a (+) and purified using a Ni-NTA purification system. The target protein SjCa8 was determined by matrix-assisted laser desorption/ionization time-of-flight (TOF)/TOF mass spectrometer after thrombin digestion and dialysis. Reverse transcriptase polymerase chain reaction and Western blot revealed SjCa8 can be detected in cercaria and skin-stage schistosomulum but not lung-stage schistosomulum, adult, or egg and was localized to head gland, penetration gland tubes, and penetration glands where Ca(2+) was abundant, and the cercarial tegument (but not tegument of tail) and body-tail junction. Furthermore, SjCa8 was interestingly detected in cercarial secretions. The characterization of SjCa8 indicated that it may undergo structural and physiological modifications, including repair of the surface membrane, changes in permeability that account for the loss of water tolerance, activities of calcium-depending enzymes, and immune signaling, etc. Furthermore, vaccination with rSjCa8 plus adjuvant induced protective effect with 50.39% worm reduction rate and significantly high hepatic and intestine egg reduction rates (54.16%, 50.63%, respectively), which is possibly mediated through an apparent induction of Th1-type immune response for strikingly high level of IgG2a and IgG2b developed in immunized C57BL/6 mice.

Vaccination against &amp;lt;italic&amp;gt;Schistosoma japonicum&amp;lt;/italic&amp;gt; Infection by DNA Vaccine Encoding Sj22.7 Antigen

To observe the in vitro expression of DNA vaccine pcDNA3-Sj22.7 and its immunological effect in mice, the recombinant plasmid pcDNA3-Sj22.7 was used to transfect HeLa cells with liposome-mediated method and the expression of Sj22.7 mRNA and protein was examined using reverse transcription-polymerase chain reaction, sodium dodecylsulfate-polyacrylamide gel electrophoresis and Western blot. Then, the ability of pcDNA3-Sj22.7 to protect against Schistosoma japonicum challenge infections was analyzed according to worm reduction rate and egg reduction rate after vaccination of mice. The serum levels of specific IgG antibody and T lymphocyte proliferation response were also determined. After the challenge infection, Sj22.7-driven interferon (IFN)-gamma and interleukin (IL)-4 was also quantified. Results showed that pcDNA3-Sj22.7 could express Sj22.7 mRNA and protein in vitro. Immunization resulted in a worm reduction rate of 29.70%, egg reduction rate of 47.25% (liver) and 51.73% (intestine), and egg reduction rate of 25.90% (eggs per female), suggesting induction of significant anti-fecundity in the pcDNA3-Sj22.7 group. Enzyme-linked immunosorbent assay and Western blot analysis indicated that immunized mice generated specific IgG against Sj22.7. T lymphocytes from mice immunized with pcDNA3-Sj22.7 showed a significant proliferation response to rSj22.7. The culture of spleen cells showed that secretion of IFN-gamma increased but IL-4 decreased. The results indicate hat DNA vaccination by pcDNA3-Sj22.7 is sufficient to elicit significant levels of protective immunity against S. japonicum infection. The DNA vaccine could induce significant cellular and humoral immune response, and display predominant T helper cell type 1 type immune responses, which contribute to the protective immunity against challenge infection in mice.

Influence of immunization dose schemes on immunoprotective response to recombinant signaling protein 14-3-3 of Schistosoma japonicum

To discuss the optimal immunization dose by observing the immunoprotective effects of different doses of recombinant Schistosoma japonicum (Chinese strain) signaling protein 14-3-3 (rSj14-3-3). Sj14-3-3 gene was amplified by reverse transcriptase PCR (RT-PCR), subcloned into prokaryotic expression vector pET28a, then transformed into E.coli to express by inducing. Purified rSj14-3-3 was prepared through SDS polyacrylamide gel electrophoresis (SDS-PAGE), electroelution, dialysis, then BALB/c mice were divided into 5 groups and immunized in rSj14-3-3 protein followed by challenging infection (the 1st, 2nd, and 3rd groups were immunized in 50 microg, 100 microg and 300 microg antigen, respectively. The 4th, 5th groups were immunized in Freund's adjuvant and normal saline controls). After 6 weeks of challenging infection, the mice were killed and the worm and egg reduction rates were calculated. And the mice sera in different time were taken to examine the specific anti-Sj14-3-3 IgG. rSj14-3-3 protein was expressed successfully. After immunizing and challenging, worm reduction was found to be 28.20% in the 1st group, 43.10% in the 2nd group, 40.00% in the 3rd group, respectively. Number of eggs in liver tissue was reduced by 41.80%, 57.50%, 55.70%, respectively. Compared the results of the tested groups to the controls, the differences were of significance by t-test (worm reduction rate: t = 6.8 in the 1st group, t = 8.7 in the 2nd group, t = 7.3 in the 3rd group, P < 0.01 in all tested groups. Egg reduction rate at the group's number above: t = 11.23, t = 11.54, t = 7.99, P < 0.01 in all tested groups). As compared the results between the tested groups by chi(2), the differences were of significance between the 1st and the 2nd groups (worm reduction rate: chi(2) = 8.96, P < 0.05; egg reduction rate: chi(2) = 15.69, P < 0.05), between the 1st and the 3rd groups, the differences were also of significance (worm reduction rate: chi(2) = 6.52, P < 0.05; egg reduction rate: chi(2) = 12.52, P < 0.05). The difference was not of significance between the 2nd and the 3rd groups (worm reduction rate: chi(2) = 1.20, P > 0.05; egg reduction rate: chi(2) = 0.93, P > 0.05). In all tested groups, total anti-Sj14-3-3 specific IgG rose markedly. IgG(1) and IgG(2a) subtypes were high, but IgG(2b) and IgG(3) were near the background in four subtypes tested. Immunoprotection of rSj14-3-3 should have some relations with immunization dose, and the protection obtained from immunizing mice by using 100 microg antigen was the best.

Vaccination of mice with recombinant nucleic acid vaccine encoding the integral membrane protein Sj23 and cytokine IL-12 elicits specific immune responses against schistosoma japonica

To develop a Schistosoma japonica integral membrane protein Sm23 or Sj23 combined with murine IL-12 DNA-base vaccine against schistosomiasis. Plasmids pVIVO2-Sj23 and pVIVO2-IL12-Sj23, expressing the integral membrane protein Sj23 of Schistosoma japonica and/or murine IL-12 were constructed. The plasmid pVIVO2-IL12-Sj23 was transfected into the human embryonic kidney cells of the line 293. RT-PCR was used to detect the expression of Sj23 mRNA in the 293 cells. Indirect immunofluorescence test was used to detect the expression of Sj23 protein. Fifty BALB/c mice were randomly divided into 5 equal groups to be injected with pVIVO2-IL12-Sj23 plasmid DNA, pVIVO2-Sj23 plasmid DNA, pVIVO2-IL12 plasmid DNA, pVIVO2 blank vector, and normal saline respectively into the quadriceps muscle of thigh. Four weeks after each mouse were infested with 40 +/- 2 cercariae of Schistosoma japonica. Six weeks after the infestation the mice were killed to calculate the load of schistosoma and the amount of eggs per gram (EPG) of liver so as to calculate the worm reduction rate and egg reduction rate after the vaccination. Before immunization, 4 weeks after immunization, and 6 weeks after immunization blood samples were collected from the caudal veins of mice. With soluble egg antigen (SEA) and adult worm antigen (AWA) ELISA was used to detect the serum IgG level. Western blotting was used to detect the serum specific anti-Sj23 IgG level. Six weeks after the cercaria challenge single splenocyte suspension was prepared. Splenocytes were cultured with SEA, and concanavalin A (ConA). ELISA was used to detect the levels of IL-4 and IFN-gamma in the supernatant. Flow cytometry was used to analyze the subgroups of splenocyte. + Forty-eight hours after the transfection, RT-PCR and indirect immunofluorescence test showed expression of Sj23 mRNA and protein in the HEK-293 cells. The worm reduction rate was 45.53% and the egg reduction was 58.35% in the pVIVO2-IL12-Sj23 group, significantly higher than those in the monovalent vaccine pVIVO2-Sj23 group (27.23% and 33.93% respectively, both P <0.05). ELISA and Western blotting analysis showed that the level of IgG specific for Sj23 significantly increased 4 weeks after vaccination in the pVIVO2-IL12-Sj23 and pVIVO2-Sj23 groups without significant difference between these 2 groups (P > 0.05). After stimulation of ConA and SEA the level of Th1 type cell factor IFN-gamma was higher and the level of the Th2 type cellular factor IL-4 was low in the supernatant of suspension of splenocytes of the pVIVO2-IL12-Sj23 group. FCM showed the percentages of CD4+ and CD8+ subgroups of the murine splenocytes of all experimental groups were all significantly lower than those of the normal mice (all P < 0.001 approximately 0.02). However, there was no significant difference in the CD4+/CD8+ ratio among the experimental groups (all pVIVO2-IL12-Sj23 is sufficient to elicit significant levels of protective immunity against Schistosoma japonica challenge infection. IL-12, a cytokine and a gene adjuvant, is able to induce Th1 responses and hence the protective immunity.

The protective effect of a Schistosoma japonicum Chinese strain 23 kDa plasmid DNA vaccine in pigs is enhanced with IL-12

The schistosome integral membrane protein Sm/Sj23 was initially shown to induce protection in mice as a synthetic peptide vaccine and further, as a plasmid DNA vaccine to induce protection in mice, sheep and water buffalo. In this study we asked if we could induce protection against challenge infection in pigs against Schistosoma japonicum by vaccinating them with a plasmid DNA vaccine encoding the S. japonicum Chinese strain 23 kDa membrane protein. Further, we asked if we could enhance protective efficacy of this vaccine by the addition of IL-12. We compared vaccination with SjC23 plasmid DNA alone or with IL-12 plasmid DNA in pigs. Pigs were immunized three times at three weekly intervals. Thirty Chinese Songjang native pigs were divided into three groups. In group A, each pig was immunized with 500 μg of SjC23 plasmid DNA by intramuscular (i.m.) injection in both buttocks. In group B each pig was immunized with 500 μg of SjC23 plasmid DNA, and 500 μg of each of pcDNA3.1-p35 and 500 μg of pcDNA3.1-p40 DNA by i.m. injection. In group C each pig was immunized with 500 μg of pcDNA3.1 as the control. Thirty days post-vaccination, pigs were challenged with S. japonicum cercariae and adult and egg burdens and granuloma size determined 45 days post-challenge. The results showed that worm reduction rates in SjC23 group compared with control group were 29.2% and in the SjC23 + IL-12 group reduced 58.6%. Similarly the female worm reduction rates were 50.8 and 58.8%, the hepatic egg reduction rates were 48.2 and 56.4%, and the mean square measure reduction rates of hepatic egg granulomas were 48.6 and 44.4%, the mean diameter reduction rates of granulomas were 27.6 and 22.8% in pigs vaccinated with SjC23 or SjC23 + IL-12 compared to plasmid vaccinated pigs, respectively. Analysis of sera from pigs vaccinated with SjC23 showed that 4 of 10 pigs had anti-Sj23 antibody responses; with 5 of 10 pigs positive for anti-Sj23 in the SjC23+IL-12 group. These results suggest that vaccination with Sj23 DNA vaccine induces not only a significant reduction in worm and egg burdens, but also significantly reduces the size of egg granulomas, thus is also anti-pathology.

Effect of combined treatment with praziquantel and artemether on Schistosoma japonicum and Schistosoma mansoni in experimentally infected animals

Praziquantel and artemether are safe and efficacious antischistosomal drugs that act against different developmental stages of the parasite: praziquantel against adult worms and artemether against schistosomula. A combined treatment has been suggested as a strategy for transmission control. Recent laboratory experiments with rabbits with a mixed infection of Schistosoma japonicum parasites of different ages confirmed the effectiveness of a combination therapy. In the present work, we assessed the effect of a combined treatment on adult worms of S. japonicum and found significantly higher worm reduction rates than with a single dose of praziquantel. In a next step, we extended the study of the combined treatment to Schistosoma mansoni. A combined treatment with 75 mg/kg praziquantel and 150 mg/kg artemether was administered to hamsters infected with juvenile and adult S. mansoni. The two drugs, administered simultaneously or spaced by 6 h, 1, 3 or 7 days, resulted in significantly higher worm reduction rates than a single treatment with praziquantel. A combination therapy with increased doses of 100 mg/kg praziquantel and 300 mg/kg artemether showed very high worm reduction rates of 90% and above, however, some hamsters died in five different combined treatment experiments, suggesting that these drug concentrations were too high. We conclude that a combined treatment with praziquantel and artemether at the lower doses is safe and more effective than praziquantel alone, which forms a foundation for designing respective clinical trials in humans.

Effect of artemether against Schistosoma haematobium in experimentally infected hamsters

The drug, artemether, has been shown to be active against the juvenile stages of Schistosoma japonicum and Schistosoma mansoni in experimentally infected animals, while it is less effective on adult worms. These findings have been confirmed in randomised controlled trials in humans. Consequently, it could be expected that artemether is also active against Schistosoma haematobium. We present here the first results from experiments assessing the effect of artemether on S. haematobium. Hamsters with a single infection received intra-gastrically an initial dose of 300 mg/kg artemether on day 14, 21 or 28, followed by further doses at varying treatment regimens. In all the treatment groups, the total and female worm reduction rates were highly significant, and ranged from 78 to 100% in hamsters harbouring juvenile schistosomes. Hamsters infected three times with S. haematobium, on days 0, 4 and 9, and repeatedly treated with artemether at the same dose as above, showed highly significant total and female worm reduction rates of between 94 and 99%. Artemether was also active against 77-day-old adult S. haematobium, since its administration on two consecutive days resulted in highly significant total and female worm reduction rates of 76–89%. Our findings confirm that artemether is also active against S. haematobium, especially the schistosomules. These results provide a basis for clinical trials in humans, for further assessment of the potential of artemether for schistosomiasis control.

Anthelmintic effect of levamisole against Angiostrongylus cantonensis in mice.

Levamisole, in dosages of 2.5, 5, 10, and 25 mg/kg/day, was given orally by orogastric tube beginning 5, 10, 15, and 20 days after the infection of ICR mice with 50 third-stage larvae of Angiostrongylus cantonensis. Medication was given for 7, 14 or 21 consecutive days. The mice in each group were sacrificed 3 days after cessation of treatment and the brains were examined for parasites. Complete anthelmintic effects could be obtained when treatment was started 10 days post-infection with dosages as low as 2.5 mg/kg/day for 21 consecutive days. Over 90% worm reduction was achieved in the two-week treatment group with medication beginning 5 days after infection at diverse dosages. High dose were given in the treatment groups beginning 15 days post-infection. When the commencement of medication was delayed to 20 days post-infection, worm reduction rates were around 50% in spite of long periods and/or high dosages of medication.

Plasma Pharmacokinetics and Therapeutic Efficacy of Praziquantel and 4-Hydroxypraziquantel in Schistosoma japonicum-Infected Rabbits after Oral, Rectal, and Intramuscular Administration

The relationship between plasma level and therapeutic efficacy of praziquantel (PZQ) and its major human oxidative metabolite, 4-hydroxypraziquantel (4-OHPZQ), has been investigated in Schistosoma japonicum-infected rabbits using three different routes of PZQ administration. After intramuscular administration (20 mg/kg), the maximum level of PZQ in rabbit cardiac plasma was 1.6 +/- 1.0 micrograms/ml (mean +/- SD) 30 min after administration. After oral or rectal administration (40 mg/kg), maximum plasma levels were 0.1 +/- 0.2 microgram/ml (oral) and 0.5 +/- 0.4 micrograms/ml (rectal). The corresponding maximum 4-OHPZQ concentrations in cardiac plasma were 4.6 +/- 1.8 micrograms/ml (intramuscular), 1.7 +/- 0.5 micrograms/ml (oral), and 4.1 +/- 1.6 micrograms/ml (rectal) 2 hr after administration of PZQ. After administration of similar doses, maximum levels of PZQ in plasma from the femoral vein were 29.3 +/- 27.5 micrograms/ml (intramuscular), 0.6 +/- 1.0 microgram/ml (oral), and 0.7 +/- 0.6 microgram/ml (rectal). However, 60 min after intramuscular administration, the maximum PZQ concentration in portal venous blood was only 1.0 +/- 0.6 microgram/ml, which is substantially less than corresponding maximum portal vein levels after oral (6.8 +/- 6.5 micrograms/ml) or rectal (3.7 +/- 4.6 micrograms/ml) administration. Therapeutically, in spite of the 4-6-fold lower levels of PZQ in portal venous plasma after intramuscular administration, adult worm reduction rates in infected rabbits using the above doses were 92.2% (intramuscular), 90.1% (rectal), and 72.5% (oral), respectively, four weeks after treatment. Thus, no direct correlation between levels of PZQ in peripheral or portal venous blood and therapeutic efficacy was observed in rabbits infected with S. japonicum.

In vitro and in vivo studies of the effect of artemether on Schistosoma mansoni

To determine whether artemether, a derivative of the antimalarial agent qinghaosu, is therapeutically active against Schistosoma mansoni, we determined the in vitro, in vivo, and histopathologic effects of the drug on S. mansoni worms. In vitro, toxic effects of artemether on S. mansoni were not seen at concentrations of less than 100 micrograms/ml. However, in vivo, 30 and 50% reductions in the lengths of male and female worms, respectively, were observed 14 days after treatment. By 56 days worm dimensions had returned to control values. Similar reversible effects on male testes and female ovaries were seen. In vivo, a single oral dose of artemether (300 mg/kg) induced a shift of worms towards the liver within 8 h after treatment. By 3 and 14 days after treatment, 99 and 76%, respectively, of worms were still in the liver. In vivo, the therapeutic effect of artemether on adult S. mansoni treated on day 56 after infection was modest. Doses as high as 1,200 mg (200 mg/kg per day, six doses) resulted in a worm reduction rate of only 39%. However, in infected mice treated on day 14 or 21 after infection, worm reduction rates of 83 to 98% were obtained. Thus, artemether exhibited modest in vitro and in vivo activities against adult S. mansoni but was twofold more active against 2- to 3-week-old liver-stage parasites.

Larvicidal effect of albendazole against Angiostrongylus cantonensis in mice.

Mice were infected with 50 third stage larvae of Angiostrongylus cantonensis and treated orally with albendazole (Zentel) in dosages of 5, 10, and 25 mg/kg/day begun 5, 10, or 15 days post-infection for 7, 14, or 21 consecutive days. The mice in each group were killed 3 days after cessation of treatment and the brains examined for parasites. Worms were recovered from the brains of all mice treated for 7 days, but recoveries from treated mice were significantly lower than from controls. Worm reduction was nearly 100% in mice treated for 14 days when treatment was initiated 5 and 10 days post-infection. Worms were found in the brain of mice treated for 14 days when treatment began at 15 and 20 days, but recovery rates were significantly lower than in controls. Similar results were obtained in animals treated for 21 days. Worm reduction rates were lower in animals given 5 mg/kg/day, but there was no significant difference in animals given higher dosages. Albendazole was effective in the treatment of A. cantonensis in mice when given within 15 days post-infection.

Axenomycins, new cestocidal antibiotics.

Axenomycins are a new group of macrolide antibiotics isolated from the fermentation broth of Streptomyces lisandri n.sp. They exhibit anthelmintic activity against tapeworms (Cestoda). Three different fractions, A, B, and D, have been obtained, the most active fraction being axenomycin D. The activities of the axenomycin complex and axenomycin D against Hymenolepis nana in mice, Taenia pisiformis, Dipylidium caninum, and Diphyllobothrium sp. in dogs, and Moniezia expansa, M. benedeni, and Avitellina centripunctata in lambs were studied in experimentally and naturally infected animals. Axenomycins were effective and well tolerated by the oral route. Worm reduction rates after a single oral dose were 90 to 100% with 5 to 10 mg of axenomycin D/kg and 50 to 100% with 20 mg of axenomycin complex/kg.