Protective effect of severe magnesium deficiency on Plasmodium chabaudi infection

Mice were fed for 30 days on purified diets containing 50 (severely Mg deficient diet), 100 (moderately Mg deficient diet) and 1300 mg/kg (control diet). An additional group raised on stock UAR diet was also used for the experiment. The mice were maintained on the experimental diets for 12 days before being inoculated with P. chabaudi. Infection evolved similarly in mice fed the control purified diet, moderately Mg deficient diet and the stock diet whereas the severely Mg deficient diet induced a 50% decrease in malarial infection as shown by the decrease in the percentage of parasitized red blood cells (RBC). In control mice, RBC Mg values increased significantly during P. chabaudi infection; however RBC Mg values were significantly lower in Mg-deficient than in control animals.     

Anti-thymocyte serum effects on Plasmodium berghei infection in rats

Rabbit anti-rat thymocyte serum (ATS) virtually abolished the innate resistance mechanism(s) of rats of different ages to primary infection with Plasmodium berghei. ATS apparently produced its immunosuppressant effect without arresting humoral antibody production as judged by agar-gel double diffusion tests. These results, when considered together with those of other workers, suggest that cell-mediated immunity is substantially involved in resistance to P. berghei.     

Anti-inflammatory, antioxidant and hepatoprotective effects of Thunbergia laurifolia Linn. on experimental opisthorchiasis

Thunbergia laurifolia Linn (Rang Chuet) possesses antioxidant and anti-inflammatory properties as well as anticancer activities. The aim of the present study was to evaluate the efficacy of T. laurifolia in reducing inflammation from pathological changes in Syrian hamsters infected with the human liver fluke Opisthorchis viverrini. Hamster groups were also administered N-nitrosodimethylamine (NDMA) and treated with T. laurifolia. Light microscopic observation of histopathological changes, liver function tests for alanine transaminase (ALT) and alkaline phosphatase (ALP) and kidney function tests for blood urea nitrogen (BUN) and creatinine were performed. Antioxidant effects of both fresh and dried Rang Chuet solutions were observed. Analysis of the histopathological changes showed anti-inflammatory properties, both in the case of O. viverrini infection or with NDMA administration, by reducing the aggregation of inflammatory cells surrounding the hepatic bile ducts as indicated by normal serum ALT, ALP, BUN and creatinine levels in treated Syrian hamsters. The present study found that fresh and dried Rang Chuet solutions clearly reduced the inflammatory cells in both O. viverrini-infected and NDMA-administered groups and was correlated with the total antioxidant capacity. These findings suggest that T. laurifolia possesses antioxidant and anti-inflammatory properties and that its application may be useful for prevention of the inflammatory process, one of the risk factors of O. viverrini-associated cholangiocarcinoma (CCA).     

A combination of praziquantel and the traditional medicinal plant Thunbergia laurifolia on Opisthorchis viverrini infection and cholangiocarcinoma in a hamster model

Cholangiocarcinoma (CCA) associated by Opisthorchis viverrini remains a health problem in Southeast Asia including Thailand. At present, there is still no efficient treatment for CCA. Thunbergia laurifolia is a traditionally used medicinal plant; its aqueous leave extract possesses the antioxidant activity and anti-inflammatory on hamster opisthorchiasis had been reported previously. Here, we demonstrate the combined effects of the T. laurifolia extract plus antihelminthic drug, praziquantel (PZ) on hamsters with opisthorchiasis and hamsters with opisthorchiasis related-cholangiocarcinoma through light microscopic observations of histopathological changes, as well as liver function tests for alanine transaminase (ALT) and alkaline phosphatase, and kidney function tests for blood urea nitrogen and creatinine. Results showed T. laurifolia extract combined with praziquantel reduced inflammatory cell aggregation and inhibiting CCA development, which were correlated to the serum ALT level. These present studies suggest that administration of T. laurifolia after praziquantel treatment clearly improve the hepatobiliary system and could reduce the risk of subsequent CCA development in human.     

Protective immunity against Plasmodium berghei malaria after administration of interleukin-12

Interleukin-12 (IL-12) has been shown to induce protection in mice against Plasmodium cyanomolgi and in rhesus monkey against Plasmodium yeolii. This study is to investigate whether recombinant IL-12 can induce protection in BALB/c mice against Plasmodium berghei. Five mice were given intraperitoneal injection of 7.5 micrograms/kg body weight recombinant mouse IL-12 two days prior to challenge with 5 x 10(4) of P. berghei, while mice in the control group were injected with 0.5 ml of normal saline prior to challenge. In both groups, the parasitaemia appeared on the fourth day after the infection. There was a slight reduction in the parasite burden in mice given IL-12 and the mice also survived longer compared to controls. Statistical significance of the difference could not be determined due to the small sample size. Nevertheless, the results of the study suggested that IL-12 may be able to protect mice against P. berghei infection.     

Synergistic effect of aqueous extract of Telfaria occidentalis on the biological activities of artesunate in Plasmodium berghei infected mice

Background

Resistance to most antimalarial drugs has encouraged the use of herbal preparations along with prescribed orthodox drugs.

Objective

To investigate effect of co-administration of aqueous extract of T. occidentalis leaves; commonly used as antimalarial and haematinic agent in Nigeria and artesunate using P. berghei animal model.

Methods

In vivo curative antiplasmodial effect of T. occidentalis (200mg/kg) alone and combination with artesunate (2mg/kg) were evaluated using albino mice infected with 10⁶ parasitized erythrocytes of P. berghei intraperitoneally. The haematological parameters: haemoglobin level, red blood cells and white blood cells and packed cell volume were monitored using standard methods.

Results

Aqueous extract of T. occidentalis, artesunate and the combination gave 72.17±4.07%, 70.43± 4.27% and 85.43±3.65% reduction in parasitaemia after 48hours respectively. A significant enhancement of the PCV was obtained with the coadministration of artesunate and aqueous extract (p< 0.01). Similar trends were also observed with heamatological parameters at 72hours of administration.

Conclusion

This study revealed a synergistic effect of the co-administration on parasite clearance rate of P. berghei infection in mice, with a significant enhancement of haematological parameters within 48 hours of administration. This indicates a rapid rate of recovery from plasmodial infections with the co-administration.     

Synergistic effect of aqueous extract of Telfaria occidentalis on the biological activities of artesunate in Plasmodium berghei infected mice

Background

Resistance to most antimalarial drugs has encouraged the use of herbal preparations along with prescribed orthodox drugs.

Objective

this study investigated effect of co-administration of aqueous extract of T. occidentalis leaves, commonly used as antimalarial and haematinic agent in Nigeria, and artesunate using P. berghei animal model.

Methods

In vivo curative antiplasmodial effect of T. occidentalis (200mg/kg) alone and in combination with artesunate (2mg/kg) were evaluated using albino mice infected with 10⁶ parasitized erythrocytes of P. berghei intraperitoneally. The haematological parameters: haemoglobin level, red blood cells and white blood cells and packed cell volume were monitored using standard methods.

Results

Aqueous extract of T. occidentalis, artesunate and the combination gave 72.17±4.07%, 70.43± 4.27% and 85.43±3.65% reduction in parasitaemia after 48hours respectively. A significant enhancement of the PCV was obtained with the co-administration of artesunate and aqueous extract (p < 0.01). Similar trends were also observed with heamatological parameters at 72 hours of administration.

Conclusion

This study revealed a synergistic effect of the co-administration on parasite clearance rate of P. berghei infection in mice, with a significant enhancement of haematological parameters within 48 hours of administration. This indicates a rapid rate of recovery from plasmodial infections with the co-administration.     

Prevention of experimental cerebral malaria by Flt3 ligand during infection with Plasmodium berghei ANKA

Dendritic cells are the most potent antigen-presenting cells, but their roles in blood-stage malaria infection are not fully understood. We examined the effects of Flt3 ligand, a cytokine that induces dendritic cell production, in vivo on the course of infection with Plasmodium berghei ANKA. Mice treated with Flt3 ligand showed preferential expansion of CD8(+) dendritic cells and granulocytes, as well as lower levels of parasitemia, and were protected from the development of lethal experimental cerebral malaria (ECM). Rag2 knockout mice treated with Flt3 ligand also showed inhibition of parasitemia, suggesting that this protection was due, at least in part, to the stimulation of innate immunity. However, it was unlikely that the inhibition of ECM was due simply to the reduction in the level of parasitemia. In the peripheral T cell compartment, CD8(+) T cell levels were markedly increased in Flt3 ligand-treated mice after infection. These CD8(+) T cells expressed CD11c and upregulated CXCR3, while the expression of CD137, CD25, and granzyme B was reduced. In the brain, the number of sequestered CD8(+) T cells was not significantly different for treated versus untreated mice, while the proportion of CD8(+) T cells that produce gamma interferon (IFN-γ) and granzyme B was significantly reduced in treated mice. In addition, sequestration of parasitized red blood cells (RBCs) in the brain was reduced, suggesting that altered CD8(+) T cell activation and reduced sequestration of parasitized RBCs culminated in inhibition of ECM development. These results suggest that the quantitative and qualitative changes in the dendritic cell compartment are important for the pathogenesis of ECM.     

The effect of an extract from Cochlospermum angolense ("Burututu") on Plasmodium berghei in the mouse malaria suppression test

Often existing cross-resistance to structure analogous antimalarials causes the need to find new active compounds against malaria parasites. For this purpose the traditional medicine of tropical countries has proved to be a treasury. A root extract of Cochlospermum angolense showed in vitro a remarkable activity against Plasmodium berghei in the DNA synthesis measurement with 3H-labelled hypoxanthine. This effect could be reproduced under in vivo conditions with the "4-day suppressive test" of rodent malaria.     

Immunosuppression in malaria: effect of hemozoin produced by Plasmodium berghei and Plasmodium falciparum

To a considerable degree, malaria-induced immunosuppression has been attributed to an inhibition of macrophage accessory cell function. In this study hemozoin, a plasmodium hemoglobin degradation product which readily accumulates in phagocytic cells and tissues during infection, was examined for its influence on immune responses. Hemozoin-laden liver and splenic macrophages from Plasmodium berghei-infected mice, displayed accessory cell dysfunction which was likely due to hemozoin loading by these phagocytic cells. This indicated by the observation that hemozoin obtained from livers and spleens of infected mice as well as from Plasmodium falciparum cultures greatly inhibited splenic plaque-forming cell responses to sheep red blood cells. The results of the present study strongly suggest that the inhibition of macrophage accessory cell activity is due, at least in part, to the uptake and accumulation of hemozoin in their cytoplasms.     

Plasmodium berghei malaria: effect of acute phase serum on immunity generated in rats by infection and by vaccination

Acute phase serum (APS) given at the time of challenge with Plasmodium berghei inhibited the generation to immunity to the infecting plasmodia. Administered with a single dose of vaccine, it inhibited induction of immunity by the vaccine. Three weekly doses, the last given two weeks before infection, induced immunity. Administration of vaccine simultaneously with infection neither aggravated nor ameliorated the infection. These results indicate that the effect of administration of APS on immunity generated by immunization or infection is dose- and time-dependent. The depression of immunity induced by this serum is thus temporary, the host finally overcoming the depression and responding to the plasmodial antigen in the serum. The interaction of vaccine and infection observed indicates that the introduction of vaccine is not detrimental to the individual incubating infection; rather, the vaccine is rendered useless, the reducing the aggregate benefit of the immunization to the group.     

Ultrastructural pathological changes in mice kidney caused by Plasmodium berghei infection

Malaria, a common health problem in certain parts of the world, has a considerable morbidity and mortality. This work reports under electron microscopy studies serious ultrastructural kidney damage such as extensive cytoplasmic vacuolation, vesiculation and autophagic vacuoles in proximal tubular cells. A thickened endothelial wall on peritubular capillary, interdigitation disorganization and significant decrease of their number in some areas were detected. Swollen rough endoplasmic reticulum, swollen mitochondria, and parasitized erythrocytes were observed. Many epithelial cells exhibited cytoplasmic areas of autophagia and a myelin-like form. A tubular cell presented severe cytoarchitecture alterations. Abundant lipid droplets were noticed. Almost total loss of interdigitations, rough endoplasmic reticulum vesiculation, peritubular capillaries with endothelial cells thickened cytoplasm, papillary processes projected to the lumen, and an inflammatory infiltrate of macrophages were also observed. These ultrastructural kidney changes could cause, on the basis of their clinical and pathologic expressions, a fat accumulation, an acute temporary reversible glomerulonephritis, a chronic progressive irreversible glomerulonephritis, and an acute renal failure (ARF).     

Platelet reactions in acute Plasmodium berghei infection in Swiss albino mice

Swiss albino mice were infected by the intraperitoneal route with P. berghei berghei malaria parasite, and platelets, white cell counts and some coagulation parameters were monitored in order to find out whether changes reported in man also occurred in the mice. Parasitaemia developed form the 2nd post-infection day and reached significant levels by the 4th-6th day. Reduced circulating platelets which reached severe thrombocytopenic levels were observed. parallel with the increasing degree of parasitaemia. Anaemia which progressed to severe degree was also observed as was a slight leucocytosis attributed to the presence of normal mouse erythrocytes in the peritoneal space. All untreated animals died by the 6th day of infection. Intramuscular chloroquine sulphate (20 micrograms/g body wt.) given for 7 days completely cured the malaria, and white cell and platelet counts were restored to preinfection levels in each animal about 2 weeks after treatment had ceased. Platelet hypersensitivity to exogenous ADP was observed within 48 hours of infection and persisted with the parasitaemia. Prothrombin time (PT) and activated partial thromboplastin time (APTT) were prolonged while clottable fibrinogen concentration was reduced.     

Regional immunosuppression induced by Plasmodium berghei yoelii infection in mice.

Plasmodium berghei yoelii infection in mice severely depressed the splenic antibody response to sheep erythrocytes but had lettle effect on antibody formation in lymph nodes.     

DNA synthesis in Plasmodium berghei during asexual and sexual development

DNA contents of individual stages of Plasmodium berghei were measured by direct microfluorometry after Feulgen-pararosaniline (SO2) staining. Sporozoites, intra-erythrocytic ringforms and trophozoites (until at least 15 h after invasion) are haploid and non-synthesizing DNA. DNA is synthesized just before and during schizogony, which takes 4-6 h. Genome duplication and segregation are alternating events throughout this process. Mature micro- and macrogametocytes have DNA contents between the haploid and diploid value; most, if not all of the DNA in excess of the haploid value is synthesized during the last 5-10 h of maturation. During gametogenesis microgametocytes within 8-10 min synthesize DNA steadily and at a very high rate to more than the octoploid value while the DNA content of macrogametocytes remains constant. Fertilization in vitro takes place within 1 h after gamete formation. Within 2 h and coinciding with the onset of meiosis the zygote then synthesizes DNA up to almost the tetraploid value, after which synthesis stops during ookinete development. All the above mentioned processes of DNA synthesis are reversibly inhibited by aphidicolin (C50 from 3-13 microM). From the rate of DNA synthesis during microgametogenesis we calculated a minimum of 1300 origins of replication in the haploid genome of P. berghei.     

Acute malaria prolongs susceptibility of mice to Plasmodium berghei sporozoite infection.

The fate of immune response against sporozoite stage in malaria infection was investigated. Two groups (A and B) of mice were inoculated twice with infective sporozoites of Plasmodium berghei. The mice in group A were maintained on chloroquine prophylaxis to prevent the sporozoite infection from causing malaria. Group B animals on the other hand were allowed to develop acute malaria from the infection which was subsequently cured with chloroquine. Upon examination for stage specific immune responses, it was found that the animals in group A produced high antibody titres against sporozoites and none against erythrocytic stages. The mice in group B produced little anti-sporozoite antibodies but had high antibody titres against blood forms. Challenge infection with P. berghei sporozoites showed that group A animals had become resistant against sporozoite-induced parasitaemia, whereas the mice in group B remained susceptible. The possible significance of suppression of protective immunity by malaria in host-parasite relationship is discussed.