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PubMed2002

Plasmodium vivax malaria in Southeast Iran in 1999-2001: establishing the response to chloroquine in vitro and in vivo.

Chloroquine-resistant Plasmodium vivax is emerging in Oceania, Asia and Latin America. The drug sensitivity of P. vivax to chloroquine both in vivo and in vitro in the southern part of Iran was assessed; chloroquine-resistant Plasmodium falciparum has already been documented in this area. The in vitro sensitivity of 39 P. vivax isolates was assessed: the mean IC50 and IC90 were 189 ng/ml and 698 ng/ml blood respectively; for in vivo testing, all 39 vivax malaria patients were treated with a standard regimen of chloroquine and followed-up at 28 days: the mean parasite clearance time was 67.2 +/- 22.5 hours. The in vitro development of young parasites to mature schizonts in standard test medium was compared with that obtained in McCoy's 5A medium: no significant difference was observed. Synchronization of the blood-stage parasites was performed according to Lambros' method: the method was not suitable because it was detrimental to the parasites. A number of in vitro tests were performed using both our own laboratory-predosed microplates and WHO microplates: there was no significant difference between the results.

Adolescent↗
PubMed2002

Trypsin and aminopeptidase activities in blood-fed females Anopheles dirus (Diptera: Culicidae) of differing susceptibility to Plasmodium yoelii nigeriensis.

Midgut proteolytic enzymes contribute to the success or failure of Plasmodium infection of the mosquito. The present study investigated trypsin and aminopeptidase activities in the midgut of two strains of Anopheles dirus selected for susceptibility and refractoriness to Plasmodium yoelii nigeriensis. At intervals of 6 hours following a bloodmeal, the midguts of fully engorged female mosquitos were dissected, homogenized, and assayed for enzyme activity. No differences trypsin activity (nmole/min) were observed between the two strains throughout the course of blood digestion. By contrast, the aminopeptidase activity measured at 0 to 18 hours post-feeding was the same for the two strains, but at 24, 30 and 36 hours significantly less activity was observed in the refractory females. The results suggest neither trypsin nor aminopeptidase plays a role in the limitation of parasite development.

Aminopeptidases↗
PubMed2003

[Biology of man-mosquito Plasmodium transmission].

The transmission of Plasmodium is a complex process that requires the encounter of three organisms: the parasite, the host and the mosquito vector. For a better understanding, the transmission of this parasite can be divided in four cyclical steps: 1) the development in man, including gametocytogenesis, 2) the transfer from man to mosquito, 3) the sporogonic development in the mosquito, 4) the transfer from mosquito to man. The present article proposes a review of these different aspects and focuses especially to recent biological knowledge on Plasmodium falciparum in the gametocytogenesis issues, infectivity of gametocytes, sporogonic development and natural factors limiting this development.

Animals↗
PubMed2003

Acute renal failure in Plasmodium vivax malaria.

OBJECTIVES: To analyze incidence, clinical feature and outcome of acute renal failure due to Plasmodium vivax malaria. MATERIAL & METHOD: This is retrospective analysis of smear positive Plasmodium vivax patients with acute renal failure between Jan 1995 to Dec 2000. RESULT: Out of 577 cases of ARF, 93 [falciparum 74 (79.61%); vivax 19 (20.4%)] were related to complicated malaria. 3.2% (19/577) patients, 16 males and three females with age range 17-72, mean 43.3 +/- 13.4 years were due to vivax malaria. Thirteen had only vivax and six had mixed falciparum and vivax infection. The presenting features were fever (100%), jaundice (36.8%), hypotension--eight (42%), encephalopathy--11 (57.9%), sepsis--five (26.3%) and DIC--four (21%). The probable contributory factors for ARF were heavy parasitemia--11 (57.9%), hypotension--six (31.5%), hyperbilirubinemia--seven (36.8%), hemolysis--eight (42%) and DIC--four (21%). Oliguria was present in 47.3%, 13 (68.4%) patients required dialysis. Mortality was noted in 15.7% (3/19) patients. CONCLUSIONS: P. vivax malaria can cause ARF, which occurs more commonly in P. falciparum malaria. Renal ischemia is the dominant pathogenic mechanism that results in acute tubular necrosis. The prognosis of ARF in P. vivax malaria is favorable.

Acute Kidney Injury↗
PubMed2003

Field application and evaluation of a rapid immunochromatographic test for detection of Plasmodium falciparum infection among the inhabitants of Lao PDR.

Field application and evaluation of a rapid immunochromatographic test (ICT) for detection of Plasmodium falciparum infection were performed in 13 villages in a southern province of Lao PDR in 1999. More than 2,000 inhabitants, accounting for 61.8% of the total estimated population, were examined. Malaria infection was confirmed in all villages surveyed by ICT and microscopic diagnosis. The positive rates of P. falciparum malaria by microscopy ranged from 9.7% to 59.2% (mean 27.2%), whereas by ICT they were from 11.6% to 64.5% (mean 29.8%). The positive rates by ICT were generally higher in 8 out of 13 villages. However, a significant difference between the positive rates by microscopy and ICT was not observed in all villages. Plasmodium falciparum infection was actually confirmed by microscopy in 84.1% of specimens that tested positive by ICT. The results by ICT were consistent with those of the microscopic diagnosis, the discrepancy of the results was less than 10% (141/2,066). The ICT was falsely-positive in 4.7% and falsely-negative in 2.1% of the test cases. These results showed the efficacy of ICT not only in the diagnosis of the respective cases, but also in the mass-examination in the field.

Animals↗
PubMed1992

[Effects of dexamethasone and cyclophosphamide on development of exo-erythrocytic form of Plasmodium cynomolgi bastianellii in rhesus monkey].

The rhesus monkeys (Macaca mulatta) challenged with Plasmodium cynomolgi bastianellii sporozoites were treated with im dexamethasone (Dex) 1 mg.kg-1.d-1 x 7 d and cyclophosphamide (Cyc) 25 mg.kg-1.d-1 x 3d, respectively. On d 7 after challenge, serial sections of liver biopsy stained with HE revealed that the distributive density and size of exo-erythrocytic (EE) form of the parasites showed no difference between medicated and control monkeys. The prepatent period of the primary attack and the relapse patterns after the treatment of Dex and Cyc were also similar to each other. The radically cured monkeys challenged with the Plasmodium erythrocytic form were reinfected with sporozoites, the relapses were much less than those in control monkeys, but the density and size of EE form in liver were similar to those in control monkeys. These results suggest that Dex and Cyc exert no effect on the development of EE form (including hypnozoite) in the monkeys.

Animals↗
PubMed1992

[Studies on the establishment of malarial animal model of short-term relapse. I. Asynchronous growth of exoerythrocytic schizonts of Plasmodium cynomolgi].

A monkey was infected with sporozoites of Plasmodium cynomolgi from Vietnam. Parasitemia was detected on the 8th day with a starting density of 17/100 white blood cells. 22 hours after that time, many EE schizonts appeared with an average density of 3.74 +/- 0.66 per mm3 hepatic tissue in liver biopsy specimens from the monkey. Most of the EE schizonts were immature and grew at an uneven rate, having an average diameter of 34.22 +/- 7.28 microns but some of them even remained 15.75 +/- 2.47 microns in diameter similar to the EE schizonts on the 6th day. The results showed that the EE schizonts of Plasmodium cynomologi were asynchronous in growth. The authors suggest that the release of merozoites from liver might be a successive process for many times, and not to be completed at a time.

Animals↗
PubMed1992

A method for screening drugs against the liver stages of malaria using Plasmodium gallinaceum and Aedes mosquitos.

1. The radical cure of human malaria caused by Plasmodium vivax requires two drugs, i.e., a blood schizontocide such as chloroquine to clear the circulating parasites, and primaquine aimed at the liver stages (hyponozoites) responsible for the late relapses of this parasite. Primaquine is unique as a radical curative drug but is highly toxic. The only useful model currently available for screening drugs to replace primaquine is Plasmodium cynomolgi-induced malaria in Rhesus monkeys. Because of the limited availability and cost of these animals, the development of non-primate models for such screening would be of considerable value. 2. We used a drug-screening assay for the liver stage malaria parasite based on the ability of such drugs to stop development of gametocytes in the mosquito vector. The inhibition of the sporogonic cycle of malaria in the mosquito by primaquine (15 mg/kg) was confirmed here and used for re-evaluation of the gametocyte method. 3. We observed that the level of parasitemia in the untreated control chicken used to infect mosquitos was a crucial factor affecting the subsequent development of sporogony. Thus, parasitemia was carefully controlled in the studies involving oocyst development. Parasitemias lower than 6% at the beginning of the experiment and increasing were found to be most appropriate for the production of the infectious gametocytes during a period of 8 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Aedes↗
PubMed1992

[Chemical synthesis and cloning of Plasmodium falciparum 45 peptide antigen gene].

We have synthesized a 162 bp gene of human Plasmodium falciparum hybrid peptide antigen by the solid-phase phosphoramidite method with ABI 381A DNA synthesizer. The gene encodes three fragments of the relative molecules 83 kDa, 55 kDa and 35 kDa merozoite-specific proteins and two CS repeats or four peptides. The gene with the designed two cohesive ends was divided into 8 fragments to be synthesized. All synthetic fragments were annealed and ligated with T4 DNA ligase to form double DNA chain. This synthetic gene was recombined with P-Blue script as vector and transformed into E. coli JM109. The positive recombinants were screened out by dot hybridization and enzyme analysis. The DNA sequence analysis showed that the synthesized human Plasmodium falciparum hybrid peptide antigen gene was identical with the designed one. (Figs. 1-4).

Amino Acid Sequence↗
PubMed1992

[DNA sequence of surface antigen gene gp195 of two Chinese isolates of Plasmodium falciparum from Hainan].

Amplification of DNA sequence of surface antigen gene, block II of gp195 from 2 Chinese isolates of Plasmodium falciparum FCC 7801/HN B3 and FCC M21/HN from Hainan, China, was established by using the polymerase chain reaction. A comparison of the 154 peptide sequences of the 2 Chinese isolates showed that they were identical, but there was a difference of 10 peptides among the established 154 peptides between the two Chinese isolates and MAD 20 (a Papua New Guinea isolate). The need to determine the fragments having protective effect against malarial infection, and to study the genetic basis of the antigen polymorphism of Chinese strains of Plasmodium falciparum is evident.

Amino Acid Sequence↗
PubMed2001

Rodent malaria in the natural host--irradiated sporozoites of Plasmodium berghei induce liver-stage specific immune responses in the natural host Grammomys surdaster and protect immunized Grammomys against P. berghei sporozoite challenge.

The choice of the host in studying host-parasite interactions is of crucial importance, and the use of a natural host is most appropriate in answering pertinent questions related to human malaria. The Grammomys surdaster is the natural host and reservoir of the rodent malaria parasite Plasmodium berghei. This natural host is difficult to protect by irradiated sporozoite immunization, a situation comparable to what has been observed in humans with P. falciparum. This is in contrast to the complete protection that can be induced in artificial hosts like inbred mice strains. The natural host is highly susceptible to P. berghei hepatic stage infections. Immunization with irradiated sporozoites in Grammomys generates blocked hepatic stage parasites and immunized Grammomys protected upon live sporozoite challenge generate antibody and T cell proliferative responses to these hepatic stages. Associated with proliferation, cytokines are secreted into culture supernatants constituted mainly of Interferon gamma, negligible amounts of TNF-alpha, and no IL-4. Natural host-parasite interactions of Grammomys surdaster-P. berghei can help define the effector mechanism(s) in the Plasmodium falciparum-human interaction.

Animals↗
PubMed1992

Trials to infect Anopheles stephensi with Plasmodium yoelii nigeriensis by the membrane feeding technique.

The aim of this study was to find optimal conditions for the membrane feeding technique to obtain maximum infection rates of mosquitoes with Plasmodium yoelii nigeriensis. The results show that the malaria parasite Plasmodium yoelii nigeriensis is most infective to Anopheles stephensi mosquitoes on day 3 of the infection in the mice, 1 day before the peak of parasitaemia. The mortality rate of the mosquitoes fed on mice on day 3 after infection was the highest as compared to mosquitoes fed on other days after infection. Gametocytes from mice 3 days after infection were fed to mosquitoes by three different membrane feeding methods. The results indicate that feeding during the first 10 min after blood collection gave the highest infection rates. Keeping the blood meal at a pH of 7.2 yields higher infection rates than keeping it at pH of 8.5. Stirring of the blood and supplying it with CO2 is not necessary when feeding of the mosquitoes is completed within the first 10 min after collection of the blood.

Animals↗
PubMedDate not supplied

Natural killer (NK) cell-mediated cytolysis of Plasmodium falciparum-infected human red blood cells in vitro.

The ability of human NK cells to inhibit the growth in vitro of the asexual blood stages of Plasmodium falciparum was tested. Purified NK cells from donors with no prior exposure to malaria significantly inhibited parasite growth after 48 hours of co-culture in the presence of human immune serum. This inhibition was completely abrogated by pre-treatment of the NK cells with an anti-CD95 (anti-Fas) monoclonal antibody and human Fas-Fc soluble protein. The level of growth inhibition was also substantially reduced by pre-treatment with an anti-CD56 antibody. These two antibodies caused reductions, to varying levels, of the amounts of NK cell-derived granzyme B (GrB) and pro-inflammatory cytokines, but only the anti-CD95 antibody affected the production of soluble Fas ligand (sFasL). Direct destruction of parasite-infected red cells by NK cells, in the absence of serum, was also observed in a standard 51Cr cytotoxicity test, during which N-carboxybenzoxy-L-lysine thiobenzil ester (BLT esterase) activity, which catalyzes serine protease granule release, was detected. The results obtained are indicative of a novel mechanism of NK cell-mediated cytotoxic activity against Plasmodium falciparum-infected red cells, which is mediated in part by both Fas and by GrB.

Animals↗
PubMed2003

[Plasmodium falciparum: epidemiology and man-mosquito transmission and infection in the vector].

The level of malaria transmission is usually estimated by some entomological parameters (entomological inoculation rate or reproductive rate and its seasonal variations). However, only one aspect of the malaria transmission is explored by this way, i.e. the transmission of Plasmodium from mosquito to man. The transmission from man to mosquito, the development of parasite in the mosquito midgut, and the role of transmission blocking immunity remain poorly documented. Recent studies on vaccination with gamete antigens showed that transmission blocking immunity, and the natural infectiousness of gametocytes after treatment underlined the need for taking into account a new aspect of malaria epidemiology concerning the transmission of Plasmodium from man to mosquito. In this paper, authors propose and discuss different new indicators and methods to improve our knowledge on malaria epidemiology.

Animals↗
PubMed2003

[The internal control role of ribosomal protein S7 in the defense of Anopheles dirus against Plasmodium infection].

OBJECTIVE: To investigate the role of ribosomal protein S7 (rpS7) in the defense of Anopheles dirus against infection. METHODS: rpS7 was amplified from Anopheles dirus hemocytes with degenerated primers designed according to the conservative region of S7, rpS7 was then cloned using T/A cloning kit and the inserted fragment was sequenced. The difference of the transcript abundance of rpS7 from Anopheles dirus hemocyte among non-blood-fed (N), normal-blood-fed (B) and Plasmodium yoelii infected groups (I) was also analyzed by RT-PCR and gel scanning system at d1, d2, d3, d4, d7 and d11 after blood feeding. RESULTS: There is no significant difference of rpS7 signal between the three groups. CONCLUSION: Anopheles dirus S7 can be used as an internal control to study the role of Anopheles dirus related immune factors in Plasmodium infection.

Amino Acid Sequence↗
PubMed2004

[Morphological characteristics of Plasmodium yoelii schizonts in ghost erythrocytes].

OBJECTIVE: To observe the morphological characteristics of Plasmodium yoelii schizogony in their ghost erythrocytes. METHODS: Saponify, hypotonic shock, and electron microscopy were used to observe the different fashions of erythrocytic parasites and their characteristic organellae in ghost erythrocytes. RESULTS: The malarial parasites and their fine structures were dramatically well preserved in the ghost erythrocytes, such as the ring-like early trophozoites, the brassiere-like early schizonts, the emerging buds on the surface of late schizonts, and the grape-cluster like late schizonts. The cytostome, food vacuole, and crystallized malarial pigments were found in the early trophozoites. The proliferations of nucleoplasma and nuclear membrane as well as and the clot-like nuclear division were followed by the budding during the schizogony. CONCLUSION: The saponify technique that makes the erythrocytic malaria parasites and their fine organellae to be dramatically revealed in their ghost erythrocytes, may be a useful method in the Plasmodium biological research and anti-malaria immunological researches.

Animals↗
PubMed2004

[Immunity of peritoneal monocytes against Plasmodium yoelii infected erythrocytes].

OBJECTIVE: To test the immunity of peritoneal monocytes against Plasmodium yoelii infected red blood cells (target cells). METHODS: Saponinized Plasmodium yoelii infected red blood cells (SPRBC, Ghost erythrocyte) were used to immunize mice i.p twice. Three weeks later, the infected red blood cells were injected i.p.; 90 min later, the total peritoneal cells were isolated and washed for scanning electromicroscopy to observe the effects of the peritoneal monocyte to the target cell. RESULTS: The peritoneal cells of the immunized mice were activated after 90 min of the challenge of target cells. The size of the cell was not even and the pili on the cell surface turned to be long and densed. Cell interconnections were found among the cells. In some peritoneal monocytes, their cell plasma were scattered (omlette-like) or with the shape as "cellular bomb". The scattered or the sheeted pili and spredding cell plasma could adhere to the target cells which were perforated densely and damaged. CONCLUSION: The protective adaptive immunity exists in the peritoneal monocytes of immunized mice.

Animals↗
PubMed2004

Genetic diversity in the merozoite surface protein 1 gene of Plasmodium falciparum in different malaria-endemic localities.

A number of stage-specific antigens have been characterized for vaccine development in Plasmodium falciparum malaria. The polymorphic merozoite surface protein 1 (MSP-1) of Plasmodium falciparum is a major asexual blood stage malaria vaccine candidate antigen. In the present study, we analyzed the impact of hyperendemic malaria transmission, mesoendemic malaria transmission, and multiple infection on allelic diversity. We have used a simple strategy of polymerase chain reaction amplification and slot-blot hybridization to analyze variable regions of block-2, block-4 and blocks 6-10 of the MSP-1 gene. The allelic types of isolates collected from regions of hyperendemic malaria transmission (RHEMT) and mesoendemic malaria transmission (RMEMT) were compared. In RHEMT, 20 of 24 possible gene types were found among 163 isolates and more than one allelic type was found in 82 (50.3%) of the isolates. Thirteen of 24 possible gene types were found among 125 isolates in RMEMT and 27 (21.6%) of them contained more than one allele type. Our results suggest for the first time that the allelic distribution or allelic diversity and chances of finding multi-strain parasites in isolates in an area vary with the rate of transmission. Analyses of isolates containing more than one strain of parasite suggest that allelic types are randomly distributed, no specific type of alleles predominately show multi-strain infection, and neither strain of the parasite affect the process of infection and development of another.

Alleles↗