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PubMed2004

A bedside dipstick method to detect Plasmodium falciparum.

We conducted this study to determine efficacy of Parasight-F (an HRP-II antigen dipstick method to detect P. Falciparum) in children. A total of 30 children were enrolled in the age group of 2 months to 12 years whose peripheral smear showed asexual forms of Plasmodium falciparum. All patients were tested for presence of HRP-II antigen of Plasmodium falciparum in their blood by the Parasight-F dipstick test by either an EDTA sample or a finger prick blood sample. The sensitivity of Parasight-F was 83.3 % However, the sensitivity of Parasight-F to detect Plasmodium Falciparum in case of mixed Plasmodium (Vivax + Falciparum) infection was only 25 %. Also, all patients less than 6 months of age had a negative Parasight-F test. Parasitic index, prior treatment with antimalarials or severity of Falciparum malaria have no effect on the sensitivity of Parasight-F test. We conclude that Parasight-F is an effective tool for diagnosis of Plasmoduim falciparum malaria in children.

Animals↗
PubMed2004

Comparative study of the in vitro sensitivity of Plasmodium falciparum to artemisinin in two border areas of Thailand.

Artesunate was introduced in Thailand in 1995 for the treatment of falciparum malaria in areas of multidrug resistance, where it is used in combination with mefloquine. The studies were conducted between May and August 1999, 2000 and 2001 in the provinces Mae Hong Son and Tak (Mae Sot District) in northwestern Thailand, both on the border to Myanmar. The province of Mae Hong Son is still largely unaffected by multidrug resistance and infections with Plasmodium falciparum are treated with mefloquine alone. In the district of Mae Sot, 350 km southwards, more than 60% of the Plasmodium falciparum isolates were found to be resistant to mefloquine. Between 1999 and 2001, a total of 227 fresh isolates of Plasmodium falciparum were successfully tested for their sensitivity to artemisinin using the WHO standard in vitro microtest. The weighted mean EC5o and EC90 values for 1999-2001 were 9.20 nM and 34.37 nM in Mae Hong Son and 11.18nM and 71.63nM in Mae Sot, respectively. The comparison of the sensitivity to artemisinin between Mae Hong Son and Mae Sot showed no significant difference in 1999, but significant differences in 2000 (p<0.05) and in 2001 (p<0.01). This phenomenon could be a consequence of different drug pressure. Furthermore, the lower sensitivity of Plasmodium falciparum to mefloquine in Mae Sot may play a minor (but amplifying) role, as the activities of artemisinin and mefloquine show a significant correlation.

Animals↗
PubMed2005

Plasmodium malariae malaria--a case report.

The tropical zone is the endemic home for all malarial parasites. Plasmodium vivax and Plasmodium falciparum are the species that are prevalent commonly in India. Plasmodium malariae is a parasite of both the tropical and subtropical zones, especially West and East Africa, Guiana and parts of India, but its presence in various zones tends to be patchy. In Karnataka state, its prevalence is rare. A case of Plasmodium malariae malaria from St John's Medical College, Bangalore in the background of the rarity of occurrence in this part of the country is presented.

Adult↗
PubMed1991

[Preliminary studies on the diagnosis of Plasmodium falciparum malaria by monoclonal antibody sandwich dot-immunogold silver staining assay].

In this report, the blood samples from 30 falciparum malaria patients with parasitemia 0.015-0.58% and the blood samples from 30 healthy persons were examined by monoclonal antibody (McAb) sandwich dot-immunogold silver staining assay (Dot-IGSSA). When the McAb 11G5, 13A2 and 13A1 were used for sandwich Dot-IGSSA with McAb 14D9 labeled with colloidal gold respectively, the 0.0001% of parasitemia could be detected and the McAb 11G5, 13A1 and 14D9 labeled with colloidal gold could also be used to detect the antigens of asexual blood stages of Yunnan and Anhui isolates of Plasmodium falciparum cultured in vitro. These McAbs did not cross-react with the antigens of Plasmodium knowlesi and Plasmodium berghei, however, the McAbs 13A1 and 14D9 weakly cross-reacted with the antigens of Plasmodium cynomolgi and the antigens in the infected blood samples from patients with vivax malaria.

Animals↗
PubMed1991

[Molecular recognition between glycophorin A and Plasmodium falciparum merozoites].

By using purified human erythrocyte membrane glycophorin A (GPA) and glycopeptide of GPA, antibodies against GPA and against GPA-glycopeptide, and SPA-colloidal gold, Plasmodium falciparum FCC-1/HN merozoites were immunolabeled. The labeled samples were observed under transmission electron microscope (TEM). The TEM pictures showed that colloidal gold pellets were distributed over all of the merozoite surface. This is the first report on the direct experimental evidence of molecular recognition and combination between GPA (or glycopeptide of GPA) and Plasmodium falciparum merozoites. The results strongly support the hypothesis that GPA is involved as a recognized receptor on erythrocytes for Plasmodium falciparum and the glycopeptide domain of GPA is the receptor site for Plasmodium falciparum.

Animals↗
PubMed1990

[Study on the exoerythrocytic forms of Plasmodium yoelii yoelii in rats and mice].

SD rats and three strains of mice were infected with Plasmodium yoelii yoelii By265 strain by intravenous inoculation of sporozoites via tail vein. Liver tissues were taken 42 hours after infection and serial sections were made and stained by Colophonium-Giemsa method for microscopic examination. The ratio of the average value of major diameter/minor diameter of exoerythrocytic(EE)schizonts of Plasmodium yoelii yoelii in rats and mice of ICR/JCL, C57BL, KM strains was 35.81 +/- 4.56 microns/29.72 +/- 4.08 microns, 28.08 +/- 4.66 microns/23.66 +/- 4.44 microns, 28.14 +/- 4.16 microns/23.63 +/- 3.77 microns, 23.80 +/- 2.42 microns/21 +/- 0 microns, respectively. The results showed that the development of EE schizonts of Plasmodium yoelii yoelii was not synchronous. The EE schizonts in the rat liver were surrounded by Kupffer cells, monocytes and monocyte-derived macrophages. Since the parasitemia disappeared rapidly in rats, and EE schizonts were not well developed in KM strain, it may be considered that ICR/JCL and C57BL strains are more suitable as vertebrate host in Plasmodium yoelii yoelii-Anopheles stephensi system model (Figs. 1-9).

Animals↗
PubMed1979

[Production of interferon after infection by various doses of "Plasmodium berghei" in mice (author's transl)].

Groups of mice were inoculated with either low or high intraperitoneal doses of Plasmodium berghei infected erythrocytes (PIE). The course of infection was observed daily by counting new PIE which appeared in the red blood cells (RBC) of infected mice. At the same time, circulating interferon (IF) was tested. When low doses of infecting PIE were used (400 per mouse), circulating IF was first detected on the 5th day after inoculation. It increased to a maximal rate, when 5% of RBC were affected. It disappeared on the 8th day despite of a continuous rise of PIE. With high doses of PIE (60,000 per mouse), IF was detected on the 3rd day, when only 0.5% of RBC were parasitized. The maximal rate was observed on the 5th day when 20% of the RBC were affected. It disappeared on the 7th day, though the PIE rate would continue to rise. Treatment of mice by chloroquine (0.01 per g), at the time of first PIE appearance after Plasmodium infection, rapidly reduced the amount of PIE. In this case, no IF production was observed. Splenectomy resulted in an increased resistance of mice to the lethal effect of Plasmodium infection. IF production in such splenectomized mice was less important than in control. It was concluded that P. berghei was a good inducer of circulating IF at the beginning of the active disease, soon after infection. The fact was proven by the striking lowering effect of chloroquine and splenectomy that both reduced Plasmodium development and IF production.

Animals↗
PubMedDate not supplied

[Morphology and infectivity of gametocytes of Plasmodium inui].

The authors report biomorphological changes of Plasmodium inui gametocytes during the natural infection of spleenless Macaca fascicularis. The infection was controlled up to the 42th day by smears produced by pricks into their ears (P.O.) and on blood taken at the same time by A. stephensi (P.M.). The first oocystes appeared on the 8th day after the infection in mosquitoes fed on the monkey parasitised in the eight day after splenectomy, as gametocytaemia was not detectable yet in the P.O. smears. The infectivity of gametocytes is highest on the 13rd day for a 152/10(4) parasitaemia. The first sporozoites appeared on the 18th day at 25 degrees C after the infecting meal. The sporozoites were infecting for a second monkey. Four morphological types (O, I, II and III) gametocytes were identified. They corresponded to the same types previously described in rodent Plasmodium. The maximum of infectivity coincided with a sudden increase in mosquitoe macrogametocytaemia; on the other hand the infectivity was very weak during the following peek of macrogametocytaemia which corresponded however to the maximum of parasitaemia (1 318/10(4) 18 days after splenectomy). When infectivity was important, there was a greater number of type O and I gametocytes in P.M. than in P.O. Eventually, the behaviour of P. inui gametocytes is, for the mainly, almost the same as that of rodent Plasmodium. However, it is to be noted that the identification of the 4 morphological types in P. inui is easier in macrogametocytes than in microgametocytes. The reverse had been observed in rodent Plasmodium.

Animals↗
PubMed1995

[Preliminary study of a recombinant polyvalent vaccine of Plasmodium falciparum and its immunological activity].

A hybrid gene named HGFC coding three protective antigenic epitopes of Plasmodium falciparum and two exogenous T cell activating epitopes was designed and synthesized. A multicopy hybrid gene named HGF-CAC was also constructed. The two genes were cloned into expression vector pWR450-1 and the hybrid fusion proteins containing forgine antigens and beta-galactosidase were expressed in E. Coli. The molecular weights of the fusion proteins were 65KDa and 77KDa respectively. The expression rate was about 35% of total bacterial proteins. The fusion protein could react specifically with mouse and rabbit antibodies against antigens of Plasmodium falciparum. The rabbit immune serum against the purified fusion protein could specifically recognize the antigens of Plasmodium falciparum and effectively inhibit the in vitro development of the parasites. The inhibitory capacity of the immune sera to parasite invasion was enhanced as the amount of the sera increased and the incubation time of the sera with the parasites was prolonged. After 72h incubation at 20% concentration with the parasites, the serum suppressed the multiplication of parasite to a level of 82% and caused degeneration and death of the parasites. The results indicated that the recombinant hybrid antigen of Plasmodium falciparum has immunological activity and protectivity. It is probably a candidate malaria vaccine.

Amino Acid Sequence↗
PubMed1996

Molecular differentiation of two new world saurian Plasmodium species in different host species using the polymerase chain reaction.

Several isolates of Plasmodium floridense obtained from naturally infected Anolis carolinensis and Anolis sagrei, and 2 isolates of Plasmodium chiricahuae obtained from Sceloporus jarrovi were characterized at the ribosomal DNA (rDNA) locus using the polymerase chain reaction and agarose gel electrophoresis. Enzymatic amplification of the rDNA locus from both Plasmodium species resulted in the generation of a 590-base pair (bp) DNA fragment. The results obtained with all isolates of P. floridense appeared as a doublet, with the second fragment being approximately 630 bp in size. Isolates of P. floridense obtained from A. carolinensis from ecologically different northern and southeastern Florida, and from A. sagrei a the same southeastern Florida site, were demonstrated to be molecularly similar. Plasmodium floridense and P. chiricahuae were molecularly distinct at the 18s rDNA locus, thus confirming their morphological and morphometrical distinction as taxonomic species. Anolis sagrei is a third natural host species for P. floridense in Florida.

Animals↗
PubMed1997

Mixed-species Plasmodium infections of humans.

We analyzed point-prevalence data from 35 recent studies of human populations in which Plasmodium falciparum and one other Plasmodium species were the reported causes of malaria infections. For the P. falciparum-Plasmodium vivax pair, higher overall prevalence in a human population is associated with fewer mixed-species infections than expected on the basis of the product of individual species prevalences. This is not true for P. falciparum-Plasmodium malariae.

Animals↗
PubMed1999

Plasmodium: immunization with carboxyl-terminal regions of MSP-1 protects against homologous but not heterologous blood-stage parasite challenge.

A leading candidate for a vaccine targeted at the erythrocytic stages of plasmodial parasite development is the merozoite surface protein-1 (MSP-1). We have previously shown that the carboxyl-terminal region of MSP-1 derived from Plasmodium yoelii yoelii 17XL, expressed as a fusion protein with glutathione S-transferase (GST-PYC2), can immunize mice against an otherwise lethal homologous challenge infection. This protection has been shown to be predominantly mediated by antibodies. We report here on the efficacy of immunization with MSP-1 carboxyl regions when the challenge is a heterologous rodent parasite species. The course of parasitemia was not altered in mice immunized with GST-PYC2 and challenged with 10(4) heterologous Plasmodium chabaudi adami parasites, as both control and immunized mice developed infections that peaked at day 7 and then rapidly declined. Similarly, mice immunized with GST-PYC2 and challenged with 10(5) Plasmodium berghei ANKA parasites displayed virulence similar to that seen in infection control mice. The homologous region of the P. chabaudi adami MSP-1 gene was similarly expressed as a fusion protein with GST. Mice immunized with GST-PCC2 and challenged with 10(4) parasites showed significant protection against homologous P. chabaudi adami infection but no protection whatsoever against heterologous P. yoelii yoelii 17XL infection. These in vivo results correlate with the observation that sera generated by immunization with the carboxyl region of MSP-1 recognizes this protein from homologous, but not heterologous, radiolabeled parasite protein preparations.

Amino Acid Sequence↗
PubMedDate not supplied

Proteome analysis of rhoptry-enriched fractions isolated from Plasmodium merozoites.

The rhoptries of Plasmodium species participate in merozoite invasion and modification of the host erythrocyte. However, only a few rhoptry proteins have been identified using conventional gene identification protocols. To investigate the protein organization of this organelle and to identify new rhoptry proteins, merozoite rhoptries from three different Plasmodium rodent species were enriched by sucrose density gradient fractionation, and subjected to proteome analysis using multidimensional protein identification technology (MudPIT); 148 proteins were identified. To distinguish abundant cellular contaminants from bona fide organellar proteins, a differential analysis comparing the proteins in the rhoptry-enriched fractions to proteins identified from whole cell lysates of P. berghei mixed asexual blood stages was undertaken. In addition, the proteins detected were analyzed for the presence of transmembrane domains, secretory signal peptide, cell adhesion motifs, and/or rhoptry-specific tyrosine-sorting motifs. Combining the differential analysis and bioinformatic approaches, a set of 36 proteins was defined as being potentially located to the Plasmodium rhoptries. Among these potential rhoptry proteins were homologues of known rhoptry proteins, proteases, and enzymes involved in lipid metabolism. Molecular characterization and understanding of the supramolecular organization of these novel potential rhoptry proteins may assist in the identification of new intervention targets for the asexual blood stages of malaria.

Animals↗
PubMed1991

Circumsporozoite protein genes of malaria parasites (Plasmodium spp.): evidence for positive selection on immunogenic regions.

The circumsporozoite (CS) protein is a cell surface protein of the sporozoite, the stage of the life cycle of malaria parasites (Plasmodium spp.) that infects the vertebrate host. Analysis of DNA sequences supports the hypothesis that in Plasmodium falciparum, positive Darwinian selection favors diversity in the T-cell epitopes (peptides presented to T cells by host MHC molecules) of the CS protein. In gene regions encoding T cell epitopes of P. falciparum, the rate of nonsynonymous nucleotide substitution is significantly higher than that of synonymous substitution, whereas this is not true of other gene regions. Furthermore nonsynonymous nucleotide substitutions in these regions cause a change of amino acid residue charge significantly more frequently than expected by chance. By contrast, in Plasmodium cynomolgi, the same regions show no evidence of positive selection, and residue charge is conserved. The CS protein has a central repeat region, which is the target of host antibodies. In P. falciparum, the amino acid sequence of the repeat region is conserved within and between alleles. In P. cynomolgi, on the other hand, there is evidence that positive selection has favored evolution of two different repeat types within a given allele.

Amino Acid Sequence↗
PubMed1984

Evolutionary relatedness of Plasmodium species as determined by the structure of DNA.

Malaria parasites can be grouped evolutionarily by analysis of DNA composition and genome arrangement. Those that vary widely with regard to host range, morphology, and biological characteristics fit into only a small number of distinctive groups. The DNA of the human parasite Plasmodium falciparum fits into a group that includes rodent and avian malarias and is unlike the DNA of other primate malaria parasites. The DNA of Plasmodium vivax, which is also a human parasite, fits into a distinctly different group that includes Plasmodium cynomolgi, a parasite of monkeys. The evolutionary lines suggested here appear to be consistent with similarities seen among malaria parasites with regard to gene sequence.

Animals↗
PubMed2006

An analysis of mobile genetic elements in three Plasmodium species and their potential impact on the nucleotide composition of the P. falciparum genome.

BACKGROUND: The completed genome sequences of the malaria parasites P. falciparum, P. y. yoelii and P. vivax have revealed some unusual features. P. falciparum contains the most AT rich genome sequenced so far--over 90% in some regions. In comparison, P. y. yoelii is approximately 77% and P. vivax is approximately 55% AT rich. The evolutionary reasons for these findings are unknown. Mobile genetic elements have a considerable impact on genome evolution but a thorough investigation of these elements in Plasmodium has not been undertaken. We therefore performed a comprehensive genome analysis of these elements and their derivatives in the three Plasmodium species. RESULTS: Whole genome analysis was performed using bioinformatic methods. Forty potential protein encoding sequences with features of transposable elements were identified in P. vivax, eight in P. y. yoelii and only six in P. falciparum. Further investigation of the six open reading frames in P. falciparum revealed that only one is potentially an active mobile genetic element. Most of the open reading frames identified in all three species are hypothetical proteins. Some represent annotated host proteins such as the putative telomerase reverse transcriptase genes in P. y. yoelii and P. falciparum. One of the P. vivax open reading frames identified in this study demonstrates similarity to telomerase reverse transcriptase and we conclude it to be the orthologue of this gene. CONCLUSION: There is a divergence in the frequencies of mobile genetic elements in the three Plasmodium species investigated. Despite the limitations of whole genome analytical methods, it is tempting to speculate that mobile genetic elements might have been a driving force behind the compositional bias of the P. falciparum genome.

Amino Acid Sequence↗
PubMed2003

The histone H4 gene of Plasmodium falciparum is developmentally transcribed in asexual parasites.

Histones are abundant nuclear core proteins that are present in all eukararyotes and are responsible for linking chromosomes and packaging them into tight chromatin aggregates. The histone H2A, H2B, and H3 genes and a partial sequence of the histone H4 gene from Plasmodium falciparum have been previously identified and share a high level of nucleotide sequence identity. In this study, we compare the histone H4 sequence of the human malaria P. falciparum with the sequences of two mouse malarias, Plasmodium berghei and Plasmodium yoelii, revealing at least 91% identity at the nucleotide level and 100% conservation at the amino acid level. Furthermore, we show the P. falciparum histone H4 is developmentally transcribed in late stage asexual parasites, completing the transcription profile for the genes comprising the histone octamer of P. falciparum and adding support to suggestions that a novel histone mRNA control mechanism exists in this parasite.

Animals↗
PubMedDate not supplied

Prevalence and level of antibodies to the circumsporozoite proteins of human malaria parasites, including a variant of Plasmodium vivax, in the population of two epidemiologically distinct areas in the state of Acre, Brazil.

A seroepidemiological study of the prevalence of antibodies against the repeating epitopes of circumsporozoite (CS) proteins of human malaria parasites was conducted in 2 different areas in the state of Acre, Brazil in 1987 and 1990. In 1987 antibodies against the CS protein of the VK 247 variant Plasmodium vivax as well as antibodies against the CS proteins of P. falciparum and the classic P. vivax were found at relatively high rates in the 2 areas, but significant microepidemiological differences were observed. In 1990, when large scale migration in Amazonia had ceased and control measures were applied in the study areas, the malaria endemicity decreased, as determined by the declining prevalence of anti-sporozoite antibodies against all Plasmodium species, and the small number of individuals with positive blood smears. Antibodies against sporozoites of the variant P. vivax did not cross-react with the CS proteins of the classic P. vivax, nor with antibodies against sporozoites of P. falciparum and P. malariae. Sera containing antibodies against the CS protein of P. malariae were found at a very low frequency, and only in 1987. The anti-CS protein antibody response to all Plasmodium species was age-related.

Adolescent↗