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At least 145 records · Page 8Linked to original sources
PubMed1986

Immunoregulatory alterations in Plasmodium falciparum and Plasmodium vivax infections.

Studies on the immune function of patients with acute Plasmodium vivax or P. falciparum infections were performed. All subjects were residing in recent malaria endemic areas of Venezuela. Lymphopenia, reduction of peripheral blood T-lymphocytes positive for monoclonal antibody OKT4 (T helper) a decrease of in vitro mitogenic proliferative response and natural killer cell activity were observed. Serum lymphocytotoxic antibodies reactive at 37 degrees C were detected in both groups of patients as well as serum autoantibodies. The possible role of lymphocytotoxic autoantibodies in the etiology of the T-lymphocyte depletion and acquired immunological perturbations in human malaria is discussed.

Antilymphocyte Serum↗
PubMed2002

Plasmodium falciparum: glycosylation status of Plasmodium falciparum circumsporozoite protein expressed in the baculovirus system.

We expressed the main surface antigen of Plasmodium falciparum sporozoites, the circumsporozoite protein (CSP), in High Five (Trichoplusia ni) insect cells using the baculovirus system. Significant amounts of the recombinant protein could be obtained, as judged by SDS-PAGE, Western blot, and immunofluorescence analysis. The cellular localization for recombinant CSP was determined by immunofluorescence. The high fluorescence signal of the permeabilized cells, relative to that of fixed nonpermeabilized cells, revealed a clear intracellular localization of this surface antigen. Analysis of possible posttranslational modifications of CSP showed that this recombinant protein is only N-glycosylated in the baculovirus system. Although DNA-sequence analysis revealed a GPI-cleavage/attachment site, no GPI anchor could be demonstrated. These analyses show that the glycosylation status of this recombinant protein may not reflect its native form in P. falciparum. The impact of these findings on vaccine development will be discussed.

Animals↗
PubMed1983

Deficiency of Con A-induced suppressor cell activity in peripheral blood mononuclear cells from Thai adults naturally infected with Plasmodium falciparum and Plasmodium vivax.

Con A-pretreated mononuclear (MNC) cells from Thai adults with naturally acquired P. falciparum or P. vivax malaria were significantly less effective in suppressing the responsiveness of autologous or normal allogeneic responder cells to mitogenic lectins or allogenic stimulator cells than pretreated cells from healthy donors. Serial studies of three patients demonstrated that reduced suppressor cell activity was present early in malaria infection but returned to normal soon after treatment. These studies demonstrate that the loss of T cells previously observed in patients with malaria, in part may functionally represent a loss of suppressor T cells.

Adult↗
PubMed1975

Chemosuppressive field trials in Thailand. II. The suppression of Plasmodium falciparum and Plasmodium vivax parasitemias by a diformyldapsone-pyrimethamine combination.

In an area of Thailand where chloroquine-resistant falciparum malaria is known to exist, a chemosuppressive field trial was undertaken to test the efficacy of the preparation diformyldapsone (DFD) combined with pyrimethamine (Py) in suppressing falciparum and vivax parasitemias. Six hundred and fifty-nine Thai villagers were randomly assigned to one of five treatment groups: DFD-Py; dapsone (DDS)-Py; DFD alone; Py alone; and placebo. Five hundred and ninety-three study subjects completed the 26-week trial. The combination DFD-Py given weekly was shown to be an effective chemosuppressive against both falciparum and vivax parasitmias, causing a more than fourfold reduction in falciparum and an approximately threefold reduction in vivax parasitemias; however, this combination was not more efficacious than DDS-Py for the chemosuppression of falciparum malaria. DFD alone was only moderately effective, while there was no difference in chemosuppression between Py alone and placebo.

Adolescent↗
PubMed2002

Atovaquone/proguanil therapy for Plasmodium falciparum and Plasmodium vivax malaria in Indonesians who lack clinical immunity.

Thirty-eight of 295 subjects participating in a randomized, double-blind, placebo-controlled trial of the efficacy of daily administration of atovaquone/proguanil for malaria prevention developed malaria at some time during the 20-week prophylaxis period. These subjects (3 atovaquone/proguanil recipients and 35 placebo recipients) were treated with 4 tablets of atovaquone/proguanil per day for 3 days. Atovaquone/proguanil provided safe, well-tolerated, and effective therapy for uncomplicated malaria in nonimmune Indonesians.

Adolescent↗
PubMed1980

Anti-lymphocytotoxic antibodies in sera of Thai adults infected with Plasmodium falciparum or Plasmodium vivax.

Because of the potential for the elimination of lymphocytes through anti-lymphocytotoxic antibodies we examined individual sera of patients infected with falciparum or vivax malaria for the presence of antibodies against normal peripheral blood mononuclear cells. In assays done at 15 degrees C, 95% of the P. falciparum patients and 98% of the P. vivax patients showed evidence for antibody activity. Activity at 37 degrees C was significantly less than that at 15 degrees C. These studies suggest that infection with malaria induces anti-lymphocytotoxic antibodies which are predominantly cold-reactive. It is possible that this phenomenon plays a role in modulating the immune response of patients toward malaria.

Adult↗
PubMed1989

Comparison of the primary structure of the 25 kDa ookinete surface antigens of Plasmodium falciparum and Plasmodium gallinaceum reveal six conserved regions.

The gene encoding the 25 kDa ookinete surface antigen (Pgs25) of Plasmodium gallinaceum has been cloned using an oligonucleotide probe directed against one of the EGF-like domains of the P. falciparum 25 kDa ookinete surface antigen (Pfs25). The Pgs25 gene codes for a polypeptide of 215 amino acids, two amino residues less than Pfs25. The deduced amino acid sequence contains a putative signal sequence at the amino-terminus, four tandemly repeated EGF-like domains, and a hydrophobic region at the carboxyl-terminus. By comparing Pgs25 with Pfs25, six conserved regions, consisting of six or more amino acid residues, have been identified. Most of the conserved regions are outside EGF-like core consensus sequences. The most striking conservation is the spacing of the cysteines.

Amino Acid Sequence↗
PubMed2003

A multiplex polymerase chain reaction for a differential diagnosis of Plasmodium falciparum and Plasmodium vivax.

A multiplex PCR was designed for the differential diagnosis of the two parasite species by targeting the 18S rRNA gene with a set of primer combinations, amplifying DNA fragments of 1451-bp and 833-bp for P. falciparum and P. vivax, respectively. The sensitivity of this PCR test was high, as minimal as 0.1 parasite per one microliter of blood sample and a minimum of four copies of the target gene could be detected. For the diagnosis of mixed infection of two Plasmodium spp., there were no apparent competition or cross-reaction between the majority and minority Plasmodium species. The multiplex PCR was evaluated on 210 clinical samples and 60 normal controls. The PCR test yielded highly concordant results with microscopic examination, with the only one exception of a mixed (P. falciparum plus P. vivax) infection case, which was diagnosed as a single infection of P. falciparum by microscopy. We propose that the multiplex PCR is a sensitive, specific, and rapid tool that can serve as a useful differential diagnostic tool for detecting P. falciparum and P. vivax.

Animals↗
PubMed2005

[An imported case of mixed malaria caused by Plasmodium falciparum and Plasmodium ovale.].

Malaria caused by Plasmodium species is an important parasitic infection in Turkey as in the rest of the world. Malaria cases originating in our country are caused by P. vivax; those caused by other Plasmodium spp. are imported cases. In this article, after work-related travel to Cameroon, a patient who acquired specific clinical signs and symptoms of malaria has been evaluated. The major clinical findings of the patient were fever, chills and shaking. After examination of thin and thick blood smears prepared from the peripheral blood of the patient, a 20% rate of Plasmodium parasitemia was obtained and the case was considered to be a mixed P. falciparum and P. ovale infection. In addition, P. falciparum infection was confirmed using the Optimal Malaria Rapid Test and the presence of another Plasmodium species besides P. falciparum was confirmed. Primaquine was added to quinine and doxycycline therapy for P. ovale hypnozoites. No Plasmodium was found in control blood smears after clinical improvement. In this case, it has been emphasized that in differential diagnosis of fever seen after travel to malaria endemic areas, malaria must be considered and prophylaxis must be carried out before travel.

English Abstract↗
PubMed1989

Analysis of the sporogonic development of Plasmodium falciparum and Plasmodium berghei in anopheline mosquitoes.

Basic knowledge of the sporogonic development of malarial parasites is crucial when evaluating the sporontocidal activity of antimalarial drugs or when determining why certain vectors are refractory to a particular parasite while others are competent vectors. We have developed a model which we have used to i) assess the sporogonic development of Plasmodium berghei ANKA in Anopheles stephensi and A. freeborni mosquitoes and ii) determine the effect of chloroquine on the sporogony of P. falciparum NF-54 in A. stephensi. Criteria used to assay sporogonic development include: i) number of oocysts present, ii) percentage of mosquitoes with oocysts, iii) time of release of sporozoites from the oocysts into the hemolymph, iv) time and degree of sporozoite invasion of salivary glands, and v) transmission (P. berghei) into vertebrate hosts. Parasite development in the mosquito is evaluated every other day, commencing on ca. day 7 post-feed (PF) and continuing until ca. day 22 PF. These detailed observations allow us to delineate the chronology of sporogonic development.

Animals↗
PubMed1999

RNA helicase-related genes of Plasmodium falciparum and Plasmodium cynomolgi.

RNA helicases play many essential roles including cell development and growth. Using degenerate oligonucleotide primers designed to amplify DNA fragments flanked by the highly conserved helicase motifs VLDEAD and YIHRIG and genomic DNAs from the malarial parasites as a template, we have cloned two putative RNA helicase genes (546 and 540 bp) from P. falciparum and one gene (546 bp) from P. cynomologi. Southern blot analysis revealed that these could be multiple and single-copy genes in P. falciparum and P. cynomolgi, respectively. Several members of the RNA helicase gene family share sequence identity with malarial parasite's helicases ranging from 30 to 76%, suggesting that they are functionally related. The discovery of such a multitude of putative RNA helicase genes in malarial parasites suggested that RNA helicase activities may be involved in many essential biological processes. Further characterization of these helicases may also help in designing parasite-specific inhibitors/drugs which specifically inhibit the parasite's growth without affecting the host.

Amino Acid Sequence↗
PubMed1986

Synthetic peptides from the circumsporozoite proteins of Plasmodium falciparum and Plasmodium knowlesi recognize the human hepatoma cell line HepG2-A16 in vitro.

Several lines of evidence have emphasized the importance of the malaria circumsporozoite (CS) protein as a factor in sporozoite invasion of the hepatocyte; however, the specific mechanism of cell recognition and invasion has not been explained. In this study we present evidence that a highly conserved region of the CS protein immediately adjacent to the repeat region, the N1 region, specifically recognizes receptors on the human hepatoma cell line HepG2-A16 under conditions where invasion by sporozoites can occur. Peptides consisting of sequences from the repeat region or of the more extensive N2 region showed no such specific association. Antibody against the N1 peptide could inhibit sporozoite invasion in vitro. Covalent coupling of radiolabeled N1 peptide to HepG2-A16 cells identified two hepatic cell proteins to be closely associated with the peptide. We suggest that these proteins could act as receptors or mediators, via the N1 region of the CS protein, for the P. falciparum sporozoite in the process of invasion of the hepatocyte.

Amino Acid Sequence↗
PubMed2004

Evaluation of a rapid whole blood immunochromatographic assay for the diagnosis of Plasmodium falciparum and Plasmodium vivax malaria.

OBJECTIVE: Microscopic examination of blood smears is the 'gold standard' for malaria diagnosis, but is labour intensive and requires skilled operators. Plasmodium vivax malaria accounts for up to 70% of infections in Sri Lanka. The objective of this study was to determine the effectiveness of an immunochromatographic test which can detect both the species of Plasmodium, P. vivax and P. falciparum, present in Sri Lanka. DESIGN: Prospective study from May 2001 to March 2002. SETTING AND METHODS: All persons above 5 years of age who presented to the Malaria Research Station, Kataragama or the Anti-malaria Clinic, Kurunegala, with a history of fever were recruited to the study. Thick and thin blood smears were examined for malarial parasites. The rapid diagnostic test (RDT), ICT Malaria P.f/P.v (AMRAD ICT, Australia) was performed simultaneously by an independent investigator. The severity of clinical disease of all patients was evaluated. RESULTS: The study sample comprised 328 individuals of whom 126 (38%) were infected, 102 with P. vivax (31.1%) and 24 with P. falciparum (7.3%). The RDT was found to be highly sensitive (100%) and specific (100%) for the diagnosis of P. falciparum when compared with field microscopy. The sensitivity for the diagnosis of P. vivax malaria was only 70%. When P. vivax parasitaemia was greater than 5000 parasites/microL the RDT was 96.2% sensitive. A significant association was noted between the band intensity on the dipstick and both peripheral blood parasitaemia (p < 0.001) and clinical severity of disease with P. vivax (p = 0.011). CONCLUSIONS: The ICT Malaria P.f/P.v test can be used in Sri Lanka in the absence of microscopists.

Adolescent↗
PubMed1998

Malaria diagnosis by dipstick assay in a Honduran population with coendemic Plasmodium falciparum and Plasmodium vivax.

A Plasmodium lactate dehydrogenase dipstick designed to separately detect P. falciparum and P. vivax malaria was evaluated in two Honduran populations where both species are endemic. The dipstick was compared to thick film microscopy; the polymerase chain reaction (PCR) was used to analyze discordant results. The dipstick had a sensitivity of 100% and a specificity of 95% compared with microscopy in the diagnosis of Plasmodium infections in a hospital population; the mean parasite density was approximately 590/mm3. In a field sample of mostly asymptomatic volunteers, the sensitivity of the dipstick for Plasmodium infection varied with parasite density. Additionally, the sensitivity and specificity of the dipstick was similar to thick film microscopy in the diagnosis of vivax malaria compared with the PCR. The dipstick was unable to detect P. vivax in the presence of P. falciparum because of cross-reactivity in the pan-specific band. Accurate species identification in mixed infections remains a problem in malaria diagnosis.

Clinical Enzyme Tests↗
PubMed1995

Resurgence of malaria and drug resistance in plasmodium falciparum and plasmodium vivax species in Bombay.

Malaria had been well controlled in Bombay, through control of mosquito breeding sites and legal provisions. However in the past 2-3 years there has been a marked increase in incidence of malaria in Bombay. The objective of the present study was to assess the incidence of drug resistance of malarial parasite to standard drugs. The study was an outpatient study, but drug administration was supervised, blood smear was read by experienced technicians counting at least 100 fields. Follow up was done upto day 14 as beyond that, smear positivity due to reinfection cannot be ruled out. Two hundred cases; 56 of P. falsiparum, 139 of P. vivax and 5 with mixed infection were investigated. The public health department strategy of administering single dose of (10 mg/kg) chloroquine found to be largely effective in the past was now found to be only partially effective, with 20/56 Pl. falciparum, 7/139 P. vivax and 1/5 mixed infection cases showing smear positive on day 6 or day 14. These patients, resistant to single dose chloroquine, were then treated with full dose of (25 mg/kg) chloroquine. Three out of 20 cases of P. falciparum and 1/7 P. vivax cases did not respond to full dose (25 mg/kg) of chloroquine. These 3 chloroquine resistant cases of P. falciparum responded to Sulfadoxinepyrimethamine while the single case of chloroquine resistant P. vivax did not respond to quinine or sulfadoxinepyrimethamine.

Adolescent↗