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Biomedical subjects

W E Collins

Publications and source records attributed to W E Collins.

At least 163 records · Page 9Linked to original sources
PubMed1987

Induction of sporozoite-specific memory cells in mice immunized with a recombinant Plasmodium vivax circumsporozoite protein.

A recombinant Plasmodium vivax circumsporozoite (CS) protein (rPvCS-1) has been investigated as a possible malaria sporozoite vaccine candidate. Experiments were carried out to determine whether sporozoite-specific memory cells develop in Swiss Webster mice immunized with rPvCS-1. Challenge of rPvCS-1-immunized mice with P. vivax sporozoites resulted in a 100-fold increase in the mean serum anti-sporozoite antibody titer. The presence of parasite-specific T helper cells was demonstrated using an in vitro assay. Anti-CS antibodies were detected in the culture supernatants of spleen cells of rPvCS-1-immunized mice following in vitro challenge with P. vivax sporozoite extract. Immune spleen cells depleted of T cells did not produce antibodies when challenged with sporozoite extract in vitro. In conclusion, immunization of mice with the rPvCS-1 protein induced memory T cells which recognized native CS antigen and functioned as T helper cells in the production of anti-sporozoite antibodies both in vivo and in vitro.

Animals↗
PubMed1987

Plasmodium ovale: in vitro development of hepatic stages.

Primary cultures of human hepatocytes, a culture-derived clone from the human hepatoma Hep G2 line, and cultured rat hepatocytes were inoculated in vitro with Plasmodium ovale sporozoites extracted from Anopheles stephensi, An. gambiae, and An. dirus mosquitoes. Penetration and differentiation of P. ovale sporozoites into trophozoite stage parasites occurred in all three cell types, but with a lower transformation rate in the Hep G2 cell line than in the primary cultured hepatocytes. Further maturation was obtained only in the human hepatocytes, in which the parasites were uninucleate until the third day after infection, before development to 60 micron in length by the eighth day. Additionally, this culture system was used to assess the ability of an anti-P. ovale sporozoite monoclonal antibody to inhibit penetration of sporozoites into hepatocytes and to detect sporozoite determinants in the maturing liver stage parasites.

Animals↗
PubMed1987

Plasmodium vivax: exoerythrocytic schizonts recognized by monoclonal antibodies against blood-stage schizonts.

Exoerythrocytic parasites of Plasmodium vivax grown in human hepatoma cells in vitro were probed with monoclonal antibodies raised against other stages of P. vivax. Monoclonal antibodies specific for four independent antigens on blood-stage merozoites all reacted with exoerythrocytic schizonts and merozoites by immunostaining. The characteristic staining pattern of each monoclonal antibody was similar on both blood- and exoerythrocytic-stage parasites and appeared only in mature schizont segmenters. In contrast, a monoclonal antibody specific for the caveolar-vesicle complex of the infected host cell membrane and a second monoclonal antibody reacting with an unknown internal antigen did not appear to react with exoerythrocytic parasites. We confirm prior reports that monoclonal antibodies against the sporozoite immunodominant repeat antigen react with all exoerythrocytic-stage parasites, but note that as the exoerythrocytic parasite matures the immunostaining is concentrated in plaques reminiscent of germinal centers and apparently distinct from mature merozoites. These results indicate that mature merozoites from either exoerythrocytic or blood-stage parasites are antigenically very similar, but that stage-specific antigens may be found in specialized structures present only in a specific host cell type.

Animals↗
PubMed1987

Characterization of Plasmodium falciparum cloned lines with respect to gametocyte production in vitro, infectivity to Anopheles mosquitoes, and transmission to Aotus monkeys.

The production of gametocytes in vitro and their subsequent infectivity to mosquitoes by 3 cloned lines of Plasmodium falciparum were studied. 2 of the cloned lines, Honduras I-clone B3 and Indochina III-clone W2, produced mature gametocytes (stage V) that were infective to Anopheles mosquitoes. The third clone, Sierra Leone I-clone D6, produced gametocytes, the majority of which did not develop beyond stage III. Fully mature gametocytes of Sierra Leone I-clone D6 were not infective to mosquitoes. Sporozoites collected from An. freeborni infected with Honduras I-clone B3 were used in transmission studies. Two of three Aotus monkeys were infected after prepatent periods of 19 and 20 d, respectively. This study supports previous reports that cloned lines of P. falciparum contain the full genetic capacity to produce morphologically mature gametocytes. The transmission to Aotus monkeys has also conclusively established that biologically competent gametocytes of both sexes are produced by clones.

Animals↗
PubMed1987

Community-based malaria control in Saradidi, Kenya: description of the programme and impact on parasitaemia rates and antimalarial antibodies.

A community-based malaria control programme initiated in Saradidi, Kenya in 1982 is described. Antimalarial treatment provided by volunteer community health workers was made available in each village. Malaria was holoendemic. Parasitaemia rates by age were high and did not change after the control programme began. Plasmodium falciparum was the most common species and was present alone or mixed in 98.2% of 8105 infections. Virtually all (98.5%) of 2040 blood samples collected in May 1981 were positive (reciprocal titre greater than or equal to 80) to P. falciparum by the indirect fluorescent antibody (IFA) test. Seropositivity rates to P. falciparum in the IFA test or the enzyme-linked immunosorbent assay (ELISA) were high in all age groups and did not change significantly in longitudinal surveys or in a cohort of children zero to nine years old followed at intervals. While the malaria control programme was successful in bringing treatment to each village, malaria prevalence was not reduced. Parasitologic and serologic studies alone were not adequate to describe the impact of the community-based malaria control programme in Saradidi. Morbidity and mortality rates caused by malaria can decline, significantly improving the health of the population, in the absence of any decrease in parasitaemia rates.

Animals↗
PubMed1987

Malaria chemoprophylaxis to pregnant women provided by community health workers in Saradidi, Kenya. III. Serologic studies.

Parasitaemia and antimalarial antibodies were examined from May 1983 to March 1984 in monthly samples taken from 930 pregnant women attending antenatal clinics in Saradidi, Kenya, and 317 of their infants; 104 women were taking chloroquine phosphate 300 mg base weekly for chemoprophylaxis. Seropositivity rates in pregnant women were uniformly high, and mean enzyme-linked immunosorbent assay (ELISA) absorbance values were not related to presence of parasitaemia or history of chemoprophylaxis. Parasitaemia was present in 26.5% of 1677 slides from pregnant women and there was little variation by month of sample. Mean ELISA absorbance values varied by month of sample. Seropositivity rates in infants were high as measured in both the indirect fluorescent antibody (IFA) test (81.6% of 938) and ELISA at 1:100 (83.8% of 1025) and 1:1000 (34.8% of 1025) serum dilutions. Seropositivity rates decreased slightly after birth but by four months of age rates were again high. Parasitaemia was present in 26.5% of 1677 slides from pregnant women. Paired comparisons were made on maternal samples collected less than two months before parturition and samples from the infants collected within two months after birth. The paired antibody response by IFA or ELISA was not dependent on the presence of detectable parasitaemia in the mother. Infants from mothers with a history of antimalarial chemoprophylaxis had significantly (P = 0.04) lower IFA titres than other infants. Measuring the absorbance of a 1:100 serum dilution by ELISA appeared to be an excellent method with which to measure longitudinal serologic changes in a population.

Animals↗
PubMed1987

Ultrastructure of the erythrocytic stages of Plasmodium malariae.

This report describes the fine structure of the erythrocytic stages of Plasmodium malariae. Erythrocytic parasites from a naturally acquired human infection and an experimentally infected chimpanzee were morphologically indistinguishable and structurally similar to other primate malarias. New findings included observations of highly structured arrays of merozoite surface coat proteins in the cytoplasm of early schizonts and on the surface of budding merozoites and the presence of knobs in the membranes of Maurer's clefts. Morphological evidence is presented suggesting that proteins are transported between the erythrocyte surface and intracellular parasites via two routes: one associated with Maurer's clefts for transport of membrane-associated knob material and a second associated with caveolae in the host cell membrane for the import or export of host- or parasite-derived substances through the erythrocyte cytoplasm.

Adolescent↗
PubMed1987

Localization of circumsporozoite protein of Plasmodium ovale in midgut oocysts.

Circumsporozoite (CS) proteins are the major proteins found on the surface of salivary gland sporozoites and are the protective antigens of several species of malaria parasites. Little is known about the distribution of CS proteins in developing oocysts, however. Immunoelectron microscopy with protein A-gold and a monoclonal antibody specific for the CS protein of Plasmodium ovale was performed to investigate the distribution of CS protein within developing P. ovale oocysts. There was an almost complete absence of label in immature oocysts prior to the development of sporoblasts. In contrast, sporoblasts and budding and free sporozoites in mature oocysts were labeled uniformly on the outer surfaces of their plasma membranes, indicating a uniform distribution of CS protein on these membranes. Gold particles were frequently associated with the cytoplasm of sporoblasts and sporozoites, as well as with the inner surface of the oocyst capsule. This is the first evidence that CS protein is present in oocyst sporozoites and sporoblasts of P. ovale.

Animals↗
PubMed1987

Comparison of genomic, plasmid, synthetic, and combined DNA probes for detecting Plasmodium falciparum DNA.

Total genomic Plasmodium falciparum DNA, the plasmid clone pRepHind, and a 21-base-long synthetic DNA probe (PFR1), the sequence of which was derived from pRepHind, were hybridized with DNA from various species of the phylum Apicomplexa. The genomic probe hybridized with P. reichenowi and P. falciparum DNA and significantly cross-hybridized with DNA of all the other Plasmodium species tested. The synthetic and plasmid probes hybridized to P. falciparum DNA and at reduced levels to P. reichenowi but did not hybridize to P. vivax, P. malariae, P. ovale, P. fragile, P. inui, P. knowlesi, Babesia bovis, B. microti, B. bigemina, Anopheles sp., Pan sp., Aotus sp., or human DNA. Southern blot analysis indicated that approximately 60 distinct restriction enzyme fragments from P. falciparum DNA were similarly detected by PFR1 and pRepHind. A method was developed by using a second brief hybridization with synthetic DNA to amplify signals from samples that were previously hybridized with plasmid-borne repetitive DNA. This amplification procedure was shown to allow the detection of 0.005% P. falciparum parasitemias from 10-microliter samples of blood from patients in Kenya.

Animals↗
PubMed1987

In vitro and in vivo adaptation of the Geneve/SGE-1 strain of Plasmodium falciparum to growth in a squirrel monkey (Saimiri sciureus) model.

Human erythrocytic culture-adapted parasites of the Geneve/SGE-1 strain of Plasmodium falciparum were successfully adapted to grow in an in vitro culture system containing squirrel monkey erythrocytes and serum. These monkey culture-adapted organisms were then used to produce a patent infection in a splenectomized squirrel monkey. Fresh infected blood from this animal was introduced into another splenectomized monkey and was subsequently serially passed through seven intact squirrel monkeys. High level parasitemias (greater than 10%) were obtained in the animals from the last two passes following inoculation of moderate numbers of parasites. It is anticipated that this squirrel monkey-adapted Geneve/SGE-1 strain of P. falciparum will continue to produce high level parasitemias in intact Bolivian Saimiri, and consequently will be suitable for challenge of these monkeys.

Animals↗
PubMed1987

Assessment of a synthetic DNA probe for Plasmodium falciparum in African blood specimens.

Synthetic DNA oligomers homologous to 21-base long repetitive sequences of Plasmodium falciparum DNA were labeled with 32P using T4 kinase, and were hybridized with purified DNA and with processed blood samples from Africa. The sequence PFR1, its antiparallel oligomer PFR1R, and PFR1 covalently attached to biotin hybridized similarly to P. falciparum DNA. One-microliter aliquots of blood from Zaire spotted on prewet nylon filters and hybridized with PFR1 gave detectable autoradiogram signals from samples with parasitemias as low as 1,000 parasites/mm3. Blood lysis and protein digestion followed by alkylation allowed dot-blot processing of larger aliquots of blood. After hybridization with PFR 1 and autoradiography, 26 samples were scored positive visually, compared with 34 scored positive by microscopy. The effective sensitivity for processed 10-microliter samples was about 500 parasites/mm3. Signals from hybridized probes were quantitated by liquid scintillation counting and densitometry, and were proportional to the amounts of purified P. falciparum DNA applied to the filter. Autoradiogram signals also were roughly proportional (correlation coefficient, r = 0.77) to the number of parasites/mm3 of blood from field samples as determined by microscopic examination.

Animals↗
PubMed1987

Infection of chimpanzees with Nigerian I/CDC strain of Plasmodium ovale.

Seven splenectomized chimpanzees were infected with the Nigerian I/CDC strain of Plasmodium ovale. Two of the animals had no history of previous malarial infection whereas three had been infected with P. vivax, one with P. malariae, and one with P. vivax and P. malariae. The two animals with no previous malarial experience had maximum parasitemias of 88,700 and 127,000 per mm3 while the other animals had maximum parasitemias ranging from 10,100 to 60,600 per mm3. Anopheles freeborni, An. dirus, An. stephensi, and An. gambiae were readily infected via membrane feeding on heparinized blood obtained from these chimpanzees during the ascending phases of their primary attacks. The parasitemias in the chimpanzees with previous malarial experience were transient.

Animals↗
PubMed1987

Antibodies to Pf155, a major antigen of Plasmodium falciparum: longitudinal studies in humans.

Antibodies to Pf155, a major Plasmodium falciparum antigen detected in the membrane of glutaraldehyde-fixed and air-dried erythrocytes infected with P. falciparum, were studied in serum samples collected from patients treated for neurosyphilis by induced P. falciparum infection. In 3 patients with no previous documented exposure to malaria, the antibodies were detected late and reached low titers. In 5 patients with extensive previous malaria infections, the antibodies appeared rapidly and reached high titers. The immunofluorescence findings were confirmed by immunoblots. No correlation was observed between antibodies to Pf155 and antibodies detected by standard immunofluorescence with whole parasite antigen.

Adult↗
PubMed1987

Infection of Aotus vociferans (karyotype V) monkeys with different strains of Plasmodium vivax.

Twenty splenectomized Aotus vociferans (karyotype V) monkeys were infected with strains of Plasmodium vivax from New Guinea, North Korea, Indonesia, El Salvador, and Honduras. Peak parasite densities ranged from 4,840 to 75,500 per mm3. Gametocytes infective to different species of mosquitoes were produced with all strains of P. vivax studied. Two transmissions of the Chesson strain of P. vivax were made by the intravenous inoculation of dissected sporozoites from An. dirus mosquitoes. Prepatent periods were 16 days.

Animals↗
PubMed1987

Chesson strain Plasmodium vivax in Saimiri sciureus boliviensis monkeys.

Nine Saimiri sciureus boliviensis monkeys were inoculated with sporozoites of Plasmodium vivax (Chesson strain) dissected from Anopheles stephensi mosquitoes infected by feeding on blood from infected chimpanzees. The animals were splenectomized 7 days after inoculation. Seven animals developed infections with prepatent periods ranging from 12 to 43 days (mean of 19.6 days). Parasitemias were low during the first 50 days. Maximum parasitemias in 5 animals in which the strain adapted ranged from 10,000 to 46,800 per mm3. Anopheles freeborni mosquitoes were infected by feeding on 4 of the monkeys.

Animals↗
PubMed1987

Ex vivo platelet deposition on fibronectin-preadsorbed surfaces.

Temporal platelet deposition profiles of canine plasma fibronectin (CPFN) adsorbed to different polymers ex vivo and the in vitro characteristics of CPFN adsorption were studied in an attempt to correlate the two. The maximum platelet deposition (gamma pltmax) obtained at a protein preadsorption time of 30 min was greater than that obtained using an adsorption time of 120 min for all surfaces studied. At 30 min of preadsorption, gamma pltmax was 520,560 and 1230 platelets/1000 micron2 on Biomer, polyethylene (PE) and oxidized PE (OXPE), respectively. In contrast, the platelet deposition at 120 min. of fibronectin preadsorption was about 60 approximately 90 platelets/1000 micron2 on all polymers studied. The surface concentrations of adsorbed CPFN measured using 125I-CPFN, were in the order PE greater than OXPE greater than Biomer. The adsorbed protein concentration increased with increasing adsorption time. The surface distribution of adsorbed CPFN was visualized with antibody-labelled colloidal gold and scanning electron microscopy. The extent of staining was lowest on PE, greater on Biomer, and highest on OXPE, roughly similar to the order of platelet deposition. Platelet deposition ex vivo appears to correlate with the immunogold-stainable-adsorbed protein rather than with the total amount of adsorbed protein.

Adsorption↗
PubMed1987

Some effects of alcohol and simulated altitude on complex performance scores and breathalyzer readings.

Each of 17 men was trained on 7 tasks in the Multiple Task Performance Battery and then performed over a 2-week period in four experimental sessions: ground level with and without alcohol, and simulated altitude (12,500 ft), with and without alcohol. Subjects breathed appropriate gas mixtures through oxygen masks at both ground level and altitude. Alcohol doses of 100-proof vodka mixed with juice 2.2 ml X kg-1 of body weight. Results showed no differential effect of simulated altitude on breathalyzer readings (peaks averaged 78 mg % at 12,500 ft and 77 mg % at ground level). The best performance occurred at ground level under placebo conditions; the 12,500-ft simulated altitude produced some decrement for placebo scores. Alcohol at ground level resulted in significantly impaired performance during the morning sessions; the addition of altitude to the alcohol condition further depressed performance scores, but to about the same extent that placebo scores were depressed by altitude. Thus, there was no synergistic interactive effect of alcohol and altitude on either breathalyzer readings or performance scores.

Adult↗