Plasmodium vivax:asexual erythrocytic stage antigens
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Date
1989
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Publisher
University of Colombo: UC(MED).
Abstract
AB. : A panel of 34 monoclonal antibodies (Mabs) established against the asexual erythrocytic (AE) stages of Plasmodium vivax was used to identify and characterize the antigenic profile of this parasite stage. These Mabs allowed the characterization of at least 38 different antigenic polypeptides, their relative molecular weights ranging from 14 to 225 kDa as ascertained by Western blotting. Classification of 6 distinct immunofluorescence staining patterns obtained with these Mabs led to formulate assumptions on the probable localization of the corresponding antigenic determinants with respect to the parasite and the infected erythrocyte. Stage specificities of these Mabs were established and cross reactivities with AE stages of 3 other plasmodial species, viz. P. cynomolgi, P. falciparum and P. fragile were determined by the indirect immunofluorescence test (IFT). An antigen associated with the caveola-vesicle complexes which are associated with Schuffner's dots on the infected erythrocyte was identified and characterized using one of these Mabs. Another antigen GAM-1, common to both asexual and sexual stages of P. vivax which has now been designated as a potential transmission blocking vaccine candidate was also identified. The analogue in P. vivax of the class of high molecular weight polymorphic schizont surface antigen, PV200 was described. Reactivity of this battery of MAbs by the IFT with 50 different P. vivax primary isolates originating from 16 different geographical districts of Sri Lanka indicated a high degree of polymorphism among these antigens in natural parasite isolates. While 6 epitopes were found to be conserved among more than 80 percent of the isolates examined, the rest were found to be divetse to varying degrees. Both epitope and size polymorphism were demonstrated in these parasite antigens. Mabs against variant epitopes of PV200 were used to analyze the variety of serotypes (genetically distinct populations) in individual P. vivax infections in Sri Lanka, by the IFT. Individual parasites were typed with respect to their reactivity with 2 Mabs (of different isotype specificities) at a time, by double staining with isotype specific chromatophores, fluoresceine and rhodamine. This technique allowed the detection of minor subpopulations representing at least 5 percent of the total parasite population within an isolate. In 9 out of 10 isolates examined parasities of only a single serotypically distinct between isolates. In one isolate parasite populations of 3 distinct serotypes were identified. Thus most P. vivax infections appeared to consist of a single genetically homogeneous population of parasites within the limits of detection of the technique used.
Description
Dissertation: PhD, University of Colombo: UC(MED), 1989.
Keywords
Malaria
Citation
UDAGAMA, PV, Plasmodium vivax:asexual erythrocytic stage antigens, University of Colombo UC(MED), 1989: vii,357p.