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Title:Identification, characterization and amino terminal sequencing of high molecular weight soluble antigens of the human malaria parasite, Plasmodium falciparum
Author(s):Nichols, James Harold
Doctoral Committee Chair(s):Hager, Lowell P.
Department / Program:Biochemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Biochemistry
Health Sciences, Immunology
Abstract:Plasmodium falciparum is the most lethal of four species of protozoa that cause malaria in humans. Since the blood stage of the parasite life cycle is responsible for the clinical manifestations of the disease, studies of the immune response and vaccine development to this stage are critical to decreasing the morbidity and mortality of malaria. Immunization of experimental monkeys with crude supernatant fractions obtained from in vitro culture media or partially purified fractions of culture media have been shown to protect them from malaria. Protective immunity is known to occur naturally in afflicted adolescent and adult individuals only after long-term exposure to malaria.
This research focuses on soluble antigens, termed exoantigens, secreted into the supernatant of in vitro blood stage cultures. These exoantigens are believed to either be shed or secreted from the parasite surface during red blood cell invasion. The goal of this research was to identify and characterize those exoantigens capable of eliciting an antibody response which could act as potential vaccine target antigens.
Crude supernatant from normal uninfected red blood cell lysates and human sera, or from cultures infected with the Vietnamese (Indochina I) strain of Plasmodium falciparum were fractionated in parallel by HPLC gel filtration and DEAE ion exchange chromatography. Western blots were performed on the infected and control fractions using an African human sera pool obtained from adult individuals with confirmed long-term exposure to Plasmodium falciparum. Sixteen antigens were identified in the range of 100-250 Kd under reducing SDS conditions. These exoantigens were further reactive against pools of sera from Malaysian and Venezuelan adults with long-term exposure. The reactive to immune sera from three continents indicates the potential of these proteins as vaccine candidate antigens.
In order to characterize these exoantigens, a large-scale preparation of 5 liters of infected culture supernatant was fractionated by high resolution gel filtration, ammonium sulfate precipitation and preparative isoelectric focusing. Their isoelectric points were determined to range from 5.2-6.0. The partially purified fractions containing the high molecular weight antigens were resolved by SDS PAGE sequencing length gels, blotted onto activated glass fiber filters and individual bands submitted for amino-terminal sequencing. Unique amino-terminal sequences demonstrate that these proteins are a new group of previously uncharacterized exoantigens.
Issue Date:1990
Rights Information:Copyright 1990 Nichols, James Harold
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9026281
OCLC Identifier:(UMI)AAI9026281

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