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Title: A seroepidemiological study of human antibodies to the major merozoite surface coat precursor protein of Plasmodium falciparum (GP195) from a hyperendemic area of the Philippines 
Author: Kramer, Kenton Jay
Date: 1990
Abstract: The seroepidemiology of the major merozoite surface coat antigen (gp195) was investigated in a human population living on the island of Palawan, Philippines. A strain of Plasmodium falciparum (Pf857), isolated from Palawan, was used as a source of gp195 antigens. Malaria surveys were conducted in the Napsan region of Palawan during June and September 1986. In total, one thousand four-hundred and fifty-eight individuals were screened for anti-gp195 antibodies using an enzyme immunoassay (EIA). The results of the June and September surveys were comparable. Approximately 90% of the people tested had anti-gp195 antibodies. The lowest seroprevalence (approximately 78%) was found in the 0-4 year old age group. By age group 10-19 years the seroprevalence of anti-gp195 antibodies had plateaued near 90%. Anti-gp195 antibody titers were determined from 59 randomly selected individuals using an EIA. The anti-gp195 antibody titers ranged from zero to 1/102,400. Anti-gp195 antibody titers increased with age (r = 0.355, p < 0.01). The lowest antibody titers were found in the 0-4 year old age group. The 5-9 year old age group had anti-gp195 antibody titers comparable with the older age groups. similar results were also obtained using two yeast recombinant polypeptides based on the gp195 amino acid sequence. This suggests that the recombinant polypeptides share some B cell epitopes with the native protein. Immunoblotting experiments, using gp195 polypeptides, revealed that all the serum samples tested had antibodies to the gp195 precursor (195-kDa). However, only individuals with anti-gp195 EIA titers greater than 1/400 had antibodies against the 42-kDa processing fragment. This implies that this fragment is either poorly immunogenic or partially hidden from the immune system. This finding is important and may explain Why immunity to P. falciparum is acquired only after repeated exposures. Future work should concentrate on the role of the 42-kDa processing fragment in immunity to P. falciparum. No significant differences were found in the anti-gp195 EIA titers or immunoblot patterns against gp195 between individuals with a positive P. falciparum blood film and those with a negative slide. This implies that if antibodies are important in immunity, the relevant antibodies are probably recognizing a limited number of specific gp195 epitopes.
Description: Typescript. Thesis (Ph. D.)--University of Hawaii at Manoa, 1990. Includes bibliographical references (leaves 122-133) Microfiche. xvi, 133 leaves, bound ill. 29 cm
Rights: All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Keywords: Malaria -- Immunological aspects -- Philippines, Malaria -- Philippines

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