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Infection and Immunity, June 1999, p. 2975-2985, Vol. 67, No. 6
Institute of Cell, Animal and Population Biology,
University of Edinburgh, Edinburgh EH9 3JT,
Scotland1; Centre for Medical
Parasitology at the Institute for Medical Microbiology and Immunology,
University of Copenhagen and RHIMA Centre, Copenhagen University
Hospital (Rigshospitalet), Copenhagen, Denmark2;
Institute of Endemic Diseases, University of Khartoum,
Khartoum, Sudan3; and Department of
Infectious and Tropical Disease, London School of Hygiene and
Tropical Medicine, London, England4
Received 26 October 1998/Returned for modification 15 December
1998/Accepted 26 March 1999
Rhoptry-associated protein 1 (RAP1) of Plasmodium
falciparum is a nonpolymorphic merozoite antigen that is
considered a potential candidate for a malaria vaccine against asexual
blood stages. In this longitudinal study, recombinant RAP1 (rRAP1)
proteins with antigenicity similar to that of P. falciparum-derived RAP1 were used to analyze antibody responses
to RAP1 over a period of 4 years (1991 to 1995) of 53 individuals
naturally exposed to P. falciparum malaria. In any 1 year
during the study, between 23 and 39% of individuals who had malaria
developed immunoglobulin G (IgG) antibodies detectable with at least
one rRAP1 protein. However, the anti-RAP1 antibody responses were
detected only during or shortly after clinical malarial infections.
RAP1 antibody levels declined rapidly (within 1 to 2 months) following
drug treatment of the infections. No anti-RAP1 antibodies were usually
detected a few months after the end of malaria transmission, during the dry season, or by the start of the next malaria season. Thus, RAP1 IgG
responses were very short-lived. The short duration of RAP1 antibody
response may explain the apparent lack of response in a surprisingly
high proportion of individuals after clinical malarial infections. For
some individuals who experienced more than one malarial infection, a
higher anti-RAP1 antibody response to subsequent infections than to
earlier infections was observed. This suggested secondary responses to
RAP1 and thus the development of immunological memory for RAP1.
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
A Longitudinal Study of Human Antibody Responses to
Plasmodium falciparum Rhoptry-Associated Protein 1 in a
Region of Seasonal and Unstable Malaria Transmission

*
Corresponding author. Mailing address: Institute of
Cell, Animal and Population Biology, University of Edinburgh, King's
Buildings, West Mains Rd., Edinburgh EH9 3JT, Scotland. Phone: 44 131 650 5494. Fax: 44 131 667 3210. E-mail: JMCBRIDE{at}ed.ac.uk.
Present address: HIV/Retrovirus Disease Branch, Centers for Disease
Control and Prevention, Atlanta, Ga.
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