A Longitudinal Study of Human Antibody Responses to Plasmodium falciparum Rhoptry-Associated Protein 1 in a Region of Seasonal and Unstable Malaria Transmission
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Date
2015-11-15
Authors
Elhassan, Ibrahim M
Cavanagh, David Ronald
Roper, Cally
Theander, Thor G
Journal Title
Journal ISSN
Volume Title
Publisher
University of Khartoum
Abstract
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.
Description
Keywords
Human, Plasmodium, Malaria Transmission