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Protective human immunity as a vaccine discovery tool for falciparum malaria
Author(s) -
Nixon Christian P.,
Friedman Jennifer F.,
Knopf Paul M.,
Duffy Patrick E.,
Kurtis Jonathan D.
Publication year - 2005
Publication title -
transfusion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.045
H-Index - 132
eISSN - 1537-2995
pISSN - 0041-1132
DOI - 10.1111/j.1537-2995.2005.00540.x
Subject(s) - malaria , parasitemia , plasmodium falciparum , rhoptry , antibody , immunology , antigen , immunity , virology , biology , medicine , immune system , apicomplexa
BACKGROUND: Plasmodium falciparum malaria remains a leading cause of morbidity and mortality in developing countries, and malaria‐associated severe anemia is the major factor driving the high transfusion requirements in pediatric populations living in endemic areas. STUDY DESIGN AND METHODS: In this report, we identify and evaluate the targets of naturally acquired protective antibody responses in a cohort of n = 143 male volunteers residing in a P. falciparum holoendemic area of western Kenya. Volunteers were drug‐cured of current malaria infection, blood was collected 2 weeks after treatment, and blood smears were collected weekly for 18 weeks. We identified and pooled plasma from the 10 most resistant (RP) and the 7 most susceptible individuals (SP) and utilized these pools in a differential screen of a P. falciparum cDNA expression library. We screened 550,000 clones and identified 7 clones that were uniquely recognized by RP but not by SP. Two clones encoded a C‐terminal region polypeptide from rhoptery‐associated membrane antigen (RAMA‐pr), a recently described rhoptry‐associated membrane antigen. RESULTS: We measured RAMA‐pr antibody levels in plasma obtained 2 weeks after treatment. Individuals with detectable immunoglobulin G 1 anti‐RAMA‐pr (n = 24) had fewer positive blood films (p < 0.003) and 43 percent lower density of parasitemia (p < 0.02) than individuals with undetectable (n = 115) antibody levels. CONCLUSION: RAMA‐pr is a rationally identified vaccine candidate preferentially recognized by antibodies produced by humans with a high level of naturally acquired resistance to P. falciparum infection. Our results demonstrate that naturally acquired protective antibody responses are useful tools to identify vaccine candidates for falciparum malaria.