Long-lived Plasmodium falciparum specific memory B cells in naturally exposed Swedish travelers

Authors

  • Francis M. Ndungu,

    Corresponding author
    1. Centre for Geographical Medicine Research (Coast), Kenya Medical Research Institute, Kilifi, Kenya
    2. Centres for Clinical Vaccinology and Tropical Medicine, Nuffield Department of Medicine, University of Oxford, Oxford, UK
    • Full correspondence: Dr. Francis M. Ndungu, KEMRI-Centre for Geographic Medicine Research Coast, P.O Box 230-80108, Kilifi, Kenya

      Fax: +254-417522390

      e-mail: FNdungu@kemri-wellcome.org

      Additional correspondence: Dr. Anna Färnert, Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institute, Karolinska University Hospital, SE-17176 Stockholm, Sweden

      e-mail: anna.farnert@ki.se

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  • Klara Lundblom,

    1. Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institute, Stockholm, Sweden
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  • Josea Rono,

    1. Centre for Geographical Medicine Research (Coast), Kenya Medical Research Institute, Kilifi, Kenya
    2. Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institute, Stockholm, Sweden
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  • Joseph Illingworth,

    1. Centres for Clinical Vaccinology and Tropical Medicine, Nuffield Department of Medicine, University of Oxford, Oxford, UK
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  • Sara Eriksson,

    1. Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institute, Stockholm, Sweden
    2. Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden
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  • Anna Färnert

    Corresponding author
    1. Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institute, Stockholm, Sweden
    2. Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden
    • Full correspondence: Dr. Francis M. Ndungu, KEMRI-Centre for Geographic Medicine Research Coast, P.O Box 230-80108, Kilifi, Kenya

      Fax: +254-417522390

      e-mail: FNdungu@kemri-wellcome.org

      Additional correspondence: Dr. Anna Färnert, Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institute, Karolinska University Hospital, SE-17176 Stockholm, Sweden

      e-mail: anna.farnert@ki.se

    Search for more papers by this author

Abstract

Antibodies (Abs) are critical for immunity to malaria. However, Plasmodium falciparum specific Abs decline rapidly in absence of reinfection, suggesting impaired immunological memory. This study determines whether residents of Sweden that were treated for malaria following international travel maintained long-lasting malaria-specific Abs and memory B cells (MBCs). We compared levels of malaria-specific Abs and MBCs between 47 travelers who had been admitted with malaria at the Karolinska University Hospital between 1 and 16 years previously, eight malaria-naïve adult Swedes without histories of travel, and 14 malaria-immune adult Kenyans. Plasmodium falciparum-lysate-specific Ab levels were above naïve control levels in 30% of the travelers, whereas AMA-1, merozoite surface protein-142, and merozoite surface protein-3-specific Ab levels were similar. In contrast, 78% of travelers had IgG-MBCs specific for at least one malaria antigen (59, 45, and 28% for apical merozoite antigen-1, merozoite surface protein-1, and merozoite surface protein-3, respectively) suggesting that malaria-specific MBCs are maintained for longer than the cognate serum Abs in the absence of re-exposure to parasites. Five travelers maintained malaria antigen-specific MBC responses for up to 16 years since the diagnosis of the index episode (and had not traveled to malaria-endemic regions in the intervening time). Thus P. falciparum can induce long-lasting MBCs, maintained for up to 16 years without reexposure.

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