High antibody responses against Plasmodium falciparum in immigrants after extended periods of interrupted exposure to malaria

PLoS One. 2013 Aug 14;8(8):e73624. doi: 10.1371/journal.pone.0073624. eCollection 2013.

Abstract

Background: Malaria immunity is commonly believed to wane in the absence of Plasmodium falciparum exposure, based on limited epidemiological data and short-lived antibody responses in some longitudinal studies in endemic areas.

Methods: A cross-sectional study was conducted among sub-Saharan African adults residing in Spain for 1 up to 38 years (immigrants) with clinical malaria (n=55) or without malaria (n=37), naïve adults (travelers) with a first clinical malaria episode (n=20) and life-long malaria exposed adults from Mozambique (semi-immune adults) without malaria (n=27) or with clinical malaria (n=50). Blood samples were collected and IgG levels against the erythrocytic antigens AMA-1 and MSP-1₄₂ (3D7 and FVO strains), EBA-175 and DBL-α were determined by Luminex. IgG levels against antigens on the surface of infected erythrocytes (IEs) were measured by flow cytometry.

Results: Immigrants without malaria had lower IgG levels than healthy semi-immune adults regardless of the antigen tested (P≤0.026), but no correlation was found between IgG levels and time since migration. Upon reinfection, immigrants with malaria had higher levels of IgG against all antigens than immigrants without malaria. However, the magnitude of the response compared to semi-immune adults with malaria depended on the antigen tested. Thus, immigrants had higher IgG levels against AMA-1 and MSP-1₄₂ (P≤0.015), similar levels against EBA-175 and DBL-α, and lower levels against IEs (P≤0.016). Immigrants had higher IgG levels against all antigens tested compared to travelers (P≤0.001), both with malaria.

Conclusions: Upon cessation of malaria exposure, IgG responses to malaria-specific antigens were maintained to a large extent, although the conservation and the magnitude of the recall response depended on the nature of the antigen. Studies on immigrant populations can shed light on the factors that determine the duration of malaria specific antibody responses and its effect on protection, with important implications for future vaccine design and public health control measures.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Antibodies, Protozoan / blood*
  • Antibodies, Protozoan / immunology*
  • Antigens, Protozoan / immunology
  • Emigrants and Immigrants / statistics & numerical data*
  • Environmental Exposure / statistics & numerical data*
  • Female
  • Humans
  • Immunoglobulin G / blood
  • Immunoglobulin G / immunology
  • Malaria, Falciparum / blood
  • Malaria, Falciparum / immunology*
  • Male
  • Plasmodium falciparum / immunology*
  • Plasmodium falciparum / physiology*
  • Species Specificity
  • Time Factors
  • Travel

Substances

  • Antibodies, Protozoan
  • Antigens, Protozoan
  • Immunoglobulin G

Grants and funding

The study received financial support from the Ministerio de Ciencia e Innovación (SAF2008-00743, salary support RYC-2008-02631 to C.D.); the Instituto de Salud Carlos III (PI050275, PS0901113, salary support CD10/00156 to G.M. and CP-4/00220 to A.M.); the Agència de Gestió d’Ajuts Universitaris i de Recerca (2009SGR934, 2009SGR385, salary support 2010FI_B 00168 to J.C.); and the Fundación Ramón Areces. The Centro de Investigação em Saúde de Manhiça receives core support from the Spanish Agency for International Cooperation and Development (AECID). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.