Acquisition, maintenance and adaptation of invasion inhibitory antibodies against Plasmodium falciparum invasion ligands involved in immune evasion

PLoS One. 2017 Aug 7;12(8):e0182187. doi: 10.1371/journal.pone.0182187. eCollection 2017.

Abstract

Erythrocyte-binding antigens (EBAs) and P. falciparum reticulocyte-binding homologue proteins (PfRhs) are two important protein families that can vary in expression and utilization by P. falciparum to evade inhibitory antibodies. We evaluated antibodies at repeated time-points among individuals living in an endemic region in Nigeria over almost one year against these vaccine candidates. Antibody levels against EBA140, EBA175, EBA181, PfRh2, PfRh4, and MSP2, were measured by ELISA. We also used parasites with disrupted EBA140, EBA175 and EBA181 genes to show that all these were targets of invasion inhibitory antibodies. However, antigenic targets of inhibitory antibodies were not stable and changed substantially over time in most individuals, independent of age. Antibodies levels measured by ELISA also varied within and between individuals over time and the antibodies against EBA181, PfRh2 and MSP2 declined more rapidly in younger individuals (≤15 years) compared with older (>15). The breadth of high antibody responses over time was more influenced by age than by the frequency of infection. High antibody levels were associated with a more stable invasion inhibitory response, which could indicate that during the long process of formation of immunity, many changes not only in levels but also in functional responses are needed. This is an important finding in understanding natural immunity against malaria, which is essential for making an efficacious vaccine.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aging / immunology
  • Antibodies, Protozoan / blood*
  • Antigens, Protozoan / immunology*
  • Child
  • Child, Preschool
  • Endemic Diseases
  • Humans
  • Immune Evasion*
  • Immunoglobulin G / blood
  • Kaplan-Meier Estimate
  • Longitudinal Studies
  • Malaria, Falciparum / epidemiology
  • Malaria, Falciparum / immunology*
  • Middle Aged
  • Nigeria
  • Plasmodium falciparum / immunology*
  • Protozoan Proteins / blood
  • Protozoan Proteins / immunology*
  • Seasons
  • Young Adult

Substances

  • Antibodies, Protozoan
  • Antigens, Protozoan
  • Immunoglobulin G
  • Protozoan Proteins

Grants and funding

Multilateral Initiative on Malaria (MIM) project A60143 through UNICEF/UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Disease (TDR), and the National Health and Medical Research Council of Australia, University of Ibadan Senate Research Grant, Myndigheten för Samhällsskydd och Beredskap, Svenska Läkaresällskapet, Sida and Vetenskapsrådet. J. Beeson was supported by a Senior Research Fellowship and Program Grant from the National Health and Medical Research Council of Australia, and the Burnet Institute is supported by the Victorian State Government Operational Infrastructure Scheme, and the NHMRC Independent Research Institutes Infrastructure Support scheme.