Acquisition of Growth-Inhibitory Antibodies Against Blood-Stage Plasmodium Falciparum

PLoS One. 2008;3(10):e3571. doi: 10.1371/journal.pone.0003571. Epub 2008 Oct 29.

Abstract

Background: Antibodies that inhibit the growth of blood-stage Plasmodium falciparum may play an important role in acquired and vaccine-induced immunity in humans. However, the acquisition and activity of these antibodies is not well understood.

Methods: We tested dialysed serum and purified immunoglobulins from Kenyan children and adults for inhibition of P. falciparum blood-stage growth in vitro using different parasite lines. Serum antibodies were measured by ELISA to blood-stage parasite antigens, extracted from P. falciparum schizonts, and to recombinant merozoite surface protein 1 (42 kDa C-terminal fragment, MSP1-42).

Results: Antibodies to blood-stage antigens present in schizont protein extract and to recombinant MSP1-42 significantly increased with age and were highly correlated. In contrast, growth-inhibitory activity was not strongly associated with age and tended to decline marginally with increasing age and exposure, with young children demonstrating the highest inhibitory activity. Comparison of growth-inhibitory activity among samples collected from the same population at different time points suggested that malaria transmission intensity influenced the level of growth-inhibitory antibodies. Antibodies to recombinant MSP1-42 were not associated with growth inhibition and high immunoglobulin G levels were poorly predictive of inhibitory activity. The level of inhibitory activity against different isolates varied.

Conclusions: Children can acquire growth-inhibitory antibodies at a young age, but once they are acquired they do not appear to be boosted by on-going exposure. Inhibitory antibodies may play a role in protection from early childhood malaria.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Animals
  • Antibodies, Protozoan / blood*
  • Child
  • Child, Preschool
  • Cohort Studies
  • Humans
  • Immunity, Innate / immunology
  • Kenya / epidemiology
  • Life Cycle Stages / immunology*
  • Malaria, Falciparum / blood*
  • Malaria, Falciparum / epidemiology
  • Malaria, Falciparum / immunology*
  • Malaria, Falciparum / parasitology
  • Middle Aged
  • Plasmodium falciparum / growth & development*
  • Plasmodium falciparum / immunology*
  • Seroepidemiologic Studies
  • Young Adult

Substances

  • Antibodies, Protozoan