Transmission-reducing immunity is inversely related to age in Plasmodium falciparum gametocyte carriers

Parasite Immunol. 2006 May;28(5):185-90. doi: 10.1111/j.1365-3024.2005.00818.x.


Immunity to the sexual stages of Plasmodium falciparum is induced during natural infections and can significantly reduce the transmission of parasites to mosquitoes (transmission reducing activity; TRA) but little is known about how these responses develop with increasing age/exposure to malaria. Routinely TRA is measured in the standard membrane feeding assay (SMFA). Sera were collected from a total of 199 gametocyte carriers (median age 4 years, quartiles 2 and 9 years) near Ifakara, Tanzania; 128 samples were tested in the SMFA and generated TRA data classified as a reduction of > 50% and > 90% of transmission. TRA of > 50% was highest in young children (aged 1-2) with a significant decline with age (chi(2) trend = 5.79, P = 0.016) and in logistic regression was associated with prevalence of antibodies to both Pfs230 and Pfs48/45 (OR 4.03, P = 0.011 and OR 2.43 P = 0.059, respectively). A TRA of > 90% reduction in transmission was not age related but was associated with antibodies to Pfs48/45 (OR 2.36, P = 0.055). Our data confirm that antibodies are an important component of naturally induced TRA. However, whilst a similar but small proportion of individuals at all ages have TRA > 90%, the gradual deterioration of TRA > 50% with age suggests decreased antibody concentration or affinity. This may be due to decreased exposure to gametocytes, probably as a result of increased asexual and/or gametocyte specific immunity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Age Factors
  • Animals
  • Anopheles / parasitology
  • Antibodies, Protozoan / blood
  • Carrier State / immunology
  • Carrier State / parasitology*
  • Carrier State / transmission
  • Child
  • Child, Preschool
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Humans
  • Infant
  • Linear Models
  • Malaria, Falciparum / blood
  • Malaria, Falciparum / immunology*
  • Malaria, Falciparum / parasitology
  • Malaria, Falciparum / transmission*
  • Male
  • Plasmodium falciparum / growth & development
  • Plasmodium falciparum / immunology*


  • Antibodies, Protozoan