Parasitology



Evaluation of the standard membrane feeding assay (SMFA) for the determination of malaria transmission-reducing activity using empirical data


M. VAN DER KOLK a1a2a3c1, S. J. DE VLAS a4, A. SAUL a5, M. VAN DE VEGTE-BOLMER a1, W. M. ELING a1 and W. SAUERWEIN a1
a1 UMC Nijmegen, Medical Microbiology, PB 9101, 6500 HB Nijmegen, The Netherlands
a2 Institut de Recherche pour le Développement, rue La Fayette 75480 Paris cedex 10, Paris, France
a3 Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), Laboratoire de Recherche sur le Paludisme, BP 288, Yaoundé, Cameroun
a4 Erasmus MC University Medical Center Rotterdam, Department of Public Health, PB 1738, 3000 DR Rotterdam, The Netherlands
a5 Malaria Vaccine Development Unit, NIAID/LPD, NIH, Rockville, MD, USA

Article author query
van der kolk m   [PubMed][Google Scholar] 
de vlas sj   [PubMed][Google Scholar] 
saul a   [PubMed][Google Scholar] 
van de vegte-bolmer m   [PubMed][Google Scholar] 
eling wm   [PubMed][Google Scholar] 
sauerwein w   [PubMed][Google Scholar] 

Abstract

Host responses to the transmittable stages of the malaria parasite may reduce transmission effectively. Transmission-reducing activity (TRA) of human serum can be determined as a percentage, using the Standard Membrane Feeding Assay (SMFA). This laboratory assay was evaluated using the results of 121 experiments with malaria-endemic sera among which many repeated measurements were obtained. The assay consists of the feeding of Anopheles stephensi mosquitoes with cultured Plasmodium falciparum gametocytes, mixed with human red blood cells, and control and experimental sera. The TRA of individual sera was determined by the comparison of oocyst densities between these sera. Bootstrap data on oocyst densities in individual mosquitoes in control feeds were used to construct confidence limits for TRA percentages of serum feeds. Low (<20%) and high TRA (>90%) values for individual sera were usually reproduced in a second experiment, whereas this was more difficult for values between 20% and 90%. The observed variability of TRA values is explained in part by the variability in oocyst density per mosquito. Oocyst densities in control feeds varied more between experiments than within experiments and showed a slight decline over the 3 years of experiments. Reproducibility of TRA of field sera was low (20%) between experiments, but much higher (61%) within experiments. A minimum of 35 oocysts per mosquito in control feeds gave optimal reproducibility (44%) between experiments. We recommend that (1) sera are compared within an experiment, or (2) assays are only analysed where controls have at least 35 oocysts per mosquito. The SMFA is under the recommended conditions appropriate for the study of factors that may influence TRA, e.g. transmission blocking vaccines.

(Received March 12 2004)
(Revised May 25 2004)
(Accepted May 26 2004)


Key Words: malaria; transmission-blocking activity; membrane feeding; Plasmodium falciparum; Anopheles stephensi; transmission-blocking vaccine.

Correspondence:
c1 UMC Nijmegen, Medical Microbiology, PB 9101, 6500 HB Nijmegen, The Netherlands. Tel: +00 31 24 3619515. E-mail: m.vanderkolk@ncmls.kun.nl; mikevanderkolk@tele2.nl


Metrics