Field Evaluation of Enzyme-linked Immunosorbent Assays for Plasmodium falciparum and Plasmodium vivax Sporozoites in Mosquitoes (Diptera: Culicidae) from Papua New Guinea1

Abstract

Enzyme-linked immunosorbent assays (ELISA's) were compared with dissection results on mosquitoes of the Anopheles punctulatus Doenitz complex collected in Papua New Guinea. Assays were based on monoclonal antibodies developed against the immunodominant peptide repeat portion of the circumsporozoite (CS) proteins of Plasmodium falciparum (Welch) and Plasmodium vivax (Grassi & Feletti) sporozoites. Excellent correlation was observed between the two methods, with positivity rates of 4.0% for salivarygland midgut infections determined by dissection and 3.4% for the combined ELISA's. These species-specific assays, with a 10-fold increase in sensitivity over previously used ELISA's, gave geometric means of 920 P. falciparum and 460 P. vivax sporozoites per infected mosquito. Use of genetically engineered P. falciparum and synthetic P. vivax CS antigens eliminated the requirement for salivary-gland sporozoites as quantitative positive controls. Approximately 30 pg of recombinant P. falciparum and 60 pg of synthetic P. vivax CS antigen corresponded to 100 salivary-gland sporozoites in the respective ELISA.