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Measuring erythrocyte surface-anchored PfEMP1 levels among progeny from a 3D7 x HB3 Plasmodium falciparum genetic cross

Friday, November 08, 2013 — Poster Session III

10:00 a.m. – 12:00 p.m.

FAES Academic Center (Upper-Level Terrace)




  • A.T. Neal
  • L.C. Ranford-Cartwright
  • C.I. Newbold
  • R.M. Fairhurst


Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is the main parasite virulence factor of P. falciparum. Disrupting the trafficking of PfEMP1 to the infected red blood cell (iRBC) surface is an attractive therapeutic approach, as studies have demonstrated that reduced surface PfEMP1 levels significantly weaken iRBC cytoadherence to host microvasculature, likely lessening disease severity. The culture-adapted parasite line 3D7 is inherently defective in exporting PfEMP1 to the iRBC surface. Hypothesizing that 3D7 harbors one or more genetic determinants of impaired PfEMP1 trafficking, we examined the surface PfEMP1 levels of 17 progeny clones obtained from a genetic cross between 3D7 and the ‘trafficking-competent’ parasite line HB3. This was accomplished using Western blotting and a two-color, triple-layer flow cytometry assay with plasma from malaria-immune Malian adults. We found that 3D7 displays 75% less PfEMP1 relative to HB3. Progeny phenotypes normalized to HB3 range from 37% more to 88% less surface PfEMP1 levels. Using these phenotypes in QTL analysis, we identified significant loci on chromosomes 12 and 14 that each explain 50% of the phenotype variance. The role of candidate genes in the trafficking of PfEMP1 will be confirmed in allele-exchange experiments, where the defect is rescued in 3D7 and introduced in HB3.

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