Membrane proteins of placental parasites
EMSL Project ID
8211
Abstract
Plasmodium falciparum parasites differ from other malaria parasite species that infect human by its ability to sequester in deep vascular beds and adhere to molecules expressed on the endothelium. It is believed that sequestration is the parasite?s mechanism to avoid passage through the spleen where specific and non-specific immune responses can eliminate them. Parasite adhesion to the endothelium is associated with severe clinical syndromes such as cerebral malaria. By adulthood residence of malaria endemic area develop adaptive immunity that protects from clinical disease. However, pregnant women, especially during their first pregnancy are much more susceptible to malaria infection than their non-pregnant counterpart. During pregnancy, the parasites sequester in the placenta. Maternal malaria is characterized by the accumulation of parasites and immune cells in the placenta that lead to poor pregnancy outcome. In a study we conducted several years ago we described that the parasites that infect the placenta have a unique binding phenotype. These parasites bind to the molecule chondroitin sulfate A (CSA) that expressed on the surface of the placenta, a binding phenotype which was not found in parasites from non-pregnant individuals. Later we demonstrated that over successive pregnancies women develop specific immunity to placental parasites, such that immune women have antibodies that inhibit parasite adhesion, unlike women during first pregnancy and males that do not have anti-adhesion antibodies. The major outcomes of placental malaria are maternal anemia and low birthweight (LBW) babies which is one of the causes for mortality during the first year of life. We demonstrated that the birthweight of babies born to mothers that had anti-adhesion antibodies was 500 gr higher than that of babies born to mother with no specific immunity. Thus developing a vaccine that will protect pregnant women will have a major health impact for both mother and infants. Plasmodium falciparum parasites mediate adhesion to the endothelium by expressing parasite?s ligands on the surface of the infected-red blood cells. Therefore these molecules are prime target for developing a vaccine.
In an effort to identify vaccine targets we conducted proteomics studies. For these studies we used samples enriched for membrane proteins. The complex protein mix were digested with trypsin and fractionated on SCX or protein samples were separated on 1D PAGE followed by in-gel trypsin digestion. So far these experiments yielded a list of proteins that were detected only in parasites that bound to CSA but not in parasites that did not have this binding phenotype. The major problem is that the number of peptides corresponding to each of these protein is low, thus the confidence level whether these proteins are actually unique to CSA-binding parasites is low. One of the difficulties is that the membrane proteins are expressed at low levels and the amount of material available to do these studies is limited. Therefore more sensitive technology is required. Using the FTICR to analyze these samples may validate the MS/MS results obtained using nanospray technology and may allow to identify additional proteins that are expressed at low levels.
Project Details
Project type
Exploratory Research
Start Date
2004-05-31
End Date
2007-06-03
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
Dang X, J Scotcher, S Wu, RK Chu, N Tolic, I Ntai, P Thomas, RT Fellers , BP Early, Y Zheng, KR Durbin, RD LeDuc, JJ Wolff, CJ Thompson, J Pan, J Han, JB Shaw, JP Salisbury, M Easterling, CH Borchers, JS Brodbelt, J Agar, L Pasa-Tolic, N Kelleher, and NL Young. 2014. "The first pilot project of the consortium for top-down proteomics: A status report." Proteomics 14(10):1130-1140. doi:10.1002/pmic.201300438
Pasa-Tolic L, and C Masselon. 2014. "Shining a spotlight on intact proteins." Proteomics 14:1125. doi:10.1002/pmic.201470073