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Identification of Plasmodium knowlesi erythrocyte binding proteins
L H Miller1, D Hudson, J D Haynes
1Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892.
Abstract:
Plasmodium knowlesi, a malaria of Old World monkeys, invades all Duffy blood group positive human erythrocytes and various New World monkey erythrocytes except Cebus apella. We had previously identified a 135 kDa parasite protein in supernatants of P. knowlesi cultures that bound to Duffy positive but not to Duffy negative human erythrocytes [Haynes et al., J. Exp. Med. 167, 1873-1881 (1988)]. We now use New World monkey erythrocytes as a reagent to identify P. knowlesi proteins in culture supernatants that will bind to all New World monkey erythrocytes susceptible to invasion but not to C. apella erythrocytes, which are refractory to invasion. The 135 kDa protein binds to all New World monkey erythrocytes, including C. appella. Another protein of 155 kDa binds to all New World monkey erythrocytes except C. apella. The 155 kDa protein binds to Old World monkey erythrocytes, the natural host of P. knowlesi; it does not bind to human Duffy positive erythrocytes. This and the previous study are the beginning of the identification of parasite proteins of P. knowlesi that bind to erythrocytes in a receptor specific manner.
Insights
Researchers identified Plasmodium knowlesi proteins binding to monkey and human red blood cells. A 155 kDa protein specifically binds to Old World monkey erythrocytes, distinct from the 135 kDa protein.
Area of Science:
- Malariology
- Parasitology
- Molecular Biology
Background:
- Plasmodium knowlesi, a malaria parasite of Old World monkeys, infects human Duffy blood group positive erythrocytes.
- Previous research identified a 135 kDa P. knowlesi protein binding to Duffy-positive human erythrocytes.
Purpose of the Study:
- To identify P. knowlesi proteins that bind specifically to New World monkey erythrocytes susceptible to invasion.
- To differentiate binding specificities of P. knowlesi erythrocyte-binding proteins.
Main Methods:
- Utilized New World monkey erythrocytes as reagents to screen P. knowlesi culture supernatants.
- Analyzed protein binding to erythrocytes from various monkey species, including Cebus apella (refractory).
- Characterized the binding properties of 135 kDa and 155 kDa P. knowlesi proteins.
Main Results:
- The 135 kDa protein binds to all tested New World monkey erythrocytes, including C. apella.
- A 155 kDa protein binds to all New World monkey erythrocytes except C. apella.
- The 155 kDa protein binds to Old World monkey erythrocytes but not human Duffy-positive erythrocytes.
Conclusions:
- Identified distinct Plasmodium knowlesi erythrocyte-binding proteins with varying specificities.
- The 155 kDa protein shows specific binding to the natural host erythrocytes (Old World monkeys).
- These findings represent initial steps in identifying receptor-specific parasite proteins for P. knowlesi.
