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Functional analysis of Plasmodium falciparum apical membrane antigen 1 utilizing interspecies domains
Julie Healer1, Tony Triglia, Anthony N Hodder
1Walter and Eliza Hall Institute, Melbourne, Australia.
Abstract:
Plasmodium falciparum apical membrane antigen 1 (AMA1) is a leading malaria vaccine candidate whose function has not been unequivocally defined. Partial complementation of function can be achieved by exchanging the AMA1 of P. falciparum (PfAMA1) with that of P. chabaudi (PcAMA1). In this study, parasites expressing chimeric AMA1 proteins were created to identify domains of PfAMA1 critical in erythrocyte invasion and which are important immune targets. We report that specific chimeric AMA1 proteins containing domains I to III from PfAMA1 and PcAMA1 were able to complement PfAMA1 function in erythrocyte invasion. We demonstrate that domain III does not contain dominant epitope targets of antibodies raised against Escherichia coli expressed and refolded PfAMA1 ectodomain. Furthermore, we generated a parasite line in which the N-terminal pro region of PfAMA1 does not undergo proteolytic cleavage and show that its removal is necessary for PfAMA1 function.
Insights
Investigating Plasmodium falciparum apical membrane antigen 1 (AMA1) function in malaria parasite invasion revealed key domains for erythrocyte invasion and identified that proteolytic cleavage of AMA1 is essential for its function.
Area of Science:
- Malariology
- Immunology
- Molecular Parasitology
Background:
- Plasmodium falciparum apical membrane antigen 1 (PfAMA1) is a crucial malaria vaccine candidate.
- Its precise function in erythrocyte invasion remains incompletely understood.
- Chimeric AMA1 proteins offer a method to dissect PfAMA1 functional domains.
Purpose of the Study:
- To identify domains of PfAMA1 critical for erythrocyte invasion.
- To determine immune targets within PfAMA1 domains.
- To investigate the role of N-terminal pro region processing in PfAMA1 function.
Main Methods:
- Generation of Plasmodium parasites expressing chimeric AMA1 proteins.
- Functional complementation assays to assess erythrocyte invasion.
- Epitope mapping of PfAMA1 ectodomain using antibodies.
Main Results:
- Specific chimeric AMA1 proteins (domains I-III) from P. falciparum and P. chabaudi complemented PfAMA1 function.
- Domain III of PfAMA1 does not harbor dominant antibody epitopes from recombinant ectodomain.
- A parasite line with uncleaved N-terminal pro region showed impaired PfAMA1 function, indicating cleavage is necessary.
Conclusions:
- PfAMA1 domains I-III are important for erythrocyte invasion, with potential for cross-species complementation.
- Domain III is not a primary target for antibodies against the recombinant ectodomain.
- Proteolytic processing of the PfAMA1 N-terminal pro region is essential for its function during malaria parasite invasion.
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