The αTSR Domain of Plasmodium Circumsporozoite Protein Bound Heparan Sulfates and Elicited High Titers of Sporozoite Binding Antibody After Displayed by Nanoparticles

Abstract

Ming Xia,1 Frank Vago,2 Ling Han,3 Pengwei Huang,1 Linh Nguyen,3 Geert-Jan Boons,4– 6 John S Klassen,3 Wen Jiang,2 Ming Tan1,7 1Division of Infectious Diseases, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, USA; 2Department of Biological Sciences, Purdue University, West Lafayette, IN, USA; 3Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada; 4Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA; 5Department of Chemistry, University of Georgia, Athens, GA, USA; 6Department of Chemical Biology and Drug Discovery, Utrecht Institute for Pharmaceutical Sciences, and Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, the Netherlands; 7Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USACorrespondence: Ming Tan, Division of Infectious Diseases, Cincinnati Children’s Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229-3039, USA, Tel [phone], Fax [phone], Email [email protected]: Malaria is a devastating infectious illness caused by protozoan Plasmodium parasites. The circumsporozoite protein (CSP) on Plasmodium sporozoites binds heparan sulfate proteoglycan (HSPG) receptors for liver invasion, a critical step for prophylactic and therapeutic interventions.Methods: In this study, we characterized the αTSR domain that covers region III and the thrombospondin type-I repeat (TSR) of the CSP using various biochemical, glycobiological, bioengineering, and immunological approaches.Results: We found for the first time that the αTSR bound heparan sulfate (HS) glycans through support by a fused protein, indicating that the αTSR is a key functional domain and thus a vaccine target. When the αTSR was fused to the S domain of norovirus VP1, the fusion protein self-assembled into uniform S60-αTSR nanoparticles. Three-dimensional structure reconstruction revealed that each nanoparticle consists of an S60 nanoparticle core and 60 surface displayed αTSR antigens. The nanoparticle displayed αTSRs retained the binding function to HS glycans, indicating that they maintained authentic conformations. Both tagged and tag-free S60-αTSR nanoparticles were produced via the Escherichia coli system at high yield by scalable approaches. They are highly immunogenic in mice, eliciting high titers of αTSR-specific antibody that bound specifically to the CSPs of Plasmodium falciparum sporozoites at high titer.Discussion and Conclusion: Our data demonstrated that the αTSR is an important functional domain of the CSP. The S60-αTSR nanoparticle displaying multiple αTSR antigens is a promising vaccine candidate potentially against attachment and infection of Plasmodium parasites.Keywords: malaria, Plasmodium, αTSR domain, receptor binding domain, S60 nanoparticle, malaria vaccine, norovirus

Keywords

• malaria
• plasmodium
• αtsr domain
• receptor binding domain
• s60 nanoparticle
• malaria vaccine
• norovirus