Poster Presentation 50th Lorne Proteins Conference 2025

Structural insights into MSP2 and AMA1, two structurally diverse merozoite vaccine candidatesĀ  of Plasmodium falciparum (#405)

Mick Foley 1 2 , Dimuthu Angage 2 , Robin F Anders 2 , Jill Chmielewski 3 4 , Janesha Maddumage 2 , Eva Hesping 4 5 , Sabrina Caiazzo 4 5 , Keng Heng Lai 3 , Lee Ming Yeoh 6 7 , D. Herbert Opi 6 7 , Nicki Badii 2 , Ray Norton 8 , James Beeson 6 9 10 , Marc Kvansakul 2 , Arti Medhavy 11 , Michael Good 11 , Danielle Stanisic 11 , Justin Boddey 4 5 , Danny Wilson 3 6 12
  1. AdAlta, Bundoora, Victoria, Australia
  2. Department of Biochemistry and Chemistry, La Trobe University, Bundoora, VIC, Australia
  3. Research Centre for Infectious Diseases, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia , Australia
  4. Infectious Diseases & Immune Defense Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
  5. Department of Medical Biology, The University of Mebourne, Parkville, Victoria, Australia
  6. Burnet Institute, Melbourne, Victoria, Australia
  7. Department of Medicine, The University of Melborune, Parkville, Victoria, Australia
  8. Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
  9. Central Clinical School and Department of Microbiology, Monash University, Clayton, Victoria, Australia
  10. Department of Infectious Diseases, The University of Melbourne, Parkville, Victoria, Australia
  11. Institute for Biomedicine and Glycomics, Griffith University, Gold Coast, Queensland, Australia
  12. Institute for Photonics and Advanced Sensing (IPAS), The University of Adelaide, Adelaide, South Australia , Australia

Apical membrane antigen-1 (AMA1) and merozoite surface protein 2 (MSP2) are key malaria vaccine candidates, with AMA1 playing a critical role in host cell invasion by Plasmodium parasites. However, extensive polymorphisms in both proteins present challenges for their use as vaccine targets. Unlike AMA1, which is well-structured MSP2 is predominantly disordered, further complicating its use in a vaccine. We used phage display to screen an i-body library for binders to AMA1 and MSP2 from various P. falciparum strains. This led to the identification of 12 AMA1-specific i-bodies, including WD34, which binds with low nanomolar affinity to a conserved epitope in multiple Plasmodium species. WD34 inhibited binding of the AMA1 ligand RON2, and reduced growth of erythrocytic and pre-erythrocytic parasites. X-ray crystallography revealed that WD34 binds to the conserved hydrophobic groove of AMA1, with binding sites consistent across apicomplexan parasites. The inhibition of P. falciparum, P. knowlesi, and transgenic P. falciparum expressing P.vivax AMA1, along with its suppression of P. yoelii infection in mice, highlights the therapeutic potential of WD34.

In contrast, no MSP2 binders were isolated, likely due to its disordered structure. AlphaFold2 confirmed NMR data that 3D7 and FC27 are disordered, however other variants are predicted to contain Ī²-solenoid folds. Developing stable recombinant structures for these variants may enable the selection of MSP2-targeting i-bodies and further our understanding of the function of MSP2. This study underscores the utility of phage display for structured antigens like AMA1, while indicating the need for innovative approaches for disordered antigens such as MSP2.