Poster Presentation 10th Australian Peptide Conference 2013

APR-1 and ASP-2 protein-based subunit peptide based vaccine against hookworm parasite (#130)

Abdullah AH Ahmad Fuaad 1 , Guangzho Zhao 1 , Ben Cristofori-Armstrong 1 , Mariusz Skwarczynski 1 , Istvan Toth 1 2
  1. School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, QLD, Australia
  2. Pharmacy Australia Centre of Excellence, University of Queensland, St Lucia, QLD, Australia

Hookworm is a blood feeding helminthes that infects more than 700 million people worldwide, predominantly in regions with low socioeconomic conditions.1  Hookworm moulds into 5 different stages in its life cycle. The different stages resulted in difficulties in selection of specific vaccine target against the parasite due its biological reformations. Thus, it is preferably to develop a vaccine that can target at least two of the five hookworm stages to combat the hematophagous parasite.

Two critical hookworm enzymes were found to be essential in feeding and growth. Hookworm larvae (L3) utilizes aspartic enzyme (ASP-2) during its growth into adult hookworm while adult hookworm exploits aspartic enzyme (APR-1) for haemoglobin digestion during feeding (Figure 1). Vaccine candidates based on these two proteins resulted in reduced faecal egg counts2,3 ; however, APR-1 autodegrades rapidly3  while ASP-2 vaccine trial to individuals previously infected by hookworm resulted in immediate-type hypersensitivity.4  To overcome these problems, subunit peptide based vaccine approach utilizing minimal peptide sequences from the proteins, showed promising results.5 

With the aim to conserve the subunit peptides’ secondary structure, a series of subunit peptides vaccines based on APR-1 and ASP2 were designed. To enhance the antigen’s efficacy, peptide sequence modifications and conjugations to lipid core peptide (LCP) delivery system were performed. The peptide series were designed using Peptide Secondary Structure Prediction tools and homology test were performed using UniProt Blast software. LCPs and peptide epitopes were synthesized via solid phase peptide synthesis (SPPS). Products were analysed using transmission electron microscopy (TEM), dynamic light scattering (DLS), and circular dichroism (CD). We demonstrated that these vaccine candidates were able to self-assemble to form particles. The peptides were also verified to have the desired conformation upon conjugation to the LCP system.

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  1. Hotez, P. J., Bethony, J. M., Diemert, D. J., Pearson, M. & Loukas, A. Developing vaccines to combat hookworm infection and intestinal schistosomiasis. Nature reviews. Microbiology 8, 814-826 (2010).
  2. Loukas, A. et al. Vaccination with recombinant aspartic hemoglobinase reduces parasite load and blood loss after hookworm infection in dogs. PLoS medicine 2, e295 (2005).
  3. Pearson, M. S. et al. An enzymatically inactivated hemoglobinase from Necator americanus induces neutralizing antibodies against multiple hookworm species and protects dogs against heterologous hookworm infection. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 23, 3007-3019 (2009).
  4. Diemert, D. J. et al. Generalized urticaria induced by the Na-ASP-2 hookworm vaccine: implications for the development of vaccines against helminths. The Journal of allergy and clinical immunology 130, 169-176 e166 (2012).
  5. Skwarczynski, M. et al. Peptide-based subunit vaccine against hookworm infection. PloS one 7, e46870 (2012).