PAMCPH

Recombinant var2CSA protein as vaccine candidate for placental malaria

Background

In 2003, var2CSA was identified at Centre for Medical Parasitology (CMP), University of Copenhagen (UCPH) as the parasite protein responsible for the binding of infected erythrocytes to CSA in the placenta1.  Only women who have had placental malaria have antibodies against the var2CSA protein give birth to healthier babies in comparison to women infected for the first time by placental malaria during their pregnancy.  Since the interaction between var2CSA and CSA is a key element in the pathogenesis of Pregnancy Associated Malaria (PAM,) a vaccine against PAM should induce antibodies that block the binding of var2CSA to CSA

The existence of a reliable in vitro assay for the evaluation of the vaccine efficacy has now enabled researchers to define specific parts of var2CSA that can be used in an adhesion-blocking vaccine (reviewed in 3).  Var2CSA is a complex 350kDa protein with seven large domains.  Through different -funding schemes, Ali Salanti’s group has produced more than 200 different recombinant var2CSA antigens in different expression systems and assessed the capacity of Immunoglobulin G (IgG) induced by immunisation of animals to inhibit parasite binding to CSA.  They have identified two subunits of the var2CSA protein (Duffy Binding-Like (DBL) 4 and DBL1-2) that induce highly inhibitory and cross-inhibitory IgGs.  These subunits have already been successfully produced in small scale and at high yields in S2 cells at ExpreS2ion Biotechnologies.

Objectives

The overall objective of the project is to enable the manufacture of a vaccine which protects foetus and mother against the adverse effects of malaria during pregnancy.  Within this project the success criterion is to define the optimal antigen and adjuvant formulation, show that it can be produced in a scalable manner and that it proves safe to use in animals.  The overall aim of this project is to support the production of a recombinant var2CSA fragment based vaccine under cGMP that can be used in the clinical trials supported by the PlacMalVac project (European Commission Framework Program 7 funded project started in 2013).

Major Milestones

  • Research Cell Banks of 2-3 clones generated and tested (Q3 2013)
  • GMP process development transferred to Contract Manufacturing Organisation (Q2 2014)
  • Drug Substance cGMP batch release (Q4 2014)
  • Drug Product cGMP batch release (Q1 2015)
  • Toxicology studies final report (Q2 2015)
  • Investigational Medicinal Product Dossier (Q3 2015)

Achievements

  • The Research Cell Bank was made in October 2013 and the stability of the selected clone tested.
  • Formulation studies were performed in October 2013 at UCPH to try to optimise the stability of the protein with different buffers/stabilisers.
  • Inhibition of parasite binding with polyclonal antibodies from rats and mice immunised with non-His tagged protein adjuvanted with Aluminium hydroxide was achieved.
  • Immunisation studies were performed in December 2013 in mice, with different antigen-adjuvant combinations.  Strong immunological responses were observed including some level of cross-inhibitory antibodies.

References

  1. Khunrae P, Dahlback M, Nielsen MA, Andersen G, Ditlev SB, Resende M et al. Full-length recombinant Plasmodium falciparum var2CSA binds specifically to CSPG and induces potent parasite adhesion-blocking antibodies. J Mol Biol. 2010 Apr;397:826-834.
  2. Dahlback M, Joergensen LM, Nielsen MA, Clausen TM, Ditlev SB, Resende M et al. The chondroitin sulphate A-binding site of the var2CSA protein involves multiple N-terminal domains. J Biol Chem. 2011 May;286(18):15908-17.
  3. Clausen TM, Christoffersen S, Dahlback M, Langkilde AE, Jensen KE, Resende M et al. Structural and Functional Insight into How the Plasmodium falciparum var2CSA Protein Mediates Binding to Chondroitin Sulfate A in Placental Malaria. J Biol Chem. 2012 Jul;287(28):23332-23345.

 

Publications

Malar J (2016) 15:476 DOI 10.1186/s12936-016-1527-8
PLoS ONE 10(9): e0135406. doi: 10.1371/journal.pone.0135406