1. department < clinical chemistry, microbiology and immunology >
office < CEVAC >
A monoclonal antibody-based immunoassay to measure the antibody response against the repeat region of the circumsporozoite protein of Plasmodium falciparum
Kristina Radin,

2. Malaria disease One of the deadliest infectious diseases.
3 billions of people at risk of infection every day.
Caused by parasitic protozoans from the genus Plasmodium (P. falciparum, P. vivax,
P. malariae, P. ovale, P. knowlesi)
EA Winzeler, Nature. 2008;455: doi: /nature07361

3. Malaria vaccine
RTS,S/AS01 (Mosquirix, GSK Vaccines); first and only licensed malaria vaccine.
Based on sporozoite surface protein - circumsporozoite protein (CSP): 19 NANP amino acid repeat units followed by the complete C-terminal domain without the GPI anchor fused to the hepatitis B surface antigen (HBsAg).
PD Crompton, J Clin Invest. 2010;120(12): doi: /JCI44423.

4. IMMUNE RESPONSES
High IgG concentrations against the NANP repeat region.
Moderate to high CD4+ Th1 responses against flanking region peptides.
No clear correlate of protection.
Monoclonal antibodies (MAL1C, MAL2A and MAL3B) derived from an RTS,S/AS01 vaccine recipient, directed against the NANP repeat region of CSP are able to convey sterile protection against P. falciparum infection when administered to immunodeficient mice with humanized liver.
Anti-CSP antibody levels in the serum of RTS,S vaccine recipients do not always strongly correlate with protection from infection.
Does the concentration of MAL1C-like antibodies in polyclonal sera from RTS,S/AS01 vaccine recipients correlate with protection?

5. DEVELOPMENT
MAL1C-like antibodies in vaccine-induced sera compete with biotinylated monoclonal antibody MAL1C for binding sites on the capture antigen.

6. PROOF of concept
Antibody concentrations (anti-CSP) were measured in 276 serum samples from 92 RTS,S/AS01 vaccine recipients (from 2 RTS,S clinical trials) with validated R32LR ELISA and MAL1C inhibition ELISA.

7. Correlation of MAL1C inhibition and R32LR ELISA titers with protection against infection.

8. conclusion
MAL1C competition ELISA is reliable and robust. Antibody contents measured with MAL1C inhibition ELISA and validated R32LR ELISA correlate very well. The MAL1C inhibition correlates with protection in one of the RTS,S/AS01 vaccine studies, but not in the other. MAL1C inhibition ELISA can be used to detect IgG in sera from other species (rabbit, mouse).