|dc.description.abstract||Background: Malaria is a major global cause of deaths and a vaccine is urgently needed.
Results: We have employed the P. falciparum merozoite antigens MSP2-3D7/FC27 and AMA1, used them in ELISA,
and coupled them in different ways using surface plasmon resonance (SPR) and estimated affinity (measured as kd)
of monoclonal as well as naturally-acquired polyclonal antibodies in human plasma. There were major differences in
kd depending on how the antigens were immobilized and where the His-tag was placed. For AMA1 we could see
correlations with invasion inhibition. Using different immobilizations of proteins in SPR, we could see only moderate
correlations with levels of antibodies in ELISA, indicating that in ELISA the proteins were not uniformly bound and
that antibodies with many specificities exist in natural immunisation. The correlations between ELISA and SPR were
enhanced when only parasite positive samples were included, which may indicate that high affinity antibodies are
difficult to maintain over long periods of time. We found higher kd values for MSP2 (indicating lower affinity) compared
to AMA1, which might be partly explained by MSP2 being an intrinsically disordered protein, while AMA1 is globular.
Conclusions: For future vaccine studies and for understanding immunity, it is important to consider how to present
proteins to the immune system to achieve highest antibody affinities.||en_US