Detection of antigen-specific B cells to Plasmodium falciparum apical membrane antigen-1 and circumsporozoite protein in humans and immunized mice (P3025)

Abstract

Worldwide, there are an estimated 216 million cases of malaria annually and of those affected 655,000 will succumb to the disease. Antibody responses to infection have been shown to be critical in limiting infection and disease, but the mechanisms by which these are acquired or lost are poorly understood. Various hypotheses have been proposed for dysfunctional humoral responses including B cell exhaustion, germinal center architectural disruption, parasite antigenic variation and inhibitory innate immune signaling. However, the relative infrequency of malaria specific B cells in the periphery has limited targeted detection of these cells. We present a strategy for phenotypic analyses of malaria specific B cells in peripheral blood using tetramerized biotinylated malaria antigen coupled to phycoerythrin labeled streptavidin, magnetic bead enrichment and cytometric flow analysis. Using this technique, we demonstrate the detection of an antigen specific germinal center reaction in B6 mice after immunization with P.pastoris expressing recombinant Plasmodium falciparum apical membrane antigen-1 and circumsporozoite protein. Preliminary results in humans identified low frequency B cells specific to these two antigens. Overall, our results suggest that this technique will be a valuable tool in studying naturally acquired and vaccine derived malaria specific B cell responses.