Probing The Role Of Hiv Antigen Nanoscale Organization On B-Cell Activation With Dna Origami

HIV germline-targeting antigens are promising immunogens in development for HIV vaccines, which have the goal of priming progenitor B-cells capable of evolving toward the production of broadly neutralizing antibodies (bNAbs). Amongst these antigens, eOD-GT8 engineered from the envelope glycoprotein gp120 has been previously reported to be highly immunogenic only when presented in a multimeric form. B-cell activation is initiated upon engagement of cell membrane expressed B-cell receptors (BCR) by antigens. Although the intracellular signaling cascade following antigen binding is well understood, very little is known about the early events of recognition and binding of antigens by the BCR. In particular, the importance of antigen nanoscale organization and valency remain not well understood even though these parameters may be critical for the development of a successful vaccine. Here, to gain more insight into the molecular mechanisms leading to B-cell activation, we use scaffolded DNA origami nanoparticles to test various models of BCR-mediated activation. DNA nanoparticles offer the unique opportunity to organize HIV antigens in a precise nanoscale organization and with control of valency. We used a combination of cytoplasmic calcium influx assay and fluorescence imaging to monitor antigen binding and subsequent B cell activation for multi-dimensional presentation of the eOD-GT8 immunogen. Thus, we determined that an inter-antigen distance greater than 28 nm and a copy-number of eOD-GT8 above 5 per nanoparticles is sufficient to trigger maximal B-cell activation. Taken together, our results demonstrate the usefulness of DNA origami nanoparticles to probe the role of nanoscale viral antigen presentation on immune cell activation. Moreover, this study opens the way to the development of new vaccines for HIV and other infectious diseases.