Enhancing and shaping the immunogenicity of native-like HIV-1 envelope trimers with a two-component protein nanoparticle

Abstract

The development of native-like HIV-1 envelope (Env) trimer antigens has enabled the induction of neutralizing antibody (NAb) responses against neutralization-resistant HIV-1 strains in animal models. However, NAb responses are relatively weak and narrow in specificity. Displaying antigens in a multivalent fashion on nanoparticles (NPs) is an established strategy to increase their immunogenicity. Here we present the design and characterization of two-component protein NPs displaying 20 stabilized SOSIP trimers from various HIV-1 strains. The two-component nature permits the incorporation of exclusively well-folded, native-like Env trimers into NPs that self-assemble in vitro with high efficiency. Immunization studies show that the NPs are particularly efficacious as priming immunogens, improve the quality of the Ab response over a conventional one-component nanoparticle system, and are most effective when SOSIP trimers with an apex-proximate neutralizing epitope are displayed. Their ability to enhance and shape the immunogenicity of SOSIP trimers make these NPs a promising immunogen platform.

Tailored Design of Protein Nanoparticle Scaffolds for Multivalent Presentation of Viral Glycoprotein Antigens

“…Each SAXS-validated trimer (Figure 2a-d) was docked pairwise with a set of previously designed symmetric homo-oligomers 26 to generate tetrahedral, octahedral, and icosahedral arrangements using the TCdock program 16,17 . Icosahedral designs are particularly interesting as vaccine scaffolds as they have the highest valency among the cubic point group symmetries (20 trimers per particle compared to 8 for octahedra and 4 or 8 for tetrahedra), and higher valency has been shown to elicit higher antibody (Ab) titers in immunization studies 18,19,27 . To increase the probability of generating icosahedra, three naturally occurring homopentamers were also included in the docking calculations (PDB IDs 2JFB, 2OBX, and 2B98; sequences in Supplementary Table 7).…”

“…Because previous work involving icosahedral nanoparticle scaffolds displaying HIV-1 Env trimers has shown that antigen crowding can modulate the accessibility of specific epitopes and thereby influence the humoral immune response 19,36 , we characterized the antigenicity of the BG505 SOSIP fusion nanoparticles in more detail.…”

“…The designed nanoparticle scaffolds developed in this work exhibit varying geometries and valencies, providing a novel way to manipulate epitope accessibility. To determine the effect of particle symmetry/geometry on epitope accessibility, we selected the BG505 SOSIP-T33_dn2 nanoparticle as a candidate to compare against a previously published SOSIP-displaying icosahedral nanoparticle (BG505 SOSIP-I53-50) 19 through surface plasmon resonance (SPR) experiments. To first validate mAb binding to the BG505 SOSIP trimer on a structural level when the latter is fused to the trimeric component T33_dn2A, NS-EM class averages and a 3D reconstruction (see Methods) were carried out with the VRC01 Fab, and the previously observed binding mode was confirmed ( Figure 6a).…”

“…These studies collectively highlight several of the key advantages of using self-assembling proteins as scaffolds for multivalent antigen presentation 13,14 , including the formation of stable, highly monodisperse immunogens, the existence of scalable manufacturing methods, and seamless integration of antigen and scaffold via genetic fusion. More recently, computationally designed one- 15 and two- 16,17 component protein nanoparticles have also been used to present complex oligomeric antigens 18,19 . The high stability of designed proteins 20,21 , versatility and ease of production and purification, increased potency observed upon immunization 18,19 , and the ability to predictively explore new structural space make these materials attractive as scaffolds for multivalent antigen presentation.…”

“…More recently, computationally designed one- 15 and two- 16,17 component protein nanoparticles have also been used to present complex oligomeric antigens 18,19 . The high stability of designed proteins 20,21 , versatility and ease of production and purification, increased potency observed upon immunization 18,19 , and the ability to predictively explore new structural space make these materials attractive as scaffolds for multivalent antigen presentation.…”