Well-Ordered Trimeric HIV-1 Subtype B and C Soluble Spike Mimetics Generated by Negative Selection Display Native-like Properties

The structure of bg505 gp140 sosip,a soluble mimic of the native hiv-1 envelope glycoprotein (env),marks the beginning of new era in env structure-based immunogen design. displaying a well-ordered quaternary structure,these subtype a-derived trimers display an excellent antigenic profile,discriminating recognition by broadly neutralizing antibodies (bnabs) from non-broadly neutralizing antibodies (non-bnabs),and provide a solid env-based immunogenic platform starting point. even with this important advance,obtaining homogeneous well-ordered soluble sosip trimers derived from other subtypes remains challenging. here,we report the “rescue” of homogeneous well-ordered subtype b and c sosip trimers from a heterogeneous env mixture using cd4 binding site-directed (cd4bs) non-bnabs in a negative-selection purification process. these non-bnabs recognize the primary receptor cd4bs only on disordered trimers but not on the native env spike or well-ordered soluble trimers due to steric hindrance. following negative selection to remove disordered oligomers,we demonstrated recovery of well-ordered,homogeneous trimers by electron microscopy (em). we obtained 3d em reconstructions of unliganded trimers,as well as in complex with scd4,a panel of cd4bs-directed bnabs,and the cleavage-dependent,trimer-specific bnab,pgt151. using bio-layer light interferometry (bli) we demonstrated that the well-ordered trimers were efficiently recognized by bnabs and poorly recognized by non-bnabs,representing soluble mimics of the native viral spike. biophysical characterization was consistent with the thermostability of a homogeneous species that could be further stabilized by specific bnabs. this study revealed that env trimers generate different frequencies of well-ordered versus disordered aberrant trimers even when they are genetically identical. by negatively selecting the native-like well-ordered trimers,we establish a new means to obtain soluble env mimetics derived from subtypes b and c for expanded use as candidate vaccine immunogens. © 2015 guenaga et al.