Thermostability of Well-Ordered HIV Spikes Correlates with the Elicitation of Autologous Tier 2 Neutralizing Antibodies.

Yu Feng,Natalia De Val,Richard Wilson,Shridhar Bale,Javier Guenaga,Heather Arendt,Joanne Destefano,Andrew B Ward,Karen Tran,Richard T Wyatt,Shailendra Kumar,Alexandra Trkola

doi:10.1371/journal.ppat.1005767

Yu Feng, Natalia De Val + Show 10 more

Open Access

https://doi.org/10.1371/journal.ppat.1005767

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Abstract

In the context of HIV vaccine design and development, HIV-1 spike mimetics displaying a range of stabilities were evaluated to determine whether more stable, well-ordered trimers would more efficiently elicit neutralizing antibodies. To begin, in vitro analysis of trimers derived from the cysteine-stabilized SOSIP platform or the uncleaved, covalently linked NFL platform were evaluated. These native-like trimers, derived from HIV subtypes A, B, and C, displayed a range of thermostabilities, and were “stress-tested” at varying temperatures as a prelude to in vivo immunogenicity. Analysis was performed both in the absence and in the presence of two different adjuvants. Since partial trimer degradation was detected at 37°C before or after formulation with adjuvant, we sought to remedy such an undesirable outcome. Cross-linking (fixing) of the well-ordered trimers with glutaraldehyde increased overall thermostability, maintenance of well-ordered trimer integrity without or with adjuvant, and increased resistance to solid phase-associated trimer unfolding. Immunization of unfixed and fixed well-ordered trimers into animals revealed that the elicited tier 2 autologous neutralizing activity correlated with overall trimer thermostability, or melting temperature (Tm). Glutaraldehyde fixation also led to higher tier 2 autologous neutralization titers. These results link retention of trimer quaternary packing with elicitation of tier 2 autologous neutralizing activity, providing important insights for HIV-1 vaccine design.

Highlights

Quaternary packing of the heavily glycosylated HIV-1 envelope glycoprotein (Env) functional spike presents formidable obstacles for the elicitation of neutralizing antibodies to this viral surface unit
As the sole determinant exposed on the viral surface to the host B cells, development of native-like HIV-1 envelope glycoprotein (Env) functional spikes has been a major initial
An alternative approach to virus like particles (VLPs) is to generate well-ordered, soluble spike mimetics such as the recently described SOSIP or NFL trimers. These trimers consist of three protomers containing the gp120 binding domain covalently coupled to the gp41 ectodomain by two different strategies, which results in the generation of soluble, “native-like” HIV-1 spike mimetics [4,5,6,7,8,9]

Summary

Introduction

Quaternary packing of the heavily glycosylated HIV-1 envelope glycoprotein (Env) functional spike presents formidable obstacles for the elicitation of neutralizing antibodies to this viral surface unit These obstacles, which have been defined over the past 20 years, include conserved epitope occlusion at the receptor CD4 binding site (CD4bs), receptor-induced formation of co-receptor binding sites, adaptable and extensive glycan shielding, spike subunit dissociation, and the umbrella shape of the trimer itself that restricts B-cell receptor access to underside regions of the spike [1,2,3,4]. An alternative approach to VLPs is to generate well-ordered, soluble spike mimetics such as the recently described SOSIP or NFL trimers These trimers consist of three protomers containing the gp120 binding domain covalently coupled to the gp ectodomain by two different strategies, which results in the generation of soluble, “native-like” HIV-1 spike mimetics [4,5,6,7,8,9]. Several studies have explored the use of cross-linking reagents to stabilize soluble Env [11, 12] and membrane-expressed Env trimers [13, 14]

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