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Stabilization of a soluble, native-like trimeric form of an efficiently cleaved Indian HIV-1 clade C envelope glycoprotein.

Stabilization of a soluble, native-like trimeric form of an efficiently cleaved Indian HIV-1 clade C envelope glycoprotein.
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Ahmed S, Shrivastava T, Kumar N, Ozorowski G, Ward AB, Chakrabarti BK,


Ahmed S, Shrivastava T, Kumar N, Ozorowski G, Ward AB, Chakrabarti BK, (click to view)

Ahmed S, Shrivastava T, Kumar N, Ozorowski G, Ward AB, Chakrabarti BK,

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The Journal of biological chemistry 2017 03 10() pii 10.1074/jbc.M117.776419

Abstract

Designing an effective HIV-1 envelope glycoprotein (Env) immunogen for elicitation of broadly neutralizing antibodies (bNAbs) is a challenging task owing to the high sequence diversity, heavy glycosylation and inherent meta-stability of Env. Based on the antigenic profile of recently isolated bNAbs, the rational approach to immunogen design is to make a stable version of the Env trimer, which mimics the native trimeric Env present on the viral surface. The SOSIP.664 form of a clade A Env, BG505, yields a homogeneous and well-ordered pre-fusion trimeric form, which maintains structural integrity and desired antigenicity. Following the same approach, we attempted to stabilize a naturally occurring efficiently cleaved clade C Env, namely 4-2.J41, isolated from an Indian patient. Though the SOSIP form of 4-2.J41 failed to produce reasonably well-ordered trimers, the 4-2.J41.SOSIP.664 Env could be stabilized in a native-like trimeric form by swapping a domain from BG505 Env to 4-2.J41 Env. Using various biochemical and biophysical means we confirmed that this engineered Env is cleaved, trimeric and it retains its native-like quaternary conformation exposing mostly broadly neutralizing epitopes. Moreover, introduction of a disulfide bond in the bridging sheet region further stabilized the closed conformation of the Env. Thus, our 4-2.J41.SOSIP.664 Env adds to the increasing pool of potential immunogens for a HIV-1 vaccine, particularly for clade C, which is the most prevalent in India and many other countries. Besides, the approach used to stabilize 4-2.J41 Env may be used successfully with Envs from other HIV-1 strains as well. Additionally, a soluble native trimeric form of an efficiently cleaved membrane bound Env; 4-2.J41 may be beneficial for immunization studies using various prime-boost strategies.

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