Characterization of full-length and cytoplasmic tail-truncated envelope glycoproteins incorporated into human immunodeficiency virus (HIV-1) virions and virus-like particles.

During transport to the surface of infected cells, the human immunodeficiency virus (HIV-1) envelope glycoprotein (Env) trimer is cleaved to produce the mature functional Env trimer [(gp120/gp41) IMPORTANCE: The human immunodeficiency virus (HIV-1) envelope glycoprotein (Env) trimer mediates entry of the virus into host cells. The pretriggered conformation (PTC) of Env is the major target for protective broadly neutralizing antibodies, but the PTC is unstable and therefore difficult to study. The cleavage of the flexible Env precursor stabilizes the PTC. Therefore, the presence of uncleaved Env compromises the purity of the PTC in Env preparations. We found that certain truncations of the Env cytoplasmic tail resulted in improved ratios of cleaved:uncleaved Env in preparations of HIV-1 viruses or virus-like particles. In some contexts, cytoplasmic tail truncation increased the level of Env in virus preparations. Although higher concentrations of antibodies were required to neutralize these viruses, Envs with specific truncations of the cytoplasmic tail retained the PTC. Thus, cytoplasmic tail truncation could assist efforts to purify and characterize the Env PTC on the viral membrane.