DISCUSSION
As noted above, the HIV Env trimer evades antibody-mediated neutralization by conformational masking, glycan shielding, and sequence variation. Env trimers stabilized in the prefusion-closed conformation, however, induce recognition of the neutralization-susceptible shape of Env, and their use in human vaccine trials such as VRC 018We previously observed in the VRC 018 clinical trialIt will be interesting to see how prefusion-stabilized Env-trimer immunization can be altered to overcome glycan shielding and sequence variation. One way to overcome immunogenicity issues related to glycan shielding might be to mask the exposed protein base on the trimer with 