The invention features stabilized human immunodeficiency virus (HIV) envelope (Env) trimers. In particular, the present invention describes stabilized HIV envelope trimers comprising three modified gp140 polypeptides. Each modified gp140 polypeptide comprises the specific modifications of (i) introduction of two cleavage site point mutations 507E and 514E (ii) a factor Xa site SRIEGR and (iii) a T4-fibritin “foldon” trimerization domain after the factor Xa site. These modifications achieve increased stability of the timer. The invention also features vaccines, nucleic acids, and vectors to deliver and/or facilitate production of the stabilized HIV Env trimers. In addition, the invention features methods of making and using the stabilized HIV Env trimers of the invention as vaccines.
