The invention provides a polynucleotide encoding an envelope protein comprising gp120 of human immunodeficiency virus-1 (HIV-1) having a mutation at amino acid residues 197-199 whereby a single N-linked glycan is removed. In a typical embodiment, the mutation replaces the asparagine (N) at residue 197 with another amino acid, such as glutamine (Q), creating an N197Q mutation. Because the N197 glycan is highly conserved among HIV-1 subtypes, this approach is applicable across HIV-1 isolates. The invention provides polypeptides, polynucleotides encoding the polypeptides, vectors, and recombinant viruses containing the polynucleotides, antigen-presenting cells (APCs) presenting the polypeptides, immune cells directed against HIV, and pharmaceutical compositions. The invention additionally provides methods, including methods for preventing and treating infection, for killing infected cells, for inhibiting viral replication, for enhancing secretion of antiviral and/or immunomodulatory lymphokines, and for enhancing production of neutralizing antibody.