Disclosed herein are isolated immunogens including variant gp120 polypeptides. In an example, a variant gp120 polypeptide includes a deletion of at least 8 consecutive residues of the fourth conserved loop (C4) between residues 419 and 434 of gp120 according to HXB2 numbering. Also provided are isolated nucleic acid molecules encoding the disclosed isolated immunogens. In an example, an isolated nucleic acid molecule further includes a nucleic acid molecule encoding a hepatitis B surface antigen or a variant thereof. Compositions including the isolated immunogens including variant gp120 polypeptides are also disclosed. In some examples, a composition further includes a carrier protein, such as a hepatitis B surface antigen or a variant thereof (natural or recombinant). Viral-like particles are also provided including any of the disclosed isolated immunogens or compositions. Also disclosed are uses of these variant gp120 polypeptides and nucleic acids encoding variant polypeptides, such as to induce an immune response to HIV-1.
