The present invention relates, in general, to a method of inducing an immune response to HIV-1 in a mammal and, in particular, to a vaccine formulation suitable for use in such a method comprising an HIV-1 envelope (Env) immunogen comprising recombinant Envs with some degree of high-mannose glycan residues and a Toll-like receptor (TLR) agonist-supplemented squalene-based adjuvant.