Methods of inducing an immune response against human immunodeficiency virus (HIV) are described. In particular, methods of inducing an immune response against HIV by co-locally administering an immunogenically effective amount of an isolated HIV envelope (Env) polypeptide and an immunogenically effective amount of an adenovirus vector encoding an HIV antigen, e.g., Env antigen are described. The isolated HIV Env polypeptide and adenovirus vector can be administered in a single composition or in separate compositions, in which the composition or compositions do not contain an adjuvant.