Non-denatured, recombinant human immunodeficiency virus (HIV) Tat that is free of bacterial RNA and endotoxin is employed in an anti-HIV vaccine. A process of producing the recombinant Tat protein includes steps for removing bacterial RNA from the recombinant Tat and for removing endotoxin from the recombinant Tat protein. A Tat-adsorbed nanoparticle formulation and method of making the same. A method of vaccinating against and/or treating HIV infection comprises administering to a subject in need of such vaccination or treatment an immune-response inducing effective amount of the recombinant Tat protein.