Abstract: Pharmaceutical composition for treating/preventing HIV comprising (i) a polynucleotide encoding HIV envelope protein and (ii) a polynucleotide encoding CD4 receptor protein or; (i) a polynucleotide encoding HIV envelope protein and (ii) a CD4 receptor protein or; a fixed cell expressing an HIV envelope protein complexed with a CD4 receptor protein. Also disclosed are pharmaceutical compositions for treating/preventing HIV comprising an antibody immunospecific for a fixed cell expressing an HIV envelope protein complex with a CD4 receptor protein. The binding of the CD4 to the HIV envelope protein, i.e. gp120, exposes hidden epitopes that may be used as targets in immunotherapy; the presentation of the gp120 and CD4 in the present forms is said to overcome problems with prior art soluble gp120-CD4 complexes.