Abstract: A heteroconjugate is formed by linking a T cell binding ligand (TCBL) such as Peptide J of .beta.-2 microglobulin to a modified HGP-30 antigentic peptide fragment of p17 gag peptide, such as. for exampleATL YSV HQR IDV KDTKEA LEK IEE EQN KS (SEQ ID NO: 5)The heteroconjugate is effective in eliciting a THI directed immune response and provides a vaccine composition for treating or preventing AIDS.