The HIV endonuclease antigenic site peptide corresponds to a sequence highly antigenic in the HIV endonuclease enzymes. Most of HIV-infected sera react with this peptide.H-Glu-Thr-Gly-Gln-Glu-Thr-Ala-Tyr-Phe-Leu-Leu-Lys-Leu-Ala-Gly-Arg-Trp-Pro-Val-Lys-OH or H-ETGQETAYFLLKLAGRWPVK-OH