This invention is in the field of lymphadenopathy virus, which has been designated Human Immunodeficiency Virus Type 1 (HIV-1) to detect the presence of DNA, RNA or antibodies of the lymphadenopathy retrovirus associated with the acquired immune deficiency syndrome or of the lymphadenopathy syndrome by the use of DNA fragments or the peptides encoded by said DNA fragments. The invention further relates tot he DNA fragments, vectors comprising them and the proteins expressed.