nts including nucleic acids", especially when "inadvertent lysis of cells" was induced, could not be avoided.(17,18,19,20) Because of this, to prove that the material which banded at 1.16 gm/ml contained nothing else but particles with "No apparent differences in physical appearances", and that the particles were indeed retroviruses, every retrovirus preparation was further analysed using the following assays: (a) physical-EM for virus count, morphology and purity; (b) biochemical-RT activity, viral and cellular RNA, total protein, gel analyses of viral and host proteins and nucleic acids; (c ) biological-infectivity in vivo and in vitro.(19,20) In other words, the first step in the effort of isolation of a retrovirus is the demonstration that: 1. The particles seen in the cultures band at 1.16 gm/ml; 2. In the 1.16 gm/ml band there is little present but the particles; 3. "No apparent differences in physical appearances" between particles are seen. Isolation of HTLV-III (HIV). In the first, seminal paper on HIV isolation, entitled "Detection Isolation and Continuous Production of Cytopathic Retroviruses (HTLV-III) from Patients with AIDS and Pre-AIDS",(6) Popovic, Gallo and their colleagues first described a leukaemic T-cell line, HT. This cell line was exposed "to concentrated culture fluids harvested from short-term cultures of T-cells... obtained from patients with AIDS or pre-AIDS. The concentrated fluids were first shown to contain particle-associated RT". The finding in the HT cell line as well as in 8 clones derived from it including H4, H9 and H17, of: (a) RT; (b) cell immunofluoresence with serum from a haemophilia patient with pre- AIDS, and "Rabbit antiserum to HTLV-III", was considered evidence for the existence in these cultures of a retrovirus which was named HTLV-III. "Both virus production and cell viability of the infected clone H4 (H4/HTLV-III) were monitored for several months. Although virus production [RT activity] ...
