In 1983, Montagnier et al. have isolated a retrovirus, now termed Human immunodeficiency virus (HIV), from a patient with lymphadenopathy and proposed that HIV may cause AIDS. Antibody against this virus has since been found in many, but not all AIDS patients (Duesberg, 1993) and in 17 million healthy people (World Health Organization, 1995).

Eleni Papadopulos, Val Turner, John Papadimitriou, David Causer, Bruce Hedland-Thomas & Barry Page (Papadopulos-Eleopulos et al., 1995) and Stefan Lanka (Lanka, 1995) maintain that the very existence of HIV is dubious because (i) HIV has not been properly isolated and thus could not have been properly identified. According to Papadopulos et al. "HIV has never been isolated as an independent particle separate from everything else." (Papadopulos-Eleopulos et al., 1995) ; and (ii) because antibodies against HIV are not specific (Papadopulos-Eleopulos, Turner and Papadimitriou, 1993) . They submit that the following evidence is not "specific" for HIV: identifying in the growth medium of infected human cell cultures either the existence of virus-like particles with the electron microscope, or of reverse transcriptase associated with such particles, or of certain HIV antigens or proteins associated with particles, because each of these could be cellular materials or could be from cell-borne (endogenous) retroviruses other than HIV. Indeed, each of these criteria could reflect another retrovirus, and some of theses criteria, eg. particels and proteins, could reflect non-viral material altogether.

However, the Papadopulos-Lanka challenge, that HIV does not exist, fails to explain (i) why virtually all people who contain HIV DNA also contain antibodies against Montagnier"s HIV strain -the global standard of all "HIV tests"- and (ii) why most, but certainly not all people who lack HIV DNA contain no such antibodies. The presence of HIV-reactive antibodies in some uninfected people reflects an inherent limitation of tests for antibodies against viruses and other microbes. Since even the simplest microbes display thousands of antibody docking sites, termed epitopes, antibodies against a given microbe may cross-react with an otherwise unrelated microbe if the two share some epitopes.

In view of the current controversy about the identification of HIV, the British AIDS magazine Continuum has offered in its Jan./Feb. issue a "Missing virus! £1000 Reward" for prove of the isolation of HIV, and the reward was reposted "105 days later ... we"re still waiting" in the March/April, 1996 issue (Christie, 1996a; Christie, 1996b; Continuum, 1996) . The stakes have since been raised considerably by a private reward of £10,000 from Alex Russell from The DMS Watson Library, University College London (letter from Alex Russell to Peter Duesberg, 2/28/96), and have now been raised even further by a £25,000 reward from James Whitehead from The International AIDS Freedom Network (IAFN), London (letter from Fred Cline, San Francisco Representative of the IAFN, April 2, 1996; and letter from Alex Russell to Fred Cline, undated, April 1996).

Here I take up these challenges. I will argue that HIV exists, and has been properly identified as a unique retrovirus on the grounds that (i) it has been isolated - even from its own virion structure - in the form of an infectious, molecularly cloned HIV DNA that is able to induce the synthesis of a reverse transcriptase containing virion, and (ii) that HIV-specific, viral DNA can be identified only in infected, but not in uninfected human cells. I will base my case for the isolation of HIV on the most rigorous method available to date, ie. molecular cloning of infectious HIV DNA, rather than only on the much less stringent, traditional "rules for isolation of a retrovirus ... discussed at the Pasteur Institute, Paris, in 1973" that were stated criteria of isolation in the Continuum"s Missing virus reward (Continuum, 1996) . Indeed I will show that molecular cloning of infectious HIV DNA exceeds the criteria of the old "Pasteur rules".

(i) Isolation of HIV: The existence of the retrovirus HIV predicts that HIV DNA can be isolated from the chromosomal DNA of infected cells. This prediction has been confirmed as follows: Full-length HIV-1 and HIV-2 DNAs have been prepared from virus-infected cells and cloned in bacterial plasmids (Fisher et al., 1985; Levy et al., 1986; Barnett et al., 1993) . Such clones are totally free of all viral and cellular proteins, and cellular contaminants that copurify with virus banded in sucrose gradients at a density of 1.16 g/ml according to the "Pasteur rules". Indeed, these clones are even free of genomic HIV RNA. Infectious HIV-1 and HIV-2 DNA clones productively infect human cells to initiate HIV replication (Fisher et al., 1985; Levy et al., 1986; Barnett et al., 1993) . Such infected ("transfected") cells contain HIV-specific DNA, and produce particles that contain reverse transcriptase, HIV-specific antigens (Fisher et al., 1985; Levy et al., 1986) , have diameters of 100 nm under the elctron microscope (Fisher et al., 1985) , as expected for retroviruses, and produce infectious virus that is neutralized by antisera from certain AIDS patients (Fisher et al., 1985; Levy et al., 1986; Barnett et al., 1993) . Since infectious HIV DNA has been isolated from infected human cells that is free of HIV"s own proteins and RNA as well as from all cellular macromolecules, HIV isolation has passed the most vigorous standards available today. In other words these infectious DNA clones meet and exceed the isolation standards of the traditional "Pasteur rules". Isolation of infectious HIV DNAs is theoretically the most absolute form of isolation - it is the equivalent of isolating the virus" soul, its genetic code, from the virus" body, the virus particle. Thus HIV isolation based on molecular cloning exceeds the old standards defined as "Pasteur rules" by Continuum.

(ii) Identification of HIV. The existence of HIV predicts that infected cells contain a unique, virus-specific DNA of 9150 nucleotides that cannot be detected in DNA of uninfected human cells. The probabilities that cellular DNA and other viral DNAs would contain the same sequence of 9150 nucleotides is 1 in 49150, or 1 in 104500 - extremly close to zero!