He was then contacted by Willy Rozenbaum in March 1982 to set up the informal French Working Group SIDA, a self-nominated body to analyse the cases appearing in France.

Leibowitch, informed by the Franco-American literary author Gilles Barbedette of the announcement by Robert Gallo in Medical World News (1 August 1982) that an HTLV type retro-virus could be the cause of AIDS, found in that most succinct brief the profile matching his CD4-tropic exotic viral suspect (in Grasset, Ballantine Books, works cited).

For his part, Willy Rozenbaum, warned in private by Leibowitch that an exotic HTLV-type retrovirus could well be the cause of AIDS, embarked upon a discreet collaboration with the Luc Montagnier team of the Pasteur Institute.

Montagnier, along with his collaborator Jean-Claude Chermann, had just recently received news of the HTLV and AIDS hypotheses by Dr Paul Prunet, the then director of « Recherché & Développement » at Sanofi-Pasteur-Marnes La Coquette, where Leibowitch had given a speech at the end of November 1982.

In a letter to the prestigious magazine Nature Medicine in 2003, as well as in his Nobel Prize acceptance speech in 2008, Luc Montagnier recognized Jacques Leibowitch as being the initiator of the retro-virus hypothesis in France.

[14] Using this craftsman test, Mathez and Leibowitch discovered a disturbing frequency of individuals contaminated by the retro-virus amongst the polytransfusion recipients, and later, in collaboration with Dr François Pinon, head of transfusions at the Cochin hospital, go on to discover, the alarming proportion of HIV positive blood donors (1 in 200) in a pilot study carried out on 10,000 donors in the Paris and Ile-de-France area.

[16] At Garches, Dominique Mathez and Jacques Leibowitch developed a sophisticated and reliable biological test enabling them to quantify active HIV virus levels in patients[17] both before and during their antiviral treatment.

The measuring of HIV viral levels is later to become, in its commercial and industrial version, the universally used test to follow the development of the virus and the effectiveness of various treatments.

[19] The results of the Stalingrad trial underlined the major importance measuring viral levels in real time in the patient in order to evaluate the impact of a given antiviral treatment.

The first results of the ICCARRE study on 48 patients from Garches were published in 2010;[22] as were those of three other withdrawal trials of this kind with short cycles carried out successfully by Anthony Fauci et al.,[23][24][25] at NIH NIAID in the United States.

In his interview of 1 December 2011, on BFM Business, and his appearances on the television show of Michel Drucker (Vivement dimanche 24 May 2013[26]) and Laurent Ruquier (On n'est pas couchés 15 June 2013[27]), Jacques Leibowitch has presented his programme of « canny short cycles », which distinguish themselves from current recommendations, which advocate the intake of medications on 7 days out of 7.