If reverse transcriptase activity is present, it confirms that the virus is a retrovirus. In December 1982, heavy research began and clinical observations suggested that the disease attacked immune cells because of the significant CD4 cell depletion. However, the depletion of the CD4 lymphocytes made it very difficult to isolate the virus in patients with the disease later known as, AIDS. Because of the difficulty isolating an infected cell from a patient with late disease progression, Barré-Sinoussi and her colleagues decided to use a lymph node biopsy from a patient with generalized lymphadenopathy. Generalized lymphadenopathy was a common symptom of patients in the early stages of disease progression. In the second week of checking the biopsied cell cultures for reverse transcriptase activity, enzymatic activity was detected and increased for a short time until the reverse transcriptase activity decreased dramatically after the T-lymphocytes in the culture began to die. Barré-Sinoussi and her colleagues decided to add lymphocytes from a blood donor in order to save the culture and it proved successful after the virus transmitted to the newly added lymphocytes from the blood donor and significant reverse transcriptase activity was again detected. At this point, the virus was named LAV for Lymphadenopathy Associated Virus, which would later be renamed to HIV, the human immunodeficiency virus. 1983 marked the beginning of Barré-Sinoussi's career researching HIV that continued until her retirement. 1983 was also the year it became clear that HIV was not only a target for what was known as the 4Hs, homosexuals, hemophiliacs, Haitians and heroin addicts, but that HIV was also targeting heterosexuals – making the likelihood that the HIV related disease, AIDS, was an epidemic very high. Francoise Barré-Sinoussi remained at the Pasteur Institute and was appointed head of the Biology of Retroviruses Unit in 1992. The Biology of Retroviruses Unit was reconfirmed in 2005 and renamed the Regulation of Retrovirial Infections Unit. Currently, the unit is working on vaccine research against HIV and the correlates of protection against AIDS for immunotherapy. Barré-Sinoussi's career has also included integration with resource-limited countries, such as Vietnam and Central African Republic. Her experiences working in developing nations with the World Health Organization were truly eye-opening experiences for her and motivated her to continue to collaborate scientifically with various countries through Africa and Asia. This collaboration has promoted many exchanges and workshops between young scientists from resource-limited countries and researches in Paris.