In order to better understand the source(s) and the mechanism(s) of HIV persistence and to potentially lead to further suppression of HIV from viral reservoirs, we propose to examine the effect of co-administration of enfuvirtide, an entry inhibitor of HIV, on diminution of the size of the viral reservoir in infected individuals who are receiving effective antiviral therapy for extended periods of time (> 5 years).

Inclusion Criteria:

1. Patient must be HIV infected
2. Patient must be > 18 years old
3. Patient must be taking standard combination antiretroviral therapy with 2-3 NRTIs and 1-2 PIs or a NNRTIs for at least five years
4. Patient must have a viral load < 50 copies/mL (using the standard available methods of detection) during the entire time on standard combination antiretroviral therapy except for initial fall of viral load
5. Patient must have a CD4 count above 400 cells/mm3 in last 3 months
6. Female patient must agree to use two methods of birth control or abstinence during the period of the study
7. Patient has to have signed full informed consent

Exclusion Criteria:

1. Patient who would have difficulty participating in a trial due to non-adherence or substance abuse

2. Patient who have taken mono or dual antiretroviral therapy

3. Patient who have had a viral load > 50 copies/mL on any antiretroviral regimen

4. Patient with any of the following abnormal laboratory test results in screening:

   • Hemaglobin < 100 g/L
   • Neutrophil count < 750 cells/uL
   • Platelet count < 50,000 cells/L
   • AST or ALT > 5X the upper limit of normal
   • Creatinine > 250 umol/L

5. Patient with a malignancy

6. Patient with other significant underlying disease (non-HIV) that might impinge upon disease progression or death

7. Patient with an active AIDS-defining illnesses in the past six months

8. Patients who are pregnant