CTN 173: Vaccination before treatment interruption

About The Study

The purpose of this study was to determine if vaccination before a structured treatment interruption (STI) is associated with an improvement in immune function, resulting in a delayed and reduced rebound in the amount of virus in the blood. The combined use of ALVAC, which enhances CD8 T cell responses and Remune, which provides CD4 T cell help, has the potential to induce anti-HIV responses capable of controlling viral replication. The study measured changes in CD4 cell count and viral load.

Study Approach

This was a randomized, double-blind, controlled study with a target enrolment of 60. Researchers were seeking participants with a viral load below 50 copies/ml for at least two years, and a CD4 cell count above 500 cells/mm3. Participants were randomized to one of three arms: one arm received Remune and ALVAC, the second arm received Remune and placebo and the third arm received matching placeobs. All participants interrupted their antiretroviral therapy at week 24.

Study Population

This study recruited 52 participants from sites in Ontario and Quebec. The average CD4 cell count was 775 cells/mm3. The average age of participants was 52.

Results

The average time to confirmed viral load above 50 copies/ml was 24.5 days for the Remune and ALVAC arm, 23 days for the Remune and placebo arms and 13.5 days for the placebo arm. At week 36, viral load was not different between the groups. The proportion of participants that restarted antiretroviral therapy (ART) was not different between groups but time to reach pre-defined criteria to restart ART was greater in the two vaccine arms. Although this approach did not result in clinically relevant control of viral replication, a number of vaccine recipients experienced a delay in viral load rebound and less rapid CD4 decline.

Conclusion

This study showed that vaccination with ALVAC with Remune delayed viral load rebound, but did not have impact on viral load set-point measured 12 weeks after ART interruption. However, it did lengthen the time for participants to meet pre-defined criteria to restart ART.

Note: These results were taken from an abstract presented at the 17th Annual Canadian Conference on HIV/AIDS Research in Montreal, Quebec, April 24-27, 2008.