This study is a follow-up, re-boosting study of Study CT-BI Vacc-4x 2007/1 (EudraCT Number 2007-006302-13) performed in US and Europe (UK, Germany, Spain and Italy). All subjects to be included have been given a therapeutic immunization with Vacc-4x during the CT-BI Vacc-4x 2007/1 study. During the study a reduction in the viral load set-point (mean viral load at Week 48 and Week 52, or if Week 52 not reached, mean viral load of the last two measured values before restart of ART) was seen in the Vacc-4x group compared to placebo group. Further stimulation of the immune system by re-boosting with Vacc-4x could reduce the viral load set-point further.