Twelve patients will be treated with administration of recombinant human interferon-beta1a. Assessment of efficacy will be based on reduction of spontaneous proliferation and proviral load. As a secondary measure the clinical response of patients will be evaluated. The study will entail an 8-week pretreatment period, a 28-week treatment phase with escalation of the interferon-beta1a dose, and a 12-week post-treatment phase. In cases where dose escalation leads to intolerable side-effects, patients will be continued at the highest tolerated dose of medication. Spontaneous proliferation, viral load, and clinical parameters will be determined monthly.