Biomarkers of outcomes of disease, treatment and complications: Edited by H. Clifford Lane and Jens D. LundgrenBiomarkers of HIV replicationSiliciano, Janet Da; Siliciano, Robert Fa,bAuthor Information aJohns Hopkins University School of Medicine, USA bHoward Hughes Medical Institute, Baltimore, Maryland, USA Correspondence to Robert F. Siliciano, MD, PhD, 879 Broadway Research Building, Johns Hopkins University School of Medicine, 733 N. Broadway, Baltimore, MD 21205, USA Tel: +1 410 955 2958; e-mail: [email protected] Current Opinion in HIV and AIDS: November 2010 - Volume 5 - Issue 6 - p 491-497 doi: 10.1097/COH.0b013e32833f206f Buy Metrics Abstract Purpose of review Viremia provides a biomarker for HIV-1 replication in various tissues. The purpose of this review is to discuss the relationship between viremia and viral replication at a theoretical level and to review recent advances in understanding this relationship, particularly in the context of highly active antiretroviral therapy (HAART). Recent findings Recent studies have focused on understanding the extremely low level of residual viremia that can be detected in patients on HAART. The two major explanations for this residual viremia are that it represents ongoing cycles of replication that continue despite HAART or that it represents release of virus from stable reservoirs. The recent finding that intensification of HAART does not further reduce residual viremia supports that latter hypothesis. Direct sequence analysis of the residual viremia has provided new insights into the complex relationship between residual viremia and viral reservoirs. Summary In patients with untreated HIV-1 infection, the level of viremia is a direct indication of the level of viral replication and a predictor of the rate of CD4 depletion. However, when viral replication is suppressed by HAART, the level of residual viremia is to a large extent an indication of virus release from stable viral reservoirs. © 2010 Lippincott Williams & Wilkins, Inc.