Lessons learned from HIV treatment interruption: safety, correlates of immune control, and drug sparing

Therapeutic approaches seeking to limit the exposure to antiretroviral drugs while retaining the benefits of continuous therapy have become an active area of investigation in HIV therapy research. Although early attempts to use interruptions of therapy as auto-vaccination strategies have shown little success, much has been discovered in regards to immunological correlates of viral control in acute and chronic infection, viral evolution, and the safety of single or multiple therapy interruptions in different patient sub-groups (acutely infected, chronically infected, and multi-drug resistant). Here we review safety data and candidate factors that may contribute to the striking differences observed between patients that undergo similar treatment interruption strategies but achieve different outcomes in controlling HIV replication. Differences between acute and chronic infection in the viral component (e.g. diversity of the viral pool) and the host immune system (e.g. low avidity CTL memory response), which may not be reversed by ART, may determine the potential for suppressive immune response upon therapy interruption. Consistent with goals of limiting toxicity and cost of antiretroviral drug regimens, safety outcomes to date indicate that intermittent therapy strategies may safely continue to be investigated in early and chronically infected patients. Based on ongoing research, we identify the topics to be targeted in future studies.