Some preliminary evidence also suggests that therapeutic vaccines themselves Fludarabine may be able to activate at least some latent virus by stimulating infected memory CD4 T cells that are HIV-specific [34] and [54]. Therapeutic vaccine development for individuals under ART treatment poses particular challenges for clinical trial design. Specific issues include: safe use of analytical treatment interruptions (ATI) in clinical trials, identification of clinically relevant biomarkers, assays to measure the HIV reservoir [55] and [56],

and potential differences in the optimal use of therapeutic vaccine approaches for different populations. Dr. Carol Weiss in her presentation highlighted the fact that there is limited regulatory precedent for approved therapeutic vaccines. The antiviral effect of therapeutic HIV vaccines is difficult to measure during ART and the immune correlates of therapeutic benefit are unknown. Since there is now limited tolerance from an individual or public health perspective for allowing the virus to persist in a readily detectable manner, the era in which vaccines might be used to simply partially control HIV or delay time to ART, without showing a clinical benefit, has passed [57]. Therapeutic

vaccines which result in safe, sustained, control of viral replication AZD2281 ic50 comparable to that achieved with accessible standard ART could possibly meet with regulatory approval, but this is a high standard that will be extraordinarily difficult to achieve. A more feasible outcome with a vaccine might be partial clearance else of the reservoir during ART, but the clinical benefit of this is unknown. An ultimate objective would be an intervention, including therapeutic vaccination performed during ART, which would result in sufficient diminishment of residual virus and control of viral replication as to allow discontinuation of ART. With over 35 million people living with HIV [58], the development of a safe, effective, and accessible HIV therapeutic vaccine capable of either clearing reservoir during ART (presumably as

a component of a combination cure strategy) or causing sustained control of virus in absence of ART represents a highly desirable global public health goal. The focus on elucidating mechanisms or markers of control and elimination of virus must sharpen. New information should come from a variety of sources, including NHP experiments, studies of natural infection, and clinical trials (especially experimental medicine trials to identify mechanisms of pathogenesis, or to demonstrate proof-of-concept). The required immune response and therapeutic benefit from therapeutic vaccine remains an area of discussion and debate. At the same time, there are promising areas of scientific focus and strategic approaches that could accelerate the development of a therapeutic vaccine.