Background:  There is renewed interest in targeting HIV reservoirs with the ultimate goal to cure HIV. Thus, techniques that accurately measure HIV reservoirs are needed. Plasma viral load, total and integrated HIV DNA have been proposed as surrogates of HIV reservoir. Since approaches that target reservoirs may also induce ongoing replication, techniques that detect ongoing replication are also needed. We propose that measurement of integrated HIV DNA is a superior surrogate to detect changes in reservoir size. In addition, as recent rounds of replication may result in spikes of un-integrated HIV DNA, combined measurements of total and integrated HIV DNA may serve as a tool to detect ongoing replication. In a separate abstract we report that 5 weeks of pegylated interferon-a2α (IFN-α) and ART, followed by a structured treatment interruption (STI) in the presence of IFN-α result in viral control (<400 copies/mL) for 12 to 24 weeks off ART in a subset (n = 9 of 20) of patients, termed responders. We show that integrated HIV DNA is reduced 12 weeks after stopping ART. Thus, an apparent reduction in reservoir size in the presence of a STI provides an ideal cohort to assess the utility of measuring total and integrated HIV DNA concurrently.

Methods:  Total and integrated HIV DNA were measured in responders and nonresponders at baseline on ART, after 5 weeks of IFN-α + ART, and 12 weeks after stopping ART, and were compared to plasma viral load.

Results:  There was a trend toward reduced integration in IFN-α responders after 5 weeks of dual therapy and a significant reduction after 12 weeks of interferon only (p = 0.01, paired Students t test). The reduction in reservoir size was not detected by total HIV DNA or by ultrasensitive plasma viral load. The ratio of total over integrated HIV DNA increased during IFN-α monotherapy, and was accompanied by a subtle increase in plasma viral load suggesting that ongoing replication occurred.

Conclusions:  Our data suggest that integrated HIV DNA may be a surrogate of reservoir size and that concurrent measurements of total and integrated HIV DNA may provide a means to detect ongoing HIV replication. It appears that ongoing replication occurred during the IFN-α monotherapy in patients yet integrated HIV DNA continued to decline. We speculate that ongoing replication that occurs after ART interruption in the presence of IFN-α may further stimulate immune clearance of cells carrying integrated HIV DNA.