Targeted Cytotoxic Therapy Kills Persisting HIV Infected Cells During ART

Abstract

Antiretroviral therapy (ART) can reduce HIV levels in plasma to undetectable levels, but rather little is known about the effects of ART outside of the peripheral blood regarding persistent virus production in tissue reservoirs. Understanding the dynamics of ART-induced reductions in viral RNA (vRNA) levels throughout the body is important for the development of strategies to eradicate infectious HIV from patients. Essential to a successful eradication therapy is a component capable of killing persisting HIV infected cells during ART. Therefore, we determined the in vivo efficacy of a targeted cytotoxic therapy to kill infected cells that persist despite long-term ART. For this purpose, we first characterized the impact of ART on HIV RNA levels in multiple organs of bone marrow-liver-thymus (BLT) humanized mice and found that antiretroviral drug penetration and activity was sufficient to reduce, but not eliminate, HIV production in each tissue tested. For targeted cytotoxic killing of these persistent vRNA ⁺ cells, we treated BLT mice undergoing ART with an HIV-specific immunotoxin. We found that compared to ART alone, this agent profoundly depleted productively infected cells systemically. These results offer proof-of-concept that targeted cytotoxic therapies can be effective components of HIV eradication strategies.

Author Summary

Antiretroviral therapy (ART) improves the quality of life for HIV infected individuals. However, ART is currently a lifelong commitment because HIV persists during treatment despite being suppressed below detection. If therapy is stopped, the HIV reappears. A concerted effort is ongoing to develop new eradication therapies to prevent virus rebound, but there are challenges to be overcome. Our work is a major step forward in this process. We measured persistent HIV throughout the body during ART using bone marrow/liver/thymus (BLT) humanized mice, a model validated to study HIV persistence. HIV infected BLT mice were treated with tenofovir, emtricitabine and raltegravir. Despite documented tissue penetration by these drugs, we found that HIV expression persists in cells isolated from all the tissues analyzed (bone marrow, thymus, spleen, lymph nodes, liver, lung, intestines and peripheral blood cells). We therefore complemented ART with an immunotoxin that specifically kills HIV expressing cells while leaving other cells untouched. Our results demonstrate a dramatic reduction in persistent HIV throughout the body resulting from the killing of virus producing cells. Thus, our study provides new insights into the locations of HIV persistence during ART and a demonstration that persistent HIV can be successfully targeted inside the body.