Date Published: January 9, 2014
Publisher: Public Library of Science
Author(s): Paul W. Denton, Julie M. Long, Stephen W. Wietgrefe, Craig Sykes, Rae Ann Spagnuolo, Olivia D. Snyder, Katherine Perkey, Nancie M. Archin, Shailesh K. Choudhary, Kuo Yang, Michael G. Hudgens, Ira Pastan, Ashley T. Haase, Angela D. Kashuba, Edward A. Berger, David M. Margolis, J. Victor Garcia, Daniel C. Douek.
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.
ART is a lifesaving and effective means to control HIV infection . However, the persistent nature of this infection requires lifelong adherence to daily ART dosing –. This viral persistence, the cumulative costs of ART, adverse events associated with long-term ART and the constant threat of emergence of drug-resistant viral variants have led researchers to pursue HIV eradication therapies that will result in a viral rebound-free interruption of therapy –. Towards this goal, “kick and kill” HIV eradication strategies are being developed . While interventions that can induce expression of latent HIV (e.g. histone deacetylase inhibitors and protein kinase activators) will function as the “kick” –, it is important to note that “kill” strategies cannot rely on the induction of virus expression in latently infected cells to result in cell death . Therefore, candidate “kill” agents, such as immunotoxins, are being considered for incorporation into HIV eradication protocols , . Immunotoxins are recombinant or biochemically linked bi-functional proteins that combine the effector domain of a protein toxin with the targeting specificity of an antibody or ligand –. Soon after HIV was identified as the causative agent of AIDS, several immunotoxins were described as potential therapeutics for HIV , . These interventions had effector domains from plant and bacterial protein toxins and targeting moieties against either the HIV Env glycoprotein (gp120, gp41) or cellular markers including CD4, CD25 or CD45RO –. The immunotoxin we chose to evaluate for in vivo efficacy herein, 3B3-PE38, combines the 3B3 scFv which targets the conserved CD4 binding site of HIV-1 gp120 with the Pseudomonas exotoxin A (PE38) effector domain .
Despite the lifesaving benefits of ART in HIV patients, relatively little is known regarding the organ specific impact of this therapy on HIV production and persistence . Improving our knowledge of the systemic effects of ART is a critical step in the development of successful HIV eradication therapies. To address this need, we characterized the impact of ART by analyzing both drug penetration and HIV production in different tissues throughout BLT humanized mice. We found that ART penetration into multiple organ systems is sufficient to significantly reduce the number of cells producing HIV, as well as cell-associated vRNA levels, throughout the body. However, HIV persists during ART in every organ analyzed.