18th International HIV Drug Resistance Workshop Basic Principles & Clinical Implications June 9–13 2009, Fort Myers, Florida, USA

ROLES OF NFAT, CELL DIVISION AND IL-7 STIMULATION ON HIV-1 REACTIVATION FROM LATENCY IN PRIMARY MEMORY T-CELLS

Antivir Ther 2009; 14 Suppl 1:A4 (abstract no. 2)

A Bosque and V Planelles
Department of Pathology, University of Utah, Salt Lake City, UT, USA

BACKGROUND: Molecular studies of HIV type-1 (HIV-1) latency have been facilitated by the recent availability of primary cell models.

METHODS: We developed a system whereby naïve cells from the periphery of healthy donors are induced to undergo normal development ex vivo in the presence of select cytokine cocktails and antigenic stimulation through CD3/CD28. These cells are infected while in the activated state and return to quiescence as memory cells. Infection of these ex vivo generated memory cells leads to latency with a high frequency (approximately 90% of infections) and leads to a polyclonal population of integrated species. Using this paradigm, we explored the signalling pathways that influence HIV-1 latency.

RESULTS: Our findings contradict several notions that were arrived through the use of transformed cell lines. Firstly, viral reactivation following TCR engagement is completely dependent on Lck and NFAT activation, while NFκB is not required. The lack of a requirement for NFκB was confirmed by the inability of PKC agonists and TNF-α to activate latent proviruses. Secondly, general modifiers of the histone code, such as histone deacetylase inhibitors, had no ability to reactivate latent HIV-1 in primary memory cells. Proliferation of memory T-cells can be driven not only by antigenic stimulation but also by cytokines. Therefore, it is conceivable that the latent viral reservoir may also be perpetuated or even expanded through homeostatic proliferation of memory T-cells. We examined the influence of cell cycle entry and found that memory lymphocytes harboring latent proviruses are perfectly capable of cell division in the absence of viral reactivation.

CONCLUSIONS: Although CD3/CD28 stimulation provides a potent signal to study viral reactivation ex vivo, it would be unlikely to have therapeutic use. In an effort to find alternative pathways, we screened a number cytokines and chemokines. We found that a combination of IL-2 and IL-7 is a potent inducer of latent HIV-1 independently of NFAT and NFκB. Therefore, reactivation via IL-2 and IL-7 represents an alternative pathway to T-cell receptor engagement and represents a novel therapeutic avenue for purging latent reservoirs.

ACKNOWLEDGEMENTS: This work was supported by NIAID grant AI49057.

2009-06-09
2

Copyright © 2009 - International Medical Press Ltd.. Reproduction of this abstract (other than one copy for personal reference) must be cleared through the International Medical Press Ltd. 2-4 Idol Lane, London EC3R 5DD UK.