11th International AIDS Conference Vancouver, British Columbia — July 7-12, 1996

Int Conf AIDS 1996 Jul 7-12; 11:225 (abstract no. Tu.A.382)
Lempicki RA, Pavlick MV, Donoghue DT, Lowry RP, Lane HC; NIH, NIAID, Rockville, MD, USA.

OBJECTIVES: The peripheral blood of HIV-infected individuals accumulates a subpopulation of CD8+ T-cells that are HLA-DR+ and CD38+. During intermittent IL-2 therapy this subpopulation of cells disappears. The purpose of the present study was to attempt to better characterize the various CD8+ subpopulations that accumulate during HIV infection and to delineate the mechanisms responsible for changes in these subpopulations during IL-2 administration.

METHODS: Peripheral blood mononuclear cells were obtained from HIV- and HIV+ donors and separated into CD8+DR+ and CD8+DR- fractions by immunomagnetic bead separation or FACS. Cells were analyzed by FACS and cultured with various IL-2 and PHA concentrations and examined for: i) proliferative responses with 3H-thymidine incorporation, ii) cell viability using propidium iodine exclusion, and iii) cell cycle stage and apoptosis using simultaneous DNA content and cell-surface immunofluorescence analysis.

RESULTS: In addition to DR+ and CD38+ CD8 cells, CD8 cells that were Fas+, CD45RO+, CD28-, CD57+, and CD62L- were also observed to accumulate during HIV infection. Similar to the in vivo findings in patients with HIV infection, CD8+DR+ cells from HIV- donors could not be stimulated to proliferate with IL-2+PHA and had a 26.2% plus or minus 9.8% less survival rate in culture. Likewise, purified CD8+DR- cells from HIV- donors stimulated with PHA alone resulted in the accumulation of DR+ cells that were similar to the CD8+DR+ in vivo with respect to propensity to undergo apoptosis and showed no proliferative capacity. The addition of IL-2 to these CD8+DR- cells resulted in high proliferative responses. Preliminary data using combined cell cycle analysis and cell surface antigen detection revealed that cells from patients with HIV infection had an increased proportion of CD8+, CD25+, CD57+ and HLA-DR+ cells blocked at the G1/S phase of the cell cycle. Additionally, the CD8+DR+ cells had a 3-4 fold increase of sub-G1 DNA relative to CD8+DR-, suggesting that a portion of the CD8+DR+ were undergoing an elevated rate of apoptosis in vivo.

CONCLUSIONS: HIV infection is associated with a state of immune activation resulting in the accumulation of CD8+DR+ cells that are unable to be further expanded. Similar cells can be generated in vitro through activation of CD8+ cells in an environment lacking IL-2. These cells express Fas and are prone to apoptosis. This increased state of activation reflects a cell population that has entered the G1 phase of the cell cycle without transversing the G1/S check point. Administration of IL-2, in vivo or in vitro, prevents cells from becoming blocked at G1/S. Thus, in addition to inducing expansion of CD4+ cells, IL-2 immunotherapy may also induce CD8 T-cells to continue through the cell cycle normally and carry out proper effector function.

960707
TuA382

Copyright © 1996 - International AIDS Society (IAS). Reproduction of this abstract (other than one copy for personal reference) must be cleared through the IAS.