Bridging the Gap: Conference Record [Abstract book, International Conference on AIDS (12th: 1998: Geneva, Switzerland)]

12th World AIDS Conference

Abstracts 21162-21165 271

Methods: 3- and 4-colors flow cytometry for the phenotypic studies; ELISA
for soluble molecules (sCD95); stimulation with anti-CD95 mAbs or use of the
HUT78 cell line and cytotoxicity for functional analyses.
Results: During the acute phase of the infection, almost all PBL (in the reported
case 93%) expressed a functional CD95. CD38 was expressed at high levels
not only by CD45RA CD4+ or CD8+ T lymphocytes, but also by CD45RA+
CD8+ T cells. Plasma sCD95 was present at high levels for several months.
Gated on CD3+,CD4+

CD38
S.CD45RA

FL 1 -hieght i '31 vs FL2-he,:-iht 14j
CD95
CD45RA

Gated on CD3+,CD8+

CD38
t5R A
-. -O-)4 s R A
' * * _ '^

FL1 -Helgf 3)v FL2-Heigiht (4
CD95

CD45RA

Conclusion: Activation-induced cell death and related markers decreased
with time spontaneously or after therapy, with different kinetics. On the contrary,
sCD95 plasma levels were unaffected either by viral load or therapy with AZT
or protease inhibitors, and had no correlation with the aforementioned markers,
including membrane CD95. The immune activation existing during acute HIV
syndrome likely plays a role in the loss not only of CD4+ but also of CD8+ cells,
thus influencing the entire course of the disease.
280*/21162 Influence of interleukin-15 on apoptosis and
proliferation of T lymphocytes of HIV-infected
individuals: Comparison with interleukins-2 and
-12
Honami Naora, M.L. Gougeon. Unite D'oncologie Virale/Institut Pasteur 28 Rue
du Dr Roux, 75724 Paris Cedex 15, France
Background: Interleukin (IL)-15 is a recently discovered cytokine which shares
several biological activities with IL-2, including an ability to stimulate proliferation
of activated T lymphocytes. Recent studies using activated T lymphocytes derived
from healthy individuals indicate that IL-15 can inhibit spontaneous cell death by
apoptosis in vitro, and block apoptosis induced via the Fas molecule. This study
examined whether IL-15 could exert a protective effect on T lymphocytes of
HIV-infected individuals, which are highly activated and prone to spontaneous
and Fas-induced apoptosis in vitro.
Methods: Peripheral blood mononuclear cells (PBMCs) of HIV-infected individuals were cultured in the absence or presence of exogenous IL-15 (10 ng/ml)
and/or immobilized anti-Fas antibody. The levels of apoptosis and proliferation
were assessed by flow cytometry and thymidine incorporation, respectively.
Results: The presence of IL-15 in cultures of PBMCs from HIV-infected individuals enhanced proliferation and reduced the overall level of spontaneous
apoptosis in both CD4+ and CD8+ T lymphocyte subsets. Such protection against
T lymphocyte loss appeared to be associated with upregulated expression of the
survival molecule bcl-2. Exogenous IL-15 was observed, in general, to upregulate
bcl-2 expression morethan IL-2, and was markedly more effective than another
T cell-stimulatory cytokine, IL-12, when used at the same concentration. However, IL-15, like IL-2 and IL-12, failed to exert a strong protective effect against
Fas-induced apoptotic cell death.
Conclusion: The results suggest that IL-15 could exert a protective effect
against loss of T lymphocytes of HIV-infected individuals through enhanced survival and proliferation, rather than via direct inhibition of Fas-mediated apoptotic
cell death.

21163 Therapy induced reduction in plasma virus load leads to
decrease in lymphocyte apoptosis in association with
decrease in T cell activation markers
Savita Pahwa, Suren Chavan, S.L. Tamma, M. Kaplan. North Shore Univ
Hosp-NYU School of Med, Manhasset, NY, 350 Community Drive, Research
Bldg #303 North Shore Univ Hosp Manhasset, NY 11030, USA
Objectives: Patients with HIV infection manifest increased T lymphocyte apoptosis. This study investigated whether therapy-induced reduction in virus load
influences T lymphocyte apoptosis (TA) in HIV infection.
Methods: 23 HIV infected adults naive to protease inhibitors, with >50 CD4
cells/pl (mean ~ SD, 209 ~ 132) and >15,000 plasma HIV RNA copies/ml (mean
~ SD, loglo RNA copies, 5.02 ~ 0.46), were enrolled in a double blind trial in
which they received nelfinavir (NFV) monotherapy (n = 11), D4T monotherapy (n
= 5) or NFV + D4T (n = 7) for 24-28 wks, followed by triple therapy (NFV + 2 RTIs)
for additional 20-24 wks. Spontaneous TA was determined in PBMC cultured for
3 days by light scatter (high forward, low side) analysis of lymphocytes gated for
CD3+CD45+ antigens by flow cytometry. Concurrently, CD4 and CD8 lymphocyte
subsets and plasma virus load (VL; b-DNA assay, Chiron) were determined at
intervals of 4 wks.
Results: All patients showed decreases in plasma VL and increases in CD4
cells in both phases of the study. At 48 wks, mean plasma HIV RNA copies/ml
decreased by 1.79 ~ 0.6 loglo), CD4 counts increased by 148 ~ 121 cells/jol)
and TA decreased from 47 ~ 14% at baseline to 23 ~ 16%, p < 0.01. The rate
of change of % TA correlated directly with rate of change of loglo VL (rs = 0.62, p
< 0.001) and inversely with rate of change of absolute CD4 counts (rs = -0.67,
p < 0.01). The correlation of TA with plasma VL (rs = 0.82, p < 0.001) and with
CD4 (rs = -0.8, p < 0.001) was greatest during the period of maximum decline in
plasma VL. Furthermore, decline in % of CD8 cells expressing activation markers
DR and CD38 correlated directly with %TA (p < 0.02). The expression of Fas
(CD95) on T cells correlated with plasma VL and TA as well.
Conclusions: These findings suggest that therapy-induced suppression of HIV
leads to reduction in TA and thus contributes to the initial increase in the pool
of T lymphocytes. Possible mechanisms for reduction in TA include 1) reduction
in chronic antigenic stimulation resulting in fewer persistently activated T cells
and 2) reduction in apoptosis induced via virus/viral protein/T cell interaction, e.g.
CD4 crosslinking in CD4 T cells.
275*/21164 Macrophages-mediated CD8+ T-cell killing via
CXC-R4/ENV interactions during HIV infection
Georges Herbein1, U. Mahlknecht2, W.A. O'Brein1, E. Verdin3. University Of
Texas Medical Branch Galvenston TX 77 555; 2The Pic Ower Institute New York
NY; 3Gladst One Inst Univ Of California San Francisco CA, USA
Objectives: To understand the increase in CD8+ T cell turnover throughout HIV
infection and CD8+ T cell depletion in late stages.
Results: We observed that the rate of CD8+ T cell apoptosis is dramatically enhanced during HIV infection of peripheral blood mononuclear cells in vitro.
HIV-induced CD8+ T cell apoptosis was mediated by macrophages and was more
pronounced with lymphotropic HIV strains. CD8+ T cell apoptosis was induced in
a dose-dependent manner by recombinant lymphotropic viral envelope glycoprotein (gp120) alone or by stromal cell-derived factor 1 (SDF-1), the physiological
CXCR4 ligand, but not by RANTES or MIP-11/, two ligands for CCR5. Induction
of CD8+ T cell apoptosis by macrophages was contact-dependent and was mediated by the interaction between macrophage membrane-bound tumor necrosis
factor a (TNFu) and CD8+ T cell TNF-receptor 2. Both cell surface proteins
were upregulated as a result of HIV infection or rgpl20 treatment. Interestingly,
both SDF-1 and lymphotropic rgpl20, but neither RANTES or macrophage-tropic
rgpl20, upregulated TNF-receptor 2 on CD8+ T cells. CD8+ T cell apoptosis observed in peripheral blood mononuclear cells isolated from HIV-infected patients
also was mediated via the TNF-receptor 2.
Conclusion: These data demonstrate that HIV infection causes a dysregulation of the interaction between TNF-receptor 2 on CD8+ T cells and TNFc, on
macrophages which results in increased CD8+ T cell apoptosis in the presence
of lymphotropic viruses.
21165 | Fas mediated apoptosis of CD4 T cells from HIV+ patients
is proportional to CD4 cell count and plasma HIV RNA
copy number
Jorge Villacian, D.H. Dockerell, C.V. Paya. Mayo Clinic/Foundation 200 First
Street S. W. Rochester MN, USA
Background: Apoptosis mediated by Fas-Fas ligand (FasL) interaction is one of
the proposed mechanisms to explain CD4 T cell depletion in patients infected
with HIV. We have prospectively analyzed the degree of Fas-mediated apoptosis
in a cohort of HIV+ patients that were anti-retroviral naive or on monotherapy
comparing it to control individuals and correlating it with HIV RNA copy number
in plasma and CD4 T cell counts.

Methods: Freshly isolated peripheral blood lymphocytes were incubated exvivo for 18 hours in wells pre-coated with an isotype control antibody (baseline
apoptosis) or with M3 monoclonal anti-Fas antibody (Fas mediated apoptosis).
Apoptosis was measured by Hoechst 33342 staining of CD3+/CD4+ T cells using
flow cytometry.
Results: CD4 T cells from the HIV+ group (n = 15) when compared to those
from control volunteers (n = 12) exhibited higher degrees of "baseline" (spon