From the Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases,
National Institutes of Health, Bethesda, Maryland 20892
Although it has been demonstrated that certain cytokines, particularly proinflammatory cytokines, can enhance ongoing viral replication in peripheral blood mononuclear cells (PBMCs) of
HIV-1-infected individuals, it is unclear what role these cytokines play in the induction of
HIV-1 replication in latently infected, resting CD4+ T cells. This study demonstrates that the
in vitro combination of the proinflammatory cytokines interleukin (IL)-6 and tumor necrosis
factor (TNF)-
together with the immunoregulatory cytokine IL-2 are potent inducers of viral
replication in highly purified, latently infected, resting CD4+ T cells derived from HIV-infected
individuals who are antiretroviral therapy-naive as well as those who are receiving highly active antiretroviral therapy (HAART). Viral replication induced by this combination of cytokines was completely suppressed in the presence of HAART in vitro. Given that an array of
cytokines, including IL-6, TNF-
, and IL-2, are copiously expressed in the microenvironment of the lymphoid tissues, which harbor the latent viral reservoirs, induction of HIV by this combination of cytokines may in part explain the commonly observed reappearance of detectable
plasma viremia in HIV-infected individuals in whom HAART was discontinued. Moreover,
since it is likely that these infected cells die upon activation of virus and that HAART prevents
spread of virus to adjacent cells, the observation that this combination of cytokines can markedly induce viral replication in this reservoir may have important implications for the activation-mediated diminution of the latent reservoir of HIV in patients receiving HAART.
Key words:
 |
Introduction |
Cytokines are important effector molecules in the initiation and propagation of inflammatory and immune
responses; in addition, certain cytokines mediate a number
of important immunoregulatory functions (1). The role of
cytokines in the pathogenesis of HIV disease has been extensively studied (2). It has been demonstrated by in
vitro experiments that HIV replication in PBMCs of HIV-infected individuals is finely regulated by a variety of endogenous cytokines acting in an autocrine and paracrine
manner (5, 6). Cytokine-rich supernatants derived from
cultures of PBMCs from normal individuals were first
shown to induce the expression of HIV-1 in chronically infected cell lines (7, 8). Subsequently, a variety of individual cytokines, particularly proinflammatory cytokines, were
demonstrated to induce HIV expression either endogenously or when added to acutely or chronically infected
cell cultures (3, 4, 9). Of these, IL-1, IL-6, and TNF-
have been implicated in the pathogenesis of HIV-1 as direct modulators of virus expression (3, 10) and higher
levels of these cytokines have been detected in the sera of
infected individuals; furthermore, secretion of these cytokines is increased in PBMCs of infected individuals (14). For these reasons, selective cytokine inhibitors such as IL-1 receptor antagonist or agents that neutralize TNF-
have
been suggested as potential therapeutic strategies aimed at
the control of viral replication (13, 19).
Recently, a small but detectable reservoir of latently
infected, resting CD4+ T cells has been shown to persist
in patients receiving highly active antiretroviral therapy
(HAART)1 and in whom plasma viremia had fallen to below the level of detectability of commonly used assays (24-
26). The presence of this latent reservoir of HIV is of considerable concern since these cells remain as a potential
source of reactivation of viral replication. In this regard,
these cells reside predominantly in the microenvironment of lymphoid tissue (27), where endogenous cytokine secretion regularly occurs in response to normal antigenic stimuli (2, 28).
In this study, we demonstrate that the in vitro combination of cytokines IL-2, IL-6, and TNF-
has a profound
effect on reactivation of HIV-1 replication in latently infected, resting CD4+ T cells both from antiretroviral naive
patients and from patients who were receiving HAART
and in whom plasma viremia was markedly suppressed, including some patients in whom plasma viremia was below
detectable levels. In vitro HAART prevents the spread of virus in cytokine-induced cultures. These findings may explain the reappearance of plasma viremia in patients in
whom HAART is discontinued due to drug toxicity or
lack of compliance (33). In addition, since cytokines alone
can reactivate HIV-1 replication in latently infected, resting
CD4+ T cells, and since these cells probably die upon reactivation, it is conceivable that a strategy of administration of
cytokines together with HAART might result in a diminution of this reservoir of latently infected cells.
 |
Materials and Methods |
Patient Population.
Six HIV-1-seropositive patients who were
naive to antiretroviral therapy, and seven patients who were receiving HAART (Table 1) were subjected to apheresis in order
to obtain PBMCs according to protocols approved by the National Institute of Allergy and Infectious Diseases and the University of Washington Institutional Review Boards.
Isolation of Resting CD4+ T Cells.
Resting CD4+ T cells were
isolated from peripheral blood of HIV-1-infected individuals using a combination of magnetic bead depletion and fluorescent activated cell sorting techniques as described previously (27).
Micro Coculture Assay.
To determine the frequency of latently
infected, resting CD4+ T cells from patients carrying replication
competent HIV-1, micro coculture assays were carried out as described previously (27).
Cytokines and Cell Cultures.
After isolation of resting CD4+
T cells from HIV-1-infected individuals, cells (2.0-10 × 106)
were incubated with complete medium consisting of RPMI supplemented with 10% FCS, penicillin-streptomycin, and L-glutamine
in a tissue culture plate with the following cytokines: IL-2 (100 U/ml; Boehringer Mannheim, Indianapolis, IN), IL-1
(5 ng/ml;
R&D Systems, Minneapolis, MN), IL-4 (3 ng/ml; R&D Systems), IL-6 (5 ng/ml; R&D Systems), TNF-
(2.5 ng/ml; R&D
Systems), or with the combination of IL-2, IL-6, and TNF-
.
Purified resting CD4+ T cells were also incubated with complete
medium in the absence of any cytokines as a negative control. As
a positive control, the same number of cells were incubated with
anti-CD3 antibody (OKT3) in the presence of 2 × 106 irradiated
PBMCs from HIV-1-seronegative individuals as feeder cells. To
examine the inhibitory role of glucocorticoids in the induction of
HIV-1 replication in latently infected, resting CD4+ T cells by
cytokines, dexamethasone (10
8 M; Calbiochem, La Jolla, CA)
was added to cultures containing the combination of three cytokines or anti-CD3 antibody. Cultures were incubated in a 37°C
CO2 incubator for 9 d, and supernatants from each culture were
removed on days 3, 6, and 9 for determination of HIV-1 p24 by
ELISA (Coulter Corp., Miami, FL). To examine the effects of in
vitro antiretroviral agents on the combination of cytokines or
anti-CD3 induced viral replication, zidovudine (AZT; 4 µM;
Sigma Chemical Co., St. Louis, MO), lamivudine (3TC; 5 µM; gift from Dr. Raymond Schnazi, Emory University, Atlanta,
GA), and the protease inhibitor indinavir (10 µM; Merck, Rahway, NJ) were added to the media.
Flow Cytometric Analysis and Cell Proliferation Assays.
To measure cytokine-induced cellular activation in latently infected, resting CD4+ T cells, flow cytometric analysis of the expression of
activation markers and thymidine incorporation assays were carried out. Resting CD4+ T cells that had been incubated with various cytokines were stained with PE-conjugated anti-CD25
(Becton Dickinson, San Jose, CA) and PE-conjugated anti-HLA-DR antibodies (Becton Dickinson) along with FITC-conjugated
anti-CD4 antibody (Becton Dickinson) 6 d after incubation. On
day 6, [3H]thymidine incorporation was measured in resting
CD4+ T cells that had been incubated with the above cytokines
or with anti-CD3 antibody.
 |
Results |
Cytokine-induced Cellular Activation in Latently Infected,
Resting CD4+ T Cells.
The replication of HIV-1 is intimately associated with the state of cellular activation of susceptible cell populations (2, 28). In this regard, we first investigated the role of individual cytokines or combinations
of cytokines on the activation of highly enriched, resting
CD4+ T cells from HIV-1-seropositive patients by examining the expression of cell surface activation markers
CD25 and HLA-DR. As shown in Table 2, in the absence
of cytokines or any other activating stimuli, purified resting
CD4+ T cells from infected individuals expressed no measurable CD25 or HLA-DR on their cell surfaces. After a 6-d
incubation in vitro, only IL-2 and IL-4 induced slight increases in activation markers on resting CD4+ T cells.
However, the combination of IL-2, IL-6, and TNF-
showed marked increases in CD25 and HLA-DR expression. The induction of cellular activation in purified resting
CD4+ T cells by the combination of three cytokines was
further confirmed by the cellular incorporation of DNA
precursor thymidine (Fig. 1). With the exception of IL-2,
which induced a slight degree of cellular proliferation, no
individual cytokine resulted in active proliferation of resting CD4+ T cells. Cells stimulated with anti-CD3 antibody showed profound cellular activation as judged by
both the expression of activation markers and [3H]thymidine incorporation, confirming that purified resting CD4+
T cells are fully capable of undergoing cellular proliferation.

View larger version (20K):
[in this window]
[in a new window]
|
Fig. 1.
Cytokine-induced cellular proliferation in latently infected,
resting CD4+ T cells. Highly enriched (>99%) resting CD4+ T cells
from one HIV-1-seronegative and two HIV-1-infected individuals were
incubated with the indicated individual cytokines, a combination of cytokines, or anti-CD3 antibody for 6 d, and [3H]thymidine incorporation
by 104 resting CD4+ T cells was measured. A representative set of results
from patient no. 2 is shown.
|
|
Induction of HIV-1 Replication by the Combination of IL-2,
IL-6, and TNF-
in Latently Infected, Resting CD4+ T Cells
from Antiretroviral Drug-naive Patients.
Given the fact that
the combination of IL-2, IL-6, and TNF-
potently activates resting CD4+ T cells as described above, we first examined the inducibility of replication-competent HIV-1 in
latently infected, resting CD4+ T cells from antiretroviral
therapy-naive, HIV-1-seropositive individuals using individual cytokines and combinations of cytokines in vitro.
Despite the fact that highly purified, resting CD4+ T cells
from all patients carried replication-competent HIV-1 with
a frequency determined by micro coculture assay ranging
from 8.1 to 205.8 infectious units per 106 resting CD4+
T cells (Table 1), measurable p24 was not detected in cultures containing neither cytokines nor anti-CD3 antibody
throughout the entire incubation period (Fig. 2). Among
the individual cytokines, only IL-2 had a slight effect on the
induction of HIV-1 expression in latently infected, resting
CD4+ T cells (Fig. 2). However, cultures incubated with
the combination of IL-2, IL-6, and TNF-
had a dramatic
increase in HIV-1 replication. The level of viral production
induced by this cytokine combination was equivalent to
that of cells stimulated with anti-CD3 antibody. When a
combination of three antiretroviral drugs was added to the
cultures incubated with the three cytokine combination or with anti-CD3 antibody, viral replication was completely
suppressed as shown in Fig. 2.

View larger version (32K):
[in this window]
[in a new window]
|
Fig. 2.
Induction of HIV-1 replication by the combination of IL-2, IL-6, and TNF- in latently infected, resting CD4+ T cells from antiretroviral
drug-naive patients. Resting CD4+ T cells from infected patients were isolated and further incubated with no cytokine, individual cytokines as indicated,
the combination of IL-2, IL-6, and TNF- , or anti-CD3 antibody with irradiated PBMCs from HIV-1-seronegative individuals. In addition, cells were
incubated with the combination of IL-2, IL-6, and TNF- or anti-CD3 antibody in the presence of three drugs (AZT, 3TC, and Indinavir; see Materials
and Methods). Supernatants from each culture were removed on days 3, 6, and 9, and HIV-1 p24 was measured by ELISA.
|
|
Induction of HIV-1 Replication by the Combination of IL-2,
IL-6, and TNF-
in Latently Infected, Resting CD4+ T cells
from Patients Receiving HAART.
We and others have recently reported that HIV-1-infected individuals receiving
HAART for prolonged periods of time with no detectable
plasma viremia carry a small number of latently infected, resting CD4+ T cells that produce infectious HIV-1 upon
mitogenic stimulation in vitro (24). In this regard, we
sought to determine whether activation of HIV-1 replication can be achieved by cytokines alone in the absence of a
potent mitogenic stimulus in latently infected, resting
CD4+ T cells from patients who had been receiving
HAART for considerable periods of time and in whom
plasma viremia was markedly suppressed. The frequency of
latently infected, resting CD4+ T cells carrying replication-competent HIV-1 from these patients ranged from 0.5 to
40.1 infectious units per 106 resting CD4+ T cells (Table
1). When purified resting CD4+ T cells from these patients
were incubated with individual cytokines, including IL-2,
no significant HIV-1 replication was detected in the supernatants (Fig. 3). However, the combination of IL-2, IL-6,
and TNF-
effectively induced HIV-1 replication in this population of cells from seven out of seven patients receiving HAART, three of whom (patient nos. 10, 12, and 13) had
no detectable plasma viremia as determined by the ultrasensitive reverse transcriptase PCR assay (Roche Labs., Nutley,
NJ) with a detection limit of 50 copies of HIV-1 RNA per
milliliter of plasma. As in patients receiving no antiretroviral drugs, triple combination of antiretroviral drugs in vitro
completely abolished HIV-1 replication induced by either
the cytokine combination or anti-CD3 stimulation.

View larger version (22K):
[in this window]
[in a new window]
|
Fig. 3.
Induction of HIV-1 replication by the combination of IL-2, IL-6, and TNF- in latently infected, resting CD4+ T cells from patients receiving HAART. Resting CD4+ T cells from infected patients were isolated and further incubated with no cytokine, individual cytokines as indicated,
the combination of IL-2, IL-6, and TNF- , or anti-CD3 antibody with irradiated PBMCs from HIV-1-seronegative individuals. In addition, cells were
incubated with the combination of IL-2, IL-6, and TNF- or anti-CD3 antibody in the presence of three drugs (AZT, 3TC, and Indinavir; see Materials
and Methods). Supernatants from each culture were removed on days 3, 6, and 9, and HIV-1 p24 was measured by ELISA.
|
|
Suppression of HIV-1 Replication in Latently Infected, Resting CD4+ T Cells by Glucocorticoids.
Glucocorticoids, a class
of hormones with broad antiinflammatory and immunoregulatory properties (34), have been shown to block
HIV-1 replication in vitro and in vivo (37, 38). One of the
major effects of glucocorticoids is to inhibit the secretion and effects of cytokines (39). In addition, it has been
shown that glucocorticoids can block nuclear factor
B-
mediated cellular activation in vitro (42). To examine the
inhibitory role of glucocorticoids in the induction of HIV-1
replication in latently infected, resting CD4+ T cells by cytokines, dexamethasone was added to cultures containing the combination of three cytokines or anti-CD3 antibody.
As shown in Fig. 4, cultures containing dexamethasone
markedly inhibited replication of HIV-1 in latently infected, resting CD4+ T cells from antiretroviral drug-naive
patients when cultures were stimulated with either the
combination of IL-2, IL-6, and TNF-
or with anti-CD3
antibody.

View larger version (20K):
[in this window]
[in a new window]
|
Fig. 4.
Suppression of induction of HIV-1 replication in latently infected, resting CD4+ T cells stimulated with the combination of cytokines or anti-CD3 antibody by in vitro glucocorticoids. Resting CD4+ T
cells were incubated with IL-2, IL-6, and TNF- , or with anti-CD3 antibody with irradiated feeders in the presence or absence of dexamethasone (10 8 M). Supernatants from each culture were removed on days 3, 6, and 9, and HIV-1 p24 was measured by ELISA.
|
|
 |
Discussion |
In this study, we have examined the synergistic role of
cytokines in the reactivation of HIV-1 replication in latently infected, resting CD4+ T cells from patients who
were receiving no antiretroviral therapy as well as from patients who were receiving HAART and in whom plasma
viremia was markedly suppressed, and in certain patients even undetectable by the ultrasensitive reverse transcriptase PCR. Despite the fact that certain proinflammatory and
immunoregulatory cytokines have been shown to upregulate the expression of HIV-1 in chronically infected cell
lines and in the PBMCs of infected individuals (3, 10),
it has been unclear what effect they have on latently infected, resting CD4+ T cells. This study clearly demonstrates a synergistic role of the combination of IL-2, IL-6,
and TNF-
in the induction of HIV-1 replication in latently infected, resting CD4+ T cells. The fact that individual cytokines did not induce significant replication of HIV
in these cells, whereas combinations of cytokines were potent inducers, is consistent with previous observations of
the synergistic effects of certain cytokines in the induction of expression of HIV from chronically infected cell lines
(12). HIV-1 replication in latently infected, resting CD4+
T cells induced by the three cytokine combination and
anti-CD3 stimulation was effectively suppressed by dexamethasone at modest concentrations (10
8 M), which agrees
with previous findings that glucocorticoids can block HIV-1
replication by inhibiting the secretion of certain cytokines,
particularly proinflammatory cytokines (39) or by inhibiting nuclear factor
B-mediated cellular activation (42).
The findings in our study suggest that combinations of
cytokines secreted in response to nonspecific stimuli or as a
result of a specific antigenic stimulus could explain at least
in part the reappearance of plasma viremia in patients receiving HAART in whom HIV-1 replication was successfully contained initially but in whom therapy was subsequently interrupted (33). Given the fact that the latently
infected pool of resting CD4+ T cells resides predominantly in lymphoid tissue (27), and since cells situated in
the microenvironment of lymphoid tissue are continually
exposed to the secretion of proinflammatory and immunoregulatory cytokines (43), it is highly likely that these cytokines readily induce HIV replication in latently infected, resting CD4+ T cells in the absence of HAART or when
HAART is ineffective in completely suppressing virus replication (33). The fact that latently infected, resting CD4+
T cells from individuals receiving HAART and in whom
plasma viremia was markedly suppressed, and in certain patients even undetectable, could be readily induced to replicate virus when cells were taken ex vivo and cultured in
the presence of the combination of cytokines is highly consistent with their ability to become reactivated when in
vivo HAART is discontinued. The ability of in vitro
HAART to again suppress cytokine-induced virus replication underscores this observation.
Finally, given the relatively long half-life of these latently
infected, resting CD4+ T cells (24) and the fact that
they are constantly within an environment capable of providing the stimuli for reactivation, it is not unreasonable to
explore strategies aimed at deliberately diminishing the size
of this pool of cells. In this regard, since cytokine-mediated
induction of HIV-1 replication in these cells with subsequent release of virus probably results in death of the cell
(44), and since the presence of HAART in vitro prevents spread of released virus, it is conceivable that in vivo
administration of cytokines together with HAART may
have such an effect.
Address correspondence to Tae-Wook Chun, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bldg. 10, Rm. 6A32, Bethesda, MD 20892. Phone: 301-496-0890; Fax: 301-402-4122; E-mail: twchun{at}nih.gov
We thank Joseph Adelsberger, Randy Stevens, and Dr. Michael Baseler for their help with cell sorting experiments; and Shuying Liu and Julie Metcalf for providing patient laboratory data. We also thank Drs.
Lawrence Corey, M. Michelle Berry, and Jo Ann M. Mican for providing PMBCs from patients.
1.
|
Paul, W.E., and
R.A. Seder.
1994.
Lymphocyte responses
and cytokines.
Cell.
76:
241-251
[Medline].
|
2.
|
Fauci, A.S..
1993.
Multifactorial nature of human immunodeficiency virus disease: implications for therapy.
Science.
262:
1011-1018
[Medline].
|
3.
|
Poli, G., and
A.S. Fauci.
1993.
Cytokine modulation of HIV
expression.
Semin. Immunol.
5:
165-73
[Medline].
|
4.
| Poli, G., and A.S. Fauci. 1995. Role of cytokines in the
pathogenesis of human immunodeficiency virus infection. In
Human Cytokines: Their Role in Disease and Therapy. B.B.
Aggarwal and R.K. Puri, editors. Blackwell Science, Cambridge, MA. 421-449.
|
5.
|
Fauci, A.S..
1996.
Host factors and the pathogenesis of HIV-induced disease.
Nature.
384:
529-534
[Medline].
|
6.
|
Kinter, A.L.,
G. Poli,
L. Fox,
E. Hardy, and
A.S. Fauci.
1995.
HIV replication in IL-2-stimulated peripheral blood mononuclear cells is driven in an autocrine/paracrine manner by
endogenous cytokines.
J. Immunol.
154:
2448-2459
[Abstract/Free Full Text].
|
7.
|
Folks, T.,
D.M. Powell,
M.M. Lightfoote,
S. Benn,
M.A. Martin, and
A.S. Fauci.
1986.
Induction of HTLV-III/LAV
from a nonvirus-producing T-cell line: implications for latency.
Science.
231:
600-602
[Medline].
|
8.
|
Folks, T.,
J. Justement,
A. Kinter,
C. Dinarella, and
A.S. Fauci.
1987.
Cytokine induced expression of HIV-1 in a chronically-infected promocyte cell line.
Science.
238:
800-801
[Medline].
|
9.
| Poli, G., and A.S. Fauci. 1996. Cytokine cascades in HIV infection. In Immunology of HIV Infection. S, Gupta, editor.
Plenum Press, New York. 285-301.
|
10.
|
Osborn, L.,
S. Kunkel, and
G.J. Nabel.
1989.
Tumor necrosis
factor alpha and interleukin 1 stimulate the human immunodeficiency virus enhancer by activation of the nuclear factor
kappa B.
Proc. Natl. Acad. Sci. USA.
86:
2336-2340
[Abstract].
|
11.
|
Kobayashi, N.,
Y. Hamamoto,
Y. Koyanagi,
I.S. Chen, and
N. Yamamoto.
1989.
Effect of interleukin-1 on the augmentation of human immunodeficiency virus gene expression.
Biochem. Biophys. Res. Commun.
165:
715-721
[Medline].
|
12.
|
Poli, G.,
P. Bressler,
A. Kinter,
E. Duh,
W.C. Timmer,
A. Rabson,
J.S. Justement,
S. Stanley, and
A.S. Fauci.
1990.
Interleukin 6 induces human immunodeficiency virus expression in infected monocytic cells alone and in synergy with
tumor necrosis factor alpha by transcriptional and post-transcriptional mechanisms.
J. Exp. Med.
172:
151-158
[Abstract].
|
13.
|
Poli, G.,
A.L. Kinter, and
A.S. Fauci.
1994.
Interleukin 1 induces expression of the human immunodeficiency virus alone
and in synergy with interleukin 6 in chronically infected U1
cells: inhibition of inductive effects by the interleukin 1 receptor antagonist.
Proc. Natl. Acad. Sci. USA.
91:
108-112
[Abstract].
|
14.
|
Belec, L.,
D. Meillet,
A. Hernvann,
G. Gresenguet, and
R. Gherardi.
1994.
Differential elevation of circulating interleukin-1 beta, tumor necrosis factor alpha, and interleukin-6 in
AIDS-associated cachectic states.
Clin. Diagn. Lab. Immunol.
1:
117-120
[Abstract].
|
15.
|
Roux-Lombard, P.,
C. Modoux,
A. Cruchaud, and
J.M. Dayer.
1989.
Purified blood monocytes from HIV 1-infected
patients produce high levels of TNF alpha and IL-1.
Clin. Immunol. Immunopathol.
50:
374-384
[Medline].
|
16.
|
Hober, D.,
A. Haque,
P. Wattre,
G. Beaucaire,
Y. Mouton, and
A. Capron.
1989.
Production of tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1) in patients with
AIDS. Enhanced level of TNF-alpha is related to a higher cytotoxic activity.
Clin. Exp. Immunol.
78:
329-333
[Medline].
|
17.
|
Navikas, V.,
J. Link,
C. Persson,
T. Olsson,
B. Hojeberg,
A. Ljungdahl,
H. Link, and
B. Wahren.
1995.
Increased mRNA
expression of IL-6, IL-10, TNF-alpha, and perforin in blood
mononuclear cells in human HIV infection.
J. Acquir. Immune
Defic. Syndr. Hum. Retrovirol.
9:
484-489
[Medline].
|
18.
|
Trentin, L.,
S. Garbisa,
R. Zambello,
C. Agostini,
C. Caenazzo,
C. Di Francesco,
A. Cipriani,
E. Francavilla, and
G. Semenzato.
1992.
Spontaneous production of interleukin-6
by alveolar macrophages from human immunodeficiency virus type 1-infected patients.
J. Infect. Dis.
166:
731-737
[Medline].
|
19.
|
Ito, M.,
M. Baba,
S. Mori,
K. Hirabayashi,
A. Sato,
S. Shigeta, and
E. De Clercq.
1990.
Tumor necrosis factor antagonizes inhibitory effect of azidothymidine on human immunodeficiency virus (HIV) replication in vitro.
Biochem.
Biophys. Res. Commun
166:
1095-1101
[Medline].
|
20.
|
Le Naour, R.,
H. Raoul,
A. Mabondzo,
Y. Henin,
A. Bousseau, and
D. Dormont.
1994.
Treatment of human monocyte-derived macrophages with a TNF alpha synthesis inhibitor prior to HIV1 infection: consequences on cytokine
production and viral replication.
Res. Virol.
145:
199-207
[Medline].
|
21.
|
Granowitz, E.V.,
B.M. Saget,
M.Z. Wang,
C.A. Dinarello, and
P.R. Skolnik.
1995.
Interleukin 1 induces HIV-1 expression in chronically infected U1 cells: blockade by interleukin
1 receptor antagonist and tumor necrosis factor binding protein type 1.
Mol. Med.
1:
667-677
[Medline].
|
22.
|
Goletti, D.,
A.L. Kinter,
E.C. Hardy,
G. Poli, and
A.S. Fauci.
1996.
Modulation of endogenous IL-1 beta and IL-1 receptor antagonist results in opposing effects on HIV expression
in chronically infected monocytic cells.
J. Immunol.
156:
3501-3508
[Abstract].
|
23.
|
Herbein, G.,
L.J. Montaner, and
S. Gordon.
1996.
Tumor necrosis factor alpha inhibits entry of human immunodeficiency
virus type 1 into primary human macrophages: a selective
role for the 75-kilodalton receptor.
J. Virol.
70:
7388-7397
[Abstract].
|
24.
|
Chun, T.W.,
L. Stuyver,
S.B. Mizell,
L.A. Ehler,
J.A. Mican,
M. Baseler,
A.L. Lloyd,
M.A. Nowak, and
A.S. Fauci.
1997.
Presence of an inducible HIV-1 latent reservoir during highly
active antiretroviral therapy.
Proc. Natl. Acad. Sci. USA.
94:
13193-13197
[Abstract/Free Full Text].
|
25.
|
Finzi, D.,
M. Hermankova,
T. Pierson,
L.M. Carruth,
C. Buck,
R.E. Chaisson,
T.C. Quinn,
K. Chadwick,
J. Margolick,
R. Brookmeyer, et al
.
1997.
Identification of a reservoir for HIV-1 in patients on highly active antiretroviral
therapy.
Science.
278:
1295-300
[Abstract/Free Full Text].
|
26.
|
Wong, J.K.,
M. Hezareh,
H.F. Gunthard,
D.V. Havlir,
C.C. Ignacio,
C.A. Spina, and
D.D. Richman.
1997.
Recovery of
replication-competent HIV despite prolonged suppression of
plasma viremia.
Science.
278:
1291-1295
[Abstract/Free Full Text].
|
27.
|
Chun, T.W.,
L. Carruth,
D. Finzi,
X. Shen,
J.A. DiGiuseppe,
H. Taylor,
M. Hermankova,
K. Chadwick,
J. Margolick,
T.C. Quinn, et al
.
1997.
Quantification of latent tissue reservoirs and total body viral load in HIV-1 infection.
Nature.
387:
183-188
[Medline].
|
28.
|
Pantaleo, G., and
A.S. Fauci.
1995.
New concepts in the immunopathogenesis of HIV infection.
Annu. Rev. Immunol.
13:
487-512
[Medline].
|
29.
|
Stanley, S.,
M.A. Ostrowski,
J.S. Justement,
K. Gantt,
S. Hedayati,
M. Mannix,
K. Roche,
D.J. Schwartzentruber,
C.H. Fox, and
A.S. Fauci.
1996.
Effect of immunization with a
common recall antigen on viral expression in patients infected with human immunodeficiency virus type 1.
N. Engl.
J. Med.
334:
1222-1230
[Abstract/Free Full Text].
|
30.
|
Staprans, S.I.,
B.L. Hamilton,
S.E. Follansbee,
T. Elbeik,
P. Barbosa,
R.M. Grant, and
M.B. Feinberg.
1995.
Activation
of virus replication after vaccination of HIV-1-infected individuals.
J. Exp. Med.
182:
1727-1737
[Abstract].
|
31.
|
O'Brien, W.A.,
K. Grovit-Ferbas,
A. Namazi,
S. Ovcak-Derzic,
H.J. Wang,
J. Park,
C. Yeramian,
S.H. Mao, and
J.A. Zack.
1995.
Human immunodeficiency virus type 1 replication can be increased in peripheral blood of seropositive patients after influenza vaccination.
Blood.
86:
1082-1089
[Abstract/Free Full Text].
|
32.
|
Ostrowski, M.A.,
S.K. Stanley,
J.S. Justement,
K. Gantt,
D. Goletti, and
A.S. Fauci.
1997.
Increased in vitro tetanus-induced
production of HIV type 1 following in vivo immunization of
HIV type 1-infected individuals with tetanus toxoid.
AIDS
Res. Hum. Retroviruses.
13:
473-480
[Medline].
|
33.
|
de Jong, M.D.,
R.J. de Boer,
F. de Wolf,
N.A. Foudraine,
C.A. Boucher,
J. Goudsmit, and
J.M. Lange.
1997.
Overshoot of HIV-1 viraemia after early discontinuation of antiretroviral treatment.
AIDS (London).
11:
F79-84
.
|
34.
|
Parrillo, J.E., and
A.S. Fauci.
1979.
Mechanisms of glucocorticoid action on immune processes.
Annu. Rev. Pharmacol.
Toxicol.
19:
179-201
[Medline].
|
35.
|
Zimmerman, G.A.,
S.M. Prescott, and
T.M. McIntyre.
1992.
Endothelial cell interactions with granulocytes: tethering and
signaling molecules.
Immunol. Today.
13:
93-100
[Medline].
|
36.
|
Sternberg, E.M.,
G.P. Chrousos,
R.L. Wilder, and
P.W. Gold.
1992.
The stress response and the regulation of inflammatory disease.
Ann. Intern. Med.
117:
854-866
[Medline].
|
37.
|
Bressler, P.,
G. Poli,
J.S. Justement,
P. Biswas, and
A.S. Fauci.
1993.
Glucocorticoids synergize with tumor necrosis
factor alpha in the induction of HIV expression from a
chronically infected promonocytic cell line.
AIDS Res. Hum.
Retroviruses.
9:
547-551
[Medline].
|
38.
|
Biswas, P.,
G. Poli,
J.M. Orenstein, and
A.S. Fauci.
1994.
Cytokine-mediated induction of human immunodeficiency
virus (HIV) expression and cell death in chronically infected
U1 cells: do tumor necrosis factor alpha and gamma interferon selectively kill HIV-infected cells?
J. Virol.
68:
2598-2604
[Abstract].
|
39.
| Schleimer, R.P. 1993. An overview of glucocorticoid anti-inflammatory actions. Eur. J. Clin. Pharmacol. 45(Suppl. 1):S3-7.
|
40.
|
Almawi, W.Y.,
H.N. Beyhum,
A.A. Rahme, and
M.J. Rieder.
1996.
Regulation of cytokine and cytokine receptor
expression by glucocorticoids.
J. Leukocyte Biol.
60:
563-572
[Abstract].
|
41.
|
Schwiebert, L.M.,
L.A. Beck,
C. Stellato,
C.A. Bickel,
B.S. Bochner,
R.P. Schleimer, and
L.A. Schwiebert.
1996.
Glucocorticosteroid inhibition of cytokine production: relevance
to antiallergic actions.
J. Allergy Clin. Immunol.
97:
143-152
[Medline].
|
42.
|
Scheinman, R.I.,
P.C. Cogswell,
A.K. Lofquist, and
A.S. Baldwin Jr..
1995.
Role of transcriptional activation of I
kappa B alpha in mediation of immunosuppression by glucocorticoids.
Science.
270:
283-286
[Abstract].
|
43.
|
Graziosi, C.,
G. Pantaleo,
K.R. Gantt,
J.P. Fortin,
J.F. Demarest,
O.J. Cohen,
R.P. Sekaly, and
A.S. Fauci.
1994.
Lack
of evidence for the dichotomy of TH1 and TH2 predominance in HIV-infected individuals.
Science.
265:
248-252
[Medline].
|
44.
|
Ho, D.D.,
A.U. Neumann,
A.S. Perelson,
W. Chen,
J.M. Leonard, and
M. Markowitz.
1995.
Rapid turnover of plasma
virions and CD4 lymphocytes in HIV-1 infection.
Nature.
373:
123-126
[Medline].
|
45.
|
Wei, X.,
S.K. Ghosh,
M.E. Taylor,
V.A. Johnson,
E.A. Emini,
P. Deutsch,
J.D. Lifson,
S. Bonhoeffer,
M.A. Nowak,
B.H. Hahn, et al
.
1995.
Viral dynamics in human immunodeficiency virus type 1 infection.
Nature.
373:
117-122
[Medline].
|
46.
|
Perelson, A.S.,
A.U. Neumann,
M. Markowitz,
J.M. Leonard, and
D.D. Ho.
1996.
HIV-1 dynamics in vivo: virion
clearance rate, infected cell life-span, and viral generation
time.
Science.
271:
1582-1586
[Abstract].
|
47.
|
Myers, L.E.,
L.J. McQuay, and
F.B. Hollinger.
1994.
Dilution assay statistics.
J. Clin. Microbiol.
32:
732-739
[Abstract].
|