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Animal Model |
From the Division of Viral Pathogenesis,*
Department of
Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School,
Boston, Massachusetts; the Division of Comparative
Pathology,
New England Regional Primate
Research Center, Harvard Medical School, Southborough, Massachusetts;
the Department of Biochemistry and Molecular
Biology,
University of Hamburg, Hamburg,
Germany; the Bernhard-Nocht-Institute for Tropical
Medicine,§
Hamburg, Germany;
Centocor,¶ Malvern, Pennsylvania, and the
Institute of Immunology,||
Technical University of
Dresden, Dresden, Germany
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Numerous experimental approaches have been used to study the role of CD8+ cell-mediated immunity in the control of infections. Studies demonstrating the importance of cellular immunity in various viral infections have been performed by adoptive transfer of lymphocytes in syngeneic mice.1,2 Genetic knockout mice in which the CD8 or ß2 microglobulin genes have been disrupted have been useful for defining the immunopathogenic role of cytotoxic T lymphocytes (CTL) in specific infectious agents.3,4 Finally, rodents depleted of CD8+ lymphocytes by administration of CD8-specific monoclonal antibodies have been useful in determining the role of CTL in controlling pathogens.5 However, these approaches have been used only in small laboratory animals. The immune responses to many human pathogens cannot be studied in rodent models.
Nonhuman primates provide unique models for a number of important infectious diseases. These models have been instrumental in characterizing disease pathogenesis and in testing immunization approaches to prevent infection by hepatitis viruses, herpes viruses, and HIV.6,7 However, the inbred or gene-disrupted nonhuman primates that would be needed for studies of cellular immunity do not exist. Previous attempts to deplete T cell subpopulations in nonhuman primates have had only limited success. Administration of monoclonal antibodies targeting the CD8 molecule have produced only transient and incomplete depletion of CD8-bearing lymphocytes from blood.8,9 More importantly, these approaches failed to deplete this cell subset consistently from secondary lymphoid organs.
In this report, we describe a rhesus monkey model of CD8+ lymphocyte depletion using a mouse-human chimeric monoclonal antibody. Intravenous administration of this antibody resulted in nearly total depletion of CD8+ lymphocytes from the blood and lymph nodes for 2–6 weeks. However, CD4 cell-mediated immune responses remained intact and all monkeys were capable of mounting humoral immune responses.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The cMT-807 mAb was prepared as described
previously.10
The heavy and light chain variable region
genes were isolated from the murine M-T807 hybridoma11
and
ligated to the human 
1 heavy chain and 
light chain genes,
respectively, in separate expression plasmids and transfected into
SP2/0-AG14 cells. The secreted mouse-human chimeric mAb was purified
using protein A affinity chromatography as previously
described.10
An isotype-matched mouse-human chimeric monoclonal antibody (chimeric 1129) directed against respiratory syncytial virus (MedImmune, Inc., Gaithersburg, MD) was used as a control monoclonal antibody. The CHO DG44 cell line, which was stably transfected with the plasmid that codes for this chimeric monoclonal antibody, was grown in Minimum Essential Medium Alpha without ribonucleosides or deoxyribonucleosides and supplemented with fetal bovine serum, glutamine, and methotrexate. Secreted chimeric antibody was routinely purified using a protein G column and concentrated in phosphate-buffered saline (PBS).
In Vitro Proliferation of Antigen-Specific CTL
To evaluate the effect of the anti-CD8 antibody cM-T807 on the proliferation of antigen-specific CD8+ T cells, we used the simian immunodeficiency virus of macaques (SIVmac) model of infection, where viral peptides and rhesus monkey major histocompatibility complex (MHC) class I alleles capable of presenting these peptides have been defined.12 Peripheral blood lymphocytes (PBL) were obtained by density gradient centrifugation from 3 monkeys chronically infected with SIVmac expressing the MHC class I allele Mamu A*01. PBL were then cultured for 3 days at 3 x 106 cells/ml in the presence of 1 µg/ml of the 9-mer SIVmac Gag peptide p11C, C-M (CTPYDINQM), and either 20 µg/ml cM-T807 or control monoclonal antibody. Cells were then maintained an additional 7 days in medium supplemented with recombinant interleukin-2 (IL-2) (20 U/ml) and either cM-T807 or control antibody (20 µg/ml). To quantitate expansion of SIVmac peptide-specific CD8+ T cells, the cells were washed and stained with anti-rhesus monkey CD3 (FN-18; gift of David M. Neville, Jr., National Institutes of Health, Bethesda, MD) directly coupled to APC and PE-coupled tetrameric complexes of Mamu-A*01/p11C, C-M as described previously.13,14 The percentage of T cells binding tetramer was then evaluated by flow cytometry.
In Vitro Lysis of Antigen-Expressing Target Cells
To evaluate the effect of cM-T807 on the lytic functional activity of CD8+ T cells, SIVmac-specific lysis of autologous target cells was performed as previously described12 in the presence of either cM-T807 or control monoclonal antibody. Briefly, PBL were generated from SIVmac-infected rhesus monkeys by nonspecific stimulation with Con A (5 µg/ml) (Sigma Chemical Co., St. Louis, MO) or SIV Gag peptide p11C, C-M for 3 days and then maintained in IL-2-supplemented medium for an additional 8 days. Autologous B lymphoblastoid cell lines (B-LCL), which served as targets, were incubated with 50 µg/ml 12-mer peptide p11C (EGCTPYDINQML) or a negative control peptide p11B (ALSEGCTPYDIN) for 90 minutes during labeling with Na251CrO4 (ICN Pharmaceuticals, Inc., Costa Mesa, CA). Effector lymphocytes were cultured in duplicate using U-bottom microtiter plates with 104 target B-LCL at different effector-to-target cell ratios in the presence of either 20 µg/ml cM-T807 or control monoclonal antibody. Plates were incubated in a humidified incubator at 37°C for 4 hours. Specific release was calculated as [(experimental release-spontaneous release)/(maximum release-spontaneous release)] x 100. Spontaneous release was <20% of maximal release with detergent (1% Triton X-100, Sigma Chemical) in all assays.
Complement-Mediated Lysis
Because there was no control antibody available that would cross-react with the rhesus monkey CD8 molecule and show significant complement activation, we used human PBL as targets. PBL from three healthy human donors were isolated by density gradient centrifugation, stained for 20 minutes with anti-CD3-APC (UCHT1, Beckman Coulter, Inc., Miami, FL) and anti-CD4-FITC (OKT4, Ortho Diagnostics, Raritan, NJ), and washed twice. These two mAbs did not show complement activation. The cells were incubated with cM-T807, another monoclonal anti-CD8 antibody (ASH, Biodesign International, Kennebunk, ME), or control monoclonal antibody at 20 µg/ml for 30 minutes on ice. The cells were washed twice and incubated with normal human serum as source of complement at a final concentration of 1:2 for 2 hours at 37°C. The cells were washed once with ice-cold PBS and incubated for 5 minutes with propidium iodide (PI) (50 µg/ml) on ice. The percentage of CD3+4- T cells (equivalent to CD3+8+ T cells) that were lysed and, therefore, stained with PI was determined by flow cytometry.
Antibody Administration to Animals
Rhesus monkeys (Macaca mulatta) were administered cM-T807 or control monoclonal antibody by intravenous injection. For optimal depletion of the monkeys' CD8+ lymphocytes, 3–5 mg/kg of cM-T807 or control antibody was administered three times (days 0, 4, and 7). For all monoclonal antibody administration and biopsy procedures, animals were anesthetized with ketamine HCl.
All animals were maintained in accordance with the guidelines of the Committee on Animals for the Harvard Medical School and the Guide for the Care and Use of Laboratory Animals (National Research Council, Washington, DC, National Academic Press, 1996).
Purification of Cobra Venom Factor (CVF) and Administration to Animals
CVF was purified from the venom of the species Naja naja by sequential column chromatography15 and was shown to be free of endotoxin using the E-TOXATE reagent (Sigma Chemical) (data not shown). Intravenous administration of CVF to rhesus monkeys to consume complement was performed as previously described.16 The first dose of CVF (200 µg/kg body weight) was administered 1 day before administration of cM-T807. The second dose of CVF (100 µg/kg body weight) was administered immediately before cM-T807 administration (5 mg/kg body weight). Two additional administrations of CVF (100 µg/ml) were performed 2 and 4 days after administration of cM-T807. The serum complement hemolytic activity was evaluated by CH50 assay using antibody-sensitized sheep erythrocytes (Sigma Chemical) as targets as described.17
Immunophenotyping of PBL and Lymph Node Cells
Lymphocytes in peripheral blood were immunophenotyped using EDTA-anticoagulated blood specimens in a whole blood lysis technique. Lymph node lymphocyte suspensions were obtained by gently teasing peripheral lymph node specimens that had been obtained by excisional biopsy. Cells in lymph node cell suspension were adjusted to 106/ml in RPMI 1640/10% fetal bovine serum. Fluorochrome-conjugated antibodies were incubated with 100 µl of whole blood or lymph node cell suspension for 20 minutes at room temperature. Antibodies used were anti-CD3(FN18)-APC, anti-CD4-FITC (OKT4, Ortho Diagnostic Systems), anti-CD8-PE (DK25, Dako, Inc., Carpenteria, CA), and anti-CD20-ECD (B1, Beckman Coulter). Erythrocytes were lysed using a ImmunoPrep Reagent System and a Q-Prep Workstation (Beckman Coulter). To reduce the background level of staining, the ImmunoPrep procedure was modified and lysed samples were washed with 1.0 ml PBS, centrifuged for 3 minutes at 300 x g, and fixed in PBS/1% formalin. Specimens were routinely analyzed for 3-color immunofluorescence using a manually determined light scattergate to gate lymphocytes. Absolute lymphocyte counts on blood specimens were obtained using a T540 Hematology Analyzer (Beckman Coulter).
To determine the extent to which cM-T807 would interfere with binding of the anti-CD8 monoclonal antibody used to detect CD8+ lymphocytes by flow cytometry, we incubated PBL after Ficoll gradient centrifugation with saturating amounts (20 µg/ml) of cM-T807 for 30 minutes on ice. PBL were then stained with anti-CD8-PE and analyzed as described above. The mean CD8-PE fluorescence on the cM-T807-pretreated T lymphocytes was compared to the mean fluorescence on T lymphocytes that were not pretreated.
Delayed-Type Hypersensitivity (DTH) in CD8+ Lymphocyte-Depleted Monkeys
To sensitize rhesus monkeys for later assessment of cutaneous DTH responses, 2 monkeys were immunized intramuscularly with 0.5 ml of tetanus toxoid (Tetanus Toxoid, USP, adsorbed, Connaught Labs, Seattle, WA). Two weeks after immunization, 0.1 ml of tetanus toxoid (Tetanus Toxoid, USP, plain, Connaught Labs) was injected intradermally. At 3 days after intradermal injection of tetanus toxoid, a 6-mm full-thickness punch biopsy of skin was taken at the injection site. For CD8+ lymphocyte depletion, the monkeys received 3 administrations of cM-T807 as described above. Eleven days after initiation of CD8+ lymphocyte depletion the monkeys received another intradermal injection of tetanus toxoid. Three days after injection a skin biopsy was taken as described above. Two weeks after reappearance of CD8+ lymphocytes the monkeys received as a control an intradermal injection of saline and skin biopsies were taken 3 days later as described above. Another 2 weeks later, the monkeys received a third intradermal injection of tetanus toxoid and the final skin biopsy was taken.
Anti-Chimeric Monoclonal Antibody Responses
Antibody responses in monkeys directed against cM-T807 or the control monoclonal antibody were measured by enzyme-linked immunosorbent assay. Chimeric monoclonal antibodies were diluted in PBS (10 µg/ml) and plated in 96-well microtiter plates at 100 µl/well overnight at 4°C. Wells were washed and blocked with PBS/1% nonfat dry milk/2% fetal bovine serum. Test plasma specimens were serially diluted in PBS/1% nonfat dry milk. Aliquots (50 µl) were added to blocked wells, incubated for 2 hours at 37°C, and then washed. Binding of monkey Ig to chimeric monoclonal antibodies was detected using a rhesus monkey IgG-specific mouse monoclonal antibody (B3, kindly provided by Ronald C. Kennedy), followed by horseradish peroxidase-conjugated anti-mouse IgG. Binding of conjugated antibody was detected using tetramethylbenzidine substrate. Endpoint dilutions were determined as optical density reading >2 SD over background.
Histology and Immunohistochemistry
Skin biopsy specimens were bisected. One half of each specimen was fixed in 10% neutral buffered formalin and routinely processed for histological examination and the other half embedded in OCT (Miles Scientific, Naperville, IL), snap-frozen, and kept at -70°C until immunohistochemistry was performed. Routine histological examination of skin was performed on formalin-fixed tissues embedded in paraffin and stained with hematoxylin and eosin.
Immunohistochemical examination of T cell subsets in skin was performed as previously described.18 Briefly, skin biopsies were snap-frozen, sectioned on a cryostat, and then fixed in ice-cold acetone for 10 minutes. To visualize CD8+ lymphocytes, sections were incubated with the first antibody (anti-CD8, DK25, Dako), the secondary antibody conjugated to biotin, and then an avidin-biotin alkaline phosphatase complex (Vector Labs, Burlingame, CA) with Vector Red as the chromogen. To visualize CD4+ lymphocytes, the staining procedure was repeated using an anti-CD4 primary antibody (NuTh/1, provided by Yokoyama and Matsuo, Nichirei Research Institute, Tokyo) and Vector Blue as the chromogen. Control procedures included omission of the primary antibody and substitution of an isotype-matched irrelevant antibody.
Lymph node biopsy specimens were cut into three portions. One portion was fixed in 10% neutral buffered formalin and routinely processed for histological examination and a second portion was embedded in OCT, snap-frozen, and kept at -70°C until immunohistochemistry was performed. The third portion was used for preparation of single cells for flow cytometric evaluation of lymphocyte subsets. Routine histological examination of lymph nodes was performed on formalin-fixed tissues embedded in paraffin and stained with hematoxylin and eosin or Giemsa stain.
Immunohistochemical identification of CD8+ lymphocytes in lymph nodes was performed on snap-frozen lymph node biopsy specimens that were sectioned (6 µm) on a cryostat and fixed in 2% paraformaldehyde at room temperature for 15 minutes. Sections were rinsed in PBS and incubated with a cocktail of anti-CD8 antibodies (Leu-2a, Becton Dickinson, Heidelberg, Germany and C8/144B, Dakopatts, Hamburg, Germany) or with a cocktail of anti-CD4 antibodies (Leu-3a, Becton Dickinson, and NCL CD4-IF6, Novocastra Laboratories Ltd., Newcastle-on-Tyne, UK) or anti-CD20 antibody (Dako Diagnostika GmbH, Hamburg, Germany). Binding of the primary antibodies was visualized by the alkaline phosphatase anti-alkaline phosphatase technique using New Fuchsin as the chromogen. Sections were counterstained with hematoxylin and mounted.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Because the CD8 molecule is crucial to CTL
function,19
we determined the in vitro effect
of cM-T807 on the effector function of CD8+ T cells. To accomplish
this, we made use of the simian immunodeficiency virus of macaques
(SIVmac) infection model in which SIVmac CTL epitope peptides and
restricting rhesus monkey MHC class I molecules have been
defined.7
However, it was first necessary to determine
whether pretreatment of PBL with cM-T807 would interfere with the
binding of the anti-CD8 antibody used for flow cytometric detection of
CD8+ lymphocytes. As shown in Figure 1A
,
pretreatment of PBL with saturating concentrations with cM-T807
resulted in a one-half log decrease in the intensity of CD8-PE
fluorescence as compared to untreated PBL. However, T cells pretreated
with cM-T807 stained positively with anti-CD8-PE with fluorescence
intensity >1 log brighter than background staining, assuring that CD8+
lymphocyte could be detected readily in the presence of the chimeric
anti-CD8 antibody.
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.
We next wished to determine whether cM-T807 would interfere with the
ability of CD8+ T cells to lyse target cells following antigen-specific
MHC class I-restricted recognition. Effector cells expanded in
vitro by either antigen-specific or nonspecific stimulation were
incubated with autologous B-LCL target cells expressing the SIVmac Gag
CTL epitope peptide. The addition of cM-T807 resulted in a decrease,
but not a total inhibition, of target cell lysis using effector cells
that had been expanded by either nonspecific or antigen-specific
stimulation using the SIV Gag peptide p11C (Figure 1C)
.
Finally, we wished to determine whether cM-T807 could affect CD8+
lymphocyte function and viability through complement-mediated lysis. To
accomplish this, we incubated human PBL with cM-T807, a control
monoclonal antibody, or another anti-CD8 antibody (ASH; IgM-isotype)
with known lytic activity. Lysis of CD8+ T cells was determined by PI
uptake in the CD3+4- T cell subset. In contrast to the anti-CD8
antibody ASH, cM-T807 showed only a low complement-mediated lysis of
CD4- T cells, similar to that seen in control monoclonal
antibody-treated cells (Figure 1D)
.
In Vivo Administration of cM-T807 to Rhesus Monkeys
To determine the effect of cM-T807 in vivo, we
administered 3–5 mg/kg body weight of the anti-CD8 antibody or a
control monoclonal antibody intravenously to 2-year-old juvenile rhesus
monkeys 3 times over a 7-day period. cM-T807 induced an immediate
depletion of CD8+ lymphocytes in peripheral blood (up to 99%) in the 2
cM-T807-treated monkeys. This treatment resulted in elimination of both
CD8+ T cells (CD3+8+) and CD8+ NK cells (CD3-8+). CD8+ T cells (Figure 2A)
and CD8+ NK cells (data not shown)
first reappeared in these monkeys 14 days after the first injection. A
significant (80–100%) reduction in percentage of CD8+ T cells in
lymph nodes was also observed (Figures 2B, 3A, and 3B)
.
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The absolute numbers of circulating CD4+ T cells and B cells did not
change during this treatment. Similarly, in the lymph nodes of
cM-T807-treated monkeys, the number and distribution of CD4+
lymphocytes or CD20+ B cells did not differ from that seen in control
antibody-treated monkeys (data not shown). Studies in
humans20
and monkeys21
have suggested that
the duration of lymphocyte depletion may be related to the
age-dependent regenerative function of the thymus. Therefore, we
evaluated the CD8 lymphocyte-depleting efficacy of cM-T807 in mature
animals (>5 years of age). Indeed, we noted a longer duration of
depletion of CD8+ lymphocytes from blood and lymph nodes in more mature
animals, persisting 21–40 days after the first injection of cM-T807
(Figure 2C and D)
. Control monoclonal antibody-treatment resulted in no
change of CD8+ T cells in peripheral blood or lymph nodes (Figure 2, E and F)
.
Mechanism of Depletion Is Not Solely Complement-Dependent
Several mechanisms may contribute to the lymphocyte-depleting
effect of a mAb in vivo. Complement proteins and their
activation products may play a major role in this process. Although our
in vitro results suggested that cM-T807 was a poor activator
of complement, we directly assessed the role of complement proteins in
the cM-T807-mediated depletion of CD8+ lymphocytes in vivo.
Administration of CVF leads to a significant reduction of the hemolytic
activity of complement by activation of the alternative
pathway.22
CVF treatment can be used to deplete complement
in vivo in a variety of animal species including rhesus
monkeys.16
To determine whether cM-T807 could deplete CD8+
lymphocytes in monkeys with significantly reduced hemolytic activity of
complement, CVF was administered 1 day before and on days 0, 2, and 4
after cM-T807-administration (Figure 4A)
.
This treatment reduced the hemolytic activity to <5% of pretreatment
levels for 8 days. Despite reduction in the complement activity, we
still observed a 50–80% reduction of CD8+ T cells during the first 7
days following cM-T807 administration. It appeared, however, that the
CD8+ lymphocyte depletion was less efficient in the complement-depleted
monkey as compared to the control monkey that received cM-T807 but not
CVF (Figure 4B)
. These results suggest that complement-independent
mechanisms are primarily responsible for the cM-T807-induced CD8+
lymphocyte depletion in vivo.
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To determine how administration of cM-T807 and subsequent CD8+
lymphocyte depletion affects other immune responses, we assessed
cutaneous DTH reactions in monkeys that were CD8+ lymphocyte-depleted.
Monkeys previously sensitized to tetanus toxoid received an intradermal
injection of tetanus toxoid after the final administration of cM-T807.
Cellular infiltration into the skin at the site of tetanus toxoid
challenge was determined by histological examination of skin biopsies
taken 3 days after antigen was injected. Superficial dermal
perivascular mononuclear cell infiltration was accompanied by variable
numbers of eosinophils.23
As illustrated in Figure 3
,
cellular infiltrates typical of a DTH reaction were evident before CD8+
lymphocyte depletion (Figure 3C)
, during CD8+ lymphocyte depletion
(Figure 3D)
, and after reappearance of CD8+ lymphocytes (Figure 3F)
,
but not following saline injections (Figure 3E)
. Immunophenotyping of
the infiltrating mononuclear cells showed a mixture of CD4+ and CD8+
cells before CD8+ lymphocyte depletion (Figure 3G)
and after
reappearance of CD8+ lymphocytes (Figure 3I)
. However, during CD8+
lymphocyte depletion, only CD4+ lymphocytes were present at the site of
the DTH reaction (Figure 3H)
. These results confirmed that no CD8+
lymphocytes capable of contributing to the DTH reaction remained in the
cM-T807-treated monkeys. Furthermore, inflammatory responses mediated
by CD4+ lymphocytes remained intact during the period of CD8+
lymphocyte depletion.
Humoral Immune Responses in CD8+ Lymphocyte-Depleted Monkeys
To determine the ability of CD8+ lymphocyte-depleted monkeys to
mount humoral immune responses and to assess the antigenicity of
mouse-human chimeric monoclonal antibodies in the treated monkeys, we
measured the generation of IgG responses specific for the administered
chimeric monoclonal antibodies. As shown in Figure 5
, monkeys that received either control
or cM-T807 monoclonal antibodies developed IgG antibody responses that
recognized the chimeric monoclonal antibody by 3 weeks after the first
treatment. Titers of anti-chimeric IgG in control monoclonal
antibody-treated monkeys were similar to those measured in monkeys that
received cM-T807.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Both CD4+ and CD8+ lymphocytes are observed in the DTH reaction in other animal models but the CD4+ lymphocytes appear to be the predominant effector cells.24-26 Before treatment with the anti-CD8 monoclonal antibody, both CD4+ and CD8+ lymphocytes were present in the DTH infiltrate of the monkeys. During CD8+ lymphocyte depletion, however, the cellular infiltrate was comprised entirely of CD4+ lymphocytes. These findings confirmed the competence of CD4+ T cells. Furthermore, all monkeys treated with the anti-CD8 monoclonal antibody developed antibody responses against the administered chimeric immunoglobulin, indicating that humoral immune responsiveness was preserved.
The mechanism by which cM-T807 mediates depletion of CD8+ lymphocytes is unclear. Results from in vitro studies and observations in the complement-depleted monkey suggested that mechanisms independent of the lytic activity of complement played a substantial role in this process. However, complement components of the classical pathway, such as C1 and C4, not consumed during CVF treatment could potentially contribute to the cell depletion in vivo. Alternatively, Fc receptor-mediated interactions between cM-T807-coated CD8+ lymphocytes and granulocytes or macrophages may also be involved in the cell depletion.
The duration of CD8+ lymphocyte depletion varied among monkeys. Thymectomy has been shown to slow the rate of lymphocyte repopulation following mAb-mediated depletion in mice.27 Similarly, a delay in lymphocyte repopulation has been seen after bone marrow transplantation in adults as compared to children.28 Monkeys experimentally depleted of T cells showed age-related differences in the rates of lymphocyte repopulation.21 Therefore, we reasoned that CD8+ lymphocyte depletion may persist for a longer period of time in older monkeys. In fact, lymphocyte depletion persisted in monkeys >5 years old for a longer period than in 2-year-old monkeys. Only 2 weeks of complete CD8+ lymphocyte depletion was achieved in juvenile monkeys. However, in 2 of 4 older monkeys, CD8+ lymphocytes reappeared only after 6 weeks. This duration of cell depletion should be sufficient to assess the role of CD8+ lymphocytes in an experimental setting.
This nonhuman primate model of CD8+ lymphocyte depletion will be extremely useful in clarifying the immune control mechanisms in diseases that cannot be studied in other animal models. The method described here will also have particular relevance in defining the immune correlates of vaccine protection. For example, the use of the live, attenuated nonhuman primate lentiviruses have proven to be one of the most effective vaccine approaches against challenge infection with a pathogenic SIV.29 This nonhuman primate model of CD8+ lymphocyte depletion will allow the determination of the correlates of protective immunity in the live, attenuated vaccines as well as in other immunization strategies.
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Acknowledgements |
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Footnotes |
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Supported by DHHS Public Health Service grants RR-13150 and RR-00168 and by the German Ministry of Education and Research (BMBF 01 K1–9714 6) (to P. R. and K. T.-R.) and German Ministry of Education and Research AIDS Program (to J. E. S.).
Accepted for publication February 25, 1999.
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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J. D. Lifson, J. L. Rossio, M. Piatak Jr., T. Parks, L. Li, R. Kiser, V. Coalter, B. Fisher, B. M. Flynn, S. Czajak, et al. Role of CD8+ Lymphocytes in Control of Simian Immunodeficiency Virus Infection and Resistance to Rechallenge after Transient Early Antiretroviral Treatment J. Virol., November 1, 2001; 75(21): 10187 - 10199. [Abstract] [Full Text] [PDF]
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D. H. Chung, I. M. Belyakov, M. A. Derby, J. Wang, L. F. Boyd, J. A. Berzofsky, and D. H. Margulies Competitive Inhibition In Vivo and Skewing of the T Cell Repertoire of Antigen-Specific CTL Priming by an Anti-Peptide-MHC Monoclonal Antibody J. Immunol., July 15, 2001; 167(2): 699 - 707. [Abstract] [Full Text] [PDF]
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