| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Deptartment of Immunology, Max Planck Institute for Infection Biology, Berlin, Germany
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
following in vitro HKL stimulation. HKL/anti-CD40
vaccination elicited robust protection against subsequent
Listeria challenge. Approximately 1000-fold fewer
bacteria were detected in the liver and spleen of vaccinated mice, and
vaccinated mice were also able to resist a normally lethal
Listeria challenge. CD40-mediated adjuvant activity
required endogenous IL-12 at the time of vaccination, and protection
was mediated by both CD8+ and CD4+ T cells.
Thus, CD40 signaling can deliver potent adjuvant activity for
vaccination against intracellular pathogens and is particularly
effective for pathogens requiring both CD4+ and
CD8+ T cells for effective control. |
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Listeria monocytogenes is a Gram-positive facultative intracellular bacterium that has been used extensively for studying cell-mediated immunity against intracellular bacteria (reviewed in Ref. 2). L. monocytogenes causes an acute infection in mice characterized by early activation of macrophages, neutrophils, and NK cells. Subsequently, CD4+ and CD8+ T cells are activated, and these cells are required for sterile clearance of L. monocytogenes (3). Infection with a sublethal dose of L. monocytogenes induces potent T cell-mediated protection against subsequent infection. In contrast, immunization of mice with nonviable Listerial Ag preparations induces very limited immunity. Indeed, most studies have found that immunization with heat-killed L. monocytogenes (HKL)2 elicits no protection against subsequent Listeria challenge (4, 5, 6). An exception was reported by Szalay et al., (7) who described some protection against Listeria using an unconventional HKL immunization protocol.
CD40, a member of the TNFR family, was initially characterized as a B
cell surface Ag critically involved in T cell-dependent humoral immune
responses. It is now known to be expressed on a wide range of cell
types, including APCs such as monocytes/macrophages and dendritic cells
(DCs) (8). CD40 signaling in APCs leads to a wide range of
phenotypic changes, including up-regulation of adhesion and
costimulatory molecules such as CD80/CD86 and ICAM-1, as well as
induction or increased expression of chemokines and cytokines such as
IL-12, IL-18, EBI1-ligand chemokine and macrophage inflammatory
protein-1
(9, 10, 11, 12, 13). The end result of these
changes is to markedly enhance T cell priming and to favor the
generation of Th1 cells. The effect of these changes can be observed in
vivo using agonistic anti-CD40 mAb. Anti-CD40 mAb can convert the
characteristic Th2 response in BALB/c mice infected with
Leishmania major to a protective Th1 response
(14), and CD8+ T cell responses to
normally nonimmunogenic tumor cells (15) or tolerogenic
peptides (16) can be induced using anti-CD40
mAb.
We hypothesized that a nonimmunogenic, nonviable L. monocytogenes preparation could be converted to an immunogenic vaccine by concurrent delivery of agonistic anti-CD40 mAb. Immunization of mice with HKL together with anti-CD40 mAb treatment induced a strong Th1 and CD8+ T cell response, and the mice were protected against subsequent challenge with a normally lethal dose of L. monocytogenes. Our results indicate that directly targeting CD40 is a promising approach for the development of novel subunit vaccines, particularly for those pathogens that require both CD4+ and CD8+ T cells for effective control.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
C57BL/6 mice were raised under specific pathogen-free conditions at the Bundesinstitut für gesundheitlichen Verbraucherschutz und Veterinärmedizin (Berlin, Germany) and used when they were between 6 and 10 wk of age. All mouse experiments were performed in accordance with German and institutional animal care guidelines.
Bacteria
L. monocytogenes (strain EGD) was grown overnight in
tryptic soy broth. Wild-type Salmonella typhimurium (strain
SL1344) was grown overnight in Luria-Bertani medium.
Salmonella and Listeria stocks were stored at
-80°C. For preparation of HKL and heat-killed S.
typhimurium (HKS), bacteria were washed twice in LPS-free PBS
(Biochrom, Berlin, Germany) and resuspended at
1010 HKL/ml, followed by a 2-h incubation at
60°C. Effective bacterial killing was confirmed by incubating a
200-µl aliquot in tryptic soy broth overnight at 37°C.
Antibodies
The following Abs were used: anti-CD40 (clone IC10, rat IgG;
(17)), anti-IL-12 (clone C17.8; (18)),
anti-CD4 (clone YTS191; (19)), anti-CD8 (clone
YTS169; (19), anti-Fc II/III (clone 2.4G2),
anti-IL-4 (clones BVD4-1D11 and BVD6-24G2) and anti-IFN-
(clones XMG1.2 and R4-6A2). Rat IgG prepared from naive mouse serum
(Sigma, St. Louis, MO), was used as a control Ab. Abs were purified
from culture supernatant or rat serum using protein G chromatography,
and were biotin- or fluorochrome-conjugated according to standard
protocols. Endotoxinlow anti-CD40 mAb (clone 3/23) was
purchased from BD PharMingen (San Diego, CA).
HKL stimulation in vitro
Single spleen cell suspensions were prepared by passing the spleens through a metal sieve. Erythrocytes were lysed by treatment with NH4Cl lysis buffer (8.29 g/L NH4Cl, 1.0 g/L KHCO3, and 0.037 g/L EDTA). The cells were washed in RPMI 1640 containing 10 mM HEPES, and resuspended in RPMI 1640 supplemented with 10% FCS (Sigma), 1 mM L-glutamine, 5 x 10-5 M 2-ME, 10 mM HEPES, 1 mM sodium pyruvate, 100 µg/ml penicillin, and 100 U/ml streptomycin. This medium was designated RP10. Except where indicated, all tissue culture reagents were obtained from Biochrom. The cells were cultured for 72 h at 2 x 105 cells/well in 200 µl RP10 in a round-bottom 96-well plate (Nunc, Naperville, IL). The cells were left unstimulated or stimulated with 107/ml HKL. In some experiments, the cells were also stimulated with 108/ml HKS as an irrelevant Ag.
Enzyme-linked immunospot assay (ELISPOT)
ELISPOT plates (Millipore, Bedford, MA) were coated with 4
µg/ml anti-IFN- mAb (R4-6A2) or 2 µg/ml anti-IL-4 mAb
(BVD4-1D1; BD PharMingen) in 0.05 M carbonate buffer (pH 9.6) at 4°C
overnight. The plates were washed once and blocked with PBS-1% BSA for
2 h at 37°C. After two washes, 105 spleen
cells were added and either cultured with 107/ml
HKL or left unstimulated in RP10 for 24 h. The plates were washed
extensively, and 0.25 µg/ml biotinylated anti-IFN- mAb
(XMG1.2) or 0.25 µg/ml anti-IL-4 mAb (BVD6-24G2) was added. After
2 h incubation at 37°C, the plates were washed and alkaline
phosphatase-conjugated streptavidin (Dianova, Hamburg, Germany) was
added for a further 1-h incubation. The plates were washed, and color
was developed for 15 min by addition of 5-bromo-4-chloro-3-indolyl
phosphate/nitroblue tetrazolium alkaline phosphatase substrate
(Sigma). Spots were counted under a dissecting microscope.
ELISA
IFN- in tissue culture supernatant was measured using a
standard ELISA protocol. Briefly, ELISA plates were coated for 1 h
at 37°C with 2 µg/ml of anti-IFN- mAb (R4-6A2). The plates
were washed four times in wash buffer (PBS-0.1% Tween 20) and
then blocked at 37°C for 2 h with PBS-1% BSA-0.1% Tween 20.
After washing, appropriate dilutions of sample and rIFN- standard
were added, and the plates were incubated overnight at 4°C. The
plates were washed and incubated sequentially for 1 h at 37°C
with 2 µg/ml biotinylated anti-IFN- (XMG1.2) and
streptavidin-alkaline phosphatase (Dianova), with washing in between
steps. Color was developed with p-nitrophenyl phosphate
(Sigma), and the plates were read at 405 nm.
Intracellular IFN- staining
Spleen cells were cultured for 20 h in a 48-well plate
(Costar, Cambridge, MA) at 3 x 106 cells/ml
in 1 ml RP10, either unstimulated or with 5 x
107/ml HKL. Brefeldin A (10 µg/ml; Sigma) was
added during the last 4 h of incubation. The cells were washed in
PBS, blocked for 10 min at room temperature with mAb to FcIII/II and
rat serum (1/200; Jackson ImmunoResearch, West Grove, PA) and stained
with Cy5-conjugated anti-CD8 mAb and Tri-Color-conjugated
anti-CD4 mAb (Caltag, South San Francisco, CA) for 15 min on ice.
The cells were washed in PBS and fixed for 30 min at room temperature
in PBS-4% paraformaldehyde. After washing in PBS-0.1% BSA, the cells
were permeabilized by addition of 100 µl PBS-0.5% saponin-0.1% BSA.
After 10 min, FITC-conjugated isotype control (clone R3-34; BD
PharMingen) or anti-IFN--FITC mAb (XMG1.2) was added. After a
20-min incubation, the cells were washed in PBS-0.1% BSA and fixed in
PBS-1% paraformaldehyde. The cells were analyzed on a FACScan (BD
Biosciences, Mountain View, CA) using CellQuest software (BD
Biosciences).
Challenge experiments
Mice were infected i.v. with a sublethal dose of 5 x
103 CFU L. monocytogenes. Three days
later, the bacterial load was determined in the liver and spleen.
Alternatively, mice were infected i.v. with 5 x
104 CFU (5x LD50), and
survival was monitored over the next 14 days.
T cell depletion
For depletion of T cells, mice were treated i.p. 3 days before and at the time of infection with 300 µg anti-CD4 and/or anti-CD8 mAb. The extent of depletion was checked by flow cytometry, and 96% of CD4+ T cells and 95% of CD8+ T cells were depleted by the respective treatments.
Statistics
CFU data were analyzed using a two-tailed Mann-Whitney U test. Differences were considered significant when p < 0.05.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Intravenous HKL administration elicits little or no detectable
immune response. We hypothesized that activation of host APCs by
coadministration of an agonistic anti-CD40 mAb (clone 1C10) could
provide strong adjuvant activity for HKL immunization. C57BL/6 mice
were immunized with 109 HKL i.v. and immediately
afterward were given 100 µg anti-CD40 mAb or control rat IgG i.p.
The immunization was repeated 14 days later. As a positive control, one
group of mice was infected with 5 x 103 CFU
L. monocytogenes i.v. on day 0. Twenty-eight days after the
initial immunization, spleen cell cytokine production in response to
stimulation with HKL (107/ml) was measured by ex
vivo ELISPOT assay (Figs. 1
, A
and B). Little or no HKL-specific cytokine production was
detected in spleen cells from mice treated with control IgG,
anti-CD40 mAb, or control IgG plus HKL. In contrast,
HKL/anti-CD40 immunization was associated with a markedly enhanced
frequency of IFN-- (Fig. 1A) but not IL-4-producing cells
(Fig. 1B) in response to HKL stimulation.
|
-producing cells was associated with
increased total IFN- production. Spleen cells from immunized mice
were cultured for 72 h with 107/ml HKL,
after which supernatant was collected and IFN- measured. High levels
of HKL-specific IFN- were produced by spleen cells from the
HKL/anti-CD40-immunized and Listeria-infected mice but
not in the other groups (Fig. 1
C). In this experiment, the
adjuvant effect of a second anti-CD40 mAb (clone 3/23; BD
PharMingen) was found to be equivalent to the 1C10 Ab. Thus, the
ability of anti-CD40 mAb to provide adjuvant activity is not
restricted to the 1C10 clone. The 3/23 mAb was a commercially available
"low-endotoxin" preparation (<0.1 ng/µl). A previous study found
that the BD PharMingen anti-CD40 preparations did not contain
detectable levels of endotoxin and, when administered alone, did not
induce IL-12 or IFN- production in mice (20).
Therefore, these results argue against the involvement of endotoxin in
our system, although we cannot fully exclude a possible contribution by
very low levels of endotoxin.
The response to HKL in the HKL/anti-CD40 group (and the live
L. monocytogenes group) was specific for HKL, as the
IFN- response of spleen cells from this group to HKS was no
different to that seen by the other experimental groups (data not
shown).
HKL/anti-CD40 immunization primes HKL-specific CD4+ and CD8+ T cells
To identify the HKL-specific IFN--producing cells,
intracellular cytokine staining was performed (Fig. 2). Spleen cells from immunized mice were
cultured overnight with or without 5 x
107/ml HKL, followed by surface CD4 and
CD8- and intracellular IFN- staining.
Essentially, no IFN- could be detected in unstimulated spleen cells
from any group. In response to HKL restimulation, both
CD4+ and CD8+ T cells from
HKL/anti-CD40-immunized and Listeria-infected mice
produced IFN- (Fig. 2). In contrast, no HKL-specific IFN-
production was detected in spleen cells from the control HKL or
anti-CD40 groups. L. monocytogenes is known to induce a
strong CD8+ T cell response by virtue of its
capacity to escape from the phagosome into the cytoplasm
(21). However, the strength of the
CD8+ T cell response in the HKL/anti-CD40
group was unexpected, because exogenous Ags generally stimulate
CD8+ T cell responses weakly or not at
all.
|
Production of IFN- is critical for effective control of a
primary Listeria infection. This suggests that HKL-specific
IFN--producing cells induced by HKL/anti-CD40 treatment may
protect mice from L. monocytogenes challenge. C57BL/6 mice
were immunized as described above, except that, on day 20 following the
second immunization, mice were challenged i.v. with 5 x
104 CFU L. monocytogenes (5x
LD50) and survival was monitored for a 14-day
period (Fig. 3). All mice treated with
control IgG ± HKL or anti-CD40 mAb alone succumbed to
Listeria infection. In contrast, all mice vaccinated with
either HKL/anti-CD40 or live Listeria survived
(Fig. 3).
|
).
|
). Similarly, mice vaccinated
with HKS and anti-CD40 mAb were protected against S.
typhimurium challenge but not against L. monocytogenes
(Table I). These results also underline the broad utility of
anti-CD40 mAb as a vaccine adjuvant by demonstrating that
HKS/anti-CD40 is an effective vaccine against S.
typhimurium infection.
|
To test the role of IL-12 in anti-CD40-mediated adjuvant
activity, mice were vaccinated and immediately treated with 500 µg
anti-IL-12 mAb or rat IgG. A second anti-IL-12 mAb treatment
was given on day 2. Fourteen days after HKL/anti-CD40 immunization,
one group of mice was killed and HKL-specific cytokine production by
spleen cells was measured (Fig. 5A). Another group of mice was
challenged i.v. with 5 x 103 CFU L.
monocytogenes. Bacterial load in the spleen was measured 3 days
later (Fig. 5B). Neutralization of IL-12 at the time of
vaccination abrogated the induction of IFN--producing HKL-specific T
cells (Fig. 5A; p < 0.05 compared with the
rat IgG-treated group) and protective immunity (Fig. 5B;
p < 0.01). In contrast, neutralization of TNF at the
time of vaccination had no effect on vaccine efficacy (data not
shown).
|
To identify the cells responsible for protection,
CD4+ and/or CD8+ T cells
were depleted from HKL/anti-CD40-vaccinated mice immediately before
i.v. challenge with 5 x 103 CFU L.
monocytogenes. Bacterial load in the liver and spleen was
determined 3 days later. Depletion of either CD4+
or CD8+ T cells markedly reduced vaccine
efficacy, whereas depletion of both CD4+ and
CD8+ T cells fully abrogated vaccine-mediated
protection (Fig. 6). In general,
depletion of CD8+ T cells had a greater effect
than that of depleting CD4+ T cells, although a
significant difference between the two treatments was not found in all
experiments (e.g., in the experiment shown in Fig. 6, p
< 0.05 in the liver and p = 0.056 in the spleen for
anti-CD4 vs anti-CD8 treatment). We conclude that
CD4+ and CD8+ T cells are
stimulated by HKL/anti-CD40 vaccination and that both T cell
populations contribute to protection.
|
In an experiment to examine the longevity of protection, C57BL/6
mice were vaccinated with HKL/anti-CD40 on day 0 and day 14.
Control mice received no treatment. Three mice per group were killed on
days 34 and 85 for analysis of HKL-specific IFN- production by their
spleen cells. The amount of HKL-induced IFN- produced by spleen
cells from vaccinated mice was similar at days 34 and 85 (Table II). Additionally, five mice per group
were challenged i.v. with 5 x 103 CFU
L. monocytogenes on days 34 and 85. Three days following
challenge, bacterial load in the spleens of vaccinated mice was
substantially reduced in comparison to control mice (Table II). The
extent of vaccine-mediated protection at days 34 and 85 was the same.
Thus, a fully effective long-term memory response that lasted at least
10 wk following the booster vaccination was induced by
HKL/anti-CD40 vaccination.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The results in this study indicate that targeting costimulatory
molecules such as CD40 may be a promising approach for the development
of improved vaccine adjuvants. HKL is weakly immunogenic in vivo
(4, 5, 6), although transient protection has been reported in
mice repeatedly vaccinated with HKL (7). In the present
study, HKL was converted to a highly immunogenic vaccine when given
together with anti-CD40 mAb. HKL/anti-CD40 vaccination was
IL-12-dependent, induced an exclusively type 1 cytokine response
(IFN- but not IL-4), and stimulated both CD4+
and CD8+ T cells. Most importantly, vaccinated
mice were protected against listeriosis. This is the first
demonstration of the potential of anti-CD40 mAb as an adjuvant for
vaccination against an intracellular pathogen.
CD40 is expressed on a wide range of immune cells, including B cells,
macrophages, DCs, and mast cells, as well as on many cells not
considered to be part of the immune system (8, 22).
Reflecting its broad cellular distribution, the CD40-CD154 pathway is
involved in many immune and inflammatory processes. We have identified
CD4+ and CD8+ T cells as
the effector cells mediating vaccine-induced protection against
L. monocytogenes, but we have not defined the immediate
target cell of anti-CD40 mAb treatment. A likely candidate for at
least some of the CD40-mediated adjuvant activity is the DC, which
undergoes a broad range of phenotypic changes in response to CD40
signaling, the end result of which is to markedly enhance the DC’s
ability to productively prime T cells (23). This involves
alteration of proteasome composition (24), up-regulation
of costimulatory and adhesion molecules such as CD80/CD86 and ICAM-1,
and the induction or increased expression of numerous cytokines and
chemokines, including IL-12, IL-18, EBI1-ligand chemokine and
macrophage-inflammatory protein-1 (9, 10, 11, 12, 13). Taken
together, the characteristics of DCs, including their response to CD40
signaling, points to DCs as a central target cell for the
anti-CD40-mediated adjuvant activity. However, a range of other
cell types such as macrophages or endothelial cells may also be
involved. A small proportion of T cells can express CD40
(25), although, in a similar system, it was shown that
anti-CD40 mAb did not act directly on T cells
(26).
The T cell response induced by HKL/anti-CD40 vaccination was notable for its extreme Th1 bias. Indeed, no HKL-specific IL-4 production could be detected using a sensitive ELISPOT assay. The potency with which anti-CD40 mAb treatment promotes a Th1 response was also demonstrated by therapeutic treatment of L. major-infected BALB/c mice, in which administration of anti-CD40 mAb was associated with a Th1, rather than the characteristic Th2, response normally observed in this mouse strain (14). This ability of anti-CD40 mAb to potentiate Th1 responses is an attractive feature for vaccination against intracellular bacteria and contrasts with alum, the only adjuvant widely used in human vaccines that predominantly enhances Th2 responses.
A second notable feature of the T cell response in HKL/anti-CD40-vaccinated mice was the strong CD8+ T cell response. In recent years, increasing numbers of papers have described exceptions to the classical dogma that states that exogenous Ag does not enter the MHC class I pathway. However, the rules that determine when and how exogenous Ags can be presented via MHC class I to CD8+ T cells are still under study (27, 28). The development of new strategies to enhance CD8+ T cell responses is an area of considerable interest for vaccine research (29). CD40 signaling is necessary for induction of Th-dependent CD8+ T cell responses, (30, 31, 32), and a recent study demonstrated that anti-CD40 mAb treatment greatly enhanced the CD8+ T cell response to i.p. administration of the model Ag OVA (33). Furthermore, anti-CD40 mAb treatment converted a tolerogenic CTL epitope into an immunogenic one (16), and CD8-mediated tumor eradication could be stimulated by treatment of mice with anti-CD40 mAb (15). Although it remains to be established how HKL-derived Ags are introduced into the MHC class I pathway, it is clear that targeting CD40 is a promising approach for enhancing CD8 T cell responses to exogenous Ags.
IL-12 was essential for CD40-mediated priming of IFN--producing
HKL-specific T cells. The requirement for IL-12 may reflect the failure
of HKL to induce substantial IL-12 production in vivo, in contrast to
the robust IL-12 production associated with live Listeria
infection (34, 35). Indeed, it has previously been shown
that coadministration of IL-12 with HKL results in the development of a
protective immune response, albeit one that predominantly involves
CD4+ T cells (4). However, bolus
delivery of immunostimulatory cytokines is sometimes associated with
unacceptable toxicity (18). Direct targeting of APCs via
cell surface molecules such as CD40 may be a superior approach with
potentially fewer side effects. Anti-CD40 mAb treatment alone is
associated with generalized immune activation (36, 37),
but promising data has been reported for generation of T
cell-independent Ab responses in which directly linking anti-CD40
mAb to the vaccine Ag allowed 500-fold less Ab to be used
(37). An alternative approach has been described by
Gurunathan et al., (38) who used a trimeric CD40 ligand
DNA construct to enhance cellular immunity to coadministered naked DNA
vaccines. Furthermore, coadministration of the CD40 ligand construct
with soluble Leishmanial Ag was able to induce protective immunity
(38).
Our inability to induce immunity after vaccination of mice with HKL alone is consistent with numerous previous studies (4, 5, 6). In contrast, an earlier study from this laboratory using an unconventional immunization protocol (three doses of HKL i.v. at 5-day intervals) demonstrated CD8+ T cell-mediated protection against subsequent Listeria challenge. However, the protection achieved was weak and relatively short-lived, having already declined substantially at 4 wk after vaccination. Indeed, effective long-term protection by killed or subunit vaccines can be difficult to achieve. For example, vaccination with Mycobacterium tuberculosis culture filtrate proteins in incomplete Freund’s adjuvant gave appreciable protection 1–3 mo following vaccination, but was markedly reduced by 5 mo (39). In the present study, the strength of vaccine-mediated protection was the same 34 or 85 days after vaccination, indicating that a genuine state of memory was obtained by this vaccination strategy. In a preliminary experiment, we also found substantial protection 5 mo after immunization (data not shown).
It is interesting to note that although anti-CD40 mAb treatment converts HKL to an effective vaccine, CD40 signaling is not required for effective immunity against L. monocytogenes infection (40). This highlights the principle that rational vaccine development need not restrict itself to mimicking the natural immune response but may profitably follow alternative strategies.
Targeting CD40 is a promising approach to vaccination against intracellular pathogens and may be especially valuable for pathogens requiring both CD4+ and CD8+ T cells for control. This includes not only viral, but also bacterial (e.g., M. tuberculosis) and protozoal (e.g., Plasmodium sp.) pathogens. To this end, we have recently initiated studies in the mouse model of M. tuberculosis infection; anti-CD40 mAb treatment greatly enhances the immunogenicity of M. tuberculosis culture filtrate proteins (M. R., unpublished observations). Finally, we consider that our results reflect a general and underappreciated paradigm for vaccine development, that directly targeting APCs is one of the most effective approaches for enhancing and tailoring an immune response.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
2 Abbreviations used in this paper: HKL, heat-killed Listeria monocytogenes; DC, dendritic cell; HKS, heat-killed Salmonella typhimurium; ELISPOT, enzyme-linked immunospot.
Received for publication September 26, 2000. Accepted for publication February 2, 2001.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
production in response to live or dead bacteria by TNF and other factors. J. Immunol. 161:1447.This article has been cited by other articles:
|
|
 |
|
  S. B. J. Wong, R. Bos, and L. A. Sherman Tumor-Specific CD4+ T Cells Render the Tumor Environment Permissive for Infiltration by Low-Avidity CD8+ T Cells J. Immunol., March 1, 2008; 180(5): 3122 - 3131. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. P. Hewitson, P. A. Hamblin, and A. P. Mountford In the Absence of CD154, Administration of Interleukin-12 Restores Th1 Responses but Not Protective Immunity to Schistosoma mansoni Infect. Immun., July 1, 2007; 75(7): 3539 - 3547. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Bartholdy, S. O. Kauffmann, J. P. Christensen, and A. R. Thomsen Agonistic Anti-CD40 Antibody Profoundly Suppresses the Immune Response to Infection with Lymphocytic Choriomeningitis Virus J. Immunol., February 1, 2007; 178(3): 1662 - 1670. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. T. Temmerman, C. A. Ma, L. Borges, M. Kubin, S. Liu, J. M. J. Derry, and A. Jain Impaired dendritic-cell function in ectodermal dysplasia with immune deficiency is linked to defective NEMO ubiquitination Blood, October 1, 2006; 108(7): 2324 - 2331. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. G. A. Bouwer, C. Alberti-Segui, M. J. Montfort, N. D. Berkowitz, and D. E. Higgins Directed antigen delivery as a vaccine strategy for an intracellular bacterial pathogen PNAS, March 28, 2006; 103(13): 5102 - 5107. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Feng, D. Zhang, D. Palliser, P. Zhu, S. Cai, A. Schlesinger, L. Maliszewski, and J. Lieberman Listeria-Infected Myeloid Dendritic Cells Produce IFN-{beta}, Priming T Cell Activation J. Immunol., July 1, 2005; 175(1): 421 - 432. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Kursar, A. Kohler, S. H. E. Kaufmann, and H.-W. Mittrucker Depletion of CD4+ T Cells during Immunization with Nonviable Listeria monocytogenes Causes Enhanced CD8+ T Cell-Mediated Protection against Listeriosis J. Immunol., March 1, 2004; 172(5): 3167 - 3172. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. O. Lee, L. Hartson, and T. D. Randall CD40-deficient, Influenza-specific CD8 Memory T Cells Develop and Function Normally in a CD40-sufficient Environment J. Exp. Med., December 1, 2003; 198(11): 1759 - 1764. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Samten, B. Wizel, H. Shams, S. E. Weis, P. Klucar, S. Wu, R. Vankayalapati, E. K. Thomas, S. Okada, A. M. Krensky, et al. CD40 Ligand Trimer Enhances the Response of CD8+ T Cells to Mycobacterium tuberculosis J. Immunol., March 15, 2003; 170(6): 3180 - 3186. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. J. Shedlock, J. K. Whitmire, J. Tan, A. S. MacDonald, R. Ahmed, and H. Shen Role of CD4 T Cell Help and Costimulation in CD8 T Cell Responses During Listeria monocytogenes Infection J. Immunol., February 15, 2003; 170(4): 2053 - 2063. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. L. Tutt, L. O'Brien, A. Hussain, G. R. Crowther, R. R. French, and M. J. Glennie T Cell Immunity to Lymphoma Following Treatment with Anti-CD40 Monoclonal Antibody J. Immunol., March 15, 2002; 168(6): 2720 - 2728. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Lauvau, S. Vijh, P. Kong, T. Horng, K. Kerksiek, N. Serbina, R. A. Tuma, and E. G. Pamer Priming of Memory But Not Effector CD8 T Cells by a Killed Bacterial Vaccine Science, November 23, 2001; 294(5547): 1735 - 1739. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. E. Hamilton, A. R. Tvinnereim, and J. T. Harty Listeria monocytogenes Infection Overcomes the Requirement for CD40 Ligand in Exogenous Antigen Presentation to CD8+ T Cells J. Immunol., November 15, 2001; 167(10): 5603 - 5609. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
