By
From the Clinical Immunology Section, Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892
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Abstract |
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The induction of type 1 immune responses (interleukin [IL]-12, interferon [IFN]-) has been
shown to be important in mediating protection against many intracellular infections including
Histoplasma capsulatum. Costimulatory molecules such as CD40 ligand (CD40L) have been
shown to be a central regulator of type 1 responses in vivo. To study the role of CD40L in mediating protection against infection with H. capsulatum, CD40L-deficient (CD40L
/
) and
CD40L+/+ mice were infected with H. capsulatum and assessed for various parameters. After a
lethal challenge of H. capsulatum, CD40L
/
mice were not substantially different from
CD40L+/+ mice in terms of mortality, fungal burden, or production of IFN-
, IL-12, nitric
oxide, or tumor necrosis factor
. Moreover, CD40L
/
mice treated with anti-IFN-
or
anti-IL-12 at the time of infection had accelerated mortality, providing further evidence that
IL-12 and IFN-
are produced in vivo in the absence of CD40L. In addition, CD40L
/
mice
infected with a sublethal dose of H. capsulatum survived infection, whereas all mice infected
with the same dose and treated with anti-IFN-
had accelerated mortality, demonstrating that IFN-
but not CD40L was essential for primary immunity to H. capsulatum infection. Interestingly, depletion of either CD4+ or CD8+ T cells resulted in accelerated mortality in CD40L
/
mice, suggesting a critical role for these cells in response to infection. Finally, CD40L
/
mice
initially infected with a sublethal dose of H. capsulatum were protected from secondary infection with a lethal dose of H. capsulatum, demonstrating that CD40L is not required for the maintenance of memory immunity.
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Introduction |
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The role of CD40L-CD40 costimulation in mediating
T cell responses in vivo was first shown in studies using CD40L-deficient (CD40L/
) mice. In these studies, T
cell activation and production of cytokines such as IFN-
were markedly impaired in response to protein antigens in
vivo (1). This ability of CD40L-CD40 stimulation to regulate Th1 (IFN-
) or type 1 (IFN-
, IL-12) cytokine responses in vivo was subsequently shown to occur through
at least two mechanisms (2), the first through the induction
of IL-12 from APCs such as macrophages and dendritic
cells (2) and the second by the ability of CD40L-CD40
stimulation to enhance expression of costimulatory cell surface molecules (e.g., B7-1, B7-2) on APCs, leading to increased T cell stimulation and production of IFN-
(7).
Based on these data, since CD40L-CD40 costimulation
appears to be a key regulator of CD4+ T cell-mediated
type 1 responses in vivo, the role and mechanism by which
CD40L regulates immunity to infectious pathogens is of great interest.
The first studies to examine the role of CD40L in regulating immune responses to infection were done using murine models of parasitic and viral infections. In studies of viral infection, CD40L/
mice exposed to lymphocytic
choriomeningitis virus had normal primary CTL responses
with clearance of infection (14); however, memory
CTL responses were impaired, suggesting that CD40L was important in maintaining a memory cellular (CTL) response (14). With regard to the role of CD40L in an infectious model requiring type 1 cytokine production, a series
of studies were done using the well-established murine
model of Leishmania infection (17). In these experiments, CD40
/
or CD40L
/
mice on a resistant background were markedly impaired in production of IL-12
(17) and IFN-
(17), correlating with enhanced susceptibility to infection (17, 19) or exacerbation of infection (18).
The aforementioned studies provided strong evidence that CD40L-CD40 interactions were important in mediating CD4+ T cell-dependent production of IL-12 to either protein antigens or Leishmania infection in vivo; however, DeKruyff et al. then showed a CD40L-independent pathway for IL-12 production from mononuclear cells stimulated in vitro with either LPS or heat-killed Listeria monocytogenes (20). These latter data suggested that certain intracellular pathogens can directly induce IL-12 in vitro and raised the question as to whether these or other pathogens would elicit functional type 1 immune responses in vivo in the absence of CD40L.
In this report, we addressed the role of CD40L in regulating type 1 cytokine responses in vivo using a murine
model of disseminated histoplasmosis. Histoplasma capsulatum is a dimorphic fungus found in the soil in distinct geographic regions around the world. Primary infection occurring through inhalation of conidial or mycelial fragments
often results in a self-limited upper respiratory infection in
immunocompetent hosts. By contrast, in immunocompromised hosts, disseminated infection can occur in multiple
organs either through primary infection as described above
or by recurrence of a previous infection (21). Protective
immunity is achieved by the interaction of T cells and macrophages through the generation of a type 1 immune response characterized by production of IL-12 leading to IFN- induction (24, 25). Additional factors such as TNF-
and nitric oxide have also been shown to be important in
mediating protection against primary infection (26). The
studies presented here examined the role of CD40L in the
generation of an immune response after both primary and
secondary infection with H. capsulatum using CD40L
/
mice. The results show that CD40L
/
mice are not substantially different from CD40L+/+ mice in terms of mortality, fungal burden, or the ability to develop a functional
type 1 cytokine response in vivo compared with control
CD40L+/+ mice after infection with H. capsulatum. Furthermore, although both CD40L
/
and CD40L+/+ mice
infected with a sublethal dose of H. capsulatum survived infection and developed sterilizing immunity, all mice infected with the same dose and treated with anti-IFN-
at
the time of infection had accelerated mortality. These data
provide clear evidence that IFN-
but not CD40L is essential
for protective immunity to primary H. capsulatum infection.
Finally, of interest was the observation that CD40L
/
mice
depleted of either CD4+ or CD8+ T cells had accelerated
mortality and increased fungal burden after primary infection. Overall, these studies demonstrate that CD40L
/
mice develop relatively intact type 1 cytokine responses to
H. capsulatum and suggest a differential requirement for
CD40L in the generation of this type of immune responses
after infection to H. capsulatum versus Leishmania major.
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Materials and Methods |
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Mice and Infection.
CD40LMedia.
HBSS (Biofluids, Inc., Rockville, MD) was used as a wash medium. Complete medium: RPMI 1640 (Biofluids, Inc.) supplemented with 10% fetal bovine serum (Biofluids, Inc.), penicillin (100 U/ml), streptomycin (100 µg/ml), L-glutamine (2 mM), sodium pyruvate (1 mM), and 2-ME (0.05 mM) was used for culturing spleen cells.Preparation and Quantitation of H. capsulatum.
The yeast phase of H. capsulatum (strain GS-57) was used in all experiments, and quantitation of H. capsulatum was performed as previously described (26). In brief, spleens from mice infected with H. capsulatum and/or treated with various cytokine antagonists were killed at various times after infection. In most experiments, three individual spleens from each group were quantitated for CFUs. In some experiments, one-third of each spleen from two or three individual animals in each group were combined and homogenized in a sterile mortar using PBS to prepare a 1:10 wt/vol suspension. 10-fold dilutions in PBS were plated in duplicate at 0.05 ml/plate on BHI-SAGC medium and incubated for 7 d at 30°C. Colonies were enumerated and the counts were recorded as CFUs.In Vivo Treatment of Mice.
Most antibodies were purified from ascites by ammonium sulfate precipitation. Rat anti-mouse IFN-Cytokine mRNA Measurement.
Cytokine mRNA levels were determined by semiquantitative reverse transcription PCR techniques as previously described (26). In brief, total RNA was isolated from spleen cells by resuspending in RNAzol B (Tel-Test, Friendswood, TX) and recovering the aqueous phage after addition of chloroform. RNA was precipitated with alcohol and resuspended in RNase-free H2O. Total RNA (1 µg) was reverse transcribed by Moloney murine leukemia virus reverse transcriptase (GIBCO BRL, Gaithersburg, MD). The reaction mixture was then diluted 1:8, and 10 µl was used for specific semiquantitative amplification of cytokine mRNA with Taq DNA polymerase (Promega, Madison, WI) and specific cytokine sense and antisense primers. The number of amplification cycles was as follows: 24 (hypoxanthine phosphoribosyltransferase), 25 (IFN-Statistics.
Statistical evaluation of differences between means of experimental groups was done by analyses of variance and multiple Student's t tests. The log-rank was used for statistical analysis of mortality. A value of P <0.05 was considered to be significant. ![]() |
Results |
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Recent work by several groups has shown that
CD40/
or CD40L
/
mice were susceptible to Leishmania infection due to diminished production of type 1 cytokines (17). In other studies, mice infected with H. capsulatum (6 × 105) and treated with anti-IL-12 or anti-
IFN-
have accelerated mortality, demonstrating a critical
role for these cytokines in primary infection to H. capsulatum (24, 25). Thus, the role of CD40L in mediating protective immunity and the generation of type 1 cytokine
production in response to H. capsulatum infection was evaluated. As shown in Fig. 1 A, the rate at which CD40L
/
mice succumbed to infection (14.67 ± 3.82 d) was not different than that for CD40L+/+ mice (14.75 ± 3.84 d). By
contrast, in the same experiment, CD40L
/
mice infected
with L. major were found to be susceptible to infection compared with control CD40L+/+ mice (Fig. 1 B). These
data suggest that CD40-CD40L stimulation, although essential for induction of type 1 responses to L. major (17),
may not be required for eliciting type 1 cytokine responses to H. capsulatum.
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In addition to the experiments shown above using CD40L/
mice bred several generations (greater than six) onto a
C57BL/6 background, a series of experiments using
CD40L
/
mice on a C57BL/6 × 129 background were
initiated. It should be noted that in these experiments, the
control CD40L+/+ mice are C57BL/6 × 129(F2), approximating the background of the CD40L
/
mice. As shown
in Fig. 2 in data combined from two independent experiments, infection of CD40L
/
mice with H. capsulatum
(6 × 105) showed a modest but not statistically significant
increase in the rate of mortality (35.6 ± 20.4 d) compared
with the control CD40L+/+ mice (41.5 ± 21.3 d). In addition, all mice infected with a sublethal dose (6 × 104 or 6 × 103) survived infection. Thus, these data support a CD40L-independent role in protective immunity.
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To correlate
whether the fatal outcome shown above was due to an increase in the infectious burden of H. capsulatum, quantitative cultures were set up from spleen cells at various times
after infection. In the same experiment as shown in Fig. 2,
spleen cells of mice were harvested 7 d after infection and
CFUs for H. capsulatum were determined (Table 1).
CD40L/
mice infected with 6 × 105 yeast cells had a
twofold increase in infectious burden at 7 d after infection
compared with control mice. Furthermore, CD40L
/
mice infected with lower doses (6 × 104, 6 × 103) had almost identical CFUs for H. capsulatum compared with control mice. These data further support the contention that
CD40L is dispensable for this infection.
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In the studies examining cytokine production in CD40/
or CD40L
/
mice in response to leishmanial infection, it was clear that there was a marked deficiency in production of IFN-
(17), IL-12 (17, 19), and nitric oxide (NO) (18). To
determine whether any qualitative or quantitative changes
in cytokine production occurred in CD40L
/
mice compared with control CD40L+/+ mice after H. capsulatum infection, mRNA expression for several cytokines previously
found to be important in regulating primary immunity to
H. capsulatum was assessed by semiquantitative PCR at various time points after infection. As shown in Fig. 3,
mRNA for IFN-
, IL-12 p40, and TNF-
were expressed
from spleen cells of CD40L
/
and CD40L+/+ mice 7 and
20 d after infection with any of the doses tested. In addition, mRNA for NO was expressed from both types of
mice 7 d after infection. As a control, there was minimal
mRNA expression for any of the cytokines from spleen
cells of uninfected mice prepared at day 7 after infection.
Thus, these data confirm that type 1 cytokines are induced
in CD40L
/
mice after infection with H. capsulatum. Finally, it should be noted that similar amounts (4-7 ng/ml)
of IL-12 protein (p40 + p70) were detected from serum 3 and 7 d after infection from both CD40L
/
and CD40L+/+
mice (data not shown).
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The data shown above suggest that CD40L/
and CD40L+/+ mice induce comparable type 1 immune
responses that might provide some immunity against a lethal challenge with H. capsulatum. Functional evidence showing that CD40L
/
mice are capable of producing
IL-12 and IFN-
in vivo was demonstrated by treating
mice with neutralizing antibodies against IL-12 or IFN-
at
the time of infection and assessing their outcome. As shown
in Fig. 4, CD40L
/
mice treated with either anti-IL-12
(8.6 ± 1.3 d) or anti-IFN-
(8.8 ± 1.1 d) had accelerated
mortality compared with mice infected with only CD40L
/
(31.0 ± 15.1 d; P <0.05). Similar results were seen from
CD40L+/+ mice after infection. Neutralization of IL-12 or
IFN-
also resulted in a 3-10-fold increase in infectious
burden of H. capsulatum compared with infected-only mice
(P <0.001), providing further evidence that CD40L
/
mice are capable of making IL-12 and IFN-
in vivo.
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Although CD40L/
mice had similar outcomes to control mice infected with a lethal dose of H. capsulatum, most of them still succumbed to infection. By contrast, as demonstrated in Fig. 2, CD40L
/
mice infected
with 6 × 104 yeast cells were able to control infection, suggesting that CD40L is not essential for protective immunity
at this infective dose. Since we had shown in a previous
study that IFN-
/
mice infected with 6 × 104 or 6 × 103 yeast cells succumbed to infection (26), the relative dispensability of CD40L compared with IFN-
in developing
effective immunity against primary infection with a sublethal dose of H. capsulatum (6 × 104) was assessed. As shown
in Fig. 5, all CD40L
/
and CD40L+/+ mice survived infection with 6 × 104 yeast cells, whereas all mice treated
with anti-IFN-
had a fatal outcome with accelerated
mortality. These experiments show conclusively that effective primary immunity to H. capsulatum occurs in an IFN-
-dependent, CD40L-independent manner.
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Both CD4+ and CD8+ T cells have been shown to be important in primary immunity against H. capsulatum (33, 34).
To assess the role of CD4+ and CD8+ T cells in CD40L/
mice infected with H. capsulatum, animals were treated
with antibodies against CD4+ and CD8+ T cells before, at
the time of, and after infection to ensure depletion (>95%
by FACS®). As shown in Fig. 6 in data combined from two
independent experiments, depletion of either CD4+ (12.8 ± 0.9 d) or CD8+ T cells (12.3 ± 0.05 d) caused accelerated mortality compared with infected controls (34.8 ± 19.6 d). This increase in mortality was associated with a
three- to fourfold increase in CFUs for H. capsulatum from
spleen cells of mice depleted of either CD4+ or CD8+ T
cells (P <0.001). Thus, in the absence of CD40L, CD4+ or
CD8+ T cells play a critical role in protective immunity.
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One final aspect of these
studies was to examine the requirement for CD40L in a
memory or secondary immune response to H. capsulatum.
To assess the role of CD40L/
in the maintenance of immunity after secondary infection, CD40L
/
mice were
initially infected with a sublethal dose of H. capsulatum (6 × 104) and then reinfected 3-4 wk later with a lethal dose (6 × 105). As shown in Fig. 7 in data combined from two independent experiments, all CD40L
/
mice reinfected with a
lethal dose (6 × 105) survived and remained healthy up to
120 d after infection. As a control, a majority of the
CD40L
/
mice undergoing primary infection (6 × 105) at
the same time succumbed within 20-30 d, consistent with
the data shown in the previous figures.
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To determine whether effective immunity to a secondary challenge was due to control of H. capsulatum in vivo,
the infectious burden of H. capsulatum was assessed from
spleen cells at various time points after reinfection. Mice
originally infected with 6 × 104 yeast cells had low but detectable amounts of H. capsulatum at the time of reinfection
(day 0) in one of the experiments (Table 2, Exp. 1) and no
detectable amounts in the other experiment (Table 2, Exp.
2). When assessed 7 d after reinfection, previously infected
CD40L/
mice had a 3-log reduction (P <0.001) in H. capsulatum compared with CD40L
/
mice undergoing
primary infection (Table 2, Exp. 2) at the same time.
Moreover, in neither experiment was there any H. capsulatum detected from spleen cells at 60 or 90 d after reinfection, demonstrating that CD40L
/
is not essential for the
development of sterilizing immunity after reinfection.
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Discussion |
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CD40L-CD40 interactions have a central
role in the induction of humoral and cellular immune responses (35, 36). With regard to its effects on the cellular
immune response, CD40L-CD40 induction of inflammatory cytokines and costimulatory molecules from macrophages and dendritic cells has been shown to enhance the
cellular immune response with production of type 1 cytokines (35). Since IL-12-dependent production of IFN- was
shown to be essential for protective immunity after primary
infection to the intracellular fungi H. capsulatum (24), it was
of interest to determine the requirement for CD40L in the
generation of type 1 cytokine responses after primary and secondary infection with H. capsulatum. The initial experiments using CD40L
/
mice bred onto a C57BL/6 background (>6 generations) showed that they did not have accelerated mortality or increased fungal burden (data not shown)
compared with CD40L+/+ mice (Fig. 1). In several additional experiments using CD40L
/
mice on a C57BL/6 × 129 background, there did appear to be a modest increase
in the rate of mortality (Figs. 2 and 4) and the fungal burden (Table 1) compared with the control CD40L+/+ mice
in response to a lethal dose (6 × 105 yeast) of H. capsulatum.
However, it should be noted that CD40L
/
or CD40L+/+
mice infected with a sublethal amount of H. capsulatum (6 × 104) had identical outcomes. Furthermore, the data showing that mRNA for IL-12, IFN-
, TNF-
, and NO are
similar between the CD40L
/
and CD40L+/+ mice,
combined with the fact that in vivo neutralization with anti-IFN-
or anti-IL-12 caused accelerated mortality and
increased fungal burden, provides strong evidence that CD40L
is not required for the induction of type 1 responses after
infection with H. capsulatum. Finally, the demonstration
that all CD40L
/
mice survived infection with a sublethal
dose of H. capsulatum (Fig. 5) but all mice treated with an
anti-IFN-
antibody had accelerated mortality and increased
fungal burden provided conclusive evidence that there is a
CD40L-independent pathway for IFN-
production.
The ability of CD40L/
mice to generate functional Th1 responses in vivo is in
contrast to the studies previously alluded to in which
CD40
/
or CD40L
/
mice had a striking deficiency in
production of IL-12 or IFN-
after infection with L. major
or Leishmania amazonensis (17). Several potential mechanisms could account for this failure of these deficient mice
to develop functional type 1 responses in response to leishmanial infection. One is that L. major is a relatively poor direct inducer of IL-12 production or other inflammatory mediators compared with other infectious pathogens. This
is supported by previous studies showing that Leishmania
promastigotes are able to evade or inhibit IL-12 production
(37, 38). In data not shown, we found that peritoneal macrophages from CD40L
/
mice produced comparable amounts
of IL-12, TNF-
, and NO in vitro as CD40L+/+ mice in
response to Staphylococcus aureus Cowan strain, Toxoplasma gondii, and H. capsulatum; however, there was no induction
of these cytokines in response to L. major promastigotes (data
not shown). These data are consistent with a recent report
by DeKruyff et al. showing that heat-killed Listeria monocytogenes induces IL-12 production in a CD40L-independent
manner in vitro (20). In addition, the demonstration that
SCID mice infected with H. capsulatum (39), L. monocytogenes (40), or T. gondii (32) all had accelerated mortality when
treated at the time of infection with anti-IL-12 provides
additional evidence that these pathogens can induce IL-12
directly or at least in the absence of T cells. Taking these
data together, we would conclude that, in addition to H. capsulatum, L. monocytogenes and T. gondii would also induce IL-12 in vivo independently of CD40L. Finally, it should
be noted that although L. major may be a relatively poor direct inducer of IL-12, mice on a resistant C57BL/6 background develop effective immunity after infection with L. major in an IL-12-dependent manner, suggesting additional
factors to explain the enhanced susceptibility of CD40L
/
mice to L. major (see below).
A second mechanism to explain why CD40L/
mice
fail to induce IL-12 in response to L. major infection is that
this experimental model is highly reliant on MHC class II-
dependent CD4 responses for primary immunity (41).
Furthermore, based on in vivo (1) and in vitro (6, 20) evidence showing that CD4+ T cell-mediated production of
type 1 cytokines is CD40L dependent in response to protein antigens, it is possible that antigens that require CD4
and/or are relatively poor direct inducers of IL-12 (i.e., L. major) would require CD40L for a functional IL-12 response. This relative CD4 dependence in the Leishmania
model would be contrasted to experimental models of listeriosis, toxoplasmosis, and histoplasmosis in which both
CD4+ and CD8+ T cells have a role in primary immunity
(see below). Moreover, L. monocytogenes, T. gondii, and H. capsulatum are all potent inducers of IFN-
from NK cells
through induction of IL-12. Thus, in these latter models,
CD8+ T cells or NK cells may provide a sufficient amount
of IFN-
or other proinflammatory mediators that could help
control infection directly and/or potentiate further production of IL-12 by a positive feedback mechanism (44, 45).
As noted above, there is
evidence that CD8+ T cells also play an important role in
primary immunity against a variety of intracellular pathogens including T. gondii (46), Mycobacterium bovis (47), Mycobacterium tuberculosis (48), and H. capsulatum (34). It has
been shown that the ability of CD8+ T cells to influence
immunity is through at least two independent mechanisms.
For secondary Listeria infection, CD8+ T cells have been
shown to protect mice through a cytolytic mechanism independent of IFN- (49, 50). By contrast, in murine models of L. monocytogenes (50), M. tuberculosis (51, 52), T. gondii (53), or H. capsulatum infection (Zhou, P., manuscript in
preparation), primary immunity is maintained in the absence
of perforin- or granzyme-mediated cytolysis. Since IFN-
is
required for effective primary immunity to all of these infections, these data suggest that IFN-
produced from
CD8+ T cells is responsible for the effector function at this
phase of the response.
In the experiments reported here, CD40L/
mice depleted of either CD4+ or CD8+ T cells had similar outcomes in terms of accelerated mortality and increased fungal burden after primary infection with H. capsulatum. Explanations for these data follow. (a) There is a quantitative threshold for cytokine (i.e., IFN-
) production necessary for effective primary immunity in the absence of CD40L
requiring both CD4+ and CD8+ T cells. In preliminary
data, CD40L
/
mice depleted of CD4+ T cells at the time
of infection had markedly diminished production of IFN-
(data not shown). (b) Depletion of either CD4+ or CD8+
T cells changes the qualitative cytokine response. This is
consistent with a striking enhancement of the Th1 counterregulatory cytokine IL-10 noted from mice depleted of
CD4+ or CD8+ T cells (data not shown). (c) There are recent reports showing that CD4+ T cells are required for
CD8+ T cell function (54, 55). This dependence on CD4+
T cells could occur through modification of the antigen
presenting cell (i.e., CD40L-inducing activation and/or
cytokine production) or to provide a cytokine-rich environment (i.e., IL-2) for the CD8+ T cells. These explanations may relate to the studies reported here in which the
absence of both CD4+ T cells and CD40L may not provide help sufficient for CD8+ T cell activation. Experiments are now in progress to determine the immune
mechanism by which CD4 and CD8 depletion worsens the course of infection in these mice.
In a previous study, we showed that effective
primary immunity to systemic infection requires a coordinated immune response requiring many factors including
IL-12, IFN-, TNF-
, or NO. By contrast, none of these
factors alone, including IFN-
, were required for the
maintenance of immunity after secondary challenge to H. capsulatum (26); however, treatment of mice with both
anti-IFN-
and anti-TNF-
at the time of reinfection did
result in a fatal outcome. The only studies of the role of
CD40L in memory immunity were done in experimental
murine models of viral infection. In these studies, CD40L
/
mice had relatively normal primary CTL responses but had
markedly diminished memory responses (14). In this report, CD40L
/
mice initially infected with a sublethal
dose of H. capsulatum and then infected 3 wk later with a
lethal dose remain alive more than 90 d after infection with
no detectable H. capsulatum from spleen cells. These results
demonstrate that CD40L is not required for effective secondary immunity.
To summarize, L. major may in fact be one of the
few intracellular infections requiring CD40-CD40L stimulation for the induction of functional type 1 cytokine responses. Infection with other pathogens such as L. monocytogenes, T. gondii, and M. tuberculosis, which directly induce
IL-12 and/or have a role for CD8+ T cells in immunity,
would not show increased susceptibility in the absence of
CD40L. This is supported by the observations in studying
patients with hyper-IgM syndrome (56). In a large review
of such patients, a minority of patients were reported to
have increased susceptibility to opportunistic infections associated with T cell deficiencies such as Pneumocystis carinii
(<10%) and Cryptosporidium (<2%), whereas there were no
cases described for other infections mediated by type 1 cellular immune responses such as T. gondii, M. tuberculosis, or
H. capsulatum. These latter findings would be consistent
with the ability of these infectious pathogens to induce
type 1 cytokine responses by the mechanisms listed above.
In addition, since exogenous B7 costimulation has been
shown to restore IFN- production in CD40L
/
mice
(12, 13), it is possible that these various pathogens may differ in their capacity to activate accessory cells in vivo, providing a mechanism to activate T cells independently of
CD40L-CD40.
Finally, with regard to autoimmune disease, since CD40L- CD40 stimulation has been shown to be critical for both IL-12 production and T cell activation in response to protein antigens in vivo, inhibition of CD40L-CD40 may be a potent treatment for certain organ-specific autoimmune diseases. This is supported by murine models of experimental autoimmune encephalitis and inflammatory colitis in which treatment with anti-IL-12 (57, 58) or anti-CD40L (59, 60) was shown to ameliorate disease. One cause of concern from chronic treatment with either of these inhibitors would be increased susceptibility to intracellular infection. The ability to sustain and generate an effective immune response to certain intracellular pathogens independently of CD40L may lessen this potential increase in susceptibility to these particular infections by anti-CD40L-CD40 treatment. By contrast, treatments directed at inhibiting IL-12 while ameliorating autoimmune disease could still increase vulnerability to the aforementioned intracellular infections.
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Footnotes |
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Address correspondence to Robert A. Seder, LCI, NIAID, NIH, Bldg. 10, Rm. 11C215, 9000 Rockville Pike, Bethesda, MD 20892; Phone: 301-402-4816; Fax: 301-496-7383; E-mail: rseder{at}nih.gov
Received for publication 6 January 1998 and in revised form 19 February 1998.
1 Abbreviations used in this paper: CD40L, CD40 ligand; NO, nitric oxide.We thank Brenda Preuninger for technical support and Brenda Rae Marshall for editorial assistance.
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References |
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1. | Grewal, I.S., J. Xu, and R.A. Flavell. 1995. Impairment of antigen-specific T cell priming in mice lacking CD40 ligand. Nature. 348: 617-620 . |
2. |
McDyer, J.F.,
T.J. Goletz,
E. Thomas,
C.H. June, and
R.A. Seder.
1998.
CD40 ligand/CD40 stimulation regulates the
production of IFN-![]() |
3. | Shu, U., M. Kiniwa, C.Y. Wu, C. Maliszewski, N. Vezzio, J. Hakimi, M. Gately, and G. Delespesse. 1995. Activated T cells induced interleukin-12 production by monocytes via CD40-CD40 ligand interaction. Eur. J. Immunol. 25: 1125-1128 [Medline]. |
4. | Koch, F., U. Stanzl, P. Jennewein, K. Janke, C. Heufler, E. Kämpgen, N. Romani, and G. Schuler. 1996. High level IL-12 production by murine dendritic cells: upregulation via MHC class II and CD40 molecules and downregulation by IL-4 and IL-10. J. Exp. Med. 184: 741-746 [Abstract]. |
5. | Cella, M., D. Scheidegger, K. Palmer-Lehmann, P. Lane, A. Lanzavecchia, and G. Alber. 1996. Ligation of CD40 on dendritic cells triggers production of high levels of interleukin-12 and enhances T cell stimulatory capacity: T-T help via APC activation. J. Exp. Med. 184: 747-752 [Abstract]. |
6. | Kennedy, M.K., K.S. Picha, W.C. Fanslow, K.H. Granstain, M.R. Alderson, K.N. Clifford, W.A. Chin, and K.M. Mohler. 1996. CD40/CD40 ligand interactions are required for T cell-dependent production of IL-12 by mouse macrophages. Eur. J. Immunol. 26: 370-378 [Medline]. |
7. | Keiner, P.A., P. Moran-Davis, B.M. Rankin, A.F. Wahl, A. Aruffo, and D. Hollenbaugh. 1995. Stimulation of CD40 with purified soluble gp39 induces proinflammatory responses in human monocytes. J. Immunol. 155: 4917-4925 [Abstract]. |
8. | Wu, Y., J. Xu, S. Shinde, I. Grewal, T. Henderson, R.A. Flavell, and Y. Liu. 1995. Rapid induction of a novel costimulatory activity on B cells to CD40 ligand. Curr. Biol. 5: 1303-1311 [Medline]. |
9. | Shinde, S., Y. Wu, Y. Guo, Q. Niu, J. Xu, I.S. Grewal, R. Flavell, and Y. Liu. 1996. CD40L is important for induction of, but not response to, costimulatory activity: ICAM-1 as the second costimulatory molecule rapidly up-regulated by CD40L. J. Immunol. 157: 2764-2768 [Abstract]. |
10. | Meenakshi, R., A. Aruffo, J. Ledbetter, P. Linsley, M. Kehry, and R. Noelle. 1995. Studies on the interdependence of gp39 and B7 expression and function during antigen-specific immune responses. Eur. J. Immunol. 25: 596-603 [Medline]. |
11. | Ranheim, E.A., and T.J. Kipps. 1993. Activated T cells induce expression of B7/BB1 on normal or leukemic B cells through a CD40-dependent signal. J. Exp. Med. 177: 925-935 [Abstract]. |
12. |
Yang, Y., and
J.M. Wilson.
1996.
CD40 ligand-dependent T
cell activation: requirement of B7-CD28 signaling through
CD40.
Science.
273:
1862-1864
|
13. |
Grewal, I.S.,
H.G. Foellmer,
K.D. Grewal,
J. Xu,
F. Hardardottir,
J.L. Baron,
C.A. Janeway Jr., and
R.A. Falvell.
1996.
Requirement for CD40 ligand in costimulation induction, T
cell activation, and experimental allergic encephalomyelitis.
Science.
273:
1864-1867
|
14. | Borrow, P., A. Tishon, S. Lee, J. Xu, I.S. Grewal, M.B.A. Oldstone, and R.A. Flavell. 1996. CD40L-deficient mice show deficits in antiviral immunity and have an impaired memory CD8+ CTL response. J. Exp. Med. 183: 2129-2142 [Abstract]. |
15. | Oxenius, A., K.A. Campbell, C.R. Maliszewski, T. Kishimoto, H. Kikutani, H. Hengartner, R.M. Zinkernagel, and M.F. Bachmann. 1996. CD40-CD40 ligand interactions are critical in T-B cooperation but not for other anti-viral CD4+ T cell functions. J. Exp. Med. 183: 2209-2218 [Abstract]. |
16. | Whitmire, J.K., M.K. Slifka, I.S. Grewal, R.A. Flavell, and R. Ahmed. 1996. CD40 ligand-deficient mice generate a normal primary cytotoxic T-lymphocyte response but a defective humoral response to a viral infection. J. Virol. 70: 8375-8381 [Abstract]. |
17. | Campbell, K.A., P.J. Ovendale, M.K. Kennedy, W.C. Fanslow, S.G. Reed, and C.R. Maliszewski. 1996. CD40 ligand is required for protective cell-mediated immunity to Leishmania major. Immunity. 4: 283-289 [Medline]. |
18. | Song, L., J.-C. Xu, I.S. Grewal, P. Kima, J. Sun, B.J. Longley Jr., N.H. Ruddle, D. McMahon-Pratt, and R.A. Flavell. 1996. Disruption of CD40-CD40 ligand interactions results in an enhanced susceptibility to Leishmania amazonensis infection. Immunity. 4: 263-273 [Medline]. |
19. | Kamanaka, M., P. Yu, T. Yasui, K. Yoshida, T. Kawabe, T. Horii, T. Kishimoto, and H. Kikutani. 1996. Protective role of CD40 in Leishmania major infection at two distinct phases of cell-mediated immunity. Immunity. 4: 275-281 [Medline]. |
20. | DeKruyff, R.H., R.S. Gieni, and D.T. Umetsu. 1997. Antigen-driven but not lipopolysaccharide-driven IL-12 production in macrophages requires triggering of CD40. J. Immunol. 158: 359-366 [Abstract]. |
21. | Johnson, P.C., N. Khardori, A.F. Najjar, F. Butt, P.W.A. Mansell, and G.A. Sarosi. 1988. Progressive disseminated histoplasmosis in patients with acquired immunodeficiency syndrome. Am. J. Med. 85: 152-158 [Medline]. |
22. | Wheat, L.J., P.A. Connolly-Stringfield, R.L. Baker, M.F. Curfman, M.E. Eads, K.S. Israel, S.A. Norris, D.H. Webb, and M.L. Zeckel. 1990. Disseminated histoplasmosis in the acquired immune deficiency syndrome: clinical finding, diagnosis and treatment, and review of the literature. Medicine (Baltimore). 69: 361-374 [Medline]. |
23. | Nightingale, S.D., J.M. Parks, S.M. Pounders, D.K. Burns, J. Reynolds, and J.A. Hernandez. 1990. Disseminated histoplasmosis in patients with AIDS. South. Med. J. 83: 624-628 [Medline]. |
24. |
Zhou, P.,
M.C. Sieve,
J. Bennett,
K.J. Kwon-Chung,
R.P. Tewari,
R.T. Gazzinelli,
A. Sher, and
R.A. Seder.
1995.
IL-12
prevents mortality in mice infected with Histoplasma capsulatum through induction of IFN-![]() |
25. | Allendoerfer, R., G.P. Boivin, and G.S. Deepe Jr.. 1997. Modulation of immune responses in murine pulmonary histoplasmosis. J. Infect. Dis. 175: 905-914 [Medline]. |
26. |
Zhou, P.,
G. Miller, and
R.A. Seder.
1998.
Factors involved
in regulating primary and secondary immunity to infection
with Histoplasma capsulatum: TNF-![]() ![]() |
27. | Renshaw, B.R., W.C. Fanslow, R.J. Armitage, K.A. Campbell, D. Liggitt, B. Wright, B.L. Davison, and C.R. Maliszewski. 1994. Humoral immune responses in CD40 ligand- deficient mice. J. Exp. Med. 180: 1889-1900 [Abstract]. |
28. |
Gurunathan, S.,
D.L. Sacks,
D.R. Brown,
S.L. Reiner,
H. Charest,
N. Glaichenhaus, and
R.A. Seder.
1997.
Vaccination with DNA encoding the immunodominant LACK parasite antigen confers protective immunity to mice infected
with Leishmania major.
J. Exp. Med.
186:
1137-1147
|
29. | Cherwinski, H., J. Schumacher, K. Brown, and T. Mosmann. 1987. Two types of mouse helper T cell clone. III. Further differences in lymphokine synthesis between Th1 and Th2 clones revealed by RNA hybridization, functionally monospecific bioassay, and monoclonal antibody. J. Exp. Med. 166: 1229-1236 [Abstract]. |
30. | Dialynas, D.P., Z.S. Quan, K.A. Wall, A. Pierres, J. Quintans, M.R. Loken, M. Pierres, and F.W. Fitch. 1983. Characterization of the murine T cell surface molecule, designated L3T4 identified by monoclonal antibody GK1.5: similarity of L3T4 to the human Leu-3/T4 molecule. J. Exp. Med. 131: 2445-2451 . |
31. |
Sarmiento, M.,
A.L. Glasebrook, and
F.W. Fitch.
1980.
IgG
and IgM monoclonal antibodies reactive with different determinants of the molecular complex bearing Lyt2 antigen block
T cell-mediated cytolysis in the absence of complement.
J.
Immunol.
125:
2665-2672
|
32. |
Gazzinelli, R.T.,
S. Hieny,
T.A. Wynn,
S. Wolf, and
A. Sher.
1993.
Interleukin-12 is required for the T-lymphocyte-
independent induction of interferon ![]() |
33. | Gomez, A.M., W.E. Bullock, C.L. Taylor, and G.S. Deepe Jr.. 1988. Role of L3T4+ T cells in host defense against Histoplasma capsulatum. Infect. Immun. 56: 1685-1691 [Medline]. |
34. |
Deepe, G. Jr..
1994.
Role of CD8+ T cells in host resistance
to systemic infection with Histoplasma capsulatum in mice.
J.
Immunol.
152:
3491-3450
|
35. | Grewal, I.S., and R.A. Flavell. 1996. The role of CD40 ligand in costimulation to T-cell activation. Immunol. Rev. 153: 85-105 [Medline]. |
36. | Noelle, R.J.. 1996. CD40 and its ligand in host defense. Immunity. 4: 415-419 [Medline]. |
37. | Reiner, S.L., S. Zheng, Z. Wang, L. Stowring, and R.M. Locksley. 1994. Leishmania promastigotes evade interleukin 12 (IL-12) induction by macrophages and stimulate a broad range of cytokines from CD40+ T cells during initiation of infection. J. Exp. Med. 179: 447-456 [Abstract]. |
38. | Carrera, L., R.T. Gazzinelli, R. Badolato, S. Hieny, W. Müller, R. Kühn, and D.L. Sacks. 1996. Leishmania promastigotes selectively inhibit interleukin 12 induction in bone marrow-derived macrophages from susceptible and resistant mice. J. Exp. Med. 183: 515-526 [Abstract]. |
39. | Zhou, P., M.C. Sieve, R.P. Tewari, and R.A. Seder. 1997. Interleukin-12 modulates the protective immune response in SCID mice infected with Histoplasma capsulatum. Infect. Immun. 65: 936-942 [Abstract]. |
40. |
Tripp, C.S.,
M.K. Gately,
J. Hakimi,
P. Ling, and
E.R. Unanue.
1994.
Neutralization of IL-12 decreases resistance to
Listeria in SCID and C.B-17 mice. Reversal by IFN-![]() |
41. | Titus, R.G., G. Milon, G. Marchal, P. Vassalli, J.-C. Cerottini, and J.A. Louis. 1987. Involvement of specific Lyt-2+ T cells in the immunological control of experimentally induced murine cutaneous Leishmania. Eur. J. Immunol. 17: 1429-1433 [Medline]. |
42. | Locksley, R.M., S.L. Reiner, F. Hatam, D.R. Littman, and N. Killeen. 1993. Helper T-cells without CD4: control of leishmaniasis in CD4-deficient mice. Science. 261: 1448-1451 [Medline]. |
43. | Chakkalath, H.R., C.M. Theodos, J.S. Markowitz, M.J. Grusby, L.H. Glimcher, and R.G. Titus. 1994. Class II major histocompatibility complex-deficient mice initially control an infection with Leishmania major but succumb to the disease. J. Infect. Dis. 171: 1302-1308 . |
44. |
Ma, X.,
J.M. Chow,
G. Gri,
G. Carra,
F. Gerosa,
S.F. Wolf,
R. Dzialo, and
G. Trinchieri.
1996.
The interleukin 12 p40
gene promoter is primed by interferon ![]() |
45. |
Hayes, M.P.,
J. Wang, and
M.A. Norcross.
1995.
Regulation
of interleukin-12 expression in human monocytes: selective
priming by interferon-![]() |
46. | Denkers, E.Y., T. Scharton-Kersten, S. Barbieri, P. Caspar, and A. Sher. 1996. A role for CD4+NK1.1+ T lymphocytes as major histocompatibility complex class II independent helper cells in the generation of CD8+ effector function against intracellular infection. J. Exp. Med. 184: 131-139 [Abstract]. |
47. | Ladel, C.H., S. Daugelat, and S.H.E. Kaufmann. 1995. Immune response to Mycobacterium bovis bacille Calmette Guerin infection in major histocompatibility complex class I- and II- deficient knock-out mice: contribution of CD4 and CD8 T cells to acquired resistance. Eur. J. Immunol. 25: 377-384 [Medline]. |
48. | Flynn, J.L., M.M. Goldstein, K.J. Triebold, E. Koller, and B.R. Bloom. 1992. Major histocompatibility complex class I-restricted T cells are required for resistance to Mycobacterium tuberculosis infection. Proc. Natl. Acad. Sci. USA. 89: 12013-12017 [Abstract]. |
49. |
Harty, J.T., and
M.L. Bevan.
1995.
Specific immunity to Listeria
monocytogenes in the absence of IFN-![]() |
50. | Kagi, D., B. Ledermann, K. Burki, H. Hengartner, and R.M. Zinkernagel. 1994. CD8+ T cell-mediated protection against an intracellular bacterium by perforin-dependent cytotoxicity. Eur. J. Immunol. 24: 3068-3072 [Medline]. |
51. | Laochumroonvorapong, P., J. Wang, C.C. Liu, W. Ye, A.L. Moreira, K.B. Elkon, V.H. Freedman, and G. Kaplan. 1997. Perforin, a cytotoxic molecule which mediates cell necrosis, is not required for the early control of mycobacterial infection in mice. Infect. Immun. 65: 127-132 [Abstract]. |
52. | Cooper, A.M., C. D'souza, A.A. Frank, and I.M. Orme. 1997. The course of Mycobacterium tuberculosis infection in the lungs of mice lacking expression of either perforin- or granzyme-mediated cytolytic mechanisms. Infect. Immun. 65: 1317-1320 [Abstract]. |
53. | Denkers, E.Y., G. Yap, T. Scharton-Kersten, H. Charest, B.A. Butcher, P. Caspar, S. Heiny, and A. Sher. 1997. Perforin-mediated cytolysis plays a limited role in host resistance to Toxoplasma gondii. J. Immunol. 159: 1903-1908 [Abstract]. |
54. |
Bennett, S.R.M.,
F.R. Carbone,
F. Karamalis,
J.F.A.P. Miller, and
W.R. Heath.
1997.
Induction of a CD8+ cytotoxic T lymphocyte response by cross-priming requires cognate CD4+ T cell help.
J. Exp. Med.
186:
65-70
|
55. |
Cardin, R.D.,
J.W. Brooks,
S.R. Sarawar, and
P.C. Doherty.
1996.
Progressive loss of CD8+ T cell-mediated control of a
![]() |
56. | Notarangelo, L.D., M. Duse, and A.G. Ugazio. 1992. Immunodeficiency with hyper-IgM (HIM). Immunodef. Rev. 3: 101-121 [Medline]. |
57. | Leonard, J.P., K.E. Waldburger, and S.J. Goldman. 1995. Prevention of experimental autoimmune encephalomyelitis by antibodies against interleukin 12. J. Exp. Med. 181: 381-386 [Abstract]. |
58. | Neurath, M.F., I. Fuss, B.L. Kelsall, E. Stuber, and W. Strober. 1995. Antibodies to interleukin 12 abrogate established experimental colitis in mice. J. Exp. Med. 182: 1281-1290 [Abstract]. |
59. | Stuber, E., W. Strober, and M. Neurath. 1996. Blocking the CD40L-CD40 interaction in vivo specifically prevents the priming of T helper 1 cells through the inhibition of interleukin 12 secretion. J. Exp. Med. 183: 693-698 [Abstract]. |
60. |
Gerritse, K.,
J.D. Laman,
R.J. Noelle,
A. Aruffo,
J.A. Ledbetter,
W.J.A. Boersma, and
E. Classen.
1996.
CD40-CD40
ligand interactions in experimental allergic encephalomyelitis
and multiple sclerosis.
Proc. Natl. Acad. Sci. USA.
93:
2499-2504
|