| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1
*
Department of Pathology, University of Geneva, Geneva, Switzerland;
Department of Pathology, University of Bern, Bern, Switzerland;
Department of Internal Medicine, University Hospital, Zurich, Switzerland; and
Laboratoire du Bacillus Calmette-Guérin and Unité de Physiopathologie de l’Infection, Institut Pasteur, Paris, France
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
(LT-) locus (Tm TNF tg
mice). These mice were as resistant to BCG infection as wild-type mice,
whereas TNF/LT--/-, TNF-/-, and
LT--/- mice succumbed. Tm TNF tg mice developed
granulomas of smaller size but at 2- to 4-fold increased frequencies
compared with wild-type mice. Granulomas were mainly formed by
monocytes and activated macrophages expressing Tm TNF mRNA and
accumulating acid phosphatase. NO synthase 2 activation as a key
macrophage bactericidal mechanism was low during the acute phase of
infection in Tm TNF tg mice but was still sufficient to limit bacterial
growth and increased in late infection. While infection with virulent
Mycobacterium tuberculosis resulted in very rapid
death of TNF/LT--/- mice, it also resulted in survival
of Tm TNF tg mice which presented an increase in the number of CFU in
spleen (5-fold) and lungs (10-fold) as compared with bacterial load of
wild-type mice. In conclusion, the Tm form of TNF induces an efficient
cell-mediated immunity and total resistance against BCG even in the
absence of LT- and secreted TNF. However, Tm TNF-mediated protection
against virulent M. tuberculosis infection can also be
efficient but not as strong as in BCG infection, in which cognate
cellular interactions may play a more predominant role in providing
long-term surveillance and containment of BCG-infected
macrophages. |
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
R1, IL-12, and IL-12R
genes, vaccination or infection with BCG resulted in lethal
dissemination or severe infection (2, 3, 4, 5). The requirement
of IFN- and IL-12 in mediating resistance to mycobacterial
infections has been also demonstrated by using genetically modified
animals such as IFN--/- or
IFN-R-/- and
IL-12p40-/- mice, which were unable to control
M. tuberculosis and M. bovis infections
(6, 7, 8, 9, 10, 11, 12). Mycobacterial infections induce a cell-mediated immune response, in which the contribution of macrophages and CD4 and CD8 T lymphocytes is essential (13, 14). Ag-specific T cells mediate the recruitment and activation of macrophages to form bactericidal granulomas. TNF and Th1 type cytokines play a critical role in the development of protective granulomas, which contain activated macrophages producing specific enzymes, such as inducible NO synthase (iNOS) or NOS2, and which are responsible for the elimination of bacteria. These mechanisms form the basis for protection against mycobacterial spreading (15, 16). Indeed, NOS2-/- mice are highly sensitive to M. tuberculosis and M. bovis infections (17, 18) but, in contrast, they show an enhanced resistance to Mycobacterium avium infection (19).
The importance of TNF in mycobacterial infections has been extensively
reported. Neutralization of TNF with anti-TNF Abs or with soluble
TNFR1-Ig fusion protein during M. bovis and M.
tuberculosis infections or the absence of a functional TNF gene
increased sensitivity by inhibiting macrophage differentiation and the
development of well-differentiated granulomas, resulting in
mycobacterial overgrowth and rapid animal death (20, 21, 22, 23, 24).
Recently, it has been shown that lymphotoxin- (LT-) is also
required for host defense against BCG and M. tuberculosis
infections (25, 26). A contribution of cell surface-bound
LT-1
2 in protective
immunity against BCG infection has been reported (27).
Most TNF activities in defense mechanisms have been attributed to
the secreted form of TNF, and little information is available on the
contribution of the transmembrane (Tm) form. TNF is synthesized as
a 26-kDa Tm precursor and is cleaved by membrane-bound
metalloprotease(s), including the TNF--converting enzyme
(TACE) or a disintegrin and metalloproteinase into 17-kDa monomers
forming active homotrimers (28, 29, 30, 31, 32). Indications for
distinct roles of Tm and secreted TNF have been obtained (33, 34). Transgenic (tg) mice expressing (instead of wild-type TNF)
a Tm form of TNF, generated by deleting the first 12 amino acids of
processed TNF, were partially resistant to Listeria
monocytogenes infection (35). These mice were also
prone to develop arthritis (36) and Con A-induced
inflammatory liver disease (37). In addition, the
inhibition of proteolytic TNF cleavage by TACE inhibitors protected
mice completely from endotoxic shock (38). These results
indicate that the TNF activities can be mediated by both the secreted
and the Tm TNF molecules.
To dissect the functions exerted by secreted and Tm TNF in M.
bovis BCG infection and also to assess the possibility of using
TACE inhibitors in controlling deleterious effects of secreted TNF
observed in active human tuberculosis, we have infected tg mice
expressing a Tm murine TNF (Tm TNF tg) generated in
TNF/LT--/- mice (39). Mutations
of this noncleavable TNF were introduced into a genomic clone of mouse
TNF under the control of the mouse TNF promoter. The 3' AU-rich
elements of the genomic TNF locus were preserved to assure adequate
gene regulation in vivo (40). Tm TNF tg mice were
protected from LPS plus D-galactosamine-induced
mortality, and no TNF bioactivity was found in the serum of these
challenged mice (39).
Using this Tm TNF tg mouse line in systemic BCG infection, we
demonstrate that, in the absence of LT- and secreted TNF, tg mice
are able to develop a protective immunity against M. bovis
BCG and that, in the control of BCG infection, Tm TNF can compensate
the absence of LT- and exerts distinct activities from secreted
TNF.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The generation of TNF/LT--/- mice
(C57BL/6 x 129/SVEV) tg for a noncleavable TNF gene has been
described before (39). The transgene is under the control
of the TNF promoter. The AU-rich regulatory elements at the 3' end of
the TNF gene have been maintained to assure appropriate gene
regulation. To generate a noncleavable mutant of murine TNF, two
deletions (Leu-12–Leu-10
and Leu-2–Leu1) and an
amino acid substitution (Lys11 >
Glu11) were introduced into a genomic TNF
clone. Wild-type, Tm TNF tg mice and
TNF/LT--/- (41) were of a
C57BL/6 x 129/SVEV genetic background.
TNF-/- mice (42) were of C57BL/6
genetic background and LT--/- were of
129/SVEV genetic background (43). Wild-type mice of
C57BL/6 and 129/SVEV genetic background were included in survival and
bacterial content experiments. Mice were maintained under conventional
conditions in the animal facility of the Medical Faculty of the
University of Geneva (Geneva, Switzerland), or under P3 conditions in
Pasteur Institute (Paris, France).
Experimental infection and determination of BCG and M. tuberculosis CFU
Mice were inoculated into retro-orbital sinuses with 107 living BCG strain 1173 P2 or with 105 CFU of virulent M. tuberculosis strain H37Rv. The numbers of viable bacteria inoculated or recovered from organs after homogenization in saline containing 0.04% Tween 80 were determined by plating serial dilution of living bacilli onto Middlebrook 7H10 agar plates containing 10% oleic-albumin Dubos complex (Difco, Detroit, MI). Plates were incubated at 37°C for 21 days. No difference in the amount of CFU recovered from organs of BCG-infected C57BL/6 x 129/SVEV, C57BL/6, and 129/SVEV mice was found.
LPS challenge
Mice infected with 107 CFU of BCG were challenged i.p. with 1 µg/g body weight of LPS from Escherichia coli (serotype 0111: B4; Sigma-Aldrich, Schnelldorf, Germany) at day 14 after BCG inoculation. Blood samples for cytokine detection were obtained 2 h after LPS injection and mortality was monitored every 2 h.
Histologic analyses
A histopathologic analysis of infected organs was routinely performed in each experiment. Liver (at three different sites), lung (two lobes), and spleen (one-third) were fixed in 4% buffered formaldehyde and embedded in paraffin for subsequent H&E staining and Ziehl-Neelsen acid-fast staining.
Acid phosphatase activity
Acid phosphatase activity was determined on frozen tissue sections (cryostat sections of 5 µm) of liver as previously reported (20, 23, 27). The method used on tissue sections was modified for quantitative detection of acid phosphatase activity on the entire organ, as previously described (27).
In situ hybridization
A 1108-bp cDNA fragment of the murine TNF (positions 1–1108; obtained from Genentech, San Francisco, CA) was subcloned into pGEM-2. After the linearization of the plasmid, sense and antisense RNA probes were prepared using the appropriate RNA polymerases as described previously (39). Cryostat sections of organs were fixed in 4% paraformaldehyde in PBS for 20 min at room temperature, rinsed in PBS, and subsequently treated with proteinase K (Boehringer Mannheim, Mannheim, Germany) at 1 mg/ml at 37°C for 30 min. After post-fixation and acetylation, hybridization was performed with 2 x 105 cpm of 35S-labeled RNA probe per microliter of hybridization solution for 18 h at 48°C (37).
Evaluation of serum levels of cytokines
Blood samples were obtained from retro-orbital sinuses at
different time after infection. IFN-, IL-12p40, IL-10, TNF, and
IL-18 levels were evaluated by ELISA with a sensitivity of 2–1000
pg/ml.
Bioactivity of TNF in mouse serum samples was measured on WEHI cells (clone 13) compared with standard murine TNF. WEHI cells (3 x 104/well) were incubated in the presence of actinomycin D (1 µg/ml) with mouse serum (dilution from 1/20 to 1/16,000) for 20 h in a 96-well plate. One picogram of standard TNF is able to kill 50% of WEHI cells. Cell viability was assessed as previously described (18).
Determination of NOS activity in spleen extracts
Evaluation of the induction of NOS activity was done on crude frozen spleen extracts of infected and uninfected mice. Spleens were homogenized in 25 mM Tris-HCl (pH 7.4), 1 mM EDTA, and 1 mM EGTA (125 mg of tissue per milliliter of buffer). Crude supernatant was obtained by centrifugation of the homogenate at 10,000 x g for 5 min. NOS activity was measured by the ability of supernatant to convert radioactive L-[14C]arginine (Amersham Pharmacia Biotech, Piscataway, NJ) to L-[14C]citrulline as previously described (27, 44).
Ag-specific release of cytokines from spleen cells
Mice were infected with 107 BCG and sacrificed 22 wk later. The spleen cells were suspended in DMEM containing 10% FCS, treated for 5 min with a 0.155 M ammonium chloride/0.010 M potassium bicarbonate solution to lyse the erythrocytes, washed, and resuspended in DMEM plus 10% FCS. Cell suspensions were cultured in 96-well plates at 5 x 105 cells per well. The cells were stimulated with medium alone, living BCG (103 CFU/well), or BCG culture protein extracts (1.7 mg/ml) for 1, 3, or 6 days (11).
Nitrite determination
NO synthesis was assessed by measuring the accumulation of nitrite in cell supernatant as detected by the Griess reagent (1% sulfanilamide and 0.1% naphtylethylenediamide in 2.5% phosphoric acid). Absorption was measured at 550 nm and nitrite concentrations were determined by comparison with OD of the NaNO2 standards.
Statistical analyses
The unpaired Student’s t test was used for all analyses. Values of p < 0.05 were considered statistically significant.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
To explore the contribution of Tm TNF in host defense against
M. bovis BCG we have used tg mice expressing a Tm TNF but
lacking the TNF/LT- locus (Tm TNF tg mice; Ref. 39). In
the previous study, Tm TNF tg mice were shown to be protected from LPS
plus D-galactosamine-induced mortality due to
acute hepatitis as a result of rapid release of TNF (39).
To characterize Tm TNF tg mice in the context of the BCG infection, LPS
was administrated to BCG-sensitized mice. Endotoxin administration
induces a massive release of TNF, which results in fulminant hepatitis
and death. TNF/LT--/- mice as well as Tm TNF
tg mice were protected from lethal effect of BCG/LPS treatment in
contrast to wild-type mice, which all died 5–8 h after LPS challenge
(Fig. 1
A). Fig. 1B
represents serum levels of TNF in BCG/LPS-treated mice 2 h after
LPS. High amounts of serum TNF were found in wild-type but not in Tm
TNF tg and TNF/LT--/- mice as determined by
ELISA (Fig. 1B) and bioactivity on WEHI cells (data not
shown).
|
-/-, and
TNF/LT--/- mice were infected i.v. with
107 living bacilli. Inoculation of sensitive
wild-type mice with this dose of BCG leads to nonlethal and
self-limiting infection. Mice deficient for TNF/LT-, TNF, or LT-
alone died between 6 and 16 wk postinfection. In contrast, Tm
TNF tg mice survived for at least 6 mo, similar to wild-type mice (Fig. 1
D). No differences in the kinetics of weight alterations
were observed between wild-type and Tm TNF tg mice during BCG
infection. To further confirm resistance of Tm TNF tg mice to BCG
infection, we quantified CFU by colony assay on tissues from wild-type,
Tm TNF tg, and TNF/LT--/- mice 2, 4, and 10
wk after infection. Wild-type and Tm TNF tg mice showed the same levels
of living bacilli in infected organs, whereas high BCG loads were found
in TNF/LT--/- mice (Fig. 2). These data demonstrate that Tm TNF in
mice lacking TNF/LT- is sufficient for controlling BCG proliferation
and ensures animal survival.
|
We have explored the role of Tm TNF in BCG granuloma formation. At
4 wk, wild-type mice showed well-formed granulomas mainly containing
large and differentiated macrophages or epithelioid cells, T
lymphocytes, and, occasionally, polymorphonuclear cells (Fig. 3A). Granulomas from Tm TNF tg
mice were much smaller, containing few (one or two) epithelioid cells
surrounded by activated monocytes, macrophages, and lymphocytes (Fig. 3B). These cells expressed TNF mRNA as evaluated by in situ
hybridization of liver, spleen, and lung tissues. Fig. 3 shows the
presence of TNF mRNA on liver tissue sections from wild-type (Fig. 3D) and Tm TNF tg mice (Fig. 3E), but not from
TNF/LT--/- mice (Fig. 3F).
Macrophage activation within the granulomas was assessed by staining of
tissue sections for acid phosphatase activity, an enzyme produced in
large amounts by differentiated macrophages. We observed acid
phosphatase activity on liver granulomas from wild-type mice (Fig. 3G) and also from Tm TNF tg mice (Fig. 3H), but
rarely on TNF/LT--/- mouse tissues (Fig. 3I). Quantification of the acid phosphatase activity of
spleen enzyme extracts from BCG-infected mice showed the same activity
in Tm TNF tg and wild-type mice through the infection (Fig. 4A). Assessment of the number
of granuloma in the liver of Tm TNF tg mice revealed a 2-fold increase
compared with wild-type mice after 4 wk of infection (Fig. 4B).
|
|
B). At this point of the infection, liver granulomas
from wild-type mice started to disappear, signs of epithelioid cell
death were apparent, and their number was reduced (Fig. 3J).
In contrast, Tm TNF tg mice showed small but still well-differentiated
granulomas, containing a central epithelioid cell or probably a
multinucleated giant cell surrounded by monocytes and lymphocytes (Fig. 3K). These results demonstrate that the presence of Tm TNF
results in the generation of numerous granulomas containing
differentiated macrophages, but these remain of smaller size probably
due to limited cell recruitment. Bactericidal mechanisms are transiently reduced in Tm TNF tg mice upon BCG infection
Activation of NOS2 in macrophages represents one of the
bactericidal mechanisms to eliminate intracellular bacteria. NOS2 is
required for protection against BCG (18). We have
evaluated the NOS activity from crude extracts of spleen at different
time points after BCG inoculation by monitoring the conversion of
radioactive L-arginine to L-citrulline and NO
(18, 44). We observed a rapid NOS activation with maximal
production 2 wk after infection in wild-type mice. In Tm TNF tg mice
NOS was also activated, but lower levels were found at 2 wk of
infection in comparison with wild-type mice (Fig. 4C). At 4
wk of infection, NOS activity in Tm TNF tg and wild-type was similar,
and at 10 wk of infection Tm TNF tg mice showed a modest but
statistically significant enhancement of NOS activity compared with
wild-type mice, suggesting that the presence of Tm TNF sustains NOS
activity (Fig. 4C). TNF/LT--/-
mice were unable to activate the NOS2 during the acute phase infection,
and later activation appeared to be inefficient for BCG
elimination.
Transient alteration of serum Th1 cytokines in Tm TNF tg mice
BCG induces a Th1 type of immune response, characterized by the
release of IFN- and IL-12, which are required for host protection
(8, 11). To investigate whether Tm TNF tg mice are able to
produce these cytokines, we evaluated the serum concentrations of
IFN-, IL-12, and also IL-18 during infection. At 2 wk after BCG
inoculation, IFN- serum levels were lower in Tm TNF tg mice than in
wild-type mice. However, at later points during infection, IFN-
levels were similar in both groups of animals (Fig. 5). Serum concentrations of IL-12p40 were
increased in Tm TNF tg mice up to 4 wk following BCG inoculation, and
this increase in IL-12p40 was statistically significant (Fig. 5). IL-18
and IL-10 serum profiles were comparable in Tm TNF tg mice and
wild-type mice. Cytokine profiles were totally different in
TNF/LT--/- mice, which were not able to
early secrete IFN-, IL-12, IL-18, or IL-10, but at 4 wk of infection
a complete disregulation of cytokine production was observed at more
advanced stages of BCG infection, correlating with disease progression
and death.
|
and NO by splenocytes in
BCG-infected mice
To determined whether the presence of Tm TNF may affect
Ag-specific production of IFN-, the amount of IFN- was assessed
by culturing splenocytes from infected animals with BCG culture
filtrate proteins and also with living BCG. There was only a marginal
difference (1.5-fold reduction) between Ag-specific IFN- secretion
from Tm TNF tg and wild-type splenocytes when culture filtrate proteins
were used for priming (Fig. 6A). Addition of viable BCG to
the splenocyte cultures, however, induced a 2.7-fold lower IFN-
release in Tm TNF tg cells than in wild-type splenocytes (Fig. 6B). These results correlate with the lower NO production of
Tm TNF splenocytes compared with wild-type cells (Fig. 6B).
Ag-induced NO production was similar in Tm TNF and wild-type
splenocytes. In contrast, BCG-induced NO production was dramatically
reduced in Tm TNF tg cells (Fig. 6, C and D).
Furthermore, the proportion of CD4-, CD8-, and F4/80-positive cells
after 22 wk of BCG infection was similar in spleens from Tm TNF tg and
wild-type mice as analyzed by flow cytometry (data not shown).
|
-/- mice and resistance of Tm
TNF-tg mice, which show an increased bacterial load in infected organs
Infection of wild-type (n = 9), Tm TNF tg
(n = 9), and TNF/LT--/-
(n = 5) mice with virulent M. tuberculosis
(H37Rv) resulted in rapid death of
TNF/LT--/- mice, which succumbed at day
20–23 postinfection. Transgenic mice for Tm TNF survived the infection
and were healthy, with the exception of one mouse (one of nine)
that presented wasting (10% of weight lost) at day 28 of infection.
Bacterial load of wild-type and tg TNF mice were determined at day 28
as presented in Fig. 7. We observe an
increase (5-fold) in the number of CFU in the spleen of Tm TNF tg mice.
The number of CFU in the lung of wild-type mice was from 52 x
103 to 479 x 103 CFU
per lung with an average of 150 x 103 CFU
per lung. In Tm TNF tg mice the number of CFU observed was more
heterogeneous, going from 540 x 103 to
3571 x 103 CFU per lung, and the average
number was 1621 x 103 CFU per lung, or
10-fold higher that the number found in wild-type mice. These data
suggest that Tm TNF tg mice are able to survive in conditions where
TNF/LT--/- mice rapidly die. However, the
control of bacterial proliferation observed in BCG infection appears to
be less efficient for M. tuberculosis infection.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
. Tm TNF tg mice survived to BCG infection, whereas either
TNF-/-, LT--/-, or
TNF/LT--/- mice succumbed. These results
thus suggest that Tm TNF confers protection even in conditions in which
secreted wild-type TNF fails, as in LT--/-
mice, indicating that Tm TNF can also compensate for the absence of
both wild-type TNF and LT-. Indeed, in the absence of either the
TNF or LT- locus, mice are not protected from
mycobacterial infection, and TNF-/- and
LT--/- mice eventually die from excessive
intracellular bacterial proliferation. Surprisingly, in contrast to Tm
TNF, secretable TNF, which plays a predominant role during the acute
phase of infection, cannot substitute for the absence of LT- as do
surface-expressed Tm TNF. This may reflect the predominant role of
cognate cellular interactions over soluble factors in providing
long-term surveillance and control of BCG proliferation. This is
probably less predominant in M. tuberculosis infection, in
which the production of soluble factors results in more efficient
response, although the unique presence of Tm TNF without soluble TNF or
LT- confers an important protection. Previously, it has been shown
that inability to use TNF and LT- in tg mice,
TNF-/- mice, or
LT--/- mice renders animals highly
susceptible to M. tuberculosis and BCG infections
(23, 24, 25, 26, 45).
Reduction of immune surveillance in mycobacterial infections leads to
the excessive proliferation of intracellular bacteria in macrophages.
We show that tg mice expressing Tm TNF develop bactericidal mechanisms
in macrophages which are able to control BCG proliferation like
wild-type mice. Determination of bacterial loads in liver, lungs, and
spleen demonstrates that Tm TNF tg mice can efficiently control and
eliminate BCG as wild-type mice. Control of bacterial proliferation by
Tm TNF tg mice was found to be less efficient in virulent M.
tuberculosis infection and in particular in lung, in which the
presence of soluble TNF may be more important than in BCG infection.
Soluble TNF may probably mediate cell recruitment to lung tissue and
more efficiently activate mycobactericidal mechanisms. Induction of
bactericidal mechanisms, including NOS2 activation, which leads to the
generation of NO and reactive nitrogen intermediates, is crucial for
cellular immunity and protection against M. tuberculosis
infection (17, 46). BCG infection in
NOS2-/- mice resulted in an enhanced but
inefficient cellular immune response with increased recruitment of
inflammatory cells eventually causing tissue necrosis, and
overproduction of TNF (18). NOS2 was activated in Tm TNF
tg mouse spleen during the acute phase of infection, although this
activation was lower than that found in wild-type mice. This can be
explained by a limited or even delayed Th1 cell recruitment and
differentiation and lower IFN- production, as observed in Tm TNF tg
mice during acute phase of infection. Nevertheless, our data show that
expression of Tm TNF during the presence of BCG is sufficient to
sustain and enhance NOS2 activation in chronic infection.
TNF is synthesized as a 26-kDa Tm protein which is cleaved by the TACE
to yield biologically active homotrimers. Strong evidence for a
biologically active Tm precursor form of TNF in host defense has been
reported (28, 29, 30, 31, 32). The 26-kDa Tm form of TNF on CD4 T cell
clones was shown to provide a costimulatory signal for human B cell
activation (47). Tm TNF was shown to play a role in
antileishmanial and antimycobacterial defense in murine macrophages
(48, 49). Tm TNF was also shown to be implicated in the
polyclonal B cell activation induced by HIV-infected human T cells
(50). A noncleavable 
1–12 mutant of mouse TNF
expressed as a transgene in TNF-/- mice was
shown to confer a partial protection against L.
monocytogenes infection (35). These mice were also
found to be prone to develop arthritis (36). This latter
effect, however, might be attributed to the enhanced expression of the
transgene due to the absence of the AU-rich elements at the 3'
untranslated region of this Tm transgene. Absence of these regulatory
sequences has been found to cause pathological alterations due to
impaired TNF regulation (40).
Distinct functions of secreted and Tm TNF have been previously
attributed to a differential binding to the two receptors TNFR1 and
TNFR2 based on interactions with their receptors. Signaling through
TNFR2 of Tm TNF has been reported for the mutant Tm TNF 1–12.
However, the preference binding to TNFR2 of the 1–12 Tm TNF may be
due to the deletion of a proline residue in position 12
(31). Because TNF requires signaling through TNFR1 for
host defense against mycobacteria (51), the present
results thus strongly indicate that Tm TNF expressed in our Tm TNF tg
mice, where the proline residue in position 12 is preserved, can also
signal by binding to TNFR1.
Indications for bidirectional signaling processes via TNFR-Tm TNF, whereby Tm TNF may act like a receptor transducing cellular signals upon binding of soluble or membrane-bound receptors, have been recently obtained (52, 53). Reverse signaling through Tm TNF seems to play an active role in cellular interactions between endothelium and monocytes/macrophages (54). Reverse signaling processes through Tm TNF may probably play a role in macrophage activation of Tm TNF tg mice; this could also explain why Tm TNF mediates additional activities to those observed for soluble TNF.
Besides the protective role of TNF in infections, TNF production can be also associated with harmful effects such as fever and progressive weight loss. TNF was shown to be instrumental in fatal acute meningitis in rabbits when BCG-induced TNF or genetically engineered BCG strains produced TNF in the CNS (55). The release of excessive amounts of TNF can be prevented by using TACE inhibitors (38). Administration of a metalloproteinase inhibitor in healthy humans injected with a single dose of LPS strongly reduced LPS-induced TNF release but did not influence the increase in monocyte-bound TNF (56). These recent data from Dekkers et al. (56) suggest a beneficial effect of TACE inhibitors on the course of disorders where excessive production of TNF is considered to play an important role. Hence, our observation that Tm TNF can substitute for secreted TNF in host defense against BCG may indicate that TACE inhibitors may be used in human tuberculosis as therapeutic modality to attenuate harmful effects of TNF but preserving beneficial properties to maintain protective immunity.
In conclusion, our data show that in a strictly TNF-dependent model Tm
TNF mediates long-term protection to M. bovis BCG
intracellular pathogen, even in the absence of secreted TNF
homotrimers. Furthermore, the biological activities exerted by Tm TNF
in vivo may differ quantitatively from those mediated by secreted TNF
and LT-.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
2 Address correspondence and reprint requests to Dr. Irene Garcia, Department of Pathology, University of Geneva, Centre Medical Universitaire, 1 rue Michel-Servet, CH 1211 Geneva 4, Switzerland. E-mail address: Irene.Garcia-Gabay{at}medecine.unige.ch
3 Abbreviations used in this paper: BCG, bacillus Calmette-Guérin; Tm, transmembrane; tg, transgenic; NOS, NO synthase; LT-, lymphotoxin-; TACE, TNF--converting enzyme.
Received for publication December 12, 2000. Accepted for publication January 17, 2002.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
-receptor deficiency in an infant with fatal bacille Calmette-Guérin infection. N. Engl. J. Med. 335:1956. genes. Science 259:1739. gene-disrupted mice. J. Exp. Med. 178:2243. in resistance to Mycobacterium tuberculosis infection. J. Exp. Med. 178:2249. receptor have profoundly altered responses to infection with bacillus Calmette-Guérin and subsequent challenge with lipopolysaccharide. J. Exp. Med. 178:1435. and nitric oxide synthase 2. J. Exp. Med. 192:347. treated murine macrophages inhibit growth of tubercle bacilli via generation of reactive nitrogen intermediates. Cell. Immunol. 132:150.[Medline]
in the differentiation of protective granulomas. Eur. J. Immunol. 27:3182.[Medline]
in the host defense against M. bovis BCG. Eur. J. Immunol. 31:1935.[Medline]
is essential for the control of an intracellular bacterial infection. J. Exp. Med. 193:239. receptor in host defense against Mycobacterium bovis BCG infection. Eur. J. Immunol. 29:4002.[Medline]
from cells. Nature 385:729.[Medline]
. Nature 385:733.[Medline]
-deficient mice: a critical requirement for TNF in the formation of primary B cell follicles, follicular dendritic cell networks and germinal centers, and in the maturation of the humoral immune response. J. Exp. Med. 184:1397. (TNF) mediates effects distinct from those of wild-type TNF in vitro and in vivo. J. Biol. Chem. 274:38112. double-deficient mice. Int. Immunol. 8:23.-deficient mice. Nature 382:462.[Medline]
in Mycobacterium-induced granuloma formation in tumor necrosis factor--deficient mice. Lab. Invest. 79:379.[Medline]
on activated CD4+ T cell clones provides a costimulatory signal for human B cell activation. J. Exp. Med. 177:1575. interferon, tumor necrosis factor, and direct cell contact in activation of antimycobacterial defense in murine macrophages. Infect. Immun. 61:3901. is involved in the polyclonal B-cell activation induced by HIV-infected human T cells. Nature 363:464.[Medline]
is required in the protective immune response against Mycobacterium tuberculosis in mice. Immunity 2:561.[Medline]
is a determinant of pathogenesis and disease progression in mycobacterial infection in the central nervous system. Proc. Natl. Acad. Sci. USA 96:5657. (TNF-) and TNF- receptors during human endotoxemia. Blood 94:2252.This article has been cited by other articles:
|
|
 |
|
  H. Shibata, Y. Yoshioka, A. Ohkawa, K. Minowa, Y. Mukai, Y. Abe, M. Taniai, T. Nomura, H. Kayamuro, H. Nabeshi, et al. Creation and X-ray Structure Analysis of the Tumor Necrosis Factor Receptor-1-selective Mutant of a Tumor Necrosis Factor-{alpha} Antagonist J. Biol. Chem., January 11, 2008; 283(2): 998 - 1007. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. C. Cowley, J. D. Sedgwick, and K. L. Elkins Differential Requirements by CD4+ and CD8+ T Cells for Soluble and Membrane TNF in Control of Francisella tularensis Live Vaccine Strain Intramacrophage Growth J. Immunol., December 1, 2007; 179(11): 7709 - 7719. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Spohn, R. Guler, P. Johansen, I. Keller, M. Jacobs, M. Beck, F. Rohner, M. Bauer, K. Dietmeier, T. M. Kundig, et al. A Virus-Like Particle-Based Vaccine Selectively Targeting Soluble TNF-{alpha} Protects from Arthritis without Inducing Reactivation of Latent Tuberculosis J. Immunol., June 1, 2007; 178(11): 7450 - 7457. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Rutschmann, K. Hoebe, J. Zalevsky, X. Du, N. Mann, B. I. Dahiyat, P. Steed, and B. Beutler PanR1, a Dominant Negative Missense Allele of the Gene Encoding TNF-{alpha} (Tnf), Does Not Impair Lymphoid Development. J. Immunol., June 15, 2006; 176(12): 7525 - 7532. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. Musicki, H. Briscoe, S. Tran, W. J. Britton, and B. M. Saunders Differential Requirements for Soluble and Transmembrane Tumor Necrosis Factor in the Immunological Control of Primary and Secondary Listeria monocytogenes Infection. Infect. Immun., June 1, 2006; 74(6): 3180 - 3189. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. Torres, L. Janot, V. F.J. Quesniaux, S. I. Grivennikov, I. Maillet, J. D. Sedgwick, B. Ryffel, and F. Erard Membrane Tumor Necrosis Factor Confers Partial Protection to Listeria Infection Am. J. Pathol., December 1, 2005; 167(6): 1677 - 1687. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. W. Spahn, H.-P. Eugster, A. Fontana, W. Domschke, and T. Kucharzik Role of Lymphotoxin in Experimental Models of Infectious Diseases: Potential Benefits and Risks of a Therapeutic Inhibition of the Lymphotoxin-{beta} Receptor Pathway Infect. Immun., November 1, 2005; 73(11): 7077 - 7088. [Full Text] [PDF]
|
|
|
|
 |
|
 J. Keane TNF-blocking agents and tuberculosis: new drugs illuminate an old topic Rheumatology, June 1, 2005; 44(6): 714 - 720. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. M. Saunders, S. Tran, S. Ruuls, J. D. Sedgwick, H. Briscoe, and W. J. Britton Transmembrane TNF Is Sufficient to Initiate Cell Migration and Granuloma Formation and Provide Acute, but Not Long-Term, Control of Mycobacterium tuberculosis Infection J. Immunol., April 15, 2005; 174(8): 4852 - 4859. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. L. Olleros, R. Guler, D. Vesin, R. Parapanov, G. Marchal, E. Martinez-Soria, N. Corazza, J.-C. Pache, C. Mueller, and I. Garcia Contribution of Transmembrane Tumor Necrosis Factor to Host Defense against Mycobacterium bovis Bacillus Calmette-Guerin and Mycobacterium tuberculosis Infections Am. J. Pathol., April 1, 2005; 166(4): 1109 - 1120. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Goto, A. Ishizaka, F. Kobayashi, M. Kohno, M. Sawafuji, S. Tasaka, E. Ikeda, Y. Okada, I. Maruyama, and K. Kobayashi Importance of Tumor Necrosis Factor-{alpha} Cleavage Process in Post-Transplantation Lung Injury in Rats Am. J. Respir. Crit. Care Med., December 1, 2004; 170(11): 1239 - 1246. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S Ehlers Role of tumour necrosis factor (TNF) in host defence against tuberculosis: implications for immunotherapies targeting TNF Ann Rheum Dis, November 1, 2003; 62(90002): ii37 - 42. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. C. Cowley and K. L. Elkins Multiple T Cell Subsets Control Francisella tularensis LVS Intracellular Growth Without Stimulation Through Macrophage Interferon {gamma} Receptors J. Exp. Med., August 4, 2003; 198(3): 379 - 389. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
