| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Departments of
*
Neurology and
Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033; and
Departments of Laboratory Medicine and Immunobiology, Yale University School of Medicine, New Haven, CT 06510
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Pathogenesis of the JHM strain of mouse hepatitis virus (JHMV) provides a rodent model of an acute viral CNS infection, which progresses to a chronic infection associated with ongoing myelin loss (17, 18, 19), pathologically similar to the human demyelinating disease, multiple sclerosis. JHMV replicates in a variety of CNS cell types, which require distinct mechanisms of CD8+ T cell-mediated clearance during acute infection (20, 21, 22, 23, 24). The absence of detectable antiviral Ab before clearance of infectious virus indicates that Ab plays little or no role during acute infection (18, 24). Consistent with a redundant early role of Ab, JHMV is cleared from the CNS of B cell-deficient C57BL/6-Igh-6tm1Cgm (µMT) mice with kinetics similar to wild-type (wt) mice (25). The critical role for Ab in controlling persistent infection was revealed by viral recrudescence in the CNS of µMT mice, which was prevented by passive transfer of JHMV-specific Ab (25). However, subsequent analysis demonstrated severely reduced T cell responses in JHMV-infected µMT mice compared with wt mice (26), in striking contrast to other viral infections of µMT mice (5, 6, 7, 27, 28). Therefore, it is not clear whether JHMV persistence is solely controlled by antiviral Ab or is also dependent on the magnitude of the virus-specific T cell response. Another antiviral mechanism disrupted in these mice is the potential cytolysis of virus-infected cells by naive B cells, recently suggested as a B cell-mediated innate immune mechanism during JHMV pathogenesis (29). Such direct participation of B cells in JHMV clearance could potentially alter viral pathogenesis in the absence of Ab specific for the viral spike protein (S protein), which inhibits B cell-mediated cytolysis (29).
To discern the relative contributions of Ab and T cells and the role(s) of both B cells and lymphoid architecture in the control of acute and persistent JHMV infection within the CNS, JHMV pathogenesis was examined in three types of H-2d mice with distinct defects in the B cell compartment: 1) B cell-deficient JHD mice; 2) transgenic mice, designated mIgM, with a near normal splenic architecture and B cells that express surface IgM but are unable to secrete antiviral Ab; and 3) transgenic (m+s)IgM mice, which have surface IgM+ B cells but a limited secretory repertoire restricted to the IgM isotype (30). T cell activation following microbial infections or immunization of these mice is comparable to wt mice (31, 32, 33). Similar to infected µMT mice (25), JHMV was initially cleared from the CNS but subsequently reactivated in both B cell/Ab-deficient and Ab-only-deficient mice. However, in contrast to infected µMT mice, no defects within the T cell compartment were detected in H-2d B cell- or Ab-deficient mice. Nevertheless, even an intact virus-specific T cell response did not suffice to control virus reactivation. These results clearly demonstrate that maintenance of JHMV persistence within CNS glial cells is solely dependent upon antiviral Ab, reminiscent of Ab-mediated control of neuronal infection by Alphaviruses (14). No evidence for an Ab-independent antiviral function of B cells in vivo was detected. However, a novel innate role of B cells in subverting viral infection to a cell type less susceptible to T cell-mediated regulation was revealed by the restriction of virus replication to specific CNS resident cell types in B cell+ Ab-deficient mice during reemergence. In summary, the data provide compelling evidence that two separate effectors regulate virus replication during acute infection and maintenance of viral persistence, i.e., cellular and humoral immunity, respectively.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
B cell-deficient mice homozygous for a disruption at the JH locus (JHD), backcrossed six times with BALB/c mice, were bred in an accredited animal facility at the University of Southern California (Los Angeles, CA) under pathogen-free conditions. The absence of B cells and Ig was confirmed by the inability to detect either CD19 or surface IgM cells by flow cytometry or serum Ig by ELISA. A transgene containing a rearranged VDJ region joined to an IgM H chain specific for the (4-hydroxy-3-nitrophenyl)acetyl hapten from which the secretory exon and polyadenylation site had been excised was used to produce transgenic mice (mIgM) with normal splenic architecture and B cell compartment. These transgenic mice express surface IgM but no circulating Ab (30) and were maintained by mating to JHD mice. An additional transgenic line, (m+s)IgM, similarly maintained by mating with JHD mice, expresses the IgM transgene as a secretory molecule and therefore contains a normal lymphoid architecture, surface IgM+ B cells, and a limited secretory IgM Ab repertoire, but no other isotypes (our unpublished observation). Both the mIgM and (m+s)IgM mice were identified by PCR as previously described (30). They both have approximately normal numbers of splenic B cells as determined by expression of CD19 and surface IgM. No antiviral IgG was detected in JHD mice or in mIgM and (m+s)IgM transgenic mice by ELISA following JHMV infection. Antiviral IgM was not detected until day 21 postinfection (p.i.) in (m+s)IgM-infected mice. Furthermore, the Ab titer in JHMV-infected (m+s)IgM-infected mice did not exceed 10% of that detected in wt BALB/c mice. No neutralizing activity was detected in the sera of JHMV-infected (m+s)IgM mice (data not shown). Age-matched wt BALB/c mice were purchased from the National Cancer Institute (Frederick, MD). Mice of both sexes were used between 7 and 8 wk of age.
Virus infection and titer determination
The J.2.2v-1 neutralization mAb-derived variant of neurotropic JHMV (34, 35) was injected intracerebrally in a volume of 30 µl containing 500 PFU. Tissue levels of infectious virus were determined from clarified homogenates prepared from one half brain by plaque assay on monolayers of delayed brain tumor cells as previously described (20, 21). Plaques were counted following 48 h incubation at 37°C and the data represent the average of duplicate determinations from groups of four or more mice.
Clinical disease
Clinical disease was scored as previously described (34, 35). Briefly, mice were graded as follows: 0, healthy; 1, ruffled hair and hunchbacked appearance; 2, reduced mobility and inability to upright; 3, paralysis and wasting; 4, death. Data represent averages of four mice per time point and are representative of three or more experiments for each group of mice.
Isolation of mononuclear cells
Mononuclear cells were isolated from spleen, cervical lymph nodes (CLN), and the CNS as previously described (20, 36, 37). Splenocytes and CLN cells were washed and resuspended in RPMI 1640 medium supplemented with 25 mM HEPES (pH 7.2) (RPMI-HEPES) before analysis. To isolate CNS-derived mononuclear cells (CMC), brains and spinal cords were removed, homogenized in RPMI-HEPES using Tenbroeck tissue homogenizers, and adjusted to 30% Percoll (Amersham Pharmacia Biotech, Piscataway, NJ). CMC were concentrated by centrifugation at 800 x g for 20 min at 4°C onto a 1-ml cushion of 70% Percoll. Cells were collected from the interface and washed twice in RPMI 1640 before analysis.
CTL assays
CMC were evaluated for ex vivo CTL-mediated cytolytic activity at days 9, 14, and 21 p.i. as previously described (20, 36, 37). Briefly, J774.1 (H-2d) target cells were labeled with Na51CrO4. The Ld-restricted, immunodominant nucleocapsid protein-derived peptide, designated pN (APTAGAFFF, Ref. 38), was added at 1 µM to labeled target cells before addition of CMC at various E:T ratios. 51Cr release was determined in 100 µl of supernatant following a 4-h incubation at 37°C. Specific lysis is defined as 100 x ((experimental release - spontaneous release)/(detergent release - spontaneous release)). Spontaneous release values were < 20% of total release in all experiments.
Flow cytometry
Cells obtained from spleen, CLN, and CNS were analyzed by flow
cytometry for expression of cell surface molecules. Cells were
preincubated with a mixture (10%) of polyclonal mouse and human sera
(Atlanta Biologicals, Norcross, GA) and rat anti-mouse Fc
III/IIR
mAb (2.4G2; BD PharMingen, San Diego, CA) for 20 min on ice to
block nonspecific binding. PE-, FITC-, or CyChrome C-labeled mAb
specific for CD4 (GK1.5), CD8 (53.67), CD44 (IM7), CD62L (MEL-14), CD43
(S7), CD19 (1D3), B220 (RA3-6B2), and IgM (R6-60.2) were all obtained
from BD PharMingen. JHMV-specific CD8+ T cells
were identified by labeling with the Ld-pN class
I tetramer as previously described (36). Cells were
analyzed with a FACScan flow cytometer (BD Biosciences, San Jose, CA)
using CellQuest software.
ELISPOT analysis
Frequencies of JHMV-specific IFN--secreting
CD8+ and CD4+ T cells were
evaluated as previously described (36, 37). Briefly,
96-well plates (Millipore, Bedford, MA) were coated with purified
anti-IFN- mAb (R4.6A2; BD PharMingen) at 10 µg/ml overnight at
4°C. CD8+ T cells were stimulated on BALB/c
splenocytes (5 x 105 per well), irradiated
for 20 min at 2000 rad, in the presence or absence of 1 µM pN 9-mer
peptide and 2.5% EL-4 supernatant as a source of IL-2. A UV
light-inactivated lysate prepared from JHMV-infected delayed brain
tumor cells was used to stimulate CD4+ T
cells for a period of 36 h at 37°C. Plates were developed using
biotinylated anti-IFN- mAb (XMG1.2; BD PharMingen) overnight at
4°C, followed by streptavidin peroxidase and 3,3'-diaminobenzidine
(Sigma-Aldrich, St. Louis, MO) as substrate. Spots from two effector
cell dilutions (n = 6) were counted using a Leica
stereo microscope (Leica, Bannockburn, IL).
Histology
Brains bisected in the midcoronal plane and spinal cords were examined for inflammation, distribution of viral Ag, and myelin loss. Tissues were fixed for 3 h in Clark’s solution (75% ethanol, 25% glacial acetic acid) before embedding. Sections were stained with either H&E or luxol fast blue to determine inflammation and demyelination, respectively. Distribution of viral Ag was determined by immunoperoxidase staining (Vectastain-ABC kit; Vector Laboratories, Burlingame, CA) using the anti-JHMV mAb J.3.3 specific for the carboxyl terminus of the viral nucleocapsid protein as the primary Ab (39, 40) and horse anti-mouse as secondary Ab (Vector Laboratories). Sections were scored in a blinded fashion.
Statistical analysis
Results, presented as means ± SEM, were analyzed using a paired Student’s t test and ANOVA. A value of p < 0.05 indicated a statistically significant difference.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Viral recrudescence in the CNS of JHMV-infected B cell-deficient
µMT mice (25) may be attributed to severely reduced T
cell responses within the CNS compared with wt mice (26),
in addition to the absence of a humoral response. To dissect the
relative importance of these defects to JHMV reactivation, transgenic
mice containing B cells that either only express surface IgM but no
circulating Ab (mIgM), or secrete a limited repertoire restricted to
the IgM isotype ((m+s)IgM) (30), were infected and
compared with syngeneic mice devoid of B cells and wt mice. All groups
of mice survived the acute disease induced by JHMV infection (Fig. 1
A). However, in contrast to
100% survival of wt mice, >50% of JHD and mIgM
mice died between days 13 and 30 p.i. Similar results were
obtained for (m+s)IgM mice (data not shown). Mild clinical signs
initially developed at 8–9 days p.i. and progressed to more severe
wasting and hind limb paralysis in all groups (Fig. 1B).
Whereas clinical disease in wt mice improved after day 14 p.i., no
improvements were noted in any of the Ab-deficient mice (Fig. 1B). Thus the presence of B cells did not affect the
morbidity and mortality observed in all Ab-deficient groups.
Furthermore, the inability to secrete antiviral Ab, rather than the
mere presence of B cells, altered the clinical outcome of JHMV
persistence following resolution of acute disease.
|
C; days 5–12 p.i.). Although there
was little or no detectable virus in the CNS of
JHD, mIgM, and (m+s)IgM mice at days 12 or
14 p.i., virus recovery from these mice increased at days 21 and
30 p.i. (Fig. 1C), consistent with enhanced clinical
disease and mortality. Although virus appeared to reactivate more
slowly within the CNS of the mIgM and (m+s)IgM mice compared with the B
cell-deficient JHD mice (Fig. 1C), the
difference was not statistically significant. JHMV replication
continued to increase within the CNS of the limited number of survivors
in all three groups of Ab-deficient mice until day 45 p.i., the
last time point analyzed (data not shown). An Ab-independent innate B
cell function affecting acute virus replication (29) was
thus not evident in vivo. JHMV reactivation within the CNS of
Ab-deficient mice thus appears independent of genetic background,
lymphoid architecture, and the presence of B cells. These data support
the concept that antiviral Ab is critical for maintaining infectious
JHMV at undetectable levels during CNS persistence
(25).
The CNS of Ab-deficient and wt mice were compared during acute
infection to verify similar inflammatory responses and viral cell
tropism. Inflammatory cells were localized to both perivascular and
intraparenchymal areas at day 14 p.i.; the pattern of distribution
in all Ab-deficient groups was identical to that in JHMV-infected wt
mice (Fig. 2, A and
B). Similarly, viral Ag was detected in microglia,
astrocytes, and oligodendroglia in all three Ab-deficient groups
analogous to wt mice (Fig. 2, C and D). The
number and distribution of virus-infected cells (Fig. 2, C
and D), as well as demyelination (data not shown), were thus
similar in all four groups of mice. Thus, acute JHMV pathogenesis was
not altered by the absence of B cells, the inability to secrete
antiviral Ab, or the ability to secrete only a limited IgM
repertoire.
|
Frequencies of virus-specific T cells were measured in spleen and
CLN cells from infected JHD, mIgM, (m+s)IgM, and
wt H-2d mice to assess potential T cell defects,
which are clearly evident in JHMV-infected µMT mice
(26). Irrespective of the overall low frequency of
tetramer+ T cells within the spleen following
JHMV infection (36, 37), infected
JHD mice consistently had a significantly reduced
percentage of tetramer+ cells within splenic
CD8+ T cells at day 5 p.i. compared with
both wt and B cell+ Ab-deficient mice (Fig. 3A). However, none of the
H-2d Ab-deficient mice had significantly reduced
splenic tetramer+CD8+ T
cells after day 5 p.i. (Fig. 3A). Few
tetramer+CD8+ T cells were
detected in CLN of any group of JHMV-infected
H-2d mice (data not shown), consistent with
observations in other mouse strains (26, 33). IFN-
ELISPOT analysis of spleen and CLN cells confirmed a reduced frequency
of virus-specific CD8+ T cells only in infected
JHD mice but not in B cell+
mice (Fig. 3, B and D). In contrast to
CD8+ T cell responses, there were no differences
in the frequencies of virus-specific CD4+ T cells
in either the spleen or CLN during the acute infection in Ab-deficient
compared with wt mice (Fig. 3, C and D). These
data indicated that any potential role of B cells or lymphoid
architecture in regulating CD8+ T cell activation
can only be transiently observed at day 5 p.i. Therefore, in
contrast to JHMV-infected µMT mice (26), no peripheral
defects in the T cell compartment were detected following day 7
p.i. in either B cell- or Ab-deficient H-2d
mice.
|
); by day 14 p.i.
CD8+ T cells decreased in wt mice but not in the
Ab-deficient groups.
Tetramer+CD8+ T cells
within the CNS of all groups were similar (Fig. 4B). The CNS
of JHD mice even contained a slight increase in
tetramer+CD8+ T cells at
day 7 p.i. compared with B cell+
Ab-deficient mice. A trend toward increased recruitment/survival of
tetramer+CD8+ T cells in
all Ab-deficient groups was evident at day 14 p.i., when
CD8+ T cell percentages were only reduced in wt
mice; however, tetramer+ populations remained
similar in all groups. Recruitment of virus-specific
CD4+ and CD8+ T cells into
the CNS was confirmed by IFN- ELISPOT analysis (Fig. 4, C
and D). Surprisingly, all Ab-deficient groups revealed
higher frequencies of virus-specific IFN--secreting
CD8+ T cells in the CNS compared with wt mice
throughout days 7–14 p.i. Nevertheless, all frequencies progressively
declined during viral clearance. The apparent discrepancy between
phenotypic (tetramer+) and functional (IFN-
secretion) analysis may indicate down-regulation of
CD8+ T cell effector function as virus is cleared
(20, 36, 37). Frequencies of virus-specific
CD4+ T cells were also higher in Ab-deficient
mice compared with wt mice throughout days 7–14 p.i. (Fig. 4),
with a relative decline evident by day 14 p.i., similar to
virus-specific CD8+ T cells. JHMV-infected
H-2d Ab-deficient mice thus revealed no
impairment in T cell activation, expansion, or recruitment into the
infected CNS, in contrast to the severely reduced virus-specific T
cells in the CNS of infected µMT mice (26). This was
also confirmed by phenotypic analysis, which showed equivalent
expression of activation/memory surface markers
(CD44highCD62LlowCD43+)
in both wt and Ab-deficient mice (data not shown).
|
).
Similar to the loss of this function concomitant with viral clearance
in wt mice (20, 26, 36, 37), ex vivo CTL activity declined
in all mice by day 14 p.i. (Fig. 5). Thus, both phenotypic and
functional analysis of CD8+ T cells within the
CNS of Ab-deficient mice suggest no defect in the ability of cytolytic
activity to contribute to viral clearance during acute infection.
|
The absence of an apparent T cell defect during acute infection of
JHD, mIgM, and (m+s)IgM mice provided the
opportunity to analyze the effect of JHMV reactivation on the T cell
compartment. At days 21 and 30 p.i. CMC yields were equal or
slightly reduced in Ab-deficient mice compared with wt mice.
CD8+ T cell populations within the CNS remained
relatively constant during virus reactivation between days 14 and
30 p.i.; a modest, albeit insignificant, decline was only evident
within the CNS of wt mice (Fig. 6A). There were also no
significant differences in frequencies of
tetramer+CD8+ T cells when
comparing the three Ab-deficient groups to wt mice at day 14 p.i.
However, between days 21 and 30, frequencies in wt mice had dropped
significantly compared with JHD and mIgM mice
(Fig. 6A). Thus, while
tetramer+CD8+ T cells
gradually declined after viral clearance in wt mice, they remained
elevated but did not increase in mice harboring recrudescing virus. To
address the possibility that tetramer+ cells were
underestimated due to Ag-induced TCR down-regulation, the frequencies
of IFN--secreting CD8+ T cells were assessed
by ELISPOT analysis. Overall, frequencies of IFN--responsive
CD8+ T cells within each group gradually
decreased between days 14 and 30 p.i., opposing the tetramer
analysis (Fig. 6B). The 
2-fold drop from day 14 to day
30 p.i. was significant not only in wt mice but in all
Ab-deficient mice. Furthermore, when comparing the groups to each other
at each time point,
IFN-+CD8+ T cell
frequencies were significantly lower in wt mice only at days 21 and
30 p.i. While the ratios of tetramer+ to
IFN-+CD8+ T cells were
the same for all groups at day 14 p.i. (5:1), they were higher in
all Ab-deficient groups by day 30 p.i., suggesting an increased
state of nonresponsiveness (Fig. 6B). Down-regulation of
effector function was supported by the inability to recover ex
vivo cytolytic activity from the CNS during virus reactivation (data
not shown). Thus, increasing Ag load within the CNS during virus
reactivation was not associated with enhanced recruitment of functional
virus-specific CD8+ T cells but rather resulted
in down-regulation of cytolytic activity and IFN- secretion.
|
C), irrespective of virus reactivation.
ELISPOT analysis revealed a statistically significant decline in
frequencies of virus-specific CD4+ T cells in wt,
mIgM, and (m+s)IgM mice between days 14 and 30 p.i., despite
increased Ag load in the CNS of the mIgM and (m+s)IgM mice. In stark
contrast, they were maintained within the CNS of
JHD mice (Fig. 6D). Thus,
IFN-+CD4+ T cells were
significantly higher in JHD mice compared with
all B cell+ mice at both days 21 and 30 p.i.
This surprising result suggests that the absence, rather than presence,
of B cells enhances virus-specific CD4+ T cell
function. Nevertheless, the overall absence of increased recruitment,
concomitant with an apparent decrease in IFN- secretion by both
CD4+ and CD8+ T cells
during virus reactivation in the CNS, suggests that T cells alone
cannot control persistent infection. An Ab-independent B cell mechanism limits persisting virus to oligodendrocytes
The observation that CD8+ T cells are
similarly down-regulated in all groups of mice, independent of viral
recrudescence or the presence of B cells, suggested that differential
regulation of CD4+ T cells in
JHD mice may reside in altered cytokine/chemokine
release or altered class II Ag presentation. Therefore, the CNS of
Ab-deficient mice were examined for the distribution of mononuclear
cell infiltrates, CNS demyelination, and virus cellular tropism during
JHMV reactivation. Increased inflammation was present in the CNS of all
Ab-deficient mice compared with wt mice (Fig. 7, A–C). However,
in contrast to acute infection (Fig. 2), the majority of mononuclear
cells were present within the CNS parenchyma. Demyelination was also
increased in the Ab-deficient mice compared with wt mice
(Fig. 7, D–F), consistent with demyelination
induced by actively replicating virus during acute infection
(17, 18, 19). Ab-deficient mice also exhibited increased
numbers of virus-infected CNS cells, most prominently in the spinal
cord, compared with wt mice (Fig. 7, G–I).
Neurons were not infected in any group. Despite the greater
number of Ag-positive cells in the CNS of JHD
compared with wt mice, the cell types infected, i.e., astrocytes and
oligodendroglia, were similar (Fig. 7, G and I).
In striking contrast to tropism of recrudescing virus in
JHD mice, oligodendroglia were the predominant
CNS cell type infected in both mIgM mice (Fig. 7H) and
(m+s)IgM mice (data not shown). Importantly, the decrease in
Ag-positive astrocytes was not counterbalanced by increased numbers of
infected oligodendrocytes. Similar numbers of Ag-positive
oligodendrocytes in B cell+ and B cell-deficient
recrudescing mice were consistent with similar severity of
demyelination. This restricted tropism for oligodendroglia in B
cell+ Ab-deficient mice suggests that the
presence of B cells contributes to virus clearance from astrocytes and
microglia. This Ab-independent clearance mechanism suggests a novel
role for B cells within the CNS, which manifests itself by limiting
infectious virus to oligodendroglia during reactivation.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
It is unclear whether the differential T cell responsiveness in infected JHD and µMT mice is due to the distinct gene segments targeted to deplete B cells (41, 42), or to haplotype-related differences. The first notion is supported by delayed clearance of rotavirus in infected µMT compared with JHD mice, both on the H-2b background (31). B cell deficiency also manifests itself differently during distinct infections. In contrast to JHMV infection, µMT mice mount normal CD8+ CTL responses following LCMV, influenza, and HSV infections (5, 6, 27, 28). Furthermore, neither acute nor memory CD4+ T cells are compromised following influenza virus infection of µMT mice (27), and murine mammary tumor virus superantigen responses in µMT mice are also comparable to wt mice (43). By contrast, CD4+ T cell responses to HSV and keyhole limpet hemocyanin are reduced in µMT mice (44, 45). These findings raise the possibility that differences affecting the CD4+ T cell compartment may lead to the distinct regulation of JHMV-specific T cells in infected µMT vs JHD mice (26). An indirect effect on CD4+ T cells, to explain discrepant T cell function in the absence of B cells, is supported by the fact that CD4+ T cells enhance JHMV-specific CD8+ T cell expansion and function (23, 26).
A role for B cell-mediated cytolysis (29) was examined in consideration of the delay in antiviral Ab responses in wt mice until after virus is essentially cleared from the CNS (18, 24). The ability of B cells from naive donors to lyse virus-infected cells through an interaction between the viral S protein and the viral receptor is unique to mouse hepatitis virus (29, 46). Although B cells express the mouse hepatitis virus receptor in vivo (29, 47), they appear resistant to infection in vivo based on the inability to detect viral Ag in lymphocytes (22, 23, 24). As cytolysis is inhibited by anti-S protein Ab (29, 47, 48), a B cell cytolytic mechanism in vivo can only be active before anti-S protein Ab secretion. However, similar kinetics of virus replication and clearance in mIgM, (m+s)IgM, and JHD mice argue against an innate immune function of B cells during acute infection, consistent with the limited recruitment of B cells into the CNS during acute infection (49).
However, preferential cellular tropism of recrudescing virus for
oligodendroglia in B cell+ Ab-deficient mice,
compared with astrocytes and oligodendroglia in
JHD mice, did uncover an apparent Ab-independent
role for B cells within the CNS during persistence. Oligodendroglial
tropism in both mIgM and (m+s)IgM mice suggests that the negligible
antiviral IgM response detected in the (m+s)IgM mice is insufficient to
mediate this effect. Furthermore, B cells only facilitate clearance of
reemerging virus from astrocytes and microglia/macrophages as the T
cell response wanes. Whether this mechanism involves direct B
cell-mediated cytolysis or an indirect effect of B cells on other cell
types is unclear. B cell cytolysis is solely dependent on viral S
protein expressed on target cells (29, 47, 48) but
independent of Fas-FasL interactions, perforin, and TNF-
in vitro
(29, 50). If a cytolytic mechanism is indeed functional in
vivo, it implies that oligodendroglia are resistant to B cell-mediated
lysis, reminiscent to their resistance to perforin-mediated cytolysis
by CD8+ T cells (24). Alternatively,
a potential indirect mechanism may involve enhanced
CD4+ T cell responses in the presence of B cells.
However, IFN--secreting virus-specific CD4+ T
cells decreased rather than increased in B cell+
mice compared with B cell-deficient JHD mice,
negating such a causal relationship. Although limited B cell lysis of
infected cells in B cell+ Ab-deficient mice
during recrudescence cannot be excluded, such B cell effector function
is unlikely to be active in immune-competent wt mice due to detection
of inhibiting antiviral Ab by approximately day 10 p.i. (18, 24).
The circuits linking altered tropism with antiviral B cell function and/or CD4+ T cell responsiveness remain elusive. As the CNS chemokine/cytokine profile is not only shaped by infiltrating cells but also by infected resident CNS cells (51), alterations in either compartment will potentially affect the other. B cells may thus potentially alter tropism directly via cytokine expression and/or via an indirect effect on CD4+ T cell function (52). Alternatively, enhanced CD4+ T cell survival/recruitment in JHD mice may result from 1) class II-mediated TCR stimulation by specific infected cell types, 2) MHC-independent recruitment factors produced by infected astrocytes and microglia/macrophages but not oligodendrocytes, and 3) the absence of potentially negative signals by B cells. The fact that only virus-specific CD4+ T cells, but not total CD4+ T cells, are enhanced favors a direct interaction with class II resident APC (10, 11, 12). These data further indicate that in contrast to infected astrocytes and microglia/macrophages, productively infected oligodendrocytes do not, or only inefficiently, present viral Ag to CD4+ T cells.
The most crucial finding relative to persistent viral infection of the
CNS is that reactivation does not result in increased inflammation,
increased virus-specific T cells, or re-expression of cytolytic
effector function. Both virus-specific CD4+ and
CD8+ T cells within the CNS retain the ability to
secrete in response to viral Ag. Although IFN- is crucial for viral
clearance during acute infection (24), this effector
function is evidently insufficient to control virus reactivation. The
inability to enhance T cell effector function may be due to a decreased
ability of peripheral T cells to access the CNS, the inability of Ag to
leave the CNS and reactivate peripheral T cells, Ag-induced anergy, or
T cell apoptosis. Irrespective of increased
tetramer+CD8+ T cells in
all recrudescing mice compared with wt mice, the overall decrease of
virus-specific IFN--secreting cells favors Ag-induced
down-regulation of T cell effector function. Initial clearance of
infectious virus thus appears to predispose the CNS to preempt further
T cell-mediated viral clearance. Such an altered CNS environment
emphasizes the need for Ab-mediated protection, particularly
after immune- or virus-induced CNS pathology. In summary, although
neither B cells nor antiviral Ab influence clearance during acute
infection, Ab inhibits viral recrudescence (25) and may,
in addition, be beneficial to completely eliminate infectious virus
during the waning T cell response, especially as
CD8+ T cells lose effector function (20, 36, 37).
|
Acknowledgments |
|---|
|
Footnotes |
|---|
2 Address correspondence and reprint requests to Dr. Cornelia C. Bergmann, Departments of Neurology and Pathology, Keck School of Medicine, University of Southern California, 1333 San Pablo Street, MCH 142, Los Angeles, CA 90033. E-mail address: cbergman{at}hsc.usc.edu
3 Abbreviations used in this paper: LCMV, lymphocytic choriomeningitis virus; CLN, cervical lymph node; CMC, CNS-derived mononuclear cell; JHMV, JHM strain of mouse hepatitis virus; p.i., postinfection; S protein, spike protein; wt, wild type.
Received for publication August 14, 2001. Accepted for publication December 3, 2001.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
is required for viral clearance from central nervous system oligodendroglia. J. Immunol. 162:1641.- and 
-chemokine expression in the central nervous system during mouse hepatitis virus-induced demyelinating disease. J. Immunol. 160:970.This article has been cited by other articles:
|
|
 |
|
  P. Kapil, R. Atkinson, C. Ramakrishna, D. J. Cua, C. C. Bergmann, and S. A. Stohlman Interleukin-12 (IL-12), but Not IL-23, Deficiency Ameliorates Viral Encephalitis without Affecting Viral Control J. Virol., June 15, 2009; 83(12): 5978 - 5986. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. W. Phares, C. Ramakrishna, G. I. Parra, A. Epstein, L. Chen, R. Atkinson, S. A. Stohlman, and C. C. Bergmann Target-Dependent B7-H1 Regulation Contributes to Clearance of Central Nervous Sysyem Infection and Dampens Morbidity J. Immunol., May 1, 2009; 182(9): 5430 - 5438. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Cervantes-Barragan, U. Kalinke, R. Zust, M. Konig, B. Reizis, C. Lopez-Macias, V. Thiel, and B. Ludewig Type I IFN-Mediated Protection of Macrophages and Dendritic Cells Secures Control of Murine Coronavirus Infection J. Immunol., January 15, 2009; 182(2): 1099 - 1106. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Nozaki, J. M. Rosenblum, D. Ishii, K. Tanabe, and R. L. Fairchild CD4 T Cell-Mediated Rejection of Cardiac Allografts in B Cell-Deficient Mice J. Immunol., October 15, 2008; 181(8): 5257 - 5263. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. J. Johnson, C.-F. Chu, and G. N. Milligan Effector CD4+ T-Cell Involvement in Clearance of Infectious Herpes Simplex Virus Type 1 from Sensory Ganglia and Spinal Cords J. Virol., October 1, 2008; 82(19): 9678 - 9688. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. A. Stohlman, D. R. Hinton, B. Parra, R. Atkinson, and C. C. Bergmann CD4 T Cells Contribute to Virus Control and Pathology following Central Nervous System Infection with Neurotropic Mouse Hepatitis Virus J. Virol., March 1, 2008; 82(5): 2130 - 2139. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. S. Butler, A. A. Dandekar, and S. Perlman Antiviral Antibodies Are Necessary To Prevent Cytotoxic T-Lymphocyte Escape in Mice Infected with a Coronavirus J. Virol., December 15, 2007; 81(24): 13291 - 13298. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Cervantes-Barragan, R. Zust, F. Weber, M. Spiegel, K. S. Lang, S. Akira, V. Thiel, and B. Ludewig Control of coronavirus infection through plasmacytoid dendritic-cell-derived type I interferon Blood, February 1, 2007; 109(3): 1131 - 1137. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. M. Brown, A. M. Dilzer, D. L. Meents, and S. L. Swain CD4 T cell-mediated protection from lethal influenza: perforin and antibody-mediated mechanisms give a one-two punch. J. Immunol., September 1, 2006; 177(5): 2888 - 2898. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Zhou and S. Perlman Preferential Infection of Mature Dendritic Cells by Mouse Hepatitis Virus Strain JHM J. Virol., March 1, 2006; 80(5): 2506 - 2514. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. M. Gonzalez, C. C. Bergmann, C. Ramakrishna, D. R. Hinton, R. Atkinson, J. Hoskin, W. B. Macklin, and S. A. Stohlman Inhibition of Interferon-{gamma} Signaling in Oligodendroglia Delays Coronavirus Clearance without Altering Demyelination Am. J. Pathol., March 1, 2006; 168(3): 796 - 804. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Ramakrishna, R. A. Atkinson, S. A. Stohlman, and C. C. Bergmann Vaccine-Induced Memory CD8+ T Cells Cannot Prevent Central Nervous System Virus Reactivation. J. Immunol., March 1, 2006; 176(5): 3062 - 3069. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. C. MacNamara, M. M. Chua, J. J. Phillips, and S. R. Weiss Contributions of the Viral Genetic Background and a Single Amino Acid Substitution in an Immunodominant CD8+ T-Cell Epitope to Murine Coronavirus Neurovirulence J. Virol., July 15, 2005; 79(14): 9108 - 9118. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Cepok, B. Rosche, V. Grummel, F. Vogel, D. Zhou, J. Sayn, N. Sommer, H.-P. Hartung, and B. Hemmer Short-lived plasma blasts are the main B cell effector subset during the course of multiple sclerosis Brain, July 1, 2005; 128(7): 1667 - 1676. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. M. Chen, N. Khanna, S. A. Stohlman, and C. C. Bergmann Virus-Specific and Bystander CD8 T Cells Recruited during Virus-Induced Encephalomyelitis J. Virol., April 15, 2005; 79(8): 4700 - 4708. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Ramakrishna, S. A. Stohlman, R. A. Atkinson, D. R. Hinton, and C. C. Bergmann Differential Regulation of Primary and Secondary CD8+ T Cells in the Central Nervous System J. Immunol., November 15, 2004; 173(10): 6265 - 6273. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. C. Bergmann, B. Parra, D. R. Hinton, C. Ramakrishna, K. C. Dowdell, and S. A. Stohlman Perforin and Gamma Interferon-Mediated Control of Coronavirus Central Nervous System Infection by CD8 T Cells in the Absence of CD4 T Cells J. Virol., February 15, 2004; 78(4): 1739 - 1750. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Kano, M. Inaoka, and T. Shiohara Association Between Anticonvulsant Hypersensitivity Syndrome and Human Herpesvirus 6 Reactivation and Hypogammaglobulinemia Arch Dermatol, February 1, 2004; 140(2): 183 - 188. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. S. Diamond, E. M. Sitati, L. D. Friend, S. Higgs, B. Shrestha, and M. Engle A Critical Role for Induced IgM in the Protection against West Nile Virus Infection J. Exp. Med., December 15, 2003; 198(12): 1853 - 1862. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. A. Dandekar, G. Jacobsen, T. J. Waldschmidt, and S. Perlman Antibody-Mediated Protection against Cytotoxic T-Cell Escape in Coronavirus-Induced Demyelination J. Virol., November 15, 2003; 77(22): 11867 - 11874. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. P. Christensen, S. O. Kauffmann, and A. R. Thomsen Deficient CD4+ T Cell Priming and Regression of CD8+ T Cell Functionality in Virus-Infected Mice Lacking a Normal B Cell Compartment J. Immunol., November 1, 2003; 171(9): 4733 - 4741. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Mpandi, L. A. Otten, C. Lavanchy, H. Acha-Orbea, and D. Finke Passive Immunization with Neutralizing Antibodies Interrupts the Mouse Mammary Tumor Virus Life Cycle J. Virol., September 1, 2003; 77(17): 9369 - 9377. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Ramakrishna, C. C. Bergmann, R. Atkinson, and S. A. Stohlman Control of Central Nervous System Viral Persistence by Neutralizing Antibody J. Virol., April 15, 2003; 77(8): 4670 - 4678. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. C. Bergmann, B. Parra, D. R. Hinton, R. Chandran, M. Morrison, and S. A. Stohlman Perforin-Mediated Effector Function Within the Central Nervous System Requires IFN-{gamma}-Mediated MHC Up-Regulation J. Immunol., March 15, 2003; 170(6): 3204 - 3213. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. S. Diamond, B. Shrestha, A. Marri, D. Mahan, and M. Engle B Cells and Antibody Play Critical Roles in the Immediate Defense of Disseminated Infection by West Nile Encephalitis Virus J. Virol., February 15, 2003; 77(4): 2578 - 2586. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. W. Marten, S. A. Stohlman, J. Zhou, and C. C. Bergmann Kinetics of Virus-Specific CD8+-T-Cell Expansion and Trafficking following Central Nervous System Infection J. Virol., February 15, 2003; 77(4): 2775 - 2778. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. Finke, S. A. Luther, and H. Acha-Orbea The role of neutralizing antibodies for mouse mammary tumor virus transmission and mammary cancer development PNAS, January 7, 2003; 100(1): 199 - 204. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. A. Dandekar and S. Perlman Virus-Induced Demyelination in Nude Mice Is Mediated by {gamma}{delta} T Cells Am. J. Pathol., October 1, 2002; 161(4): 1255 - 1263. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S.-I. Tschen, C. C. Bergmann, C. Ramakrishna, S. Morales, R. Atkinson, and S. A. Stohlman Recruitment Kinetics and Composition of Antibody-Secreting Cells Within the Central Nervous System Following Viral Encephalomyelitis J. Immunol., March 15, 2002; 168(6): 2922 - 2929. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
0.05).
