CNS cell populations are protected from virus-induced pathology by distinct arms of the immune system

Neuropeptide Y has a protective role during murine retrovirus-induced neurological disease

Viral infections in the central nervous system (CNS) can lead to neurological disease either directly by infection of neurons or indirectly through activation of glial cells and production of neurotoxic molecules. Understanding the effects of virus-mediated insults on neuronal responses and neurotrophic support is important in elucidating the underlying mechanisms of viral diseases of the CNS. In the current study, we examined the expression of neurotrophin- and neurotransmitter-related genes during infection of mice with neurovirulent polytropic retrovirus. In this model, virus-induced neuropathogenesis is indirect, as the virus predominantly infects macrophages and microglia and does not productively infect neurons or astrocytes. Virus infection is associated with glial cell activation and the production of proinflammatory cytokines in the CNS. In the current study, we identified increased expression of neuropeptide Y (NPY), a pleiotropic growth factor which can regulate both immune cells and neuronal cells, as a correlate with neurovirulent virus infection. Increased levels of Npy mRNA were consistently associated with neurological disease in multiple strains of mice and were induced only by neurovirulent, not avirulent, virus infection. NPY protein expression was primarily detected in neurons near areas of virus-infected cells. Interestingly, mice deficient in NPY developed neurological disease at a faster rate than wild-type mice, indicating a protective role for NPY. Analysis of NPY-deficient mice indicated that NPY may have multiple mechanisms by which it influences virus-induced neurological disease, including regulating the entry of virus-infected cells into the CNS.

Demyelinated axons and motor function are protected by genetic deletion of perforin in a mouse model of multiple sclerosis

Axon injury is a major determinant of the loss of neurological function in patients with multiple sclerosis. It is unclear, however, whether damage to axons is an obligatory consequence of demyelination or whether it is an independent process that occurs in the permissive environment of demyelinated lesions. Previous investigations into the role of CD8 T cells and perforin in the Theiler murine encephalomyelitis virus model of multiple sclerosis have used mouse strains resistant to Theiler murine encephalomyelitis virus infection. To test the role of CD8 T cells in axon injury, we established a perforin-deficient mouse model on the H-2 major histocompatibility complex background thereby removing confounding factors related to viral biology in this Theiler murine encephalomyelitis virus-susceptible strain. This permitted direct comparison of clinical and pathological parameters between perforin-competent and perforin-deficient mice. The extent of demyelination was indistinguishable between perforin-competent and perforin-deficient H-2 mice, but chronically infected perforin-deficient mice exhibited preservation of motor function and spinal axons despite the presence of spinal cord demyelination. Thus, demyelination is necessary but insufficient for axon injury in this model; the absence of perforin protects axons without impacting demyelination. These results suggest that perforin is a key mediator of axon injury and lend additional support to the hypothesis that CD8 T cells are primarily responsible for axon damage in multiple sclerosis.

Tumor necrosis factor alpha is reparative via TNFR2 [corrected] in the hippocampus and via TNFR1 [corrected] in the striatum after virus-induced encephalitis

Differentiating between injurious and reparative factors facilitates appropriate therapeutic intervention. We evaluated the role of tumor necrosis factor alpha (TNFalpha) in parenchymal brain pathology resolution following virus-induced encephalitis from a picornavirus, Theiler's murine encephalomyelitis virus (TMEV). We infected the following animals with TMEV for 7 to 270 days: B6/129 TNF(-/-) mice (without TNFalpha expression), B6/129 TNFR1(-/-) mice (without TNFalpha receptor 1 expression), and B6/129 TNFR2(-/-) mice (without TNFalpha receptor 2 expression). Normal TNFalpha-expressing controls were TMEV-infected B6, 129/J, B6/129F1 and B6/129F2 mice. Whereas all strains developed inflammation and neuronal injury in the hippocampus and striatum 7 to 21 days postinfection (dpi), the control mice resolved the pathology by 45 to 90 dpi. However, parenchymal hippocampal and striatal injury persisted in B6/129 TNF(-/-) mice following infection. Treating virus-infected mice with active recombinant mouse TNFalpha resulted in less hippocampal and striatal pathology, whereas TNFalpha-neutralizing treatment worsened pathology. T1 "black holes" appeared on MRI during early infection in the hippocampus and striatum in all mice but persisted only in TNF(-/-) mice. TNFR2 [corrected] mediated hippocampal pathology resolution whereas TNFR1 [corrected] mediated striatal healing. These findings indicate the role of TNFalpha in resolution of sublethal hippocampal and striatal injury.

Interleukin 22 is a candidate gene for Tmevp3, a locus controlling Theiler's virus-induced neurological diseases

After intracerebral inoculation, Theiler's virus induces in its natural host, the mouse, an acute encephalomyelitis followed, in susceptible animals, by chronic inflammation and primary demyelination. Susceptibility to demyelination among strains of laboratory mice is explained by the capacity of the immune system to control viral load during persistence. Also, differences of susceptibility to viral load between the susceptible SJL strain and the resistant B10.S strain are mainly due to two loci, Tmevp2 and Tmevp3, located close to the Ifng locus on chromosome 10. In this article, we show that the Tmevp3 locus controls both mortality during the acute encephalomyelitis and viral load during persistence. Most probably, two genes located in the Tmevp3 interval control these two different phenotypes with efficiencies that depend on the age of the mouse at inoculation. Il22, a member of the IL-10 cytokine family, is a candidate gene for the control of mortality during the acute encephalomyelitis.

Genetic deletion of a single immunodominant T-cell response confers susceptibility to virus-induced demyelination

An important question in neuropathology involves determining the antigens that are targeted during demyelinating disease. Viral infection of the central nervous system (CNS) leads to T‐cell responses that can be protective as well as pathogenic. In the Theiler’s murine encephalomyelitis virus (TMEV) model of demyelination it is known that the immune response to the viral capsid protein 2 (VP2) is critical for disease pathogenesis. This study shows that expressing the whole viral capsid VP2 or the minimal CD8‐specific peptide VP2_121‐130 as “self” leads to a loss of VP2‐specific immune responses. Loss of responsiveness is caused by T cell‐specific tolerance, as VP2‐specific antibodies are generated in response to infection. More importantly, these mice lose the CD8 T‐cell response to the immunodominant peptide VP2_121‐130, which is critical for the development of demyelinating disease. The transgenic mice fail to clear the infection and develop chronic demyelinating disease in the spinal cord white matter. These findings demonstrate that T‐cell responses can be removed by transgenic expression and that lack of responsiveness alters viral clearance and CNS pathology. This model will be important for understanding the mechanisms involved in antigen‐specific T‐cell deletion and the contribution of this response to CNS pathology.

A new humanized HLA transgenic mouse model of multiple sclerosis expressing class II on mouse CD4 T cells

Among all the genetic factors associated with susceptibility to multiple sclerosis (MS), the strongest association has been seen with expression of certain major histocompatibility complex (MHC) class II molecules, although analysis of their exact function remains complicated. In general, the expression of class II is restricted to professional antigen-presenting cells; however, human but not mouse CD4+ T cells express class II on their surface. Functional studies of class II+ CD4+ T cells have been hampered due to lack of a proper animal model. Here, we describe development and characterization of a new humanized class II transgenic (tg) mouse expressing HLA-DR3 on mouse endogenous class II-negative background.

Role of MHC class II expressing CD4+ T cells in proteolipid protein(91-110)-induced EAE in HLA-DR3 transgenic mice

MHC class II molecules play a central role in the control of adaptive immune responses through selection of the CD4(+) T cell repertoire in the thymus and antigen presentation in the periphery. Inherited susceptibility to autoimmune disorders such as multiple sclerosis, rheumatoid arthritis and IDDM are associated with particular MHC class II alleles. Advent of HLA transgenic mice has helped us in deciphering the role of particular HLA DR and DQ class II molecules in human autoimmune diseases. In mice, the expression of class II is restricted to professional antigen-presenting cells (APC). However, in humans, class II is also expressed on T cells, unlike murine T cells. We have developed new humanized HLA class II transgenic mice expressing class II molecules not only on APC but also on a subset of CD4(+) T cells. The expression of class II on CD4(+) T cells is inducible, and class II(+) CD4(+) T cells can present antigen in the absence of APC. Further, using EAE, a well-established animal model of MS, we tested the functional significance of these class II(+) CD4(+) T cells. DR3.AEo transgenic mice were susceptible to proteolipid protein(91-110)-induced EAE and showed CNS pathology accompanied by widespread inflammation and demyelination seen in human MS patients, suggesting a role for class II(+) CD4(+) T cells in the pathogenesis.

Absence of perforin expression confers axonal protection despite demyelination

Current evidence suggests that demyelination may be a necessary but not a sufficient condition for neurologic deficits associated with multiple sclerosis. Axon injury that occurs within the permissive environment of the demyelinated lesion is better correlated with functional deficits, but the mechanisms and cellular effectors of this injury are largely unknown. In an effort to identify potential axon injury mediators, we examined demyelination, motor function, and the number of spinal axons in perforin-deficient mice. Perforin is a critical molecular mediator of cytotoxic immunological injury and we hypothesized that genetic deletion of perforin expression would protect demyelinated axons. Indeed, we found that while perforin-deficient mice had considerable spinal cord demyelination 180 days after infection with Theiler's murine encephalomyelitis virus, such mice exhibited functional and axonal preservation comparable to non-demyelinated perforin-competent controls. We conclude that perforin-dependent effector cells such as cytotoxic T cells, gammadelta T cells, and natural killer cells may play a role in axon damage that is dependent upon but separable from demyelination.

Injection of the sciatic nerve with TMEV: a new model for peripheral nerve demyelination

Demyelination of the human peripheral nervous system (PNS) can be caused by diverse mechanisms including viral infection. Despite association of several viruses with the development of peripheral demyelination, animal models of the condition have been limited to disease that is either autoimmune or genetic in origin. We describe here a model of PNS demyelination based on direct injection of sciatic nerves of mice with the cardiovirus, Theiler's murine encephalomyelitis virus (TMEV). Sciatic nerves of FVB mice develop inflammatory cell infiltration following TMEV injection. Schwann cells and macrophages are infected with TMEV. Viral replication is observed initially in the sciatic nerves and subsequently the spinal cord. Sciatic nerves are demyelinated by day 5 post-inoculation (p.i.). Injecting sciatic nerves of scid mice resulted in increased levels of virus recovered from the sciatic nerve and spinal cord relative to FVB mice. Demyelination also occurred in scid mice and by 12 days p.i., hindlimbs were paralyzed. This new model of virus-induced peripheral demyelination may be used to dissect processes involved in protection of the PNS from viral insult and to study the early phases of lesion development.

CD40L is critical for protection from demyelinating disease and development of spontaneous remyelination in a mouse model of multiple sclerosis

Theiler's murine encephalomyelitis virus (TMEV) induces acute neuronal disease followed by chronic demyelination in susceptible strains of mice. In this study we examined the role of a limited immune defect (deletion or blocking of CD40 ligand [CD40L]) on the extent of brain disease, susceptibility to demyelination, and the ability of demyelinated mice to spontaneously remyelinate following TMEV infection. We demonstrated that CD40L-dependent immune responses participate in pathogenesis in the cerebellum and the spinal cord white matter but protect the striatum of susceptible SJL/J mice. In mice on a background resistant to TMEV-induced demyelination (C57BL/6), the lack of CD40L resulted in increased striatal disease and meningeal inflammation. In addition, CD40L was required to maintain resistance to demyelination and clinical deficits in H-2b mice. CD40L-mediated interactions were also necessary for development of protective H-2b-restricted cytotoxic T cell responses directed against the VP2 region of TMEV as well as for spontaneous remyelination of the spinal cord white matter. The data presented here demonstrated the critical role of this molecule in both antibody- and cell-mediated protective immune responses in distinct phases of TMEV-mediated pathology.

Direct comparison of demyelinating disease induced by the Daniel's strain and BeAn strain of Theiler's murine encephalomyelitis virus

We compared CNS disease following intracerebral injection of SJL mice with Daniel's (DA) and BeAn 8386 (BeAn) strains of Theiler's murine encephalomyelitis virus (TMEV). In tissue culture, DA was more virulent then BeAn. There was a higher incidence of demyelination in the spinal cords of SJL/J mice infected with DA as compared to BeAn. However, the extent of demyelination was similar between virus strains when comparing those mice that developed demyelination. Even though BeAn infection resulted in lower incidence of demyelination in the spinal cord, these mice showed significant brain disease similar to that observed with DA. There was approximately 100 times more virus specific RNA in the CNS of DA infected mice as compared to BeAn infected mice. This was reflected by more virus antigen positive cells (macrophages/microglia and oligodendrocytes) in the spinal cord white matter of DA infected mice as compared to BeAn. There was no difference in the brain infiltrating immune cells of DA or BeAn infected mice. However, BeAn infected mice showed higher titers of TMEV specific antibody. Functional deficits as measured by Rotarod were more severe in DA infected versus BeAn infected mice. These findings indicate that the diseases induced by DA or BeAn are distinct.

STAT4- and STAT6-signaling molecules in a murine model of multiple sclerosis

Epidemiological studies suggest that an environmental factor (possibly a virus) acquired early in life may trigger multiple sclerosis (MS). The virus may remain dormant in the central nervous system but then becomes activated in adulthood. All existing models of MS are characterized by inflammation or demyelination that follows days after virus infection or antigen inoculation. While investigating the role of CD4+ T cell responses following Theiler's virus infection in mice deficient in STAT4 or STAT6, we discovered a model in which virus infection was followed by demyelination after a very prolonged incubation period. STAT4-/- mice were resistant to demyelination for 180 days after infection, but developed severe demyelination after this time point. Inflammatory cells and up-regulation of Class I and Class II MHC antigens characterized these lesions. Virus antigen was partially controlled during the early chronic phase of the infection even though viral RNA levels remained high throughout infection. Demyelination correlated with the appearance of virus antigen expression. Bone marrow reconstitution experiments indicated that the mechanism of the late onset demyelination was the result of the STAT4-/- immune system. Thus, virus infection of STAT4-/- mice results in a model that may allow for dissection of the immune events predisposing to late-onset demyelination in MS.

HLA DR and DQ interaction in myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis in HLA class II transgenic mice

Multiple sclerosis (MS) is shown to be associated with the HLA class II genes. The presence of strong linkage disequilibrium between HLA DR and DQ molecules in humans makes it difficult to identify the individual roles of HLA DR and HLA DQ molecule in MS pathogenesis. To address this problem, we used HLA class II transgenic mice and the experimental autoimmune encephalitis (EAE) model. Administration of recombinant MOG (rMOG) induced severe inflammation and demyelination in the central nervous system (CNS) of HLA DRB1*1502 mice (60%), whereas no disease was observed in HLA DQB1*0601(0%) and mild disease was observed in DQB1*0302 mice (13%). Lymphocyte proliferation was blocked by anti HLA antibodies, confirming that the rMOG was functionally presented by the HLA molecules. Introduction of DQB1*0302 into DRB1*1502 mice resulted in the development of chronic progressive clinical disease characterized by severe inflammation and demyelination (90%) in response to immunization with rMOG, whereas mild disease was observed when DQB1*0601 was introduced in DRB1*1502 mice (30%). This would suggest that the presence of more than one susceptible allele, namely HLA DRB1*1502 and DQB1*0302 resulted in enhanced severity of disease in the DRB1*1502/DQB1*0302 mice, possibly due to the additional selection and expansion of potential autoreactive T cells. The use of defined single and double HLA transgenic mice may reveal the intricate interactions between class II molecules in human disease.

Delineation of the minimal encephalitogenic epitope of proteolipid protein peptide(91-110) and critical residues required for induction of EAE in HLA-DR3 transgenic mice

Previously, we have reported that proteolipid protein (PLP) peptide 91-110 can induce experimental autoimmune encephalomyelitis (EAE) in HLA-DR3 transgenic (tg) mice. Here we, report that residues spanning 97-108 are the minimal epitope required for induction of EAE in DR3 mice. Utilizing a series of alanine-substituted peptides, positions 99, 101, 102, 103, 104, and 106 are identified as residues necessary for an immune response. Further analysis indicated that amino acid isoleucine (99), aspartate (102) and lysine (104) are anchor residues facilitating binding to HLA-DR3 molecules. These results may have applications in the future design of peptide based immunotherapy.

Gamma interferon is critical for neuronal viral clearance and protection in a susceptible mouse strain following early intracranial Theiler's murine encephalomyelitis virus infection

We evaluated the role of gamma interferon (IFN-gamma) in protecting neurons from virus-induced injury following central nervous system infection. IFN-gamma(-/-) and IFN-gamma(+/+) mice of the resistant major histocompatibility complex (MHC) H-2(b) haplotype and intracerebrally infected with Theiler's murine encephalomyelitis virus (TMEV) cleared virus infection from anterior horn cell neurons. IFN-gamma(+/+) H-2(b) mice also cleared virus from the spinal cord white matter, whereas IFN-gamma(-/-) H-2(b) mice developed viral persistence in glial cells of the white matter and exhibited associated spinal cord demyelination. In contrast, infection of IFN-gamma(-/-) mice of the susceptible H-2(q) haplotype resulted in frequent deaths and severe neurologic deficits within 16 days of infection compared to the results obtained for controls. Morphologic analysis demonstrated severe injury to spinal cord neurons in IFN-gamma(-/-) H-2(q) mice during early infection. More virus RNA was detected in the brain and spinal cord of IFN-gamma(-/-) H-2(q) mice than in those of control mice at 14 and 21 days after TMEV infection. Virus antigen was localized predominantly to anterior horn cells in infected IFN-gamma(-/-) H-2(q) mice. IFN-gamma deletion did not affect the humoral response directed against the virus. However, the level of expression of CD4, CD8, class I MHC, or class II MHC in the central nervous system of IFN-gamma(-/-) H-2(q) mice was lower than those in IFN-gamma(+/+) H-2(q) mice. Finally, in vitro analysis of virus-induced death in NSC34 cells and spinal motor neurons showed that IFN-gamma exerted a neuroprotective effect in the absence of other aspects of the immune response. These data support the hypothesis that IFN-gamma plays a critical role in protecting spinal cord neurons from persistent infection and death.

Interleukin-6 protects anterior horn neurons from lethal virus-induced injury

We evaluated the role of interleukin-6 (IL-6) in neuronal injury after CNS infection. IL-6-/- and IL-6+/+ mice of resistant major histocompatibility complex (MHC) H-2b haplotype intracerebrally infected with Theiler's virus cleared the infection normally without development of viral persistence, lethal neuronal infection, or late phase demyelination. In contrast, infection of IL-6-/- mice on a susceptible H-2q haplotype resulted in frequent deaths and severe neurologic deficits within 2 weeks of infection as compared with infected IL-6+/+ H-2q littermate controls. Morphologic analysis demonstrated dramatic injury to anterior horn neurons of IL-6-/- H-2q mice at 12 d after infection. Infectious viral titers in the CNS (brain and spinal cord combined) were equivalent between IL-6-/- H-2q and IL-6+/+ H-2q mice. In contrast, more viral RNA was detected in the spinal cord of IL-6-/- mice compared with IL-6+/+ H-2q mice. Virus antigen was localized predominantly to anterior horn cells in infected IL-6-/- H-2q mice. IL-6 deletion did not affect the humoral response directed against virus, nor did it affect the expression of CD4, CD8, MHC class I, or MHC class II in the CNS. Importantly, IL-6 was expressed by astrocytes of infected IL-6+/+ mice but not in astrocytes of IL-6-/- mice or uninfected IL-6+/+ mice. Furthermore, expression of various chemokines was robust at 12 d after infection in both H-2b and H-2q IL-6-/- mice, indicating that intrinsic CNS inflammatory responses did not depend on the presence of IL-6. Finally, in vitro analysis of virus-induced death in neuroblastoma-spinal cord-34 motor neurons and primary anterior horn cell neurons showed that IL-6 exerted a neuroprotective effect. These data support the hypothesis that IL-6 plays a critical role in protecting specific populations of neurons from irreversible injury.

Interleukin-6 protects anterior horn neurons from lethal virus-induced injury

We evaluated the role of interleukin-6 (IL-6) in neuronal injury after CNS infection. IL-6-/- and IL-6+/+ mice of resistant major histocompatibility complex (MHC) H-2b haplotype intracerebrally infected with Theiler's virus cleared the infection normally without development of viral persistence, lethal neuronal infection, or late phase demyelination. In contrast, infection of IL-6-/- mice on a susceptible H-2q haplotype resulted in frequent deaths and severe neurologic deficits within 2 weeks of infection as compared with infected IL-6+/+ H-2q littermate controls. Morphologic analysis demonstrated dramatic injury to anterior horn neurons of IL-6-/- H-2q mice at 12 d after infection. Infectious viral titers in the CNS (brain and spinal cord combined) were equivalent between IL-6-/- H-2q and IL-6+/+ H-2q mice. In contrast, more viral RNA was detected in the spinal cord of IL-6-/- mice compared with IL-6+/+ H-2q mice. Virus antigen was localized predominantly to anterior horn cells in infected IL-6-/- H-2q mice. IL-6 deletion did not affect the humoral response directed against virus, nor did it affect the expression of CD4, CD8, MHC class I, or MHC class II in the CNS. Importantly, IL-6 was expressed by astrocytes of infected IL-6+/+ mice but not in astrocytes of IL-6-/- mice or uninfected IL-6+/+ mice. Furthermore, expression of various chemokines was robust at 12 d after infection in both H-2b and H-2q IL-6-/- mice, indicating that intrinsic CNS inflammatory responses did not depend on the presence of IL-6. Finally, in vitro analysis of virus-induced death in neuroblastoma-spinal cord-34 motor neurons and primary anterior horn cell neurons showed that IL-6 exerted a neuroprotective effect. These data support the hypothesis that IL-6 plays a critical role in protecting specific populations of neurons from irreversible injury.

ICAM-1 is crucial for protection from TMEV-induced neuronal damage but not demyelination

Previous work has suggested that the factors protecting mice from Theiler's murine encephalomyelitis virus (TMEV)-induced spinal cord demyelination are distinct from those involved in protection of the brain during the acute encephalitic phase. In this study, we examined the requirement for intercellular adhesion molecule-1 (ICAM-1) in both of these processes. During the acute phase of infection (days 7 to 10 after intracerebral infection with TMEV), no differences in brain or spinal cord pathology or virus burdens were observed between ICAM-1-knockout mice and the infected immunocompetent control mice of a similar background. Examination of brain pathology later in infection (that is, day 45 post infection [p.i.]) revealed that ICAM-1-deficient mice experienced increased levels of pathology in gray matter regions of the brain. We observed an increase in striatal damage and meningeal inflammation in the brains of TMEV-infected ICAM-1-knockout mice compared to C57BL/6J mice. Despite the increase in brain pathology, no immunoreactivity to viral antigens was detected, suggesting that the virus had been cleared by this time. Resistance to demyelination was similar in both groups, indicating that the resulting immune response was sufficient for protection of the spinal cord white matter.

HLA-DQ polymorphism influences progression of demyelination and neurologic deficits in a viral model of multiple sclerosis

The importance of genetic susceptibility in determining the progression of demyelination and neurologic deficits is a major focus in neuroscience. We studied the influence of human leukocyte antigen (HLA)-DQ polymorphisms on disease course and neurologic impairment in virus-induced demyelination. HLA-DQ6 or DQ8 was inserted as a transgene into mice lacking endogenous expression of MHC class I (beta(2)m) and class II (H2-A(beta)) molecules. Following Theiler's murine encephalomyelitis virus (TMEV) infection, we assessed survival, virus persistence, demyelination, and clinical disease. Mice lacking expression of endogenous class I and class II molecules (beta(2)m(o) Abeta(o) mice) died 3 to 4 weeks postinfection (p.i.) due to overwhelming virus replication in neurons. beta(2)m(o) Abeta(o) DQ6 and beta(2)m(o) Abeta(o) DQ8 mice had increased survival and decreased gray matter disease and virus replication compared to nontransgenic littermate controls. Both beta(2)m(o) Abeta(o) DQ6 and beta(2)m(o) Abeta(o) DQ8 mice developed chronic virus persistence in glial cells of the white matter of the spinal cord, with greater numbers of virus antigen-positive cells in beta(2)m(o) Abeta(o) DQ8 than in beta(2)m(o) Abeta(o) DQ6 mice. At day 45 p.i., the demyelinating lesions in the spinal cord of beta(2)m(o) Abeta(o) DQ8 were larger than those in the beta(2)m(o) Abeta(o) DQ6 mice. Earlier and more profound neurologic deficits were observed in beta(2)m(o) Abeta (o) DQ8 mice compared to beta(2)m(o) Abeta(o) DQ6 mice, although by 120 days p.i. both strains of mice showed similar extent of demyelination and neurologic deficits. Delayed-type hypersensitivity and antibody responses to TMEV demonstrated that the mice mounted class II-mediated cellular and humoral immune responses. The results are consistent with the hypothesis that rates of progression of demyelination and neurologic deficits are related to the differential ability of DQ6 and DQ8 transgenes to modulate the immune response and control virus.

V(beta)8(+) T cells protect from demyelinating disease in a viral model of multiple sclerosis

Previous studies illustrated the influence of T cell subsets on susceptibility or resistance to demyelination in the Theiler's murine encephalomyelitis virus (TMEV) model of multiple sclerosis. Genetic segregation analysis showed a correlation with disease phenotype in this model with particular V(beta) genes. In this study we investigated the contribution of specific V(beta) TCR to the pathogenesis of virus-induced demyelinating disease. Spectratype analysis of cells infiltrating the CNS early in infection demonstrated an over-representation of V(beta)8(+) T cells in mice expressing a susceptible H-2 haplotype. We infected transgenic mice expressing the V(beta)8.2 TCR directed against a non-TMEV antigen and found an increase in demyelinating disease in mice of either susceptible or resistant background compared with littermate controls. In addition, depletion studies with an anti-V(beta)8-specific antibody in both susceptible (B10.Q) and resistant (C57BL/6) mice resulted in increased demyelination. TCR analysis of VP2-specific cytotoxic T cell clones from mice with a resistant genotype identified only the V(beta)8.1 TCR, suggesting that limited T cell diversity is critical to TMEV clearance. Together, these results support a protective role for V(beta)8(+) T cells in virus-induced demyelinating disease.

Short ragweed allergen induces eosinophilic lung disease in HLA-DQ transgenic mice

The human leukocyte antigen (HLA) restriction of the IgE response to different allergens in humans has been a subject of numerous published studies. However, the role and contribution of specific HLA class II molecules in the pathogenesis of allergic airway inflammation are unknown and difficult to assess. HLA-DQ6 and HLA-DQ8 transgenic mice lacking endogenous mouse class II gene expression were actively immunized and later challenged intranasally with short ragweed (SRW) allergenic extract. The HLA-DQ transgenic mice developed pulmonary eosinophilia and lung tissue damage. We also found an increase in total protein (TP) level and IL-5 production in bronchoalveolar lavage (BAL) fluid and an increase in SRW-specific Th2-type immunoglobulins (IgG1, IgG2b) and total serum IgE levels. Under similar treatment, DQ-negative full-sib control mice were normal. The allergic response could be significantly inhibited or abrogated in HLA-DQ mice by systemic treatment with anti-DQ mAb. The in vivo responses of HLA-DQ6 and HLA-DQ8 mice showed differences in terms of levels of eosinophilia, BAL protein, IL-5 concentration, and lung hyperreactivity to inhaled methacholine. These findings demonstrate the crucial role for specific HLA-DQ molecules in SRW-specific CD4(+) T-cell activation and resulting recruitment of eosinophils into the airways.