BALB/c substrain differences in susceptibility to Theiler's murine encephalomyelitis virus-induced demyelinating disease

Comparison of cisplatin-induced anti-tumor response in CT26 syngeneic tumors of three BALB/c substrains

Background

To determine whether the background of BALB/c substrains affects the response to anti-tumor drugs, we measured for alterations in tumor growth, histopathological structure of the tumor, and expressions of tumor-related proteins in three BALB/c substrains derived from different sources (BALB/cKorl, BALB/cA and BALB/cB), after exposure to varying concentrations of cisplatin (0.1, 1 and 5 mg/kg).

Results

Cisplatin treatment induced similar responses for body and organ weights, serum analyzing factors, and blood analyzing factors in all BALB/c substrains with CT26 syngeneic tumor. Few differences were detected in the volume and histopathological structure of the CT26 tumor. Growth inhibition of CT26 tumors after exposure to cisplatin was greater in the BALB/cB substrain than BALB/cKorl and BALB/cA substrains, and a similar pattern was observed in the histopathological structure of tumors. However, the expression levels of other tumor-related factors, including Ki67, p27, p53, Bcl-2-associated X protein (Bax), B-cell lymphoma 2 (Bcl-2), caspase-3 (Cas-3), matrix metallopeptidase 2 (MMP2) and vascular endothelial growth factor (VEGF) proteins, were constantly maintained in the tumors of all three substrains after cisplatin treatment. A similar decrease pattern was observed for the expressions of inflammatory cytokines, including interleukin (IL)-1β, IL-6 and IL-10, in the CT26 tumors of the three BALB/c substrains.

Conclusions

Taken together, results of the present study indicate that the genetic background of the three BALB/c substrains has no major effect on the therapeutic responsiveness of cisplatin, except growth and histopathology of the CT26 syngeneic tumor.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42826-021-00110-3.

Resilience in Long-Term Viral Infection: Genetic Determinants and Interactions

Virus-induced neurological sequelae resulting from infection by Theiler's murine encephalomyelitis virus (TMEV) are used for studying human conditions ranging from epileptic seizures to demyelinating disease. Mouse strains are typically considered susceptible or resistant to TMEV infection based on viral persistence and extreme phenotypes, such as demyelination. We have identified a broader spectrum of phenotypic outcomes by infecting strains of the genetically diverse Collaborative Cross (CC) mouse resource. We evaluated the chronic-infection gene expression profiles of hippocampi and thoracic spinal cords for 19 CC strains in relation to phenotypic severity and TMEV persistence. Strains were clustered based on similar phenotypic profiles and TMEV levels at 90 days post-infection, and we categorized distinct TMEV response profiles. The three most common profiles included "resistant" and "susceptible," as before, as well as a "resilient" TMEV response group which experienced both TMEV persistence and mild neurological phenotypes even at 90 days post-infection. Each profile had a distinct gene expression signature, allowing the identification of pathways and networks specific to each TMEV response group. CC founder haplotypes for genes involved in these pathways/networks revealed candidate response-specific alleles. These alleles demonstrated pleiotropy and epigenetic (miRNA) regulation in long-term TMEV infection, with particular relevance for resilient mouse strains.

Substrains matter in phenotyping of C57BL/6 mice

The inbred mouse strain C57BL/6 has been widely used as a background strain for spontaneous and induced mutations. Developed in the 1930s, the C57BL/6 strain diverged into two major groups in the 1950s, namely, C57BL/6J and C57BL/6N, and more than 20 substrains have been established from them worldwide. We previously reported genetic differences among C57BL/6 substrains in 2009 and 2015. Since then, dozens of reports have been published on phenotypic differences in behavioral, neurological, cardiovascular, and metabolic traits. Substrains need to be chosen according to the purpose of the study because phenotypic differences might affect the experimental results. In this paper, we review recent reports of phenotypic and genetic differences among C57BL/6 substrains, focus our attention on the proper use of C57BL/6 and other inbred strains in the era of genome editing, and provide the life science research community wider knowledge about this subject.

Influence of three BALB/c substrain backgrounds on the skin tumor induction efficacy to DMBA and TPA cotreatment

Differences in responsiveness of BALB/c substrains have been investigated in various fields, including diabetes induction, corpus callosum deficiency, virus-induced demyelinating disease, aggressive behavior and osteonecrosis. However, induction efficacy of skin tumor remains untried. We therefore investigated the influence of BALB/c substrain backgrounds on the skin tumor induction efficacy in response to DMBA (7,12-Dimethylbenz[a]anthracene) and TPA (12-O-tetradecanoylphorbol-13-acetate) cotreatment. Alterations in the levels of tumor growth related factors, histopathological structure, and the expression to tumor related proteins were measured in three BALB/c substrains (BALB/cKorl, BALB/cA and BALB/cB) after exposure to DMBA (25 μg/kg) and three different doses of TPA (2, 4 and 8 μg/kg). The average number and induction efficacy of tumors in response to DMBA+TPA treatment were significantly greater in the BALB/cKorl substrain than in BALB/cA and BALB/cB. However, cotreatment with DMBA+TPA induced similar responses for body and organ weights of all three substrains. Few differences were detected in the serum analyzing factors, while similar responsiveness was observed for blood analyzing factors after DMBA+TPA treatment. Furthermore, the three BALB/c substrains exhibited similar patterns in their histopathological structure in DMBA+TPA-induced tumors. The expression levels of apoptotic proteins and tumor related proteins were constantly maintained in all three BALB/c substrains treated with DMBA+TPA. In addition, the responsiveness to cisplatin treatment was overall very similar in the three BALB/c substrains with DMBA+TPA-induced tumors. Taken together, these results indicate that genetic background of the three BALB/c substrains does not have a major effect on the DMBA+TPA-induced skin carcinogenesis and therapeutic responsiveness of cisplatin, except induction efficacy.

The ATP-gated P2X1 ion channel contributes to the severity of antibody-mediated Transfusion-Related Acute Lung Injury in mice

The biological responses that control the development of Transfusion-Related Acute Lung Injury (TRALI), a serious post-transfusion respiratory syndrome, still need to be clarified. Since extracellular nucleotides and their P2 receptors participate in inflammatory processes as well as in cellular responses to stress, we investigated the role of the ATP-gated P2X₁ cation channel in antibody-mediated TRALI. The effects of NF449, a selective P2X1 receptor (P2RX1) antagonist, were analyzed in a mouse two-hit model of TRALI. Mice were primed with lipopolysaccharide (LPS) and 24 h later challenged by administrating an anti-MHC I antibody. The selective P2RX1 antagonist NF449 was administrated before the administration of LPS and/or the anti-MHC I antibody. When given before antibody administration, NF449 improved survival while maximal protection was achieved when NF449 was also administrated before the sensitization step. Under this later condition, protein contents in bronchoalveolar lavages were dramatically reduced. Cell depletion experiments indicated that monocytes/macrophages, but not neutrophils, contribute to this effect. In addition, the reduced lung periarteriolar interstitial edemas in NF449-treated mice suggested that P2RX1 from arteriolar smooth muscle cells could represent a target of NF449. Accordingly, inhibition of TRPC6, another cation channel expressed by smooth muscle cells, also reduced TRALI-associated pulmonary interstitial and alveolar edemas. These data strongly suggest that cation channels like P2RX1 or TRPC6 participate to TRALI pathological responses.

Manipulation of host factors optimizes the pathogenesis of western equine encephalitis virus infections in mice for antiviral drug development

While alphaviruses spread naturally via mosquito vectors, some can also be transmitted as aerosols making them potential bioterrorism agents. One such pathogen, western equine encephalitis virus (WEEV), causes fatal human encephalitis via multiple routes of infection and thus presumably via multiple mechanisms. Although WEEV also produces acute encephalitis in non-human primates, a small animal model that recapitulates features of human disease would be useful for both pathogenesis studies and to evaluate candidate antiviral therapies. We have optimized conditions to infect mice with a low passage isolate of WEEV, thereby allowing detailed investigation of virus tropism, replication, neuroinvasion, and neurovirulence. We find that host factors strongly influence disease outcome, and in particular, that age, gender, and genetic background all have significant effects on disease susceptibility independent of virus tropism or replication within the central nervous system. Our data show that experimental variables can be adjusted in mice to recapitulate disease features known to occur in both non-human primates and humans, thus aiding further study of WEEV pathogenesis and providing a realistic therapeutic window for antiviral drug delivery.

An elite controller of picornavirus infection targets an epitope that is resistant to immune escape

The emergence of novel viral pathogens can lead to devastating consequences in the infected population. However, on occasion, rare hyper-responsive elite controllers are able to mount a protective primary response to infection and clear the new pathogen. Factors distinguishing elite controllers from other members of the population are not completely understood. We have been using Theiler's murine encephalomyelitis as a model of primary infection in mice and clearance of the virus is limited to one MHC genotype capable of generating a protective response to a single viral peptide VP2_121-130. The genetics of host susceptibility to TMEV, a natural mouse pathogen, has been studied extensively and non-protective CD8 responses to other peptides have been documented, however, little is known why the protective response to infection focuses on the VP2_121-130 peptide. To study this question, we have generated TMEV mutants that encode for mutations within the VP2_121-130 peptide. We find that very few of mutants are able to assemble and infect in vitro. These mutations are not related to virus RNA structure since non-coding mutations do not interfere with assembly. In the rare event when functional VP2_121-130 mutant viruses did emerge, they were attenuated to some level or retained the ability to develop an immune response to the wild-type VP2_121-130 sequence, demonstrating that the virus is incapable of escaping the protective response. These findings advance our understanding of how characteristics of the host immune response and an infectious agent can interact to lead to the appearance of rare super controllers in a population. Furthermore, the immutable nature of the viral antigen highlights the importance of choosing appropriate vaccine antigens and has implications for the development of agents that are able to generate protective CD8 T-cell responses.

Multiple linked quantitative trait loci within the Tmevd2/Eae3 interval control the severity of experimental allergic encephalomyelitis in DBA/2J mice

Theiler’s murine encephalomyelitis virus-induced demyelination (TMEVD) and experimental allergic encephalomyelitis (EAE) are the principal animal models of multiple sclerosis (MS). Previously we provided evidence that Tmevd2 and Eae3 may represent either a shared susceptibility locus or members of a gene complex controlling susceptibility to CNS inflammatory demyelinating disease. To explore the genetic relationship between Tmevd2 and Eae3, we generated a D2.C-Tmevd2 interval-specific congenic (ISC) line and three overlapping interval-specific recombinant congenic (ISRC) lines in which the Tmevd2 resistant allele from BALB/cByJ was introgressed onto the TMEVD-susceptible DBA/2J background. These mice, all H2^d, were studied for susceptibility to EAE elicited by immunization with PLP_180–199. Compared to DBA/2J mice, D2.C-Tmevd2 mice developed a significantly less severe clinical disease course and EAE pathology in the spinal cord, confirming the existence of Eae3 and its linkage to Tmevd2 in this strain combination. Compare to DBA/2J and D2.C-Tmevd2, all three ISRC lines exhibited clinical disease courses of intermediate severity. Neither differences in ex vivo antigen-specific cytokine nor proliferative responses uniquely cosegregated with differences in disease severity. These results indicate that multiple QTL within the Tmevd2/Eae3 interval influence EAE severity, one of which includes a homology region for a QTL found in MS by admixture mapping.

Neonatal maternal separation alters immune, endocrine, and behavioral responses to acute Theiler's virus infection in adult mice

Previous studies have established a link between adverse early life events and subsequent disease vulnerability. The present study assessed the long-term effects of neonatal maternal separation on the response to Theiler's murine encephalomyelitis virus infection, a model of multiple sclerosis. Balb/cJ mouse pups were separated from their dam for 180-min/day (180-min MS), 15-min/day (15-min MS), or left undisturbed from postnatal days 2-14. During adolescence, mice were infected with Theiler's virus and sacrificed at days 14, 21, or 35 post-infection. Prolonged 180-min MS increased viral load and delayed viral clearance in the spinal cords of males and females, whereas brief 15-min MS increased the rate of viral clearance in females. The 15-min and 180-min MS mice exhibited blunted corticosterone responses during infection, suggesting that reduced HPA sensitivity may have altered the immune response to infection. These findings demonstrate that early life events alter vulnerability to CNS infection later in life. Therefore, this model could be used to study gene-environment interactions that contribute to individual differences in susceptibility to infectious and autoimmune diseases of the CNS.

Differential Susceptibility of BALB/c and BALB/cBy mice to Graves' hyperthyroidism

BALB/c mice are susceptible to the induction of Graves' hyperthyroidism. To investigate the susceptibility of BALB/c substrains of mice to the induction of hyperthyroidism, we immunized BALB/cJ and BALB/cByJ mice with an adenovirus expressing amino acid residues 1-289 of thyrotropin receptor (TSHR). The data presented in this article showed that 17 of 26 (65%) BALB/c and only 4 of 30 (13%) BALB/cBy mice developed hyperthyroidism. Hyperthyroid mice displayed characteristics of Graves' disease, such as thyroid-stimulating antibodies and enlarged thyroid glands. To explore the differences in the susceptibility of these substrains for hyperthyroidism, we examined the TSHR antibodies in three different assays. The TSHR antibodies determined in a radioreceptor assay (TSH binding inhibitory immunoglobulins) were similar in both of these BALB/c substrains. The TSHR antibody titers of total IgG, IgG1, and IgG2a were measured by an enzyme-linked immunosorbent assay and were found to be similar in these mice. There were no significant differences between these two groups of mice in the thyroid-stimulating antibody activity. However, BALB/cBy mice had significantly higher TSH-blocking antibody activity compared to BALB/c mice. TSHR-specific proliferation of splenocytes and secretion of cytokines interferon-gamma and interleukin-4 by spleen cells were comparable in both the groups. BALB/cJ and BALB/cByJ mice both belong to same MHC haplotype, H-2(d), but differ in the Qa-2 region of class Ib molecule. This report shows the importance of other genes, such as Qa-2 region of class Ib molecule in addition to MHC class II, in the susceptibility of Graves' hyperthyroidism.

Social stress alters the severity and onset of the chronic phase of Theiler's virus infection

Social stress alters the acute phase of Theiler's virus infection (TMEV), a model of multiple sclerosis. Stress applied prior to infection had deleterious disease outcomes, while stress applied concurrent with infection was protective. The current study examined multiple behavioral (motor impairment, open field activity) and immunological measures (IL-6, antibodies to virus and myelin proteins) in both the acute and chronic phases of TMEV. It was found that stress applied prior to infection exacerbated disease outcomes, while concurrent application was protective in both disease phases.

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.

Transition from acute to persistent Theiler's virus infection requires active viral replication that drives proinflammatory cytokine expression and chronic demyelinating disease

The dynamics of Theiler's murine encephalomyelitis virus (TMEV) RNA replication in the central nervous systems of susceptible and resistant strains of mice were examined by quantitative real-time reverse transcription-PCR and were found to correlate with host immune responses. During the acute phase of infection in both susceptible and resistant mice, levels of viral replication were high in the brain and brain stem, while levels of viral genome equivalents were 10- to 100-fold lower in the spinal cord. In the brain, viral RNA replication decreased after a peak at 5 days postinfection (p.i.), in parallel with the appearance of virus-specific antibody responses; however, by 15 days p.i., viral RNA levels began to increase in the spinal cords of susceptible mice. During the transition to and the persistent phase of infection, the numbers of viral genome equivalents in the spinal cord varied substantially for individual mice, but high levels were consistently associated with high levels of proinflammatory Th1 cytokine and chemokine mRNAs. Moreover, a large number of viral genome equivalents and high proinflammatory cytokine mRNA levels in spinal cords were only observed for susceptible SJL/J mice who developed demyelinating disease. These results suggest that TMEV persistence requires active viral replication beginning about day 11 p.i. and that active viral replication with high viral genome loads leads to increased levels of Th1 cytokines that drive disease progression in infected mice.

Infection-dependent phenotypes in MHC-congenic mice are not due to MHC: can we trust congenic animals?

Background

Congenic strains of mice are assumed to differ only at a single gene or region of the genome. These mice have great importance in evaluating the function of genes. However, their utility depends on the maintenance of this true congenic nature. Although, accumulating evidence suggests that congenic strains suffer genetic divergence that could compromise interpretation of experimental results, this problem is usually ignored. During coinfection studies with Salmonella typhimurium and Theiler's murine encephalomyelitis virus (TMEV) in major histocompatibility complex (MHC)-congenic mice, we conducted the proper F₂ controls and discovered significant differences between these F₂ animals and MHC-genotype-matched P₀ and F₁ animals in weight gain and pathogen load. To systematically evaluate the apparent non-MHC differences in these mice, we infected all three generations (P₀, F₁ and F₂) for 5 MHC genotypes (b/b, b/q and q/q as well as d/d, d/q, and q/q) with Salmonella and TMEV.

Results

Infected P₀ MHC q/q congenic homozygotes lost significantly more weight (p = 0.02) and had significantly higher Salmonella (p < 0.01) and TMEV (p = 0.02) titers than the infected F₂ q/q homozygotes. Neither weight nor pathogen load differences were present in sham-infected controls.

Conclusions

These data suggest that these strains differ for genes other than those in the MHC congenic region. The most likely explanation is that deleterious recessive mutations affecting response to infection have accumulated in the more than 40 years that this B10.Q-H-2^q MHC-congenic strain has been separated from its B10-H-2^b parental strain. During typical experiments with congenic strains, the phenotypes of these accumulated mutations will be falsely ascribed to the congenic gene(s). This problem likely affects any strains separated for appreciable time and while usually ignored, can be avoided with the use of F₂ segregants.

Susceptibility to anthrax lethal toxin is controlled by three linked quantitative trait loci

Anthrax lethal toxin (LT) is the principal virulence factor associated with lethal pathologies following infection with Bacillus anthracis. Macrophages are the primary effector cells mediating lethality since macrophage-depleted mice are resistant to LT challenge. Recently, Ltxs1, the gene controlling differential susceptibility of murine macrophages to cytolysis following in vitro exposure to LT, was identified as Kif1c. To directly assess the in vivo role of Kif1c alleles in mortality, we studied a panel of interval-specific recombinant congenic lines carrying various segments of central chromosome 11 derived from LT-resistant DBA/2 mice on the LT-susceptible BALB/c background. The results of this study reveal that mortality is controlled by three linked quantitative trait loci (QTL): Ltxs1/Kif1c (42-43 cM), Ltxs2 (35-37 cM), and Ltxs3 (45-47 cM). The Ltxs3 interval encompasses Nos2, which is an attractive candidate gene for Ltxs3. In this regard, we demonstrate that selective, pharmacologically based inhibition of Nos2 activity in vivo partially overrides genetic resistance to LT and that Nos2 expression as determined by reverse transcription-polymerase chain reaction differs significantly between DBA/2 and BALB/c macrophages. Additionally, to recapitulate dominant resistance to mortality as seen in (BALB/c x DBA/2) F(1) hybrids, DBA/2 alleles are required at all three QTL.

Susceptibility to Theiler's murine encephalomyelitis virus-induced demyelinating disease in BALB/cAnNCr mice is related to absence of a CD4+ T-cell subset

Two histocompatible substrains of BALB/c mice (BALB/cByJ, BALB/cAnNCr) are resistant and susceptible, respectively, to Theiler's murine encephalomyelitis virus-induced demyelinating disease (TMEV-1DD)--a model for viral etiology of human multiple sclerosis. BALB/cByJ mice become susceptible following low-dose irradiation given prior to infection. Resistance is restored by adoptive transfer of CD8+ (but not CD4+) splenic T cells from infected, unirradiated BALB/cByJ donors. In contrast resistance is conferred to BALB/cAnNCr mice by adoptive transfer of either CD4+ or CD8+ T cells from resistant BALB/cByJ donors. T cells from BALB/cAnNCr mice cannot confer protection. To integrate these two observations, we hypothesized that the BALB/cAnNCr mice possess precursors of the regulatory CD8+ T cells, but fail to activate them because they lack a critical CD4+ T-cell subpopulation. We tested this model using serial transfers. The transfer of CD4+ T cells from the BALB/cByJ to the BALB/cAnNCr mice permitted development of BALB/cAnNCr CD8+ T cells that in turn, provided resistance when transferred into susceptible recipients. The BALB/cByJ CD4+ T cells, which activated the CD8+ cells, were sensitive to low-dose irradiation, unlike CD4+ T cells involved in the later inflammatory demyelination. Thus, susceptibility of BALB/cAnNCr mice is due to a defective/absent CD4+ T-cell subset acting immediately after infection.

Virus-induced autoimmunity: epitope spreading to myelin autoepitopes in Theiler's virus infection of the central nervous system

Epidemiological studies indicate that host immunogenetics and history of infection, particularly by viruses, may be a necessary cofactor for the induction of a variety of autoimmune diseases. To date, however, there is no clear-cut evidence, either in experimental animal models or in human autoimmune disease, that supports either molecular mimicry (Wucherpfennig and Strominger, 1995; Fujinami and Oldstone, 1985) or a role for superantigens (Scherer et al., 1993) in the initiation of T cell-mediated autoimmunity. In contrast, the current data provide compelling evidence in support of a major role for epitope spreading in the induction of myelin-specific autoimmunity in mice persistently infected with TMEV. It is significant that two picornaviruses closely related to TMEV, coxsackievirus (Rose and Hill, 1996) and encephalomyocarditis virus (EMCV) (Kyu et al., 1992), have been similarly shown to persist (either the viral RNA or the infectious virus) in their target organs and have been associated with the development of chronic autoimmune diseases, including myocarditis and diabetes. Thus, inflammatory responses induced by viruses that trigger proinflammatory Th1 responses, and have the ability to persist in genetically susceptible hosts, may lead to chronic organ-specific autoimmune disease via epitope spreading. Epitope spreading has important implications for the design of antigen-specific therapies for the potential treatment of MS and other autoimmune diseases. This process indicates that autoimmune diseases are evolving entities and that the specificity of the effector autoantigen-specific T cells varies during the chronic disease process. Our experiments employing tolerance in R-EAE clearly indicate that antigen-specific treatment of ongoing disease is possible for preventing disease relapses, provided the proper relapse-associated epitope is targeted (Vanderlugt et al., 1999). However, the ability to identify relapse-associated epitopes in humans will be a difficult task because immunodominance will vary in every individual. The use of costimulatory antagonists that can induce anergy without requiring prior knowledge of the exact epitopes (Miller et al., 1995b), or the use of therapies that induce bystander suppression (Nicholson et al., 1997; Brocke et al., 1996), may thus be more practical current alternative therapies for the treatment of human autoimmune disease.

Striatal antibodies in children with Tourette's syndrome: multivariate discriminant analysis of IgG repertoires

Antineuronal antibodies have been postulated to be the underlying pathophysiology in TS and other neuropsychiatric disorders. Serum antibodies from 20 children with TS, and 21 control subjects against human striatum, globus pallidus, muscle, and HTB-10 cells were assayed by Western blot techniques. A MANOVA differentiated between TS and control blots, and a discriminant analysis demonstrated which variables contributed most to differences between groups. Prominent differences between TS and control blots were identified using striatal epitopes in contrast to similar patterns shown between groups for globus pallidus, muscle and HTB-10 tissue, supporting striatal autoimmune involvement in TS pathophysiology.

CD8(+) T cells from Theiler's virus-resistant BALB/cByJ mice downregulate pathogenic virus-specific CD4(+) T cells

Theiler's murine encephalomyelitis virus (TMEV) is a picornavirus which induces an immune-mediated demyelinating disease in susceptible strains of mice and serves as a relevant animal model for multiple sclerosis. Treatment with low dose irradiation prior to infection with the BeAn strain of TMEV renders the genetically resistant BALB/cByJ (C/cByJ) mice susceptible to disease. Previous studies have shown that disease resistance in the C/cByJ is mediated by a 'regulatory' CD8(+) T cell population, which does not appear to function via a cytolytic mechanism. We show here that TMEV-specific CD4(+) T cell blasts transferred into susceptible, irradiated C/cByJ accelerate clinical disease and enhance TMEV-specific DTH and proliferation in these animals. Significantly, CD8(+) cells from infected, resistant C/cByJ mice specifically downregulate the in vivo disease potentiation and diminish virus specific DTH, and proliferative and pro-inflammatory cytokine responses (IFNgamma and IL-2) in recipients of TMEV-specific CD4(+) T cell blasts. These results indicate that TMEV infection of resistant C/cByJ mice induces a radiosensitive population of regulatory CD8(+) T cells which actively downregulate inherent Th1 responses which have disease initiating potential.

Pathologic role and temporal appearance of newly emerging autoepitopes in relapsing experimental autoimmune encephalomyelitis

Relapsing experimental autoimmune encephalomyelitis (R-EAE) is a CD4+ T cell-mediated demyelinating disease model for multiple sclerosis. Myelin destruction during the initial relapsing phase of R-EAE in SJL mice initiated by immunization with the proteolipid protein (PLP) epitope PLP139-151 is associated with activation of T cells specific for the endogenous, non-cross-reactive PLP178-191 epitope (intramolecular epitope spreading), while relapses in R-EAE induced with the myelin basic protein (MBP) epitope MBP84-104 are associated with PLP139-151-specific responses (intermolecular epitope spreading). Here, we demonstrate that T cells specific for endogenous myelin epitopes play the major pathologic role in mediating clinical relapses. T cells specific for relapse-associated epitopes can serially transfer disease to naive recipients and are demonstrable in the CNS of mice with chronic R-EAE. More importantly, induction of myelin-specific tolerance to relapse-associated epitopes, by i.v. injection of ethylene carbodiimide-fixed peptide-pulsed APCs, either before disease initiation or during remission from acute disease effectively blocks the expression of the initial disease relapse. Further, blockade of B7-1-mediated costimulation with anti-B7-1 F(ab) during disease remission from acute PLP139-151-induced disease prevents clinical relapses by inhibiting activation of PLP178-191-specific T cells. The protective effects of anti-B7-1 F(ab) treatment are long-lasting and highly effective even when administered following the initial relapsing episode wherein spreading to a MBP epitope (MBP84-104) is inhibited. Collectively, these data indicate that epitope spreading is B7-1 dependent, plays a major pathologic role in disease progression, and follows a hierarchical order associated with the relative encephalitogenic dominance of the myelin epitopes (PLP139-151 > PLP178-191 > MBP84-104).

The role of protective CD8+ T cells in resistance of BALB/c mice to Theiler's murine encephalomyelitis virus-induced demyelinating disease: regulatory vs. lytic

Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease (TMEV-IDD) is an excellent model for human multiple sclerosis. Within the BALB/c strain, BALB/cAnNCr mice are susceptible while BALB/cByJ mice are resistant. BALB/cByJ mice become susceptible when irradiated. Adoptive transfer of CD8+ splenic T cells from resistant BALB/cByJ donors protect irradiated BALB/cByJ, as well as BALB/cAnNCr recipients, from development of TMEV-IDD. Anti-TMEV CTL activities in BALB/cAnNCr, BALB/cByJ and irradiated BALB/cByJ mice are comparable. A population of splenic CD4+ T cells in BALB/cByJ donors has also been identified which can protect both susceptible BALB/cAnNCr and irradiated BALB/cByJ recipients from TMEV-IDD via adoptive transfer.

Natural pathogens of laboratory mice, rats, and rabbits and their effects on research

Laboratory mice, rats, and rabbits may harbor a variety of viral, bacterial, parasitic, and fungal agents. Frequently, these organisms cause no overt signs of disease. However, many of the natural pathogens of these laboratory animals may alter host physiology, rendering the host unsuitable for many experimental uses. While the number and prevalence of these pathogens have declined considerably, many still turn up in laboratory animals and represent unwanted variables in research. Investigators using mice, rats, and rabbits in biomedical experimentation should be aware of the profound effects that many of these agents can have on research.

Central nervous system cytokine mRNA expression following Theiler's murine encephalomyelitis virus infection

DA strain of Theiler's murine encephalomyelitis virus (TMEV) produces a biphasic disease with an initial self-limited acute gray matter polioencephalomyelitis in all strains of mice followed by, in the case of certain susceptible strains of mice, a chronic inflammatory demyelination of the spinal cord with a persistent virus infection. A pathogenic role for T-helper 1 (Th1) cells during the demyelinating phase of disease has been proposed. We characterized the cytokine mRNA expression in the brain and spinal cord of susceptible and resistant strains of mice during the early encephalomyelitic disease and the late demyelination, using a semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) assay. At the time of the encephalomyelitis, both resistant and susceptible mice expressed proinflammatory cytokine mRNAs followed by T-cell derived mRNAs; susceptible mice expressed more IL-12 p40 mRNA than resistant mice. During this early disease, there was no significant difference in Th1 cytokine mRNA expression in the brain and spinal cord among the four strains and relatively little Th2 type cytokine upregulation above levels seen in mock-infected controls. During the late demyelinating disease, susceptible but not resistant mice had evidence of viral genome and a continuous expression of Th1 type cytokine mRNAs. The expression of Th2 cytokine mRNAs varied among the different strains and did not correlate with susceptibility or resistance. The results indicate the complexity of cytokine mRNA expression following TMEV infection and the dependence of the expression on disease pathology, the time following infection and the genetics of the host.

Two models of multiple sclerosis: experimental allergic encephalomyelitis (EAE) and Theiler's murine encephalomyelitis virus (TMEV) infection. A pathological and immunological comparison

Theiler's murine encephalomyelitis virus (TMEV) infection and experimental allergic encephalomyelitis (EAE) are considered among the best models of human multiple sclerosis (MS). In both models, clinical disease is characterized by paralysis, while pathological changes consist of inflammatory demyelination. In both models there is a genetic influence on susceptibility/resistance to the development of disease. This has been thoroughly studied in TMEV infection, and it has been found to depend on both major histocompatibility complex (MHC) and non-MHC genes. At least four genes have been so far identified. Because of this genetic influence, some strains of mice are more susceptible to both clinical and pathological changes than others, and susceptibility appears to best correlate with the ability of a certain murine strain to develop a delayed-type hypersensitivity (DTH) response to viral antigens. We have also observed that even among mice which are equally susceptible clinically, striking differences may be seen under pathological examination. These consist of different gradients of severity of inflammation, particularly in regards to the macrophage component. There is an inverse relationship between the number of macrophages, and their length of stay in the CNS, and the ability of mice to remyelinate their lesions. The most severe lesions are in SJL/J mice, and remyelination in this strain is extremely poor. The least severe lesions in terms of macrophage invasion are in strains such as NZW and RIIIS/J, and these are able to remyelinate lesions very successfully. Murine chronic relapsing EAE (CR-EAE) shows pathological changes in many ways similar to those in TMEV-infected SJL/J mice, although less severe in terms of degrees of macrophage infiltration and tissue destruction. Mice with CR-EAE have a correspondingly limited ability to remyelinate their lesions. In both models the pathology appears to be mediated through a DTH response. However, while in EAE the DTH response is clearly against neuroantigens, the response in TMEV infection is against the virus itself. The end result in both models would be that of myelin destruction through a lymphotoxin-cytokine-mediated mechanism. The importance of the DTH response in both models is well illustrated by the effects of tolerance induction in EAE and TMEV infection to neuroantigens and virus, respectively. These are important models of human MS, since the current hypothesis is that a viral infection early in life, on the appropriate genetic background, may trigger a secondary misdirected immune response which could be directed either against myelin antigens and/or possible persistent virus(es).

Release of myelin basic protein-degrading proteolytic activity from microglia and macrophages after infection with Theiler's murine encephalomyelitis virus: comparison between susceptible and resistant mice

Theiler's murine encephalomyelitis virus (TMEV) produces a chronic inflammatory demyelinating disease in its natural host, the mouse. A delayed-type hypersensitivity (DTH) response to viral antigens generally correlates with susceptibility to the disease and is thought to play an important role in the pathogenesis of demyelination in this model of human multiple sclerosis (MS). The hallmark of DTH responses is the recruitment by activated Th-1 cells of lymphoid cells and especially macrophages in infected areas. It is believed that soluble factors released by these cells would produce tissue damage, particularly myelin breakdown. In the present study, we compared TMEV-infected macrophages and microglia, isolated from both susceptible SJL/J and resistant C57BL/6 mice, for their ability to secrete proteolytic enzymes capable of degrading myelin basic protein. In addition, we studied whether supernatants from infected microglia/macrophages were also capable of killing oligodendrocytes in the same in vitro system. As detected by SDS-PAGE, MBP-degrading proteolytic activity was found only in supernatants from infected SJL/J microglia and macrophages, but not in supernatants collected from infected C57BL/6 microglia and macrophages, or in supernatants from mock-infected SJL/J and C57BL/6 cells. Similarly, incubation of E20.1 cells, an immortalized line of oligodendrocytes, with infected SJL/J, but not C57BL/6 supernatants, resulted in cytotoxic activity. When cells from resistant C57BL/6 mice were treated with LPS, they became susceptible to infection and also secreted proteolytic enzymes. The proteolytic activity released from infected microglia and macrophages was found to be dose-dependent, was inactivated by heat, and was inhibited by phenylmethylsulphonyl fluoride (PMSF). These results indicate that a serine protease is released from infected microglia and macrophages and suggest a role for proteases in TMEV-induced myelin injury.

Immunology of Theiler's murine encephalomyelitis virus infection

Theiler's murine encephalomyelitis virus (TMEV) is a single-stranded RNA virus that belongs to the family of picornaviruses. Intracranial inoculation of susceptible mouse strains with TMEV results in biphasic disease, consisting of early acute disease that resembles poliomyelitis, followed by late chronic demyelinating disease that is characterized by the appearance of chronic inflammatory demyelinating lesions. Susceptibility to TMEV infection is genetically controlled by three loci: one that maps to the H-2D region of the major histocompatibility complex, one to the beta-chain constant region of the T-cell antigen receptor, and one located on chromosome 3. Both early acute and chronic late demyelinating diseases are immunologically mediated. T cells appear to play an important role in the pathogenesis of the disease. TMEV-induced demyelinating disease in mice has extensive similarities with multiple sclerosis, and it is considered one of the best experimental animal models for multiple sclerosis.