Strain-dependent recovery of spontaneous hindlimb movement in spinal cord transected mice (CD1, C57BL/6, BALB/c).

Reorganization and plasticity after spinal cord injury have been recently shown to take place in sublesional neuronal networks, but the possibility of strain-dependent changes at that level has never been explored. The authors studied the spontaneous return of hindlimb movement in low-thoracic spinal cord transected (Tx) mice from 3 commonly used strains. Without intervention, most CD1, C57BL/6, and BALB/c mice displayed some hindlimb movement recovery after Tx. Although all assessment methods unanimously reported that CD1 displayed higher recovery levels than did the C57BL/6 and BALB/c, higher scores were generally found with the Antri-Orsal-Barthe (M. Antri, D. Orsal, & J. Y. Barthe, 2002) and the Average Combined Score (P. A. Guertin, 2005a) methods. Such spontaneous recovery in low-thoracic Tx mice is likely the result of neuronal plasticity at the lumbosacral spinal cord level, suggesting that these sublesional changes are strain dependent. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An important role for major histocompatibility complex class I-restricted T cells, and a limited role for gamma interferon, in protection of mice against lethal herpes simplex virus infection

Herpes simplex virus (HSV) inhibits major histocompatibility complex (MHC) class I expression in infected cells and does so much more efficiently in human cells than in murine cells. Given this difference, if MHC class I-restricted T cells do not play an important role in protection of mice from HSV, an important role for these cells in humans would be unlikely. However, the contribution of MHC class I-restricted T cells to the control of HSV infection in mice remains unclear. Further, the mechanisms by which these cells may act to control infection, particularly in the nervous system, are not well understood, though a role for gamma interferon (IFN-gamma) has been proposed. To address the roles of MHC class I and of IFN-gamma, C57BL/6 mice deficient in MHC class I expression (beta2 microglobulin knockout [beta2KO] mice), in IFN-gamma expression (IFN-gammaKO mice), or in both (IFN-gammaKO/beta2KO mice) were infected with HSV by footpad inoculation. beta2KO mice were markedly compromised in their ability to control infection, as indicated by increased lethality and higher concentrations of virus in the feet and spinal ganglia. In contrast, IFN-gamma appeared to play at most a limited role in viral clearance. The results suggest that MHC class I-restricted T cells play an important role in protection of mice against neuroinvasive HSV infection and do so largely by mechanisms other than the production of IFN-gamma.     

Factors influencing the effects of murine cytomegalovirus on the pancreas

BACKGROUND: As human cytomegalovirus (HCMV) infections are implicated in insulin-dependent diabetes mellitus (IDDM), the effects of murine (M)CMV infection of inbred mice on the pancreas are of interest. RESULTS: Inflammation and periacinar oedema peaked on day 3 and were replaced by a focal inflammation, but infected cells were rare. The islets were spared in C57BL mice. Insulitis normally seen in non-obese diabetic (NOD) mice was accelerated, but infected NOD mice did not become glycosuric. Isotypes of total and autoreactive antibodies suggested a shift to a Th 1 response (IgG2a) in all MCMV-infected mice. MCMV-induced pancreatitis was not affected by MHC genes but was similar or less severe in BALB/c mice. As these lack the Cmv1 gene, which provides a protective natural killer (NK) cell response in C57BL congenic mice, the C57BL background may carry a pancreatitis susceptibility gene able to counter NK-mediated restriction of viral replication. Consistently, congenic mice expressing Cmvl on a BALB/c background did not display pancreatitis, unless depleted of NK cells. In vivo treatment with soluble cytokine receptors suggested that interleukin 1 (IL-1) and/or tumour necrosis factor alpha contribute to acinar necrosis in C57BL mice.     

Induction of bilateral retinal necrosis in mice by unilateral intracameral inoculation of a glycoprotein-C deficient clinical isolate of herpes simplex virus type 1

Herpes simplex virus can cause acute retinal necrosis, a blinding retinal disease in man. A unilateral intracameral inoculation of herpes simplex virus type 1 (HSV-1) in mice induces retinal necrosis primarily in the contralateral eye and provides an experimental model for the disease. Previous studies suggested that a major envelope glycoprotein of HSV-1, glycoprotein C (gC), is required for retinal necrosis. We studied HSV-1 strain TN-1, a gC-deficient clinical isolated from a lesion of herpetic keratitis, for its pathogenicity in mice with an intracameral inoculation of the virus and found that TN-1 could induce severe necrotizing retinitis in both inoculated and uninoculated eyes of BALB/c mice. Inoculation with a lower dose of TN-1 resulted in a unilateral necrotizing retinitis in the uninoculated eyes. Tissue virus titration of infected mice killed at various times after inoculation detected an infectious virus in various organs including the eyeballs, trigeminal ganglia, brain and adrenal glands. Anterior chamber-associated immune deviation (ACAID) was observed in TN-1-inoculated mice as well as in mice inoculated with gC-positive laboratory strain KOS 7 days postinoculation. Our findings suggested that gC of HSV-1 is not necessary for either the induction of retinal necrosis, neural spread of the virus, or ACAID.     

Interferon-gamma antagonizes transforming growth factor-beta2-mediated immunosuppression in murine Toxoplasma encephalitis

The in vivo modulating activity of recombinant transforming growth factor (TGF)-beta2 on acute toxoplasmosis was evaluated in both Toxoplasma gondii susceptible C57BL/6 and resistant BALB/c mice. TGF-beta2 lethally exacerbated Toxoplasma encephalitis in C57BL/6, but not in BALB/c mice. In C57BL/6 mice, TGF-beta2 induced a profound dose-dependent increase of the intracerebral parasitic load as well as a reduction of IFN-gamma levels in serum and cerebrospinal fluid with a coincident decrease of MHC class II antigen expression of macrophages, microglial cells, and B cells. Furthermore, TGF-beta2-treated C57BL/6 mice showed a reduced activation of CD4+ and CD8+ T cells and a diminished recruitment of immune cells to the brain. The TGF-beta2-mediated development of lethal toxoplasmosis in C57BL/6 mice was abolished by treatment with recombinant interferon (IFN)-gamma.     

Coronavirus-induced demyelination occurs in the presence of virus-specific cytotoxic T cells

C57BI/6, but not BALB/c, mice infected with mouse hepatitis virus strain JHM (MHV-JHM) develop a late onset, symptomatic demyelinating encephalomyelitis. In this report, we characterized anti-viral cytotoxic T cells in the central nervous system and spleen during the acute and chronic stages of the MHV infection. The data show that C57BI/6 mice display a cytotoxic T cell (CTL) response to the surface (S) glycoprotein and this response can be demonstrated in lymphocytes isolated from the brains and spinal cords of mice both acutely and persistently infected with MHV-JHM. Thus, the anti-S CTL activity present in the central nervous system of chronically infected animals is not sufficient to prevent the demyelinating process. BALB/c mice have been shown previously to mount a CTL response against the nucleocapsid (N) protein (Stohlman et al., 1992). Since C57BI/6 mice do not mount a response to the N protein, the role of the N-specific response in preventing the late onset disease was assessed using B10.A(18R) mice, recombinant in the H-2 locus. These mice contain the d alleles of the D and L loci and exhibit a CTL response against the N protein. However, unlike the BALB/c mice, these animals develop the late onset symptomatic disease. These results suggest that the N-specific response is partially protective against the development of the demyelinating disease, but that additional factors are also likely to be involved.     

Epizootic congenital arthrogryposis-hydranencephaly syndrome in cattle: isolation of Akabane virus from affected fetuses

Previous serolgoical studies strongly suggested Akabane virus to be the etiologic agent of epizootic abortion and congenital arthrogryposis-hydranencephaly in cattle, and this view was further corroborated in this study by the isolation of the virus from an aborted fetus in an epizootic of the disease and from a fetus extracted froma cow which was suggested by serologic tests to have a recent infection with the virus. The latter fetus had histological changes of encephalomyelitis and polymyositis, and specific antigens of Akabane virus was shown by the immunofluorescent technique in brain tissues as well as skeletal muscular tissues. The virus was recovered from various fetal tissues and fluids, and in relatively large amounts from brain, spinal cord, cerebral fluid, skeletal muscles and fetal placenta. The intracranial inoculation of suckling mice, 1-2 days of age, was the most sensitive system for Akabane virus isolation and HmLu-1, a continuous cell line from hamster lung, seemed almost as sensitive as suckling mice.     

Ambiguous role of interleukin-12 in Yersinia enterocolitica infection in susceptible and resistant mouse strains

Endogenous interleukin-12 (IL-12) mediates protection against Yersinia enterocolitica in C57BL/6 mice by triggering gamma interferon (IFN-gamma) production in NK and CD4+ T cells. Administration of exogenous IL-12 confers protection against yersiniae in Yersinia-susceptible BALB/c mice but exacerbates yersiniosis in resistant C57BL/6 mice. Therefore, we wanted to dissect the different mechanisms exerted by IL-12 during Yersinia infections by using different models of Yersinia-resistant and -susceptible mice, including resistant C57BL/6 mice, susceptible BALB/c mice, intermediate-susceptible wild-type 129/Sv mice, 129/Sv IFN-gamma-receptor-deficient (IFN-gamma R-/-) mice and C57BL/6 tumor necrosis factor (TNF) receptor p55 chain-deficient (TNFR p55-/-) mice. IFN-gamma R-/- mice turned out to be highly susceptible to infection by Y. enterocolitica compared with IFN-gamma R+/+ mice. Administration of IL-12 was protective in IFN-gamma R+/+ mice but not in IFN-gamma R-/- mice, suggesting that IFN-gamma R-induced mechanisms are essential for IL-12-induced resistance against yersiniae. BALB/c mice could be rendered Yersinia resistant by administration of anti-CD4 antibodies or by administration of IL-12. In contrast, C57BL/6 mice could be rendered more resistant by administration of transforming growth factor beta (TGF-beta). Furthermore, IL-12-triggered toxic effects in C57BL/6 mice were abrogated by coadministration of TGF-beta. While administration of IL-12 alone increased TNF-alpha levels, administration of TGF-beta or TGF-beta plus IL-12 decreased both TNF-alpha and IFN-gamma levels in Yersinia-infected C57BL/6 mice. Moreover, IL-12 did not induce toxicity in Yersinia-infected TNFR p55-/- mice, suggesting that TNF-alpha accounts for IL-12-induced toxicity. Taken together, IL-12 may induce different effector mechanisms in BALB/c and C57BL/6 mice resulting either in protection or exacerbation. These results are important for understanding the critical balance of proinflammatory and regulatory cytokines in bacterial infections which is decisive for beneficial effects of cytokine therapy.     

Immunization with a single major histocompatibility complex class I-restricted cytotoxic T-lymphocyte recognition epitope of herpes simplex virus type 2 confers protective immunity

We have evaluated the potential of conferring protective immunity to herpes simplex virus type 2 (HSV-2) by selectively inducing an HSV-specific CD8(+) cytotoxic T-lymphocyte (CTL) response directed against a single major histocompatibility complex class I-restricted CTL recognition epitope. We generated a recombinant vaccinia virus (rVV-ES-gB498-505) which expresses the H-2Kb-restricted, HSV-1/2-cross-reactive CTL recognition epitope, HSV glycoprotein B residues 498 to 505 (SSIEFARL) (gB498-505), fused to the adenovirus type 5 E3/19K endoplasmic reticulum insertion sequence (ES). Mucosal immunization of C57BL/6 mice with this recombinant vaccinia virus induced both a primary CTL response in the draining lymph nodes and a splenic memory CTL response directed against HSV gB498-505. To determine the ability of the gB498-505-specific memory CTL response to provide protection from HSV infection, immunized mice were challenged with a lethal dose of HSV-2 strain 186 by the intranasal (i.n.) route. Development of the gB498-505-specific CTL response conferred resistance in 60 to 75% of mice challenged with a lethal dose of HSV-2 and significantly reduced the levels of infectious virus in the brains and trigeminal ganglia of challenged mice. Finally, i.n. immunization of C57BL/6 mice with either a recombinant influenza virus or a recombinant vaccinia virus expressing HSV gB498-505 without the ES was also demonstrated to induce an HSV-specific CTL response and provide protection from HSV infection. This finding confirms that the induction of an HSV-specific CTL response directed against a single epitope is sufficient for conferring protective immunity to HSV. Our findings support the role of CD8(+) T cells in the control of HSV infection of the central nervous system and suggest the potential importance of eliciting HSV-specific mucosal CD8(+) CTL in HSV vaccine design.     

Glucose-modified low density lipoprotein enhances human monocyte chemotaxis

In response to stimulation with immobilized anti-CD3 antibody, splenocytes from C57BL/6 and BALB/c mice principally produced INF-gamma and IL-4, respectively. However, both splenocytes equally proliferated in response to ConA. We compared the changes after inoculation with BCG (1 mg/mouse) in their capacity to produce IL-4 or IFN-gamma in response to anti-CD3 antibody and to proliferate in response to ConA. Splenocytes from C57BL/6 and BALB/c mice, that had been inoculated with BCG 4 weeks before, produced IFN-gamma with diminished IL-4 production in response to anti-CD3 antibody. Furthermore these splenocytes became anergic to ConA stimulation and died due to cell apoptosis in stead of proliferation. However, we observed the strain difference at 12 weeks after BCG-infection. BCG-primed C57BL/6 splenocytes, that continuously produced IFN-gamma in response to anti-CD3 antibody, failed to proliferate in response to ConA. In contrast, BCG-primed BALB/c splenocytes, that increased IL-4 production but decreased IFN-gamma production when stimulated with anti-CD3 antibody, could proliferate well in response to ConA. Since the splenocytes of BALB/c mice became ConA responsive along with their shifting from Th1 dominant immune response at 4 weeks to Th2 dominant immune response at 12 weeks after BCG-inoculation, IL-4 was assumed to play a crucial role in activation of anergic T cells. Therefore, we stimulated splenocytes from both strains of mice infected with BCG 4 weeks before with ConA in the presence or absence of IL-4. Splenocytes from BCG-infected BALB/c mice showed marked proliferation, while those from BCG-infected C57BL/6 mice failed. We found that IL-4 protected against ConA-induced cell apoptosis in BALB/c splenocytes but not C57BL/6 splenocytes.     

An early, abundant cytotoxic T-lymphocyte response against Theiler's virus is critical for preventing viral persistence

In genetically susceptible strains of mice, the DA strain of Theiler's virus, a picornavirus, causes a persistent infection of the white matter of the spinal cord associated with chronic demyelination. In resistant strains, on the other hand, the infection is cleared within 1 to 2 weeks. In this article, we show that Theiler's virus induces a rapid and abundant cytotoxic T lymphocyte (CTL) response in resistant C57BL/6 mice, while the response remains low throughout infection in susceptible SJL/J mice. This difference can be referred to a higher number of virus-specific CTL precursors in C57BL/6 mice. These observations indicate that the efficient induction of virus-specific CTL precursors is critical for avoiding the establishment of a persistent picornaviral infection.     

Differences in the liability to self-administer intravenous cocaine between C57BL/6 x SJL and BALB/cByJ mice

Application of animal models of psychostimulant abuse for experimentation in mice is becoming increasingly important for studying the contribution of genetic differences, as well as the roles of selected (targeted) genes, in specific behaviors. The purpose of this study was to investigate strain differences in cocaine self-administration behavior between C57BL/6 x SJL hybrid mice and BALB/cByJ mice. These two strains were chosen because BALB/cByJ mice have a well-developed behavioral pharmacological profile, and hybrid strains on a C57BL/6 background are commonly used for generating transgenic expressing and knockout mutant mice. C57BL/6 x SJL mice dose-dependently acquired cocaine self-administration (1.0 mg/kg/injection but not 0.25 mg/kg/injection) by responding selectively in the active nose-poke hole and maintaining stable levels of daily drug intake; they also exhibited a characteristic inverted-U-shaped cocaine dose-effect function. BALB/cByJ mice failed to acquire cocaine self-administration at either dose under the same test conditions. The strain differences observed in self-administration did not seem to be attributed to other behavioral differences because the two strains exhibited similar amounts of spontaneous nose-poking in the absence of reinforcers, and BALB/cByJ mice responded more than C57BL/6 x SJL mice in a food-reinforced nose-poke operant task. Importantly, the dose-effect function for the motor stimulating effects of cocaine (3.8-30 mg/kg intraperitoneally) suggests enhanced sensitivity but reduced efficacy of cocaine in stimulating motor activity in BALB/cByJ mice relative to the C57BL/6 x SJL hybrid mice. These results indicate that the decreased liability of BALB/cByJ mice to acquire cocaine self-administration is not the result of differences in spontaneous activity or performance, but may reflect different sensitivities to the reinforcing, or rate-disrupting, properties of cocaine. The data support an influence of genetic background in the liability to self-administer cocaine. Thus, a hypothesis is proposed that the decreased liability of BALB/cByJ mice to acquire cocaine self-administration is related to differences in brain monoamine systems linked to the high "emotionality" profile of BALB/c mice in novel or fearful situations, including perhaps cocaine administration.     

Radiological evaluation of complications of intestinal tuberculosis

We have recently observed that the selective adenosine A3 receptor agonist N6-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (IB-MECA) augments interleukin-10 and inhibits tumor necrosis factor-alpha production in endotoxemic mice. In the present study, we extended our investigations into the effect of this compound on the bacterial lipopolysaccharide (endotoxin)-induced inflammatory response in the BALB/c, as well as in the C57BL/6 interleukin-10+/+ and the interleukin-10 deficient C57BL/6 interleukin-10(0)/0 mice strains. In the BALB/c mice, i.p. pre-treatment with IB-MECA (0.2 and 0.5 mg/kg) decreased lipopolysaccharide (60 mg/kg i.p.)-induced plasma levels of interleukin-12 (p40 and p70), interferon-gamma, and nitrite/nitrate (breakdown products of nitric oxide (NO)). On the other hand, pre-treatment with this compound failed to influence lipopolysaccharide-induced plasma interleukin-1 alpha, interleukin-6, and corticosterone concentrations. Similar to its effect in BALB/c mice, IB-MECA enhanced the release of interleukin-10 in the C57BL/6 interleukin-10+/+ mice. Furthermore, IB-MECA inhibited the production of interleukin-12, interferon-gamma, and NO in both the C57BL/6 interleukin-10+/+ and C57BL/6 interleukin-10(0)/0 mice, suggesting that the inhibition of pro-inflammatory cytokine production by this compound is independent of the increased release of interleukin-10. Finally, pre-treatment with this compound protected mice against lipopolysaccharide (60 mg/kg i.p.)-induced lethality. These results indicate that stimulation of adenosine A3 receptors has potent anti-inflammatory effects and may represent a potential strategy in the treatment of septic shock and other inflammatory diseases.     

The in vitro expression patterns of individual type I interferon genes in Newcastle disease virus infected murine splenocytes and fibroblasts

Murine type I interferon levels present in mice sera following Newcastle disease virus infections are influenced by the If-1 locus. Sera interferon levels in C57BL/6 mice (If-1h allele) are 10- to 15-fold higher than in BALB/c mice (If-1(1) allele). The B6.C-H-28c strain, which carries BALB/c If-1(1) allele on C57BL/6 genomic background, has low interferon levels in sera. This study examined the expression of interferon alpha 1, alpha 4, alpha 5, alpha 6, alpha 9 and beta mRNAs at 7 hr after Newcastle disease virus infection of primary cells (splenocytes and mouse embryo fibroblasts) from C57BL/6, B6.C-H-28c and BALB/c mouse genotypes. Total RNA from these cells was reverse transcribed and all known type I interferon subtypes were amplified. The products were identified by differential hybridization to a panel of subtype specific oligonucleotides. The results show that the pattern of interferon subtypes examined in splenocytes did not differ between If-1h and If-1(1) allele carrying C57BL mice. However, when the genotype was different (BALB/c splenocytes) the pattern of type I interferon mRNAs seen was altered. This genotype-dependent expression was also seen in newcastle disease virus infected fibroblasts. Within a given mouse strain, there were also differences in the subtype response patterns detected in fibroblasts compared with those seen in splenocytes. In conclusion, the present study indicates that mouse genotype appears to be a major determinant of the subtype response pattern seen and tissue specific pattern differences are present within a given mouse genotype.     

Role of macrophages in acute murine cytomegalovirus infection

It has been recognized that macrophages play an important role in controlling virus infection in experimental animal models. To evaluate the role of macrophages in acute murine cytomegalovirus infection, macrophages in the spleen and the liver were eliminated by an intravenous injection of liposomes containing a cytolytic agent, dichloromethylene diphosphonate. The depletion of macrophages led to a significant increase of virus titer in the spleen and lungs in both susceptible BALB/c and resistant C57BL/6 mice during the first three days after intravenous infection. In the spleen, the increase of virus titer in macrophage-depleted BALB/c mice was much greater than that in NK cell-depleted mice. These results suggest that macrophages contribute to protection mainly by the mechanisms which are independent of NK cells during the first three days after infection. The increase of virus titer in macrophage-depleted C57BL/6 mice was as great as that in NK cell-depleted mice because of the high contribution of NK cells to protection in C57BL/6 mice. In the liver in both strains of mice, the effects of macrophage depletion on virus titer were not as much as those in the spleen and lungs. Furthermore, the local depletion of peritoneal macrophages resulted in a great increase of virus titer in the spleen at three days after intraperitoneal infection. We conclude that macrophages greatly contribute to decreasing the virus load in some organs possibly through either or both intrinsic and extrinsic mechanisms in the early phase of primary infection with murine cytomegalovirus.     

Deletions and duplication in internal inverted repeat sequence of long region/unique sequence of long region (IRL/UL) of herpes simplex virus type-1 (HSV-1) genome are not evidently associated with intracranial and foot-pad pathogenicity in mouse model

The biological properties of three deletion variants (1704, 1705 and 1706) of herpes simplex virus type-1 (HSV-1) strain 17 syn+, were studied by establishing a base line pathogenicity of nine individual plaques from the parental 17 syn+ elite stock. Restriction enzyme analysis of deoxyribonucleic acid (DNA) from each of the nine plaque stocks and intracranial inoculation into three weeks old BALB/c mice showed no difference in the size of fragments and distribution of the sites or their 50% lethal dose (LD50) values [plaque forming units (pfu)/mouse] as compared to the parental 17 syn+ stock. Inoculation of the variants into three weeks old BALB/c mice showed that 1705 was not different in pathogenicity from the wild type following intracranial and footpad inoculations. On the other hand variants 1704 and 1706, when compared to the wild type virus were less virulent on intracranial inoculation i.e. the difference in LD50 values was approximately one log and two logs respectively and both the variants failed to kill any of the animals following footpad inoculation even at the dose of 1 x 10(7) pfu/mouse. During in vivo replication experiment in the peripheral nervous system of mice, 1704 and 1706 grew very poorly.     

Strain difference in the induction of T-cell activation-associated, interferon gamma-dependent hepatic injury in mice

A single intravenous injection of concanavalin A (Con A) induces T-cell activation-associated inflammatory injury selectively in the liver. This study investigated the strain difference in the development of Con A-induced hepatic injury. Normal C57BL/6 and BALB/c spleen cells produced comparable levels of T-cell-derived lymphokines (interferon gamma [IFN-gamma], tumor necrosis factor alpha [TNF-alpha], and interleukin-2 [IL-2]) following in vitro stimulation with Con A. A single intravenous injection of Con A to C57BL/6 mice induced the plasma levels of TNF-alpha and IL-2 comparable with or slightly higher than those observed in BALB/c mice, whereas the same treatment resulted in an apparently lower level of IFN-gamma production in C57BL/6 mice. RNA from livers of Con A-treated C57BL/6 mice exhibited lower levels of IFN-gamma mRNA than RNA of BALB/c livers. Unexpectedly, a dramatic difference in the severity of hepatic injury was observed between C57BL/6 and BALB/c. Namely, the peak alanine transaminase (ALT) level was more than 15,000 U/L and inducible as early as 8 hours after injection of 0.2 mg Con A per mouse in the C57BL/6 strain, whereas the peak was approximately 3,000 U/L and induced as late as 24 hours after Con A injection in the BALB/c strain. The increase in plasma ALT levels was limited to less than 10% by injection of anti-IFN-gamma monoclonal antibody (mAb) in both strains. The C57BL/6 strain inducing lower levels of IFN-gamma exhibited higher IFN-gamma responsiveness as exemplified by the intrahepatic expression of an IFN-gamma-inducible gene, an inducible type of nitric oxide (NO) synthase (iNOS). These results indicate that, while IFN-gamma produced in vivo by activated T cells induces hepatic injury, there exists a striking strain difference in the induction of IFN-gamma-dependent hepatic injury.     

Mouse adenovirus type-1 replication is restricted to vascular endothelium in the CNS of susceptible strains of mice

Previous studies have shown that mouse adenovirus type-1 (MAV-1) caused a fatal hemorrhagic encephalitis in certain strains of mice. C57BI/6 mice exhibited 100% mortality when given as little 10(3) plaque-forming units (PFU) of MAV, in contrast to BALB/c mice which were resistant to as many as 10(6) PFU. Susceptible animals died with a flaccid paralysis on the 3rd or 4th day after inoculation. The brains and spinal cords of these animals displayed numerous petechial hemorrhages that were found in virtually all areas of the brain, but were more numerous in white matter. In this paper, immunohistochemistry and electron microscopy were used to identify the viral target of replication within the CNS of susceptible mice. These studies showed that the CNS vascular endothelial cell was the primary site of viral replication within the CNS of mice infected with MAV-1. Characterization of cytokine mRNA levels and disease course in immunodeficient mice revealed that the host immune response played little, if any, role in the pathogenesis of MAV-1 disease in susceptible mice and was not responsible for the resistance of BALB/c mice. These results support the conclusion that disease course and outcome in susceptible and resistant strains of mice were determined primarily by the ability of the virus to replicate within the CNS vascular endothelium.     

A critical role for IL-4 in regulating disease severity in experimental allergic encephalomyelitis as demonstrated in IL-4-deficient C57BL/6 mice and BALB/c mice

Experimental allergic encephalomyelitis (EAE) is a T cell-mediated autoimmune disease of the central nervous system (CNS) that has served as the principal experimental model for multiple sclerosis (MS). Susceptibility to disease is thought to correlate with the ability to generate a Th1-type cytokine profile in myelin-responsive T cells, whereas T cells producing a Th2 cytokine pattern, in particular IL-4, are thought to be nonencephalitogenic and also to confer protection against a Th1-type response. However, recent studies using a variety of genetically engineered animals in which the genes for Th1-type cytokines and/or their receptors have been inactivated have called into question the Th1-Th2 paradigm in experimental allergic encephalomyelitis. In this report we have addressed the contribution of IL-4 to disease expression by studying two strains of mice, C57BL/6 and BALB/c, in which the gene for IL-4 has been inactivated. The IL-4-deficient C57BL/6 mice, and to a lesser extent the IL-4-deficient BALB/c mice, developed a more severe form of clinical disease, a more extensive pathologic involvement of the spinal cord, and an increased expression of proinflammatory cytokines in the CNS than their wild-type littermates. BALB/c and C57BL/6 mice showed a slightly different cytokine profile in the CNS. Both groups of animals recovered from the acute clinical episode in a time frame that was essentially identical to that found in the wild-type controls. We conclude that IL-4 plays an important role in modulating the severity of the encephalitogenic process, but does not by itself contribute to spontaneous remission from the disease.     

Effect of intracerebral administration of Corynebacterium parvum on the growth of brain tumors in mice

The effect of intracerebral administration of Corynebacterium parvum (C. parvum) on the growth of syngeneic brain tumors in C57BL/6 mice and the mechanism of its action were investigated. Mice were inoculated with 10(4) malignant glioma cells intracerebrally, and treated with various doses of C parvum on day 6 after tumor inoculation. The growth of tumors was significantly inhibited in proportion ot the dose of C. parvum. The cytotoxic activity of effector cells was enhanced when C. parvum was administered at the site of tumor inoculation. Significant cytotoxic activity was observed in the adherent cell fraction of brain mononuclear cells, while less cytotoxic activity was observed in the nonadherent cell fraction. These results indicate that activated intracranial macrophages may participate in the tumoricidal effect of intracerebral C. parvum administration.