Plasma Oxylipins Levels in Nonalcoholic Fatty Liver Disease.

BACKGROUND: Activation of innate immunity by gut-derived immunogens such as lipopolysaccharides (LPS) may play an important role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Whether NAFLD-associated lipid disturbances and polyunsaturated fatty acid (PUFA) metabolism in particular contribute to heightened innate immunity, remains to be determined. OBJECTIVE: To determine if oxylipins, metabolic products of PUFA metabolism, enhance innate immune reactivity alone and/or following exposure to LPS. METHODS: Plasma and peripheral blood mononuclear cells (PBMC) were collected from 35 NAFLD patients and 8 healthy controls. Oxylipin levels were documented by HPLC-MS/MS, cytokines (IL-1, IL-6, IL-10, and TNF-α) by ELISA, and chemokine receptors (CCR1 and CCR2) by flow cytometry. RESULTS: Mean plasma levels of four pro-inflammatory oxylipins (Tetranor 12-HETE, 20-HETE, 8-HETrE, and 7-HDoHE) were significantly elevated in NAFLD patients compared to healthy controls. However, the levels did not correlate with the severity of liver injury as reflected by serum aminotransferases, ck18M30, and Fib-4 determinations. In vitro, 20-HETE (0.01-100 nM), the plasma oxylipin with the most significantly elevated plasma levels, did not alter NAFLD or control PBMC cytokine release or enhance the increases in cytokine release following 24 h of LPS exposure. Similarly, 20-HETE alone did not alter PBMC CCR1 or CCR2 expression or LPS-induced downregulation of these receptors. CONCLUSIONS: Pro-inflammatory oxylipin levels are increased in NAFLD, but these metabolites do not appear to drive short-term direct or LPS-induced increases in PBMC cytokine release or chemotaxis.

The Effects of Pathogen-Associated Molecular Patterns on Peripheral Blood Monocytes in Patients with Non-alcoholic Fatty Liver Disease.

Background: Innate immune responses to gut-derived pathogen-associated molecular patterns (PAMPs) have been implicated in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Whether NAFLD patients have increased sensitivity to PAMP exposure has yet to be reported. Methods: Peripheral blood mononuclear cell (PBMC)/monocytes were exposed to lipopolysaccharide (LPS), Pam3CSK4, or BSA conjugated palmitate in vitro. Changes in toll-like receptors (TLR), cytokines, and chemokine receptors (CR) expressions were documented by flow cytometry and/or enzyme-linked immunoabsorbent assays (ELISAs). Results: TLR2 and TLR4 expression were similar at baseline and increased to a similar extent (TLR2) or remained unchanged (TLR4) following PAMP exposure in NAFLD and healthy control (HC) monocytes. Proinflammatory IL-1ß and IL-6 levels were similar at baseline but increased in a concentration-dependent manner to a greater extent in NAFLD PBMCs. CCR1 and CCR2 expressions at baseline were similar and decreased to a similar extent in NAFLD and HC monocytes. The extent of PAMP-induced proinflammatory cytokine release correlated with evidence of hepatocyte injury (CK18M30 levels). Discussion: NAFLD patients have increased proinflammatory cytokine responses following exposure to PAMPs relative to HC subjects. This response is concentration-dependent and correlates with the extent of hepatic injury.

Pro-Inflammatory Signaling Upregulates a Neurotoxic Conotoxin-Like Protein Encrypted Within Human Endogenous Retrovirus-K.

Motor neuron degeneration and spinal cord demyelination are hallmark pathological events in Amyotrophic Lateral Sclerosis (ALS). Endogenous retrovirus-K (ERVK) expression has an established association with ALS neuropathology, with murine modeling pointing to a role for the ERVK envelope (env) gene in disease processes. Here, we describe a novel viral protein cryptically encoded within the ERVK env transcript, which resembles two distinct cysteine-rich neurotoxic proteins: conotoxin proteins found in marine snails and the Human Immunodeficiency Virus (HIV) Tat protein. Consistent with Nuclear factor-kappa B (NF-κB)-induced retrotransposon expression, the ERVK conotoxin-like protein (CTXLP) is induced by inflammatory signaling. CTXLP is found in the nucleus, impacting innate immune gene expression and NF-κB p65 activity. Using human autopsy specimens from patients with ALS, we further showcase CTXLP expression in degenerating motor cortex and spinal cord tissues, concomitant with inflammation linked pathways, including enhancement of necroptosis marker mixed lineage kinase domain-like (MLKL) protein and oligodendrocyte maturation/myelination inhibitor Nogo-A. These findings identify CTXLP as a novel ERVK protein product, which may act as an effector in ALS neuropathology.

The Impact of Gender on Interferon-Associated Depression and Anxiety.

Population studies indicate women have higher prevalences of depression and anxiety than men. Interferon (IFN) is a biologic agent that can induce or exacerbate depression and/or anxiety. Whether women are more likely to experience these side effects of IFN during treatment remains to be determined. The aim of this study was to document levels of depression and anxiety in female and male patients before and during IFN-based treatment. This was a prospective open-label study in which depression was measured by Beck Depression Inventory (BDI) and anxiety by Hospital Anxiety and Depression Scale (HADS). Before treatment, the prevalence of depression was higher in females (3/13 [23%]) than males (1/25 [4%]), but the difference did not reach statistical significance (P = 0.12). Initial BDI scores were also higher in females but not significantly (P = 0.07). During treatment, BDI scores increased to a similar extent in both genders. A similar percentage of nondepressed patients at baseline developed depression (females: 50% versus males: 35%, P = 0.45). Before treatment, anxiety was significantly more common in females (7/13 [54%]) than males (3/25 [12%]) (P = 0.016) and median HADS scores were higher in females (P = 0.03). During treatment, increases in HADS scores were similar in the 2 genders. A similar percentage of patients without anxiety at baseline developed anxiety on treatment (females: 50% versus males: 23%, P = 0.31). The frequency and extent of IFN-induced/exacerbated depression and anxiety are not gender dependent.

The Influence of Hepatitis C Viral Loads on Natural Killer Cell Function.

BACKGROUND: Hepatitis C virus (HCV) infection has a high rate of chronicity, attributable to its capacity to alter host immunity, including natural killer (NK) cell function. In this study, the interaction between NK cell activity and HCV viral load was investigated. METHODS: Peripheral blood NK cells were examined for cytotoxicity and interferon (IFN)-γ expression in HCV infected low (LVL, < 800,000 IU/mL, n = 10) and high (HVL, > 800,000 IU/mL, n = 13) viral load patient cohorts. RESULTS: Spontaneous NK cell cytotoxicity was more robust in the LVL cohort resulting in a negative correlation with viral loads (spontaneous, r = -0.437, P = 0.037; IFN-α activated, r = -0.372, P = 0.081). Although the percent of IFN-γ+ NK cells did not associate with viral load, within the LVL cohort there was a marked increase in IFN-γ+ NK cells upon IFN-α activation relative to medium alone (P < 0.01). To examine the inability of NK cells derived from HVL patients to be further activated, the expression of the exhaustion marker programmed cell death protein (PD)-1 was evaluated. PD-1 expression upon NK cell activation correlated with viral load (r = 0.649, P = 0.009). In addition, HCV proteins upregulated PD-1 expression in vitro (P < 0.05), suggesting that HCV can directly promote NK cell exhaustion. Cells from HVL patients were also more likely to produce IFN-γ in response to HCV core protein. The finding that NK cell PD-1 and IFN-γ expression are linked (r = 0.542, P < 0.05) suggests that increased IFN-γ levels may induce PD-1 as a negative feedback mechanism. CONCLUSIONS: High HCV loads appear to promote NK exhaustion in chronic HCV infection.

In vivo IgE levels in exogenous antigen stimulated responses: measurement of total IgE as a valid, simple surrogate for Ag-specific IgE.

Due to its dependence on IL-4 and IL-13 production, IgE production is frequently used to assess the type 2 character of an immune effector response. It is particularly relevant to measure IgE in murine models of immediate hypersensitivity, as allergen specific IgE is a critical effector molecule in this process. Given the complexity of developing ELISAs to measure specific IgE, total IgE levels are often reported with the implicit assumption that this provides an accurate gauge of specific IgE responses. Here, we rigorously test this assumption by examining the relationship between total and Ag-specific IgE levels in mice immunized to elicit a wide range of serum IgE responses. We identify a strong, consistent relationship between total and Ag-specific IgE, regardless of the phenotype of the immune response (type 1 vs. type 2 biased), the nature of the immune response (primary vs. recall), the genetic background of mouse strain examined (C57Bl/6, BALB/c or outbred CD1 mice), or the intensity of the initial immunological stimulus (0.2, 2.0 or 100 microg OVA). These findings indicate that measurement of total IgE levels through straightforward, easy to develop, total IgE ELISAs offers an appropriate surrogate for measurement of Ag-specific IgE levels, usually measured through the use of subjective PCA assays or Ag-specific IgE ELISAs.

Involvement of fibrinolytic regulators in adhesion of monocytes to vascular endothelial cells induced by glycated LDL and to aorta from diabetic mice.

Diabetes mellitus accelerates the development of atherosclerotic cardiovascular diseases. Monocyte adhesion is an early cellular event of atherogenesis. Elevated levels of glyLDL were common in diabetic patients. Our previous studies indicated that HSF1 and p22-phox (a subunit of the NOX complex) were involved in glyLDL-induced up-regulation of PAI-1 in vascular EC. The present study demonstrated that glyLDL significantly increased the adhesion of monocytes to the surface of cultured human umbilical vein or PAEC. Transfection of siRNA for PAI-1, p22-phox, or HSF1 in EC prevented glyLDL-induced monocyte adhesion to EC. uPA siRNA increased monocyte adhesion to EC. Exogenous uPA reduced monocyte adhesion induced by glyLDL or uPA siRNA. Exogenous PAI-1 restored monocyte adhesion to EC inhibited by PAI-1 siRNA or uPA. GlyLDL-induced monocyte adhesion to EC was inhibited by treatment of EC with RAP, an antagonist for LRP, and enhanced by uPAR antibody. The adhesion of monocytes to aorta from leptin db/db diabetic mice was significantly greater than to that from control mice, which was associated with elevated contents of PAI-1, uPA, p22-phox, and HSF1 in hearts of db/db mice. The results suggest that oxidative stress and fibrinolytic regulators (PAI-1, uPA, and uPAR) are implicated in the modulation of glyLDL-induced monocyte adhesion to vascular endothelium, which may play a crucial role in vascular inflammation under diabetes-associated metabolic disorder.

Baseline Comorbidities Enhance the Risk of Treatment-Induced Depression in HCV-Infected Men: A Pilot Study.

BACKGROUND: Hepatitis C virus (HCV) infection is associated with clinical depression,a condition that is aggravated on interferon-based therapy. In HCV infection, men often appear more resilient to depression than women. However, men are subject to depression in diseases that tend to be comorbid in HCV-infected. AIM: This study examined whether HCV-infected men with baseline comorbidities were more or less susceptible to depression prior to and on treatment. METHODS: Patients with chronic HCV infection preparing to begin treatment participated (n = 37). The presence of baseline comorbidities was determined by pretreatment medication regimes. Depression was measured by the Beck Depression Inventory prior to and following 2, 4, 8, and 12 weeks of interferon therapy. RESULTS: At baseline, cohorts with (n = 16) and without (n = 21) comorbidities had equivocal demographics and infection characteristics. Comorbidities did not associate with baseline depression. However, on treatment, men with baseline comorbidities demonstrated an elevated risk for the onset of de novo depression (odds ratio = 19.25; confidence interval = 1.41, 582.14; p = .008). This was not observed for women. Baseline comorbidities did not alter the need for treatment discontinuations or the ability to achieve a sustained viral response. CONCLUSION: The results of this study suggest that baseline comorbidities render men more susceptible to interferon treatment-induced depression.

Distribution of viral hepatitis in indigenous populations of North America and the circumpolar Arctic.

The burden of viral hepatitis among indigenous populations of the United States, Canada and Greenland is greater than in non-indigenous populations. In particular, throughout the circumpolar Arctic regions, chronic hepatitis B infection is highly prevalent, although incidence rates have declined considerably in certain regions due to infant HBV vaccination. Unique HBV (sub)genotypes having distinct clinical outcomes and distribution patterns are also observed within this region. In conjunction with hepatitis B infection, hepatitis delta infection is also apparent within North American indigenous peoples, particularly with outbreaks in Greenlandic Inuit communities. Incidence rates for hepatitis C infection are higher for indigenous populations within the United States and Canada; however, some hepatitis C antibody-positive indigenous patients are more likely to be HCV RNA-negative compared to non-indigenous patients. Thus, an increased understanding of the epidemiology, clinical consequences and pathogenicity of viral hepatitis affecting the indigenous populations will help to address and balance the burden of infection.

Preliminary analysis of immune activation in early onset type 2 diabetes.

INTRODUCTION: First Nations and other Aboriginal children are disproportionately affected by cardiometabolic diseases, including type 2 diabetes (T2D). In T2D, the disruption of insulin signalling can be driven by pro-inflammatory immunity. Pro-inflammatory responses can be fueled by toll-like receptors (TLR) on immune cells such as peripheral blood mononuclear cells (PBMC, a white blood cell population). TLR4 can bind to lipids from bacteria and food sources activating PBMC to produce cytokines tumour necrosis factor (TNF)-α and interleukin (IL)-1ß. These cytokines can interfere with insulin signalling. Here, we seek to understand how TLR4 activation may be involved in early onset T2D. We hypothesized that immune cells from youth with T2D (n = 8) would be more reactive upon TLR4 stimulation relative to cells from age and body mass index (BMI)-matched controls without T2D (n = 8). METHODS: Serum samples were assayed for adipokines (adiponectin and leptin), as well as cytokines. Freshly isolated PBMC were examined for immune reactivity upon culture with TLR4 ligands bacterial lipopolysaccharide (LPS, 2 and 0.2 ng/ml) and the fatty acid palmitate (200 µM). Culture supernatants were evaluated for the amount of TNF-α and IL-1ß produced by PBMC. RESULTS: Youth with T2D displayed lower median serum adiponectin levels compared to controls (395 vs. 904 ng/ml, p < 0.05). PBMC isolated from youth with and without T2D produced similar levels of TNF-α and IL-1ß after exposure to the higher LPS concentration. However, at the low LPS dose the T2D cohort exhibited enhanced IL-1ß synthesis relative to the control cohort. Additionally, exposure to palmitate resulted in greater IL-1ß synthesis in PBMCs isolated from youth with T2D versus controls (p < 0.05). These differences in cytokine production corresponded to greater monocyte activation in the T2D cohort. CONCLUSION: These preliminary results suggest that cellular immune responses are exaggerated in T2D, particularly with respect to IL-1ß activity. These studies aim to improve the understanding of the biology behind early onset T2D and its vascular complications that burden First Nations people.

Hepatitis C virus in American Indian/Alaskan Native and Aboriginal peoples of North America.

Liver diseases, such as hepatitis C virus (HCV) infection, are "broken spirit" diseases. The prevalence of HCV infection for American Indian/Alaskan Native (AI/AN) in the United States and Canadian Aboriginals varies; nonetheless, incidence rates of newly diagnosed HCV infection are typically higher relative to non-indigenous people. For AI/AN and Aboriginal peoples risk factors for the diagnosis of HCV infection can reflect that of the general population: predominately male, a history of injection drug use, in midlife years, with a connection with urban centers. However, the face of the indigenous HCV infected individual is becoming increasingly female and younger compared to non-indigenous counterparts. Epidemiology studies indicate that more effective clearance of acute HCV infection can occur for select Aboriginal populations, a phenomenon which may be linked to unique immune characteristics. For individuals progressing to chronic HCV infection treatment outcomes are comparable to other racial cohorts. Disease progression, however, is propelled by elevated rates of co-morbidities including type 2 diabetes and alcohol use, along with human immunodeficiency virus (HIV) co-infection relative to non-indigenous patients. Historical and personal trauma has a major role in the participation of high risk behaviors and associated diseases. Although emerging treatments provide hope, combating HCV-related morbidity and mortality will require interventions that address the etiology of broken spirit diseases.

The potential influence of KIR cluster profiles on disease patterns of Canadian Aboriginals and other indigenous peoples of the Americas.

Genetic differences in immune regulators influence disease resistance and susceptibility patterns. There are major health discrepancies in immune-mediated diseases between Caucasians and Canadian Aboriginal people, as well as with other indigenous people of the Americas. Environmental factors offer a limited explanation as Aboriginal people also demonstrate a rare resistance to chronic hepatitis C virus infection. Killer immunoglobulin-like receptors (KIRs) are known modulators of viral responses and autoimmune diseases. The possibility that variation in KIR cluster profiles contribute to the health outcomes of Aboriginal people was evaluated with Canadian Caucasian (n=93, population controls) and Aboriginal (n=86) individuals. Relative to Caucasians, the Aboriginal KIR cluster displayed a greater immune activating phenotype associated with genes of the B haplotype situated within the telomeric region. In conjunction, there was a decrease in the genes of the B haplotype from the centromeric region. Caucasian and Aboriginal cohorts further demonstrated distinct genotype and haplotype relationships enforcing the disconnect between the B haplotype centromeric and telomeric regions within the Aboriginal population. Moreover, Caucasian KIR cluster patterns reflected studies of Caucasians globally, as well as Asians. In contrast, the unique pattern of the Canadian Aboriginal cohort mirrored the phenotype of other indigenous peoples of the Americas, but not that of Caucasians or Asians. Taken together, these data suggest that historically indigenous peoples of the Americas were subject to immune selection processes that could be influencing the current disease resistance and susceptibility patterns of their descendents.

Activation of ß-adrenergic receptors increases the in vitro migration of malignant hepatocytes.

AIM: Activation of adrenergic receptors (AR) has been reported to enhance the growth and invasion of various malignancies. The effects of AR agonists on malignant hepatocyte proliferation and migration have yet to be determined. METHODS: PLC/PRF/5 (PLC) and Huh-7 cells were exposed to a wide range of concentrations of the AR agonists noradrenaline (NA) and isoprenaline. Cell proliferation, migration, intracellular cyclic adenosine monophosphate (cAMP), protein kinase A (PKA) and C (PKC), matrix metalloproteinases (MMP)-2, -3, -7 and -9, and α(1) -, ß(1) - and ß(2) -AR expression were documented in both cell lines. RESULTS: Cell proliferative activity was unaltered following exposure to physiological and stress-related concentrations of AR agonists but migration was accelerated, an effect that was inhibited by the nonselective ß-AR antagonist labetalol. cAMP, PKA, PKC or MMP expression remained unchanged. Although α(1) - and ß(1) -AR expressions were abundant, ß(2) -AR expression was limited in both cell lines. CONCLUSION: Unlike other malignancies studied to date, in this study, the proliferative activity of malignant hepatocytes was not increased by exposure to AR agonists, a finding that could be explained by downregulation of ß(2) -AR expression. The increase in malignant hepatocyte migration observed remains unexplained but does not appear to involve adenyl cyclase or MMP signaling pathways.

Impact of aboriginal ethnicity on HCV core-induced IL-10 synthesis: interaction with IL-10 gene polymorphisms.

UNLABELLED: The host immune response is a critical determinant in viral infection outcome. Epidemiological studies indicate that North American indigenous peoples are more resistant to chronic HCV infection than other populations. Due to the prominence of IL-10 in chronic HCV infection, we investigated the genetic tendency to produce IL-10 in Caucasian (CA) and First Nation (FN) populations. Peripheral blood mononuclear cells (PBMCs) from CA subjects had a greater tendency to produce IL-10 defined by allelic polymorphisms, as well as genotypes and haplotypes, at the -1082, -819, and -592 positions of the IL-10 promoter. More importantly, we directly evaluated the influence of ethnicity on the ability of HCV core protein to induce IL-10 synthesis and found significantly higher IL-10 production by PBMCs isolated from healthy CA subjects compared with FN subjects. Further examination of the underlying relationship between core-induced IL-10 with the high, intermediate, and low phenotypes at the -1082, -819, and -592 position revealed that spontaneous and core-induced IL-10 synthesis tended to interact negatively with defined polymorphisms. This was particularly evident for the FN cohort, in which the relationship was strengthened by a stronger interaction of core with the low-IL-10-producing phenotypes. As with previous studies, concanavalin A induced IL-10 synthesis from the CA cohort positively associated with defined genetic phenotypes. CONCLUSION: Cells from FN subjects had a reduced capacity to produce IL-10 in response to HCV core protein, suggesting that reduced susceptibility of FN immunity to virally induced IL-10 synthesis might contribute to epidemiological observations of enhanced HCV clearance.

Prevention of allergen-specific, Th2-biased immune responses in vivo: role of increased IL-12 and IL-18 responsiveness.

The factors that control development of adaptive responses to exogenous Ag remain incompletely understood. An ability to selectively direct immunity toward a specific phenotype would be of clinical benefit in numerous immunological disorders. Administration of chemically modified allergen glutaraldehyde-polymerized OVA (OA-POL) leads to >90% reductions in murine IgE and >500-fold increases in IgG2c responses that develop upon subsequent immunization with native Ag. In the present study, we examine the mechanisms underlying this reorientation of the type 2 dominant response that would normally develop. Lack of endogenous IL-12 or IFN-gamma results in markedly reduced induction of IgG2c responses following OA-POL treatment, but only IFN-gamma(-/-) mice demonstrate reduced capacity to prevent IgE induction. This indicates that while both IL-12 and IFN-gamma are critical promoters of type 1 immunity, only IFN-gamma is required to maximally inhibit development of type 2 immune responses. Compared with OVA-immunized mice, CD69(+) T cells from OA-POL-immunized mice demonstrate elevated IL-12Rbeta(2), IL-18Ralpha, and IL-18Rbeta mRNA levels, as well as increased IFN-gamma production in response to rIL-12 or rIL-18 stimulation. Collectively, these data indicate that preventing induction of type 2 immune responses is critically dependent on altered T cell responsiveness to these cytokines. The finding that targeted, Ag-specific manipulation of IL-12 and IL-18 responsiveness can be used to shape the phenotype of the dominant immune response that develops suggests that specifically targeting IL-12 and IL-18 receptor expression may offer clinical options for clinical prophylaxis or intervention.

Antigen-specific versus total immunoglobulin synthesis: total IgE and IgG1, but not IgG2a levels predict murine antigen-specific responses.

BACKGROUND: Induction of an effective antibody (Ab) response requires delivery of multiple signals to B cells. Cross-linking of the B cell antigen receptor (BCR), signaling through CD40 and CD80/86 and cytokine signals combine to induce class switching and expression of specific isotypes. These signals are principally derived from activated, antigen (Ag)-specific T cells. In contrast, IFNgamma, the only cytokine known to induce class switch to IgG2a, can be produced systemically by activated NK or NKT cells, suggesting that Ag-nonspecific signals may also regulate IgG2a production. METHODS: Given the potential differences in regulation between IgE/IgG1 versus IgG2a, we immunized mice on day 0 with ovalbumin (OVA) in the presence of strong type-1- or type-2-immunity-inducing adjuvants and boosted mice 4 weeks later. Mice were bled during the primary immune response and after boost to assess primary and recall Ab responses. RESULTS: Regardless of strain of mice used, phenotype (type 1 versus type 2 dominated) or nature of the immune response induced (primary versus recall), strong correlations between OVA-specific and total IgE and IgG1 were demonstrated. In contrast, a consistent lack of correlation between OVA-specific and total IgG2a levels was observed in all but BALB/c mice. CONCLUSION: These data indicate that the increase in total levels of IgE/IgG1 isotypes is primarily a result of increased levels of OVA-specific Ab. In contrast, the lack of correlation between total and OVA-specific IgG2a suggests broader activation of IgG2a-producing B cells routinely occurs following exogenous Ag immunization.

Mouse hepatitis virus neurovirulence: evidence of a linkage between S glycoprotein expression and immunopathology.

Differences in disease outcome between the highly neurovirulent MHV-JHM and mildly neurovirulent MHV-A59 have been attributed to variations within the spike (S) glycoprotein. Previously, we found that MHV-JHM neurovirulence was marked by diminished expression of interferon-gamma (IFN-gamma) mRNA and a reduced presence of CD8 T cells in the CNS concomitant with heightened macrophage inflammatory protein (MIP)-1 transcript levels and greater macrophage infiltration relative to MHV-A59 infection. Here, the ability of the S and non-spike genes to regulate these immune responses was evaluated using chimeric viruses. Chimeric viruses WTR13 and S4R22 were made on MHV-A59 variant backgrounds and, respectively, contained the S gene of MHV-A59 and MHV-JHM. Unexpectedly, genes other than S appeared to modulate events critical to viral replication and survival. Unlike unresolving MHV-JHM infections, the clearance of WTR13 and S4R22 infections coincided with strong IFN-gamma transcription and an increase in the number of CD8 T cells infiltrating into the CNS. However, despite the absence of detectable viral titers, approximately 40% of S4R22-infected mice succumbed within 3 weeks, indicating that the enhanced mortality following S4R22 infection was not associated with high viral titers. Instead, similar to the MHV-JHM infection, reduced survival following S4R22 infection was observed in the presence of elevated MIP-1alpha and MIP-1beta mRNA accumulation and enhanced macrophage numbers within infected brains. These observations suggest that the S protein of MHV-JHM influences neurovirulence through the induction of MIP-1alpha- and MIP-1beta-driven macrophage immunopathology.

Differential regulation of innate and adaptive immune responses in viral encephalitis.

Viral encephalitis is a global health concern. The ability of a virus to modulate the immune response can have a pivotal effect on the course of disease and the fate of the infected host. In this study, we sought to understand the immunological basis for the fatal encephalitis following infection with the murine coronavirus, mouse hepatitis virus (MHV)-JHM, in contrast with the more attenuated MHV-A59. Distinct glial cell cytokine and chemokine response patterns were observed within 3 days after infection, became progressively more polarized during the course of infection and with the infiltration of leukocytes. In the brain, MHV-JHM infection induced strong accumulation of IFNbeta mRNA relative to IFNgamma mRNA. This trend was reversed in MHV-A59 infection and was accompanied by increased CD8 T cell infiltration into brain compared to MHV-JHM infection. Increased apoptosis appeared to contribute to the diminished presence of CD8 T cells in MHV-JHM-infected brain with the consequence of a lower potential for IFNgamma production and antiviral activity. MHV-JHM infection also induced sustained mRNA accumulation of the innate immune response products interleukin (IL)-6 and IL-1. Furthermore, high levels of macrophage-inflammatory protein (MIP)-1alpha, MIP-1beta, and MIP-2 mRNA were observed at the onset of MHV-JHM infection and correlated with a marked elevation in the number of macrophages in the brain on day 7 compared to MHV-A59 infection. These observations indicate that differences in the severity of viral encephalitis may reflect the differential ability of viruses to stimulate innate immune responses within the CNS and subsequently the character of infiltrating leukocyte populations.