Strain differences in the somnogenic effects of interferon inducers in mice

Host genetics play a critical role in controlling CD8 T cell function and lethal immunopathology during chronic viral infection

Effective CD8 T cell responses are vital for the control of chronic viral infections. Many factors of the host immune response contribute to the maintenance of effector CD8 T cell responses versus CD8 T cell exhaustion during chronic infection. Specific MHC alleles and the degree of MHC heterogeneity are associated with enhanced CD8 T cell function and viral control during human chronic infection. However, it is currently unclear to what extent host genetics influences the establishment of chronic viral infection. In order to examine the impact of MHC heterogeneity versus non-MHC host genetics on the development of chronic viral infection, an F1 cross of B10.D2 x B6 (D2B6F1) and BALB.B x BALB/c (BCF1) mice were infected with the clone-13 (Cl-13) strain of lymphocytic choriomeningitis virus (LCMV). Following chronic Cl-13 infection both H-2^bxd D2B6F1 and BCF1 mice demonstrated increased viral control compared to homozygous mice. Strikingly, H-2^bxd D2B6F1 mice on a C57BL genetic background exhibited mortality following Cl-13 infection. CD8 T cell depletion prevented mortality in Cl-13-infected D2B6F1 mice indicating that mortality was CD8 T-cell-dependent. D2B6F1 mice maintained more CD8 T cell effector cytokine production and exhibited reduced expression of the T cell exhaustion marker PD-1. In addition, D2B6F1 mice also induced a larger Th1 response than BCF1 mice and Cl-13-induced mortality in D2B6F1 mice was also dependent on CD4 T-cell-mediated IFN-γ production. Thus, following a chronic viral infection, increased functionality of the CD8 T cell response allowed for more rapid viral clearance at the cost of enhanced immunopathology dependent on both MHC diversity and the genetic background of the host.

Chronic viral infections pose a serious healthcare concern resulting in substantial mortality worldwide. Chronic viral infections result from the inability of the immune system to eliminate the virus from the infected individual. The immune system’s inability to eradicate the invading pathogen is partially due to excessive regulation of the T cell response. However, host genetics have been associated with enhanced T cell function and viral control during chronic infection. Therefore, we sought to investigate the role of host genetic diversity on the T cell response during chronic viral infection in a murine model. We found that increasing MHC heterogeneity resulted in an increased T cell response and enhanced viral control. In addition, host genetic background differences allowed for induction of a distinct CD4 T cell subset, which was associated with reduced suppression of the CD8 T cell response and enhanced viral control. Thus, specific features of the host genetic background contribute to the size and quality of the T cell response and resulting viral control. This study identifies components of the T cell response that may provide a therapeutic target to enhance T-cell-mediated viral control during chronic infection.

Influenza, immune system, and pregnancy

Influenza is a major health problem worldwide. Both seasonal influenza and pandemics take a major toll on the health and economy of our country. The present review focuses on the virology and complex immunology of this RNA virus in general and in relation to pregnancy. The goal is to attempt to explain the increased morbidity and mortality seen in infection during pregnancy. We discuss elements of innate and adaptive immunity as well as placental cellular responses to infection. In addition, we delineate findings in animal models as well as human disease. Increased knowledge of maternal and fetal immunologic responses to influenza is needed. However, enhanced understanding of nonimmune, pregnancy-specific factors influencing direct interaction of the virus with host cells is also important for the development of more effective prevention and treatment options in the future.

Mapping complex traits using families of recombinant inbred strains: an overview and example of mapping susceptibility to Candida albicans induced illness phenotypes

This overview and data-based example indicate how large families of recombinant inbred (RI) strains can be used to identify genetic loci and genes that underlie complex phenotypic differences among inbred mice. The RI approach requires no a priori expectations or assumptions about mechanisms that influence the phenotype, other than that variability is partly heritable. RI strains, which are produced by inbreeding the F2 progeny of two parental strains for at least 20 generations, have two major advantages. First, numerous subjects with identical genotypes can be analyzed to determine the average phenotype associated with that genotype, and second, it becomes practical to systematically accumulate large genome and phenome data sets for entire RI families, including sequence data, transcriptomes for many organs, and cell types and extensive data on gene-by-pathogen interactions. This enables the construction of far more sophisticated models of disease cause and progression. To illustrate the use of the systems genetics approach to infectious disease, we designed a simple study using three complementary families of RI strains (CXB, BXD, and AXB/BXA) that are differentially susceptible to intravenous challenge with the yeast Candida albicans.

Sleep and behavior during vesicular stomatitis virus induced encephalitis in BALB/cJ and C57BL/6J mice

Intranasal application of vesicular stomatitis virus (VSV) produces a well-characterized model of viral encephalitis in mice. Within one day post-infection (PI), VSV travels to the olfactory bulb and, over the course of 7 days, it infects regions and tracts extending into the brainstem followed by clearance and recovery in most mice by PI day 14 (PI 14). Infectious diseases are commonly accompanied by excessive sleepiness; thus, sleep is considered a component of the acute phase response to infection. In this project, we studied the relationship between sleep and VSV infection using C57BL/6 (B6) and BALB/c mice. Mice were implanted with transmitters for recording EEG, activity and temperature by telemetry. After uninterrupted baseline recordings were collected for 2 days, each animal was infected intranasally with a single low dose of VSV (5×10(4) PFU). Sleep was recorded for 15 consecutive days and analyzed on PI 0, 1, 3, 5, 7, 10, and 14. Compared to baseline, amounts of non-rapid eye movement sleep (NREM) were increased in B6 mice during the dark period of PI 1-5, whereas rapid eye movement sleep (REM) was significantly reduced during the light periods of PI 0-14. In contrast, BALB/c mice showed significantly fewer changes in NREM and REM. These data demonstrate sleep architecture is differentially altered in these mouse strains and suggests that, in B6 mice, VSV can alter sleep before virus progresses into brain regions that control sleep.

Environmental perturbation, inflammation and behavior in healthy and virus-infected mice

The development of so-called "sickness behaviors" (e.g., anorexia, anhedonia, reduced social interaction, fatigue) during infectious and inflammatory disease has been linked to facets of the immune response. Such problems can be particularly troublesome during chronic latent infection, as the host immune system must employ continual vigilance to maintain viral latency. Epstein-Barr virus (EBV) is a ubiquitous human gamma-herpesvirus that causes acute disease and establishes life-long latency in people. Murine gammaherpesvirus (MuGHV) is a natural pathogen of wild rodents that provides an experimental model for studying the pathophysiology of an EBV-like gamma-herpesvirus in mice. To evaluate this model with regard to sickness behavior and its exacerbation during a chronic latent viral disease, we exposed uninfected and MuGHV-infected C57BL/6J and BALB/cByJ mice to novel and potentially stressful environmental perturbations and measured the impact of these challenges on behavior and markers of inflammation. The data indicate that exposure of mice to environmental perturbations during the normal somnolent phase is associated with reduced activity during the subsequent active phase, despite an intervening rest period. Effects on inflammatory mediators were complex due to independent and interactive effects of infection status, mouse strain, and exposure to stressful environment. However, GCSF and MCP1 were consistently elevated in lung both immediately after and 12h after exposure to a "dirty" cage containing the resident mouse (DCR); this increase occurred in both C57BL/6J and BALB/cByJ mice and was independent of infection status. At 12h after DCR, IL1β and IP10 were also consistently elevated in lung. In response to DCR, BALB/cByJ mice showed a greater number of significant cytokine effects than did C57BL/6J mice. With regard to infection status, IP10 was consistently elevated in lung at both time points regardless of mouse strain or DCR exposure. Several analytes were affected by mouse strain in serum or lung at one or both time points, with most strain differences present in serum at E18. Taken together, the data show that exposure of mice to environmental perturbations is associated with systemic inflammation that is in part independent of genetic background or latent MuGHV infection and with reduced activity that could represent fatigue, depression, or other facets of sickness behavior.

Inhibition of LiCl-induced conditioning of anticipatory nausea in rats following immune system stimulation: comparing the immunogens lipopolysaccharide, muramyl dipeptide, and polyinosinic: polycytidylic acid

The effects of the bacterial endotoxins, lipopolysaccharide (LPS) and muramyl dipeptide (MDP; Experiment 1), and the viral mimetic, polyinosinic: polycytidylic acid (poly I:C; Experiment 2), on the acquisition of "conditioned gaping" behavior in the rodent model of LiCl-induced anticipatory nausea were examined. Experimentally naïve adult male Long-Evans rats were injected (intraperitoneal, i.p.) with either 200 μg/kg LPS, 1.6 mg/kg MDP, or 0.9% saline (Experiment 1), or 4.0 mg/kg poly I:C or 0.9% saline (Experiment 2), 90 min prior to treatment with 127 mg/kg LiCl or saline control and immediately placed into a distinctive context for 30 min (repeated over 4 conditioning days, spaced 72 h apart). On a drug-free test day (72 h following conditioning day 4), each animal was re-exposed to the context for 10 min, and orofacial and aversive behavioral responses were video recorded and analyzed. The results showed that pre-treatment with LPS, MDP (Experiment 1), or poly I:C (Experiment 2) prior to LiCl+context conditioning significantly impaired the establishment of conditioned gaping behavior, thus blocking the acquisition of anticipatory nausea. Results varied in regards to peripheral acute-phase response sickness behaviors, with significantly reduced weight loss in LPS-treated animals, less robust weight loss in poly I:C-treated animals, and no significant reductions in body weight in MDP-treated animals. The learning impairments observed in the current study suggest that endotoxin treatment with bacterial and viral endotoxin may have stronger central effects on learning and memory behavior, relative to peripheral effects on body weight and other sickness-related responses.

Evidence for neuroinflammatory and microglial changes in the cerebral response to sleep loss

STUDY OBJECTIVES

Sleep loss has pro-inflammatory effects, but the roles of specific cell populations in mediating these effects have not been delineated. We assessed the modulation of the electroencephalographic and molecular responses to sleep deprivation (S-DEP) by minocycline, a compound that attenuates microglial activation occurring in association with neuroinflammatory events.

DESIGN

Laboratory rodents were subjected to assessment of sleep and wake in baseline and sleep deprived conditions.

PARTICIPANTS

Adult male CD-1 mice (30-35 g) subjected to telemetric electroencephalography.

INTERVENTIONS

Minocycline was administered daily. Mice were subjected to baseline data collection on the first day of minocycline administration and, on subsequent days, 2 S-DEP sessions, 1 and 3 h in duration, followed by recovery sleep. Following EEG studies, mice were euthanized either at the end of a 3 h S-DEP or as time-of day controls for sampling of brain messenger RNAs. Gene expression was measured by real-time polymerase chain reaction.

MEASUREMENTS AND RESULTS

Minocycline-treated mice exhibited a reduction in time spent asleep, relative to saline-treated mice, in the 3-h interval immediately after administration. S-DEP resulted in an increase in EEG slow wave activity relative to baseline in saline-treated mice. This response to S-DEP was abolished in animals subjected to chronic minocycline administration. S-DEP suppressed the expression of the microglial-specific transcript cd11b and the neuroinflammation marker peripheral benzodiazepine receptor, in the brain at the mRNA level. Minocycline attenuated the elevation of c-fos expression by S-DEP. Brain levels of pro-inflammatory cytokine mRNAs interleukin-1β (il-1β), interleukin-6 (il-6), and tumor necrosis factor-α (tnfα) were unaffected by S-DEP, but were elevated in minocycline-treated mice relative to saline-treated mice.

CONCLUSIONS

The anti-neuroinflammatory agent minocycline prevents either the buildup or expression of sleep need in rodents. The molecular mechanism underlying this effect is not known, but it is not mediated by suppression of il-1β, il-6, and tnfα at the transcript level.

Sleep and psychoneuroimmunology

The brain uses a variety of mechanisms to survey the immune system constantly. Responses of the immune system to invading pathogens are detected by the central nervous system, which responds by orchestrating complex changes in behavior and physiology. Sleep is one of the behaviors altered in response to immune challenge. The role of cytokines as mediators of responses to infectious challenge and regulators and modulators of sleep is the focus of this article.

Genetic susceptibility and resistance to influenza infection and disease in humans and mice

Although genetic risk factors for influenza infection have not yet been defined in people, differences in genetic background and related variation in the response to infection, as well as viral virulence, are all likely to influence both the likelihood of infection and disease severity. However, apart from characterization of viral binding sites in avian and mammalian hosts, relatively little investigation has focused on host genetic determinants of susceptibility or resistance to infection, or the severity of the associated disease in humans or other species. Similarly, the role of genetic background in the generation of an efficacious immune response to either infection or vaccination has not been extensively evaluated. However, genetic influences on susceptibility and resistance to numerous infectious agents and on the resultant host inflammatory and immune responses are well established in both humans and other animals. Mouse-adapted strains of human influenza viruses and the use of inbred strains of laboratory mice have supported extensive characterization of the pathogenesis and immunology of influenza virus infections. Like individual humans, inbred strains of mice vary in their reactions to influenza infection, particularly with regard to the inflammatory response and disease severity, supporting the potential use of these mice as a valuable surrogate for human genetic variation. Relying heavily on what we have learned from mice, this overview summarizes existing animal, human and epidemiologic data suggestive of host genetic influences on influenza infection.

Polyinosinic:polycytidylic acid induces memory processing deficits in the day-old chick

Anecdotal and experimental evidence has demonstrated that humans and animals exhibit physiological and cognitive alterations in response to sickness and injury. It is now clear that these changes are due to the actions of proinflammatory cytokines. The current study examined the effects of peripheral administration of polyinosinic:polycytidylic acid, a synthetic double-stranded viral RNA, on the memory processes of day-old chicks trained on a single trial passive avoidance task. Polyinosinic:polycytidylic acid impaired performance on the passive avoidance task in a dose-dependent manner. Maximal deficits were observed when 5 g/kg polyinosinic:polycytidylic acid was administered 120 min before training. Tests for retention revealed that interference in memory consolidation appeared between 30 and 40 min after training. These results indicate an inhibitory effect of polyinosinic:polycytidylic acid on the processes of memory formation at the transition from intermediate-term memory phase (A) to intermediate-term memory phase (B) of the Gibbs and Ng model of memory formation. The study also investigated the pyrogenic actions of polyinosinic:polycytidylic acid, and examined the effect of pretreatment with ketoprofen, a cyclooxygenase inhibitor. Significant rises in body temperature were observed 30 min after injection of polyinosinic:polycytidylic acid. Inhibition of cyclooxygenase by ketoprofen ameliorated the polyinosinic:polycytidylic acid-induced deficits in retention and attenuated the increase in body temperature. These results demonstrate that polyinosinic:polycytidylic acid induces memory processing deficits and is pyrogenic in the day-old chick and that these effects are cyclooxygenase-dependent.

Sleep and Psychoneuroimmunology

Personal experience indicates we sleep differently when sick. Data reviewed demonstrate the extent to which sleep is altered during the course of infection of host organisms by several classes of pathogens. One important unanswered question is whether or not the alterations in sleep during infection are of functional relevance. That is, does the way we sleep when sick facilitate or impede recovery? One retrospective, preclinical study suggests that sleep changes during infection are of functional relevance. Toth and colleagues [102] analyzed sleep responses of rabbits to three different microbial infections. Those rabbits that exhibited robust increases in NREM sleep were more likely to survive than those that exhibited long periods of NREM sleep suppression. These tantalizing data suggest that the precise alterations in sleep through the course of infection are important determinants of morbidity and mortality. Data from healthy subjects demonstrate a role for at least two cytokines in the regulation of spontaneous, physiologic NREM sleep. A second critical yet unanswered question is whether or not cytokines mediate infection-induced alterations in sleep. The hypothesis that cytokines mediate infection-induced alterations in sleep is logical based on observations of the impact of infection on levels of cytokines in the peripheral immune system and in the brain. No attempts have been made to intervene with cytokine systems in brain during the course of infection to determine if there is an impact on infection-induced alterations in sleep. Although substantial progress has been made in elucidating the myriad mechanisms by which cytokines regulate and modulate sleep, much remains to be determined with respect to mechanistic and functional aspects of infection-induced alterations in sleep.

Behavioral and physiological effects of a single injection of rat interferon-alpha on male Sprague-Dawley rats: a long-term evaluation

Interferon-alpha (IFN-alpha) is a cytokine used as a first line of defense against diseases such as cancer and hepatitis C. However, reports indicate that its effectiveness as a treatment is countered by central nervous system (CNS) disruptions in patients. Our work explored the possibility that it may also cause long-term behavioral disruptions by chronicling the behavioral and physiological disturbances associated with a single injection of vehicle, 10, 100, or 1,000 units of IFN-alpha in male Sprague-Dawley rats (n = 5/dose). Following 1 day of locomotor baseline collection, we monitored sickness behaviors (ptosis, piloerection, lethargy, and sleep), food and water intake, body weight, temperature, and motor activity. Observations were recorded 4 days prior to and 4 days following the IFN-alpha injection. Temperature and sickness behaviors were recorded three times daily at 9:00, 15:00, and 21:00 h, and all other indices, once daily. On the injection day, temperature values were highest in the animals receiving the 10-unit IFN-alpha dose 15 min and 13 h post-injection. In the case of sickness behaviors, a significant increase was observed in piloerection in all IFN-alpha groups at each time point measured, while the scores of the rats in the vehicle condition remained unchanged between pre- and post-injection days. Analyses of overall sickness behaviors during morning and night observation periods indicated increased scores in all IFN-alpha groups following injection. Cumulatively, these data suggest that a single IFN-alpha exposure may elicit long-term behavioral disruptions and that its consequences should be thoroughly investigated for its use in clinical populations.

Sleep and body temperature responses in an acute viral infection model are altered in interferon type I receptor-deficient mice

Type I interferons (IFNs) include IFNalpha and IFNbeta, both of which are elevated in acute viral infections and both of which have been shown to induce symptoms such as fever and somnolence when administered in pharmacological doses. To investigate the role of type I IFNs in mediation of acute respiratory viral symptoms we examined sleep and body temperature responses in mice with a targeted mutation of the IFN receptor type I (IFN-RI knockouts). IFN-RI knockouts (KOs) or wild-type 129 SvEv controls were challenged intratracheally (IT) with combined poly[rI.rC] (synthetic double-stranded RNA) and IFNgamma, a model that simulates an acute viral infection with respect to body temperature and locomotor activity responses. Control mice of both strains were treated with IT IFNgamma alone. Hypothermic responses to IT poly[rI.rC]/IFNgamma were more exaggerated in the IFN-RI KO mice than in wild-type. The non-rapid eye movement sleep (NREMS) response to IT poly[rI.rC]/IFNgamma was increased earlier in the IFN-RI KO mice than in wild-type, though the total time spent in NREMS was reduced in the KOs compared to wild-type and the return to baseline NREMS was faster in the KOs. The quality of NREMS also was altered more extensively in the wild-type than in the KO mice. Spontaneous rapid eye movement sleep (REMS) was suppressed in IFN-RI KOs as previously reported, but was not substantially altered in either mouse strain by IT poly[rI.rC]/IFNgamma challenge. Our results implicate type I IFNs as inhibitors of the hypothermic response and enhancers of the NREMS response to IT poly[rI.rC]/IFNgamma, a model of acute viral infection.

Mice deficient in the interferon type I receptor have reduced REM sleep and altered hypothalamic hypocretin, prolactin and 2′,5′-oligoadenylate synthetase expression

We report that mice with a targeted null mutation in the interferon type I receptor (IFN-RI), which cannot respond to such IFNs as IFNalpha and IFNbeta, have a 30% reduction in time spent in spontaneous rapid eye movement sleep (REMS) as a consequence of a reduced number of REMS episodes. Time spent in nonrapid eye movement sleep (NREMS) was essentially unaltered in IFN-RI knockouts (KOs) compared to 129 SvEv controls. Body temperature and locomotor activity were similar in both strains of mice. Hypothalamic expression of mRNAs for molecules previously linked to sleep-wake regulation and an IFN-inducible antiviral gene, 2',5'-oligoadenylate synthetase 1a (OAS), were determined by real-time reverse-transcriptase polymerase chain reaction (RT2-PCR). The level of hypocretin A mRNA was elevated in IFN-RI KO mice compared to 129 SvEv mice, while prolactin mRNA and OAS mRNA levels were suppressed. Vasoactive intestinal peptide (VIP) and corticotropin-releasing hormone (CRH) mRNA levels were unchanged relative to controls. Serum prolactin levels were similar in both strains. Results are consistent with the hypothesis that increased hypocretin and reduced prolactin in the hypothalamus of IFN-RI KO mice are responsible for their reduced REMS. In addition, the reduced OAS expression may result in modulation of prolactin receptor signaling and thus contribute to suppression of REMS.

Macrophage participation in influenza-induced sleep enhancement in C57BL/6J mice

Mice develop changes in sleep during the nonspecific immune response that occurs during the initial few days after inoculation with influenza virus. T lymphocytes, neutrophils, macrophages, and natural killer (NK) cells all participate in the early host response to influenza infection. All of these cell types are potential sources of endogenous substances that modulate sleep, but the contributory role of each cell type to the alteration of somnolence during infection has not been determined. To investigate which cell types contribute to the sleep enhancement that develops during influenza infection in mice, the sleep patterns of C57BL/6J mice with perturbations of particular facets of host immune response capabilities were assessed before and after influenza infection. Targeted mutation of the gene Ccl3 (macrophage inflammatory protein 1 alpha) prevented development of the dark phase sleep enhancement that is characteristic of C57BL/6J mice after influenza infection. Other experimental treatments that impair macrophage or monocyte function also produced significant (administration of pentoxifylline or CNI-1493) or marginally significant (deletion of the interferon-gamma gene or intranasal administration of carrageenan) changes in influenza-induced sleep enhancement in C57BL/6J mice. In contrast, functional impairments of NK cells, neutrophils, and T lymphocytes did not significantly influence sleep responses. These data therefore support a contributory role for macrophages, but not for NK cells, neutrophils, and T lymphocytes, in eliciting the sleep response typical of influenza-infected C57BL/6J mice.

The viral mimic, polyinosinic:polycytidylic acid, induces fever in rats via an interleukin-1-dependent mechanism

Polyinosinic:polycytidylic acid (poly I:C) is a synthetic double-stranded RNA that is used experimentally to model viral infections in vivo. Previous studies investigating the inflammatory properties of this agent in rodents demonstrated that it is a potent pyrogen. However, the mechanisms underlying this response have not been fully elucidated. In the current study, we examined the effects of peripheral administration of poly I:C on body temperature and cytokine production. Male rats were implanted with biotelemetry devices and randomly assigned to one of the following three groups: poly I:C + saline, poly I:C + interleukin-1 receptor antagonist (IL-1ra), or saline + saline. Maximal fever of 1.6 degrees C above baseline was observed 3 h after an intraperitoneal injection of poly I:C (750 microg/kg). Pretreatment with IL-1ra diminished this response by >50% (maximum body temperature = 0.6 degrees C above baseline). Plasma IL-6 concentration increased fivefold 2 h post-poly I:C compared with saline-injected rats; levels returned to baseline 4 h postinjection. Pretreatment with IL-1ra prevented this rise in IL-6. Plasma tumor necrosis factor (TNF)-alpha was also increased more than fourfold 2 h postinjection but remained unaffected by IL-1ra treatment. IL-1beta and cyclooxygenase-2 mRNA were significantly upregulated in the hypothalamus of poly I:C-treated animals. Finally, poly I:C decreased food intake by 30%, but this response was not altered by pretreatment with IL-1ra. These results suggest that poly I:C induces fever, but not anorexia, through an IL-1 and prostaglandin-dependent mechanism.

Intratracheal double-stranded RNA plus interferon-γ: A model for analysis of the acute phase response to respiratory viral infections

Double-stranded (ds)RNA is made as a by-product of viral replication. Synthetic dsRNA induces virtually all of the same systemic symptoms as acute viral infections, such as fever and malaise. In order to develop a model of respiratory viral infections (such as influenza) suitable for use in gene knockout mice (where the deleted gene may affect viral replication), we examined C57BL/6 mouse body temperature and locomotor activity responses to the synthetic dsRNA polyriboinosinic.polyribocytidylic acid (poly[rI.rC]) introduced via the intratracheal (IT) route. We compared the IT poly[rI.rC] responses to the well-characterized intraperitoneal (IP) poly[rI.rC] responses. IT poly[rI.rC] failed to induce an acute phase response (APR) in mice, in contrast to IP poly[rI.rC]. However, addition of interferon (IFN)gamma to the IT poly[rI.rC] inoculum induced sustained hypothermia and suppressed locomotor activity responses with similar kinetics to those responses seen in acute mouse influenza. We further examined cytokine, antiviral, muscarinic M2 receptor and inducible nitric oxide synthase gene expression at 5 hr in the lungs of IT challenged mice. These studies suggested that priming the lung with IFNgamma could enhance proinflammatory (IL1beta, IL6, TNFalpha) cytokine gene expression and suppress interferon gene expression compared to IT poly[rI.rC] alone. No differences were detected for the other genes examined. While further molecular characterization of the model is required, we demonstrate that IT challenge with combined poly[rI.rC] and IFNgamma closely simulates the APR to an acute respiratory virus, and may serve as a suitable model for analyzing the molecular basis of the viral APR in gene knockout mice.

Cytokine- and microbially induced sleep responses of interleukin-10 deficient mice

Interleukin (IL)-1 and tumor necrosis factor (TNF) promote slow-wave sleep (SWS), whereas IL-10 inhibits the synthesis of IL-1 and TNF and promotes waking. We evaluated the impact of endogenous IL-10 on sleep-wake behavior by studying mice that lack a functional IL-10 gene. Under baseline conditions, C57BL/6-IL-10 knockout (KO) mice spent more time in SWS during the dark phase of the light-dark cycle than did genetically intact C57BL/6 mice. The two strains of mice showed generally comparable responses to treatment with IL-1, IL-10, or influenza virus, but differed in their responses to lipopolysaccharide (LPS). In IL-10 KO mice, LPS induced an initial transient increase and a subsequent prolonged decrease in SWS, as well as profound hypothermia. These responses were not observed in LPS-treated C57BL/6 mice. These data demonstrate that in the absence of endogenous IL-10, spontaneous SWS is increased and the impact of LPS on vigilance states is altered. Collectively, these observations support a role for IL-10 in sleep regulation and provide further evidence for the involvement of cytokines in the regulation of sleep.

The circadian clock mutation alters sleep homeostasis in the mouse

The onset and duration of sleep are thought to be primarily under the control of a homeostatic mechanism affected by previous periods of wake and sleep and a circadian timing mechanism that partitions wake and sleep into different portions of the day and night. The mouse Clock mutation induces pronounced changes in overall circadian organization. We sought to determine whether this genetic disruption of circadian timing would affect sleep homeostasis. The Clock mutation affected a number of sleep parameters during entrainment to a 12 hr light/dark (LD 12:12) cycle, when animals were free-running in constant darkness (DD), and during recovery from 6 hr of sleep deprivation in LD 12:12. In particular, in LD 12:12, heterozygous and homozygous Clock mutants slept, respectively, approximately 1 and approximately 2 hr less than wild-type mice, and they had 25 and 51% smaller increases in rapid eye movement (REM) sleep during 24 hr recovery, respectively, than wild-type mice. The effects of the mutation on sleep are not readily attributable to differential entrainment to LD 12:12 because the baseline sleep differences between genotypes were also present when animals were free-running in DD. These results indicate that genetic alterations of the circadian clock system and/or its regulatory genes are likely to have widespread effects on a variety of sleep and wake parameters, including the homeostatic regulation of sleep.

Animal models of neuroimmune interactions in inflammatory diseases

Animal models have been used successfully to study various aspects of neural-immune interactions. Although different approaches carry certain advantages and disadvantages, current high sensitivity screening and manipulation methods coupled with molecular and genetic approaches can be successfully used to tease out the neural pathways that regulate inflammatory disease and the effects of immune molecules, such as interleukins, on neuronal function and pathology. Newer methodologies that measure gene expression of thousands of genes will in the future add to the ability to evaluate complex systems interactions in whole animal models. This review addresses the advantages and disadvantages of some of these approaches in the context of application to neural-immune interactions.