Restraint stress differentially affects the pathogenesis of an experimental influenza viral infection in three inbred strains of mice

Propranolol reduces IFN-γ driven PD-L1 immunosuppression and improves anti-tumour immunity in ovarian cancer

The immune system plays an important role in controlling epithelial ovarian cancer (EOC). EOC is considered to be a "cold tumour," a tumour that has not triggered a strong response by the immune system. However, tumour infiltrating lymphocytes (TILs) and the expression of programmed cell death ligand (PD-L1) are used as prognostic indicators in EOC. Immunotherapy such as PD-(L)1 inhibitors have shown limited benefit in EOC. Since the immune system is affected by behavioural stress and the beta-adrenergic signalling pathway, this study aimed to explore the impact of propranolol (PRO), a beta-blocker, on anti-tumour immunity in both in vitro and in vivo EOC models. Noradrenaline (NA), an adrenergic agonist, did not directly regulate PD-L1 expression but PD-L1 was significantly upregulated by IFN-γ in EOC cell lines. IFN-γ also increased PD-L1 on extracellular vesicles (EVs) released by ID8 cells. PRO significantly decreased IFN-γ levels in primary immune cells activated ex vivo and showed increased viability of the CD8⁺ cell population in an EV-immune cell co-incubation. In addition, PRO reverted PD-L1 upregulation and significantly decreased IL-10 levels in an immune-cancer cell co-culture. Chronic behavioural stress increased metastasis in mice while PRO monotherapy and the combo of PRO and PD-(L)1 inhibitor significantly decreased stress-induced metastasis. The combined therapy also reduced tumour weight compared to the cancer control group and induced anti-tumour T-cell responses with significant CD8 expression in tumour tissues. In conclusion, PRO showed a modulation of the cancer immune response by decreasing IFN-γ production and, in turn, IFN-γ-mediated PD-L1 overexpression. The combined therapy of PRO and PD-(L)1 inhibitor decreased metastasis and improved anti-tumour immunity offering a promising new therapy.

ERK1/2 mitogen-activated protein kinase mediates downregulation of intestinal tight junction proteins in heat stress-induced IBD model in pig

In many mammalian species, including pigs, heat stress (HS) detrimentally leads to epithelium damage and increases intestinal permeability. However, the underlying molecular mechanisms are not thoroughly investigated yet. This study aimed to examine the RIP1/RIP3-ERK1/2 signaling pathway that regulates the expression of tight junction proteins in HS-treated pigs. In in vitro cultured intestinal porcine epithelial cells (IPEC-J2), HS induced the expression of tight junction proteins, ZO-1, claudin-1, and claudin-4, that are regulated by the ERK1/2-MAPK signaling pathway. Further, high expression of HSP70 in IPEC-J2 cells induced a significant decrease in receptor-interacting protein 1/3 (RIP1/3), phosphorylated ERK, and tight junction protein claudin-1 (P < 0.05). Necrostatin-1 (A selective inhibitor of RIPK1) suppressed the upregulation of phosphorylated ERK1/2 induced by HS, indicating that the RIP1/RIP3 regulates ERK1/2 phosphorylation in IPEC-J2 under heat stress. In addition, HS significantly damaged the intestinal morphology characterized by reduction of villus length and crypt depth in in vivo porcine model. Moreover, the expression of tight junction, ZO-1, and claudin-4 were downregulated, whereas phosphorylated p38 and ERK1/2 were upregulated in the duodenum of heat-stressed pigs. Interestingly, a decrease in ZO-1 and claudin-1 was observed in the colon, where phosphorylated ERK1/2 was similar to that in the duodenum. Our results demonstrate that RIP1/RIP3-ERK1/2 signaling pathway regulates the expression of tight junction proteins in HS-pigs. This finding further advances the intestinal barrier function's underlying mechanisms associated with signaling regulation.

Appeasing Pheromones against Bovine Respiratory Complex and Modulation of Immune Transcript Expressions

Bovine respiratory disease is still a major concern and has major economic impact. Another consequence of respiratory infections is the use of antimicrobial molecules to control bacterial pathogens. This can participate in the emergence and shedding of antimicrobial resistance that can threaten animal as well as human health. Appeasing pheromones with their capacity to reduce stress and thus their ability to preserve the functions of the immune system have been proposed to reduce the use of antimicrobial substances. In this study, we assessed the effect of appeasing pheromone administration on bovine health and performance during the fattening period. Zootechnical and health parameters and whole blood immune transcript expressions were measured over four weeks in bulls to determine the effect of the pheromone. We observed increased clinical signs on Day 8 (D8) and decreased clinical signs on D30 in bulls who received the pheromone and a higher expression of interleukin 8 transcripts in this group than in the control group on D8. Our results are overall in line with previous reports in livestock species. Further studies are needed to shed more light on the effect of appeasing pheromones and decipher their exact mechanisms of action.

Stress-Induced Microglia Activation and Monocyte Trafficking to the Brain Underlie the Development of Anxiety and Depression

Psychosocial stress is capable of causing immune dysregulation and increased neuroinflammatory signaling by repeated activation of the neuroendocrine and autonomic systems that may contribute to the development of anxiety and depression. The stress model of repeated social defeat (RSD) recapitulates many of the stress-driven alterations in the neuroimmune system seen in humans experiencing repeated forms of stress and associated affective disorders. For example, RSD-induced neuronal and microglia activation corresponds with sympathetic outflow to the peripheral immune system and increased ability of bone marrow derived myeloid progenitor cells (MPC) to redistribute throughout the body, including to the central nervous system (CNS), reinforcing stress-associated behaviors. An overview of the neuroendocrine, immunological, and behavioral stress-induced responses will be reviewed in this chapter using RSD to illustrate the mechanisms leading to stress-related alterations in inflammation in both the periphery and CNS, and stress-related changes in behavioral responses.

Differential Susceptibilities of Human Lung Primary Cells to H1N1 Influenza Viruses

Human alveolar epithelial cells (AECs) and alveolar macrophages (AMs) are the first lines of lung defense. Here, we report that AECs are the direct targets for H1N1 viruses that have circulated since the 2009 pandemic (H1N1pdm09). AMs are less susceptible to H1N1pdm09 virus, but they produce significantly more inflammatory cytokines than AECs from the same donor. AECs form an intact epithelial barrier that is destroyed by H1N1pdm09 infection. However, there is significant variation in the cellular permissiveness to H1N1pdm09 infection among different donors. AECs from obese donors appear to be more susceptible to H1N1pdm09 infection, whereas gender, smoking history, and age do not appear to affect AEC susceptibility. There is also a difference in response to different strains of H1N1pdm09 viruses. Compared to A/California04/09 (CA04), A/New York/1682/09 (NY1682) is more infectious and causes more epithelial barrier injury, although it stimulates less cytokine production. We further determined that a single amino acid residue substitution in NY1682 hemagglutinin is responsible for the difference in infectivity. In conclusion, this is the first study of host susceptibility of human lung primary cells and the integrity of the alveolar epithelial barrier to influenza. Further elucidation of the mechanism of increased susceptibility of AECs from obese subjects may facilitate the development of novel protection strategies against influenza virus infection.

IMPORTANCE

Disease susceptibility of influenza is determined by host and viral factors. Human alveolar epithelial cells (AECs) form the key line of lung defenses against pathogens. Using primary AECs from different donors, we provided cellular level evidence that obesity might be a risk factor for increased susceptibility to influenza. We also compared the infections of two closely related 2009 pandemic H1N1 strains in AECs from the same donor and identified a key viral factor that affected host susceptibility, the dominance of which may be correlated with disease epidemiology. In addition, primary human AECs can serve as a convenient and powerful model to investigate the mechanism of influenza-induced lung injury and determine the effect of genetic and epigenetic factors on host susceptibility to pandemic influenza virus infection.

Heat stress upregulation of Toll-like receptors 2/4 and acute inflammatory cytokines in peripheral blood mononuclear cell (PBMC) of Bama miniature pigs: an in vivo and in vitro study

Global warming is a challenge to animal health, because of increased heat stress, with subsequent induction of immunosuppression and increased susceptibility to disease. Toll-like receptors (TLR) are pattern recognition receptors that act as sentinels of pathogen invasion and tissue damage. Ligation of TLRs results in a signaling cascade and production of inflammatory cytokines, which eradicate pathogens and maintain the health of the host. We hypothesized that the TLR signaling pathway plays a role in immunosuppression in heat-stressed pigs. We explored the changes in the expression of TLR2, TLR4 and the concentration of acute inflammatory cytokines, such as IL-2, IL-8, IL-12 and IFN-γ in Bama miniature pigs subjected to 21 consecutive days of heat stress, both in vitro and in vivo models. The results showed that heat stress induced the upregulation of cortisol in the plasma of pigs (P<0.05); TLR4 mRNA was elevated, but IL-2 was reduced in peripheral blood mononuclear cells (PBMC, P<0.05). The white blood cell count and the percentage of granulocytes (eosinophilic+basophilic) decreased significantly in heat-stressed pigs (P<0.05). In the in vitro model (PBMC heat shocked for 1 h followed by a 9 h recovery period), TLR2 and TLR4 mRNA expression also increased, as did the concentration of IL-12 in supernatants. However, IFN-γ was significantly reduced in PBMC culture supernatants (P<0.05). We concluded that a consecutive heat stress period elevated the expression of TLR2 and TLR4 in PBMC and increased the plasma levels of inflammatory cytokines. These data indicate that TLR activation and dysregulation of cytokine expression in response to prolonged heat stress may be associated with immunosuppression and increased susceptibility to antigenic challenge in Bama miniature pigs.

Stress significantly increases mortality following a secondary bacterial respiratory infection

A variety of mechanisms contribute to the viral-bacterial synergy which results in fatal secondary bacterial respiratory infections. Epidemiological investigations have implicated physical and psychological stressors as factors contributing to the incidence and severity of respiratory infections and psychological stress alters host responses to experimental viral respiratory infections. The effect of stress on secondary bacterial respiratory infections has not, however, been investigated. A natural model of secondary bacterial respiratory infection in naive calves was used to determine if weaning and maternal separation (WMS) significantly altered mortality when compared to calves pre-adapted (PA) to this psychological stressor. Following weaning, calves were challenged with Mannheimia haemolytica four days after a primary bovine herpesvirus-1 (BHV-1) respiratory infection. Mortality doubled in WMS calves when compared to calves pre-adapted to weaning for two weeks prior to the viral respiratory infection. Similar results were observed in two independent experiments and fatal viral-bacterial synergy did not extend beyond the time of viral shedding. Virus shedding did not differ significantly between treatment groups but innate immune responses during viral infection, including IFN-γ secretion, the acute-phase inflammatory response, CD14 expression, and LPS-induced TNFα production, were significantly greater in WMS versus PA calves. These observations demonstrate that weaning and maternal separation at the time of a primary BHV-1 respiratory infection increased innate immune responses that correlated significantly with mortality following a secondary bacterial respiratory infection.

Stress and the anti-influenza immune response: repeated social defeat augments clonal expansion of CD8(+)T cells during primary influenza A viral infection

Social disruption stress (SDR) prior to primary influenza A virus (IAV) infection augments memory to IAV re-challenge in a T cell-specific manner. However, the effect of SDR on the primary anti-viral immune response has not been elucidated. In this study, SDR-infected (INF) mice terminated viral gene expression earlier and mounted an enhanced pulmonary IAV-specific CD8(+)T cell response versus controls. Additionally, SDR-INF mice had a more pro-inflammatory lung profile prior to and during infection and an attenuated corticosterone response. These data demonstrate neuroendocrine modification of the lung microenvironment and increased antigen-specific T cell activation, clonal expansion and viral control in stress-exposed mice.

Selection of reference genes for gene expression studies in PBMC from Bama miniature pig under heat stress

Heat stress decreases immune function and increases disease susceptibility in stressed animals, which are important factors for industry and public health. We investigated the molecular mechanisms underlying heat stress by profiling the expression of target genes involved in the cellular response in the blood of Bama miniature pigs (Sus scrofa domestica) over 21 days with the use of quantitative RT-PCR (qRT-PCR). Reliable standards were established for the normalization of qRT-PCR. Six potential reference genes were ranked by their stability using the geNorm and NormFinder programs. Ribosomal protein L4 (RPL4) and TATA-box-binding protein (TBP) ranked as the two most stably expressed genes, except on day 21 when beta-2-microglobulin (B2M) was the most stable. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and ribosomal RNA 18S (18SRNA) were discarded as reference genes due to their unstable expression patterns. When B2M and TBP genes were selected as standards in combination, rather than GAPDH, a significant upregulation in Toll-like receptor 2 (TLR2) expression was observed after 21 consecutive days of heat stress. These findings suggest that selection of an ideal reference gene is a key step in comparison of transcription profiles in Bama miniature pigs.

Stressor-induced alterations of adaptive immunity to vaccination and viral pathogens

The stress response influences the immune system, and studies in laboratory animals indicate that the response to stress significantly reduces resistance to infectious challenge. Only a few studies, however, have determined the impact of the stress response on human susceptibility to infectious challenge due, in part, to the difficulties of using live, replicating pathogens in human research. As a result, many studies have assessed the immune response to vaccination as a surrogate for the immune response to an infectious challenge. Thus, much is known about how the stress response influences adaptive immunity, and memory responses, to vaccination. These studies have yielded data concerning the interactions of the nervous and immune systems and have provided important information for clinicians administering vaccines to susceptible populations. This review provides a brief overview of the immune response to commonly used vaccines and the impact that stress can have on vaccine-specific immunity.

Variations in the hemagglutinin of the 2009 H1N1 pandemic virus: potential for strains with altered virulence phenotype?

A novel, swine-origin influenza H1N1 virus (H1N1pdm) caused the first pandemic of the 21st century. This pandemic, although efficient in transmission, is mild in virulence. This atypical mild pandemic season has raised concerns regarding the potential of this virus to acquire additional virulence markers either through further adaptation or possibly by immune pressure in the human host. Using the mouse model we generated, within a single round of infection with A/California/04/09/H1N1 (Ca/04), a virus lethal in mice--herein referred to as mouse-adapted Ca/04 (ma-Ca/04). Five amino acid substitutions were found in the genome of ma-Ca/04: 3 in HA (D131E, S186P and A198E), 1 in PA (E298K) and 1 in NP (D101G). Reverse genetics analyses of these mutations indicate that all five mutations from ma-Ca/04 contributed to the lethal phenotype; however, the D131E and S186P mutations--which are also found in the 1918 and seasonal H1N1 viruses-in HA alone were sufficient to confer virulence of Ca/04 in mice. HI assays against H1N1pdm demonstrate that the D131E and S186P mutations caused minor antigenic changes and, likely, affected receptor binding. The rapid selection of ma-Ca/04 in mice suggests that a virus containing this constellation of amino acids might have already been present in Ca/04, likely as minor quasispecies.

Effect of stress on viral-bacterial synergy in bovine respiratory disease: novel mechanisms to regulate inflammation

The severity of bovine respiratory infections has been linked to a variety of factors, including environmental and nutritional changes, transportation, and social reorganization of weaned calves. Fatal respiratory infections, however, usually occur when a primary viral infection compromises host defences and enhances the severity of a secondary bacterial infection. This viral–bacterial synergy can occur by a number of different mechanisms and disease challenge models have been developed to analyse host responses during these respiratory infections. A primary bovine herpesvirus-1 (BHV-1) respiratory infection followed by a secondary challenge with Mannheimia haemolytica results in fatal bovine respiratory disease (BRD) and host responses to these two pathogens have been studied extensively. We used this disease model to demonstrate that stress significantly altered the viral–bacterial synergy resulting in fatal BRD. Functional genomic analysis revealed that BHV-1 infection enhanced toll-like receptors (TLR) expression and increased pro-inflammatory responses which contribute to the severity of a Mannheimia haemolytica infection. TLRs play a critical role in detecting bacterial infections and inducing pro-inflammatory responses. It is difficult to understand, however, how stress-induced corticosteroids could enhance this form of viral–bacterial synergy. Nuclear translocation of the glucocorticoid receptor activates cell signalling pathways which inhibit both TLR signalling and pro-inflammatory responses. The apparent conundrum between stress-induced corticosteroids and enhanced BRD susceptibility is discussed in terms of present data and previous investigations of stress and respiratory disease.

Impact of nose-only exposure system on pulmonary gene expression

Nose-only exposure is used to study the distribution and toxicity of airborne contaminants. Restraint of animals in nose-only tubes causes stress, but the impact on pulmonary mRNA levels is unknown. Since stress and xenobiotics activate common pathways, we assessed whether nose-only exposure would alter expression of toxicologically relevant genes in the lungs. To identify candidate genes for further analysis, we first interrogated microarray data to examine time-dependent changes in gene expression in air-control animals from a nose-only inhalation study involving male wild-type C57BL/6 mice and transgenic tumor necrosis factor (TNF)-alpha over-expressing littermates. Comparison of transcript levels immediately and 24 h after a single 4-h nose-only exposure to air revealed differential expression of 280 genes (false discovery rate-adjusted, p < .05). Functional analysis revealed enrichment of immune response, apoptosis, and signalling terms, consistent with effects of restraint stress. We then selected a subset of target genes for comparison of naive animals and air-exposed animals from the inhalation study by real-time polymerase chain reaction (PCR). Expression of genes involved in stress (BNIP, sestrin-1, CDKN1A [p21], GADD45 gamma), glucocorticoid-response (GILZ, Sgk), and signal transduction (MAP3K6, C/EBP-delta) was increased as a result of nose-only exposure (p < .05). In contrast, proinflammatory factors (lymphotoxin-beta, chemokine receptor CXCR5) were decreased (p < .05). Immune gene responses observed in wild-type animals were reduced in animals with lung inflammation, indicating that pathological states can modify the response to nose-only exposure. Observed responses may warrant consideration in the evaluation of materials delivered by nose-only inhalation, and suggest that incorporation of naive animals into nose-only studies should be considered as a best practice.

Cutting edge: Sympathetic nervous system increases proinflammatory cytokines and exacerbates influenza A virus pathogenesis

Although the sympathetic nervous system innervates the lung, little is known about its participation in host immunity to pulmonary pathogens. In this study, we show that peripheral sympathectomy reduces mouse morbidity and mortality from influenza A virus-induced pneumonia due to reduced inflammatory influx of monocytes, neutrophils, and NK cells. Mortality was also delayed by treating mice with an alpha-adrenergic antagonist. Sympathectomy diminished the immediate innate cytokine responses, particularly IL-1, which was profoundly reduced. These findings demonstrate an unexpected role for the sympathetic nervous system in innate antiviral immunity and in exacerbating the pathology of a virus of great significance to human and animal health.

Modern approaches to understanding stress and disease susceptibility: A review with special emphasis on respiratory disease

Studies in animals and humans link both physical and psychological stress with an increased incidence and severity of respiratory infections. For this manuscript we define stress as the physiological responses an individual undergoes while adjusting to a continually changing environment. It is known that stressors of various types (psychological/physical) can alter the physiological levels of certain hormones, chemokines and cytokines. These alterations send information to the central nervous system to take necessary action which then sends messages to appropriate organs/tissues/cells to respond. These messages can either activate or suppress the immune system as needed and failure to compensate for this by the body can lead to serious health-related problems. Little is known how stress affects disease susceptibility, yet understanding this mechanism is important for developing effective treatments, and for improving health and food quality. The current review focuses on (a) the effects of psychological stressors in humans and animals, (b) various methodologies employed to understand stress responses and their outcomes, and (c) the current status of the attempts to correlate stress and disease with respiratory disease as model system. The methodologies included in this review span traditional epidemiological, behavioral and immunological studies to current high throughput genomic, proteomic, metabolomic/metabonomic approaches. With the advent of various newer omics and bioinformatics methodologies we postulate that it will become feasible to understand the mechanisms through which stress can influence disease onset. Although the literature in this area is limited because of the infancy of this research area, the objective of this review is to illustrate the power of new approaches to address complex biological questions. These new approaches will also aid in our understanding how these processes are related to the dynamics and kinetics of changes in expression of multiple genes at various levels.

Impacts of chronic stress and social status on various physiological and performance measures in pigs of different breeds

Pigs typically experience various environmental stressors, which can negatively affect performance. Cortisol concentrations and various immune and performance measures are influenced by breed, but few data exist describing the impact of breed on stress responsiveness in pigs. The objective of this experiment was to determine if certain physiological responses to chronic stressors differed among 3 breeds and 2 commercial lines of pigs. The pigs were Landrace (n = 36), Meishan (n = 30), Yorkshire (n = 32), or 1 of 2 commercial lines (Line-A and Line-B; both n = 36). All pigs were weaned at 17 to 21 d and kept in a common nursery. At 49 d of age, pigs were assigned to 1 of 2 treatments: stress (heat, crowding, and mixing) or control (no stress treatment). Pigs were allocated to groups of 3 pigs per pen of the same sex. Control pigs were kept with their littermates. At the onset of the experiment, stressed pigs were mixed with 2 unfamiliar pigs once, and heat and crowding stressors were implemented simultaneously for 14 d. Pigs allocated to the stress treatment were video-recorded for 24 h following initiation of mixing to determine social status: dominant, intermediate, or submissive. Blood samples were taken at d 0 (baseline), 1, 7, and 14 to assess cortisol concentrations and immune measures. Breed and treatment affected cortisol, immune, and performance measures, but no significant breed x treatment interactions were found. In general, pigs subjected to the chronic stressor had lower (P < 0.001) BW and ADG (P < 0.001) than did control pigs. Plasma cortisol was lower (P < 0.001) among stressed pigs at d 7 and 14. Regardless of breed, lipopolysaccharide-induced proliferation (P < 0.01) and natural killer (NK; P < 0.005) cytotoxicity were greater in stressed pigs compared with controls. Furthermore, among stressed pigs, dominant pigs had a greater total white blood cell count (P < 0.005), NK (P < 0.05), and phagocytosis (P < 0.05) than the subordinate pigs. The results indicate that pig breed did not influence the physiological responses to the chronic concurrent stressors imposed for 14 d in this study, but social status did influence the immune responsiveness of these pigs to heat, crowding, and mixing.

Stress induces the translocation of cutaneous and gastrointestinal microflora to secondary lymphoid organs of C57BL/6 mice

Mammals are colonized by a vast array of bacteria that reside as part of the host's microflora. Despite their enormous levels, these microorganisms tend to be restricted to cutaneous and mucosal surfaces. In the current experiment, only a small percentage of non-stressed mice exhibited detectable levels of bacteria in their inguinal lymph nodes (ILN), spleen, liver, or mesenteric lymph nodes (MLN). However, after experiencing repeated social disruption (SDR), a significant increase in the number of animals having bacteria in their ILN and MLN was found. Since SDR involves fighting in which bite wounds on the skin could provide a portal of entry into the host, it was determined whether experimental wounding (full-thickness skin biopsy), chronic restraint (which is a potent stressor that does not disrupt the skin barrier), or wounding combined with restraint would increase the occurrence of bacteria in secondary lymphoid tissues and liver. Wounding did not significantly increase the prevalence of bacteria in the ILN, MLN, or liver. Interestingly, a larger percentage of restrained and restrained plus wounded mice, in comparison to controls, had bacteria in the ILN, MLN, and liver. Although the stressors increased the number of animals that became colonized, the levels of bacteria in the stressed mice were similar to the levels found in the few non-stressed mice that did become colonized. Our results indicate that psychological components of social stress facilitate the translocation of indigenous bacteria into the host, thus identifying an additional facet through which stressors may impact health.

Restraint stress alters lung gene expression in an experimental influenza A viral infection

In the present study the global effect of restraint stress on gene expression in the murine lung during an experimental influenza A/PR8 viral infection was examined. Gene expression profiling using high density oligonucleotide microarrays revealed that the expression of 95 genes was altered on day 3 post infection (p.i.), while 48 genes were altered on day 7 p.i. Restraint stress reduced and delayed the expression of specific cytokines, cell adhesion molecules and cell surface receptors indicating alterations in cell migration to the site of infection. Furthermore, mapping of the candidate genes to known pathways revealed that genes associated with host defense and immune responses, including chemotaxis and chemokine function, antigen presentation and processing, MHC class II receptor function and inflammation were the major pathways affected by restraint stress.

Stress-induced modulation of NK activity during influenza viral infection: role of glucocorticoids and opioids

Activation of the hypothalamic-pituitary-adrenal axis (HPA) and sympathetic nervous system by stress has been shown to modulate both innate and adaptive immunity during an experimental influenza A/PR8 viral infection. HPA activation alters levels of glucocorticoids (GC) and opioids which are associated with suppression of lymphoid cellularity and NK activity. These experiments were designed to investigate the role that stress-induced GC and opioids have in modulating NK activity during an influenza viral infection. C57BL/6 mice were treated daily with mifepristone (RU486), a GC receptor antagonist or naltrexone (NTX), a non-specific opioid receptor antagonist. Mice were infected intranasally with A/PR8 virus and underwent daily restraint stress (RST). Phenotypic analysis of splenic cell populations and NK cytotoxicity were assessed at 3 days post-infection. RST of infected mice significantly suppressed splenic CD3(-)DX5+ cellularity and NK cytolytic activity. RU486 administration fully restored splenic NK cellularity but not cytolytic activity. NTX administration restored NK cytolytic activity but not splenic NK cell number. A similar restoration in NK cytolytic activity was observed after administration of beta-funaltrexamine (FNA), a mu-specific opioid receptor antagonist, but not the delta- or kappa-specific opioid receptor antagonists naltrindole or nor-binaltorphimine, respectively. Co-administration of RU486 and NTX restored both NK cellularity and cytolytic activity. The restoration of RST-induced suppression of NK activity by RU486 and NTX or FNA suggests that glucocorticoids modulate NK cellularity and opioids that bind to the mu-opioid receptor modulate NK cytotoxicity during periods of stress and viral infection.

Alterations in chemokine expression following Theiler's virus infection and restraint stress

Restraint stress (RS) applied to mice during acute infection with Theiler's virus causes corticosterone-induced immunosuppression. This effect was further investigated by measuring chemokine changes in the spleen and central nervous system (CNS) using an RNase Protection Assay. mRNAs for lymphotactin (Ltn), interferon-induced protein-10 (IP-10), MIP-1 beta, monocyte chemoattractant protein-1 (MCP-1) and TCA-3 were detected in the spleen at day 2 pi, but not in the brain of CBA mice infected with Theiler's virus. Ltn, IP-10 and RANTES were elevated in both the spleen and the brain at day 7 pi, and were significantly decreased by RS in the brain. RS also resulted in decreased inflammation within the CNS.

Workshop report: The effects of psychological variables on the progression of HIV-1 disease

The reciprocal interactions between the neuroendocrine, immune, and autonomic nervous systems are complicated, yet worthy of examination. A body of literature suggests that psychological factors such as stress, or psychiatric conditions such as major depression, may influence the immune system thereby altering host susceptibility to viral, or other types of infection. Alternately, in an attempt to limit infection and replication, the anti-viral host response, via innate and acquired immunity and subsequent release of pro-inflammatory cytokines and additional anti-viral mediators, may affect mood, cognition emotion, and possibly precipitate a psychiatric disorder. In order to address what is known regarding neuroendocrine-immune interactions in the context of HIV infection, the Center for Mental Health Research on AIDS convened a panel of scientists from diverse areas of expertise. Their primary charge was to examine whether stress-induced activation of the neuroendocrine system affects the immune system in a manner that negatively influences HIV disease progression, and whether HIV infection influences the central nervous system and behavior. The ensuing report summarizes their deliberations as they discussed the current body of information and identified outstanding critical questions in the areas of research. The group consensus was that the biological mediators of psychological status can play an important role in mediating HIV disease progression, particularly in subgroups of vulnerable patients; furthermore, they identified candidate biological mediators and mechanisms of disease progression. The Workgroup outlined the inherent challenges and limitations of such research and provided recommendations as to the future directions of research utilizing human, animal, and in vitro models of HIV-1 infection and stress.

Immune alterations induced by social defeat do not alter the course of an on-going BCG infection in mice

The timing for applying stressor and primary immunization is known to influence the nature of the immune alterations induced by stress. The aim of the present study was to investigate the consequences of a stress occurring several days after the beginning of a primary infection on the host resistance. For this purpose, we investigated the effects of repeated social defeat on the immune response of mice infected with BCG 11 days before. In vitro production of cytokines in response to LPS or tuberculin, and the sensitivity of spleen cells to corticosterone were assessed 8 days after the end of the stress. Bacterial growth was assessed in the spleen. We demonstrated that social defeat in BCG-infected mice induced a long-term increase in IL-6 and IL-10 production in response to LPS but did not modify the sensitivity of spleen cells to corticosterone. Stress did not affect the specific response to BCG, as shown by the production of cytokines in tuberculin-stimulated cultures. Accordingly, social defeat was unable to influence the mycobacterial growth in vivo. These results support the hypothesis postulating that stress does not affect antigen-specific response when it is applied after priming.

Suppression of host resistance to Listeria monocytogenes by acute cold/restraint stress: lack of direct IL-6 involvement

We conducted kinetic studies to evaluate the effects of acute cold/restraint stress (ACRS) on both primary and secondary host resistance to Listeria monocytogenes (LM). The involvement of IL-6 also was investigated using IL-6 knockout (KO) mice on the BALB/c background. ACRS dramatically increased the serum corticosterone levels, indicating that ACRS activated the hypothalamic-pituitary-adrenal (HPA) axis. ACRS significantly inhibited host resistance to LM during a primary but not a secondary LM infection. During the primary infection, ACRS caused a significant delay in clearance of LM, loss of body weight, reduced food/water intake, and elevated levels of pro-inflammatory cytokines (IL-6, IL-1beta, and TNFalpha) and IFNgamma. ACRS IL-6 KO mice showed higher LM burdens than did IL-6 KO controls, suggesting that IL-6 is not required for the ACRS-impairment of host resistance. Elevated levels of IL-1beta and TNFalpha may compensate for the absence of IL-6 and maintain the ACRS-induced impairment, in that the serum and splenic IL-1beta and TNFalpha levels were significantly higher in infected ACRS IL-6 KO mice, but not in control IL-6 KO mice, as compared to respective wild type controls. ACRS appears to inhibit IL-6 independent mechanisms associated with innate immunity and/or the development of adaptive immunity, but these reactions are unable to modulate the more efficient secondary immune responses.

Stress and influenza viral infection: modulation of proinflammatory cytokine responses in the lung

Viral infection of the respiratory tract induces a complex series of cellular and molecular events leading to immunological responses designed to terminate viral replication. Anti-viral immunity involves natural resistance mechanisms that overlap and modulate the development of the subsequent adaptive immune responses. An experimental murine infection with influenza A/PR8 virus was used to examine the effects of stress-induced activation of the nervous and endocrine systems on components of innate immunity. Proinflammatory cytokine responses (IL-1alpha, IL-6 and TNFalpha) were measured in the lungs during an influenza A/PR8 viral infection. For activation of the nervous and endocrine systems, restraint stress (RST) was applied prior to and during infection. Following infection, IL-1alpha increased transiently, while elevated IL-6 persisted; TNFalpha was not detected. RST suppressed virally-induced IL-1alpha, while IL-6 was unaffected. These data demonstrate differential regulation of proinflammatory cytokines by stress. The mechanism underlying suppression of the lung IL-1alpha in stressed mice is currently unknown; its downregulation may contribute to increased viral pathogenesis in stressed individuals.

Steroid hormone regulation of antiviral immunity

Recent observations in both humans and animals have demonstrated that stress is immunomodulatory and can alter the pathogenesis of microbial infections to the extent that it may be adverse to health. Stress disrupts homeostasis, and the body responds through endocrine and nervous system interactions in an effort to re-establish the health of the host. However, the resulting physiologic changes associated with stress, such as the rise in serum glucocorticoids (GCs), are implicated in suppression of antiviral immunity. Therefore, it would be of significance to counterregulate stress-mediated immunosuppression during viral infection to improve immune responses and limit virus-mediated damage. The data in this study focus upon the antiglucocorticoid influence of a native steroid hormone that has been shown to augment immune function and protect animals against lethal viral infections. Androstenediol (5-androstene-3 beta,17 beta-diol, AED), a metabolite of dehydroepiandrosterone (DHEA), confers protection against lethal infection with influenza A virus. The protective activity appears to counterbalance the function of the regulatory GCs because AED prevents GC-mediated suppression of IL-1, TNF-alpha, and IL-2 secretion. Furthermore, AED inhibits GC-induced transcription of a GC-sensitive reporter gene.

Social disruption, immunity, and susceptibility to viral infection. Role of glucocorticoid insensitivity and NGF

Glucocorticoid (cort) responses have been shown to suppress inflammatory reactions by inhibiting the trafficking of immune cells. Recently, it was demonstrated that restraint stress (RST) and psychosocial stress (social reorganization; SRO) differentially affected the pathophysiology and survival in the mouse influenza viral infection model. While both stressors activated the HPA axis, only SRO affected survival. In RST, elevated cort diminished recruitment of inflammatory cells following intranasal challenge of C57BL/6 mice with A/PR8 virus. However, infected SRO mice developed hypercellularity in the lungs and were more likely to die from lung consolidation than controls. Since elevated cort failed to be anti-inflammatory in SRO mice, the hypothesis that psychosocial stress induced steroid insensitivity was tested. An in vitro cort suppression test was performed by stimulating splenocytes from SRO and control mice with mitogen in the presence or absence of cort. Proliferation of ConA-stimulated cells was inhibited by cort in a dose-dependent fashion in controls, but splenocytes from SRO mice stimulated with ConA were resistant to cort-induced suppression. Thus, psychosocial stress induced a state of steroid insensitivity. SRO also induced the release of nerve growth factor (NGF) from the salivary glands into circulation; plasma NGF correlated with development of steroid insensitivity. NGF has been reported to negatively regulate the expression of type II glucocorticoid receptors, and thus may be a key factor in the induction of steroid insensitivity.

Evaluating mutant mice: anatomic pathology

As the human and mouse genome projects approach their goals, initiatives in functional genomics are advancing. When the nucleotide sequences are available, identification of gene functions will assume even greater importance. Determination of gene products and their proximal biochemical functions provide a part of the picture, but determination of their functions in the context of the whole organism is the ultimate goal. The manipulated mouse genome has become accepted as a model for understanding the genetic basis of human conditions and diseases. Consequently, biomedical research institutions have seen significant increases in the use of mice since the early 1980s, and these increases are largely attributable to the use of genetically modified mice. The role of comparative pathology in research on mutant mouse models of disease is increasing in response to these trends. Evaluation and phenotypic characterization of mutant mice, via clinical and anatomic pathology techniques, will be an important component of functional genomics initiatives.

Impaired activity of phagocytic cells in Candida albicans infection after exposure to chronic varied stress

OBJECTIVE

Candidiasis is a prototypic opportunistic fungal disease that may follow severe modulations of the immune system of the host. The purpose of this study was to evaluate which innate immune mechanisms involved in the protection against fungal invasion are impaired under stress conditions.

METHODS

Wistar rats were infected intraperitoneally with Candida albicans and immediately exposed to chronic varied stress (CVS) over 10 days (CVS; Ca-S); the fungal burden (CFU), histopathological lesion and ACTH levels were evaluated. Additionally, functional assessment of peritoneal cells (PC) included the phagocytic and anticandidacidal activities and the production of H(2)O(2) and NO.

RESULTS

In the only infected animals (Ca), C. albicans colonization stimulated an efficient inflammatory response, while in Ca-S rats poor tissue reactions were associated with increased CFU in livers and kidneys (p < 0.05, Ca vs. Ca-S). Whereas the phagocytic process was not modified, the candidacidal activity of PC was significantly decreased after the application of CVS (p < 0.001, Ca vs. Ca-S). The H(2)O(2) production by macrophages and neutrophils was downregulated by the infection, and while at early intervals these cells possessed a residual oxidative capacity, by day 10, the production of this metabolite was blocked. Spontaneous NO production by macrophages was significantly increased in both Ca and Ca-S animals (p < 0.001), but in stressed rats, this reactive nitrogen intermediate was noticeably downregulated (p < 0.05, Ca vs. Ca-S). The hyperactivity of hypothalamus-pituitary-adrenal axis after exposure to stress was confirmed by an increase in baseline plasma ACTH levels.

CONCLUSION

These results show that during infection with C. albicans, the exposure to CVS contributes to the spread of the fungus and downregulates critical functions of phagocytic cells involved in the control of this opportunistic pathogen.

Plasma corticosterone and immune reactivity in restrained female C3H mice

Psychological stressors are known to stimulate the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system resulting in the release of corticosterone and catecholamines respectively. They have also been reported to induce cytokine production. All these molecules affect various immune parameters and can alter overall immune competence of the individual. The purpose of this investigation was to study the regulation of the production of corticosterone during stress and its possible effects on immune reactivity. In a first series of experiments, the possible regulation of corticosterone production by interleukin (IL)-1beta and peripheral catecholamines during restraint was assessed using a pharmacological approach in mice. Plasma IL-1beta concentrations remained at basal after 1-h restraint and the stress-induced increase of plasma corticosterone was not modified by a peripheral injection of an IL-1 receptor antagonist (IL-1ra). By contrast, chemical sympathectomy potentiated the restraint-induced increase in plasma corticosterone concentration, this potentiation being reversed by IL-1ra. In a second series of experiments, the role of corticosterone in stress-immune relationships was studied in adrenalectomized mice subjected to restraint and immunized with sheep erythrocytes. Non-specific immunity, i.e. proliferation of splenocytes and thymocytes and plasma levels of IL-1beta, as well as specific immunity, i.e. antibody production and delayed hypersensitivity, were not altered after 2-h restraint. Adrenalectomy failed to induce immune effects in stressed animals, except that delayed hypersensitivity was stronger in adrenalectomized animals, revealing that the high levels of corticosterone produced during stress have an anti-inflammatory activity. The present data show that the stress-induced production of corticosterone was modulated by both peripheral catecholamines and IL-1beta. However, this production of corticosterone was unable to modulate immune reactivity except delayed hypersensitivity.

Animal models of pulmonary infection in the compromised host: potential usefulness for studying health effects of inhaled particles

Pulmonary infection leading to pneumonia is a significant cause of morbidity and mortality worldwide. Airborne particles have been associated with pneumonia through epidemiological research, but the mechanisms by which particles affect the incidence of pneumonia are not well established. The purpose of this review is to examine the potential of animal models to improve our understanding of the mechanisms by which inhaled particles might affect the incidence and resolution of pulmonary infection. The pathogenesis of pneumonia in most animal models differs from that in humans because humans frequently have underlying diseases that predispose them to infection with relatively low doses of pathogens. Normal, healthy animals lack the underlying pathology often found in humans and clear bacteria and viruses rapidly from their lungs. To overcome this, animals are administered large inocula of pathogens, are treated with agents that cause mucosal lesions, or are treated with immunosuppressive drugs. Alternatively, pathogenic bacteria are protected from phagocytosis by encasing them in agar. No one animal model will replicate a human disease in its entirety, and the choice of model depends upon how well the animal infection mimics the particular human response being examined. The advantages and disadvantages of animal models in current use for bacterial and viral infections important in the etiology of human pneumonia are reviewed in detail. Considerable data indicate that prior exposure to particles compromises the ability of experimental animals to resolve a subsequent infection. In addition, information is available on the effects of particle exposure on various portions of respiratory defense including phagocytic function, ciliary movement, inflammation, and antibody response in the absence of infection. In contrast, little research to date has examined the consequences of particle exposure on the host defense mechanisms of animals already infected or on their ability to resolve their infection.

Mapping quantitative trait loci for stress induced alterations in porcine leukocyte numbers and functions

To identify quantitative trait loci (QTLs) with effects on 'stress' induced alterations of porcine immune functions, a number of immune capacity traits were analysed in the F2 generation of a Wild Boar--Yorkshire intercross. All traits were measured prior, and one day after, exposure to experimental 'stress' (mixing and transport). The 'stress' protocol induced a decrease in numbers of circulating neutrophils and in spontaneous proliferation in vitro, whereas phagocytic capacity, mitogen induced proliferation and spontaneous IL-2 activity increased. The IFN-alpha production tended to decrease, although the individual variation was pronounced. More than 200 genetic markers have been scored in the entire pedigree and were used to trace the inheritance of individual chromosome segments. Wild Boar alleles were on average associated with higher mitogen induced IL-2 activity and a slightly lower decrease in IFN-alpha production after mixing and transport. Four QTLs with significant effects were identified; one influencing 'stress' induced alteration in numbers of neutrophils (chromosome 8), one influencing spontaneous proliferation after 'stress' (chromosome 2), one influencing mitogen induced IL-2 activity after 'stress' (chromosome 6) and one influencing 'stress' induced alterations in mitogen induced IL-2 activity (chromosome 12). In addition, several suggestive QTLs were indicated.

Influence of psychosocial, psychogenic and neurogenic stressors on several aspects of immune functioning in mice

Analysis of stressor effects on immune functioning is complicated by the fact that the nature of the changes observed may be influenced by organismic factors (e.g., species, strain, age), the nature, severity and chronicity of the stressor, as well as the specific immune parameters being examined. It is demonstrated in the present investigation that in the highly reactive inbred BALB/cByJ mouse, the relatively hardy C57BL/6ByJ strain, as well as in the noninbred CD-1 strain, acute psychogenic (predator exposure) and neurogenic (footshock) stressors reduced splenic macrophage activity, and this effect was less marked after a chronic stressor. With protracted, but not transient, psychosocial disturbances (isolated housing) similar effects were seen, suggesting that the effect was not simply due to a change of the social mileau. The psychogenic and neurogenic stressors also enhanced LPS-stimulated lymphocyte proliferation in CD-1, but not in the inbred strains. However, isolated housing reduced both B and T cell proliferation, indicating that social isolation likely affects processes distinct from those of other stressors. Interestingly, when the aversiveness of the psychogenic stressor was increased (by decreasing the distance between the rat and the mouse) LPS-stimulated lymphocyte proliferation was reduced in the reactive BALB/cByJ strain, but increased in the hardy C57BL/6ByJ mice. This stressor, however, enhanced T cell proliferation in both strains of mice. It is suggested that analysis of stressor effects need to consider in greater detail the characteristics of the organism being stressed, as well as the characteristics of the stressor itself.

Restraint stress-induced immunosuppression by inhibiting leukocyte migration and Th1 cytokine expression during the intraperitoneal infection of Listeria monocytogenes

In this study, a murine model of Listeria monocytogenes infection was used to investigate effects of restraint stress (RST) on host defense. We observed that the L. monocytogenes infection as well as RST induced an elevation of endogenous corticosterone (CORT) levels and RST synergistically enhanced endogenous CORT levels during the listerial infection. RST suppressed the migration of leukocytes including macrophages, neutrophils, NK cells and lymphocytes into the peritoneal cavities after the intraperitoneal inoculation of L. monocytogenes. RST also suppressed the increase of the surface MHC class II antigen expression in both peritoneal macrophages and B cells during the listerial infection. Interestingly, gene expression of iNOS, MCP-1 (JE) and Th1-type cytokines including IFN-gamma and IL-12 was down-regulated but Th2-type cytokine (IL-4 and IL-6) gene expression in the PEC was rather up-regulated on day 7 after infection, indicating that Th2-type immune response is more resistant to the elevated endogenous CORT levels than Th1-type response. Treatment of mice with RU486, a glucocorticoid receptor antagonist, restored the immune responses suppressed by RST to their normal levels in the infected mice, suggesting that the RST-induced elevation of endogenous corticosterone levels is mainly responsible for the induction of the immunosuppressive events during L. monocytogenes infection.

Metallothionein induction in response to restraint stress. Transcriptional control, adaptation to stress, and role of glucocorticoid

Metallothioneins (MT) have been implicated in the protection of cells from oxidative stress. We studied the molecular mechanism of induction of MT-I and MT-II in response to restraint stress using a mouse model system in which the animals were restrained in well ventilated polypropylene tubes for 12 h each day (one cycle). Here, we show that MT-I and MT-II mRNA levels were elevated as much as 10-20-fold after just one cycle of this simple stress. Stress-mediated MT induction occurred at the transcriptional level. The level of MT mRNA correlated with the stress-induced increase, and not with the diurnal variation, in the level of serum glucocorticoid. Treatment of the mice with RU 486, a glucocorticoid receptor antagonist, prior to restraint stress inhibited MT induction by at least 50%. Furthermore, the glucocorticoid responsive element-binding activity in the liver nuclear extracts from the stressed mice was significantly higher than that in the control mice. The complex formations between the transcription factor Sp1, MTF1, or MLTF/ARE and the respective specific oligonucleotides were not altered in the liver from the stressed mouse. The MT mRNA levels returned to the basal level at the end of nine cycles of stress, indicating habituation of the animals to restraint stress. At this stage, exposure of the animals to another type of stress, treatment with heavy metals, resulted in further induction of MT. These data indicate that glucocorticoid is the primary physiological factor responsible for MT induction following restraint stress, and the glucocorticoid receptor is the major transcription factor involved in this process.

Differential immune reactivity to stress in BALB/cByJ and C57BL/6J mice: in vivo dependence on macrophages

Inbred BALB/cByJ and C57BL/6J mice not only differ in their neuroendocrine and behavioral reactivity to stress, but also their ability to mount appropriate immune responses to various pathogens. Because evidence suggests that stress may bias humoral or cell-mediated immune responses in these mouse strains, we assessed the effects of acute (1 h) physical restraint on the humoral immune response to keyhole limpet hemocyanin (KLH). Restraint exposure in close proximity to immunization with KLH enhanced the number of primary antigen-specific IgM and IgG producing splenic B cells in BALB/cByJ mice, but not in C57BL/6J mice. These effects might be determined at the level of macrophage antigen presenting cells, because BALB/cByJ mice immunized with KLH as a particulate antigen (i.e., encapsulated in liposomes) displayed the same stressor enhanced antibody response as they did to free, unencapsulated KLH. In addition, these mice showed enhanced production of the IgG1 subtype of IgG, but not the IgG2a subtype. Conversely, stressed C57BL/6J mice revealed an enhanced IgG2a response, although this was observed only under conditions of immunization with liposome-encapsulated KLH. In a final experiment involving only the BALB/cByJ strain, the depletion of macrophages in the spleen by administration of liposomes containing dichloromethylene biphosphonate (DMDP) 2 days before immunizing the mice with free KLH and restraint exposure, blocked the restraint-induced enhancement of humoral immune responses. These data suggest a possible intermediary role for macrophages in stressor-induced immunomodulation in vivo, which may be a potential point of divergence that explains the differential immune reactivity to KLH of BALB/cByJ and C57BL/6J mice exposed to an acute stressor.

Social stress and the reactivation of latent herpes simplex virus type 1

Psychological stress is thought to contribute to reactivation of latent herpes simplex virus (HSV). Although several animal models have been developed in an effort to reproduce different pathogenic aspects of HSV keratitis or labialis, until now, no good animal model existed in which application of a psychological laboratory stressor results in reliable reactivation of the virus. Reported herein, disruption of the social hierarchy within colonies of mice increased aggression among cohorts, activated the hypothalamic-pituitary-adrenal axis, and caused reactivation of latent HSV type 1 in greater than 40% of latently infected animals. However, activation of the hypothalamic-pituitary-adrenal axis using restraint stress did not activate the latent virus. Thus, the use of social stress in mice provides a good model in which to investigate the neuroendocrine mechanisms that underlie behaviorally mediated reactivation of latent herpesviruses.

A genetic basis for neuroendocrine-immune interactions

Psychoneuroimmunology is an exciting, complex field that elucidates interactions among the nervous, endocrine, and immune systems. The contribution of psychosocial factors and behavioral processes to these interactions has been the focus of numerous studies designed to investigate the intricate pathways that are involved in the "mind-body connection." In addition, the effects of this connection on the development and progression of various disease conditions are of considerable interest. Although efforts have been made to identify the cellular and molecular mechanisms underlying these relationships, the impact of genetic makeup on the communication among these systems has yet to be fully realized. The development of sophisticated genetic analytical methods and gene mapping techniques now provide the "tools" to determine the influence of genetics on behavior-neuroendocrine-immune interactions--an area of study that may represent the next frontier in psychoneuroimmunology.

Differential effects of stress-induced adrenal function on components of the herpes simplex virus-specific memory cytotoxic T-lymphocyte response

We have previously demonstrated in a murine model system that psychological stress, applied in the form of physical restraint, suppresses both the activation of splenic-derived, herpes simplex virus (HSV)-specific memory cytotoxic T-lymphocytes (CTLm) to the lytic phenotype and the production of cytokines associated with CTL activation and function. In the studies described herein, we investigated the hypothesis that an adrenal-dependent event is responsible, either in whole or in part, for these observations. While adrenalectomy was shown to abrogate stress-induced suppression of both HSV-specific CTLm activation and the production of IL-6 and IFN-gamma, the reduction in splenic cellularity associated with restraint stress remained, In addition, a role for adrenal function in the regulation of splenic cellularity and IFN-gamma production in non-stressed mice was observed. Together, these results indicate that both adrenal-dependent and adrenal-independent events, operative under both baseline and stress conditions, mediate control of the memory component of the cellular immune response to HSV infection. Overall, these studies provide insight into the mechanisms by which psychological stress modulates immune responsiveness to viral pathogens.

Endocrine regulation of the immune response to influenza virus infection with a metabolite of DHEA-androstenediol

In these studies the influence of androstenediol on the course of an experimental virus infection was examined. Pretreatment with 320 mg/kg AED protected male mice from lethal influenza virus infection. In addition, AED enhanced antigen-induced trafficking of mononuclear cells into the draining lymph node and augmented antigen-specific activation of helper-T cells, which are important for control of viral pathogenesis. Furthermore, AED prevented the characteristic increase in serum corticosterone noted during influenza A virus infection. Although steroid hormones, at least corticosteroids, typically suppress host immune and inflammatory responses in vivo, these data suggest that AED may function to augment host immune and inflammatory responses in contrast to corticosteroids.

The impact of psychological stress on the efficacy of anti-viral adoptive immunotherapy in an immunocompromised host

Adoptive immunotherapy represents a potentially effective approach by which to control the extent of viral infections in an immunocompromised host. However, the impact of psychological stress and its associated neuroendocrine components on the efficacy of such a treatment strategy has yet to be determined. In the studies described herein, we have developed and utilized a model of primary, local herpes simplex virus (HSV) infection in radiation-induced, immunosuppressed C57BL/6 mice to investigate the role of stress in altering the protective capacity of adoptively transferred lymphocytes that contribute to the resolution of primary HSV infection. The sublethal dose of irradiation chosen for this model was shown to abrogate the local, adaptive immune response to HSV infection as measured by the degree of in vivo lymphoproliferation, development of HSV-specific cytotoxic T lymphocytes (CTL), and production of gamma interferon (IFN-gamma). Both short- and long-term acute stress, applied in the form of physical restraint, diminished the effectiveness of adoptively transferred lymphocytes as was indicated by an enhancement of viral replication in the footpad tissue and an increased rate of mortality. A reduction in the levels of IFN-gamma at the site of primary HSV infection represented at least one mechanism underlying this suppression of anti-viral immunity. Furthermore, the time-dependent restoration of immune function following irradiation was shown to be compromised in mice subjected to the restraint stress procedure. Together, these findings emphasize the potential role of psychological stress in suppressing both the capability of adoptive immunotherapeutic procedures to combat viral infection and the reestablishment of immune function in individuals who have undergone immunosuppressive therapy.

Psychoneuroimmunology: animal models of disease

OBJECTIVE

Psychoneuroimmunology, which investigates the bidirectional communication between the central nervous system and the immune system, has been greatly advanced by the use of animal models. The objective of this paper is to describe animal models of disease that can or might be utilized to elucidate neural-immune interactions that alter pathogenesis.

METHODS

This paper reviews animal studies that have demonstrated a link among the brain, behavior, immunity, and disease, highlighting models in which the potential contribution of CNS-immune interactions has not yet been explored.

RESULTS

Animal studies allow for careful control of environmental stimuli, genetic background, and immunological challenge. As such, they are an important component of psychoneuroimmunology research. Models in which one might study the role of psychosocial factors in immunologically mediated disease processes, as in the case of other pathophysiologic processes, profit from an ability to manipulate both stressful events and the magnitude of the challenge to the immune system.

CONCLUSIONS

Animal studies in psychoneuroimmunology highlight the complexity of the interactions among behavior, the brain, the immune system, and pathogen. The genetic background of the animal (both in terms of central nervous and immune system responses), its previous history, the nature of the stressor, the nature of the pathogen and the type of immune response generated are some of the interacting factors that determine the magnitude and direction of stress-induced changes in disease outcome.

Adenovirus gene transfer causes inflammation in the brain

We report that injecting an E1-deleted, non-replicating, human adenovirus type 5 vector into the brain leads to an inflammatory response. Much of this inflammation is induced directly by the virion particles themselves rather than through the expression of new proteins from the vector. The severity of inflammation was found to depend on the strain of inbred rat used: PVG rats have less inflammation than AO rats in response to a vector injection. Twelve hours after injection of adenovirus vectors into the striatum of AO rats, leukocytes were seen marginating to the walls of nearby blood vessels. By two days there was a large increase in major histocompatibility complex class I expression and a heavy infiltration of leukocytes, mainly macrophages and T cells. Retrograde transport of adenovirus to neurons of the substantia nigra was associated with a delayed and less intense inflammation at this distant site. Although AO and PVG rats showed comparable responses in the striatum up to six days, at later times PVG rats had less intense inflammation. In spite of the inflammatory response, vector-driven expression of the marker protein beta-galactosidase and an adenovirus early protein was seen for at least two months following the injection, although expression declined with time. The observation that adenovirus gene transfer leads to an inflammatory response in the brain must be taken into account when planning and interpreting experiments with these vectors. Furthermore, we conclude that using an appropriate strain of rat can diminish some aspects of the inflammation.