Social separation, housing relocation, and survival in simian AIDS: a retrospective analysis

Effect of Single Housing on Innate Immune Activation in Immunodeficiency Virus-Infected Pigtail Macaques ( Macaca nemestrina ) as a Model of Psychosocial Stress in Acute HIV Infection

OBJECTIVE

Simian immunodeficiency virus (SIV) infection of macaques recapitulates many aspects of HIV pathogenesis and is similarly affected by both genetic and environmental factors. Psychosocial stress is associated with immune system dysregulation and worse clinical outcomes in people with HIV. This study assessed the impact of single housing, as a model of psychosocial stress, on innate immune responses of pigtailed macaques ( Macaca nemestrina ) during acute SIV infection.

METHODS

A retrospective analysis of acute SIV infection of 2- to si6-year-old male pigtailed macaques was performed to compare the innate immune responses of socially ( n = 41) and singly ( n = 35) housed animals. Measures included absolute monocyte count and subsets, and in a subset ( n ≤ 18) platelet counts and activation data.

RESULTS

SIV infection resulted in the expected innate immune parameter changes with a modulating effect from housing condition. Monocyte number increased after infection for both groups, driven by classical monocytes (CD14 + CD16 - ), with a greater increase in socially housed animals (227%, p < .001, by day 14 compared with preinoculation time points). Platelet numbers recovered more quickly in the socially housed animals. Platelet activation (P-selectin) increased by 65% ( p = .004) and major histocompatibility complex class I surface expression by 40% ( p = .009) from preinoculation only in socially housed animals, whereas no change in these measures occurred in singly housed animals.

CONCLUSIONS

Chronic psychosocial stress produced by single housing may play an immunomodulatory role in the innate immune response to acute retroviral infection. Dysregulated innate immunity could be one of the pathways by which psychosocial stress contributes to immune suppression and increased disease severity in people with HIV.

Short-Term Relocation Stress-Induced Hematological and Immunological Changes in Saimiri boliviensis boliviensis

Nonhuman primates are frequently transported to a new location or temporarily relocated within their colony. Both transportation and relocation expose animals to new environments, causing them to undergo a stress response (before adapting). In our NHP colony, the mentioned situations are not infrequent for many reasons, including maintenance. The objective of this study was to determine whether abrupt changes consisting of relocation, housing, separation, and grouping could influence hematological and immunological parameters and thereby functional activity. The current study used squirrel monkeys as a model to investigate the stress-inducing effects of relocation within a facility, while animals acclimated to new situations (physical, housing). A detailed blood analysis revealed significant changes in lymphocytes, triglycerides, total protein, creatinine, and ALT. Flow cytometric analysis of peripheral blood showed reduction in CD3+, CD4+, and CD8+ T cells and monocytes, while B cells and natural killer (NK) cells changed with relocation. Simultaneously, changes in functional activity of immune cells altered proliferative responses and as shown by ELISpot (IFN γ). Though the parameters studied are not affected as severely as those in animals transported by road or air, stress responses induced by intrafacility relocation are significant and worth consideration. Our findings indicate that squirrel monkeys mimic the features seen in humans exposed to social stressors and may serve an important model for understanding the mechanisms of stress-induced immune dysfunction in humans.

Prenatal Relocation Stress Enhances Resilience Under Challenge in Infant Rhesus Macaques

The prenatal period is a developmental stage of peak sensitivity, during which environmental exposures can program post-natal developmental outcomes. Prenatal stress, in particular, has often been associated with detrimental neurobehavioral outcomes like mood and anxiety disorders. In the present study, we examined the effects of a stressful prenatal maternal experience (maternal relocation during pregnancy) on the post-partum development of offspring in rhesus macaques. To help isolate the effects of prenatal stress from genetic predispositions and post-natal experience, we compared biologically reared infants (infants raised with their biological mothers) with cross-fostered infants (those raised by non-related females in new social groups). We examined the effects of prenatal relocation stress on measures collected at 3-4 months of age during a standardized biobehavioral assessment. Unexpectedly, we found that prenatal stress resulted in a behavioral pattern consistent with resilience rather than anxiety: prenatal stress was linked with greater activity, lower anxiety, and more interaction with novel objects, as well as higher ratings of temperamental confidence during assessment. These effects were observed in infants reared by biological mothers as well as cross-fostered infants, suggesting that the effects of prenatal stress were not attributable to maternal genetics or post-natal factors. Our surprising results suggest that prenatal relocation stress may confer resilience in infant rhesus monkeys.

Effects of relocation on immunological and physiological measures in female squirrel monkeys (Saimiri boliviensis boliviensis)

In the present study, we have quantified the effects of transport, relocation and acclimate/adapt to their new surroundings on female squirrel monkey. These responses are measured in blood samples obtained from squirrel monkeys, at different time points relative to their relocation from their old home to their new home. A group of squirrel monkeys we transported, by truck, for approximately 10 hours. Peripheral blood mononuclear cells (PBMCs) were assayed in order to evaluate the phenotype of lymphocyte subsets by flow, mitogen-specific immune responses of PBMCs in vitro, and levels of cytokines at various time points including immediately before transport, immediately upon arrival, and after approximately 150 days of acclimation. We observed significant changes in T cells and subsets, NK and B cells (CD4⁺, CD8⁺, CD4⁺/CD8⁺, CD16⁺, and CD20⁺). Mitogen specific (e.g. PHA, PWM and LPS) proliferation responses, IFN-γ by ELISPOT assay, and cytokines (IL-2, IL-4 and VEGF) significant changes were observed. Changes seen in the serum chemistry measurements mostly complement those seen in the hematology data. The specific goal was to empirically assess the effects of relocation stress in squirrel monkeys in terms of changes in the numbers and functions of various leukocyte subsets in the blood and the amount of time required for acclimating to their new environment. Such data will help to determine when newly arrived animals become available for use in research studies.

Personality, environmental stressors, and diarrhea in Rhesus macaques: An interactionist perspective

Previous research has repeatedly shown both personality and psychological stress to predict gastrointestinal disorders and chronic diarrhea in humans. The goal of the present research was to evaluate the role of personality, as well as psychological stressors (i.e., housing relocations and rearing environment), in predicting chronic diarrhea in captive Rhesus macaques, with particular attention to how personality regulated the impact of such stressors. Subjects were 1,930 R. macaques at the California National Primate Research Center reared in a variety of environments. All subjects took part in an extensive personality evaluation at approximately 90-120 days of age. Data were analyzed using generalized linear models to determine how personality, rearing condition, housing relocations, and personality by environment interactions, predicted both diarrhea risk (an animal's risk for having diarrhea at least once) and chronic diarrhea (how many repeated bouts of diarrhea an animal had after their initial bout). Much like the human literature, we found that certain personality types (i.e., nervous, gentle, vigilant, and not confident) were more likely to have chronic diarrhea, and that certain stressful environments (i.e., repeated housing relocations) increased diarrhea risk. We further found multiple interactions between personality and environment, supporting the "interactionist" perspective on personality and health. We conclude that while certain stressful environments increase risk for chronic diarrhea, the relative impact of these stressors is highly dependent on an animal's personality.

Laboratory rhesus macaque social housing and social changes: Implications for research

Macaque species, specifically rhesus (Macaca mulatta), are the most common nonhuman primates (NHPs) used in biomedical research due to their suitability as a model of high priority diseases (e.g., HIV, obesity, cognitive aging), cost effective breeding and housing compared to most other NHPs, and close evolutionary relationship to humans. With this close evolutionary relationship, however, is a shared adaptation for a socially stimulating environment, without which both their welfare and suitability as a research model are compromised. While outdoor social group housing provides the best approximation of a social environment that matches the macaque behavioral biology in the wild, this is not always possible at all facilities, where animals may be housed indoors in small groups, in pairs, or alone. Further, animals may experience many housing changes in their lifetime depending on project needs, changes in social status, management needs, or health concerns. Here, we review the evidence for the physiological and health effects of social housing changes and the potential impacts on research outcomes for studies using macaques, particularly rhesus. We situate our review in the context of increasing regulatory pressure for research facilities to both house NHPs socially and mitigate trauma from social aggression. To meet these regulatory requirements and further refine the macaque model for research, significant advances must be made in our understanding and management of rhesus macaque social housing, particularly pair-housing since it is the most common social housing configuration for macaques while on research projects. Because most NHPs are adapted for sociality, a social context is likely important for improving repeatability, reproducibility, and external validity of primate biomedical research. Am. J. Primatol. 79:e22528, 2017. © 2016 Wiley Periodicals, Inc.

Training laboratory primates – benefits and techniques

Abstract. This review discusses the benefits of training in the effective management of laboratory-housed nonhuman primates, including improved welfare, facilitated husbandry, improved quality of data, and human–animal relationships. Training implies that the animals cooperate in aspects of their own care and is a type of enrichment. Some refined ways of using negative reinforcement are discussed, as well as management perspectives on laboratory primate training. Several approaches to dealing with fear are described: systematic desensitization/counterconditioning (SD/CC) versus combined reinforcement training (NPRT). In addition, a detailed shaping plan covering target training, useful when e.g. moving, weighing, or stationing animals, is presented.

Animal housing and welfare: effects of housing conditions on body weight and cortisol in a medium-sized rodent (Cavia aperea)

Rodents are the most abundant experimental nonhuman animals and are commonly studied under standard laboratory housing conditions. As housing conditions affect animals' physiology and behavior, this study investigated the effects of indoor and outdoor housing conditions on body weight and cortisol level of wild cavies, Cavia aperea. The changing housing condition strongly influenced both parameters, which are commonly used as indicators for animal welfare. The transfer from outdoor to indoor enclosures resulted in a body-weight loss of about 8%. In contrast, animals kept indoors showed a substantial weight gain of about 12% when they were transferred outdoors. These effects were reversible. To substantiate a connection between body-weight changes and the health states of the animals, blood basal cortisol concentrations were measured. Animals kept outdoors had significantly lower cortisol levels than did animals kept indoors. These results imply that indoor conditions have a direct effect on the animals' states. The physiological and metabolic consequences as well as potential welfare aspects should be taken into account when planning experimental work, especially on nondomestic animals.

The neuroendocrinology of social isolation

Social isolation has been recognized as a major risk factor for morbidity and mortality in humans for more than a quarter of a century. Although the focus of research has been on objective social roles and health behavior, the brain is the key organ for forming, monitoring, maintaining, repairing, and replacing salutary connections with others. Accordingly, population-based longitudinal research indicates that perceived social isolation (loneliness) is a risk factor for morbidity and mortality independent of objective social isolation and health behavior. Human and animal investigations of neuroendocrine stress mechanisms that may be involved suggest that (a) chronic social isolation increases the activation of the hypothalamic pituitary adrenocortical axis, and (b) these effects are more dependent on the disruption of a social bond between a significant pair than objective isolation per se. The relational factors and neuroendocrine, neurobiological, and genetic mechanisms that may contribute to the association between perceived isolation and mortality are reviewed.

The influences of perinatal challenge persist into the adolescent period in socially housed bonnet macaques (Macaca radiata)

Social challenges during the perinatal period influence the mother-infant relationship in nonhuman primates and may affect the offspring's response to later social challenge(s). Relocation of a breeding colony of monkeys (Macaca radiata) created two groups of infants: one group experienced social group relocation to a new housing facility during the perinatal period (ATYPICAL) and the second group developed within a constant environment (TYPICAL). At a mean age of 25 months, all animals were removed from their natal group and placed in same sex adolescent social groups. Behavioral observations were collected after group formation or introduction to a new group. ATYPICAL subjects showed increased aggression and reduced affiliation compared to TYPICAL subjects. Hair cortisol in male subjects collected 6 months after introduction was elevated in the ATYPICAL subjects compared to TYPICAL subjects. These findings demonstrate that early life challenges affect behavior as well as stress hormone responses to social challenge in adolescence.

Repeated intranasal oxytocin administration in early life dysregulates the HPA axis and alters social behavior

Agonistic interactions are a powerful stressor. Conversely, positive social interactions can reduce the adverse effects of social stress. This possibly occurs through the action of oxytocin (OT), a neuropeptide able to reduce activation of the hypothalamo-pituitary-adrenal (HPA) axis. We hypothesized that repeated OT intranasal administration to neonatal pigs could provide long-lasting protective effects against social stress. In each of six litters, two pigs per litter received 0.5 mL of saline containing 24 IU (or 50 μg) of OT intranasally and two control littermates received 0.5 mL of saline as a control at 1, 2 and 3 days of age. Contrary to our predictions, when socially mixed after weaning at 17 days of age, neonatally OT-administered pigs received more aggressive interactions and performed more aggressive interactions in return, showed greater locomotion, spent less time in social contact, and had greater cortisol concentrations than control pigs. When this social mixing was repeated at 8 weeks of age, OT pigs still performed more aggressive interactions and had greater adrenocorticotropic hormone concentrations than control pigs. A dexamethasone suppression test and corticotropic releasing hormone administration challenge at 11 weeks of age revealed that OT pigs were less responsive to dexamethasone than control pigs, suggesting a deficient HPA axis' negative feedback control. Postnatal repeated OT administration altered social behavior and resulted in a long-term dysregulation of the HPA axis. These findings highlight the complex, fine-tuning of the neurobiological mechanisms regulating the development of social behavior and suggest caution in the application of neonatal peptide treatments during early development.

Inflammatory vulnerability associated with the rh5-HTTLPR genotype in juvenile rhesus monkeys

Individual variation in serotonergic function is associated with reactivity, risk for affective disorders, as well as an altered response to disease. Our study used a nonhuman primate model to further investigate whether a functional polymorphism in the promoter region for the serotonin transporter gene helps to explain differences in proinflammatory responses. Homology between the human and rhesus monkey polymorphisms provided the opportunity to determine how this genetic variation influences the relationship between a psychosocial stressor and immune responsiveness. Leukocyte numbers in blood and interleukin-6 (IL-6) responses are sensitive to stressful challenges and are indicative of immune status. The neutrophil-to-lymphocyte ratio and cellular IL-6 responses to in vitro lipopolysaccharide stimulation were assessed in 27 juvenile male rhesus monkeys while housed in stable social groups (NLL  = 16, NS  = 11) and also in 18 animals after relocation to novel housing (NLL  = 13, NS  = 5). Short allele monkeys had significantly higher neutrophil-to-lymphocyte ratios than homozygous Long allele carriers at baseline [t(25) = 2.18, P = 0.02], indicative of an aroused state even in the absence of disturbance. In addition, following the housing manipulation, IL-6 responses were more inhibited in short allele carriers (F1,16  = 8.59, P = 0.01). The findings confirm that the serotonin transporter gene-linked polymorphism is a distinctive marker of reactivity and inflammatory bias, perhaps in a more consistent manner in monkeys than found in many human studies.

Physiological and Welfare Consequences of Transport, Relocation, and Acclimatization of Chimpanzees (Pan troglodytes)

Manipulations of the environments of captive nonhuman primates often have welfare consequences to the animals, including behavioral effects, and for certain manipulations, physiological effects as well. The processes of transporting, relocating, and acclimatizing nonhuman primates across facilities represent manipulations that are likely to have welfare, behavioral, and physiological consequences to the relocated animals. Seventy-two chimpanzees were relocated from the Primate Foundation of Arizona (PFA) in Arizona to the Keeling Center (KCCMR) in Texas. Animals were transported for approximately 21 h in single cages in a USDA-approved, climate-controlled trailer. Chimpanzees were weighed, anesthetized, and blood samples were collected 1) immediately prior to departure from PFA, 2) immediately upon arrival at the KCCMR, and 3) at additional time point(s) between 3 and 12 weeks after arrival at the KCCMR. Chimpanzees were quarantined in familiar pairs or social groups for 60-90 days at the KCCMR. Blood samples were analyzed for hematological and clinical chemistry parameters and compared across time points. In addition, samples from a subset of animals were assayed for cell-mediated immune parameters. Comparisons of the data obtained just prior to transport, to the data obtained immediately upon arrival, revealed numerous statistically significant differences in hematological, clinical chemistry, and immunological parameters. Some of these were indicative of stress, and thus, changes in welfare state, although many remained within the published normal ranges for chimpanzees. Additional analyses showed that many of the clinical chemistry values collected 3 to 12 weeks after arrival at the KCCMR had returned to pre-transport values. In contrast, of the cell-mediated immune parameters that were affected by transport and relocation, few had returned to pre-transport levels 8 weeks after transport, and three of the four hematology variables analyzed had not returned to pre-transport levels 12 weeks after transport. Comparisons of body weights before and immediately after transport revealed that animals lost an average of 2.5 kg during the 21-h transport, a statistically significant reduction that some animals never regained. These results demonstrate that transport and relocation affect a variety of physiological parameters with potential welfare implications and that some of these effects last as long as 3 months. These findings have important implications for the welfare and use of recently transported nonhuman primates, especially chimpanzees, in biomedical research. In order to allow animals to adapt to their new surroundings and to prevent unwanted confounds from influencing experiments, sufficient time must be provided after transport for chimpanzees to acclimatize.

Early rearing interacts with temperament and housing to influence the risk for motor stereotypy in rhesus monkeys (Macaca mulatta)

Laboratory and zoo housed non-human primates sometimes exhibit abnormal behaviors that are thought to reflect reduced wellbeing. Previous research attempted to identify risk factors to aid in the prevention and treatment of these behaviors, and focused on demographic (e.g. sex or age) and experience-related (e.g. single housing or nursery rearing) factors. However, not all animals that display abnormal behavior possess these risk factors and some individuals that possess a risk factor do not show behavioral abnormalities. We hypothesized that other aspects of early experience and individual characteristics might identify animals that were more likely to display one specific abnormal behavior, motor stereotypy (MS). Using logistic regression we explored the influence of early rearing (involving four different types of rearing conditions), and variation in temperament, on likelihood of displaying MS while controlling for previously identified risk factors. Analyses indicated that having a greater proportion of life lived indoors, a greater proportion of life-indoors singly-housed, and a greater number of anesthesias and blood draws significantly increased the risk of displaying MS (P < 0.001). Rearing condition failed to independently predict the display of MS; however significant interactions indicated that single housing had a greater impact on risk for indoor-reared animals versus outdoor-reared animals, and for indoor mother-reared animals versus nursery-reared animals. There were no main effects of temperament, although interactions with rearing were evident: scoring high on Gentle or Nervous was a risk factor for indoor-reared animals but not outdoor-reared animals. The final model accounted for approximately 69.3 % of the variance in the display of MS, and correctly classified 90.6% of animals. These results indicate that previously identified risk factors may impact animals differently depending on the individual's early rearing condition. These results are also the first in non-human primates to demonstrate that individual difference factors, like temperament, could be additional tools to identify animals at highest risk for motor stereotypy.

Challenges to bonnet monkey (Macaca radiata) social groups: Mother-infant dyad and infant social interactions

The mother-infant dyad is crucial to early development in a variety of species. The complexity of social groupings in nonhuman primates makes this relationship resilient as well as susceptible to early challenges associated with environmental chaos. Quantitative behavior observations of bonnet monkey mother-infant interactions were collected from 28 mother-infant dyads between one and twelve months of age. Social groups were subjected to several prenatal and/or postnatal housing relocations within a single year resulting in two study groups. One group experienced relocations (ATYPICAL, n = 14) and the second group (TYPICAL, n = 14) was conceived and reared in the same location. Behaviors in the ethogram included mother-infant interactions and infant social interactions with other members of the group. Observations between ages of two to four months were analyzed by a mixed model analysis of variance including fixed effects of per and postnatal history (TYPICAL, ATYPICAL), age, and history by age interaction and random effects of mother and infant nested within mother. A significant effect of relocation history was noted on a number of infant behaviors. ATYPICAL infants were out of direct contact with their mother at an earlier age but remained in her proximity. Control of proximity shifted to offsrping in the ATYPICAL group compared to the TYPICAL group. Furthermore, greater social interactions between two and four months of age with other members of the social group as well as the ir mother were observed in the ATYPICAL group. It is suggested that continuous challenge associated with relocation may affect the infant at later developmental ages due to these early differences in ways that are yet unclear.

Genetic characterization of specific pathogen-free rhesus macaque (Macaca mulatta) populations at the California National Primate Research Center (CNPRC)

A study based on 14 STRs was conducted to understand intergenerational genetic changes that have occurred within the California National Primate Research Center's (CNPRC) regular specific pathogen-free (SPF) and super-SPF captive rhesus macaque populations relative to their conventional founders. Intergenerational genetic drift has caused age cohorts of each study population, especially within the conventional population, to become increasingly differentiated from each other and from their founders. Although there is still only minimal stratification between the conventional population and either of the two SPF populations, separate derivation of the regular and super-SPF animals from their conventional founders has caused the two SPF populations to remain marginally different from each other. The regular SPF and, especially, the super-SPF populations have been influenced by the effects of differential ancestry, sampling, and lost rare alleles, causing a substantial degree of genetic divergence between these subpopulations. The country of origin of founders is the principal determinant of the MHC haplotype composition of the SPF stocks at the CNPRC. Selection of SPF colony breeders bearing desired genotypes of Mamu-A*01 or -B*01 has not affected the overall genetic heterogeneity of the conventional and the SPF research stocks.Because misclassifying the ancestry of research stocks can undermine experimental outcomes by excluding animals with regional-specific genotypes or phenotypes of importance, understanding founder/descendent genetic relationships is crucial for investigating candidate genes with distinct geographic origins. Together with demographic management, population genetic assessments of SPF colonies can curtail excessive phenotypic variation among the study stocks and facilitate successful production goals.

Personality and serotonin transporter genotype interact with social context to affect immunity and viral set-point in simian immunodeficiency virus disease

From the beginning of the AIDS epidemic, stress has been a suspected contributor to the wide variation seen in disease progression, and some evidence supports this idea. Not all individuals respond to a stressor in the same way, however, and little is known about the biological mechanisms by which variations in individuals' responses to their environment affect disease-relevant immunologic processes. Using the simian immunodeficiency virus/rhesus macaque model of AIDS, we explored how personality (Sociability) and genotype (serotonin transporter promoter) independently interact with social context (Stable or Unstable social conditions) to influence behavioral expression, plasma cortisol concentrations, SIV-specific IgG, and expression of genes associated with Type I interferon early in infection. SIV viral RNA set-point was strongly and negatively correlated with survival as expected. Set-point was also associated with expression of interferon-stimulated genes, with CXCR3 expression, and with SIV-specific IgG titers. Poorer immune responses, in turn, were associated with display of sustained aggression and submission. Personality and genotype acted independently as well as in interaction with social condition to affect behavioral responses. Together, the data support an "interactionist" perspective [Eysenck, H.J., 1991. Personality, stress and disease: an interactionist perspective. Psychol. Inquiry 2, 221-232] on disease. Given that an important goal of HIV treatment is to maintain viral set-point as low as possible, our data suggest that supplementing anti-retroviral therapy with behavioral or pharmacologic modulation of other aspects of an organism's functioning might prolong survival, particularly among individuals living under conditions of threat or uncertainty.

Contributions of non-human primates to neuroscience research

Non-human primates have a small but important role in basic and translational biomedical research, owing to similarities with human beings in physiology, cognitive capabilities, neuroanatomy, social complexity, reproduction, and development. Although non-human primates have contributed to many areas of biomedical research, we review here their unique contributions to work in neuroscience, and focus on four domains: Alzheimer's disease, neuroAIDS, Parkinson's disease, and stress. Our discussion includes, for example, the role of non-human primates in development of new treatments (eg, stem cells, gene transfer) before phase I clinical trials in patients; basic research on disease pathogenesis; and understanding neurobehavioural outcomes resulting from genotype-environment interactions.

Understanding the interaction between psychosocial stress and immune-related diseases: a stepwise progression

For many years, anecdotal evidence and clinical observations have suggested that exposure to psychosocial stress can affect disease outcomes in immune-related disorders such as viral infections, chronic autoimmune diseases and tumors. Experimental evidence in humans supporting these observations was, however, lacking. Studies published in the last 2 decades in Brain, Behavior and Immunity and other journals have demonstrated that acute and chronic psychological stress can induce pronounced changes in innate and adaptive immune responses and that these changes are predominantly mediated via neuroendocrine mediators from the hypothalamic-pituitary-adrenal axis and the sympathetic-adrenal axis. In addition, psychological stress has predicted disease outcomes using sophisticated models such as viral challenge, response to vaccination, tracking of herpesvirus latency, exploration of tumor metastasis and healing of experimental wounds, as well as epidemiological investigations of disease progression and mortality. These studies have contributed significantly to our understanding that the neuroendocrine-immune interaction is disturbed in many pathophysiological conditions, that stress can contribute to this disturbance, and that malfunction in these communication pathways can play a significant role in the progression of disease processes. There are, however, significant gaps in the extant literature. In the coming decade(s), it will be essential to further analyze neuroendocrine-immune communication during disease states and to define the specific pathways linking the central nervous system to the molecular events that control important disease-relevant processes. This knowledge will provide the basis for new therapeutic pharmacological and non-pharmacological behavioral approaches to the treatment of chronic diseases via specific modulation of nervous system-immune system communication.

Social stress enhances sympathetic innervation of primate lymph nodes: mechanisms and implications for viral pathogenesis

Behavioral processes regulate immune system function in part via direct sympathetic innervation of lymphoid organs, but little is known about the factors that regulate the architecture of neural fibers in lymphoid tissues. In the present study, we find that experimentally imposed social stress can enhance the density of catecholaminergic neural fibers within axillary lymph nodes from adult rhesus macaques. This effect is linked to increased transcription of the key sympathetic neurotrophin nerve growth factor and occurs predominately in extrafollicular regions of the paracortex that contain T-lymphocytes and macrophages. Functional consequences of stress-induced increases in innervation density include reduced type I interferon response to viral infection and increased replication of the simian immunodeficiency virus. These data reveal a surprising degree of behaviorally induced plasticity in the structure of lymphoid innervation and define a novel pathway by which social factors can modulate immune response and viral pathogenesis.

Immune function declines with unemployment and recovers after stressor termination

OBJECTIVE

To examine the effect of unemployment on natural killer cell cytotoxicity (NKCC) and, in a subsample of persons who become re-employed, to determine if, after termination of the stressor, immune values recover to levels similar to matched controls.

METHODS

One hundred unemployed and 100 matched employed healthy men and women, aged 29 to 45 years, were followed for 4 months with monthly blood samples taken to measure NKCC, the ability of NK cells to kill target cells. Twenty-five participants obtained employment before the end of the study, leaving 75 unemployed (and 75 employed) participants in the main sample. For unemployed participants who obtained employment before the end of the study, subsample analyses compared NKCC levels before and after obtaining a new job.

RESULTS

The persistently unemployed sample had significantly lower NKCC levels for all three effector:target ratios (100:1, p = .0004; 50:1, p = .002; and 25:1, p = .02) when compared with the matched employed sample. There were no significant gender effects. In the subsample analyses, NKCC was significantly higher after the participants became employed, compared with their unemployed period, with substantial "recovery" of immune function (44%-72%) compared with values from the steadily employed group.

CONCLUSIONS

Chronic stress is associated with persistent NKCC impairment. When the chronic stressor is terminated, however, the immune cell functional capacity quickly begins to recover. We believe this is the first study in humans to document immune function recovery after the definable end of a chronic stressor.

Considerations in the selection and conditioning of Old World monkeys for laboratory research: animals from domestic sources

Nonhuman primates from domestic sources constitute an important resource for the research community. The life history of the Old World monkey species that comprise the bulk of this resource is described, and issues that colony managers and researchers alike should consider regarding animal selection (e.g., species, age, sex, rearing history, temperament, genotype, viral status, geographic origin) are discussed. Preparation of domestically bred animals for research usually involves some combination of social separation, relocation, resocialization, alterations in physical space, photoperiod, and diet, as well as exposure to novel environments. The research literature that has focused on these issues is reviewed, and authors suggest that once animals have been assigned to their project housing situation, a period ranging up to 3 mo (depending on the magnitude of the change in housing) might be warranted before an experimental protocol should begin. Attention to issues of animal selection and conditioning by both researchers and colony managers can lead to the shared goal of high-quality research that utilizes the minimal number of animals.

Balancing animal research with animal well-being: establishment of goals and harmonization of approaches

A resource is provided for the creation of an institutional program that balances the scientific mission of an institution with the well-being of the animals used in support of the research. The concept of harmonizing scientific goals with animal well-being was first suggested in the early part of the twentieth century and later revitalized in the literature of the 1950s. Harmonization can best be achieved through the promotion of a team initiative. The team should include, at a minimum, the scientist, veterinarian, institutional animal care and use committee, and animal care staff. It is the responsibility of this animal research team to promote and balance the generation of scientifically valid data with animal well-being. The team must strive to minimize or eliminate non-protocol variables that could adversely affect the validity and repeatability of the experimental data. Good experimental design coupled with excellent communication between team members can often minimize or eliminate many variables and result in both better science and animal well-being. To ensure the scientific validity of experimental data, scientists must be aware of the complex nature of the environment in which their animals are maintained. To ensure repeatablity of an experiment, scientists must document and publish both the inanimate and social environments in which their animals are housed. Better documentation of environmental variables and their correlation with experimental results will promote critical knowledge about the relationships between an animal's environment, its well-being, and science.

Increases in a marker of immune system reconstitution are predated by decreases in 24-h urinary cortisol output and depressed mood during a 10-week stress management intervention in symptomatic HIV-infected men

BACKGROUND

Stress management interventions reduce distress symptoms and hypothalamic-pituitary-adrenal (HPA) axis hormones such as cortisol, which has been related to a down-regulation of immune system components relevant to the human immunodeficiency virus (HIV) infection. We previously showed that HIV+ men assigned to a 10-week cognitive behavioral stress management (CBSM) intervention showed more CD4+CD45RA+CD29+ lymphocytes, an indicator of immune system reconstitution, at a 6- to 12-month follow-up compared with controls. Here, we tested whether reductions in urinary cortisol output and depressed mood during the 10-week CBSM intervention period mediated its effects on this immune system reconstitution marker at follow-up.

METHODS

Twenty-five HIV-infected men randomized to either a 10-week CBSM intervention or a wait-list control provided 24-h urine samples and psychological responses pre- to postintervention, which were related to changes in immune status over a 6- to 12-month follow-up period.

RESULTS

Greater reductions in cortisol output and depressed mood during CBSM appeared to mediate the effects of this intervention on this indicator of immune system reconstitution over the 6- to 12-month follow-up period. Changes in mood were maintained over the follow-up period, although these did not add explanatory information beyond the cortisol and mood changes that were observed during the 10-week intervention period. These findings were not explained by the changes in medications or health behaviors during follow-up.

CONCLUSION

A time-limited CBSM intervention may affect the rate of immune system reconstitution in HIV-infected men by modifying the stress of symptomatic disease. This intervention may work by decreasing depressed mood and normalizing HPA axis functioning.

Stereotypies and Other Abnormal Repetitive Behaviors: Potential Impact on Validity, Reliability, and Replicability of Scientific Outcomes

Normal behavior plays a key role in facilitating homeostasis, especially by allowing the animal to control and modify its environment. Captive environments may interfere with these behavioral responses, and the resulting stress may alter many physiological parameters. Abnormal behaviors indicate that an animal is unable to adjust behaviorally to the captive environment and, hence, may be expressing abnormal physiology. Therefore, captive environments may affect the following aspects of an experiment: validity, by introducing abnormal animals into experiments; reliability, by increasing interindividual variation through the introduction of such individuals; and replicability, by altering the number and type of such individuals between laboratories. Thus, far from increasing variability, enrichment may actually improve validity, reliability, and replicability by reducing the number of abnormal animals introduced into experiments. In this article, the specific example of abnormal repetitive behaviors (ARBs) is explored. ARBs in captive animals appear to involve the same mechanisms as ARBs in human psychiatry, which reflect underlying abnormalities of brain function. ARBs are also correlated with a wide range of behavioral changes that affect experimental outcomes. Thus, ARBs in laboratory animals may compromise validity, reliability, and replicability, especially in behavioral experiments; and enrichments that prevent ARB may enhance validity, reliability, and replicability. Although many links in this argument have been tested experimentally, key issues still remain in the interpretation of these data. In particular, it is currently unclear (1) whether or not the differences in brain function seen in animals performing ARB are abnormal, (2) which common behavioral paradigms are affected by ARB, and (3) whether enrichment does indeed improve the quality of behavioral data. Ongoing and future work addressing these issues is outlined.

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.

Personality influences tetanus-specific antibody response in adult male rhesus macaques after removal from natal group and housing relocation

Previous research has suggested that personality is related to immune function in macaques. Using a prospective design, we examined whether variation in the personality dimension "Sociability" in adult male rhesus macaques (Macaca mulatta) was related to the in vivo secondary antibody response to a tetanus toxoid booster immunization following removal from natal groups and relocation to individual housing. We also explored whether the timing of the immunization following relocation had an impact on the immune response. Blood was sampled at the time of booster immunization, at 14 and 28 days post-immunization, and approximately 9 months post-immunization. Plasma was assayed for tetanus-specific IgG by enzyme-linked immunoassay (ELISA). There was no difference between High- and Low-Sociable animals in antibody levels at the time of the booster immunization. Multivariate analysis of variance (MANOVA) revealed that High-Sociable animals had a significantly higher antibody response following relocation and immunization compared to Low-Sociable animals. There was no effect of timing of the immunization on the immune response. The results confirm that personality factors can affect animals' immune responses, and that the dimension Sociability may be influential in a male's response to social separation and relocation.

An interdisciplinary research model to investigate psychosocial cofactors in disease: Application to HIV-1 pathogenesis

This paper argues for a broader interdisciplinary conceptualization of research on psychosocial risk factors and disease that relies on epidemiology, human laboratory-based studies, animal studies, in vitro and other mechanistic studies and intervention research. A model is proposed that includes the isolation of the active ingredients in the proposed psychological or social contributing factor, and a determination of their neural substrates, peripheral neurophysiological and pathophysiological correlates, and clinical disease outcomes. Research in HIV-1 pathogenesis provides examples of these kinds of studies. The HIV section highlights research that focuses on specific cognitive representations of stressful life experiences as active ingredients that shape the affective and neurophysiological impact of events. Links between these cognitive states and HIV progression, as well as the potential neurophysiologic, virologic, and immunologic mediators of these relationships are described. Implications and extensions of this model are derived for research on psychosocial factors and cancer.

Differential detection of B virus and rhesus cytomegalovirus in rhesus macaques

Non-human primate herpesviruses establish and maintain a lifelong persistent infection in immunocompetent hosts in the absence of clinical signs of disease. A fundamental issue for understanding the natural history of non-human primate herpesviruses is whether the viruses are maintained in a truly latent state or one characterized by a low level of chronic expression. To address this issue, a real-time PCR assay was developed to quantify Cercopithecine herpesvirus type 1 (B virus) DNA in mucosal fluids of rhesus macaques. This assay was rapid, sensitive (10 genome copies) and specific for B virus obtained from multiple species of macaques. The shedding profile of B virus was compared to another endemic herpesvirus, rhesus cytomegalovirus (RhCMV), in colony-reared monkeys. Mucosal swabs or saliva samples were taken daily from two groups of seropositive monkeys undergoing either a stressful relocation (group 1) or daily chair restraint (group 2). B virus DNA was detected in mucosal fluids from four animals relocated during the breeding season (group 1) but not from 10 animals moved at other times of the year. No B virus DNA was detected in any group 2 monkey. In contrast, RhCMV DNA was detected in the majority of animals of both groups 1 and 2. Detection of B virus DNA shedding is a relatively rare event associated with the breeding season, while RhCMV DNA is persistently detected in mucosal fluids of most monkeys.

Environmental stress mediates changes in neuroimmunological interactions

Combinations of environmental stress coordinately increase toxicological assaults on health, dependent on the genetics of the exposed organism. Multiple gene variances between individuals influence the risks associated with environmental exposures, and environmental stress presents in multiple forms including chemical, physical, and psychological stresses. Combined chemical, physical, and psychological stresses are suggested as exacerbating the initiation and/or duration of illnesses, and many of the detrimental outcomes on health are posited to relate to changes in neuroendocrine immune circuitry. However, most human epidemiological or experimental animal studies have not considered the combination of chemical, physical, and psychological stress on health status. Current consideration is being given to "real world" exposures for assessment of health risk, but this mainly relates to evaluation of chemical mixtures. In addition to concomitant chemical exposures having agonistic and/or antagonistic interactions, the physical and psychological status of the individual can influence exposure outcomes. An individual's psychosocial environment is likely to be important in epidemiological investigations. Neuroimmunology is a burgeoning discipline, and neurotoxicology and immunotoxicology studies should consider the bidirectional regulatory mechanisms between these organ systems and the potential long-term influences of psychological stress. This mini-review discusses some intriguing data from animal and human studies, which address the regulatory pathways between the neural, endocrine, and immune systems, with emphasis on psychological stress.

Psychoneuroimmunology and psychosomatic medicine: back to the future

OBJECTIVE

Although psychological modulation of immune function is now a well-established phenomenon, much of the relevant literature has been published within the last decade. This article speculates on future directions for psychoneuroimmunology research, after reviewing the history of the field.

METHODS

This review focuses on human psychoneuroimmunology studies published since 1939, particularly those that have appeared in Psychosomatic Medicine. Studies were clustered according to key themes, including stressor duration and characteristics (laboratory stressors, time-limited naturalistic stressors, or chronic stress), as well as the influences of psychopathology, personality, and interpersonal relationships; the responsiveness of the immune system to behavioral interventions is also addressed. Additionally, we describe trends in populations studied and the changing nature of immunological assessments. The final section focuses on health outcomes and future directions for the field.

RESULTS

There are now sufficient data to conclude that immune modulation by psychosocial stressors or interventions can lead to actual health changes, with the strongest direct evidence to date in infectious disease and wound healing. Furthermore, recent medical literature has highlighted a spectrum of diseases whose onset and course may be influenced by proinflammatory cytokines, from cardiovascular disease to frailty and functional decline; proinflammatory cytokine production can be directly stimulated by negative emotions and stressful experiences and indirectly stimulated by chronic or recurring infections. Accordingly, distress-related immune dysregulation may be one core mechanism behind a diverse set of health risks associated with negative emotions.

CONCLUSIONS

We suggest that psychoneuroimmunology may have broad implications for the basic biological sciences and medicine.

Cognitive-behavioral stress management reduces distress and 24-hour urinary free cortisol output among symptomatic HIV-infected gay men

BACKGROUND

Stress management interventions can reduce symptoms of distress as well as modulate certain immune system components in persons infected with human immunodeficiency virus (HIV). These effects may occur in parallel with reductions in hypothalamic-pituitary-adrenal (HPA) axis hormones such as cortisol, which has been related in other work to a down-regulation of immune system components relevant to HIV infection. The present study tested the effects of a multimodal cognitive-behavioral stress management (CBSM) intervention on 24-hour urinary free cortisol levels and distressed mood in symptomatic HIV+ gay men.

METHODS

Symptomatic HIV-infected gay men who were randomized to either a 10-week group-based CBSM intervention or a 10-week wait-list period provided psychological responses and urine samples pre-post intervention.

RESULTS

Of the 59 participants providing matched questionnaire data, men assigned to CBSM (n = 40) showed significantly lower posttreatment levels of self-reported depressed affect, anxiety, anger, and confusion than those in the wait-list control group (n = 19). Among the 47 men providing urine samples (34 CBSM, 13 controls), those assigned to CBSM revealed significantly less cortisol output as compared to controls. At the individual level, depressed mood decreases paralleled cortisol reductions over this period across the entire sample.

CONCLUSION

A time-limited CBSM intervention reduced distress symptoms and urinary free cortisol output in symptomatic HIV+ gay men and greater reductions in some aspects of distress, especially depressed mood, paralleled greater decreases in cortisol over the intervention period. If persisting stressors and depressed mood contribute to chronic HPA axis activation in HIV-infected persons, then interventions such as CBSM, which teaches them to relax, alter cognitive appraisals, use new coping strategies, and access social support resources, may decrease distress and depressed mood and normalize HPA axis functioning.

Stress and coping: the psychoneuroimmunology of HIV/AIDS

A considerable body of evidence, reviewed in this chapter, suggests that psychosocial factors play an important role in progression of HIV infection, its morbidity and mortality. Psychosocial influences relating to faster disease progression include life-event stress, sustained depression, denial/avoidance coping, concealment of gay identity (unless one is rejection-sensitive), and negative expectancies. Conversely, protective psychosocial factors include active coping, finding new meaning, and stress management. In studying long survivors of HIV/AIDS, our group has found protective effects on health of life involvement, collaborative relationship with doctor, emotional expression, depression (conversely), and perceived stress (conversely). Reviewed and discussed are psychoneuroimmunological pathways by which immune and neuroendocrine mechanisms might link psychosocial factors with health and long survival. Finally, biological factors are also a major determinant of disease progression and include genetics and age of the host, viral strain and virulence, medication and several immune response factors on which psychosocial influences could impact.

The relationship of personality dimensions in adult male rhesus macaques to progression of simian immunodeficiency virus disease

Studies of nonhuman primate personality have suggested that physiological correlates of relevant behavioral dimensions exist. The present study examined personality using techniques similar to those employed in human personality research. Adult male rhesus monkeys were each rated on 25 adjectives while living in their natal groups. Approximately 1.5 years later, 18 animals were inoculated with the simian immunodeficiency virus (SIV) and exposed to socially stable or socially unstable conditions. Behavior, viral load (SIV RNA), plasma cortisol concentrations, and the IgG response to SIV and to rhesus cytomegalovirus were measured at regular intervals. Multiple regression analyses revealed that the four personality dimensions (Sociability, Confidence, Equability, Excitability) were correlated with various measures. Following inoculation with SIV, animals higher in Sociability showed a more rapid decline in plasma cortisol concentrations, elevations in the anti-RhCMV IgG response, and a decline in SIV RNA. The results indicate that personality factors in rhesus monkeys do have physiological correlates that have significance for disease processes and that in the context of a social manipulation, Sociability, reflecting the tendency to engage in affiliative interactions, is an important factor in explaining outcome measures at early time points.