Anticipatory immune changes in women treated with chemotherapy for ovarian cancer

Pavlovian Conditioning of Immunological and Neuroendocrine Functions

The phenomenon of behaviorally conditioned immunological and neuroendocrine functions has been investigated for the past 100 yr. The observation that associative learning processes can modify peripheral immune functions was first reported and investigated by Ivan Petrovic Pavlov and his co-workers. Their work later fell into oblivion, also because so little was known about the immune system’s function and even less about the underlying mechanisms of how learning, a central nervous system activity, could affect peripheral immune responses. With the employment of a taste-avoidance paradigm in rats, this phenomenon was rediscovered 45 yr ago as one of the most fascinating examples of the reciprocal functional interaction between behavior, the brain, and peripheral immune functions, and it established psychoneuroimmunology as a new research field. Relying on growing knowledge about efferent and afferent communication pathways between the brain, neuroendocrine system, primary and secondary immune organs, and immunocompetent cells, experimental animal studies demonstrate that cellular and humoral immune and neuroendocrine functions can be modulated via associative learning protocols. These (from the classical perspective) learned immune responses are clinically relevant, since they affect the development and progression of immune-related diseases and, more importantly, are also inducible in humans. The increased knowledge about the neuropsychological machinery steering learning and memory processes together with recent insight into the mechanisms mediating placebo responses provide fascinating perspectives to exploit these learned immune and neuroendocrine responses as supportive therapies, the aim being to reduce the amount of medication required, diminishing unwanted drug side effects while maximizing the therapeutic effect for the patient’s benefit.

Peri-transplant psychosocial factors and neutrophil recovery following hematopoietic stem cell transplantation

Objective

Multiple psychosocial factors appear to affect cancer progression in various populations; however, research investigating the relationship between psychosocial factors and outcomes following hematopoietic stem cell transplantation (HCT) is scarce. Subject to adverse immunological and psychological conditions, HCT patients may be especially vulnerable to psychosomatic health sequelae; therefore, we studied whether optimism and anxiety influence the pertinent clinical outcome of days to neutrophil engraftment (DTE).

Method

54 adults undergoing either autologous or allogeneic HCT completed self-report questionnaires measuring optimism and anxiety. We assessed the association between these psychosocial variables and DTE.

Results

Greater optimism and less anxiety were associated with the favorable outcome of fewer DTE in autologous HCT recipients, though this relationship was no longer significant when reducing the sample size to only subjects who filled out their baseline survey by the time of engraftment.

Conclusion

Our findings are suggestive that optimism and anxiety may be associated with time to neutrophil recovery in autologous, but not allogeneic, adult HCT recipients. Further investigation in larger, more homogeneous subjects with consistent baseline sampling is warranted.

Aberrant disgust responses and immune reactivity in cocaine-dependent men

BACKGROUND

Infectious diseases are the most common and cost-intensive health complications associated with drug addiction. There is wide belief that drug-dependent individuals expose themselves more regularly to disease-related pathogens through risky behaviors such as sharing pipes and needles, thereby increasing their risk for contracting an infectious disease. However, evidence is emerging indicating that not only lifestyle but also the immunomodulatory effects of addictive drugs, such as cocaine, may account for their high infection risk. As feelings of disgust are thought to be an important psychological mechanism in avoiding the exposure to pathogens, we sought to investigate behavioral, physiological, and immune responses to disgust-evoking cues in both cocaine-dependent and healthy men.

METHODS

All participants (N = 61) were exposed to neutral and disgust-evoking photographs depicting food and nonfood images while response accuracy, latency, and skin conductivity were recorded. Saliva samples were collected before and after exposure to neutral and disgusting images, respectively. Attitudes toward disgust and hygiene behaviors were assessed using questionnaire measures.

RESULTS

Response times to disgust-evoking photographs were prolonged in all participants, and specifically in cocaine-dependent individuals. While viewing the disgusting images, cocaine-dependent individuals exhibited aberrant skin conductivity and increased the secretion of the salivary cytokine interleukin-6 relative to control participants.

CONCLUSION

Our data provide evidence of a hypersensitivity to disgusting stimuli in cocaine-dependent individuals, possibly reflecting conditioned responses to noningestive sources of infection. Coupled with a lack of interoception of bodily signals, aberrant disgust responses might lead to increased infection susceptibility in affected individuals.

Learned placebo responses in neuroendocrine and immune functions

The phenomenon of learned placebo responses in neuroendocrine and immune functions is a fascinating example of communication between the brain and both the endocrine and peripheral immune systems. In this chapter, we will give a short overview of afferent and efferent communication pathways, as well as the central mechanisms, which steer the behavioral conditioned immune response. Subsequently, we will focus on data that provides evidence for learned immune responses in experimental animals and learned neuroendocrine and immune placebo responses in humans. Finally, we will take a critical look at these learning protocols, to determine whether or not they can be considered a viable additional treatment option to pharmacological regimens in clinical routine. This is fundamental, since there are still a number of issues, which need to be solved, such as the potential reproducibility, predictability, and extinction of the learned neuroendocrine and immune responses. Together, these findings not only provide an excellent basis to increase our understanding of human biology but may also have far reaching clinical implications. They pave the way for the ultimate aim of employing associative learning protocols as supportive treatment strategies in pharmacological regimens. As a result, medication levels may be reduced, as well as their unwanted side effects, providing a maximized therapeutic outcome to the benefit of the patient.

Brain-immune interactions and the neural basis of disease-avoidant ingestive behaviour

Neuro-immune interactions are widely manifested in animal physiology. Since immunity competes for energy with other physiological functions, it is subject to a circadian trade-off between other energy-demanding processes, such as neural activity, locomotion and thermoregulation. When immunity is challenged, this trade-off is tilted to an adaptive energy protecting and reallocation strategy that is identified as 'sickness behaviour'. We review diverse disease-avoidant behaviours in the context of ingestion, indicating that several adaptive advantages have been acquired by animals (including humans) during phylogenetic evolution and by ontogenetic experiences: (i) preventing waste of energy by reducing appetite and consequently foraging/hunting (illness anorexia), (ii) avoiding unnecessary danger by promoting safe environments (preventing disease encounter by olfactory cues and illness potentiation neophobia), (iii) help fighting against pathogenic threats (hyperthermia/somnolence), and (iv) by associative learning evading specific foods or environments signalling danger (conditioned taste avoidance/aversion) and/or at the same time preparing the body to counteract by anticipatory immune responses (conditioning immunomodulation). The neurobiology behind disease-avoidant ingestive behaviours is reviewed with special emphasis on the body energy balance (intake versus expenditure) and an evolutionary psychology perspective.

The learned immune response: Pavlov and beyond

The ability to associate physiological changes with a specific flavor was most likely acquired during evolution as an adaptive strategy aimed at protecting the organism while preparing it for danger. The behaviorally conditioned or learned immune response is an exquisite example of the bidirectional communication between the central nervous system (CNS) and the peripheral immune system. How is it possible that specific immuno-modulating properties of a drug or substance (unconditioned stimulus) can be re-enlisted just by the mere re-exposure to a particular taste, odor or environment (conditioned stimulus)? To answer this key question, we review the neurobiological mechanism mediating this type of associative learning, as well as the pathways and mechanisms employed by the brain to harness the immune system during the execution of the conditioned immune response. Finally, we focus on the potential therapeutic relevance of such learned immune responses, and their re-conceptualization within the framework of "learned placebo effects".

Expectations and associations that heal: Immunomodulatory placebo effects and its neurobiology

The use of placebo may have accompanied healing and medical practices since their origins (Plato; Charmides, 155-156). Recent experimental data indicate that we would be well advised to further consider placebo effects in future therapeutic strategies, with a better knowledge of their potency, psychological basis and underlying neurobiological mechanisms. Current research in the areas of pain, depression and Parkinson's disease has uncovered some of the potential neurobiological mechanisms of placebo effects. These data indicate that conscious expectation and unconscious behavioral conditioning processes appear to be the major neurobiological mechanisms capable of releasing endogenous neurotransmitters and/or neurohormones that mimic the expected or conditioned pharmacological effects. To date, research on placebo responses affecting immune-related diseases is scarce, but there are consistent indications that skin and mucosal inflammatory diseases, in particular, are strongly modulated by placebo treatments. However, the brain's capability to modulate peripheral immune reactivity has been impressively demonstrated by paradigms of behavioral conditioning in animal experiments and human studies. Thus, placebo effects can benefit end organ functioning and the overall health of the individual through positive expectations and behavioral conditioning processes.

Anticipatory symptoms and anticipatory immune responses in pediatric cancer patients receiving chemotherapy: features of a classically conditioned response?

There is considerable evidence from studies in adult patients that classical conditioning contributes to anticipatory nausea and/or vomiting (ANV) in cancer chemotherapy: The stimuli predicting the infusion serve as conditioned stimuli (CS). When reexposed to the CS, some patients experience ANV prior to infusion onset. In adult patients, anticipatory immunomodulation (AIM) has also been observed. The present study examines whether ANV and AIM occur in pediatric cancer patients and whether they show features of a conditioned response.

METHODS

Nineteen pediatric cancer patients (M = 10.1 years, > 2 previous chemotherapies) were studied over two consecutive cycles (A, B). In both cycles, self-reported symptoms, for example nausea and vomiting, were recorded from two days prior to the onset (Day -2), during infusion, and two days after the end of the infusion (Day +2). In Cycle B, blood was drawn at home at Day -2, and at Day 0 in the hospital prior to infusion onset, thus using a quasi-experimental variation of the CS content of the environment. Immune parameters valid for tumor defense and cytotoxic competence (natural killer cell activity [NKCA], plasma interleukin [IL]-1beta, IL-2, IL-10, interferon [IFN]-gamma, tumor necrosis factor [TNF]-alpha) and cortisol were measured.

RESULTS

ANV was reported by 7 patients in at least one cycle. In Cycle A, ANV was positively associated with emetogenity of chemotherapy. Features of ANV-duration and occurrence-tended to be positively associated with those of posttreatment nausea and vomiting. AN increased as infusion onset time approached. NKCA and IFN-gamma increased from home to hospital, independent from cortisol level. The NKCA increase was predominantly observed in patients with ANV.

CONCLUSIONS

ANV in pediatric patients showed features of a CR. Immune parameters were sensitive to the CS content of the environment, predominantly in patients with ANV. This is consistent with the manifestation of multiple CRs.

Pavlovian conditioning of immune function: animal investigation and the challenge of human application

Pavlovian conditioning of immune functions provided early impetus to the rapidly expanding knowledge of bi-directional communication among the immune, endocrine, and central nervous systems. Since these early investigations, the phenomenology of this response has been well characterized. However the neural mechanisms and biological relevance of conditioned immunomodulation remain unclear. To this end, we present here data from our laboratories that have: (1) revealed some of the neural mechanisms and biological relevance of an animal model of conditioned immunomodulation; (2) demonstrated the conditionability and potential mechanisms of conditioned immune responses in healthy humans, and (3) investigated conditioned immunomodulation in a clinical sample. Together, these data demonstrate that animal models provide a basis for investigating mechanisms whereby conditioned changes in immune function may modulate health status in a clinical realm.

Effects of overshadowing on conditioned nausea in cancer patients: an experimental study

The infusion of cytotoxic drugs in cancer patients is often accompanied by posttreatment nausea (PN). In addition, patients complain about nausea prior to an infusion [i.e., anticipatory nausea (AN)]. AN is mainly explained by classical conditioning, with the infusion as the unconditioned stimulus (US) and with the stimuli signaling the infusion as conditioned stimuli (CS). Despite this conditioning etiology, a specifically derived therapy to attenuate the CS-US contingency is missing. The purpose of this study is to develop and to test an overshadowing procedure for prevention of AN, and also for the modification of PN intensity. Sixteen cancer patients were assigned to one of two groups: Overshadowing+ (OV+) and Overshadowing- (OV-). At the start of all infusions of two consecutive chemotherapy cycles A and B (acquisition), OV+ subjects drank a saliently tasting beverage (the overshadowing CS), whereas group OV- drank water. All patients received water in cycle C (test). Self-reported symptoms and heart rates were recorded. As expected, in cycle C (test), no patient of group OV+ showed AN, whereas two patients of group OV- developed AN. There was a tendency for a reduction of the intensity of PN, in terms of duration and latency after overshadowing, in cycle C: OV+ patients tended to show a shorter duration and a longer latency between end of infusion and PN onset. In OV-, there was a significantly larger heart rate deceleration in both measurement periods, in the anticipatory and the posttreatment measurement period. Data suggest to apply overshadowing for prevention of AN and modification of PN. Physiological markers of conditioned nausea are revealed. After its procedural implementation, the technique can be used in larger samples now.

Social support and immune status during and after chemotherapy for breast cancer

Social support and immune status were assessed in women treated with adjuvant chemotherapy for breast cancer. Perception of enhanced attachment was associated with an increased number of white blood cell levels three months after, but not during, chemotherapy. After treatment, patients with high attachment ratings had higher numbers and proportions of granulocytes, and lower proportions of lymphocytes and monocytes. It is concluded that the support experienced by a cancer patient can be associated with counts and proportions of leukocytes, but that this effect, if present during chemotherapy, is overridden by the biological factor that affects the haematopoetic process.