Disease-related disgust promotes antibody release in human saliva

Host avoidance and resistance vary independently and are specific to parasite genotype

Hosts can reduce the negative fitness effects of parasite infection by avoiding contact with parasites or by resisting infection after contact. Because of their shared outcome, avoidance and resistance have been hypothesized to trade off with one another. Assuming these defenses carry fitness costs, hosts are expected to have high levels of one defense or the other, but not both. Alternatively, avoidance and resistance may covary positively, if, for example, they complement one another or are genetically or mechanistically linked. Testing these hypotheses requires measuring avoidance and resistance independently, which is challenging because they are functionally linked. In this study, we separated avoidance and resistance of the host C. elegans against the bacterial parasite S. marcescens and tested for a correlation between them. We phenotyped a panel of 12 genetically divergent hosts using two distinct bacterial strains and multiple experimental contexts. We found no evidence of a correlation between avoidance and resistance. This result suggests that avoidance and resistance can covary independently. Moreover, we found strong genetic specificity not only for resistance, but also for a measure of avoidance, motivating further research to examine the coevolutionary dynamics of avoidance.

The influence of everyday emotions on mucosal immunity: An intensive longitudinal modeling approach

Mucosal immunity is a multifaceted system of immunological responses that provides a barrier against pathogenic invasion and can be regulated by psychosocial and neuroendocrine factors. The present study aims to elucidate the association between everyday emotional states, emotion regulation skills, and mucosal immunity by utilizing an ambulatory assessment approach. 30 healthy subjects (61% male; M = 30.18 years old) completed an emotion questionnaire (PANAS) and collected saliva samples via passive drool to determine salivary immunoglobulin-A (S-IgA) excretion rate three times a day over a period of 1 week. In a multi-level model, the influence of emotions on S-IgA, both on a within-subject and between-subject level, was estimated. We found that most of the variation in S-IgA (74%) was accounted for by within-subject changes rather than stable between-subject differences. On a within-subject level, negative emotions had a significant positive effect on S-IgA levels (b = 1.87, p = .015), while positive emotions had no effect. This effect of negative emotions was moderated by the individual emotion regulation skills, with higher regulation skills corresponding to smaller effects (b = -2.67, p = .046). Furthermore, S-IgA levels decreased over the course of a day, indicating circadian rhythmicity (b = -0.13, p = .034). These results highlight the possibilities of intensive longitudinal data to investigate the covariance between psychological and immunological states over time.

Mindfulness in Pregnancy and Postpartum: Protocol of a Pilot Randomized Trial of Virtually Delivered Mindfulness-Based Cognitive Therapy to Promote Well-Being during the Perinatal Period

BACKGROUND

During the period from pregnancy through the first year postpartum, vulnerable individuals are at elevated risk for the onset or worsening of psychological distress, and accessible (e.g., virtually delivered) mental health interventions are needed. Research suggests that Mindfulness-Based Cognitive Therapy (MBCT) can effectively mitigate psychological distress, although few studies have evaluated MBCT in the perinatal period, and samples have been clinically homogenous. Thus, we have designed and are conducting a pilot trial of virtually delivered MBCT with pregnant individuals experiencing a range of psychological symptoms to assess its feasibility and preliminarily explore its effectiveness. Here, we present the study protocol.

METHODS

Eligible participants (target N = 70) are ≥18 years with pregnancies between 12 and 30 weeks of gestation. Participants complete a diagnostic interview, self-report symptom ratings, and a computerized cognitive battery assessing self-regulation at the baseline. Participants are then randomized to either MBCT or care as usual. The MBCT intervention involves eight weekly group sessions delivered virtually, with each session focusing on a mindfulness practice followed by group discussion and skill development. Participants in the intervention group are also encouraged to practice mindfulness skills between sessions. Participants in the control condition are provided with information about mindfulness and treatment resources. Baseline measures are repeated following the eight-week intervention period and at three months postpartum.

CONCLUSIONS

This pilot study is designed to evaluate the feasibility of virtually delivered MBCT and explore group differences in psychological symptoms during the perinatal period, and will lay the foundation for a larger clinical trial focused on optimizing this intervention to improve psychological functioning among diverse pregnant individuals.

Neurobiology of Pathogen Avoidance and Mate Choice: Current and Future Directions

Animals are under constant threat of parasitic infection. This has influenced the evolution of social behaviour and has strong implications for sexual selection and mate choice. Animals assess the infection status of conspecifics based on various sensory cues, with odours/chemical signals and the olfactory system playing a particularly important role. The detection of chemical cues and subsequent processing of the infection threat that they pose facilitates the expression of disgust, fear, anxiety, and adaptive avoidance behaviours. In this selective review, drawing primarily from rodent studies, the neurobiological mechanisms underlying the detection and assessment of infection status and their relations to mate choice are briefly considered. Firstly, we offer a brief overview of the aspects of mate choice that are relevant to pathogen avoidance. Then, we specifically focus on the olfactory detection of and responses to conspecific cues of parasitic infection, followed by a brief overview of the neurobiological systems underlying the elicitation of disgust and the expression of avoidance of the pathogen threat. Throughout, we focus on current findings and provide suggestions for future directions and research.

The COVID-19 pandemic and changes in social behavior: Protective face masks reduce deliberate social distancing preferences while leaving automatic avoidance behavior unaffected

Protective face masks were one of the central measures to counteract viral transmission in the COVID-19 pandemic. Prior research indicates that face masks impact various aspects of social cognition, such as emotion recognition and social evaluation. Whether protective masks also influence social avoidance behavior is less clear. Our project assessed direct and indirect measures of social avoidance tendencies towards masked and unmasked faces in two experiments with 311 participants during the first half of 2021. Two interventions were used in half of the participants from each sample (Experiment 1: protective face masks; Experiment 2: a disease prime video) to decrease or increase the salience of the immediate contagion threat. In the direct social avoidance measure, which asked for the deliberate decision to approach or avoid a person in a hypothetical social encounter, participants showed an increased willingness to approach masked as opposed to unmasked faces across experiments. This effect was further related to interindividual differences in pandemic threat perception in both samples. In the indirect measure, which assessed automatic social approach and avoidance tendencies, we neither observed an approach advantage towards masked faces nor an avoidance advantage for unmasked faces. Thus, while the absence of protective face masks may have led to increased deliberate social avoidance during the pandemic, no such effect was observed on automatic regulation of behavior, thus indicating the relative robustness of this latter behavior against changes in superordinate social norms.

Disgust sensitivity and psychopathic behavior: A narrative review

Humans live under constant threat from pathogenic microorganisms and minimizing such threat has been a major evolutionary selective force in shaping human behavior and health. A particular adaptive mechanism against the harm caused by parasites and their infectiousness is disgust sensitivity, which has evolved to detect and avoid poisonous foods as well as bodily secretions harboring virulent microorganisms. This ubiquitous and reflexive behavior requires the integration of several internal and external sensory signals between the brain, the autonomic nervous system (ANS), and the gastrointestinal tract. Although the emotional expression of disgust is experienced by almost all individuals, the neural mechanisms of sensory signals underlying disgust sensitivity may differ in certain psychiatric conditions. Psychopathy, for instance, is a personality disorder in which disgust sensitivity to contagious bodily secretions is apparently absent or downregulated from its atypical personality temperament. In this review, we provide convergent behavioral, anatomical, and cellular evidence to suggest that a fractured experience of disgust sensitivity might be an additional feature of psychopathic behavior. First, we discuss the neural networks of certain brain regions mediating the emotional states of disgust and then discuss the intersection of the ANS and gastrointestinal tract in the processing of disgust and its relevance to aberrant antisocial behavior. Together, this work highlights the interconnections between the brain and the bilateral body plan as an integrated cell network that is relevant for understanding common principles underlying function and dysfunction of disgust levels in psychiatric domains.

SARS-CoV-2 specific sIgA in saliva increases after disease-related video stimulation

Secretory immunoglobulin A (sIgA) in saliva is the most important immunoglobulin fighting pathogens in the respiratory tract and may thus play a role in preventing SARS-CoV-2 infections. To gain a better understanding of the plasticity in the mucosal antibody, we investigated the proactive change in secretion of salivary SARS-CoV-2-specific sIgA in 45 vaccinated and/or previously infected, generally healthy persons (18 to 35 years, 22 women). Participants were exposed to a disease video displaying humans with several respiratory symptoms typical for COVID-19 in realistic situations of increased contagion risk. The disease video triggered an increase in spike-specific sIgA, which was absent after a similar control video with healthy people. The increase further correlated inversely with revulsion and aversive feelings while watching sick people. In contrast, the receptor binding domain-specific sIgA did not increase after the disease video. This may indicate differential roles of the two salivary antibodies in response to predictors of airborne contagion. The observed plasticity of spike-specific salivary antibody release after visual simulation of enhanced contagion risk suggests a role in immune exclusion.

Family support during childhood as a predictor of mate retention and kin care in adults during the COVID-19 pandemic in Brazil: an exploratory study

Introduction

Experiences during development help to explain behavior expression in adulthood.

Aims

In this study, we explored how unpredictability and harshness experienced during childhood may have impacted the occurrence of reproductive milestones in adulthood and the expression of fundamental motives related to self-protection, disease avoidance, mate seeking, mate retention, and kin care (children/family) during the pandemic.

Methods

This was an exploratory study with 438 participants. Through the administration of online questionnaires, participants were assessed and categorized based on their childhood experiences, resulting in three groups: low unpredictability, high unpredictability with family support, and high unpredictability without family support.

Results

We found that family support experienced during childhood predicts a slow life-history strategy. This involves an emphasis on growth and parenting efforts at the expense reproduction and was relevant even for participants who faced financial unpredictability. During the pandemic, we also observed that mate retention and kin care (family) motives were predominant among individuals who had greater family support during childhood.

Discussion

Overall, the findings suggest that unpredictability experienced during childhood is crucial for the development of life-history strategies and the manifestation of fundamental motives in adulthood.

The walking sick: Perception of experimental sickness from biological motion

Identification of sick conspecifics allows for avoidance of infectious threats, and is therefore an important behavioral defense against diseases. Here, we investigated if humans can identify sick individuals solely from biological motion and posture (using point-light displays). Additionally, we sought to determine which movements and sickness parameters would predict such detection. We collected video clips and derived point-light displays (one stride presented in a loop) of sick walkers (injected with lipopolysaccharide at 2.0 ng/kg body weight) and the same walkers when healthy (injected with saline). We then presented these displays to two groups, one group classified each walker as sick or healthy (study 1, n = 106), and the other group scored the walkers' health on a visual analogue scale (study 2, n = 106). The raters were able to identify sick individuals above chance, and rated sick walkers as having worse health, both from observing video clips and point-light displays. Furthermore, both sickness detection and worse apparent health were predicted by inflammation-induced increase in rigidity and slower walking, but not other cues. Altogether, these findings indicate that biological motion can serve as a sickness cue, possibly allowing humans to identify sick conspecifics from a distance, and thereby allowing for disease avoidance.

Disgusting odors trigger the oral immune system

Recent research has characterized the behavioral defense against disease. In particular the detection of sickness cues, the adaptive reactions (e.g. avoidance) to these cues and the mediating role of disgust have been the focus. A presumably important but less investigated part of a behavioral defense is the immune system response of the observer of sickness cues. Odors are intimately connected to disease and disgust, and research has shown how olfaction conveys sickness cues in both animals and humans. This study aims to test whether odorous sickness cues (i.e. disgusting odors) can trigger a preparatory immune response in humans. We show that subjective and objective disgust measures, as well as TNFα levels in saliva increased immediately after exposure to disgusting odors in a sample of 36 individuals. Altogether, these results suggest a collaboration between behavioral mechanisms of pathogen avoidance in olfaction, mediated by the emotion of disgust, and mechanisms of pathogen elimination facilitated by inflammatory mediators. Disgusting stimuli are associated with an increased risk of infection. We here test whether disgusting odors, can trigger an immune response in the oral cavity. The results indicate an increase level of TNFα in the saliva. This supports that disease cues can trigger a preparatory response in the oral cavity.