Pediatric neuropsychiatric syndromes associated with infection and microbiome alterations: clinical findings, possible role of the mucosal epithelium, and strategies for the development of new animal models

INTRODUCTION

: Subsets of pediatric obsessive-compulsive disorder (OCD) and autism spectrum disorder (ASD) respectively have been associated with respiratory tract infections and alterations in the intestinal microbiome. Pediatric Acute-onset Neuropsychiatric Syndromes (PANS) refers to the sudden onset of neuropsychiatric symptoms that are triggered by several different infectious and non-infectious factors. Clinical studies and animal modeling are consistent with the proposal that inflammation plays an important etiological role in PANS, as well as in ASD associated with gut dysbiosis.

AREAS COVERED

The authors provide an overview of clinical studies of PANS and ASD associated with gastrointestinal symptoms, as well as the current strategies for studying these syndromes in rodent models. Finally, the authors highlight similarities between these syndromes that may provide clues to common etiological mechanisms.

EXPERT OPINION

Although data from existing animal models are consistent with an important role for anti-neuronal antibodies in PANS triggered by GAS infection, we lack models for identifying pathophysiological mechanisms of PANS associated with other infectious and non-infectious triggers. The authors propose a strategy for developing such models that incorporates known vulnerability and triggering factors for PANS into the modeling process. This novel strategy should expand our understanding of the pathophysiology of PANS, as well as facilitate the development of new pharmacological treatments for PANS and related syndromes.

Dataset on c-Fos expression within components of corticostriatal thalamocortical circuits during the expression of a compulsive-like behavior in the female rabbit: Brain-behavior relationships

The dataset describes regional brain c-Fos expression and a component of maternal nest building behavior ("straw carrying") in 5 late term pregnant rabbits that had been allowed to interact with straw (a nest building material) for a discrete period (30 min), during which repetitive straw carrying behavior was initiated. Animals were sacrificed for brain c-Fos immunoreactivity 1 h after straw was placed into their cage. Regional brain c-Fos expression: Neuronal c-Fos expression is known to associate with a sustained increase in neuronal excitation above resting levels, primarily due to its induction in response to increased glutamatergic input and corresponding activation of the NMDA receptor. In practice, c-Fos expression is taken to be an indication of an increase in "neuronal activity". Importantly, there is a lag of approximately 20 to 30 min between the onset of the stimulus that caused increased excitation, and the initiation of neuronal c-Fos expression, and c-Fos has a cellular half-life of approximately 1 h. Thus, the pattern of brain c-Fos expression within a brain histological section represents a composite snapshot of "superimposed" regional activations that occurred within approximately 30 min to 2 h prior to sacrifice. Behavioral variables: Behavioral variables included in the present dataset are those that reflect the repetitive nature of straw carrying (straw carrying cycle frequency), as well as individual subcomponents of this behavior (collecting straw, interacting with the nest site), and indicators of the "rigidity" of expression of these subcomponents across all cycle repetitions (standard deviations of time spent collecting straw, time spent interacting with nest site). Exploratory Factor Analysis (EFA) with cluster rotation was applied in an exploratory manner in order to clarify correlational relationships between regional c-Fos expression and specific behavioral variables.

Activation of cortical and striatal regions during the expression of a naturalistic compulsive-like behavior in the rabbit

Nest building behavior in the pregnant rabbit (Oryctolagus cuniculus) can serve as a model for compulsions in obsessive compulsive disorder (OCD). Previous work showed that the "straw carrying" phase of nest building (during which the rabbit repeatedly collects straw in its mouth, carries it into the nest box and deposits it there, and then returns to collect more) is associated with increased c-FOS expression (a marker of neuronal activity) in the orbitofrontal, anterior cingulate, and piriform cortices. In the present study, we quantified c-FOS expression in the caudate and putamen, as well as in the primary motor, somatosensory, and prefrontal cortices of: (1) pregnant rabbits given straw (PREG + STRAW); pregnant rabbits not given straw (PREG); (3) estrous rabbits given straw (ESTROUS + STRAW); and (4) estrous rabbits not given straw (ESTROUS). We found that straw carrying was associated with increased c-FOS expression in the dorsal putamen, ventral caudate, primary motor cortex, and somatosensory cortex. Additionally, a correlational analysis of PREG + STRAW animals revealed that these regions, along with the premotor and prelimbic cortices, were significantly intercorrelated with respect to c-FOS expression, suggesting their "coactivation" during repetitive straw carrying. By contrast, behavioral interactions of non-pregnant (ESTROUS) rabbits with straw (e.g., sniffing, nibbling it) were associated with a distinct pattern of c-FOS expression that included the medial and ventral putamen. c-FOS expression in PREG + STRAW rabbits is similar to patterns of regional brain activity in OCD patients exposed to obsession-provoking stimuli, as well as to those observed in healthy human mothers responding to infant-associated stimuli.