Antibiotic treatment attenuates behavioral and neurochemical changes induced by exposure of rats to group a streptococcal antigen

Dopamine receptor autoantibody signaling in infectious sequelae differentiates movement versus neuropsychiatric disorders

Despite growing recognition, neuropsychiatric diseases associated with infections are a major unsolved problem worldwide. Group A streptococcal (GAS) infections can cause autoimmune sequelae characterized by movement disorders, such as Sydenham chorea, and neuropsychiatric disorders. The molecular mechanisms underlying these diseases are not fully understood. Our previous work demonstrates that autoantibodies (AAbs) can target dopaminergic neurons and increase dopamine D2 receptor (D2R) signaling. However, AAb influence on dopamine D1 receptor (D1R) activity is underexplored. We found evidence that suggests GAS-induced cross-reactive AAbs promote autoimmune encephalitis of the basal ganglia, a region of high dopamine receptor density. Here, we report a mechanism whereby neuropsychiatric syndromes are distinguished from movement disorders by differences in D1R and D2R AAb titers, signaling, receiver operating characteristic curves, and immunoreactivity with D1R and D2R autoreactive epitopes. D1R AAb signaling was observed through patient serum AAbs and novel patient-derived monoclonal antibodies (mAbs), which induced both D1R G protein- and β-arrestin-transduced signals. Furthermore, patient AAbs and mAbs enhanced D1R signaling mechanisms mediated by the neurotransmitter dopamine. Our findings suggest that AAb-mediated D1R signaling may contribute to the pathogenesis of neuropsychiatric sequelae and inform new options for diagnosis and treatment of GAS sequelae and related disorders.

Ceftriaxone Inhibits Conditioned Fear and Compulsive-like Repetitive Marble Digging without Central Nervous System Side Effects Typical of Diazepam-A Study on DBA2/J Mice and a High-5HT Subline of Wistar-Zagreb 5HT Rats

Background: Ceftriaxone upregulates GLT1 glutamate transporter in the brain and may have anti-CFC and anti-OCD effects. Methods: Twenty WZ-5HT rats were used to investigate the effects of ceftriaxone on obsessive-compulsive (OCD)-like behaviour in the marble-burying (MB) test, freezing behaviour in contextual fear conditioning (CFC) and expression of GLT1 protein in the hippocampus or amygdala using immunoblots. Fifteen DBA/2J mice were used in the MB test. We also compared diazepam with ceftriaxone in open-field, beam-walking, and wire-hanging tests on 47 DBA/2J mice. Ceftriaxone (200 mg/kg) and saline were applied intraperitoneally, once daily for 7 (rats) or 5 (mice) consecutive days. A single dose of diazepam (1.5-3.0 mg/kg) or saline was injected 30 min before the behavioural tests. Results: Ceftriaxone significantly diminished OCD-like behaviour (↓ number of marbles buried) and freezing behaviour in CFC context session (↑ latencies, ↓ total duration, ↓ duration over four 2 min periods of the session) but increased GLT1 protein expression in the amygdala and hippocampus of rats. Diazepam induced sedation, ataxia and myorelaxation in mice. Ceftriaxone did not have these side effects. Conclusions: The results of this study confirm the anti-CFC and anti-OCD effects of ceftriaxone, which did not produce the unwanted effects typical of diazepam.

Urinary Tract Infection in Parkinson's Disease

Urinary tract infection (UTI) is a common precipitant of acute neurological deterioration in patients with Parkinson's disease (PD) and a leading cause of delirium, functional decline, falls, and hospitalization. Various clinical features of PD including autonomic dysfunction and altered urodynamics, frailty and cognitive impairment, and the need for bladder catheterization contribute to an increased risk of UTI. Sepsis due to UTI is a feared consequence of untreated or undertreated UTI and a leading cause of morbidity in PD. Emerging research suggests that immune-mediated brain injury may underlie the pathogenesis of UTI-induced deterioration of PD symptoms. Existing strategies to prevent UTI in patients with PD include use of topical estrogen, prophylactic supplements, antibiotic bladder irrigation, clean catheterization techniques, and prophylactic oral antibiotics, while bacterial interference and vaccines/immunostimulants directed against common UTI pathogens are potentially emerging strategies that are currently under investigation. Future research is needed to mitigate the deleterious effects of UTI in PD.

Increased Compulsivity in Adulthood after Early Adolescence Immune Activation: Preclinical Evidence

Immune activation during early developmental stages has been proposed as a contributing factor in the pathogenesis of neuropsychiatric conditions such as obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, and autism in both human and animal studies. However, its relationship with the vulnerability to inhibitory control deficit, which is a shared feature among those conditions, remains unclear. The present work studied whether postnatal immune activation during early adolescence, combined with exposure to early-life adverse events, could lead to adult vulnerability to impulsive and/or compulsive behaviors. Male Wistar rats were exposed to lipopolysaccharide (LPS) in early adolescence at postnatal day 26 (PND26). During peripuberal period, half of the animals were exposed to a mild stress protocol. In adulthood, behavioral assessment was performed with the aid of the sustained attentional 5-choice serial reaction time (5-CSRT) task, schedule-induced polydipsia (SIP), and open-field locomotor activity and novelty reactivity. Rats exposed to LPS showed more compulsive responses than their control counterparts on 5-CSRT task, although no differences were observed in SIP or locomotor responses. Our study contributes to the knowledge of the relationship between immune activation and inhibitory control deficit. Future studies should aim to disentangle how, and to what extent, immune activation impacts behavior, and to understand the role of early life mild stress.

Microbiota-gut-brain axis as a regulator of reward processes

Our gut harbours trillions of microorganisms essential for the maintenance of homeostasis and host physiology in health and disease. In the last decade, there has been a growing interest in understanding the bidirectional pathway of communication between our microbiota and the central nervous system. With regard to reward processes there is accumulating evidence from both animal and human studies that this axis may be a key factor in gating reward valence. Focusing on the mesocorticolimbic pathway, we will discuss how the intestinal microbiota is involved in regulating brain reward functions, both in natural (i.e. eating, social or sexual behaviours) and non-natural reinforcers (drug addiction behaviours including those relevant to alcohol, psychostimulants, opioids and cannabinoids). We will integrate preclinical and clinical evidence suggesting that the microbiota-gut-brain axis could be implicated in the development of disorders associated with alterations in the reward system and how it may be targeted as a promising therapeutic strategy. Cover Image for this issue: https://doi.org/10.1111/jnc.15065.

Unravelling the role of gut microbiota in Parkinson's disease progression: Pathogenic and therapeutic implications

In recent years, researchers have shown interest in bi-directional interaction between the brain and gut, called "gut-brain axis". Emerging pieces of evidence indicate that disturbances in this axis is found to be associated with the Parkinson's disease (PD). Several clinical investigations revealed the crucial role of gut microbiota in the pathogenesis of PD. It has been suggested that aggregation of misfolded protein α-syn, the neuropathological hallmark of PD, might begin in gut and propagates to the CNS via vagus nerve and olfactory bulb. Emerging evidences also suggest that initiation and progression of PD may be due to inflammation originating from gut. It has been shown that microbial gut dysbiosis causes the production of various pathogenic microbial metabolites which elevates pro-inflammatory environment in the gut that promotes neuroinflammation in the CNS. These observations raise the intriguing question - how gut microbial dysbiosis could contribute to PD progression. In this context, various microbiota-targeted therapies are under consideration that can re-establish the intestinal homeostasis which may have greater promise in the prevention and treatment of PD. This review focuses on the role of the gut microbiota in the initiation, progression of PD and current therapeutic intervention to deplete the severity of the disease.

Increased vulnerability to impulsive behavior after streptococcal antigen exposure and antibiotic treatment in rats

RATIONALE

The inflammation induced by Group A Streptococcus (GAS) infection has been viewed as a vulnerability factor in mental disorders characterized by inhibitory control deficits, such as attention-deficit/hyperactivity disorder or obsessive-compulsive disorder. Antibiotic treatment reduces GAS symptoms; however, its effects on impulsivity have not been fully assessed.

OBJECTIVES

We investigated whether GAS exposure during early adolescence might be a vulnerability factor for adult impulsivity, if antibiotic treatment acts as a protective factor, and whether these differences are accompanied by changes in the inflammatory cytokine frontostriatal regions.

METHODS

Male Wistar rats were exposed to the GAS antigen or to vehicle plus adjuvants at postnatal day (PND) 35 (with two boosts), and they received either ampicillin (supplemented in the drinking water) or water alone from PND35 to PND70. Adult impulsivity was assessed using two different models, the 5-choice serial reaction time task (5-CSRT task) and the delay discounting task (DDT). The levels of interleukin-6 (IL-6) and IL-17 were measured in the prefrontal cortex (PFc), and the tumor necrosis factor α levels (TNFα) were measured in the PFc and nucleus accumbens (NAcc).

RESULTS

GAS exposure and ampicillin treatment increased the waiting impulsivity by a higher number of premature responses when the animals were challenged by a long intertrial interval during the 5-CSRT task. The GAS exposure revealed higher impulsive choices at the highest delay (40 s) when tested by DDT, while coadministration with ampicillin prevented the impulsive choice. GAS exposure and ampicillin reduced the IL-6 and IL-17 levels in the PFc, and ampicillin treatment increased the TNFα levels in the NAcc. A regression analysis revealed a significant contribution of GAS exposure and TNFα levels to the observed effects.

CONCLUSIONS

GAS exposure and ampicillin treatment induced an inhibitory control deficit in a different manner depending on the form of impulsivity measured here, with inflammatory long-term changes in the PFc and NAcc that might increase the vulnerability to impulsivity-related neuropsychiatric disorders.

Neuropsychiatric consequences of childhood group A streptococcal infection: A systematic review of preclinical models

In recent years, clinical studies have shown strong epidemiological evidence of an increased risk of developing neuropsychiatric disorders after childhood exposure to streptococcal infection, including the Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infection (PANDAS). New preclinical studies on group A streptococcus (GAS) exposure investigate how to disentangle the influences of immune activation to induce long-term neurobehavioral effects associated with neuropsychiatric disorders such as obsessive-compulsive disorder, schizophrenia or autism. The present systematic review collects neurobehavioral evidence regarding the use of GAS exposure in animal models to study the vulnerability to different neuropsychiatric disorders, improving our understanding of its possible causes and consequences, and compares its contribution with other preclinical models of immune activation in a variety of paradigms. Specifically, we reviewed the effects of postnatal GAS exposure, in comparison with post- and prenatal exposure to Lipopolysaccharide (LPS) and Polyinosinic:polycytidylic acid (Poly I:C), on the long-term effects concerning psychomotor, cognition and socioemotional outcomes in rodents. GAS exposure in animal models has revealed different behavioral alterations such as reduced locomotion and motor coordination, a deficit in sensorimotor gating, learning, working memory, altered social behavior, and increased anxiety and stereotyped behavior. Most of the results found are in accordance with other immune activation models -LPS and Poly I:C-, with some discrepancies. The systematic review of the literature supports the preclinical model of GAS exposure as a valid model for studying the neurobehavioral consequences of streptococcal infections. Future studies on streptococcal infection could contribute increasing our knowledge on preventive actions or treatments for neuropsychiatric disorders.

Molecular Mimicry, Autoimmunity, and Infection: The Cross-Reactive Antigens of Group A Streptococci and their Sequelae

The group A streptococci are associated with a group of diseases affecting the heart, brain, and joints that are collectively referred to as acute rheumatic fever. The streptococcal immune-mediated sequelae, including acute rheumatic fever, are due to antibody and cellular immune responses that target antigens in the heart and brain as well as the group A streptococcal cross-reactive antigens as reviewed in this article. The pathogenesis of acute rheumatic fever, rheumatic heart disease, Sydenham chorea, and other autoimmune sequelae is related to autoantibodies that are characteristic of autoimmune diseases and result from the immune responses against group A streptococcal infection by the host. The sharing of host and streptococcal epitopes leads to molecular mimicry between the streptococcal and host antigens that are recognized by the autoantibodies during the host response. This article elaborates on the discoveries that led to a better understanding of the pathogenesis of disease and provides an overview of the history and the most current thought about the immune responses against the host and streptococcal cross-reactive antigens in group A streptococcal sequelae.

Individualized Immunological Data for Precise Classification of OCD Patients

Obsessive⁻compulsive disorder (OCD) affects about 2% of the general population, for which several etiological factors were identified. Important among these is immunological dysfunction. This review aims to show how immunology can inform specific etiological factors, and how distinguishing between these etiologies is important from a personalized treatment perspective. We found discrepancies concerning cytokines, raising the hypothesis of specific immunological etiological factors. Antibody studies support the existence of a potential autoimmune etiological factor. Infections may also provoke OCD symptoms, and therefore, could be considered as specific etiological factors with specific immunological impairments. Finally, we underline the importance of distinguishing between different etiological factors since some specific treatments already exist in the context of immunological factors for the improvement of classic treatments.

A Double-Blind Randomized Placebo-Controlled Pilot Study of Azithromycin in Youth with Acute-Onset Obsessive-Compulsive Disorder

OBJECTIVES

Sudden and severe onset of obsessive-compulsive disorder (OCD) may present secondary to infectious and/or immune-mediated triggers. We assessed the preliminary efficacy, tolerability, and safety of azithromycin compared with placebo in the treatment of OCD and associated symptoms in children with pediatric acute-onset neuropsychiatric syndrome (PANS).

METHODS

Thirty-one youth aged 4-14 years (M = 8.26 ± 2.78 years, 62.5% male) were randomized to receive either placebo or azithromycin for 4 weeks (10 mg/kg up to 500 mg per day). Both groups were administered twice daily probiotics. The primary outcome, obsessive-compulsive symptom severity, was assessed using the OCD Clinical Global Impressions Severity (CGI-S OCD) and Children's Yale-Brown Obsessive Compulsive Scale (CY-BOCS).

RESULTS

Participants in the azithromycin group (n = 17) showed significantly greater reductions in OCD severity on the CGI-S OCD than the placebo group (n = 14) posttreatment (p = 0.003), although there were no significant differences on the CY-BOCS. Significantly more participants in the azithromycin condition met treatment responder criteria on the CGI-I OCD at the end of week 4 (41.2%, n = 7) in comparison to the placebo group (7.1%, n = 1; p = 0.045). Tic severity moderated treatment response, with greater tic severity being associated with enhanced treatment response on the CGI-S OCD. Azithromycin was well tolerated with minimal adverse effects and no study dropouts due to side effects. However, the azithromycin group showed a trend toward significantly greater electrocardiography QTc (p = 0.060) at the end of week 4, and significantly more reports of loose or abnormal stools (p = 0.009).

CONCLUSION

This double blind pilot study suggests that azithromycin may be helpful in treating youth meeting the PANS diagnosis, especially those with elevated levels of both OCD and tic symptoms. Azithromycin was well tolerated, but the potential for cardiac risks suggests that additional monitoring may be needed to ensure safety.

An expert opinion on PANDAS/PANS: highlights and controversies

OBJECTIVES

'Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections' (PANDAS) identified a unique subgroup of patients with abrupt onset of obsessive compulsive disorder (OCD) symptoms clinically related to Streptococcus infection and accompanied by neuropsychological and motor symptoms. After almost 20 years, PANDAS has not been accepted as distinct disorder and new criteria for paediatric acute-onset neuropsychiatric syndrome (PANS) have been replaced it, highlighting the fact that several agents rather than only Streptococcus might be involved.

METHODS

Extensive review of the PANDAS/PANS literature was performed on PubMed.

RESULTS

Although antibiotics have been reported to be effective for acute and prophylactic phases in several uncontrolled studies and non-steroidal anti-inflammatory drugs (NSAID) are used during exacerbations, clinical multicenter trials are still missing. Selective serotonin reuptake inhibitors (SSRIs) and cognitive behavioural therapy (CBT) are still the first line of recommendation for acute onset OCD spectrum. Immunological therapies should be restricted to a few cases.

CONCLUSIONS

While PANDAS has found no confirmation as a distinct syndrome, and it is not presented in DSM-5, patients with acute onset OCD spectrum, neurocognitive and motor symptoms should be evaluated for inflammatory, infective, immunological and metabolic abnormalities with a comprehensive diagnostic algorithm.

Gut microbiota: Implications in Parkinson's disease

Gut microbiota (GM) can influence various neurological outcomes, like cognition, learning, and memory. Commensal GM modulates brain development and behavior and has been implicated in several neurological disorders like Alzheimer's disease, multiple sclerosis, amyotrophic lateral sclerosis, anxiety, stress and much more. A recent study has shown that Parkinson's disease patients suffer from GM dysbiosis, but whether it is a cause or an effect is yet to be understood. In this review, we try to connect the dots between GM and PD pathology using direct and indirect evidence.

Acute rheumatic fever and rheumatic heart disease

Acute rheumatic fever (ARF) is the result of an autoimmune response to pharyngitis caused by infection with group A Streptococcus. The long-term damage to cardiac valves caused by ARF, which can result from a single severe episode or from multiple recurrent episodes of the illness, is known as rheumatic heart disease (RHD) and is a notable cause of morbidity and mortality in resource-poor settings around the world. Although our understanding of disease pathogenesis has advanced in recent years, this has not led to dramatic improvements in diagnostic approaches, which are still reliant on clinical features using the Jones Criteria, or treatment practices. Indeed, penicillin has been the mainstay of treatment for decades and there is no other treatment that has been proven to alter the likelihood or the severity of RHD after an episode of ARF. Recent advances - including the use of echocardiographic diagnosis in those with ARF and in screening for early detection of RHD, progress in developing group A streptococcal vaccines and an increased focus on the lived experience of those with RHD and the need to improve quality of life - give cause for optimism that progress will be made in coming years against this neglected disease that affects populations around the world, but is a particular issue for those living in poverty.

Autoimmunity against dopamine receptors in neuropsychiatric and movement disorders: a review of Sydenham chorea and beyond

Antineuronal autoantibodies are associated with the involuntary movement disorder Sydenham chorea (SC) and paediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS) which are characterized by the acute onset of tics and/or obsessive compulsive disorder (OCD). In SC and PANDAS, autoantibodies signal human neuronal cells and activate calcium calmodulin-dependent protein kinase II (CaMKII). Animal models immunized with group A streptococcal antigens demonstrate autoantibodies against dopamine receptors and concomitantly altered behaviours. Human monoclonal antibodies (mAbs) derived from SC target and signal the dopamine D2L (long) receptor (D2R). Antibodies against D2R were elevated over normal levels in SC and acute-onset PANDAS with small choreiform movements, but were not elevated over normal levels in PANDAS-like chronic tics and OCD. The expression of human SC-derived anti-D2R autoantibody V gene in B cells and serum of transgenic mice demonstrated that the human autoantibody targets dopaminergic neurones in the basal ganglia and other types of neurones in the cortex. Here, we review current evidence supporting the hypothesis that antineuronal antibodies, specifically against dopamine receptors, follow streptococcal exposures and may target dopamine receptors and alter central dopamine pathways leading to movement and neuropsychiatric disorders.

Post-infectious group A streptococcal autoimmune syndromes and the heart

There is a pressing need to reduce the high global disease burden of rheumatic heart disease (RHD) and its harbinger, acute rheumatic fever (ARF). ARF is a classical example of an autoimmune syndrome and is of particular immunological interest because it follows a known antecedent infection with group A streptococcus (GAS). However, the poorly understood immunopathology of these post-infectious diseases means that, compared to much progress in other immune-mediated diseases, we still lack useful biomarkers, new therapies or an effective vaccine in ARF and RHD. Here, we summarise recent literature on the complex interaction between GAS and the human host that culminates in ARF and the subsequent development of RHD. We contrast ARF with other post-infectious streptococcal immune syndromes - post-streptococcal glomerulonephritis (PSGN) and the still controversial paediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS), in order to highlight the potential significance of variations in the host immune response to GAS. We discuss a model for the pathogenesis of ARF and RHD in terms of current immunological concepts and the potential for application of in depth "omics" technologies to these ancient scourges.