Evidence for vagal sensory neural involvement in influenza pathogenesis and disease.

Influenza A virus (IAV) is a common respiratory pathogen and a global cause of significant and often severe morbidity. Although inflammatory immune responses to IAV infections are well described, little is known about how neuroimmune processes contribute to IAV pathogenesis. In the present study, we employed surgical, genetic, and pharmacological approaches to manipulate pulmonary vagal sensory neuron innervation and activity in the lungs to explore potential crosstalk between pulmonary sensory neurons and immune processes. Intranasal inoculation of mice with H1N1 strains of IAV resulted in stereotypical antiviral lung inflammation and tissue pathology, changes in breathing, loss of body weight and other clinical signs of severe IAV disease. Unilateral cervical vagotomy and genetic ablation of pulmonary vagal sensory neurons had a moderate effect on the pulmonary inflammation induced by IAV infection, but significantly worsened clinical disease presentation. Inhibition of pulmonary vagal sensory neuron activity via inhalation of the charged sodium channel blocker, QX-314, resulted in a moderate decrease in lung pathology, but again this was accompanied by a paradoxical worsening of clinical signs. Notably, vagal sensory ganglia neuroinflammation was induced by IAV infection and this was significantly potentiated by QX-314 administration. This vagal ganglia hyperinflammation was characterized by alterations in IAV-induced host defense gene expression, increased neuropeptide gene and protein expression, and an increase in the number of inflammatory cells present within the ganglia. These data suggest that pulmonary vagal sensory neurons play a role in the regulation of the inflammatory process during IAV infection and suggest that vagal neuroinflammation may be an important contributor to IAV pathogenesis and clinical presentation. Targeting these pathways could offer therapeutic opportunities to treat IAV-induced morbidity and mortality.

Comment on Kopanska et al. Disorders of the Cholinergic System in COVID-19 Era-A Review of the Latest Research. Int. J. Mol. Sci. 2022, 23, 672.

We read the recent review article by Marta Kopanska et al. [...].

Reply to Cafiero et al. Comment on "Kopanska et al. Disorders of the Cholinergic System in COVID-19 Era-A Review of the Latest Research. Int. J. Mol. Sci. 2022, 23, 672".

We have carefully read the Letter to the Editor by Concetta Cafiero, Alessandra Micera, Agnese Re, Beniamino Schiavone, Giulio Benincasa, and Raffaele Palmirotta related to our paper entitled "Disorders of the Cholinergic System in COVID-19 Era-A Review of the Latest Research" [...].

Disorders of the Cholinergic System in COVID-19 Era-A Review of the Latest Research.

The appearance of the SARS-CoV-2 virus initiated many studies on the effects of the virus on the human body. So far, its negative influence on the functioning of many morphological and physiological units, including the nervous system, has been demonstrated. Consequently, research has been conducted on the changes that SARS-CoV-2 may cause in the cholinergic system. The aim of this study is to review the latest research from the years 2020/2021 regarding disorders in the cholinergic system caused by the SARS-CoV-2 virus. As a result of the research, it was found that the presence of the COVID-19 virus disrupts the activity of the cholinergic system, for example, causing the development of myasthenia gravis or a change in acetylcholine activity. The SARS-CoV-2 spike protein has a sequence similar to neurotoxins, capable of binding nicotinic acetylcholine receptors (nAChR). This may be proof that SARS-CoV-2 can bind nAChR. Nicotine and caffeine have similar structures to antiviral drugs, capable of binding angiotensin-converting enzyme 2 (ACE 2) epitopes that are recognized by SARS-CoV-2, with the potential to inhibit the formation of the ACE 2/SARS-CoV-2 complex. The blocking is enhanced when nicotine and caffeine are used together with antiviral drugs. This is proof that nAChR agonists can be used along with antiviral drugs in COVID-19 therapy. As a result, it is possible to develop COVID-19 therapies that use these compounds to reduce cytokine production. Another promising therapy is non-invasive stimulation of the vagus nerve, which soothes the body's cytokine storm. Research on the influence of COVID-19 on the cholinergic system is an area that should continue to be developed as there is a need for further research. It can be firmly stated that COVID-19 causes a dysregulation of the cholinergic system, which leads to a need for further research, because there are many promising therapies that will prevent the SARS-CoV-2 virus from binding to the nicotinic receptor. There is a need for further research, both in vitro and in vivo. It should be noted that in the functioning of the cholinergic system and its connection with the activity of the COVID-19 virus, there might be many promising dependencies and solutions.

Optical vagus nerve modulation of heart and respiration via heart-injected retrograde AAV.

Vagus nerve stimulation has shown many benefits for disease therapies but current approaches involve imprecise electrical stimulation that gives rise to off-target effects, while the functionally relevant pathways remain poorly understood. One method to overcome these limitations is the use of optogenetic techniques, which facilitate targeted neural communication with light-sensitive actuators (opsins) and can be targeted to organs of interest based on the location of viral delivery. Here, we tested whether retrograde adeno-associated virus (rAAV2-retro) injected in the heart can be used to selectively express opsins in vagus nerve fibers controlling cardiac function. Furthermore, we investigated whether perturbations in cardiac function could be achieved with photostimulation at the cervical vagus nerve. Viral injection in the heart resulted in robust, primarily afferent, opsin reporter expression in the vagus nerve, nodose ganglion, and brainstem. Photostimulation using both one-photon stimulation and two-photon holography with a GRIN-lens incorporated nerve cuff, was tested on the pilot-cohort of injected mice. Changes in heart rate, surface electrocardiogram, and respiratory responses were observed in response to both one- and two-photon photostimulation. The results demonstrate feasibility of retrograde labeling for organ targeted optical neuromodulation.

Neuroinvasion, neurotropic, and neuroinflammatory events of SARS-CoV-2: understanding the neurological manifestations in COVID-19 patients.

Respiratory viruses are opportunistic pathogens that infect the upper respiratory tract in humans and cause severe illnesses, especially in vulnerable populations. Some viruses have neuroinvasive properties and activate the immune response in the brain. These immune events may be neuroprotective or they may cause long-term damage similar to what is seen in some neurodegenerative diseases. The new "Severe Acute Respiratory Syndrome Coronavirus 2" (SARS-CoV-2) is one of the Respiratory viruses causing highly acute lethal pneumonia coronavirus disease 2019 (COVID-19) with clinical similarities to those reported in "Severe Acute Respiratory Syndrome Coronavirus"(SARS-CoV) and the "Middle East Respiratory Syndrome Coronavirus"(MERS-CoV) including neurological manifestation. To examine the possible neurological damage induced by SARS-CoV-2, it is necessary to understand the immune reactions to viral infection in the brain, and their short- and long-term consequences. Considering the similarities between SARS-CoV and SARS-CoV-2, which will be discussed, cooperative homological and phylogenetical studies lead us to question if SARS-CoV-2 can have similar neuroinvasive capacities and neuroinflammatiory events that may lead to the same short- and long-term neuropathologies that SARS-CoV had shown in human and animal models. To explain the neurological manifestation caused by SARS-CoV-2, we will present a literature review of 765 COVID-19 patients, in which 18% had neurological symptoms and complications, including encephalopathy, encephalitis and cerebrovascular pathologies, acute myelitis, and Guillain-Barré syndrome. Clinical studies describe anosmia or partial loss of the sense of smell as the most frequent symptom in COVID19 patients, suggesting that olfactory dysfunction and the initial ultrarapid immune responses could be a prognostic factor.

Vernet syndrome resulting from varicella zoster virus infection-a very rare clinical presentation of a common viral infection.

Vernet syndrome is a unilateral palsy of glossopharyngeal, vagus, and accessory nerves. Varicella zoster virus (VZV) infection has rarely been described as a possible cause. A 76-year-old man presented with 1-week-long symptoms of dysphonia, dysphagia, and weakness of the right shoulder elevation, accompanied by a mild right temporal parietal headache with radiation to the ipsilateral ear. Physical examination showed signs compatible with a right XI, X, and XI cranial nerves involvement and also several vesicular lesions in the right ear's concha. He had a personal history of poliomyelitis and chickenpox. Laringoscopy demonstrated right vocal cord palsy. Brain MRI showed thickening and enhancement of right lower cranial nerves and an enhancing nodular lesion in the ipsilateral jugular foramen, in T1 weighted images with gadolinium. Cerebrospinal fluid (CSF) analysis disclosed a mild lymphocytic pleocytosis and absence of VZV-DNA by PCR analysis. Serum VZV IgM and IgG antibodies were positive. The patient had a noticeable clinical improvement after initiation of acyclovir and prednisolone therapy. The presentation of a VZV infection with isolated IX, X, and XI cranial nerves palsy is extremely rare. In our case, the diagnosis of Vernet syndrome as a result of VZV infection was made essentially from clinical findings and supported by analytical and imaging data.

Pharyngolaryngeal involvement by varicella-zoster virus.

INTRODUCTION: Involvement of cranial nerves V, VII, and VIII by varicella-zoster virus (VZV) is widely reported in the literature, whereas involvement of cranial nerves IX and X is rarer and therefore poorly characterized. MATERIAL AND METHODS: We performed a systematic review of the literature through MEDLINE (up to January 2012). We selected cases reporting pharyngolaryngeal involvement by VZV and extracted clinical features, complementary studies, treatments, and outcome. We added three cases to the existing literature. RESULTS: Of the 65 screened articles, 38 were included reporting 54 cases. The main clinical features were odynodysphagia and dysphonia reflecting underlying hemipharyngolaryngeal palsy. Vesicles were seen in 66% of the patients. Besides the involvement of cranial nerves IX and X, concomitant involvement of other cranial nerves was seen in 48% of the cases. The most concerned nerves were cranial nerves VII and VIII. Virological tests (63%) and imaging (28%) were performed, with the latter being systematically normal. Seventy-two percent of patients were treated with antiviral agents and/or corticosteroids. Twenty-six percent of patients made a full recovery while the remaining had some persistent deficits. We did not find statistically significant differences in outcomes according to age or treatments received. CONCLUSIONS: Pharyngolaryngeal involvement by VZV is rare and seldom restricted to the ninth and tenth cranial nerves. It occurs mostly within the context of cranial polyneuropathy. Regardless of the treatment, full recovery is rare and long-term sequelae persist in many cases, especially with speech and swallowing impairment. Close monitoring and follow-up are therefore essential.

[Functional morphology of the vagus nerve nuclei changes in the medulla oblongata (N. Ambiguus, N. Dorsalis), induced by influenza a (H(3)N(I)) in experiment].

Morphological changes of the brain cortex IV-V layers, the structures of n. ambiguus, n. dorsalis and n. vagus ganglia on the model of influenza virus A strains (H3NI) MLD50 in number 50 microns intranasal inoculation in mice aged 6-8 weeks were studied. For assessment of virus-induced pathology 2 series of experiments were carried out. Electron microscopy, morphometric and histological methods, including by Nissl stain were used. LD dose, daily loss of body weight with access to the so-called "endpoint" determined previously. Experimental period from 48 hours to 12 days. It is shown that in n.vagus stem structures in the medulla oblongata (n. dorsalis, n. ambiguus) have the mosaic and the polymorphic nature of the changes - signs of influenza virus cytotropic effect, such as swelling, vacuolation, chromatolysis, less pyknosis and hyperchromatosis. In the period of the greatest weight loss and expressed «endpoint¼ irreversible changes in the stem structures associated with n. vagus - apoptotic nuclei and neurons massive edema, lipofuscin accumulation have taken place. Results of the study suggest that the parasympathetic nervous system (n. vagus) may be one of the possible route of influenza A virus (H3NI) genomic structures transnerval invasion in the central nervous system during experimental infection.

The supraspinal innervation of the left adrenal is more intense than that of the right one.

BACKGROUND AND PURPOSE: Previous studies using the viral transneuronal tracing technique demonstrated that central autonomic circuits are involved in the innervation of the adrenal gland. Since increasing number of data indicate laterality in the neuroendocrine system, we aimed to investigate whether the supraspinal innervation of the adrenal gland exhibits asymmetry or not. METHODS: The central circuitry involved in the innervation of the left and the right adrenal gland was studied in individual rats by dual transneuronal tracing using isogenic recombinant strains (BDG and BDL) of Bartha strain of pseudorabies virus. RESULTS: Viral infection of brain nuclei (dorsal vagal nucleus, nucleus of the solitary tract, caudal raphe nuclei, A5 cell group, hypothalamic paraventricular nucleus) from the left adrenal was more severe than that from the right organ. Dual-infected neurons from the two adrenals were also detected both in the brain stem and in the hypothalamus. CONCLUSION: The results indicate a predominance in the supraspinal innervation of the left adrenal gland. Data further suggest that each adrenal gland is innervated both by side-specific neurons and by neurons which project to both organs.

The vagus nerve as a conduit for neuroinvasion, a diagnostic tool, and a therapeutic pathway for transmissible spongiform encephalopathies, including variant Creutzfeld Jacob disease.

It is hypothesised that the vagus nerve (cranial nerve X) is an important conduit for infective neuroinvasion during the incubation of certain transmissible spongiform encephalopathies (TSEs) including scrapie in sheep, variant Creutzfeld Jacob disease in humans, chronic wasting disease in deer, and bovine spongiform encephalopathy in cattle. Presence of infection in the brainstem will disrupt normal function of this important region responsible for autonomic control of visceral function via the vagus nerve. It is proposed that physiological study of disrupted vagal function using techniques such as heart rate variability will indicate early, and ongoing, functional signs of infection even before levels of abnormal prion protein reach the thresholds currently used in tests for the presence of TSEs. It is further suggested that repeated measures of vagal function during treatment with experimental therapies will give a non-invasive, repeated measures index of drug efficacy. In addition, pharmaceutical interventions directed via the vagus nerve will bypass the blood brain barrier and take an anatomical route appropriate to the treatment of TSEs.

[Paresis of the vagus and accessory nerve in the course of the herpes zoster]. / Porazenie nerwów X i XI w przebiegu pólpasca.

INTRODUCTION: The cephalic zoster is a cranial neuritis, with great tendency to diffusion along the nerves. The objective of this article is both to report a case of cranial polineuritis due to herpes zoster infection with laryngeal involvement and review of the relevant literature. MATERIAL AND METHODS: The case of 57-years-old man with unilateral laryngeal mucosal eruptions and complete left vocal paralysis is reported. Laryngeal symptoms, diagnostic criteria and therapeutic result are described. CONCLUSION: 1. In cases of head and neck herpes zoster, the investigations of all cranial nerves should be carried out, and the larynx must always be examinated; 2. Co-occurrence of the neuralgic pain (radiating especially to the ear or the occipital region) with unilateral laryngeal palsy should raise a suspicion that herpes zoster infection may by the causative factor; 3. The explanation of the etiologic cause of a vocal fold paralysis in idiopathic cases, may yield not only diagnostic, but also therapeutic value.

The vagus nerve is one route of transneural invasion for intranasally inoculated influenza a virus in mice.

Intranasally inoculated neurotropic influenza viruses in mice infect not only the respiratory tract but also the central nervous system (CNS), mainly the brain stem. Previous studies suggested that the route of invasion of virus into the CNS was via the peripheral nervous system, especially the vagus nerve. To evaluate the transvagal transmission of the virus, we intranasally inoculated unilaterally vagectomized mice with a virulent influenza virus (strain 24a5b) and examined the distribution of the viral protein and genome by immunohistochemistry and in situ hybridization over time. An asymmetric distribution of viral antigens was observed between vagal (nodose) ganglia: viral antigen was detected in the vagal ganglion of the vagectomized side 2 days later than in the vagal ganglion of the intact side. The virus was apparently transported from the respiratory mucosa to the CNS directly and decussately via the vagus nerve and centrifugally to the vagal ganglion of the vagectomized side. The results of this study, thus, demonstrate that neurotropic influenza virus travels to the CNS mainly via the vagus nerve.

Dexamethasone prevents virus-induced hyperresponsiveness via multiple mechanisms.

In the lungs, neuronal M2 muscarinic receptors inhibit acetylcholine release from the parasympathetic nerves. Parainfluenza virus infection causes loss of M2 receptor function, which increases acetylcholine release and vagally mediated bronchoconstriction. Because glucocorticoids are known to inhibit airway hyperresponsiveness, we tested whether dexamethasone (6.5 or 65 microg/kg i.p.) prevents virus-induced hyperresponsiveness and M2 receptor dysfunction in guinea pigs. In controls, pilocarpine, a muscarinic agonist, inhibited vagally induced bronchoconstriction, demonstrating functional M2 receptors. However, in virus-infected animals, pilocarpine failed to inhibit vagally induced bronchoconstriction, demonstrating M2 receptor dysfunction. Frequency-dependent bronchoconstriction was greater in virus-infected animals than in controls, indicating airway hyperresponsiveness. Low-dose dexamethasone (6.5 microg/kg i.p.) treatment prevented virus-induced airway hyperresponsiveness, ameliorated M2 receptor dysfunction, and decreased viral content in the lungs without inhibiting virus induced inflammation. High-dose dexamethasone (65 microg/kg i.p.) prevented virus-induced hyperresponsiveness, completely reversed M2 receptor dysfunction, decreased viral titers, and decreased virus-induced inflammation. This high-dose dexamethasone also increased M2 receptor function in uninfected animals. In conclusion, dexamethasone prevented virus-induced hyperresponsiveness and M2 receptor dysfunction via multiple mechanisms.

Activity of cardiorespiratory networks revealed by transsynaptic virus expressing GFP.

A fluorescent transneuronal marker capable of labeling individual neurons in a central network while maintaining their normal physiology would permit functional studies of neurons within entire networks responsible for complex behaviors such as cardiorespiratory reflexes. The Bartha strain of pseudorabies virus (PRV), an attenuated swine alpha herpesvirus, can be used as a transsynaptic marker of neural circuits. Bartha PRV invades neuronal networks in the CNS through peripherally projecting axons, replicates in these parent neurons, and then travels transsynaptically to continue labeling the second- and higher-order neurons in a time-dependent manner. A Bartha PRV mutant that expresses green fluorescent protein (GFP) was used to visualize and record from neurons that determine the vagal motor outflow to the heart. Here we show that Bartha PRV-GFP-labeled neurons retain their normal electrophysiological properties and that the labeled baroreflex pathways that control heart rate are unaltered by the virus. This novel transynaptic virus permits in vitro studies of identified neurons within functionally defined neuronal systems including networks that mediate cardiovascular and respiratory function and interactions. We also demonstrate superior laryngeal motorneurons fire spontaneously and synapse on cardiac vagal neurons in the nucleus ambiguus. This cardiorespiratory pathway provides a neural basis of respiratory sinus arrhythmias.

Herpes simplex replication and dissemination is not increased by corticosteroid treatment in a rat model of focal Herpes encephalitis.

Neurological damage in Herpes simplex type 1 encephalitis results from neuronal cell death secondary to viral invasion, and from inflammatory changes and cerebral oedema secondary to the immune response to the virus. Corticosteroids could have an important role in the management of Herpes simplex encephalitis because their anti-inflammatory action reduces cerebral oedema. However their use has been limited by concerns that their immunosuppressive actions could increase viral replication and spread. The present study examined this issue in a rat model in which injection of HSV-1 into the cervical vagus nerve produced a well-defined focal encephalitis, characterised by an orderly progression of the virus through central neural pathways connected with vagal afferent termination sites in the medulla oblongata. After injection of HSV-1, rats were treated twice a day, either with vehicle (saline, 400 microl i.p.), with acyclovir (30 mg/kg i.p.), with dexamethasone (5 mg/kg i.p.), or with both acyclovir and dexamethasone. Animals were sacrificed after 72 h, and viral load in different brain regions was quantified by computer-assisted measurement of the area occupied by immunohistochemical reaction product. Treatment with acyclovir reduced viral load to 17 +/- 5% of the saline value (P < 0.01). After dexamethasone treatment, the viral load (63 +/- 13% of the saline value) was also reduced (P < 0.05). Treatment with both acyclovir and dexamethasone reduced viral load to 26 +/- 8% of the saline value (P < 0.01 compared with saline, and P > 0.05 compared to acyclovir alone). Our results confirm the effectiveness of acyclovir in a new model of HSV-1 infection, and provide evidence that corticosteroids do not inhibit the antiviral action of acyclovir. In addition corticosteroids may decrease the extent of infection in their own right. The acute time course studied in our model parallels the time course of acute Herpes simplex encephalitis in humans. Our data suggests that corticosteroids are not detrimental when combined with acyclovir in the management of this condition.

Jugular foramen syndrome caused by varicella zoster virus infection in a patient with ipsilateral hypoplasia of the jugular foramen.

We report a patient with acute cranial polyneuropathy with unilateral involvement of the ninth, tenth, and eleventh cranial nerves. Although this patient lacked a typical cutaneous herpetic manifestation, elevated levels of IgM and IgG antibodies to varicella zoster virus (VZV) in both the serum and cerebrospinal fluid confirmed the clinical diagnosis of VZV infection and zoster sine herpete. Coexisting hypoplasia of the ipsilateral jugular foramen was detected using three-dimensional, surface-rendering displays reconstructed from the cranial helical CT scan. The patient recovered almost completely following treatment with an anti-inflammatory corticosteroid. Anatomical narrowing of the jugular foramen in this patient may have contributed to entrapment of the affected nerves at their passage through the foramen.

Retrograde transynaptic pseudorabies virus infection of central autonomic circuits in neonatal rats.

Pseudorabies virus (PRV) is widely used to map synaptically-linked neural circuits in adult animals. The present study sought to determine whether PRV has similar utility in neonatal rats, and whether central PRV infection in neonates elicits astrocytic and microglia/macrophage responses similar to those that contribute to specific transynaptic neuronal infection in adult rats. Retrograde transneuronal infection of autonomic circuits was examined 24-64 h after injection of an attenuated strain of PRV (PRV-Bartha) into the ventral stomach wall of 1-day-old rats. Brain and spinal cord sections were processed for immunocytochemical detection of PRV. Alternate sections were processed for immunolocalization of glial fibrillary acidic protein (GFAP) to identify fibrous astrocytes, or for an antigen associated with the complement C3bi receptor (OX42) to identify microglia. As in adult rats, the number and distribution of infected CNS neurons in neonatal rats increased progressively with advancing post-inoculation survival. Infected CNS neurons initially were restricted to the thoracic intermediolateral cell column and the dorsal motor nucleus of the vagus. Longer survival times led to retrograde transynaptic infection of additional neurons in the thoracic spinal cord, nucleus of the solitary tract, ventrolateral medulla, and caudal raphe nuclei. At the longest post-inoculation intervals, infected neurons also were observed in the area postrema and in certain autonomic-related regions of the rostral brainstem, hypothalamus, and amygdala. Quantitative analysis of immunolabeling in the dorsal vagal complex demonstrated that regions containing neurons at early stages of viral infection displayed increased astrocytic GFAP immunostaining; conversely, areas containing neurons at later stages of infection were characterized by a significant loss of GFAP staining and a parallel increase of OX42 microglia/macrophage immunolabeling. We conclude that PRV is effectively transported through synaptically-linked CNS circuits in neonatal rats, and that spatiotemporally-ordered responses by non-neuronal cells may contribute to the synaptic specificity of transneuronal viral transport.

Herpes simplex virus type I reactivation as a cause of a unilateral temporary paralysis of the vagus nerve.

Infection by neurotropic viruses, as exemplified by the herpes family, is universally accepted as a cause of palsies of the cochleo-vestibular and facial nerve. Palsies of the vagus nerve with a possible viral etiology have been described, although viruses have been identified in only a few selected cases. We report a 52-year-old man with unilateral otalgia, hoarseness and dysphagia. Examination revealed unilateral (left-sided) pharyngeal dysfunction, and paralysis of the left vocal cord fixed in the paramedian position. A barium swallow documented dysfunction of the left pharyngeal constrictor muscles. These findings suggested the lesion to be located either at the inferior ganglion of the vagus nerve or cranially. At direct laryngoscopy a smear was obtained from a 4-mm mucosal ulcer at the region of the left arytenoid cartilage. This smear demonstrated antibodies to herpes simplex virus (HSV) type I by immunofluorescence. On follow-up 19 months after the initial infection there was complete remission of the paralysis of the left vocal cord and normal pharyngeal function. The demonstration of HSV type 1 antibodies from a mucosal lesion in the distribution of the superior laryngeal nerve suggests that reactivation of HSV type I was the most likely explanation for the temporary nerve palsy seen.