Impaired immune responses following spinal cord injury lead to reduced ability to control viral infection

Prolonged intermittent hypoxia differentially regulates phrenic motor neuron serotonin receptor expression in rats following chronic cervical spinal cord injury

Low-dose (< 2 h/day), acute intermittent hypoxia (AIH) elicits multiple forms of serotonin-dependent phrenic motor plasticity and is emerging as a promising therapeutic strategy to restore respiratory and non-respiratory motor function after spinal cord injury (SCI). In contrast, high-dose (> 8 h/day), chronic intermittent hypoxia (CIH) undermines some forms of serotonin-dependent phrenic motor plasticity and elicits pathology. CIH is a hallmark of sleep disordered breathing, which is highly prevalent in individuals with cervical SCI. Interestingly, AIH and CIH preconditioning differentially impact phrenic motor plasticity. Although mechanisms of AIH-induced plasticity in the phrenic motor system are well-described in naïve rats, we know little concerning how these mechanisms are affected by chronic SCI or intermittent hypoxia preconditioning. Thus, in a rat model of chronic, incomplete cervical SCI (lateral spinal hemisection at C2 (C2Hx), we assessed serotonin type 2A, 2B and 7 receptor expression in and near phrenic motor neurons and compared: 1) intact vs. chronically injured rats; and 2) the impact of preconditioning with varied "doses" of intermittent hypoxia (IH). While there were no effects of chronic injury or intermittent hypoxia alone, CIH affected multiple receptors in rats with chronic C2Hx. Specifically, CIH preconditioning (8 h/day; 28 days) increased serotonin 2A and 7 receptor expression exclusively in rats with chronic C2Hx. Understanding the complex, context-specific interactions between chronic SCI and CIH and how this ultimately impacts phrenic motor plasticity is important as we leverage AIH-induced motor plasticity to restore breathing and other non-respiratory motor functions in people with chronic SCI.

"It's been a double-edged sword": An online qualitative exploration of the impact of COVID-19 on individuals with spinal cord injury in the US with comparisons to previous UK findings

OBJECTIVE

The impact of COVID-19 lockdowns and social distancing for persons with spinal cord injury (SCI) are poorly understood. This exploratory online qualitative study collected self-reported COVID-19 experiences from persons with SCI in the United States (US). To enrich understanding, these data were compared to similar previously-published data from a sample of SCI participants from the United Kingdom (UK).

DESIGN

Explorative, online qualitative study. Participants completed an online survey of open-ended qualitative questions pertaining to their experiences during the pandemic. Thematic analysis was utilized to generate themes from the US data. These themes were compared to our previously-published thematic analysis of data from the UK.

SETTING

Community-based sample of persons with SCI in the US.

PARTICIPANTS

Participants were recruited via SCI-focused research registries and social media outlets serving the SCI community, using convenience sampling (n = 36). Key themes identified in the US data were compared to themes identified in a similar sample from the UK (n = 42) collected at the same time and published previously.

RESULTS

Analysis resulted in three themes from the US data, each containing positive and negative qualitative reflections. Themes included (1) health and access to care, (2) making sense of the pandemic, and (3) daily life during the pandemic. Each theme captured common facets of life during the pandemic, often shared by those without physical disabilities, but included accounts particularly relevant to persons with disabilities. Comparisons to thematic findings from the UK study revealed similarities (e.g. healthcare access challenges, isolation) and differences (e.g. importance of previous SCI experiences).

CONCLUSION

We detailed common experiences of COVID-19 pandemic lockdowns and their impact on people with SCI, while contrasting these with sense-making positive reflections and social benefits that appeared to be helpful in managing distress and coping with the pandemic.

A comprehensive look at the psychoneuroimmunoendocrinology of spinal cord injury and its progression: mechanisms and clinical opportunities

Spinal cord injury (SCI) is a devastating and disabling medical condition generally caused by a traumatic event (primary injury). This initial trauma is accompanied by a set of biological mechanisms directed to ameliorate neural damage but also exacerbate initial damage (secondary injury). The alterations that occur in the spinal cord have not only local but also systemic consequences and virtually all organs and tissues of the body incur important changes after SCI, explaining the progression and detrimental consequences related to this condition. Psychoneuroimmunoendocrinology (PNIE) is a growing area of research aiming to integrate and explore the interactions among the different systems that compose the human organism, considering the mind and the body as a whole. The initial traumatic event and the consequent neurological disruption trigger immune, endocrine, and multisystem dysfunction, which in turn affect the patient's psyche and well-being. In the present review, we will explore the most important local and systemic consequences of SCI from a PNIE perspective, defining the changes occurring in each system and how all these mechanisms are interconnected. Finally, potential clinical approaches derived from this knowledge will also be collectively presented with the aim to develop integrative therapies to maximize the clinical management of these patients.

Impact of the COVID-19 pandemic on the quality of life and accessing rehabilitation services among patients with spinal cord injury and their fear of COVID-19

BACKGROUND

The unanticipated coronavirus disease (COVID-19) had a negative effect on the quality of life (QoL) of patients with spinal cord injury (SCI) and made significant changes in their daily routine. Patients with SCI face additional health risks, especially mental, behavioral, and physical. Without regular physiotherapy sessions, patients' psychological and functional abilities can deteriorate, and complications can occur. There is little information available about the impact of COVID-19 on the quality of life of patients with SCI, and their access to rehabilitation services during the pandemic.

OBJECTIVE

This study was designed to examine the effects of the COVID-19 pandemic on the quality of life of patients with SCI and also their fear of COVID-19. The pandemic's impact on the accessibility of rehabilitation services and attendance at physiotherapy sessions in one Chinese hospital were also documented.

DESIGN

An observational study based on an online survey.

SETTING

Outpatients clinic at the rehabilitation department of Wuhan's Tongji Hospital.

PARTICIPANTS

People who had been diagnosed with a spinal cord injury (SCI) and who were receiving regular medical monitoring as outpatients at the rehabilitation department were invited to participate in our study (n = 127).

INTERVENTION

Not applicable.

OUTCOME MEASURES

A 12-Item Short-Form Health Survey (SF-12) designed to measure participants' quality of life before and during the pandemic. Their fear of COVID-19 was quantified using the Fear of COVID-19 Scale (FCV-19S). Demographic and medical status information was extracted from their medical records. Their use of rehabilitation services and attendance at physical therapy sessions was also documented.

RESULTS

Seventy-nine patients with SCI completed the SF-12 and FCV-19 scale. The mental and physical aspects of the participants' quality of life declined significantly, during the epidemic compared to the pre-epidemic period. More than half of the participants have experienced fear of COVID-19 based on FCV-19S. Most received only irregular physical therapy during routine checkups. Worry about virus transmission was the most common cause cited for not attending regular physical therapy sessions.

CONCLUSIONS

The quality of life of these Chinese patients with SCI declined during the pandemic. Most of the participants were shown a high level of fear of COVID-19 and were classified as having an intense fear of COVID-19, in addition to the impact of the pandemic on their access to rehabilitation services and attendance at physical therapy sessions.

Systemic Immune Profile Predicts the Development of Infections in Patients with Spinal Cord Injuries

Patients with spinal cord injury (SCI) frequently develop infections that may affect quality of life, be life-threatening, and impair their neurological recovery in the acute and subacute injury phases. Therefore, identifying patients with SCI at risk for developing infections in this stage is of utmost importance. We determined the systemic levels of immune cell populations, cytokines, chemokines, and growth factors in 81 patients with traumatic SCI at 4 weeks after injury and compared them with those of 26 age-matched healthy control subjects. Patients who developed infections between 4 and 16 weeks after injury exhibited higher numbers of neutrophils and eosinophils, as well as lower numbers of lymphocytes and eotaxin-1 (CCL11) levels. Accordingly, lasso logistic regression showed that incomplete lesions (American Spinal Injury Association Impairment Scale [AIS] C and D grades), the levels of eotaxin-1, and the number of lymphocytes, basophils, and monocytes are predictive of lower odds for infections. On the other hand, the number of neutrophils and eosinophils as well as, in a lesser extent, the levels of IP-10 (CXCL10), MCP-1 (CCL2), BDNF [brain-derived neurotrophic factor], and vascular endothelial growth factor [VEGF]-A, are predictors of increased susceptibility for developing infections. Overall, our results point to systemic immune disbalance after SCI as predictors of infection in a period when infections may greatly interfere with neurological and functional recovery and suggest new pathways and players to further explore novel therapeutic strategies.

Systemic inflammation after spinal cord injury: A review of biological evidence, related health risks, and potential therapies

Individuals with chronic traumatic spinal cord injury (SCI) develop progressive multi-system health problems that result in clinical illness and disability. Systemic inflammation is associated with many of the common medical complications and acquired diseases that accompany chronic SCI, suggesting that it contributes to a number of comorbid pathological conditions. However, many of the mechanisms that promote persistent systemic inflammation and its consequences remain ill-defined. This review describes the significant biological factors that contribute to systemic inflammation, major organ systems affected, health risks, and the potential treatment strategies. We aim to highlight the need for a better understanding of inflammatory processes, and to establish appropriate strategies to address inflammation in SCI.

Effect of the COVID-19 pandemic on individuals with spinal cord injury: Mental health and use of telehealth

INTRODUCTION

Limited access to health care services and the self-isolation measures due to the coronavirus disease 2019 (COVID-19) pandemic may have had additional unintended negative effects, affecting the health of individuals with spinal cord injury (SCI).

OBJECTIVES

To examine the perceived influence of the COVID-19 pandemic on individuals with SCI. First, this study looked to understand how the pandemic affected the use and perception of telehealth services for these individuals. Second, it investigated the effect of COVID-19 on mental health.

DESIGN

Cross-sectional online survey.

SETTING

Individuals with SCI living in the community in British Columbia, Canada.

PATIENTS

This survey was offered to individuals with SCI and had 71 respondents, with 34% living in a rural setting and 66% in an urban setting.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Telehealth utility, Patient Health Questionnaire-9 (PHQ-9), Generalized Anxiety Disorder 7 (GAD-7), Fear of COVID-19 scale (FCV-19S), and Perceived Vulnerability to Disease (PVD).

RESULTS

Telehealth use in the SCI population has increased from 9.9% to 25.4% over the pandemic, with rates of telehealth use in urban centers nearing those of rural participants. Thirty-one percent of respondents had probable depression and 7.0% had probable generalized anxiety disorder as measured by a score of ≥10 on the PHQ-9 and GAD-7, respectively. The mean scores on FCV-19S and PVD were 17.0 (6.6 SD) and 4.29 (1.02 SD), respectively.

CONCLUSION

Telehealth use during COVID-19 has more than doubled. It is generally well regarded by respondents, although only a fourth of the SCI population has reported its use. With this in mind, it is important to understand the barriers to further adoption. In addition, higher rates of probable depression were seen than those estimated by pre-pandemic studies in other countries.

CCR7-mediated T follicular helper cell differentiation is associated with the pathogenesis and immune microenvironment of spinal cord injury-induced immune deficiency syndrome

Spinal cord injury-induced immune deficiency syndrome (SCI-IDS) is a disorder characterized by systemic immunosuppression secondary to SCI that dramatically increases the likelihood of infection and is difficult to treat. T follicular helper (Tfh) cells regulated by chemokine receptor CCR7 are associated with SCI-IDS after acute SCI. The present study explored the roles of CCR7 in SCI-IDS occurrence and immune microenvironment composition. Gene expression profile data of peripheral blood leukocytes from SCI and non-SCI subjects were collected from the Gene Expression Omnibus database. According to differential gene expression analysis, a protein-protein interaction (PPI) network, and risk model construction, the CCR7 expression level was prominently related to acute SCI and CCR7 expression was significantly downregulated after acute SCI. Next, we constructed a clinical prediction model and used it to identify patients with acute SCI. Using Gene Ontology (GO) analysis and gene set enrichment analysis (GSEA), we discovered that immune-related biological processes, such as T cell receptor signaling pathway, were suppressed, whereas chemokine-related signaling pathways were activated after acute SCI. Immune infiltration analysis performed using single sample GSEA and CIBERSORT suggested that Tfh cell function was significantly correlated with the CCR7 expression levels and was considerably reduced after acute SCI. Acute SCI was divided into two subtypes, and we integrated multiple classifiers to analyze and elucidate the immunomodulatory relationships in both subtypes jointly. The results suggested that CCR7 suppresses the immunodeficiency phenotype by activating the chemokine signaling pathway in Tfh cells. In conclusion, CCR7 exhibits potential as a diagnostic marker for acute SCI.

Hyperbaric Oxygen Therapy-Induced Molecular and Pathway Changes in a Rat Model of Spinal Cord Injury: A Proteomic Analysis

Hyperbaric Oxygen Therapy (HBOT) has definitive therapeutic effects on spinal cord injury (SCI), but its mechanism of action is still unclear. Here, we've conducted a systemic proteomic analysis to identify differentially expressed proteins (DEPs) between SCI rats and HBOT + SCI rats. The function clustering analysis showed that the top enriched pathways of DEPs include oxygen transport activity, oxygen binding, and regulation of T cell proliferation. The results of functional and signal pathway analyses indicated that metabolic pathways, thermogenesis, LXR/RXR activation, acute phase response signaling, and the intrinsic prothrombin pathway in the SCI + HBOT group was higher than SCI group.

Barriers to personal hygiene in persons with spinal cord injury during the COVID-19 pandemic and lockdown: A rehabilitation perspective of two cases

Personal hygiene is the most important measure to prevent coronavirus disease 19 (COVID-19). The pandemic has put persons with disabilities into various challenges. People with spinal cord injury (SCI) are facing these obstacles more because of their altered physiology and increased susceptibility to COVID-19. Through telerehabilitation, hurdles were identified in two paraplegic individuals, such as safe water sources, concerns regarding self-catheterization, increased dependence on care partner, hygiene of assistive aids/wheelchairs, availability of dressing materials for pressure injury dressing, and sanitary pads for menstrual hygiene. To the best of our knowledge, these are the first cases to describe hygiene concerns of SCI people during the COVID-19 pandemic and its rehabilitation implications. Considering the population with disabilities, we should improve access to primary care at the community level regarding personal hygiene. For a large population with disabilities such as SCI who are at risk, simple health education, awareness, and economic ways of hygienic practices can be a saviour.

Infections and spinal cord injury: Covid-19 and beyond

Spinal cord injuries cause not only a loss of mobility and sensibility, but also numerous chronic disorders such as: immunosuppression, higher rates of hypertension, neurogenic bladder, blood circulation impairments, and at T8 or above levels of injury, respiratory muscle weakness that can lead to breathing failure. All these conditions make chronic patients susceptible to infections due to a lowered immune system.

The aim of this chapter is to analyze the clinical presentation of Covid-19 in patients with spinal cord injury. The authors pretend to make pause to understand if this emergent disease, which is deadly hitting our general population, behaves in the same way in these special patients, to understand if the spinal cord injury condition is acting as a risk factor for morbidity or not, and why. For this purpose, we want to explore the role that the immune system plays in causing infection in patients with spinal cord injury.

Some spinal cord-injured patients develop a dysregulation of the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis, which negatively affects all immune processes. Therefore, the combination of this situation with other locally impaired conditions provide the suitable environment for developing an infection, as it occurs in urinary tract infections, the most frequent infection in these patients, because of the presence of a neurogenic bladder and the use of catheters to facilitate its voiding; or in pulmonary infections, the severest ones, because of the respiratory muscle weakness, dysphagia disorders, pulmonary edema, and the use of ventilators to assist with breathing. The physiopathology of these infections helps us to understand its appropriate diagnosis, treatment, and methods of prevention.

Most of the published studies show a tendency of milder initial symptoms and a less severe evolution of the Covid-19 disease in spinal cord-injured patients, but currently further validation is needed to support or reject it. The altered immune response could play a critical role in the clinical presentation of these patients. Close observation of neurofunctional outcomes, especially with the help of the International Standards for Neurological Classification of the Spinal Cord Injury (ISNCSCI) Worksheet, is needed to conclude if this infection produces sensory and motor deficits in these patients. Telemedicine has demonstrated to be a useful and effective tool to provide access to medical healthcare to these chronically affected patients, especially under pandemic restriction.

Supplementation With Vitamin E, Zinc, Selenium, and Copper Re-Establishes T-Cell Function and Improves Motor Recovery in a Rat Model of Spinal Cord Injury

Spinal cord injury (SCI) causes a dysfunction of sympathetic nervous system innervation that affects the immune system, leading to immunosuppression syndrome (ISS) and contributing to patient degeneration and increased risk of several infections. A possible therapeutic strategy that could avoid further patient deterioration is the supplementation with Vitamin E or trace elements, such as Zinc, Selenium, and Copper, which individually promotes T-cell differentiation and proliferative responses. For this reason, the aim of the present study was to evaluate whether Vitamin E, Zinc, Selenium, and Copper supplementation preserves the number of T-lymphocytes and improves their proliferative function after traumatic SCI. Sprague–Dawley female rats were subjected to moderate SCI and then randomly allocated into three groups: (1) SCI + supplements; (2) SCI + vehicle (olive oil and phosphate-buffered saline); and (3) sham-operated rats. In all rats, the intervention was initiated 15 min after SCI and then administered daily until the end of study. Locomotor recovery was assessed at 7 and 15 days after SCI. At 15 days after supplementation, the quantification of the number of T-cells and its proliferation function were examined. Our results showed that the SCI + supplements group presented a significant improvement in motor recovery at 7 and 15 days after SCI. In addition, this group showed a better T-cell number and proliferation rate than that observed in the group with SCI + vehicle. Our findings suggest that Vitamin E, Zinc, Selenium, and Copper supplementation could be part of a therapy for patients suffering from acute SCI, helping to preserve T-cell function, avoiding complications, and promoting a better motor recovery. All procedures were approved by the Animal Bioethics and Welfare Committee (Approval No. 201870; CSNBTBIBAJ 090812960).

Chromobacterium violaceum: A Rare Cause of Urinary Tract Infection

A 41-year-old man with a neurogenic bladder due to spinal cord injury (SCI) attended the outpatient department with chief complaints of fever, pain in the lower abdomen, and persistent hematuria for 10 days. From the urine culture and the microbiological and biochemical tests, the causative organism was identified as Chromobacterium violaceum. The isolate was resistant to cephalosporins, while it was sensitive to ofloxacin, gentamicin, and imipenem. Clinicians should be aware of this rare cause of urinary tract infection (UTI), the choice of antibiotic, length of treatment, and necessity of prompt treatment in SCI patients.

Peripheral Immune Dysfunction: A Problem of Central Importance after Spinal Cord Injury

Simple Summary

Spinal cord injury can result in an increased vulnerability to infections, but until recently the biological mechanisms behind this observation were not well defined. Immunosuppression and concurrent sustained peripheral inflammation after spinal cord injury have been observed in preclinical and clinical studies, now termed spinal cord injury-induced immune depression syndrome. Recent research indicates a key instigator of this immune dysfunction is altered sympathetic input to lymphoid organs, such as the spleen, resulting in a wide array of secondary effects that can, in turn, exacerbate immune pathology. In this review, we discuss what we know about immune dysfunction after spinal cord injury, why it occurs, and how we might treat it.

Abstract

Individuals with spinal cord injuries (SCI) exhibit increased susceptibility to infection, with pneumonia consistently ranking as a leading cause of death. Despite this statistic, chronic inflammation and concurrent immune suppression have only recently begun to be explored mechanistically. Investigators have now identified numerous changes that occur in the peripheral immune system post-SCI, including splenic atrophy, reduced circulating lymphocytes, and impaired lymphocyte function. These effects stem from maladaptive changes in the spinal cord after injury, including plasticity within the spinal sympathetic reflex circuit that results in exaggerated sympathetic output in response to peripheral stimulation below injury level. Such pathological activity is particularly evident after a severe high-level injury above thoracic spinal cord segment 6, greatly increasing the risk of the development of sympathetic hyperreflexia and subsequent disrupted regulation of lymphoid organs. Encouragingly, studies have presented evidence for promising therapies, such as modulation of neuroimmune activity, to improve regulation of peripheral immune function. In this review, we summarize recent publications examining (1) how various immune functions and populations are affected, (2) mechanisms behind SCI-induced immune dysfunction, and (3) potential interventions to improve SCI individuals’ immunological function to strengthen resistance to potentially deadly infections.

Absence of αβ T cells accelerates disuse bone loss in male mice after spinal cord injury

Whether T cells promote bone loss following immobilization after spinal cord injury (SCI) remains undetermined. Therefore, wild-type (WT) and T cell-deficient (Tcrb-/- ) male mice underwent sham or contusion SCI to cause hindlimb paralysis. Femurs were isolated and distal and midshaft regions were evaluated by microcomputed tomography scanning. Bone marrow (BM) levels of bone turnover markers, as well as receptor activator of nuclear factor-kappa B ligand (RANKL) and osteoprotegerin (OPG), were measured by ELISA. At 2 weeks post-SCI, immobilization resulted in marked reduction in trabecular fractional bone volume (55%), thickness (40%), connectivity, and cortical thickness only in the Tcrb-/- animals (interaction with P < 0.05). BM analysis revealed lower bone formation (procollagen type 1 intact N-terminal propeptide), higher bone resorption (tartrate-resistant acid phosphatase-5b), and a higher RANKL/OPG ratio in the Tcrb-/- SCI animals. At 5 weeks post-SCI, while both WT and Tcrb-/- paralyzed animals showed deterioration of all indices of bone structure, they were more severe in Tcrb-/- animals. In summary, unlike other skeletal disorders, loss of αβ T cells compromises, rather than preserves, skeletal integrity under conditions of immobilization.

COVID-19 and Spinal Cord Injury: Clinical Presentation, Clinical Course, and Clinical Outcomes: A Rapid Systematic Review

Persons living with spinal cord injury (SCI) are potentially at risk for severe COVID-19 disease given that they often have decreased lung capacity and may lack the ability to effectively evacuate their lungs. Known risk factors for negative outcomes after COVID-19, such as obesity, diabetes, and cardiovascular disease, disproportionally affect people with SCI and raise concerns for the mortality risk among persons with SCI. A rapid systematic review of English, Spanish, Portuguese, and Chinese literature on COVID-19 and SCI was performed using the keywords "spinal cord injury" and "COVID-19." We included studies that provided information on clinical presentation, characteristics, course, and outcomes of COVID-19 disease in SCI. We excluded studies on patients who did not have an SCI before severe acute respiratory syndrome coronavirus-2 infection or did not report clinical information. We included 10 studies in total: nine studies with a total of 171 patients and a survey study of 783 healthcare professionals. Fever (74%), cough (52%), and dyspnea (33%) were the most frequently reported symptoms, and 63% showed abnormalities on X-ray imaging. In the included case series and reports (N = 31), only 1 patient required mechanical ventilation, but 3 patients died (10%). The mortality rate in a large registry study (N = 140) was 19%. Clinical presentation of COVID-19 in SCI patients was similar to the general population, and though adverse events and intensive care unit admission were low, the mortality rate was high (10-19%). No prognostic factors for severe disease or mortality could be identified. Registration (PROSPERO): CRD42020196565.

COVID-19 tsunami: the first case of a spinal cord injury patient in Italy

INTRODUCTION

We present the report of the first, to our best knowledge, case of COVID-19 in a tetraplegic person.

CASE PRESENTATION

A 56-year-old male with AIS A C4 tetraplegia developed fever during the night, without any prodrome. His general practitioner suspected a urinary tract infection and prescribed him antibiotic therapy. After 2 days of antibiotic therapy the fever still persisted, so the individual was admitted to the local hospital and treated with broad-spectrum antibiotics. After 2 days he was transferred to our spinal unit. Considering the worsening of the chest X-ray and fever despite 48 h of broad-spectrum antibiotic therapy, we strongly suspected viral pneumonia. SARS-CoV-2 was detected and antiviral therapy with Lopinavir/Ritonavir, associated with hydroxychloroquine, was promptly started. Fever ceased after 2 days of therapy.

DISCUSSION

Blood test and chest X-ray findings in this patient were similar to previously published findings regarding COVID-19. One difference between this case and the known clinical course of COVID-19 is that did not develop cough. Another interesting feature of our case is that, despite tetraplegia, the clinical course was not severe. Persons with COVID-19 remain asymptomatic, these results underscore the need for rehabilitation and SCI professionals to have a high index of suspicion for COVID-19 in their inpatient and outpatient clients. Only inpatient with fever hase being tested for COVID-19. All new patients are submitted to SARS-COV-2 Test. Moreover, routine testing of patients who have to participate in therapy in common gym areas may be warranted.

Elevated plasma BDNF levels are correlated with NK cell activation in patients with traumatic spinal cord injury

BACKGROUND

The precise role of innate immune responses in the early stage of traumatic spinal cord injury (SCI), especially those mediated by natural killer (NK) cells, is poorly understood.

METHODS

The frequency and phenotype of NK cells from traumatic SCI patients and healthy controls were assessed by flow cytometry. ELISA assay was used to detect the production of a series of cytokines, neurotrophins, and neurohormones in plasma samples. In vitro cell culture was performed to observe brain-derived neurotrophic factor (BDNF)-induced NK cell activation.

RESULTS

A significant increase in the NK cell frequency and the presence of NK cells with the activated phenotype was observed, as reflected by the enhanced expression of CD69, HLA-DR, NKG2D, and NKp30 on the NK cells, in traumatic SCI patients within 24 h of injury, compared to case for the healthy controls. Meanwhile, a higher level of BDNF, a member of the neurotrophin family, was observed in the plasma samples of the SCI patients; the elevated level of BDNF was strongly and positively correlated with the percentage of NK cells during the early stage of traumatic SCI. Furthermore, the expression of CD69 and NKp30 on the NK cells increased following stimulation with BDNF for 24 h in vitro, which is consistent with the in vivo observation in SCI patients.

CONCLUSION

Collectively, our findings demonstrate the activation of NK cells within 24 h after traumatic SCI, and reveal a novel role of BDNF in regulating NK cell activation.

Immunostimulatory functions of adoptively transferred MDSCs in experimental blunt chest trauma

Myeloid-derived suppressor cells (MDSCs) expand during inflammation and exhibit immunomodulatory functions on innate and adaptive immunity. However, their impact on trauma-induced immune responses, characterized by an early pro-inflammatory phase and dysregulated adaptive immunity involving lymphocyte apoptosis, exhaustion and unresponsiveness is less clear. Therefore, we adoptively transferred in vitro-generated MDSCs shortly before experimental blunt chest trauma (TxT). MDSCs preferentially homed into spleen and liver, but were undetectable in the injured lung, although pro-inflammatory mediators transiently increased in the bronchoalveolar lavage (BAL). Surprisingly, MDSC treatment strongly increased splenocyte numbers, however, without altering the percentage of splenic leukocyte populations. T cells of MDSC-treated TxT mice exhibited an activated phenotype characterized by expression of activation markers and elevated proliferative capacity in vitro, which was not accompanied by up-regulated exhaustion markers or unresponsiveness towards in vitro activation. Most importantly, also T cell expansion after staphylococcal enterotoxin B (SEB) stimulation in vivo was unchanged between MDSC-treated or untreated mice. After MDSC transfer, T cells preferentially exhibited a Th1 phenotype, a prerequisite to circumvent post-traumatic infectious complications. Our findings reveal a totally unexpected immunostimulatory role of adoptively transferred MDSCs in TxT and might offer options to interfere with post-traumatic malfunction of the adaptive immune response.

Elevated Autoantibodies in Subacute Human Spinal Cord Injury Are Naturally Occurring Antibodies

Spinal cord injury (SCI) results in long-term neurological and systemic consequences, including antibody-mediated autoimmunity, which has been related to impaired functional recovery. Here we show that autoantibodies that increase at the subacute phase of human SCI, 1 month after lesion, are already present in healthy subjects and directed against non-native proteins rarely present in the normal spinal cord. The increase of these autoantibodies is a fast phenomenon–their levels are already elevated before 5 days after lesion–characteristic of secondary immune responses, further supporting their origin as natural antibodies. By proteomics studies we have identified that the increased autoantibodies are directed against 16 different nervous system and systemic self-antigens related to changes known to occur after SCI, including alterations in neural cell cytoskeleton, metabolism and bone remodeling. Overall, in the context of previous studies, our results offer an explanation to why autoimmunity develops after SCI and identify novel targets involved in SCI pathology that warrant further investigation.

The spleen as a neuroimmune interface after spinal cord injury

Traumatic spinal cord injury (SCI) causes widespread damage to neurons, glia and endothelia located throughout the spinal parenchyma. In response to the injury, resident and blood-derived leukocytes orchestrate an intraspinal inflammatory response that propagates secondary neuropathology and also promotes tissue repair. SCI also negatively affects autonomic control over peripheral immune organs, notably the spleen. The spleen is the largest secondary lymphoid organ in mammals, with major roles in blood filtration and host defense. Splenic function is carefully regulated by neuroendocrine mechanisms that ensure that the immune responses to infection or injury are proportionate to the initiating stimulus, and can be terminated when the stimulus is cleared. After SCI, control over the viscera, including endocrine and lymphoid tissues is lost due to damage to spinal autonomic (sympathetic) circuitry. This review begins by examining the normal structure and function of the spleen including patterns of innervation and the role played by the nervous system in regulating spleen function. We then describe how after SCI, loss of proper neural control over splenic function leads to systems-wide neuropathology, immune suppression and autoimmunity. We conclude by discussing opportunities for targeting the spleen to restore immune homeostasis, reduce morbidity and mortality, and improve functional recovery after SCI.

Impaired CD8 T cell antiviral immunity following acute spinal cord injury

BACKGROUND

Spinal cord injury (SCI) disrupts essential neuroimmune communication, leading to severe immune depression. Previous studies confirmed immune dysfunction in mice with chronic SCI and following high thoracic level injury where sympathetic innervation of the spleen is disrupted. Here, we induced a mid-thoracic injury where integrity of the sympathetic response is maintained and investigated the antiviral T cell response to influenza virus after acute SCI.

METHODS

One week following a contusion SCI at thoracic level T9, mice were infected intranasally with influenza virus. Profiles of immune cell populations were analyzed before infection, and virus-specific CD8 T cell response was analyzed 7 days post-infection.

RESULTS

Following intranasal infection, injured mice had prolonged recovery and significant weight loss. Importantly, expansion and effector functions of virus-specific CD8 T cells were decreased in injured mice. The compromised CD8 T cell response was associated with inflammation and stress responses initiated after injury. Regulatory mechanisms, including increased regulatory T cells (Tregs) and upregulated PD-1/PD-L1, were induced following SCI. Furthermore, we show that increased corticosterone (CORT) levels can inhibit CD8 T cells and that blocking CORT in vivo following SCI enhances CD8 T cell antiviral responses.

CONCLUSIONS

Our results show that mice with mid-thoracic SCI have impaired CD8 T cell function during the acute stage of injury, indicating that impaired antiviral responses occur rapidly following SCI and is not dependent on injury level.

Biochemical events related to glial response in spinal cord injury

Introducción. La lesión de la médula espinal (LME) es un evento devastador con implicaciones físicas, psicológicas y socioeconómicas. En el tejido cercano a la lesión se instauran cambios morfofisiológicos que determinan la recuperación funcional del segmento medular y de los órganos efectores dependientes de los tractos axonales lesionados.Objetivo. Describir los eventos bioquímicos secuenciales más relevantes de la respuesta de las células gliales posterior a la LME.Materiales y métodos. Se realizó una búsqueda de publicaciones científicas de los últimos 18 años en las bases de datos PubMed y ScienceDirect, bajo los términos en inglés spinal cord injury (SCI), SCI pathophysiology, SCI inflammation, microglia in SCI, glial scar y chondroitin sulfate proteoglycans (CSPG).Resultados. Los procesos fisiopatológicos que se producen después de la LME determinan la recuperación neurológica de los pacientes. La activación de las células gliales juega un papel importante, ya que promueve la producción de moléculas bioactivas y la formación de barreras físicas que inhiben la regeneración neural.Conclusión. El conocimiento de los cambios neurobiológicos ocurridos tras la LME permite una mayor comprensión de la fisiopatología y favorece la búsqueda de nuevas alternativas terapéuticas que limiten la progresión de la lesión primaria y que minimicen el daño secundario responsable de la disfunción neurológica.

Impaired toll like receptor-7 and 9 induced immune activation in chronic spinal cord injured patients contributes to immune dysfunction

Reduced immune activation or immunosuppression is seen in patients withneurological diseases. Urinary and respiratory infections mainly manifested as septicemia and pneumonia are the most frequent complications following spinal cord injuries and they account for the majority of deaths. The underlying reason of these losses is believed to arise due to impaired immune responses to pathogens. Here, we hypothesized that susceptibility to infections of chronic spinal cord injured (SCI) patients might be due to impairment in recognition of pathogen associated molecular patterns and subsequently declining innate and adaptive immune responses that lead to immune dysfunction. We tested our hypothesis on healthy and chronic SCI patients with a level of injury above T-6. Donor PBMCs were isolated and stimulated with different toll like receptor ligands and T-cell inducers aiming to investigate whether chronic SCI patients display differential immune activation to multiple innate and adaptive immune cell stimulants. We demonstrate that SCI patients' B-cell and plasmacytoid dendritic cells retain their functionality in response to TLR7 and TLR9 ligand stimulation as they secreted similar levels of IL6 and IFNα. The immune dysfunction is not probably due to impaired T-cell function, since neither CD4⁺ T-cell dependent IFNγ producing cell number nor IL10 producing regulatory T-cells resulted different outcomes in response to PMA-Ionomycin and PHA-LPS stimulation, respectively. We showed that TLR7 dependent IFNγ and IP10 levels and TLR9 mediated APC function reduced substantially in SCI patients compared to healthy subjects. More importantly, IP10 producing monocytes were significantly fewer compared to healthy subjects in response to TLR7 and TLR9 stimulation of SCI PBMCs. When taken together this work implicated that these defects could contribute to persistent complications due to increased susceptibility to infections of chronic SCI patients.

Long-term functional outcome in patients with acquired infections after acute spinal cord injury

OBJECTIVE

To investigate whether prevalent hospital-acquired pneumonia and wound infection affect the clinical long-term outcome after acute traumatic spinal cord injury (SCI).

METHODS

This was a longitudinal cohort study within the prospective multicenter National Spinal Cord Injury Database (Birmingham, Alabama). We screened datasets of 3,834 patients enrolled in 20 trial centers from 1995 to 2005 followed up until 2016. Eligibility criteria were cervical SCI and American Spinal Cord Injury Association impairment scale A, B, and C. Pneumonia or postoperative wound infections (Pn/Wi) acquired during acute medical care/inpatient rehabilitation were analyzed for their association with changes in the motor items of the Functional Independence Measure (FIM_motor) using regression models (primary endpoint 5-year follow-up). Pn/Wi-related mortality was assessed as a secondary endpoint (10-year follow-up).

RESULTS

A total of 1,203 patients met the eligibility criteria. During hospitalization, 564 patients (47%) developed Pn/Wi (pneumonia n = 540; postoperative wound infection n = 11; pneumonia and postoperative wound infection n = 13). Adjusted linear mixed models after multiple imputation revealed that Pn/Wi are significantly associated with lower gain in FIM_motor up to 5 years after SCI (-7.4 points, 95% confidence interval [CI] -11.5 to -3.3). Adjusted Cox regression identified Pn/Wi as a highly significant risk factor for death up to 10 years after SCI (hazard ratio 1.65, 95% CI 1.26 to 2.16).

CONCLUSION

Hospital-acquired Pn/Wi are predictive of propagated disability and mortality after SCI. Pn/Wi qualify as a potent and targetable outcome-modifying factor. Pn/Wi prevention constitutes a viable strategy to protect functional recovery and reduce mortality. Pn/Wi can be considered as rehabilitation confounders in clinical trials.

Spinal Cord Injury Suppresses Cutaneous Inflammation: Implications for Peripheral Wound Healing

People who suffer a traumatic spinal cord injury (SCI) are at increased risk for developing dermatological complications. These conditions increase cost of care, incidence of rehospitalization, and the risk for developing other infections. The consequences of dermatological complications after SCI are likely exacerbated further by post-injury deficits in neural-immune signaling. Indeed, a functional immune system is essential for optimal host defense and tissue repair. Here, we tested the hypothesis that SCI at high spinal levels, which causes systemic immune suppression, would suppress cutaneous inflammation below the level of injury. C57BL/6 mice received an SCI (T3 spinal level) or sham injury; then one day later complete Freund's adjuvant (CFA) was injected subcutaneously below the injury level. Inflammation was quantified by injecting mice with V-Sense, a perfluorocarbon (PFC) tracer that selectively labels macrophages, followed by in vivo imaging. The total radiant efficiency, which is proportional to the number of macrophages, was measured over a 4-day period at the site of CFA injection. Fluorescent in vivo imaging revealed that throughout the analysis period, the macrophage reaction in SCI mice was reduced ∼50% compared with sham-injured mice. Radiant efficiency data were confirmed using magnetic resonance imaging (MRI), and together the data indicate that SCI significantly impairs subcutaneous inflammation. Future studies should determine whether enhancing local inflammation or boosting systemic immune function can improve the rate or efficiency of cutaneous wound healing in individuals with SCI. Doing so also could limit wound infections or secondary complications of impaired healing after SCI.

Multiple organ dysfunction and systemic inflammation after spinal cord injury: a complex relationship

Spinal cord injury (SCI) is a devastating event that results in significant physical disabilities for affected individuals. Apart from local injury within the spinal cord, SCI patients develop a variety of complications characterized by multiple organ dysfunction or failure. These disorders, such as neurogenic pain, depression, lung injury, cardiovascular disease, liver damage, kidney dysfunction, urinary tract infection, and increased susceptibility to pathogen infection, are common in injured patients, hinder functional recovery, and can even be life threatening. Multiple lines of evidence point to pathological connections emanating from the injured spinal cord, post-injury systemic inflammation, and immune suppression as important multifactorial mechanisms underlying post-SCI complications. SCI triggers systemic inflammatory responses marked by increased circulation of immune cells and pro-inflammatory mediators, which result in the infiltration of inflammatory cells into secondary organs and persistence of an inflammatory microenvironment that contributes to organ dysfunction. SCI also induces immune deficiency through immune organ dysfunction, resulting in impaired responsiveness to pathogen infection. In this review, we summarize current evidence demonstrating the relevance of inflammatory conditions and immune suppression in several complications frequently seen following SCI. In addition, we highlight the potential pathways by which inflammatory and immune cues contribute to multiple organ failure and dysfunction and discuss current anti-inflammatory approaches used to alleviate post-SCI complications. A comprehensive review of this literature may provide new insights into therapeutic strategies against complications after SCI by targeting systemic inflammation.

Natural Killer (NK) Cell Functionality after human Spinal Cord Injury (SCI): protocol of a prospective, longitudinal study

Background

Natural killer (NK) cells comprise the main components of lymphocyte-mediated nonspecific immunity. Through their effector function they play a crucial role combating bacterial and viral challenges. They are also thought to be key contributors to the systemic spinal cord injury-induced immune-deficiency syndrome (SCI-IDS). SCI-IDS increases susceptibility to infection and extends to the post-acute and chronic phases after SCI.

Methods and design

The prospective study of NK cell function after traumatic SCI was carried out in two centers in Berlin, Germany. SCI patients and control patients with neurologically silent vertebral fracture also undergoing surgical stabilization were enrolled. Furthermore healthy controls were included to provide reference data. The NK cell function was assessed at 7 (5–9) days, 14 days (11–28) days, and 10 (8–12) weeks post-trauma. Clinical documentation included the American Spinal Injury Association (ASIA) impairment scale (AIS), neurological level of injury, infection status, concomitant injury, and medications. The primary endpoint of the study is CD107a expression by NK cells (cytotoxicity marker) 8–12 weeks following SCI. Secondary endpoints are the NK cell’s TNF-α and IFN-γ production by the NK cells 8–12 weeks following SCI.

Discussion

The protocol of this study was developed to investigate the hypotheses whether i) SCI impairs NK cell function throughout the post-acute and sub-acute phases after SCI and ii) the degree of impairment relates to lesion height and severity. A deeper understanding of the SCI-IDS is crucial to enable strategies for prevention of infections, which are associated with poor neurological outcome and elevated mortality.

Trial registration

DRKS00009855.

Circulating T cell subsets are altered in individuals with chronic spinal cord injury

Traumatic spinal cord injury (SCI) induces changes in the immune system, both acutely and chronically. To better understand changes in the chronic phase of SCI, we performed a prospective, observational study in a research institute and Department of Physical Medicine and Rehabilitation of an academic medical center to examine immune system parameters, including peripheral immune cell populations, in individuals with chronic SCI as compared to uninjured individuals. Here, we describe the relative frequencies of T cell populations in individuals with chronic SCI as compared to uninjured individuals. We show that the frequency of CD3+ and CD3+ CD4+ T cells are decreased in individuals with chronic SCI, although activated (HLA-DR+) CD4+ T cells are elevated in chronic SCI. We also examined regulatory T cells (T_regs), defined as CD3+ CD4+ CD25+ CD127lo and CCR4+, HLA-DR+ or CCR4+ HLA-DR+. To our knowledge, we provide the first evidence that CCR4+, HLA-DR+ or CCR4+ HLA-DR+ T_regs are expanded in individuals with SCI. These data support additional functional studies of T cells isolated from individuals with chronic SCI, where alterations in T cell homeostasis may contribute to immune dysfunction, such as immunity against infections or the persistence of chronic inflammation.

Chronic spinal cord injury attenuates influenza virus-specific antiviral immunity

Background

Individuals suffering from spinal cord injury (SCI) are at higher risk for respiratory-related viral infections such as influenza. In a previous study (Zha et al., J Neuroinflammation 11:65, 2014), we demonstrated that chronic spinal cord injury caused impairment in CD8⁺T cell function with increased expression of the immunosuppressive protein, programmed cell death 1 (PD-1). The present study was undertaken to establish whether chronic SCI-induced immune deficits would affect antiviral immunity directed against primary and secondary infections.

Methods

Six to seven weeks following a SCI contusion at thoracic level T9, mice were infected intranasally with influenza virus. Virus-specific immunity was analyzed at various time points post-infection and compared to uninjured controls.

Results

We report that chronic thoracic SCI impairs the ability of the animals to mount an adequate antiviral immune response. While all uninjured control mice cleared the virus from their lungs by day 10 post-infection, a significant number (approximately 70 %) of chronic SCI mice did not clear the virus and succumbed to infection-induced mortality. This was attributed to severe deficits in both virus-specific antibody production and CD8⁺ T cell response in injured mice after primary infection. We also determined that previously acquired humoral immunity was maintained after spinal cord injury as vaccination against influenza A prior to injury-protected mice from a homologous viral challenge. In contrast, prior immunization did not protect mice from a heterotypic challenge with a different strain of influenza virus.

Conclusions

Taken together, our data demonstrate that chronic SCI attenuates virus-specific humoral and cellular immunity during the establishment of primary response and impairs the development of memory CD8⁺ T cells. In contrast, B cell memory acquired through vaccination prior to SCI is preserved after injury which demonstrates that antigen-specific memory cells are refractory following injury. Our study defines important parameters of the deficits of chronic SCI-induced immune depression during a viral respiratory infection. Our objective is to better understand the mechanisms of spinal cord injury-induced immune depression with the goal of developing more effective therapies and reduce mortality due to complications from influenza and other infections.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0574-y) contains supplementary material, which is available to authorized users.

Spinal cord injury-induced immune deficiency syndrome enhances infection susceptibility dependent on lesion level

Pneumonia is the leading cause of death after acute spinal cord injury and is associated with poor neurological outcome. In contrast to the current understanding, attributing enhanced infection susceptibility solely to the patient's environment and motor dysfunction, we investigate whether a secondary functional neurogenic immune deficiency (spinal cord injury-induced immune deficiency syndrome, SCI-IDS) may account for the enhanced infection susceptibility. We applied a clinically relevant model of experimental induced pneumonia to investigate whether the systemic SCI-IDS is functional sufficient to cause pneumonia dependent on spinal cord injury lesion level and investigated whether findings are mirrored in a large prospective cohort study after human spinal cord injury. In a mouse model of inducible pneumonia, high thoracic lesions that interrupt sympathetic innervation to major immune organs, but not low thoracic lesions, significantly increased bacterial load in lungs. The ability to clear the bacterial load from the lung remained preserved in sham animals. Propagated immune susceptibility depended on injury of central pre-ganglionic but not peripheral postganglionic sympathetic innervation to the spleen. Thoracic spinal cord injury level was confirmed as an independent increased risk factor of pneumonia in patients after motor complete spinal cord injury (odds ratio = 1.35, P < 0.001) independently from mechanical ventilation and preserved sensory function by multiple regression analysis. We present evidence that spinal cord injury directly causes increased risk for bacterial infection in mice as well as in patients. Besides obvious motor and sensory paralysis, spinal cord injury also induces a functional SCI-IDS ('immune paralysis'), sufficient to propagate clinically relevant infection in an injury level dependent manner.

Lower response to early T-cell-dependent vaccination after neurotrauma or neurosurgery in adults

BACKGROUND

Recent international guidelines recommend vaccination with a 13-valent pneumococcal conjugate vaccine to reduce the risk of meningitis after neurotrauma with cerebrospinal fluid leak. The antibody response and optimal time point for vaccination have not been established and because the risk of meningitis is at the highest shortly after trauma, early vaccination is preferable. This study aimed to investigate the antibody response and to ensure that central nervous system injury-induced immunodepression did not affect the response to a T-cell-dependent conjugate vaccine when administered shortly after the injury.

METHODS

So as not to interfere with routine pneumococcal vaccination, a conjugate vaccine against Haemophilus influenza type b (Hib) was chosen for the study. Thirty-three patients with basilar skull fracture and 23 patients undergoing transsphenoidal pituitary gland surgery were vaccinated within 10 days after trauma/surgery and 29 control patients at least three weeks after trauma/surgery. Sera were collected pre- and post-vaccination for analysis of anti-Hib concentration.

RESULTS

Four patients with post-vaccination target antibody concentration before vaccination were excluded from analysis. In the neurotrauma and neurosurgery groups 10/32 (31%) and 5/20 (25%) patients, respectively, were non-responders compared with 3/29 (10%) in the control group. Log10 anti-Hib concentrations in the neurotrauma, neurosurgery and control groups were 1.52 ± 0.15, 1.38 ± 0.15 and 1.81 ± 0.12 μg/ml, respectively.

CONCLUSIONS

The majority of the patients responded to vaccination. However, the number of responders was significantly decreased and antibody concentration significantly lower in patients vaccinated early after the trauma/surgery. Investigation of the pneumococcal conjugate vaccine response in neurotrauma patients is therefore urgent.

Immune dysfunction and chronic inflammation following spinal cord injury

STUDY DESIGN

Review article.

OBJECTIVES

The objective of this study is to provide an overview of the many factors that contribute to the chronic inflammatory state typically observed following spinal cord injury (SCI).

METHODS

Literature review.

RESULTS

Not applicable.

CONCLUSION

SCI is typically characterized by a low-grade inflammatory state due to a number of factors. As bidirectional communication exists between the nervous, endocrine and immune systems, damage to the spinal cord may translate into both endocrinal and immune impairment. Damage to the autonomic nervous system may induce immune dysfunction directly, through the loss of neural innervation of lymphoid organs, or indirectly by inducing endocrinal impairment. In addition, damage to the somatic nervous system and the corresponding loss of motor and sensory function increases the likelihood of developing a number of secondary health complications and metabolic disorders associated with a state of inflammation. Lastly, numerous related disorders associated with a state of chronic inflammation have been found to be at a substantially higher prevalence following SCI. Together, such factors help explain the chronic inflammatory state and immune impairment typically observed following SCI. An understanding of the interactions between systems, both in health and disease, and the many causes of chronic inflammation may aid in the effective future treatment of immune dysfunction and related disorders following SCI.

Spinal cord injury impacts B cell production, homeostasis, and activation

Complex interactions govern the interplay of central nervous and immune systems, including the generation, homeostatic maintenance, and activation of B cells. Accordingly, spinal cord injury will likely impact all of these processes. Several laboratories have recently explored this possibility, and their observations in aggregate reveal both acute and chronic consequences that can vary based on the injury location. Acute effects include a transient cessation of bone marrow B lymphopoiesis, with a corresponding drop in the peripheral follicular and transitional B cell subsets, whereas the marginal zone subset is preserved. Despite recovery of B lymphopoiesis by 28 days post injury, follicular B cell numbers remain depressed; this may reflect reduced levels of the homeostatic cytokine BLyS. In general, the ability to mount T dependent antibody responses after injury are intact, as are pre-existing memory B cell pools and antibody levels. In contrast, T-independent responses are chronically compromised. Both glucocorticoid-dependent and -independent processes mediate these effects, but a detailed understanding of the mechanisms involved awaits further study. Nonetheless, these observations in toto strengthen the growing appreciation for bidirectional interactions between the CNS and immune system, highlighting the need for further basic and translational efforts.

Spinal cord injury, immunodepression, and antigenic challenge

The inability to effectively control microbial infection is a leading cause of morbidity and mortality in individuals affected by spinal cord injury (SCI). Available evidence from clinical studies as well as animal models of SCI demonstrate that increased susceptibility to infection is derived from disruption of central nervous system (CNS) communication with the host immune system that ultimately leads to immunodepression. Understanding the molecular and cellular mechanisms governing muted cellular and humoral responses that occur post-injury resulting in impaired host defense following infection is critical for improving the overall quality of life of individuals with SCI. This review focuses on studies performed using preclinical animal models of SCI to evaluate how injury impacts T and B lymphocyte responses following either viral infection or antigenic challenge.

Chronic thoracic spinal cord injury impairs CD8+ T-cell function by up-regulating programmed cell death-1 expression

Background

Chronic spinal cord injury (SCI) induces immune depression in patients, which contributes to their higher risk of developing infections. While defects in humoral immunity have been reported, complications in T-cell immunity during the chronic phase of SCI have not yet been explored.

Methods

To assess the impact of chronic SCI on peripheral T-cell number and function we used a mouse model of severe spinal cord contusion at thoracic level T9 and performed flow cytometry analysis on the spleen for T-cell markers along with intracellular cytokine staining. Furthermore we identified alterations in sympathetic activity in the spleen of chronic SCI mice by measuring splenic levels of tyrosine hydroxylase (TH) and norepinephrine (NE). To gain insight into the neurogenic mechanism leading to T-cell dysfunction we performed in vitro NE stimulation of T-cells followed by flow cytometry analysis for T-cell exhaustion marker.

Results

Chronic SCI impaired both CD4⁺ and CD8⁺ T-cell cytokine production. The observed T-cell dysfunction correlated with increased expression of programmed cell death 1 (PD-1) exhaustion marker on these cells. Blocking PD-1 signaling in vitro restored the CD8⁺ T-cell functional defect. In addition, we showed that chronic SCI mice had higher levels of splenic NE, which contributed to the T-cell exhaustion phenotype, as PD-1 expression on both CD4⁺ and CD8⁺ T-cells was up-regulated following sustained exposure to NE in vitro.

Conclusions

These studies indicate that alteration of sympathetic activity following chronic SCI induces CD8⁺ T-cell exhaustion, which in turn impairs T-cell function and contributes to immune depression. Inhibition of the exhaustion pathway should be considered as a new therapeutic strategy for chronic SCI-induced immune depression.

The SCIentinel study--prospective multicenter study to define the spinal cord injury-induced immune depression syndrome (SCI-IDS)--study protocol and interim feasibility data

Background

Infections are the leading cause of death in the acute phase following spinal cord injury and qualify as independent risk factor for poor neurological outcome (“disease modifying factor”). The enhanced susceptibility for infections is not stringently explained by the increased risk of aspiration in tetraplegic patients, neurogenic bladder dysfunction, or by high-dose methylprednisolone treatment. Experimental and clinical pilot data suggest that spinal cord injury disrupts the balanced interplay between the central nervous system and the immune system. The primary hypothesis is that the Spinal Cord Injury-induced Immune Depression Syndrome (SCI-IDS) is 'neurogenic’ including deactivation of adaptive and innate immunity with decreased HLA-DR expression on monocytes as a key surrogate parameter. Secondary hypotheses are that the Immune Depression Syndrome is i) injury level- and ii) severity-dependent, iii) triggers transient lymphopenia, and iv) causes qualitative functional leukocyte deficits, which may endure the post-acute phase after spinal cord injury.

Methods/Design

SCIentinel is a prospective, international, multicenter study aiming to recruit about 118 patients with acute spinal cord injury or control patients with acute vertebral fracture without neurological deficits scheduled for spinal surgery. The assessment points are: i) <31 hours, ii) 31–55 hours, iii) 7 days, iv) 14 days, and v) 10 weeks post-trauma. Assessment includes infections, concomitant injury, medication and neurological classification using American Spinal Injury Association impairment scale (AIS) and neurological level. Laboratory analyses comprise haematological profiling, immunophenotyping, including HLA-DR expression on monocytes, cytokines and gene expression of immune modulators. We provide an administrative interim analysis of the recruitment schedule of the trial.

Discussion

The objectives are to characterize the dysfunction of the innate and adaptive immune system after spinal cord injury and to explore its proposed 'neurogenic’ origin by analyzing its correlation with lesion height and severity. The trial protocol considers difficulties of enrolment in an acute setting, and loss to follow up. The administrative interim analysis confirmed the feasibility of the protocol. Better understanding of the SCI-IDS is crucial to reduce co-morbidities and thereby to attenuate the impact of disease modifying factors to protect neurological “outcome at risk”. This putatively results in improved spinal cord injury medical care.

Trial registration

DRKS-ID: DRKS00000122 (German Clinical Trials Registry)

The immunological response to spinal cord injury: helpful or harmful?

The role of the immune response in spinal cord injury has become a frequent object of debate. Evidence exists to suggest that autoimmunity following neurotrauma can be either beneficial or detrimental to recovery. The following commentary examines the recent findings indicating that mice lacking mature B- and T-lymphocytes have improved behavioral and histological outcomes following thoracic spinal cord injury. These data, presented in the October issue of Experimental Neurology are discussed within the context of previous findings and differing viewpoints in the field of neuroimmunology. Limitations on the translation of immune modulation therapeutics, and clinical perspectives on their future potential are also examined.

Functional neurological recovery after spinal cord injury is impaired in patients with infections

Infections are a common threat to patients after spinal cord injury. Furthermore, infections might propagate neuronal death, and consequently contribute to the restriction of neurological recovery. We investigated the association of infections (i.e. pneumonia and/or postoperative wound infections) with functional neurological outcome after acute severe traumatic spinal cord injury. We screened data sets of 24 762 patients enrolled in a prospective cohort study (National Spinal Cord Injury Database, Birmingham, AL, USA). Patients were assessed according to the ASIA classification. ASIA impairment scale-classified A and B patients recruited within 24 h post-trauma (n = 1436) were selected as being a major recruitment population for interventional trials. Patients with documented pneumonia and/or postoperative wound infections (n = 581) were compared with control subjects (non-documented infections, n = 855). The functional neurological outcome parameters (i) upward ASIA impairment scale conversions; (ii) gain of ASIA motor scores; and (iii) gain of motor and sensory levels were consecutively analysed over time up to 1 year after spinal cord injury. The group with pneumonia and/or postoperative wound infections revealed less ASIA impairment scale upward conversions after 1 year than the control group (ASIA impairment scale A: 17.2 versus 23.9%, P = 0.03; ASIA impairment scale B: 57.1 versus 74.7%, P = 0.009). ASIA motor score gain [median (interquartile range)] was lower in patients with infections [ASIA impairment scale A: 8 (4-12) versus 10 (5-17), P = 0.01; ASIA impairment scale B: 19.5 (8-53.5) versus 42 (20.5-64), P = 0.03)]. Analysis of acquired motor/sensory levels supported these findings. In ASIA impairment scale A patients, the gain in motor levels (21.7 versus 33.3%, P = 0.04) and sensory levels (24.4 versus 38 of 102, 37.3%, P = 0.03) was significantly lower in the group with pneumonia and/or postoperative wound infections than in the control group. Multiple regression analysis identified pneumonia and/or postoperative wound infections as independent risk factors for impaired ASIA impairment scale upward conversion (odds ratio: 1.89, 95% confidence interval: 1.36-2.63, P < 0.0005) or lower gain in ASIA motor score (regression coefficient: -8.21, 95% confidence interval: -12.29 to -4.14, P < 0.0005). Infections associated with spinal cord injury, such as pneumonia and/or postoperative wound infections, qualify as independent risk factors for poor neurological outcome after motor complete spinal cord injury. Infections constitute a clinically relevant target for protecting the limited endogenous functional regeneration capacity. Upcoming interventional trials might gain in efficacy with improved patient stratification and might benefit from complementary protection of the intrinsic recovery potential after spinal cord injury.

Chronic spinal cord injury impairs primary antibody responses but spares existing humoral immunity in mice

Spinal cord injury (SCI) results in immune depression. To better understand how injury inhibits humoral immunity, the effects of chronic thoracic SCI on B cell development and immune responses to thymus-independent type 2 and thymus-dependent Ags were determined. Mice received complete crush injury or control laminectomy at either thoracic level 3, which disrupts descending autonomic control of the spleen, or at thoracic level 9, which conserves most splenic sympathetic activity. Although mature B cell numbers were only mildly reduced, bone marrow B cell production was transiently but profoundly depressed immediately after injury. Despite the return of normal B cell production 4 wk after SCI, mice receiving thoracic level 3 injury showed a significant reduction in their ability to mount primary thymus-independent type 2 or thymus-dependent immune responses. The latter were marked by decreases in germinal center B cells as well as class-switched high-affinity Ab-secreting cells. Importantly, injury did not affect affinity maturation per se, pre-existing B cell memory, or secondary humoral immune responses. Taken together, these findings show that chronic high thoracic SCI impairs the ability to mount optimal Ab responses to new antigenic challenges, but spares previously established humoral immunity.

Additive effects of exogenous IL-12 supplementation and antibiotic treatment in infection prophylaxis

The increasing clinical incidence and host risk of open fracture-associated infections, as well as the reduced effectiveness of conventional antibiotics to treat such infections, have driven the development of new therapies for the prophylaxis of open fracture-associated infections. We investigated percutaneous supplementation of a natural cytokine (i.e., interleukin 12p70 or IL-12) at an open fracture site to reduce open fracture-associated infections. We also determined the efficacy of the combination therapy of IL-12 and conventional antibiotic therapy in the prophylaxis of open fracture-associated infections. An open femur fracture infection model was produced by direct inoculation of a clinical isolate of Staphylococcus aureus after creating a femur fracture using rats. The animals were assigned to one of four groups: no drug administration, percutaneous supplementation of IL-12, intraperitoneal administration of the antibiotic ampicillin, or percutaneous IL-12 in combination with intraperitoneal ampicillin. Animals were euthanized at postoperative days 6, 10, 14, and 21. Percutaneous IL-12 led to a reduction in infection at postoperative days 6 and 10. For the first time, exogenous IL-12 was found to have additive effects in the prevention of infection when combined with conventional treatment (i.e., antibiotic therapy). Combination therapy of ampicillin and IL-12 substantially reduced the infection rate at postoperative day 6 and also decreased the time needed for complete inhibition of infection. Therefore, exogenous IL-12, providing a mechanism of protection independent of antibiotic resistance, complements the routine use of antibiotics.

Molecular Mechanisms and Consequences of Immune and Nervous System Interactions

This chapter provides an overview on the multiple mechanisms by which the nervous system regulates and directs immune function towards what is needed and tolerated by the nervous system. The immune system plays two essential roles necessary for the survival of complex organisms, including tissue homeostasis and tissue defense against pathogens. These immune functions are essential to maintain the func­tions of all organs in the body and are studied as a part of the general field of immunology. The immune system is divided into two arms: a rapid “innate” immune response system and a slow “adaptive” immune response system. The receptors for the types of “alarm” signals detected by the innate immune system are preformed and stably encoded in the genome. By contrast, the receptors for the types of signals that trigger the adaptive immune system are in part stochastically generated and in part shaped by the types and frequency of the pathogens encountered.

Incidence of acute hepatitis B in patients with spinal cord injury

STUDY DESIGN

Retrospective case survey.

OBJECTIVE

To examine incidence and clinical characteristics of hepatitis B infection in individuals with spinal cord injury (SCI).

SETTING

Inpatient clinic within a physical medicine and rehabilitation hospital specialized in rehabilitation.

PARTICIPANTS

A total of 161 patients with SCI.

INTERVENTIONS

Patients' records were investigated and the status of hepatitis B surface antigen (HBsAg), anti-hepatitis C virus (HCV), anti-hepatitis B surface antigen positivity, alanine aminotransferase levels, duration of hospitalization and cost were recorded.

MAIN OUTCOME MEASURES

Incidence of acute hepatitis B.

RESULTS

Six patients were diagnosed with acute hepatitis B on the first hospitalization for rehabilitation. A total of 11 patients (4.2%) were HBsAg positive with a previously established diagnosis of hepatitis B virus infection, 1 patient (0.4%) was anti-HCV positive. After a follow-up of 6 months, three of the acute hepatitis B patients progressed into chronic hepatitis B stage. In acute hepatitis B patients' initiation of the rehabilitation was delayed, duration of hospitalization was increased.

CONCLUSIONS

After SCI, patients are at high risk of acute hepatitis B infection. A high rate of chronicity may be associated with impaired immune response, secondary to neurological deficit. Screening and vaccination protocols may prevent the spread of the hepatitis B infection, healthcare losses and financial loss.