Combined effect of BCG vaccination and enriched environment promote neurogenesis and spatial cognition via a shift in meningeal macrophage M2 polarization

The Neuroprotective Role of BCG Vaccine in Movement Disorders: A Review

Bacillus Calmette-Guérin (BCG) is the first developed vaccine to prevent tuberculosis (TB) and is the world's most widely used vaccine. It has a reconcilable defense in opposition to tuberculosis, meningitis, and miliary disease in children but changeable protection against pulmonary TB. Immune activation is responsible for regulating neural development by activating it. The effect of the BCG vaccine on neuronal disorders due to subordinate immune provocation is useful. BCG vaccine can prevent neuronal degeneration in different neurological disorders by provoking auto-reactive T-cells. In the case of TB, CD4+ T-cells effectively protect the immune response by protecting the central defense. Because of the preceding fact, BCG induces protection by creating precise T-cells like CD4+ T-cells and CD8+ T-cells. Hence, vaccination-induced protection generates specific T-cells and CD4+ T-cells, and CD8+ T-cells. The BCG vaccine may have an essential effect on motor disorders and play a crucial role in neuroprotective management. The present review describes how the BCG vaccine might be interrelated with motor disorders and play a key role in such diseases.

VEGF-A in serum protects against memory impairment in APP/PS1 transgenic mice by blocking neutrophil infiltration

Activation of innate immunity in the brain is a prominent feature of Alzheimer's disease (AD). The present study investigated the regulation of innate immunity by wild-type serum injection in a transgenic AD mouse model. We found that treatment with wild-type mouse serum significantly reduced the number of neutrophils and microglial reactivity in the brains of APP/PS1 mice. Mimicking this effect, neutrophil depletion via Ly6G neutralizing antibodies resulted in improvements in AD brain functions. Serum proteomic analysis identified vascular endothelial growth factor-A (VEGF-A) and chemokine (C-X-C motif) ligand 1 (CXCL1) as factors enriched in serum samples, which are crucial for neutrophil migration and chemotaxis, leukocyte migration, and cell chemotaxis. Exogenous VEGF-A reversed amyloid β (Aβ)-induced decreases in cyclin-dependent kinase 5 (Cdk5) and increases in CXCL1 in vitro and blocked neutrophil infiltration into the AD brain. Endothelial Cdk5 overexpression conferred an inhibitory effect on CXCL1 and neutrophil infiltration, thereby restoring memory abilities in APP/PS1 mice. Our findings uncover a previously unknown link between blood-derived VEGF signaling and neutrophil infiltration and support targeting endothelial Cdk5 signaling as a potential therapeutic strategy for AD.

Can COVID-19 Vaccines Induce Premature Non-Communicable Diseases: Where Are We Heading to?

According to the WHO, as of January 2023, more than 850 million cases and over 6.6 million deaths from COVID-19 have been reported worldwide. Currently, the death rate has been reduced due to the decreased pathogenicity of new SARS-CoV-2 variants, but the major factor in the reduced death rates is the administration of more than 12.8 billion vaccine doses globally. While the COVID-19 vaccines are saving lives, serious side effects have been reported after vaccinations for several premature non-communicable diseases (NCDs). However, the reported adverse events are low in number. The scientific community must investigate the entire spectrum of COVID-19-vaccine-induced complications so that necessary safety measures can be taken, and current vaccines can be re-engineered to avoid or minimize their side effects. We describe in depth severe adverse events for premature metabolic, mental, and neurological disorders; cardiovascular, renal, and autoimmune diseases, and reproductive health issues detected after COVID-19 vaccinations and whether these are causal or incidental. In any case, it has become clear that the benefits of vaccinations outweigh the risks by a large margin. However, pre-existing conditions in vaccinated individuals need to be taken into account in the prevention and treatment of adverse events.

COVID-19 vaccination may enhance hippocampal neurogenesis in adults

Emerging evidence suggests a detrimental impact of COVID-19 illness on the continued hippocampal neurogenesis in adults. In contrast, the existing literature supports an enhancing effect of COVID-19 vaccination on adult hippocampal neurogenesis. Vaccines against respiratory infections, including influenza, have been shown to enhance hippocampal neurogenesis in adult-age animals. We propose that a similar benefit may happen in COVID-19 vaccinated adults. The vaccine-induced enhancement of the hippocampal neurogenesis in adults thus may protect against age-related cognitive decline and mental disorders. It alsohints at an added mental health benefit of the COVID-19 vaccination programs in adults.

Improvement of cognitive function in wild-type and Alzheimer´s disease mouse models by the immunomodulatory properties of menthol inhalation or by depletion of T regulatory cells

A complex network of interactions exists between the olfactory, immune and central nervous systems. In this work we intend to investigate this connection through the use of an immunostimulatory odorant like menthol, analyzing its impact on the immune system and the cognitive capacity in healthy and Alzheimer's Disease Mouse Models. We first found that repeated short exposures to menthol odor enhanced the immune response against ovalbumin immunization. Menthol inhalation also improved the cognitive capacity of immunocompetent mice but not in immunodeficient NSG mice, which exhibited very poor fear-conditioning. This improvement was associated with a downregulation of IL-1β and IL-6 mRNA in the brain´s prefrontal cortex, and it was impaired by anosmia induction with methimazole. Exposure to menthol for 6 months (1 week per month) prevented the cognitive impairment observed in the APP/PS1 mouse model of Alzheimer. Besides, this improvement was also observed by the depletion or inhibition of T regulatory cells. Treg depletion also improved the cognitive capacity of the APP^{NL-G-F/NL-G-F} Alzheimer´s mouse model. In all cases, the improvement in learning capacity was associated with a downregulation of IL-1β mRNA. Blockade of the IL-1 receptor with anakinra resulted in a significant increase in cognitive capacity in healthy mice as well as in the APP/PS1 model of Alzheimer´s disease. These data suggest an association between the immunomodulatory capacity of smells and their impact on the cognitive functions of the animals, highlighting the potential of odors and immune modulators as therapeutic agents for CNS-related diseases.

Dynamics and immunomodulation of cognitive deficits and behavioral changes in non-severe experimental malaria

Data recently reported by our group indicate that stimulation with a pool of immunogens capable of eliciting type 2 immune responses can restore the cognitive and behavioral dysfunctions recorded after a single episode of non-severe rodent malaria caused by Plasmodium berghei ANKA. Here we explored the hypothesis that isolated immunization with one of the type 2 immune response-inducing immunogens, the human diphtheria-tetanus (dT) vaccine, may revert damages associated with malaria. To investigate this possibility, we studied the dynamics of cognitive deficits and anxiety-like phenotype following non-severe experimental malaria and evaluated the effects of immunization with both dT and of a pool of type 2 immune stimuli in reversing these impairments. Locomotor activity and long-term memory deficits were assessed through the open field test (OFT) and novel object recognition task (NORT), while the anxiety-like phenotype was assessed by OFT and light/dark task (LDT). Our results indicate that poor performance in cognitive-behavioral tests can be detected as early as the 12^th day after the end of antimalarial treatment with chloroquine and may persist for up to 155 days post infection. The single immunization strategy with the human dT vaccine showed promise in reversal of long-term memory deficits in NORT, and anxiety-like behavior in OFT and LDT.

Microglia in depression: an overview of microglia in the pathogenesis and treatment of depression

Major depressive disorder is a highly debilitating psychiatric disorder involving the dysfunction of different cell types in the brain. Microglia are the predominant resident immune cells in the brain and exhibit a critical role in depression. Recent studies have suggested that depression can be regarded as a microglial disease. Microglia regulate inflammation, synaptic plasticity, and the formation of neural networks, all of which affect depression. In this review, we highlighted the role of microglia in the pathology of depression. First, we described microglial activation in animal models and clinically depressed patients. Second, we emphasized the possible mechanisms by which microglia recognize depression-associated stress and regulate conditions. Third, we described how antidepressants (clinical medicines and natural products) affect microglial activation. Thus, this review aimed to objectively analyze the role of microglia in depression and focus on potential antidepressants. These data suggested that regulation of microglial actions might be a novel therapeutic strategy to counteract the adverse effects of devastating mental disorders.

Environmental eustress improves postinfarction cardiac repair via enhancing cardiac macrophage survival

Macrophages play a vital role in cardiac repair following myocardial infarction (MI). An enriched environment (EE) is involved in the regulation of macrophage-related activities and disease progression; however, whether EE affects the phenotype and function of macrophages to improve postinfarction cardiac repair remains unknown. In this study, we found that EE improved cardiac function, decreased mortality, and ameliorated adverse ventricular remodeling in mice after MI, with these outcomes closely related to the increased survival of Ly6C^low macrophages and their CCR2^-MHCII^low subsets. EE increased the expression of brain-derived neurotrophic factor (BDNF) in the hypothalamus, leading to higher circulating levels of BDNF, which, in turn, regulated the cardiac macrophages. BDNF bound to tropomyosin receptor kinase B to activate downstream ERK1/2 and AKT pathways, promoting macrophage survival. These findings demonstrate that EE optimizes postinfarction cardiac repair and highlights the significance of EE as a previously unidentified strategy for impeding adverse ventricular remodeling.

Understanding the Role of the Gut Microbiome in Brain Development and Its Association With Neurodevelopmental Psychiatric Disorders

The gut microbiome has a tremendous influence on human physiology, including the nervous system. During fetal development, the initial colonization of the microbiome coincides with the development of the nervous system in a timely, coordinated manner. Emerging studies suggest an active involvement of the microbiome and its metabolic by-products in regulating early brain development. However, any disruption during this early developmental process can negatively impact brain functionality, leading to a range of neurodevelopment and neuropsychiatric disorders (NPD). In this review, we summarize recent evidence as to how the gut microbiome can influence the process of early human brain development and its association with major neurodevelopmental psychiatric disorders such as autism spectrum disorders, attention-deficit hyperactivity disorder, and schizophrenia. Further, we discuss how gut microbiome alterations can also play a role in inducing drug resistance in the affected individuals. We propose a model that establishes a direct link of microbiome dysbiosis with the exacerbated inflammatory state, leading to functional brain deficits associated with NPD. Based on the existing research, we discuss a framework whereby early diet intervention can boost mental wellness in the affected subjects and call for further research for a better understanding of mechanisms that govern the gut-brain axis may lead to novel approaches to the study of the pathophysiology and treatment of neuropsychiatric disorders.

Malaria Related Neurocognitive Deficits and Behavioral Alterations

Typical of tropical and subtropical regions, malaria is caused by protozoa of the genus Plasmodium and is, still today, despite all efforts and advances in controlling the disease, a major issue of public health. Its clinical course can present either as the classic episodes of fever, sweating, chills and headache or as nonspecific symptoms of acute febrile syndromes and may evolve to severe forms. Survivors of cerebral malaria, the most severe and lethal complication of the disease, might develop neurological, cognitive and behavioral sequelae. This overview discusses the neurocognitive deficits and behavioral alterations resulting from human naturally acquired infections and murine experimental models of malaria. We highlighted recent reports of cognitive and behavioral sequelae of non-severe malaria, the most prevalent clinical form of the disease worldwide. These sequelae have gained more attention in recent years and therapies for them are required and demand advances in the understanding of neuropathogenesis. Recent studies using experimental murine models point to immunomodulation as a potential approach to prevent or revert neurocognitive sequelae of malaria.

Efficacy of BCG vaccine in animal models of neurological disorders

The Bacillus Calmette-Guerin (BCG) vaccine can modulate the immune response via antigen-specific immune response, but also it can confer nonspecific protection and therapeutic benefits in several neurological conditions through different heterologous effects of vaccination. However, the precise mechanism of action of BCG remains unclear. In this review, different mechanisms underlying BCG-mediated immunity will be explained in animal models that reflects characteristic feature of neuroinflammatory and neurodegenerative disorders such as multiple sclerosis, Alzheimer's and Parkinson's diseases. Furthermore, evidence for a beneficial effect of the BCG on neuropsychiatric disorders, will be also discussed.

Immune system challenge improves recognition memory and reverses malaria-induced cognitive impairment in mice

The immune system plays a role in the maintenance of healthy neurocognitive function. Different patterns of immune response triggered by distinct stimuli may affect nervous functions through regulatory or deregulatory signals, depending on the properties of the exogenous immunogens. Here, we investigate the effect of immune stimulation on cognitive-behavioural parameters in healthy mice and its impact on cognitive sequelae resulting from non-severe experimental malaria. We show that immune modulation induced by a specific combination of immune stimuli that induce a type 2 immune response can enhance long-term recognition memory in healthy adult mice subjected to novel object recognition task (NORT) and reverse a lack of recognition ability in NORT and anxiety-like behaviour in a light/dark task that result from a single episode of mild Plasmodium berghei ANKA malaria. Our findings suggest a potential use of immunogens for boosting and recovering recognition memory that may be impaired by chronic and infectious diseases and by the effects of ageing.

Cyclosporin A impairs neurogenesis and cognitive abilities in brain development via the IFN-γ-Shh-BDNF pathway

A wealth of evidence indicate that the peripheral immune activation alters brain development. However, it is still largely unclear whether and how peripheral immunosuppression affects neurodevelopment. Here, we found that the immunosuppressant cyclosporin A (CsA) decreased the number of BrdU+, BrdU+/DCX+, BrdU+/NeuN + cells in the hippocampus, impaired learning and memory and inhibited protein levels of the shh signaling pathway, including Shh, Smo and Gli1. However, the shh pathway receptor agonist SAG could block the impairment of cognitive ability and the decrease of hippocampal neurogenesis and brain-derived neurotrophic factor (BDNF) level induced by CsA. We also found that CsA decreased the level of interferon-gamma (IFN-γ), while up-regulation of IFN-γ altered the inhibitory effect of the shh signaling pathway and the decrease of BDNF induced by CsA. Collectively, these data indicate that peripheral CsA impairs neurogenesis and cognition in brain development through downregulating the IFN-γ-Shh-BDNF pathway. The present study guides us to correctly apply immunomodulatory drugs in early life and suggests that the IFN-γ-Shh-BDNF pathway may represent a novel protective target for neurodevelopment under the condition of immunosuppression.

Bladder Cancer Immunotherapy by BCG Is Associated with a Significantly Reduced Risk of Alzheimer's Disease and Parkinson's Disease

Bacillus Calmette–Guerin (BCG) is a live attenuated form of Mycobacterium bovis that was developed 100 years ago as a vaccine against tuberculosis (TB) and has been used ever since to vaccinate children globally. It has also been used as the first-line treatment in patients with nonmuscle invasive bladder cancer (NMIBC), through repeated intravesical applications. Numerous studies have shown that BCG induces off-target immune effects in various pathologies. Accumulating data argue for the critical role of the immune system in the course of neurodegenerative diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). In this study, we tested whether repeated exposure to BCG during the treatment of NMIBC is associated with the risk of developing AD and PD. We presented a multi-center retrospective cohort study with patient data collected between 2000 and 2019 that included 12,185 bladder cancer (BC) patients, of which 2301 BCG-treated patients met all inclusion criteria, with a follow-up of 3.5 to 7 years. We considered the diagnosis date of AD and nonvascular dementia cases for BC patients. The BC patients were partitioned into those who underwent a transurethral resection of the bladder tumor followed by BCG therapy, and a disjoint group that had not received such treatment. By applying Cox proportional hazards (PH) regression and competing for risk analyses, we found that BCG treatment was associated with a significantly reduced risk of developing AD, especially in the population aged 75 years or older. The older population (≥75 years, 1578 BCG treated, and 5147 controls) showed a hazard ratio (HR) of 0.726 (95% CI: 0.529–0.996; p-value = 0.0473). While in a hospital-based cohort, BCG treatment resulted in an HR of 0.416 (95% CI: 0.203–0.853; p-value = 0.017), indicating a 58% lower risk of developing AD. The risk of developing PD showed the same trend with a 28% reduction in BCG-treated patients, while no BCG beneficial effect was observed for other age-related events such as Type 2 diabetes (T2D) and stroke. We attributed BCG’s beneficial effect on neurodegenerative diseases to a possible activation of long-term nonspecific immune effects. We proposed a prospective study in elderly people for testing intradermic BCG inoculation as a potential protective agent against AD and PD.

Minocycline alleviates peripheral nerve adhesion by promoting regulatory macrophage polarization via the TAK1 and its downstream pathway

AIMS

Inflammation plays a key role in peripheral nerve adhesion and often leads to severe pain and nerve dysfunction. Minocycline was reported to have potent anti-inflammatory effects and might be a promising drug to prevent or attenuate peripheral nerve adhesion. The present study aimed to clarify whether minocycline contributes to nerve adhesion protection and its underlying mechanism.

MATERIALS AND METHODS

Rats with sciatic nerve adhesion induced by glutaraldehyde glue (GG) were intraperitoneally injected with minocycline or saline every 12 h for 7 consecutive days. After that, the adhesion score, Ashcroft score, demyelination, macrophage polarization and inflammatory factors in peripheral nerve adhesion tissues or tissues in sham group were determined with histological staining, western blot and real time-PCR. Murine macrophage RAW264.7 cells were stimulated by LPS alone or together with minocycline at different concentrations and time duration to study the mechanism of minocycline in alleviating nerve adhesion.

KEY FINDINGS

We found that minocycline treatment reduced the adhesion score, Ashcroft score, the growth of scar tissue, demyelination, and macrophage recruitment. Moreover, minocycline significantly and dose-dependently promoted regulatory macrophage polarization but decreased pro-inflammatory macrophage polarization. Furthermore, mechanism studies showed that TAK1 and its downstream pathway p38/JNK/ERK1/2/p65 were inhibited by minocycline, which led to lower IL-1β and TNFα expression, but increased IL-10 expression.

SIGNIFICANCE

Altogether, these results suggest that minocycline is highly effective against peripheral nerve adhesion through anti-fibrosis, anti-inflammation, and myelination protection, making it a highly promising candidate for treating adhesion-related disorders.

Effects of the Prenatal Administration of Tetanus Toxoid on the Sociability and Explorative Behaviors of Rat Offspring: A Preliminary Study

OBJECTIVE

Autism spectrum disorder (ASD) is a severely disabling psychiatric disease characterized by impairments in communication and social skills. Although efforts have been made to explore the etiology of ASD, its pathophysiology remains unclear. This issue is rendered more challenging by confounding data about the effects of vaccination on disease etiology. In this study, therefore, we investigated the neurodevelopmental effects of maternal tetanus toxoid administration on rat offspring. We hypothesized that the vaccine affects the sociability and preference for social novelty of rat offspring as well as the production of immunological and neurotrophic factors, including tumor necrosis factor-alfa (TNF-α), neuregulin-1 (NRG-1), neuron growth factor (NGF), and oxytocin.

METHODS

The study involved 12 female and 4 male adult Sprague-Dawley rats (238 ± 10 g), which were assigned to two groups. Group 1 (control group) was given 0.5 ml of normal saline (0.9% NaCl) on the 10th day of pregnancy, whereas Group 2 (experimental group) was administered 0.5 ml of tetanus vaccine (tetanus toxoid, 40 IU).

RESULTS

Maternal tetanus toxoid administration exerted beneficial effects on the sociability and explorative behaviors of the rats. The brain tissue levels of TNF-α, NGF, NRG-1, and oxytocin were higher in the experimental group than those among the controls. All these significant differences were found in both the male and female rats.

CONCLUSION

This study is the first to demonstrate the advantages of tetanus toxoid administration in relation to the sociability and explorative behaviors of rat offspring. The results showed that the vaccine also influences NRG-1, neuregulin, and oxytocin production.

A 20-Year Journey from Axonal Injury to Neurodegenerative Diseases and the Prospect of Immunotherapy for Combating Alzheimer's Disease

The understanding of the dialogue between the brain and the immune system has undergone dramatic changes over the last two decades, with immense impact on the perception of neurodegenerative diseases, mental dysfunction, and many other brain pathologic conditions. Accumulated results have suggested that optimal function of the brain is dependent on support from the immune system, provided that this immune response is tightly controlled. Moreover, in contrast to the previous prevailing dogma, it is now widely accepted that circulating immune cells are needed for coping with brain pathologies and that their optimal effect is dependent on their type, location, and activity. In this perspective, we describe our own scientific journey, reviewing the milestones in attaining this understanding of the brain-immune axis integrated with numerous related studies by others. We then explain their significance in demonstrating the possibility of harnessing the immune system in a well-controlled manner for the treatment of neurodegenerative diseases.

Sleep-restriction Inhibits Neurogenesis Through Decreasing the Infiltration of CD169+ Macrophages to Ischemic Brain After Stroke

Chronic sleep-restriction (SR) is shown to be correlated with neurodevelopmental disorders. However, the effects of SR during stroke recovery on neurorepair remain unclear. In this study, mice were subjected to 60 min of cerebral ischemia followed by reperfusion. The SR protocol was accomplished by depriving mice of sleep for 20 h/day for 14 days starting at 14 days post-ischemia. We found that SR increased CD169⁺ macrophages infiltration into the ischemic brain parenchyma and inhibited neurogenesis and functional recovery. SR decreased CD169⁺ macrophages infiltration into the choroid plexus (CP) and cerebrospinal fluid (CSF), accompanied by increased expression of Chemokine C-X3-C-Motif Ligand 1 (CX3CL1) and intercellular adhesion molecule (ICAM-1) via IFN-γ/IFN-γR signaling in the CP. When splenic CD169⁺ macrophages sorted from Kaede transgenic mice were administered into CSF of C57BL/6 mice, they homed to the ischemic brain parenchyma. Moreover, blockade of IFN-γ/IFN-γR signaling, CX3CL1 or ICAM-1 decreased CD169⁺ macrophages infiltration into the CP, CSF and ischemic brain parenchyma, as well as decreasing neurogenesis and functional recovery after SR. The promoting roles of infiltrated CD169⁺ macrophages in post-stroke neurogenesis were due to increasing regulatory T cells (Tregs) in the ischemic brain parenchyma. Furthermore, dexmedetomidine treatment during SR increased CD169⁺ macrophages infiltration into the CP, CSF and ischemic brain parenchyma, and promoted neurogenesis and functional recovery. Taken together, our results showed that SR during stroke recovery decreased Tregs in the ischemic brain parenchyma by decreasing CD169⁺ macrophages infiltration to the ischemic brain parenchyma across the CP, which inhibited neurogenesis and functional recovery.

Protective Effect of Sphaerococcus coronopifolius Crude Extract in Combination with Bacillus Calmette-Guerin on Ligature-Induced Depression in Female Wistar Rats

OBJECTIVE

Immunomodulation is a therapeutic technique that modulates the balance of cytokines in the body. In this regard, our experiment was conducted to investigate the potential effect of S. coronopifolius crude extract in combination with low dose of Bacillus Calmette-Guerin (BCG) on depression-like behaviors in female Wistar rats.

METHODS

Sciatic nerve injury was employed to induce depression and intradermal injection of 0.02 mL of BCG per rat was administered to lead an activation of innate immune system. Daily intra-peritoneal injections of 25 mg algae extract kg-1 body weight were performed for 14 continuous days. Forced Swimming (FS) and Open Field (OF) tests were conducted to assess despairing and spontaneous behaviors. At the end of the experiment, brain was removed to determine the activities of catalase (CAT) and glutathione-S-transferase (GST), whereas spleen and adrenals were used for the histopathological study.

RESULTS

The combined treatment exhibited antidepressant-like activity in FST by reducing immobility time, without inducing any significant change in ambulatory behavior in OFT. The histological analyses of spleen and adrenal structure showed a conserved architecture.

CONCLUSION

The results suggested that algae extract produce an antidepressant-like effect in combination with low dose of BCG, which is possibly trigged by its anti-oxidant and anti-inflammatory properties.

Bacillus Calmette-Guérin (BCG) therapy lowers the incidence of Alzheimer's disease in bladder cancer patients

BACKGROUND

Alzheimer's disease (AD) affects one in ten people older than 65 years. Thus far, there is no cure or even disease-modifying treatment for this disease. The immune system is a major player in the pathogenesis of AD. Bacillus Calmette-Guérin (BCG), developed as a vaccine against tuberculosis, modulates the immune system and reduces recurrence of non-muscle invasive bladder cancer. Theoretical considerations suggested that treatment with BCG may decrease the risk of AD. We tested this hypothesis on a natural population of bladder cancer patients.

METHODS AND FINDINGS

After removing all bladder cancer patients presenting with AD or developing AD within one-year following diagnosis of bladder cancer, we collected data on a total of 1371 patients (1134 males and 237 females) who were followed for at least one year after the diagnosis of bladder cancer. The mean age at diagnosis of bladder cancer was 68.1 years (SD 13.0). Adjuvant post-operative intra-vesical treatment with BCG was given to 878 (64%) of these patients. The median period post-operative follow-up was 8 years. During follow-up, 65 patients developed AD at a mean age of 84 years (SD 5.9), including 21 patients (2.4%) who had been treated with BCG and 44 patients (8.9%) who had not received BCG. Patients who had been treated with BCG manifested more than 4-fold less risk for AD than those not treated with BCG. The Cox proportional hazards regression model and the Kaplan-Meier analysis of AD free survival both indicated high significance: patients not treated with BCG had a significantly higher risk of developing AD compared to BCG treated patients (HR 4.778, 95%CI: 2.837-8.046, p = 4.08x10-9 and Log Rank Chi-square 42.438, df = 1, p = 7.30x10-11, respectively). Exposure to BCG did not modify the prevalence of Parkinson's disease, 1.9% in BCG treated patients and 1.6% in untreated (Fisher's Exact Test, p = 1).

CONCLUSIONS

Bladder cancer patients treated with BCG were significantly less likely to develop AD at any age than patients who were not so treated. This finding of a retrospective study suggests that BCG treatment might also reduce the incidence of AD in the general population. Confirmation of such effects of BCG in other retrospective studies would support prospective studies of BCG in AD.

Potential Immunotherapeutic Targets on Myeloid Cells for Neurovascular Repair After Ischemic Stroke

Neurological deficits and cognitive dysfunctions caused by acute ischemic stroke pose enormous burden to the stroke families and the communities. Restoration of the normal function of the neurovascular unit following ischemic stroke is critical for improving neurological recovery and cognitive functions after stroke. Recent evidence suggests that the myeloid cells including both the resident microglia and infiltrating monocytes/macrophages and neutrophils are highly plastic in response to the environmental cues. They intimately interact with multiple components of the neurovascular unit in response to the alarmins, danger associated pattern molecules (DAMPs) and other signals released from the ischemic brain. The aim of this review is to discuss the reciprocal interactions between the myeloid cells and the ischemic neurovascular unit during the late repair phase of cerebral ischemic stroke. We also summarize potential immunotherapeutic targets on myeloid cells and new therapeutic approaches targeting myeloid cells, such as cell transplantation, mitochondrial dynamic and extracellular vesicles-based therapy et al to enhance neurovascular repair for better stroke recovery.

Synergistic effects of combined vaccination with BCG and influenza vaccines on spatial cognition and hippocampal plasticity in rats

Previous study has demonstrated the neurobeneficial role of BCG and influenza vaccines. Based on this, our study concentrated on the synergistic effects on development of central nervous system by combined vaccination with BCG and influenza vaccines in rats. Our results displayed that pups combinedly vaccinated with BCG and influenza vaccines showed a significant enhance in spatial cognition, induction of LTP, hippocampal neurogenesis and morphology of dendritic spines compared with pups vaccinated with BCG solely. Furthermore, combined vaccination with BCG and influenza vaccines showed higher expression of BDNF, IGF-1, IL-4, IFN-γ and lower IL-1β, TNF-α and IL-6 than BCG. Taken together, combined vaccination with BCG and influenza vaccines presented synergistic effects on spatial cognition and hippocampal plasticity in rats.

Bridging the gap between vaccination with Bacille Calmette-Guérin (BCG) and immunological tolerance: the cases of type 1 diabetes and multiple sclerosis

At the end of past century, when the prevailing view was that treatment of autoimmunity required immune suppression, experimental evidence suggested an approach of immune-stimulation such as with the BCG vaccine in type 1 diabetes (T1D) and multiple sclerosis (MS). Translating these basic studies into clinical trials, we showed the following: BCG harnessed the immune system to 'permanently' lower blood sugar, even in advanced T1D; BCG appeared to delay the disease progression in early MS; the effects were long-lasting (years after vaccination) in both diseases. The recently demonstrated capacity of BCG to boost glycolysis may explain both the improvement of metabolic indexes in T1D, and the more efficient generation of inducible regulatory T cells, which counteract the autoimmune attack and foster repair mechanisms.

The evolving role of neuro-immune interaction in brain repair after cerebral ischemic stroke

Stroke is the world's leading cause of disability with limited brain repair treatments which effectively improve long-term neurological deficits. The neuroinflammatory responses persist into the late repair phase of stroke and participate in all brain repair elements, including neurogenesis, angiogenesis, synaptogenesis, remyelination and axonal sprouting, shedding new light on post-stroke brain recovery. Resident brain glial cells, such as astrocytes not only contribute to neuroinflammation after stroke, but also secrete a wide range of trophic factors that can promote post-stroke brain repair. Alternatively, activated microglia, monocytes, and neutrophils in the innate immune system, traditionally considered as major damaging factors after stroke, have been suggested to be extensively involved in brain repair after stroke. The adaptive immune system may also have its bright side during the late regenerative phase, affecting the immune suppressive regulatory T cells and B cells. This review summarizes the recent findings in the evolving role of neuroinflammation in multiple post-stroke brain repair mechanisms and poses unanswered questions that may generate new directions for future research and give rise to novel therapeutic targets to improve stroke recovery.

Switching of the Microglial Activation Phenotype Is a Possible Treatment for Depression Disorder

Major depressive disorder (MDD) is a common emotional cognitive disorder that seriously affects people’s physical and mental health and their quality of life. Due to its clinical and etiological heterogeneity, the molecular mechanisms underpinning MDD are complex and they are not fully understood. In addition, the effects of traditional drug therapy are not ideal. However, postmortem and animal studies have shown that overactivated microglia can inhibit neurogenesis in the hippocampus and induce depressive-like behaviors. Nonetheless, the molecular mechanisms by which microglia regulate nerve regeneration and determine depressive-like behaviors remain unclear. As the immune cells of the central nervous system (CNS), microglia could influence neurogenesis through the M1 and M2 subtypes, and these may promote depressive-like behaviors. Microglia may be divided into four main states or phenotypes. Under stress, microglial cells are induced into the M1 type, releasing inflammatory factors and causing neuroinflammatory responses. After the inflammation fades away, microglia shift into the alternative activated M2 phenotypes that play a role in neuroprotection. These activated M2 subtypes consist of M2a, M2b and M2c and their functions are different in the CNS. In this article, we mainly introduce the relationship between microglia and MDD. Importantly, this article elucidates a plausible mechanism by which microglia regulate inflammation and neurogenesis in ameliorating MDD. This could provide a reliable basis for the treatment of MDD in the future.

Prenatal influenza vaccination rescues impairments of social behavior and lamination in a mouse model of autism

Background

Prenatal infection is a substantial risk factor for neurodevelopmental disorders such as autism in offspring. We have previously reported that influenza vaccination (VAC) during early pregnancy contributes to neurogenesis and behavioral function in offspring.

Results

Here, we probe the efficacy of VAC pretreatment on autism-like behaviors in a lipopolysaccharide (LPS)-induced maternal immune activation (MIA) mouse model. We show that VAC improves abnormal fetal brain cytoarchitecture and lamination, an effect associated with promotion of intermediate progenitor cell differentiation in MIA fetal brain. These beneficial effects are sufficient to prevent social deficits in adult MIA offspring. Furthermore, whole-genome analysis suggests a strong interaction between Ikzf1 (IKAROS family zinc-finger 1) and neuronal differentiation. Intriguingly, VAC rescues excessive microglial Ikzf1 expression and attenuates microglial inflammatory responses in the MIA fetal brain.

Conclusions

Our study implies that a preprocessed influenza vaccination prevents maternal bacterial infection from causing neocortical lamination impairments and autism-related behaviors in offspring.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1252-z) contains supplementary material, which is available to authorized users.

Calcitonin gene-related peptide decreases IL-1beta, IL-6 as well as Ym1, Arg1, CD163 expression in a brain tissue context-dependent manner while ameliorating experimental autoimmune encephalomyelitis

Activation states of immune cells (among them, the so-called pro- or anti-inflammatory states) influence the pathogenesis of multiple sclerosis (MS). The neuropeptide calcitonin gene-related peptide (CGRP) can exert a pro- or anti-inflammatory role in a context-dependent manner. In mice CGRP was found to attenuate the development of experimental autoimmune encephalomyelitis (EAE, a common MS animal model). We analyzed CGRP effects on the expression of cytokines and markers of activation states, as well as its intracellular cascade, following intrathecal administration during EAE immunization. Real Time quantitative-PCR (RT-PCR) showed that IL-1beta and IL-6 (associated to a pro-inflammatory state in EAE), but also Ym1 (also known as Chil3), Arg1 and CD163 (associated to an anti-inflammatory state in EAE) were decreased in the encephalon (devoid of cerebellum). In the cerebellum itself, IL-1beta and Ym1 were decreased. TNF-alpha (associated to a pro-inflammatory state in EAE), but also IL-10 (associated to another type of anti-inflammatory state) and BDNF were unchanged in these two regions. No changes were detected in the spinal cord. Additional tendencies toward a change (as revealed by RT-PCR) were again decreases: IL-10 in the encephalon and Arg1 in the spinal cord. CGRP decreased percentage of Ym1⁺/CD68⁺ immunoreactive cells and cell density of infiltrates in the cervical spinal cord pia mater. Instead, Ym1 in the underlying parenchyma and at thoracic and lumbar levels, as well as Arg1, were unchanged. In cultured microglia the neuropeptide decreased Ym1, but not Arg1, immunoreactivity. Inducible NOS (iNOS) was unchanged in spinal cord microglia and astrocytes. The neuropeptide increased the activation of ERK1/2 in the astrocytes of the spinal cord and in culture, but did not influence the activation of ERK1/2 or p38 in the spinal cord microglia. Finally, in areas adjacent to infiltration sites CGRP-treated microglia showed a larger ramification radius. In conclusion, CGRP-induced EAE amelioration was associated to a concomitant, context-dependent decrease in the expression of markers belonging to both pro- or anti-inflammatory activation states of immune cells. It can be hypothesized that CGRP-induced EAE attenuation is obtained through a novel mechanism that promotes down-regulation of immune cell activation that facilitates the establishment of a beneficial environment in EAE provided possibly also by other factors.

An enriched environment restores hepatitis B vaccination-mediated impairments in synaptic function through IFN-γ/Arginase1 signaling

Activation of the neonatal immune system may contribute to deficits in neuronal plasticity. We have reported that neonatal vaccination with a hepatitis B vaccine (HBV) transiently impairs mood status and spatial memory involving a systemic T helper (Th) 2 bias and M1 microglial activation. Here, an EE induced microglial anti-inflammatory M2 polarization, as evidenced by selectively enhanced expression of the Arginase1 gene (Arg-1) in the hippocampus. Interestingly, knock-down of the Arg-1 gene prevented the effects of EE on restoring the dendritic spine density. Moreover, levels of the Th1-derived cytokine IFN-gamma (IFN-γ) were elevated in the choroid plexus (CP), which is the interface between the brain and the periphery. IFN-γ-blocking antibodies blunted the protective effects of an EE on spine density and LTP. Furthermore, levels of complement proteins C1q and C3 were elevated, and this elevation was associated with synapse loss induced by the HBV, whereas an EE reversed the effects of the HBV. Similarly, blockade of C1q activation clearly prevented synaptic pruning by microglia, LTP inhibition and memory deficits in hepatitis B-vaccinated mice. Together, the EE-induced increase in IFN-γ levels in the CP may disrupt systemic immunosuppression related to HBV via an IFN-γ/Arg-1/complement-dependent pathway.

CD8+ T cells are essential for the effects of enriched environment on hippocampus-dependent behavior, hippocampal neurogenesis and synaptic plasticity

Enriched environment (EE) induces plasticity changes in the brain. Recently, CD4⁺ T cells have been shown to be involved in brain plasticity processes. Here, we show that CD8⁺ T cells are required for EE-induced brain plasticity in mice, as revealed by measurements of hippocampal volume, neurogenesis in the DG of the hippocampus, spinogenesis and glutamatergic synaptic function in the CA of the hippocampus. As a consequence, EE-induced behavioral benefits depend, at least in part, on CD8⁺ T cells. In addition, we show that spleen CD8⁺ T cells from mice housed in standard environment (SE) and EE have different properties in terms of 1) TNFα release after in vitro CD3/CD28 or PMA/Iono stimulation 2) in vitro proliferation properties 3) CD8⁺ CD44⁺ CD62L^low and CD62L^hi T cells repartition 4) transcriptomic signature as revealed by RNA sequencing. CD8⁺ T cells purified from the choroid plexus of SE and EE mice also exhibit different transcriptomic profiles as highlighted by single-cell mRNA sequencing. We show that CD8⁺ T cells are essential mediators of beneficial EE effects on brain plasticity and cognition. Additionally, we propose that EE differentially primes CD8⁺ T cells leading to behavioral improvement.