Mortality and Neurologic Sequelae in Influenza-Associated Encephalopathy: Retrospective Multicenter PICU Cohort in France

The intersection of influenza infection and autoimmunity

The relationship between viral infection and autoimmune manifestations has been emerging as a significant focus of study, underscoring the intricate interplay between viral infections and the immune system. Influenza infection can result in a spectrum of clinical outcomes, ranging from mild illness to severe disease, including mortality. Annual influenza vaccination remains the most effective strategy for preventing infection and its associated complications. The complications arising from acute influenza infection are attributable not only to the direct effects of the viral infection but also to the dysregulated immune response it elicits. Notably, associations between influenza and various autoimmune diseases, such as Guillain-Barré Syndrome (GBS), Type 1 Diabetes (T1D), and antiphospholipid syndrome, have been reported. While viral infections have long been recognized as potential triggers of autoimmunity, the underlying mechanisms remain to be elucidated. Here, we described the pathophysiology caused by influenza infection and the influenza-associated autoimmune manifestations. Current advances on the understanding of the underlying immune mechanisms that lead to the potential strategies were also summarized.

Predictive value of the serum procalcitonin level for fulminant virus-associated encephalopathy

BACKGROUND

Fulminant virus-associated encephalopathy (VAE) is a rare complication of viral infection that presents as acute brain dysfunction and requires respiratory support and/or vasoactive agents. However, the mechanism of VAE is undetermined. The mortality rate is high since there is no specific treatment for fulminant VAE. The aim of this study was to identify risk factors for children with fulminant VAE on the basis of clinical data since timely recognition and treatment might be needed to improve the poor prognosis.

METHODS

This retrospective study included children with fulminant VAE who were diagnosed between June 2018 and October 2023 in the PICU of Guangdong Women and Children Hospital. Clinical data were analyzed, and receiver operating characteristic (ROC) curve analysis was performed to determine the prognostic value of the selected variables.

RESULTS

Twenty-three children with fulminant VAE were included and divided into a survival group (n = 16) and a nonsurvival group (n = 7). The mortality rate of patients with fulminant VAE was 30.8%. Compared with the survival group, the nonsurvival group had higher incidences of shock 48 h after onset, a higher acute necrotizing encephalopathy severity score (ANE-SS), higher procalcitonin (PCT) levels, and lower platelet counts (p < 0.05). The serum PCT level was significantly higher in the children with shock than in those without shock (p = 0.015). The serum PCT concentration was positively correlated with the ANE-SS (correlation coefficient 0.544, p < 0.039). Combined immunotherapies might help to decrease PCT levels in some children. Low PCT levels might be related to a good outcome. The area under the curve (AUC) for PCT used to predict death in patients with fulminant VAEs was 0.821 (95% CI 0.626-1.00). The sensitivity and specificity of PCT > 101.58 ng/ml for predicting death in patients with fulminant VAE were 57.1% and 100.0%, respectively.

CONCLUSIONS

Patients with fulminant VAE deteriorate rapidly and are at high risk of death if they develop shock within 48 h after onset, exhibit extremely elevated serum PCT levels, or have decreased platelet counts. The serum PCT level might predict the death outcome of patients with fulminant VAE.

Mortality risk factors in children with influenza-associated encephalopathy admitted to the paediatric intensive care unit between 2009 and 2021

AIM

The purpose of this study was to determine the risk factors for death in children with influenza-associated encephalopathy (IAE) in the paediatric intensive care unit (PICU).

METHODS

Forty-six paediatric patients with IAE admitted to the PICU at shenzhen Children's Hospital between December 2009 and December 2021 were evaluated. Their clinical characteristics were retrospectively analysed.

RESULTS

A total of 46 patients were diagnosed with influenza A virus infection and encephalopathy. The cases were concentrated in children <5 years of age (27/46, 58.7%). Twenty-nine patients (63.0%) survived and 17 patients (37.0%) died, of which 70.6% (12/17) of the patients died within 1 week of hospitalisation. Thirty-two patients (69.6%) developed neurological symptoms within 1-2 days of fever onset. Common symptoms included fever (45/46, 97.8%), loss of consciousness (39/46, 84.8%), seizures (31/46, 67.4%), cough (19/46, 41.3%), and vomiting (16/46, 34.8%). Multivariate logistic regression analysis indicated that vomiting (odds ratio [OR], 11.005), loss of consciousness (AVPU score: P; OR, 15.871), lymphopenia (OR, 8.964), alanine aminotransferase (>80 IU/L; OR, 32.060) and serum sodium concentration (>145 mmol/L or <135 mmol/L; OR, 16.264) were related to mortality.

CONCLUSIONS

The mortality in this study population was 37.0%. Children with IAE who have corresponding clinical manifestations and abnormal examination results in PICU should be warned of the high mortality rate.

Viral entry and translation in brain endothelia provoke influenza-associated encephalopathy

Influenza-associated encephalopathy (IAE) is extremely acute in onset, with high lethality and morbidity within a few days, while the direct pathogenesis by influenza virus in this acute phase in the brain is largely unknown. Here we show that influenza virus enters into the cerebral endothelium and thereby induces IAE. Three-weeks-old young mice were inoculated with influenza A virus (IAV). Physical and neurological scores were recorded and temporal-spatial analyses of histopathology and viral studies were performed up to 72 h post inoculation. Histopathological examinations were also performed using IAE human autopsy brains. Viral infection, proliferation and pathogenesis were analyzed in cell lines of endothelium and astrocyte. The effects of anti-influenza viral drugs were tested in the cell lines and animal models. Upon intravenous inoculation of IAV in mice, the mice developed encephalopathy with brain edema and pathological lesions represented by micro bleeding and injured astrocytic process (clasmatodendrosis) within 72 h. Histologically, massive deposits of viral nucleoprotein were observed as early as 24 h post infection in the brain endothelial cells of mouse models and the IAE patients. IAV inoculated endothelial cell lines showed deposition of viral proteins and provoked cell death, while IAV scarcely amplified. Inhibition of viral transcription and translation suppressed the endothelial cell death and the lethality of mouse models. These data suggest that the onset of encephalopathy should be induced by cerebral endothelial infection with IAV. Thus, IAV entry into the endothelium, and transcription and/or translation of viral RNA, but not viral proliferation, should be the key pathogenesis of IAE.

Influenza H7N9 virus disrupts the monolayer human brain microvascular endothelial cells barrier in vitro

Influenza H7N9 virus causes human infections with about 40% case fatality rate. The severe cases usually present with pneumonia; however, some present with central nervous system complications. Pneumonia syndrome is attributed to the cytokine storm after infection with H7N9, but the pathogenic mechanism of central nervous system complications has not been clarified. This study used immortalized human brain microvascular endothelial cells hCMEC/D3 to simulate the blood-brain barrier. It demonstrated that H7N9 virus could infect brain microvascular endothelial cells and compromise the blood-brain barrier integrity and permeability by down-regulating the expression of cell junction-related proteins, including claudin-5, occludin, and vascular endothelial (VE)-cadherin. These results suggested that H7N9 could infect the blood-brain barrier in vitro and affect its functions, which could be a potential mechanism for the pathogenesis of H7N9 viral encephalopathy.

State of the Art: Acute Encephalitis

Encephalitis is a devastating neurologic disease often complicated by prolonged neurologic deficits. Best practices for the management of adult patients include universal testing for a core group of etiologies, including herpes simplex virus (HSV)-1, varicella zoster virus (VZV), enteroviruses, West Nile virus, and anti-N-methyl-D-aspartate receptor (anti-NMDAR) antibody encephalitis. Empiric acyclovir therapy should be started at presentation and in selected cases continued until a second HSV-1 polymerase chain reaction test is negative. Acyclovir dose can be increased for VZV encephalitis. Supportive care is necessary for other viral etiologies. Patients in whom no cause for encephalitis is identified represent a particular challenge. Management includes repeat brain magnetic resonance imaging, imaging for occult malignancy, and empiric immunomodulatory treatment for autoimmune conditions. Next-generation sequencing (NGS) or brain biopsy should be considered. The rapid pace of discovery regarding autoimmune encephalitis and the development of advanced molecular tests such as NGS have improved diagnosis and outcomes. Research priorities include development of novel therapeutics.

Case report: Acute necrotizing encephalopathy: a report of a favorable outcome and systematic meta-analysis of outcomes with different immunosuppressive therapies

Acute Necrotizing Encephalopathy (ANE) is a condition characterized by symmetric, bilateral lesions affecting the thalamus and potentially other areas of the brain following an acute febrile illness. It manifests clinically as abrupt development of encephalopathy, or alteration in mental status that often includes development of seizures and progression to coma. Treatment strategies combine immunosuppressive therapies and supportive care with varying levels of recovery, however there are no universally accepted, data-driven, treatment algorithms for ANE. We first report a case of a previously healthy 10-year-old female with acute onset diplopia, visual hallucinations, lethargy, and seizures in the setting of subacute non-specific viral symptoms and found to have bilateral thalamic and brainstem lesions on MRI consistent with ANE. She was treated with a combination of immunomodulatory therapies and ultimately had a good outcome. Next, we present a meta-analysis of 10 articles with a total of 158 patients meeting clinical and radiographic criteria for ANE. Each article reported immunosuppressive treatments received, and associated morbidity or mortality outcome for each individual patient. Through our analysis, we confirm the effectiveness of high-dose, intravenous, methylprednisolone (HD-IV-MP) therapy implemented early in the disease course (initiation within 24 h of neurologic symptom onset). There was no significant difference between patients treated with and without intravenous immunoglobulin (IVIG). There was no benefit of combining IVIG with early HD-IV-MP. There is weak evidence suggesting a benefit of IL-6 inhibitor tocilizumab, especially when used in combination with early HD-IV-MP, though this analysis was limited by sample size. Finally, plasma exchange (PLEX) improved survival. We hope this meta-analysis will be useful for clinicians making treatment decisions for patients with this potentially devastating condition.