A review of blood diseases and cytopenias associated with human parvovirus B19 infection

Viruses and thrombocytopenia

Thrombocytopenia, characterized by a decrease in platelet count, is a multifaceted clinical manifestation that can arise from various underlying causes. This review delves into the intriguing nexus between viruses and thrombocytopenia, shedding light on intricate pathophysiological mechanisms and highlighting the pivotal role of platelets in viral infections. The review further navigates the landscape of thrombocytopenia in relation to specific viruses, and sheds light on the diverse mechanisms through which hepatitis C virus (HCV), measles virus, parvovirus B19, and other viral agents contribute to platelet depletion. As we gain deeper insights into these interactions, we move closer to elucidating potential therapeutic avenues and preventive strategies for managing thrombocytopenia in the context of viral infections.

COVID-19 in patients with anemia and haematological malignancies: risk factors, clinical guidelines, and emerging therapeutic approaches

Extensive research in countries with high sociodemographic indices (SDIs) to date has shown that coronavirus disease 2019 (COVID-19) may be directly associated with more severe outcomes among patients living with haematological disorders and malignancies (HDMs). Because individuals with moderate to severe immunodeficiency are likely to undergo persistent infections, shed virus particles for prolonged periods, and lack an inflammatory or abortive phase, this represents an overall risk of morbidity and mortality from COVID-19. In cases suffering from HDMs, further investigation is needed to achieve a better understanding of triviruses and a group of related variants in patients with anemia and HDMs, as well as their treatment through vaccines, drugs, and other methods. Against this background, the present study aimed to delineate the relationship between HDMs and the novel COVID-19, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Besides, effective treatment options for HDM cases were further explored to address this epidemic and its variants. Therefore, learning about how COVID-19 manifests in these patients, along with exploiting the most appropriate treatments, may lead to the development of treatment and care strategies by clinicians and researchers to help patients recover faster. Video Abstract.

Pediatric central nervous system infections in the Amazon: clinical and laboratory profiles

Background

Central nervous system (CNS) infections are important causes of mortality and morbidity in children, and they are related to severe problems such as hearing loss, neurological sequelae, and death. The objective was to describe clinical and laboratory exam profiles of children who were diagnosed with CNS infections.

Methods

We conducted a cross-sectional study based on medical records, which included pediatric patients aged from 3 months to 15 years, with a clinical suspicion of CNS infection between January 2014 to December 2019. The pathogens were confirmed in cerebrospinal fluid (CSF) samples using Gram staining, cell culture, molecular diagnostics (PCR and qPCR), and serology.

Results

Out of the 689 enrolled patients, 108 (15.6%) had laboratory-confirmed infections in CSF. The most common bacterial pathogens isolated from the culture were Neisseria meningitidis serogroup C in 19, Streptococcus pneumoniae in 11, and Haemophilus influenzae in seven samples. The viruses identified were Enterovirus, Cytomegalovirus, Varicella-zoster virus, Epstein-Barr virus, and arbovirus. No patient was found to be positive for Herpes simplex virus 1 and 2. Patients with viral infections showed altered levels of consciousness (p = 0.001) when compared to bacterial infections.

Conclusion

This study shows the presence of important vaccine-preventable pathogens, and different families of viruses causing CNS infections in the pediatric patients of Manaus.

Non-Permissive Parvovirus B19 Infection: A Reservoir and Questionable Safety Concern in Mesenchymal Stem Cells

Mesenchymal stromal/stem cells (MSCs) are multipotent cells with differentiation, immunoregulatory and regenerative properties. Because of these features, they represent an attractive tool for regenerative medicine and cell-based therapy. However, MSCs may act as a reservoir of persistent viruses increasing the risk of failure of MSCs-based therapies and of viral transmission, especially in immunocompromised patients. Parvovirus B19V (B19V) is a common human pathogen that infects bone marrow erythroid progenitor cells, leading to transient or persistent anemia. Characteristics of B19V include the ability to cross the placenta, infecting the fetus, and to persist in several tissues. We thus isolated MSCs from bone marrow (BM-MSCs) and fetal membrane (FM-MSCs) to investigate their permissiveness to B19V infection. The results suggest that both BM- and FM- MSCs can be infected by B19V and, while not able to support viral replication, allow persistence over time in the infected cultures. Future studies are needed to understand the potential role of MSCs in B19V transmission and the conditions that can favor a potential reactivation of the virus.

Next Generation Sequencing for the Analysis of Parvovirus B19 Genomic Diversity

Parvovirus B19 (B19V) is a ssDNA human virus, responsible for an ample range of clinical manifestations. Sequencing of B19V DNA from clinical samples is frequently reported in the literature to assign genotype (genotypes 1-3) and for finer molecular epidemiological tracing. The increasing availability of Next Generation Sequencing (NGS) with its depth of coverage potentially yields information on intrinsic sequence heterogeneity; however, integration of this information in analysis of sequence variation is not routinely obtained. The present work investigated genomic sequence heterogeneity within and between B19V isolates by application of NGS techniques, and by the development of a novel dedicated bioinformatic tool and analysis pipeline, yielding information on two newly defined parameters. The first, α-diversity, is a measure of the amount and distribution of position-specific, normalised Shannon Entropy, as a measure of intra-sample sequence heterogeneity. The second, σ-diversity, is a measure of the amount of inter-sample sequence heterogeneity, also incorporating information on α-diversity. Based on these indexes, further cluster analysis can be performed. A set of 24 high-titre viraemic samples was investigated. Of these, 23 samples were genotype 1 and one sample was genotype 2. Genotype 1 isolates showed low α-diversity values, with only a few samples showing distinct position-specific polymorphisms; a few genetically related clusters emerged when analysing inter-sample distances, correlated to the year of isolation; the single genotype 2 isolate showed the highest α-diversity, even if not presenting polymorphisms, and was an evident outlier when analysing inter-sample distance. In conclusion, NGS analysis and the bioinformatic tool and pipeline developed and used in the present work can be considered effective tools for investigating sequence diversity, an observable parameter that can be incorporated into the quasispecies theory framework to yield a better insight into viral evolution dynamics.

Case Report: Parvovirus B19 infection complicated by hemophagocytic lymphohistiocytosis in a heart-lung transplant patient

Immunosuppressed patients can contract parvovirus B19, and some may experience hemophagocytic lymphohistiocytosis (HLH). Herein, we describe the first report of hemophagocytic lymphohistiocytosis in a heart-lung transplant patient with concomitant parvovirus B19 infection. The patient was treated with intravenous immune globulin (IVIG) and the features of HLH were remission. This instance emphasizes the significance of parvovirus B19 monitoring in transplant patients with anemia; if HLH complicates the situation, IVIG may be an adequate remedy. Finally, a summary of the development in diagnosing and managing parvovirus B19 infection complicated by HLH is provided.

[Parvovirus B19 infections in adults]

Acute Parvovirus B19 (PVB19) infection is responsible for erythema infectiosum in children and non-specific polyarthralgias in immunocompetent adults associated with skin lesions and rarer manifestations (hepatic, neurological, cardiac or nephrological). In immunocompromised patients, cytopenias are more frequent and in some cases, viremia persists and is responsible for PVB19 chronic infection. PVB19 is responsible for pure red cell aplasia during chronic hemolytic diseases. Acute PVB19 infection is a differential diagnosis of some autoimmune diseases and has been suspected to be a trigger for some autoimmune diseases because of its ability to promote the emergence of autoimmune markers. Mechanisms of molecular mimicry, induction of apoptosis and activation of enzymes have been demonstrated, explaining in part the production of autoantibodies during infection. However, the demonstration of a causal relationship in the triggering of autoimmune disease remains to be done. This review provides a synthesis of the PVB19 infection clinical data in adults with a particular focus on these links with autoimmunity.

Hemophagocytic lymphohistiocytosis associated with parvovirus B19-induced aplastic crisis in a hereditary spherocytosis patient: A case report and literature review

Hemophagocytic lymphohistiocytosis (HLH) is a syndrome of pathologic immune activation. It occurs because of severe inflammation due to uncontrolled proliferation of activated lymphocytes and histiocytes, characterized by the production of excessive levels of cytokines. Virus-associated HLH is a well-known entity, and parvovirus B19 is one of the common causes. Parvovirus B19 can also affect blood cell lineages. Therefore, HLH may be accompanied by several diseases such as cytopenia, aplastic anemia, and myelodysplastic syndrome. Herein, we report the case of a patient with hereditary spherocytosis who was diagnosed with parvovirus B19-induced HLH and aplastic crisis. A 7-year-old girl presented to our hospital with fever, pleural effusion, pancytopenia, hepatosplenomegaly, and hypotension. A bone marrow biopsy was performed under the suspicion of HLH, which revealed hemophagocytes. The diagnostic criteria for HLH were met, and prompt chemoimmunotherapy was initiated considering the clinically unstable situation. Her health improved rapidly after initiating treatment. Further study revealed that she had hereditary spherocytosis, and parvovirus B19 had caused aplastic crisis and HLH. The patient's clinical progress was excellent, and chemoimmunotherapy was reduced and discontinued at an early stage. This case shows that aplastic crisis and HLH can coexist with parvovirus B19 infection in patients with hereditary spherocytosis. Although the prognosis was good in this case of HLH caused by parvovirus B19, early detection and active treatment are essential.

A Functional Minigenome of Parvovirus B19

Parvovirus B19 (B19V) is a human pathogenic virus of clinical relevance, characterized by a selective tropism for erythroid progenitor cells in bone marrow. Relevant information on viral characteristics and lifecycle can be obtained from experiments involving engineered genetic systems in appropriate in vitro cellular models. Previously, a B19V genome of defined consensus sequence was designed, synthesized and cloned in a complete and functional form, able to replicate and produce infectious viral particles in a producer/amplifier cell system. Based on such a system, we have now designed and produced a derived B19V minigenome, reduced to a replicon unit. The genome terminal regions were maintained in a form able to sustain viral replication, while the internal region was clipped to include only the left-side genetic set, containing the coding sequence for the functional NS1 protein. Following transfection in UT7/EpoS1 cells, this minigenome still proved competent for replication, transcription and production of NS1 protein. Further, the B19V minigenome was able to complement B19-derived, NS1-defective genomes, restoring their ability to express viral capsid proteins. The B19V genome was thus engineered to yield a two-component system, with complementing functions, providing a valuable tool for studying viral expression and genetics, suitable to further engineering for purposes of translational research.

Neurological Manifestations Associated with Parvovirus B19 Infection in Immunocompetent Children: Case Series and Systematic Review

An increasing number of reports have described human parvovirus B19 infection in association with a variety of neurological manifestations, especially in children. This study assessed the clinical and laboratory outcomes found in a case series of immunocompetent children who tested positive for parvovirus B19 by qualitative polymerase chain reaction assays of cerebrospinal fluid, in a tertiary referral center in the western Brazilian Amazon. We screened 178 children with clinically diagnosed central nervous system infections (meningoencephalitis). Of these, five (2.8%) were positive for parvovirus B19. A literature review also presented herein identified a further 50 cases of parvovirus B19 with neurological manifestations. Thus, even if the classic signs of parvovirus B19 infection are absent, such as the well-known rash, children with signs of neurological infection should also be evaluated for parvovirus B19 infection.

Leukoerythroblastosis as an Unusual Presentation of Parvovirus B19 Infection in a Sickle Cell Patient

Parvovirus B19 infection in pediatrics most commonly causes fifth disease, a mild viral illness. Hematologic manifestations include severe anemia, especially in patients with chronic hemolytic anemias or who are immunocompromised. Because of the shortened life span of erythrocytes in patients with sickle cell disease, parvovirus infection can cause transient aplastic crisis which can be life-threatening. However, leukocytosis and thrombocytosis are rarely seen. We report leukoerythroblastosis as an unusual presentation of acute parvovirus B19 infection in a previously splenectomized 12-year-old boy with sickle cell disease.

No G-Quadruplex Structures in the DNA of Parvovirus B19: Experimental Evidence versus Bioinformatic Predictions

Parvovirus B19 (B19V), an ssDNA virus in the family Parvoviridae, is a human pathogenic virus, responsible for a wide range of clinical manifestations, still in need of effective and specific antivirals. DNA structures, including G-quadruplex (G4), have been recognised as relevant functional features in viral genomes, and small-molecule ligands binding to these structures are promising antiviral compounds. Bioinformatic tools predict the presence of potential G4 forming sequences (PQSs) in the genome of B19V, raising interest as targets for antiviral strategies. Predictions locate PQSs in the genomic terminal regions, in proximity to replicative origins. The actual propensity of these PQSs to form G4 structures was investigated by circular dichroism spectroscopic analysis on synthetic oligonucleotides of corresponding sequences. No signature of G4 structures was detected, and the interaction with the G4 ligand BRACO-19 (N,N'-(9-{[4-(dimethylamino)phenyl]amino}acridine-3,6-diyl)bis(3-pyrrolidin-1-ylpropanamide) did not appear consistent with the stabilisation of G4 structures. Any potential role of PQSs in the viral lifecycle was then assessed in an in vitro infection model system, by evaluating any variation in replication or expression of B19V in the presence of the G4 ligands BRACO-19 and pyridostatin. Neither showed a significant inhibitory activity on B19V replication or expression. Experimental challenge did not support bioinformatic predictions. The terminal regions of B19V are characterised by relevant sequence and symmetry constraints, which are functional to viral replication. Our experiments suggest that these impose a stringent requirement prevailing over the propensity of forming actual G4 structures.

Genetic Basis of Myocarditis: Myth or Reality?

The genetic basis of myocarditis remains an intriguing concept, at least as long as the definition of myocarditis constitutes the definitive presence of myocardial inflammation sufficient to cause the observed ventricular dysfunction in the setting of cardiotropic infections. Autoimmune or immune-mediated myocardial inflammation constitutes a complex area of clinical interest, wherein numerous and not yet fully understood role of hereditary auto-inflammatory diseases can result in inflammation of the pericardium and myocardium. Finally, myocardial involvement in hereditary immunodeficiency diseases, cellular and humoral, is a possible trigger for infections which may complicate the diseases themselves. Whether the role of constitutional genetics can make the patient susceptible to myocardial inflammation remains yet to be explored.

Aggressive large B-cell lymphoma triggered by a parvovirus B19 infection in a previously healthy child

In absence of red blood cells disease or immune defect, parvovirus B19 (PVB-19) is usually considered as a benign condition. Here, we report the case of a 10-year-old boy, previously healthy, presenting with a PVB-19 infection revealed by a bicytopenia and a voluminous axillary adenopathy. Pathophysiology examination showed reactional lymphoid population. Nine months later and in the absence of remission, a new biopsy of the same adenopathy revealed a Hodgkin lymphoma with area of T-cell rich aggressive large B-cell lymphoma. This case suggests PVB-19 as potential trigger of this malignant childhood hemopathy. Although no definitive conclusion can be drawn, our clinical case questions the role of PVB-19 in lymphomagenesis.

Prevalence and disease association of human parvovirus B19 in Iran: a systematic review

Aim: The prevalence of human parvovirus B19 (B19V) and its association with other diseases in Iran are yet to be systematically assessed. This study aimed to evaluate the prevalence and disease association of B19V across Iran from 2000 to 2019. Methods: The literature search, based on different keywords in different databases, was performed. A total of 29 eligible studies were included and the essential information was collected from each article. Results: The results of this study show a relatively high prevalence of the B19V-associated diseases in all age groups of the Iranian population. Conclusion: The transmission of B19V and its complications should be prevented by developing preventative strategies.

Advances in the Development of Antiviral Strategies against Parvovirus B19

Parvovirus B19 (B19V) is a human pathogenic virus, responsible for an ample range of clinical manifestations. Infections are usually mild, self-limiting, and controlled by the development of a specific immune response, but in many cases clinical situations can be more complex and require therapy. Presently available treatments are only supportive, symptomatic, or unspecific, such as administration of intravenous immunoglobulins, and often of limited efficacy. The development of antiviral strategies against B19V should be considered of highest relevance for increasing the available options for more specific and effective therapeutic treatments. This field of research has been explored in recent years, registering some achievements as well as interesting future perspectives. In addition to immunoglobulins, some compounds have been shown to possess inhibitory activity against B19V. Hydroxyurea is an antiproliferative drug used in the treatment of sickle-cell disease that also possesses inhibitory activity against B19V. The nucleotide analogues Cidofovir and its lipid conjugate Brincidofovir are broad-range antivirals mostly active against dsDNA viruses, which showed an antiviral activity also against B19V. Newly synthesized coumarin derivatives offer possibilities for the development of molecules with antiviral activity. Identification of some flavonoid molecules, with direct inhibitory activity against the viral non-structural (NS) protein, indicates a possible line of development for direct antiviral agents. Continuing research in the field, leading to better knowledge of the viral lifecycle and a precise understanding of virus–cell interactions, will offer novel opportunities for developing more efficient, targeted antiviral agents, which can be translated into available therapeutic options.

Human parvovirus B19 infection in patients with or without underlying diseases

BACKGROUND/PURPOSE

The clinical presentations of parvovirus B19 in patients with underlying diseases have greater diversity than previously healthy patients. We retrospectively identified patients with polymerase chain reaction (PCR)-confirmed parvovirus B19 infection in attempt to describe its clinical features especially in these populations.

METHODS

From 2009 to 2018, patients with real-time PCR-confirmed parvovirus B19 infection were collected. Comparisons were done between previously healthy patients and patients with preexisting diseases, as well as patients with high (>5.5 × 10⁵ copies/mL sera) and low viral loads.

RESULTS

Parvovirus B19 DNA was detected in 31 patients. Fourteen (45%) patients had underlying diseases, including six (19%) with immunologic diseases, five (16%) with hematologic diseases, and three (10%) with cardiopulmonary diseases. Only seven (23%) patients received an initial impression of erythema infectiosum prior to positive PCR. A higher proportion of patients with underlying diseases presented with fatigue and pallor, and suffered from tachycardia and hepatosplenomegaly compared to previously healthy patients. Among patients with a high viral load, a substantial proportion were of older age, suffered fatigue, and anemia. There was a trend of patients with immunologic comorbidity having a higher viral load.

CONCLUSION

The classical parvovirus B19 manifestations were less frequently observed in patients with a preexisting disease compared with previously healthy patients. Depending on host factors, the symptoms of parvovirus B19 infection can be multifaceted.

Clinical impact & pathogenic mechanisms of human parvovirus B19: A multiorgan disease inflictor incognito

Human parvovirus B19 (B19V) causes myriads of clinical diseases; however, owing to lack of awareness and undetermined clinical impact, it has failed to become a virus pathogen of global concern. Cryptically, B19V causes significant morbidity and mortality. Half of the world population and 60 per cent of Indians are known to be serologically naive and are at risk of acquiring B19V infections. Cumulatively, our data showed 21.3 per cent B19V-infected patients with juvenile chronic arthropathy, recurrent abortions, multi-transfused thalassaemia and leukaemia. In addition, B19V-infected cases that ended fatally included patients with pure red cell aplasia, fulminant hepatitis and haemophagocytic syndrome. Novel clinical associations of B19V observed were amegakaryocytic thrombocytopaenia, myositis and non-occlusive ischaemic gangrene of bowel. B19V possesses multiple receptors which are distributed widely in human tissues. Vascular endothelial cell infection by B19V causes endothelialitis and vasculitic injuries besides antibody-dependent enhancement which empowered B19V to cause multiorgan diseases. Owing to lack of suitable animal model for B19V, true causal role remains to be determined, but numerous reports on B19V infections substantiate a causal role in multiorgan diseases. Hence, B19V infections need to be recognized, investigated and treated besides making efforts on vaccine developments.

Parvoviral disease in childhood cancer: Clinical outcomes and impact on therapy at a tertiary cancer center in India

BACKGROUND AND AIM

Parvovirus-B19 disease in immunocompromised children can cause myelosuppression and therapeutic delays. We studied the clinical profiles of children having symptoms suggestive of parvoviral disease at our institution, a large tertiary cancer center.

METHODS

Children below age 15 years undergoing treatment for malignancies with clinical features suggestive of parvoviral infection, and/or unexplained drop in hemoglobin, and/or prolonged cytopenia were screened for parvovirus infection using DNA-PCR for parvovirus-B19 (PB19) in the peripheral blood. Patients testing positive from September 2014 till February 2017 were studied.

RESULTS

Of the 59 patients (36 patients with hematolymphoid malignancies, 23 with solid tumors) screened for suspected parvoviral infections, 27 tested positive. Median age was 9.6 years (2.25-15 years), 18 (66%) had hematolymphoid malignancies, while 7 (33%) had solid tumors. Six patients (26%) were on intensive phases, 16 (60%) patients developed the symptoms during maintenance chemotherapy, and 4 (15%) after completion of therapy. Isolated anemia was the commonest feature seen in 10 patients (37%) while bicytopenia and pancytopenia were noticed in 8 (30%) and 9 (33%) patients respectively. Fifty percent of patients those who received rituximab (3/6) developed persistent parvoviremia (>4 weeks) as compared with 24% (5/21) of those who did not. Two patients (7%) developed hemophagocytic lymphohistiocytosis (HLH). Treatment delay by more than 14 days was encountered in a majority (62%), with 5 patients requiring treatment modification or even suspension.

CONCLUSIONS

Parvoviral infection in children who are on or have recently completed chemotherapy can lead to multiple cytopenias and significant treatment delays. Rituximab exposure may lead to persistent parvoviral disease (p < 0.05). HLH, though occasional, can be a serious complication.

Frequency and Genotype of Human Parvovirus B19 among Iranian Hemodialysis and Peritoneal Dialysis Patients

OBJECTIVES

The aim of this study was to evaluate the frequency and genotype of human parvovirus B19 and its relation with anemia among Iranian patients under dialysis.

METHODS

Fifty hemodialysis (HD) and 33 peritoneal dialysis (PD) patients were enrolled. B19 IgG and IgM antibodies were assessed by ELISA, and the presence of B19 DNA was evaluated by nested PCR. PCR products were sequenced directly and phylogenetic analysis was performed.

RESULTS

In the HD group, the prevalence of B19 antibodies was 54% for IgG and 4% for IgM. B19 DNA was detected in 10% of the cases, and 10% showed B19 IgG and viremia simultaneously. In the PD group, the prevalence of B19 IgG and IgM was 57.6 and 0% respectively, whereas B19 DNA was found in 12.1% of the group. A total of 9.1% showed B19 IgG and viremia concurrently. There was no significant difference regarding anemia and B19 infection in either group. All B19 isolates were clustered in genotype 1A.

CONCLUSION

Our findings indicate that B19 infection plays no role in leading chronic anemia in dialysis patients. However, persistent B19 viremia and the circulation of the same strains in dialysis patients may indicate a potential risk for the contamination of dialysis equipment and nosocomial spread of B19 infection within dialysis units.

Human Parvoviruses

Parvovirus B19 (B19V) and human bocavirus 1 (HBoV1), members of the large Parvoviridae family, are human pathogens responsible for a variety of diseases. For B19V in particular, host features determine disease manifestations. These viruses are prevalent worldwide and are culturable in vitro, and serological and molecular assays are available but require careful interpretation of results. Additional human parvoviruses, including HBoV2 to -4, human parvovirus 4 (PARV4), and human bufavirus (BuV) are also reviewed. The full spectrum of parvovirus disease in humans has yet to be established. Candidate recombinant B19V vaccines have been developed but may not be commercially feasible. We review relevant features of the molecular and cellular biology of these viruses, and the human immune response that they elicit, which have allowed a deep understanding of pathophysiology.

Acute encephalitis and encephalopathy associated with human parvovirus B19 infection in children

Reports of neurologic manifestations of human parvovirus B19 (B19) infection have been on the rise. Acute encephalitis and encephalopathy is the most common, accounting for 38.8% of total B19-associated neurological manifestations. To date, 34 children with B19 encephalitis and encephalopathy have been reported, which includes 21 encephalitis and 13 encephalopathy cases. Ten (29%) were immunocompromised and 17 (39%) had underlying diseases. Fever at the onset of disease and rash presented in 44.1% and 20.6% of patients, respectively. Neurological manifestations include alteration of consciousness occurred in all patients, seizures in 15 (44.1%) patients, and focal neurologic signs in 12 (35.3%) patients. Anemia and pleocytosis in cerebrospinal fluid (CSF) occurred in 56.3% and 48.1% of patients, respectively. Serum Anti-B19 IgM (82.6%) and CSF B19 DNA (90%) were positive in the majority of cases. Some patients were treated with intravenous immunoglobulins and/or steroids, although an accurate evaluation of the efficacy of these treatment modalities cannot be determined. Nineteen (57.6%) patients recovered completely, 11 (33.3%) patients had some neurological sequelae and 3 (8.8%) patients died. Although the precise pathogenesis underlying the development of B19 encephalitis and encephalopathy is unclear, direct B19 infection or NS1protein of B19 toxicity in the brain, and immune-mediated brain injuries have been proposed.