Combination ELISAs for antiviral antibodies in CSF and serum in patients with neurological symptoms and in healthy controls

AAV Gene Therapy Redosing in the CNS

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Recent progress and considerations for AAV gene therapies targeting the central nervous system

BACKGROUND

Neurodevelopmental disorders, as a class of diseases, have been particularly difficult to treat even when the underlying cause(s), such as genetic alterations, are understood. What treatments do exist are generally not curative and instead seek to improve quality of life for affected individuals. The advent of gene therapy via gene replacement offers the potential for transformative therapies to slow or even stop disease progression for current patients and perhaps minimize or prevent the appearance of symptoms in future patients.

MAIN BODY

This review focuses on adeno-associated virus (AAV) gene therapies for diseases of the central nervous system. An overview of advances in AAV vector design for therapy is provided, along with a description of current strategies to develop AAV vectors with tailored tropism. Next, progress towards treatment of neurodegenerative diseases is presented at both the pre-clinical and clinical stages, focusing on a few select diseases to highlight broad categories of therapeutic parameters. Special considerations for more challenging cases are then discussed in addition to the immunological aspects of gene therapy.

CONCLUSION

With the promising clinical trial results that have been observed for the latest AAV gene therapies and continued pre-clinical successes, the question is no longer whether a therapy can be developed for certain neurodevelopmental disorders, but rather, how quickly.

The detection of intrathecal synthesis of anti-herpes simplex IgG antibodies: comparison between an antigen-mediated immunoblotting technique and antibody index calculations. European Union Concerted Action on Virus Meningitis and Encephalitis

The detection of intrathecal antibody synthesis was compared by the calculation of antibody indices (AI) derived from ELISA techniques with the detection of virus-specific oligoclonal IgGs by an antigen-mediated capillary blot technique. Twenty-seven paired serum and cerebrospinal fluid (CSF) samples were examined from 15 immunocompetent patients with herpes simplex virus encephalitis (HSE) diagnosed by PCR on early CSF samples. These techniques were also applied to paired samples from 20 multiple sclerosis (MS) patients, 10 patients with other inflammatory neurological diseases and 10 patients with non inflammatory neurological disorders. There was a good correlation between the results obtained by AI and those obtained by immunoblotting, especially in HSE (2 discordant results out of 27). Discrepancies were more frequent (25%) in MS patients where a "polyspecific" reaction characterized by low affinity antibodies is known to occur. Some of the discrepancies could, in part, be due to serological cross-reaction with varicella zoster virus.

Specific diagnostic methods for herpesvirus infections of the central nervous system: a consensus review by the European Union Concerted Action on Virus Meningitis and Encephalitis

BACKGROUND

Herpesvirus infections of the central nervous system are often severe but are fortunately rare. The incidence of these infections has however, increased in recent years as a consequence of an increase in the number of immune-compromised individuals. New diagnostic procedures have improved our ability to diagnose these infections and herpesviruses may yet be implicated as the cause of further neurological diseases with no known aetiology. Methodological standards for selection and evaluation of patient materials are essential to the provision of reliable diagnosis, yet few studies have addressed this important issue.

OBJECTIVES

To describe and define methodological standards and reference methodology for diagnosis of herpesvirus infections of the CNS.

STUDY DESIGN

Information gathered by literature review.

RESULTS

Only for herpes simplex encephalitis is there sufficient data to allow the definition of reference methodology. Good methodological standards exist but few studies have adhered to these standards. As methods for the detection of specific intrathecal antibody synthesis are well established yet under-used in diagnostic virology, the principle of these measurements is reviewed in some detail.

CONCLUSIONS

Herpesvirus infections of the CNS are of increasing importance. High quality, multi-centre studies are needed to establish the value of the new diagnostic test procedures if further improvement in the diagnostic sensitivity and specificity of these procedures is to be achieved.

Viral etiology of acute childhood encephalitis in Beijing diagnosed by analysis of single samples

OBJECTIVE

To understand the viral etiology of acute childhood encephalitis in Beijing.

METHODS

Ninety-seven Chinese children (between 7 months and 13 years of age) with acute encephalitis were retrospectively investigated. They were treated in Beijing Children's Hospital between June, 1991, and October, 1994. Different serologic methods (immunofluorescence assay, enzyme-linked immunosorbent assay, solid phase reverse immunosorbent test) were used for detection of IgM antibody to enteroviruses, herpesviruses, mumps, measles, rubella and Japanese encephalitis virus. The viral DNA of six herpesviruses was detected by polymerase chain reaction.

RESULTS

Viral etiology was identified in 35 of 97 (36.0%) cases. The most frequently identified pathogens were enteroviruses (15; 15.4%), followed by mumps (7; 7.2%), rubella (6; 6.1%), Japanese encephalitis virus (5; 5.1%), human herpesvirus 6 (2; 2.0%), herpes simplex virus (2; 2.0%) and Epstein-Barr virus (1; 1.0%). IgM antibody in cerebrospinal fluid was detected for enterovirus, mumps and rubella viruses.

CONCLUSIONS

Enteroviruses were the most frequent viral pathogens of acute childhood encephalitis in Beijing. Detection of IgM in cerebrospinal fluid may be useful for diagnosis in certain cases of viral encephalitis.

Intrathecal synthesis of IgG in simian immunodeficiency virus (SIV)-infected rhesus macaques (Macaca mulatta)

We examined cerebrospinal fluid (CSF) and serum from 25 simian immunodeficiency (SIV)-infected rhesus macaques for the presence of SIV-specific immunoglobulin G (IgG) and for intrathecal synthesis of IgG. SIV-specific IgG was present in CSF from almost 50% of the macaques. In approximately half of these animals the SIV-specific IgG appeared to be derived from serum by leakage across a disrupted blood-brain barrier, whereas in the remaining animals there was evidence of intrathecal IgG synthesis. There were no significant associations between CSF SIV-specific IgG, intrathecal IgG synthesis and isolation of virus from CSF, clinical status, or neuropathological findings. However, SIV-specific IgG was absent from CSF in all four of the macaques with SIV encephalitis. The presence of SIV-specific IgG in CSF may have a modulating effect on the development of SIV-associated neurological disease.

Acute "idiopathic" peripheral facial palsy: clinical, serological, and cerebrospinal fluid findings and effects of corticosteroids

INTRODUCTION

The causes for peripheral facial palsy remain obscure in many patients. Evidence exists suggesting viruses, especially those belonging to the herpesvirus group, may be causative. This study was developed to evaluate this theory.

METHODS

One hundred forty-seven patients with acute peripheral facial palsy of primarily unknown origin were studied. All were examined within 1 week of onset. Subsequent follow-up was undertaken until the palsy had recovered or become static. Paried cerebral spinal fluid and serum samples were obtained for serological evaluation to detect herpes simplex, varicella zoster, cytomegalovirus, measles, mumps, rubella, tick-borne encephalitis, adenovirus, Epstein-Barr virus, and human immunodeficiency virus, as well as the antibodies to Borrelia burgdorferi.

RESULTS

Elevated antibiotic titers to Borrelia burgdorferi were observed in 11% of patients, whereas 9% of patients demonstrated elevated viral titers. Antibody pattern consistent with Epstein-Barr virus reactivation was present in 13%. A total of 67% were classified as idiopathic.

CONCLUSION

Patients with reactivated Epstein-Barr virus were characterized by having a higher incidence of auricular pain and displayed diabetes mellitus in a higher frequency than in other groups. In the Borrelia group, neck/back pain was more common. Healing was less favorable in the Borrelia group despite an equal rate of palsy at onset and adequate antibiotic treatment. Corticosteroid treatment used in 44% of the patients did not significantly improve the functional outcome.

Early diagnosis of enteroviral meningitis by detection of specific IgM antibodies with a solid-phase reverse immunosorbent test (SPRIST) and mu-capture EIA

A solid-phase reverse immunosorbent test (SPRIST) and a mu-capture enzyme immunosorbent assay (EIA) for detection of enterovirus-specific IgM antibodies were evaluated for enterovirus diagnosis of aseptic meningitis in 160 consecutive patients from whom enterovirus (11 different serotypes) were isolated in 64. In patients with an enterovirus isolate and/or four-fold titre rise in the complement fixation test (CFT) for enterovirus, specific enterovirus IgM antibodies were detected on the day of admission to hospital in 48% by SPRIST and in 50% by EIA and 4-6 days after onset of symptoms in 71% by SPRIST and 79% by EIA. A significant increase in titre was observed between serum sampled on the day of admission and 2 days later in 38% by SPRIST and in 41% by EIA. These results indicate that the IgM antibody response appears early in the course of aseptic meningitis. Since both SPRIST and EIA provide rapid results the tests may be of differential diagnostic value and the IgM antibody kinetics may be utilized for diagnosis during the acute phase of aseptic meningitis. With optimized serum sampling the positive outcome was 76% in SPRIST and 82% in EIA among patients with positive virus isolation and/or CFT for enterovirus. In 67 patients virus isolation and CFT for enterovirus yielded negative results as well as all non-enteroviral diagnostic tests. Thirty-eight of these patients were positive by SPRIST and/or EIA and in half of these 38 a significant titre rise and/or fall in SPRIST and/or EIA was recorded. The majority of these IgM-positive patients became ill in the late summer or autumn, i.e., the "enterovirus season."(ABSTRACT TRUNCATED AT 250 WORDS)

Acute peripheral facial palsy: CSF findings and etiology

CSF and serum were examined in acute and convalescence phase from 56 patients with acute idiopathic peripheral facial palsy. CSF protein analysis, viral and borrelia serology were performed. Borrelia infection was found in 9/56 cases and was often associated with inflammatory CSF findings. One patient each had serological evidence for a recent or ongoing infection with herpes simplex, varicella zoster, adeno, influenza B, echo and Epstein-Barr virus, but none had specific intrathecal antibody synthesis; 11 patients had a serological pattern compatible with a reactivated Epstein-Barr virus infection. Eleven patients displayed mononuclear CSF pleocytosis. Four of them had a borrelia infection. A disturbed blood-brain barrier was observed in 19 patients. Intrathecal immunoglobulin synthesis as indicated by elevated IgM-indices was found in 16 patients and by IgG indices in three. Nine patients had oligoclonal IgG bands in serum and CSF, three exclusively in CSF. It is concluded that patients with facial palsy often have inflammatory CSF findings, indicating a generalised central nervous system affection, and not only a mononeuritis. The importance of viral infections in the pathogenesis is still obscure. Borrelia is the most common infectious cause of facial palsy.

A sensitive ELISA system for the rapid detection of virus specific IgM antibodies in the cerebrospinal fluid

The intrathecal production of IgM antibodies to different viral antigens was measured by a modification of ELISA that was both sensitive and specific. Suitably diluted CSF and homologous serum samples containing similar amount of IgM were examined, and a comparison of the photometric signals permitted the detection of specific antibodies secreted from activated lymphocytes into the CSF compartment during the course of viral infections of the central nervous system. Polyvinyl chloride (PVC) microtitre plates were activated by glutaraldehyde and then coated with different viral antigens. Test samples were incubated on these solid-phase antigens and virus-specific IgM antibodies were detected using a peroxidase-conjugated F (ab')2 fragment of anti-human IgM antibody to avoid interference from rheumatoid factors.

Total, anti-viral, and anti-myelin IgG subclass reactivity in inflammatory diseases of the central nervous system

Total IgG subclass levels, anti-viral, anti-myelin basic protein (anti-MBP), and anti-ganglioside 1 (anti-GM1) IgG subclass levels were measured in 6 patients with herpes simplex virus encephalitis (HSVE), 16 with borreliosis, 8 with other bacterial infections, 12 with multiple sclerosis (MS), 13 with subacute sclerosing panencephalitis (SSPE), 5 with glioblastoma and 12 controls. Total IgG1 levels were elevated in cerebrospinal fluid (CSF) from all patient groups (but not in the controls), IgG2 in bacterial infections, IgG3 in HSVE and borreliosis and IgG4 in some SSPE patients. The anti-viral (anti-measles, varicella zoster virus and rubella) IgG antibodies in MS were restricted to IgG1, anti-measles IgG to IgG1 and sometimes IgG4 in SSPE, anti-borrelia IgG to IgG1, IgG2 and IgG3. In contrast to anti-viral antibodies, anti-MBP and GM1 antibodies belonged to IgG1, IgG3 or IgG4 in MS. The nature of the immunological activation appears to be reflected in the subclass patterns elicited in the central nervous system. Different IgG subclass patterns in infectious diseases and MS suggest a difference between antigen-specific and non-specific B-cell activation.

Antiviral IgM and IgG subclasses in varicella zoster associated neurological syndromes

The varicella zoster virus (VZV) and herpes simplex virus (HSV) IgGl-4 subclasses were compared in serum and cerebrospinal fluid (CSF) of 22 patients with VZV-associated neurological symptoms, 12 patients with HSV-associated neurological symptoms and 14 controls. The clinical syndromes of the VZV-associated diseases comprised meningo-encephalitis, myelitis, myelopathies and polyneuropathies, mostly with a favourable outcome. A characteristic finding was an intrathecal synthesis of VZV IgG1 and HSV-3. Commonly also IgG2 and 4 were seen in CSF of VZV patients. Their intrathecally synthesised HSV IgG was restricted to IgG1. VZV IgG3 occurred in serum and/or CFS together with VZV IgM in 14 cases and may be a marker of recent VZV replication. In patients with HSV-associated neurological disease, a multi-IgG subclass HSV response and concomitant VZV antibodies restricted to IgG1 was found. Intrathecal synthesis of both HSV and VZV IgG occurred in 20 patients. Detection of two or more VZV or HSV specific IgG subclasses synthesised intrathecally identified the aetiological agent in 19 of these 20 cases.

Specific IgG subclass reactivity in herpes simplex encephalitis

Serum and cerebrospinal fluid (CSF) samples from 19 patients with a previous diagnosis of herpes simplex virus encephalitis (HSVE), from 14 patients with a previous diagnosis of non HSVE encephalitis and from 21 healthy subjects were examined to detect IgG subclasses 1-4 reactive with herpes simplex virus (HSV), cytomegalovirus (CMV) and varicella zoster virus (VZV). Antibodies to HSV were detected in CSF and serum from the 14 HSVE-patients with a reactivated HSV infection and from 3 of the 5 patients with a primary HSV infection. The predominant subclass pattern was an early HSV-specific IgG1 rise, followed by IgG3 and, more seldom, IgG4; HSV IgG2 was rarely seen. In HSVE patients, HSV IgG3 was absent in early samples and usually appeared 10-20 days after onset of disease. In 14 out of 16 seropositive healthy controls, on the other hand, HSV IgG3 was present in the CSF. Rising VZV IgG levels in serum and CSF were found in 11 HSVE patients. Eight of them showed signs of intrathecal VZV IgG1 synthesis. The VZV IgG reactivity was restricted to IgG1 in 7 of these whereas the HSV IgG subclass response also included IgG3 or 4. The appearance of several HSV IgG subclasses appeared to serve as a marker of HSV infection in spite of the serological VZV reaction, usually restricted to VZV IgG1. Intrathecal synthesis of the quantitatively minor HSV IgG3 and 4 subclasses was detected earlier than intrathecal synthesis of total HSV IgG, dominated by IgG1 in 4 patients with HSVE.