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

Infection with and Carriage of Mycoplasma pneumoniae in Children

“Atypical” pneumonia was described as a distinct and mild form of community-acquired pneumonia (CAP) already before Mycoplasma pneumoniae had been discovered and recognized as its cause. M. pneumoniae is detected in CAP patients most frequently among school-aged children from 5 to 15 years of age, with a decline after adolescence and tapering off in adulthood. Detection rates by polymerase chain reaction (PCR) or serology in children with CAP admitted to the hospital amount 4–39%. Although the infection is generally mild and self-limiting, patients of every age can develop severe or extrapulmonary disease. Recent studies indicate that high rates of healthy children carry M. pneumoniae in the upper respiratory tract and that current diagnostic PCR or serology cannot discriminate between M. pneumoniae infection and carriage. Further, symptoms and radiologic features are not specific for M. pneumoniae infection. Thus, patients may be unnecessarily treated with antimicrobials against M. pneumoniae. Macrolides are the first-line antibiotics for this entity in children younger than 8 years of age. Overall macrolides are extensively used worldwide, and this has led to the emergence of macrolide-resistant M. pneumoniae, which may be associated with severe clinical features and more extrapulmonary complications. This review focuses on the characteristics of M. pneumoniae infections in children, and exemplifies that simple clinical decision rules may help identifying children at high risk for CAP due to M. pneumoniae. This may aid physicians in prescribing appropriate first-line antibiotics, since current diagnostic tests for M. pneumoniae infection are not reliably predictive.

Diagnostic strategy used to establish etiologies of encephalitis in a prospective cohort of patients in England

The laboratory diagnostic strategy used to determine the etiology of encephalitis in 203 patients is reported. An etiological diagnosis was made by first-line laboratory testing for 111 (55%) patients. Subsequent testing, based on individual case reviews, resulted in 17 (8%) further diagnoses, of which 12 (71%) were immune-mediated and 5 (29%) were due to infection. Seventy-five cases were of unknown etiology. Sixteen (8%) of 203 samples were found to be associated with either N-methyl-d-aspartate receptor or voltage-gated potassium channel complex antibodies. The most common viral causes identified were herpes simplex virus (HSV) (19%) and varicella-zoster virus (5%), while the most important bacterial cause was Mycobacterium tuberculosis (5%). The diagnostic value of testing cerebrospinal fluid (CSF) for antibody was assessed using 139 samples from 99 patients, and antibody was detected in 46 samples from 37 patients. Samples collected at 14 to 28 days were more likely to be positive than samples taken 0 to 6 days postadmission. Three PCR-negative HSV cases were diagnosed by the presence of virus-specific antibody in the central nervous system (CNS). It was not possible to make an etiological diagnosis for one-third of the cases; these were therefore considered to be due to unknown causes. Delayed sampling did not contribute to these cases. Twenty percent of the patients with infections with an unknown etiology showed evidence of localized immune activation within the CNS, but no novel viral DNA or RNA sequences were found. We conclude that a good standard of clinical investigation and thorough first-line laboratory testing allows the diagnosis of most cases of infectious encephalitis; testing for CSF antibodies allows further cases to be diagnosed. It is important that testing for immune-mediated causes also be included in a diagnostic algorithm.

Etiology of aseptic meningitis, peripheral facial nerve palsy, and a combination of both in children

BACKGROUND

A variety of microorganisms have been shown to cause peripheral facial nerve palsy (PFNP) and/or aseptic meningitis in children. Clinical findings and history may help to predict the specific etiology of these entities.

METHOD

Children > or =12 months old hospitalized at the University Children's Hospital Basel, Switzerland, from 2000 to 2005 with clinical signs of PFNP and/or aseptic meningitis were studied retrospectively. History, clinical, and laboratory findings were evaluated using analysis of variance with Bonferroni (Dunn) correction.

RESULTS

Of 181 patients, 123 (68%) had aseptic meningitis, 28 (15%) had PFNP, and 30 (17%) had a combination of both. PFNP with aseptic meningitis was associated with Borrelia burgdorferi (Bb) infection in the majority of patients (73%) compared with 11% and 9% of patients with PFNP or aseptic meningitis, respectively. The majority of patients with aseptic meningitis without PFNP had enterovirus infection (63%). In patients with aseptic meningitis, mean leukocyte counts in cerebrospinal fluid (CSF) were higher with enterovirus (565/microL) compared with Bb infection (191/microL; P < 0.01) or unknown causes (258/microL; P < 0.01). Further, CSF mean mononuclear cell proportion was higher in patients with Bb (89%) than in those with enterovirus infection (51%; P < 0.01) or unknown causes (60%; P < 0.01). Mean time interval between onset of disease and admission to hospital showed significant differences between Bb (7.6 days) and enterovirus infection (2.8 days; P < 0.01) or unknown causes (2.0 days; P < 0.01).

CONCLUSIONS

Time interval between onset of disease and hospital admission and CSF characteristics can contribute to distinguishing the etiology of aseptic meningitis with or without PFNP. As expected, the most common etiology for aseptic meningitis with PFNP was Bb infection whereas enterovirus infection was the predominant cause for aseptic meningitis alone.

Causality in acute encephalitis: defining aetiologies

Defining the causal relationship between a microbe and encephalitis is complex. Over 100 different infectious agents may cause encephalitis, often as one of the rarer manifestations of infection. The gold-standard techniques to detect causative infectious agents in encephalitis in life depend on the study of brain biopsy material; however, in most cases this is not possible. We present the UK perspective on aetiological case definitions for acute encephalitis and extend them to include immune-mediated causes. Expert opinion was primarily used and was supplemented by literature-based methods. Wide usage of these definitions will facilitate comparison between studies and result in a better understanding of the causes of this devastating condition. They provide a framework for regular review and updating as the knowledge base increases both clinically and through improvements in diagnostic methods. The importance of new and emerging pathogens as causes of encephalitis can be assessed against the principles laid out here.

Detection of virus-specific intrathecally synthesised immunoglobulin G with a fully automated enzyme immunoassay system

BACKGROUND

The determination of virus-specific immunoglobulin G (IgG) antibodies in cerebrospinal fluid (CSF) is useful for the diagnosis of virus associated diseases of the central nervous system (CNS) and for the detection of a polyspecific intrathecal immune response in patients with multiple sclerosis. Quantification of virus-specific IgG in the CSF is frequently performed by calculation of a virus-specific antibody index (AI). Determination of the AI is a demanding and labour-intensive technique and therefore automation is desirable. We evaluated the precision and the diagnostic value of a fully automated enzyme immunoassay for the detection of virus-specific IgG in serum and CSF using the analyser BEP2000 (Dade Behring).

METHODS

The AI for measles, rubella, varicella-zoster, and herpes simplex virus IgG was determined from pairs of serum and CSF samples of patients with viral CNS infections, multiple sclerosis and of control patients. CSF and serum samples were tested simultaneously with reference to a standard curve. Starting dilutions were 1:6 and 1:36 for CSF and 1:1386 and 1:8316 for serum samples.

RESULTS

The interassay coefficient of variation was below 10% for all parameters tested. There was good agreement between AIs obtained with the BEP2000 and AIs derived from the semi-automated reference method.

CONCLUSION

Determination of virus-specific IgG in serum-CSF-pairs for calculation of AI has been successfully automated on the BEP2000. Current limitations of the assay layout imposed by the analyser software should be solved in future versions to offer more convenience in comparison to manual or semi-automated methods.

Quantitation of intrathecal antibodies in cerebrospinal fluid of subacute sclerosing panencephalitis, herpes simplex encephalitis and multiple sclerosis: discrimination between microorganism-driven and polyspecific immune response

The detection of intrathecal antibody synthesis by qualitative methods or the Antibody-Index (AI) is a relevant tool for diagnosis of inflammatory neurological diseases. An increased AI can be observed for a causative antigen as well as part of a polyspecific immune response. The quantitation of the intrathecal antibody fraction in cerebrospinal fluid (CSF), F(S), helps to discriminate both cases. In contrast to AI, F(S) needs an absolute antibody concentration detected in the ELISA in mg/L. The intrathecally synthesized, "local" antibody concentration in CSF (AB(Loc)) is expressed as the specific fraction of the intrathecally synthesized total IgG (IgG(Loc)) in CSF with F(S)=AB(Loc)/IgG(Loc) x 100 in %. F(S) for HSV or measles has about 20- to 60-fold higher values in virus-caused antibody synthesis in acute herpes simplex encephalitis (mean HSV-F(S)=8.9%) or subacute sclerosing panencephalitis (mean measles-F(S)=18.8%) compared to the polyspecific immune response against these antigens e.g., in multiple sclerosis (0.14% or 0.52%, correspondingly). F(S) helps also to avoid misinterpretations of an increasing AI in cases of therapy control, and allows direct comparison of relative antibody concentrations (R(S)) in blood and intrathecally synthesized fractions in CSF (F(S)): In multiple sclerosis patients F(S):R(S) has a mean ratio of about 3 for the measles, rubella and VZV antibodies. Together with the large variability we find by ranking that about two third of MS patients have no direct correlation of the relative concentrations in serum and intrathecal synthesis. So this concept gains increasingly relevance for analysis of the polyspecific immune response in brain.

Diagnosis of herpes simplex virus infections of the CNS

Advances in the diagnosis of herpes simplex virus infections of the CNS have occurred rapidly over the past 10 years. The development and application of PCR technology to the detection of herpes simplex virus DNA from cerebrospinal fluid has resulted in tremendous improvements in the management of patients with suspected herpes simplex virus CNS infections, not the least of which is decreasing the necessity for invasive brain biopsy to establish the diagnosis. The pace of discovery has continued in recent years with the development of more rapid DNA amplification techniques that do not require postamplification analysis using amplified products (real-time PCR). However, despite the power of these new diagnostic modalities, test results must always be considered in the context of the patient, and physician judgment should never be usurped by technological advances. This article will summarize the advances in the diagnosis of herpes simplex virus CNS disease within the context of how these advances can enhance the care of individual patients.

The role of antibody affinity for specific antigens in the differential diagnosis of inflammatory nervous system disorders

Affinity maturation has previously been shown with assays for total IgG for specific antigens using the technique of competition by chaotropic ions. We have extended this technique to individual clones and followed the maturation of clones during the course of herpes encephalitis. This has important implications for our understanding of the pathogenesis of multiple sclerosis.

A screening assay to detect antigen-specific antibodies within cerebrospinal fluid

Identification of the aetiology of central nervous system infections requires the detection of either the organism or a microbe-specific immune response within the brain or cerebrospinal fluid. We describe a screening assay to detect herpes simplex virus, varicella zoster virus, cytomegalovirus, measles and Toxoplasma gondii specific antibodies in cerebrospinal fluid. Antigen-specific immunoblotting of oligoclonal IgG and IgM was used to confirm the presence of antibody. Of 51 consecutive cerebrospinal fluid samples received by the laboratory from patients with suspected central nervous system infection 18 (35%) were screen positive for one or more antigen. In only 7 of these were antigen-specific oligoclonal IgG or IgM bands confirmed. The assay provides a simple, cheap assay to screen for microbial-specific antibody in the cerebrospinal fluid samples of patients with suspected neurological infections.

Childhood encephalopathy: viruses, immune response, and outcome

This study examined children with an acute encephalopathy illness for evidence of viral infection, disordered blood-brain barrier function, intrathecal immunoglobulin synthesis, and interferon (IFN) production, and related their temporal occurrence to outcome. A prospective study of 22 children (13 males, 9 females; age range 1mo to 13y, median 2y 4mo), recorded clinical details, with serum and cerebrospinal fluid (CSF) analysis near presentation and then on convalescent specimens taken up to day 39 of the neurological illness. Outcome was assessed with standard scales between 18 months and 3 years after presentation. A history consistent with viral infection was given in 17 children but laboratory evidence of viral infection was found in only 7 (7/17). In 18 out of 21 children, an elevated CSF:serum albumin ratio indicative of impairment of the blood-CSF and blood-brain barriers was detected at some stage of the illness. In 14 of the 15 children with a raised immunoglobulin G index, and in 12 of the 14 children where the CSF was positive for oligoclonal bands, this was preceded by, or was observed at the same time as, an abnormal albumin ratio. Sixteen children (16/18) had elevated IFN-alpha levels in serum, or CSF, or in both. We conclude that these findings indicate an initial disruption of the blood-brain barrier followed by intrathecal antibody production by activated lymphocytes, clonally restricted to a few antigens. This is the first in vivo study to show this as an important pathogenetic mechanism of encephalitis in children. Poor outcome was associated with young age, a deteriorating electroencephalogram pattern from grade 1 to grade 2, and the degree of blood-brain barrier impairment, particularly when prolonged, but not with Glasgow Coma Scale score. The persistence of IFN-alpha was associated with a good prognosis.

Measurement of high affinity antibodies on antigen-immunoblots

We describe a semi-quantitative method for measuring the relative affinity of antigen-specific oligoclonal IgG bands separated by isoelectric focusing followed by blotting onto antigen-coated membrane and incubation with sodium thiocyanate. When the developed blot is digitised in greyscale, densitograms can be made and peak areas calculated using ImageJ freeware. By expressing peak area as a percentage of the total area under the curve we have shown that there is a statistically significant rise in percentage of peak area for a given band which persists with increasing molarities of sodium thiocyanate.

Consensus recommendations of the Italian Association for Neuroimmunology for immunochemical cerebrospinal fluid examination

In 2002-2003, the Italian Association for Neuroimmunology (AINI) ran a program for procedure and method standardization in neuroimmunology. The main purposes of the program were: a) to improve the overall quality of analytical performance and, simultaneously, to reduce costs by resource optimization; b) to establish the bases for clinical guidelines in neurology; c) to promote the formation of laboratory networks and of joint research projects; d) to facilitate the procedures for certification required by governmental/non-governmental agencies. This report summarizes the consensus recommendations of a panel of AINI neuroimmunologists/biochemists involved in the field of cerebrospinal fluid examination. The collection process for said recommendations was guided by "impact-factored" literature and the knowledge of the experts involved. Communication was by email and face-to-face at two dedicated AINI workshops.

Herpes simplex encephalitis: an audit of the use of laboratory diagnostic tests

BACKGROUND

The combination of both PCR and intrathecal antibody studies is recommended to confirm or refute the diagnosis of herpes simplex encephalitis (HSE).

AIM

To investigate the pattern of use of laboratory tests in the diagnosis of suspected cases of HSE, and to determine the final diagnosis in cases proven not to be HSE.

DESIGN

Structured audit.

METHODS

We reviewed the case-notes of all patients who, over a five-year time period, presented with suspected encephalitis; and/or were prescribed aciclovir. Clinical and laboratory criteria were used to categorize the likelihood of HSE.

RESULTS

We identified 222 patients: 10 (5%) had definite HSE, 24 (10%) possible HSE, and 144 (65%) a definite alternative diagnosis. In 44 (20%), no final diagnosis was made, but the diagnosis of HSE was excluded. PCR was performed in 68 (31%), intrathecal antibody studies in 24 (11%), and brain biopsy in 17 (8%). A wide range of diseases mimicked HSE, but most common were inflammatory diseases and other infections of the central nervous system.

DISCUSSION

Laboratory tests, particularly intrathecal antibody assays, are under-used in the diagnosis of HSE. Although early empirical treatment of suspected HSE is essential, confirmation or exclusion of the diagnosis is equally important to avoid overlooking alternative diagnoses. Identification of the aetiology of encephalitis is of particular importance, given the current concerns of emerging infections and bioterrorism.

Productive herpes simplex virus in brain of elderly normal subjects and Alzheimer's disease patients

It was previously shown that herpes simplex virus type 1 (HSV1) DNA resides latently in a high proportion of aged brains and that in carriers of the type 4 allele of the apolipoprotein E gene (APOE-epsilon4), it confers a strong risk of Alzheimer's disease. It was suggested that initial entry of brain by HSV1 and any subsequent reactivation(s) would cause a type of limited encephalitis, the resulting damage being more harmful in APOE-epsilon4 carriers. Reactivation(s) would induce synthesis of intrathecal antibodies; these are long-lived after herpes simplex encephalitis so they were sought in cerebrospinal fluid (CSF) of Alzheimer's disease patients and age-matched normal subjects. Intrathecal antibodies to human herpesvirus 6 (HHV6) were also sought as DNA of this virus has been detected previously in a high proportion of Alzheimer's disease brains. Antibody indices for HSV and HHV6 were measured using indirect ELISA for IgG antibody, and single radial immunodiffusion was used for albumin, in serum and CSF. A raised antibody index (>1.5) indicative of virus-specific intrathecal HSV1 IgG synthesis was found in 14/27 (52%) Alzheimer's disease patients and 9/13 (69%) age-matched normals (difference non-significant). A raised antibody index to HHV6 was detected in 22% of the Alzheimer's disease patients and in no normals, so presumably this virus either did not reactivate in brain or it elicited only short-lived intrathecal antibodies. The HSV1 results confirm the original PCR findings that show the presence of HSV1 DNA sequences in many elderly brains, and indicate also that the whole functional HSV1 genome is present, and that the virus has replicated.

Human African trypanosomiasis: quantitative and qualitative assessment of intrathecal immune response

Quantitative and qualitative techniques for assessment of the intrathecal humoral immune response in human African trypanosomiasis were compared, and their diagnostic potential for detection of the meningo-encephalitic stage of the disease was evaluated. Total and trypanosome specific immunoglobulin G (IgG) and IgM intrathecal synthesis were studied in paired cerebrospinal fluid (CSF) and blood samples of 38 trypanosomiasis patients and in three controls using Reiber's formulae. The presence of CSF-specific oligoclonal IgG and of trypanosome-specific antibodies was determined using iso-electric focusing followed by immunoblotting and antigen-driven immunoblots. The intrathecal IgG fraction (16% positive) and oligoclonal IgG detection (24% positive) were insensitive for detection of an intrathecal humoral immune response. Trypanosome-specific IgG synthesis, reflected by the IgG antibody index (AI) (26% positive), was confirmed by the presence of oligoclonal specific IgG (47% positive), but the latter was more sensitive. Although the detection technique failed for oligoclonal IgM, the intrathecal IgM fraction (42% positive) and the IgM AI (32% positive) indicated that the meningo-encephalitic stage of the disease is characterized by a dominant intrathecal IgM response, which was higher than the IgG response. The highest combination of diagnostic sensitivity and specificity for the meningo-encephalitic stage of trypanosomiasis was observed for quantitative IgM determinations.

Clinical relevance of polymerase chain reaction (PCR) assays and antigen-driven immunoblots for the diagnosis of neurological infectious diseases

Polymerase chain reaction assays are a powerful tool for detecting the presence of infectious genomes in the cerebrospinal fluid. Positive results always mean a current or pending infection of the central nervous system. Subacute (>7 days) or chronic infections induce an intrathecal humoral immune response and the appearance of oligoclonal IgG antibodies directed against the causal infectious agent. This local synthesis may be observed even in cases of severe systemic immunodeficiency. The use of polymerase chain reactions in combination with the detection of a specific intrathecal immune response should represent the most reliable strategy for the diagnosis of viral and chronic infections of the central nervous system. The authors describe their experience, using this approach, in herpetic encephalitis, acute and recurrent herpetic meningitis, varicella zoster-induced neurological diseases, cytomegalovirus encephalitis, progressive multifocal leukoencephalitis and tuberculous meningitis.

Viliuisk encephalomyelitis: intrathecal synthesis of oligoclonal IgG

Viliuisk encephalomyelitis (VE) is a neurodegenerative disorder expressed as subacute meningo-encephalitis progressing to a more prolonged pan-encephalitic syndrome with a fatal outcome within 1 to 10 years. Some patients survive to a steady state of global dementia and severe spasticity that may last for over 20 years. Multiple micronecrotic foci surrounded by inflammatory infiltrates are observed throughout the cerebral cortex and other gray matter areas. Infectious etiology of VE is strongly suspected, but the causative agent has not been identified. We conducted a search for assays that might be helpful for VE diagnosis and established for the first time that the majority of patients with definite VE show evidence for intrathecal IgG synthesis correlating with the clinical manifestations of the disease. This indicates that the detection of oligoclonal IgG banding in the cerebrospinal fluid is a valuable diagnostic assay for VE. Implications of these findings for a possible etiology of VE are discussed.

Chlamydia pneumoniae in multiple sclerosis: humoral immune responses in serum and cerebrospinal fluid and correlation with disease activity marker

Humoral immune responses to Chlamydia pneumoniae (C. pneumoniae) were studied in paired sera and cerebrospinal fluid (CSF) of patients with definite multiple sclerosis (MS) and other inflammatory and non-inflammatory neurological diseases. Seropositivity was not significantly different between these groups. However, C. pneumoniae-specific IgG titers were significantly higher in CSF of MS than in controls. Sixteen out of 52 seropositive MS patients (30.8%) showed intrathecal synthesis of C. pneumoniae-specific IgG but only one of 43 seropositive controls (2.3%). In MS, this was strongly associated with intrathecal synthesis of polyclonal IgG in 13/16 patients. However, these elevated C. pneumoniae antibody titers in CSF did not significantly correlate with disease duration, disease course, clinical or MRI disease activity, disability or presence of oligoclonal IgG in MS.

Evidence of cerebrospinal fluid free kappa light chains in AIDS patients with Toxoplasma gondii encephalitis

Cerebrospinal fluid (CSF) free light chains of kappa or lambda (FLC kappa/lambda) type were investigated by affinity mediated blotting technique (AMI) and ELISA in 28 patients of which nine with AIDS and Toxoplasma gondii encephalitis (AIDS, TE), 11 with AIDS with or without other CNS AIDS-related opportunistic infections (non-TE AIDS) and eight control patients with or without inflammatory neurological disorders (control group). CSF restricted oligoclonal FLC bands either of k or lambda isotype or both were found by AMI in 18 (90%) out of 20 AIDS patients, while a CSF pattern predominantly characterized by FkappaLC rather than FlambdaLC was observed in eight (88.8%) out of nine TE patients. No FLC components were detected in the matched sera of TE or non-TE AIDS patients or in the CSF and sera from control group. The anti-parasite-specific FkappaLC CSF/serum mean levels and the T. gondii-specific FkappaLC index values were found by ELISA to be significantly more elevated in TE patients when compared to non-TE AIDS or control group. These findings suggest that the increased production of T. gondii-specific FkappaLC could provide insights into pathogenesis of reactivated TE in immunocompromised patients and may have important diagnostic usefulness.

Epstein-Barr virus nuclear antigen-1 (EBNA-1) associated oligoclonal bands in patients with multiple sclerosis

Oligoclonal bands (OCBs) are frequently observed in the cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS), but the target antigens of these antibodies remain unknown. We used antigen specific immunoblotting to determine whether Epstein Barr virus nuclear antigen-1 (EBNA-1) was a target of the OCBs in the CSF of patients with MS. Antibody indices (AIs) were measured by ELISA and calculated by the formula of Reiber and Lange which includes correction factors for both breakdown of the blood brain barrier and intrathecal polyclonal IgG synthesis. A distinctive oligoclonal antigen specific banding pattern for EBNA-1 was observed in 5/15 MS patients, but 0/12 controls (P=0.037, Fisher's Exact Probability). AIs in this EBNA-l positive subgroup were extremely high, comparable with levels observed in viral CNS infections. In one patient with EBNA-1 specific OCBs, EBNA-1 and a peptide 'equivalent', p62, were able to absorb a component of the total IgG. Our results suggest that in a subset of MS patients, EBNA-1 may be a major target of selected OCBs.