Evaluation of three commercial enzyme-linked immunosorbent assays and two latex agglutination assays for diagnosis of primary Epstein-Barr virus infection

Fever with atypical lymphocytosis: pearls and pitfalls in Epstein-Barr virus serology

The heterophile antibody (also known as the Monospot) test is a useful screening tool for infectious mononucleosis (IM) resulting from primary Epstein-Barr virus (EBV) infection. However, up to 10% of patients with IM are heterophile negative. Heterophile-negative patients who have lymphocytosis or atypical lymphocytes on peripheral blood smear should be further tested for EBV serologies, which include testing for specific IgM and IgG antibodies against viral capsid antigens, early antigens and EBV nuclear antigen proteins. A diagnostic dilemma arises when the patient has clinical and laboratory features of IM, but is both heterophile negative and seronegative for IM, as illustrated in this case presentation. To avoid missed diagnoses of IM, misdiagnosis of mononucleosis-like illnesses and unnecessary testing, knowledge of test characteristics and the evolving course of EBV serologies is important to assure and inform both the physician and the patient.

Diagnosis of nasopharyngeal carcinoma using an ultrasensitive immunoassay method based on nanoparticles

The detection of the antibody of Epstein-Barr virus (EBV) is critical for the diagnosis of nasopharyngeal carcinoma (NPC). An accurate and scalable point-of-care detection method would support the screening, diagnosis, and monitoring of NPC patients. In this study, firstly, we made an antibody enrichment element, antigen-MNPs, which can screen out specific antibodies in a complex sample. Secondly, signal-amplifying elements were synthesized by labelling inorganic quantum dots (QDs) and anti-antibodies on the surface of flop-ferritin. A sandwich structure is formed among antigen-MNPs, target-antibodies, and anti-antibodies-flop-ferritin@QDs. The antibodies are quantified by fluorescence intensity with a limit of detection (LOD) as low as 10^-11 g mL^-1. Moreover, the method can detect different types of antibodies and was employed to examine 10 sera from NPC patients and 10 sera from healthy individuals. The result indicates that the simultaneous detection of anti-EBNA-IgG and anti-EBNA-IgA provides an efficient route for early diagnosis of NPC.

Evaluation of the Serological Point-of-Care Testing of Infectious Mononucleosis by Data of External Quality Control Samples

Timely and reliable laboratory diagnostics is a necessity for patient safety and good patient management. Success in external quality assessment (EQA) reflects on the everyday work in a clinical laboratory. This study evaluated the reliability of serological point-of-care (POC) testing for the Epstein-Barr virus (EBV) that causes infectious mononucleosis (IM). Data from the results of 95 external quality control (EQC) samples, altogether 18 885 results during an eight-year period (2010-2017) were collected from 273 Finnish testing sites. Diagnosing acute infectious mononucleosis (EBV IM) is based on clinical, haematological and serological findings. Heterophile antibody tests are used for this purpose because they can be carried out at POC and are cheap and robust to perform. In this study, the data showed that the testing sites used 3 test methods and 17 different test kits; of the kits, 4 were used during the whole study period. The most commonly used test methods were immunochromatographic assays (12 test kits, 17 959 EQC results). Latex agglutination (4 test kits, 504 results) and immunofiltration test methods (one kit, 422 results) were also used. The overall success rate was 99.3% (for positive samples 99.6%, for negative samples 99.1%). The success rates of the different test methods varied from 94.3% for the immunofiltration method to 99.6% for the latex agglutination method. The lowest success rates were found for negative samples: 82.0% (QuickVue, Quidel [immunochromatographic method]), 91.3% (RDT EBV IgM Assay, Bio-Rad [immunofiltration method]). The results of the negative samples that represented old EBV immunity were the most difficult to interpret with a success rate of 98.9% compared to success rates of clearly positive (99.6%) and negative (99.5%) samples (P < .001). Especially the immunofiltration method (RDT EBV IgM Assay) produced 13.7% false positive results for samples of old immunity. The data showed that 42 of the studied 95 EBV IM EQA rounds were reported as expected (true positive or true negative) by all testing sites.

High-Throughput Incubation and Quantification of Agglutination Assays in a Microfluidic System

In this paper, we present a two-phase microfluidic system capable of incubating and quantifying microbead-based agglutination assays. The microfluidic system is based on a simple fabrication solution, which requires only laboratory tubing filled with carrier oil, driven by negative pressure using a syringe pump. We provide a user-friendly interface, in which a pipette is used to insert single droplets of a 1.25-µL volume into a system that is continuously running and therefore works entirely on demand without the need for stopping, resetting or washing the system. These assays are incubated by highly efficient passive mixing with a sample-to-answer time of 2.5 min, a 5⁻10-fold improvement over traditional agglutination assays. We study system parameters such as channel length, incubation time and flow speed to select optimal assay conditions, using the streptavidin-biotin interaction as a model analyte quantified using optical image processing. We then investigate the effect of changing the concentration of both analyte and microbead concentrations, with a minimum detection limit of 100 ng/mL. The system can be both low- and high-throughput, depending on the rate at which assays are inserted. In our experiments, we were able to easily produce throughputs of 360 assays per hour by simple manual pipetting, which could be increased even further by automation and parallelization. Agglutination assays are a versatile tool, capable of detecting an ever-growing catalog of infectious diseases, proteins and metabolites. A system such as this one is a step towards being able to produce high-throughput microfluidic diagnostic solutions with widespread adoption. The development of analytical techniques in the microfluidic format, such as the one presented in this work, is an important step in being able to continuously monitor the performance and microfluidic outputs of organ-on-chip devices.

False-Positive Monospot in a Returning Traveler with Dengue Fever

The heterophile antibody (Monospot), initial test of choice for Epstein-Barr virus (EBV)-associated infectious mononucleosis, is both sensitive (70-92%) and specific (96-100%). False positives have been demonstrated in cases of viral hepatitis, human immunodeficiency virus, leukemia, lymphoma, pancreatic cancer, systemic lupus erythematosus, and rubella. We present a case of a 46-yr-old male who developed fever, chills, headaches, myalgia, fatigue, and photophobia 1 d after returning from the Philippines. He demonstrated a mild transaminitis and significant thrombocytopenia (12,000 cells/μL). His initial evaluation revealed a positive heterophile antibody test. Without a classic EBV presentation, a fever in returning traveler evaluation was instituted resulting in a positive dengue test by direct fluorescence IgM (8.82 IU) and IgG (7.13 IU), respectively. Both his EBV DNA polymerase chain reaction and IgM by viral capsid antigen were negative. Dengue, an RNA flavivirus, and the dengue antibody have demonstrated cross-reactivity with other flaviviruses including Japanese encephalitis virus, yellow fever virus, West Nile virus, and St. Louis encephalitis. However, EBV is a double-helix DNA herpesvirus and structurally very different. To our knowledge, this is the first reported case of cross-reactivity between dengue and EBV that describes a potential false positive for the heterophile antibody test.

Infectious diseases

The measurement of biochemical parameters such as blood glucose, blood gases, electrolytes and cardiac markers have particularly benefited from recent advances in POCT. More and more, this form of analysis is now positively impacting the field of infectious diseases. Many microbiological POCT systems tend to be designed as rapid tests. In general, such tests can be carried out in a few simple steps by medical assistants or physicians without laboratory equipment or laboratory experience. It is even possible for the patients themselves to perform a series of such tests.

Serological diagnosis of Epstein-Barr virus infection: Problems and solutions

Serological tests for antibodies specific for Epstein-Barr virus (EBV) antigens are frequently used to define infection status and for the differential diagnosis of other pathogens responsible for mononucleosis syndrome. Using only three parameters [viral capsid antigen (VCA) IgG, VCA IgM and EBV nuclear antigen (EBNA)-1 IgG],it is normally possible to distinguish acute from past infection: the presence of VCA IgM and VCA IgG without EBNA-1 IgG indicates acute infection, whereas the presence of VCA IgG and EBNA-1 IgG without VCA IgM is typical of past infection. However, serological findings may sometimes be difficult to interpret as VCA IgG can be present without VCA IgM or EBNA-1 IgG in cases of acute or past infection, or all the three parameters may be detected simultaneously in the case of recent infection or during the course of reactivation. A profile of isolated EBNA-1 IgG may also create some doubts. In order to interpret these patterns correctly, it is necessary to determine IgG avidity, identify anti-EBV IgG and IgM antibodies by immunoblotting, and look for heterophile antibodies, anti-EA (D) antibodies or viral genome using molecular biology methods. These tests make it possible to define the status of the infection and solve any problems that may arise in routine laboratory practice.

Epstein-Barr virus serologic abnormalities and risk of rheumatoid arthritis among women

BACKGROUND

Epstein-Barr virus (EBV) infection and the immune response may be involved in the pathogenesis of rheumatoid arthritis (RA). Past studies have suggested an association between EBV and RA.

METHODS

We studied the association between EBV serologies and RA risk in a nested case-control study in the Nurses' Health Study (NHS) cohorts. We confirmed incident RA cases from 1990 to 2002 by questionnaire and medical record review. Each incident case with blood collected prior to RA symptoms was matched with a healthy participant by time of day and date of blood collection, birth year, menopausal status and postmenopausal hormone use. Immunofluorescence assays measured serologic EBV responses: viral capsid antigen, early-antigen-diffuse and early antigen-complex (restricted and diffuse), Epstein Barr nuclear antigen (EBNA)-1, EBNA-2 and cytomegalovirus (CMV), as control. All were reported as titers, except CMV, which was reported as positive or negative. Antinuclear antibody positive samples were excluded. Elevated EBV antibody titers were defined as the upper 20% (or nearest titer) among controls. Conditional logistic regression analyses modeled RA risk associated with elevated EBV titers or the presence/absence of CMV, further adjusted for pack-years smoking and alcohol intake.

RESULTS

Eighty-seven incident RA cases were identified. Mean time to RA after blood draw was 6.2 (± 3.5) years in NHS and 1.9 (± 0.6) years in NHS II. Antibody titers against EBV were not significantly different between pre-RA cases and controls.

CONCLUSIONS

In this prospective study of women, we observed no association between EBV serologies and RA risk.

Antiviral treatment for severe EBV infections in apparently immunocompetent patients

BACKGROUND

Infectious mononucleosis usually runs a mild self-limiting course. Complications arise rarely and when so, corticosteroids are the mainstay of their treatment. The role of antivirals in the management of severe EBV infections is debatable.

METHODS

We sought to review the usage of antivirals for severe EBV infection in apparently immunocompetent patients. For this reason a search in PubMed and Scopus was performed for the time period from 1982 to 2009.

RESULTS

45 patients with severe manifestations of infectious mononucleosis received antivirals (as an adjunct to steroids in 26 of them). Specifically 21 patients with CNS involvement (meningoencephalitis, cerebellitis), 4 with peripheral nervous system involvement (Guillain-Barré, myeloradiculitis, facial nerve palsy), 5 with hepatitis and 15 with other afflictions (including adult respiratory distress syndrome, thrombocytopenia, aplastic anemia, acute renal failure, ulcerations, myocarditis, and frosted branch vasculitis) received antiviral medications. Thirty-nine out of these 45 patients had a favourable outcome (27 were cured and 12 showed clinical improvement) while 6 patients died. The most commonly prescribed antiviral regimen was acyclovir monotherapy (35 patients). Three patients received combinations of acyclovir with other antivirals and 1 received famciclovir. Three patients received ganciclovir monotherapy, 1 ganciclovir plus foscarnet, 1 foscarnet and 1 vidarabine.

CONCLUSION

The available data derive from case reports and case series and thus the deduction of conclusions regarding the effect, if any, of antiviral treatment is debatable. However, physicians may consider using antiviral agents in severe manifestations of EBV infections in immunocompetent patients as an adjunct to steroid treatment.

Search for Anti-EA(D) Antibodies in Subjects with an "Isolated VCA IgG" Pattern

The presence of an “isolated viral capsid antigen (VCA) IgG” pattern in serum is not easy to interpret without the aid of further tests, such as specific immunoblotting or a virus genome search, that often give rise to organisational and economic problems. However, one alternative is to use an enzyme-linked immunosorbent assay (ELISA) to detect anti-early antigen (EA) antibodies, which can be found in about 85% of subjects with acute Epstein-Barr virus (EBV) infections. The purpose of this work was to search for anti-EA(D) antibodies in 130 samples with an isolated VCA IgG pattern at ELISA screening and classified as being indicative of past (102 cases) or acute (28 cases) infection on the basis of the immunoblotting results. Thirty-seven samples (28.5%) were positive for anti-EA(D), of which 25 (89.3%) had been classified by immunoblotting as indicating acute and 12 (11.8%) past EBV infection. This difference was statistically significant (P < .01). The results of our search for anti-EA(D) antibodies correctly identified nearly 90% of acute (presence) or past EBV infections (absence). When other tests are not available, the search for anti-EA antibodies may therefore be helpful in diagnosing patients with an isolated VCA IgG pattern at screening tests.

The Effect of Antiretroviral Combination Treatment on Epstein-Barr Virus (EBV) Genome Load in HIV-Infected Patients

We evaluated the effect of combination anti-retroviral treatment (cART) on the host control of EBV infection in moderately immunosuppressed HIV-1 patients. Twenty HIV-1 infected individuals were followed for five years with repeated measurements of EBV DNA load in peripheral blood lymphocytes in relation to HIV-RNA titers and CD4+ cell counts. Individuals with optimal response, i.e. durable non-detectable HIV-RNA, showed a decline of EBV load to the level of healthy controls. Individuals with non-optimal HIV-1 control did not restore their EBV control. Long-lasting suppression of HIV-replication after early initiation of cART is a prerequisite for re-establishing the immune control of EBV.

Seroepidemiology of EBV and interpretation of the "isolated VCA IgG" pattern

The presence of VCA IgG in the absence of VCA IgM and EBNA-1 IgG antibodies makes classifying EBV infection more difficult as this serological picture can be seen in the case of past infection with EBNA-1 IgG loss or non-appearance, or acute infections with the early disappearance or delayed onset of VCA IgM. The aim of this study was to assess the prevalence of this pattern in 2,422 outpatients with suspected EBV infection examined in 2005-2006, and to interpret its significance by means of immunoblotting. One hundred and seventy-seven (7.3%) of the patients were VCA IgG-positive, VCA IgM-negative and EBNA-1 IgG-negative, 15 of whom (8.5%) presented with heterophile antibodies. Analysis by age class showed that the prevalence of isolated VCA IgG ranged from 4.5% in the subjects aged 1-10 years to 9% in those aged >60 years. Immunoblotting allowed 18.9% of the cases to be classified as acute and 81.1% as past infections, the latter being observed in about 37% of the patients aged less than 10 years and in 100% of those aged >30 years. Therefore, in our case series, the presence of isolated VCA IgG was associated usually with past infection, particularly among adults. In children aged less than 10 years, it was associated mainly with acute infection but as past infection may be present in about one-third of such children, this possibility should not be overlooked.

Display of a peptide mimotope on a crystalline bacterial cell surface layer (S-layer) lattice for diagnosis of Epstein-Barr virus infection

Fusion proteins based on the crystalline bacterial cell surface layer (S-layer) proteins SbpA from Bacillus sphaericus CCM 2177 and SbsB from Geobacillus stearothermophilus PV72/p2 and a peptide mimotope F1 that mimics an immunodominant epitope of Epstein-Barr virus (EBV) were designed and overexpressed in Escherichia coli. Constructs were designed such that the peptide mimotope was presented either at the C-terminus (SbpA/F1) or at the N-terminus (SbsB/F1) of the respective S-layer proteins. The resulting S-layer fusion proteins, SbpA/F1 and SbsB/F1, fully retained the intrinsic self-assembly capability of the S-layer moiety into monomolecular lattices. As determined by immunodot assays and ELISAs using monoclonal antibodies, the F1 mimotope was well-presented on the outer surface of the S-layer lattices and accessible for antibody binding. Further comparison of the two S-layer fusion proteins showed that the S-layer fusion protein SbpA/F1 had a higher antibody binding capacity than SbsB/F1 in aqueous solution and in immune sera, illustrating the importance of epitope orientation on the performance of solid-phase immunoassays. To assess the diagnostic values of S-layer mimotope fusion protein SbpA/F1, we screened a panel of 83 individual EBV IgM-positive, EBV negative, and potential cross-reactive sera for their reactivities. This resulted in 98.2% specificity and 89.3% sensitivity, and furthermore no cross-reactivity with related viral disease states including rheumatoid factor was observed. This study shows the potential of S-layer fusion proteins as a matrix for site-directed immobilization of small ligands in solid-phase immunoassays using EBV diagnostics as a model system.

Changes in seroprevalence to four herpesviruses over 30 years in Swedish children aged 9–12 years

BACKGROUND

Changing social conditions and life-styles in Sweden may have affected the spread of varicella-zoster virus (VZV), herpes simplex virus (HSV), cytomegalovirus (CMV), and Epstein-Barr virus (EBV).

OBJECTIVES

To study possible changes over 30 years in prevalence of antibodies against VZV, HSV, CMV, and EBV in Swedish children, using modern serological methods.

STUDY DESIGN

Serum samples from 819 Swedish children who were 9-12 years old in 1967-1968, in 1977-1978 (two cohorts), and in 1997, respectively, were examined. IgG antibodies against VZV, HSV, and CMV were measured by well validated enzyme-linked immunosorbent assays and against EBV by indirect immunoflourescense.

RESULTS

The seropositivity for VZV for 9-12 years old children was 50% in 1967-1968, 74-82% in 1977-1978, and 98% in 1997. The corresponding figures were 31%, 53%, 50%, and 58% for CMV, 35%, 35%, 32%, and 38% for HSV, and 64% in 1967-1968 and in 1977-1978 (both cohorts), and 62% in 1997 for EBV.

CONCLUSIONS

The seroprevalence for VZV increased significantly from 1967-1968 to 1997, and there was also a significant but smaller increase in the CMV seroprevalence, while seroprevalence to HSV and EBV remained relatively stable.

Human herpesvirus 8--a novel human pathogen

In 1994, Chang and Moore reported on the latest of the gammaherpesviruses to infect humans, human herpesvirus 8 (HHV-8) [1]. This novel herpesvirus has and continues to present challenges to define its scope of involvement in human disease. In this review, aspects of HHV-8 infection are discussed, such as, the human immune response, viral pathogenesis and transmission, viral disease entities, and the virus's epidemiology with an emphasis on HHV-8 diagnostics.

Evaluation of a multiplexed bead assay for assessment of Epstein-Barr virus immunologic status

Currently, serological assays using either indirect immunofluorescence assay or enzyme-linked immunosorbent assay (ELISA) are performed to evaluate the status of Epstein-Barr virus (EBV) infection in humans. Although these methods are reliable, they are limited to testing an antibody response to a single viral antigen per reaction, thus necessitating a panel of assays to complete the evaluation. In contrast, a new bead-based method (BioPlex 2200; Bio-Rad Laboratories, Hercules, Calif.) can analyze the humoral response to multiple antigens in a single tube. This approach potentially reduces overall cost, turnaround time, and sample volume. The aim of this study was to evaluate the multiplexed EBV serologic assays performed on the BioPlex 2200 platform compared to results of conventional heterophile and ELISA-based assays. A total of 167 nonconsecutive, stored serum samples from adult and pediatric patients submitted for EBV serologic studies were used in the evaluation. Concordance between results generated by the BioPlex 2200 system and conventional assays was calculated. The anti-EA-D assay had the lowest concordance at 91%. The BioPlex 2200 system showed 97% agreement with conventional heterophile and anti-nuclear antigen assays and 92% agreement with the anti-VCA IgG and immunoglobulin M assays. Agreement between the BioPlex 2200 system and conventional testing was 92% with respect to categorization of acute versus nonacute EBV disease. The correlation between these two systems with regard to assignment into one of four categories of EBV status was also good (82%). In summary, there is excellent correlation between contemporary EBV serologic testing and the BioPlex 2200 system.

Evaluation of four commercially available Epstein-Barr virus enzyme immunoassays with an immunofluorescence assay as the reference method

Four commercially available enzyme immunoassays (EIAs) (Novitec, Biotest, Virotech, and DiaSorin) were evaluated, with an indirect immunofluorescence assay as the reference method, for Epstein-Barr virus (EBV) VCA (viral capsid antigen) immunoglobulin G (IgG), VCA IgM, or EBNA (EBV nuclear antigen) IgG at three different locations (Homburg, Stuttgart, and Dresden). Serum samples from 66 immunocompetent patients with infectious mononucleosis, 73 patients without prior EBV infection, and 96 patients with past EBV infections and 29 serum samples with possible cross-reactions to other herpesviruses were included. In addition, 25 samples from an extensively pretested panel that is commercially available (Boston Biomedica) were tested. Each sample was tested at only one location. The four EIAs varied considerably in performance. When analyzing for EBV diagnosis, the Novitec assay performed the best, with 4.9% discrepant diagnoses, followed by the Biotest, Virotech, and DiaSorin assays, with 6.8, 11.7, and 14.0% discrepant diagnoses, respectively. On the basis of single-parameter analysis, the Novitec assay also showed the lowest number of discrepant results, with 3.5%, compared with the Virotech, Biotest, and DiaSorin assays, which produced 5.4, 6.4, and 8.6% discrepant results, respectively. VCA assays using affinity-purified native antigens performed better than assays with recombinant or synthetic antigens. The synthetic EBNA-1s showed the lowest concordance with the reference compared to recombinant p72. Commercially available EBV EIAs differed considerably in performance; however, some proved to be reliable and convenient alternatives to the indirect immunofluorescence assay for routine diagnostics. Native antigens, rather than synthetic peptides, are favored for EBV serology testing.

Use of real-time PCR to measure Epstein-Barr virus genomes in whole blood

The measurement of the Epstein-Barr viral load in peripheral blood has been recognised as an important way of monitoring the response to treatment in patients with Epstein-Barr virus (EBV)-related malignancies. In particular, EBV load in transplant recipients can be used as a predictive parameter for Post-transplant Lymphoproliferative Disorder (PTLD). The aim was to develop a rapid and reliable PCR protocol for the quantification of the cell-associated EBV genome. Real-time PCR using TaqMan methodology was established. This technique was applied to determine the EBV load in various study groups including healthy controls, transplant recipients, patients on haemodialysis, and patients with infectious mononucleosis. The baseline level of EBV genomes in the immunosuppressed renal transplant recipients was significantly different from that in the healthy controls.

A systematic study of Epstein-Barr virus serologic assays following acute infection

We determined the presence of IgG and IgM antibody to viral capsid antigen (VCA-IgG, VCA-IgM) and IgG antibody to the Epstein-Barr virus nuclear antigen (EBNA) by indirect immunofluorescence assay (IFA) and enzyme-linked immunosorbent assay (ELISA) during the acute illness and at 1, 2, 6, and 48 months in a prospective population-based case series of 95 persons with an acute illness serologically confirmed as Epstein-Barr virus infection. The acute illness was characterized by the presence of VCA-IgG and VCA-IgM (by ELISA) and by the absence of EBNA in most, but not all, patients. During follow-up, VCA-IgG antibodies remained detectable in all patients, while the proportion with VCA-IgM declined and the number with detectable EBNA antibodies steadily increased. The primary differences between the 2 serologic test methods were the increased persistence of VCA-IgM during follow-up by ELISA and the earlier detection of EBNA by IFA. Clinicians should consider the illness stage and the laboratory technique to appropriately interpret serologic test results in suspected cases of mononucleosis caused by the Epstein-Barr virus.

Application of virus-specific immunoglobulin M (IgM), IgG, and IgA antibody detection with a polyantigenic enzyme-linked immunosorbent assay for diagnosis of Epstein-Barr virus infections in childhood

The Enzygnost anti-Epstein-Barr virus enzyme-linked immunosorbent assay (ELISA) system, which is based on a defined antigen mixture and on detection of antibodies of the immunoglobulin G (IgG), IgM, and IgA classes, was evaluated for its reliability in diagnosing Epstein-Barr virus infections in childhood. With samples from 66 children, the Epstein-Barr virus status and the infection phase were defined by indirect immunofluorescence and anticomplement fluorescence assays: 11 children were seronegative, 8 had a primary infection, 20 had a recent primary or past infection, and in 27 a reactivated Epstein-Barr virus infection was diagnosed. When applying the Enzygnost ELISAs, 15 serum samples (22.7%) were not interpretable due to indeterminate results in at least one of the assays used and were therefore excluded from further evaluation. The respective sensitivities and specificities for the diagnosis of seronegativity were 100 and 100%, those for the diagnosis of primary infection were 100 and 97%, those for the diagnosis of recent primary or past infection were 100 and 52%, and those for the diagnosis of reactivated infection were 10 and 100%. This poor performance of the Enzygnost system with reactivated infections is due to the prerequisite of an IgG antibody value of >650 IU/ml for the diagnosis of viral activity, which was fulfilled in only two of the children. Despite the high rate of indeterminate results, the Enzygnost system is useful in diagnosing acute and past Epstein-Barr virus infection in childhood. For serological diagnosis of viral activity in childhood, a supplementary assay is necessary.

Evaluation of a recombinant line blot for diagnosis of Epstein-Barr Virus compared with ELISA, using immunofluorescence as reference method

A commercial line blot using recombinant antigens was compared with a commercial ELISA and 'in-house' IFA (reference test). Two panels were evaluated: Panel A was selected to distinguish between primary infections (89), past infections (20) and seronegatives (8) in immunocompetent individuals. In panel B, patients with a high number of reactivations were included: immunosuppressed patients (37), lymphoma (19), nasopharyngeal carcinoma (10), chronic fatigue syndrome (14). Blood donors (43) and cross-reactive sera (29) were added as controls. Line blot and IFA were concordant in 94% of primary infections, 100% of seronegatives and 100% of past infections, similar to ELISA. Results differed significantly with regard to reactivations. When compared with IFA, the incidence of reactivations was overestimated by the blot, 24 and 58% in blood donors and cross-reactive sera, respectively. ELISA showed a similar problems with 21 and 34% indeterminate results, respectively. The line blot is easy to carry out, has a good concordance with the reference IFA for primary infections, and is, therefore, a sufficient choice for distinguishing primary infection from seronegative and past infection. EBV reactivation assessment will require other methods such as EBV viral load.

Serological diagnosis of Epstein-Barr virus infection by novel ELISAs based on recombinant capsid antigens p23 and p18

A new pair of Epstein-Barr virus ELISAs (Biotest Anti-EBV VCA IgG and VCA IgM ELISA) was evaluated for usefulness for routine diagnosis of acute EBV infections. The ELISAs are based on two viral capsid antigens (VCA), p23 (BLRF2, full-length) and p18 (BFRF3, carboxy-half), that are combined by autologous gene fusion. In total, 179 sera were tested in direct comparison with classical VCA immunofluorescence assays (IFA). With the help of clinical data and additional reference serology, i.e., heterophile antibodies, anti-EA IgG (IFA) and anti-EBNA-1 IgG (ELISA), the patients were divided into the following categories: seronegatives (46), acute primary infections (67), previous infections (39), suspected reactivations (20) and constellations with intermediate serological patterns (7). The VCA IgG and VCA IgM ELISAs showed overall agreement to IFA of 95.0% and 94.4%, respectively. The calculated analytical performance (sensitivity; specificity) of VCA IgG and VCA IgM was 94.0%; 97.8% and 97.1%; 96.5%, respectively. A certain delay in seroconversion of anti-p23-p18 IgG may account for a significant difference in sensitivity of the VCA IgG ELISA between primary (88.4%) and previous infections (100%). In summary, the new recombinant VCA ELISAs yielded good correlation to VCA IFA and in combination with EBNA-1 IgG allow rapid, sensitive, and specific diagnosis of infectious mononucleosis or EBV immune status in general.

Molecular diagnosis of Epstein-Barr virus-related diseases

Epstein-Barr virus (EBV) is the causative agent of infectious mononucleosis, and it may also be found in a wide variety of benign and malignant lesions including oral hairy leukoplakia, inflammatory pseudotumor, Hodgkin's disease, non-Hodgkin's lymphoma, nasopharyngeal carcinoma, and gastric carcinoma. Molecular testing is increasingly important in the diagnosis and monitoring of patients affected by these diseases. In biopsy tissues, molecular detection of EBV-encoded RNA transcripts by in situ hybridization remains the gold standard for proving that a histopathological lesion is EBV-related. EBV-encoded RNA hybridization and EBV LMP1 immunostains are used routinely to detect latent EBV in tissues affected by posttransplant lymphoproliferative disorder (PTLD) or in enlarged nodes from patients with infectious mononucleosis. Traditional serology is the best test for evaluating acute versus remote infection in healthy individuals. High serological titers serve as a tumor marker for some EBV-related malignancies, but titers are not a dependable tumor marker in immunocompromised hosts. EBV viral load testing by quantitative DNA amplification of blood samples is a promising new laboratory test that has proven useful for early diagnosis and monitoring patients with PTLD. Recent studies suggest a role for EBV viral load testing in nasopharyngeal carcinoma, Hodgkin's disease, and AIDS patients with brain lymphoma. Further research is needed to define more fully the clinical utility of viral load tests in the full spectrum of EBV-associated diseases. Gene expression profiling is on the horizon as a means to improve subclassification of EBV-related diseases and to predict response to therapy.

Association between clinical disease activity and Epstein-Barr virus reactivation in MS

OBJECTIVE

To assess the potential significance of Epstein-Barr virus (EBV) reactivation in disease activity in MS patients.

METHODS

The prevalence of antibodies against herpes simplex virus type 1 (HSV-1), HSV-2, EBV, and cytomegalovirus was determined in a group of 108 MS patients and in 163 healthy control subjects. Sera were analyzed using combinations of novel assay systems employing highly purified viral and recombinant antigens. In addition, PCR for the detection of EBV DNA was performed in serial samples.

RESULTS

In contrast to the control populations, antibodies against EBV were present in 100% of MS patients. Among the tested human herpesviruses, this high extent of seropositivity was only found for EBV. Primary infection was found exclusively in the control group (3.7%), whereas serologic evidence of EBV reactivation was seen in MS patients (13. 9%) as well as control subjects (17.2%). There was no temporal coincidence between EBV reactivation and disease activity in MS patients. However, in 19 patients followed monthly for 1 year, active viral replication as measured by increased immunoglobulin (Ig) M and IgA responses to EBV early antigens (p54 + p138) and positive serum DNA was seen in 72.7% of patients with exacerbations during the study period and in none of the patients with clinically stable disease.

CONCLUSIONS

The results demonstrate an association between EBV reactivation and disease activity in MS patients over time, and suggest that EBV might play an indirect role in MS as an activator of the underlying disease process.

Evaluation of 12 commercial tests for detection of Epstein-Barr virus-specific and heterophile antibodies

Ten microbiological departments in Norway have participated in a multicenter evaluation of the following commercial tests for detection of Epstein-Barr virus (EBV)-specific and heterophile antibodies: CAPTIA Select viral capsid antigen (VCA)-M/G/EBNA (Centocor Inc.), Enzygnost anti-EBV/immunoglobulin M (IgM) and IgG (Dade Behring), Vironostika EBV VCA IgM/IgG/EBNA enzyme-linked immunosorbent assay (ELISA) (Organon Teknika), SEROFLUOR immunofluorescence assay and EBV Combi-Test (Institute Virion Ltd.), anti-EBV recombinant IgM- and IgG-early antigen/EBNA IgG ELISA (Biotest Diagnostics), EBV IgM/IgG/EBNA ELISA (Gull Laboratories), Paul-Bunnell-Davidsohn test (Sanofi Diagnostics Pasteur), Monosticon Dri-Dot (Organon Teknika), Avitex-IM (Omega Diagnostics Ltd.), Alexon Serascan infectious mononucleosis test (Alexon Biomedical Inc. ), Clearview IM (Unipath Ltd.), and Cards+/-OS Mono (Pacific Biotech, Inc.). The test panel included sera from patients with primary EBV infection, immunocompromised patients with recent cytomegalovirus infection, healthy persons (blood donors), and EBV-seronegative persons. Among the tests for EBV-specific antibodies the sensitivity was good, with only small differences between the different assays. However, there was a greater variation in specificity, which varied between 100% (Enzygnost) and 86% (Biotest). Tests for detection of heterophile antibodies based on purified or selected antigen (Avitex, Alexon, Clearview IM, and Cards+/-OS Mono) were more sensitive than the Paul-Bunnell-Davidsohn and Monosticon tests.

Novel immunoblot assay using four recombinant antigens for diagnosis of Epstein-Barr virus primary infection and reactivation

A new immunoblot assay, composed of four Epstein-Barr virus (EBV)-encoded recombinant proteins (virus capsid antigen [VCA] p23, early antigen [EA] p138, EA p54, and EBNA-1 p72), was compared with an immunofluorescence assay on a total of 291 sera. The test was accurate in 94.5% of cases of primary EBV infection, while an immunoglobulin G anti-VCA p23 band with strong intensity correlated with reactivation.

Comparative evaluation of the use of immunoblots and of IgG avidity assays as confirmatory tests for the diagnosis of acute EBV infections

BACKGROUND

Despite the availability of several different markers for Epstein--Barr virus (EBV) serology, the EBV status of some patients cannot be resolved from a single serum sample with routine testing. To avoid the requirement of follow-up samples, supplementary tests have to be used in these cases.

OBJECTIVE

To evaluate the usefulness of avidity and immunoblot assays as supplementary tests for the diagnosis of acute EBV infections.

STUDY DESIGN

Three groups of samples for which a definite diagnosis on the EBV status could not be obtained with the routine serological tests were further examined by an EBV IgG avidity assay, by an immunoblot based on a lysate of EBV infected cells, and by a second immunoblot based on recombinant EBV antigens. The three groups consisted of 38 samples with negative/borderline EB nuclear antigen 1 (EBNA-1) antibodies, negative/borderline EBV IgM and positive EBV IgG; 10 samples with indeterminate EBNA-1 and/or EBV IgM assays because of control antigen reactions; and 4 samples with positive EBV IgM results that were not plausible.

RESULTS

The avidity assay differentiated between acute and past infections for all samples. In contrast, some cases remained unresolved with both the recombinant and the lysate immunoblot. Two samples were incorrectly classified with the lysate immunoblot. Interpretation of the lysate immunoblot banding patterns was complicated when anticellular antibodies were present.

CONCLUSION

Avidity testing appears to be the confirmatory method of choice to differentiate between acute and past EBV infections.