Anti-EBNA1/anti-EBNA2 ratio decreases significantly in patients with progression of HIV infection

Epstein-Barr Virus-Specific Humoral Immune Responses in Health and Disease

Epstein-Barr virus (EBV) is widely distributed in the world and associated with a still increasing number of acute, chronic, malignant and autoimmune disease syndromes. Humoral immune responses to EBV have been studied for diagnostic, pathogenic and protective (vaccine) purposes. These studies use a range of methodologies, from cell-based immunofluorescence testing to antibody-diversity analysis using immunoblot and epitope analysis using recombinant or synthetic peptide-scanning. First, the individual EBV antigen complexes (VCA , MA, EA(D), EA(R) and EBNA) are defined at cellular and molecular levels, providing a historic overview. The characteristic antibody responses to these complexes in health and disease are described, and differences are highlighted by clinical examples. Options for EBV vaccination are briefly addressed. For a selected number of immunodominant proteins, in particular EBNA1, the interaction with human antibodies is further detailed at the epitope level, revealing interesting insights for structure, function and immunological aspects, not considered previously. Humoral immune responses against EBV-encoded tumour antigens LMP1, LMP2 and BARF1 are addressed, which provide novel options for targeted immunotherapy. Finally, some considerations on EBV-linked autoimmune diseases are given, and mechanisms of antigen mimicry are briefly discussed. Further analysis of humoral immune responses against EBV in health and disease in carefully selected patient cohorts will open new options for understanding pathogenesis of individual EBV-linked diseases and developing targeted diagnostic and therapeutic approaches.

Atypical prediagnosis Epstein-Barr virus serology restricted to EBV-positive Hodgkin lymphoma

An altered anti-Epstein-Barr virus (EBV) serologic profile preceding diagnosis is associated with an increased risk of Hodgkin lymphoma. It is unknown whether this atypical pattern predicts Hodgkin lymphoma risk further subdivided by determination of EBV in tumor cells. A nested case-control study of 128 incident Hodgkin lymphoma cases and 368 matched controls from active-duty military personnel with archived serum in the US Department of Defense Serum Repository was conducted to determine whether a panel of anti-EBV antibody titers differed in EBV(+) and EBV(-) Hodgkin lymphoma. Among 40 EBV(+) Hodgkin lymphoma cases and matched controls, statistically significant increased risks were associated with elevated anti-EBV VCA IgG antibody titers (relative risk = 3.1; 95% confidence interval [CI], 1.1-8.7), and an anti-EBNA-1/anti-EBNA-2 antibody ratio ≤ 1.0 versus > 1.0 (relative risk = 4.7; 95% CI, 1.6-13.8). In contrast, no significant associations were found among 88 EBV(-) Hodgkin lymphoma cases relative to their matched controls. In case-case analysis, EBV(+) disease was significantly associated with a low anti-EBNA-1/anti-EBNA-2 antibody ratio. This distinctive serologic response to EBV latent antigens, indicative of immune dysfunction in other clinical settings, is associated with an increased risk of developing EBV(+) but not EBV(-) Hodgkin lymphoma.

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.

Antibody titers against EBNA1 and EBNA2 in relation to Hodgkin lymphoma and history of infectious mononucleosis

A role for Epstein Barr virus (EBV) in Hodgkin lymphoma (HL) pathogenesis is supported by the detection of EBV genome in about one-third of HL cases, but is not well defined. We previously reported that an elevated prediagnosis antibody titer against EBV nuclear antigens (EBNA) was the strongest serologic predictor of subsequent HL. For the present analysis, we measured antibody levels against EBNA components EBNA1 and EBNA2 and computed their titer ratio (anti-EBNA1:2) in serum samples from HL cases and healthy siblings. We undertook this analysis to examine whether titer patterns atypical of well-resolved EBV infection, such as an anti-EBNA1:2 ratio ≤ 1.0, simply reflect history of infectious mononucleosis (IM), an HL risk factor, or independently predict HL risk. Participants were selected from a previous population-based case-control study according to their history of IM. We identified 55 EBV-seropositive persons with a history of IM (IM+; 33 HL cases, 22 siblings) and frequency-matched a comparison series of 173 IM history-negative, EBV-seropositive subjects on HL status, gender, age and year of blood draw (IM-; 105 cases, 58 siblings). In multivariate logistic regression models, an anti-EBNA1:2 ratio ≤ 1.0 was significantly more prevalent in HL cases than siblings (odds ratio, 95% confidence interval = 2.43, 1.05-5.65); similar associations were apparent within the IM+ and IM- groups. EBNA antibodies were not significantly associated with IM history in HL cases or siblings. These associations suggest that chronic or more severe EBV infection is a risk factor for HL, independent of IM history.

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.

High Epstein-Barr virus (EBV) DNA loads in HIV-infected patients: correlation with antiretroviral therapy and quantitative EBV serology

OBJECTIVE

To study Epstein-Barr virus (EBV) DNA loads in peripheral blood of HIV carriers to determine base-line values and diagnostic relevance of viral load in relation to quantitative serology; to compare EBV presence in parallel plasma and unfractionated whole blood samples; and to correlate EBV DNA load to HIV, CD4 T-cell counts and HAART.

DESIGN

One-hundred and nine random patients receiving highly active antiretroviral therapy (HAART) during 1999 and 99 patients on anti-HIV monotherapy during 1993-1996 were included.

METHODS

EBV DNA load was determined by quantitative competitive PCR. EBV serology was determined by immunoblot profile and quantitative enzyme-linked immunosorbent assay for responses against VCA-p18 and EBNA-1.

RESULTS

Twenty-two out of 109 patients receiving HAART and 28 out of 99 of patients on anti-HIV monotherapy showed elevated EBV DNA loads in whole blood (> 2000 copies/ml), without elevated loads in parallel plasma. EBV DNA load distribution did not differ between the two groups (P = 0.78) and did not correlate with HIV or CD4 T-cell count. In three patients with high EBV DNA loads EBV RNA was virtually absent. Patients with high EBV DNA loads (3610-89 400 copies/ml) had higher anti-VCA-p18 IgG levels than patients with undetectable EBV DNA (P < 0.0001) but lower anti-EBNA-1 IgG levels (P = 0.005).

CONCLUSION

Absolute values of EBV DNA load may have poor diagnostic value for defining HIV patients at risk for developing EBV-associated disease. Elevated EBV DNA loads are cell-associated and are not influenced by HAART. Increased anti-p18-VCA and decreased anti-EBNA-1 IgG levels in patients with high EBV loads indicate impaired latency control and increased lytic replication suggesting disturbed overall immunosurveillance against EBV.

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.

Altered prevalence and reactivity of anti-Epstein-Barr virus antibodies in patients with multiple sclerosis

In this study, the prevalence and reactivity of anti-Epstein-Barr virus (EBV) antibodies were investigated in 107 patients with multiple sclerosis (MS) in comparison to age- and gender-matched healthy controls from a north German state. We found a significant 100% EBV-seropositivity and a significant lack of primary EBV infections in the MS group, indicating that all MS patients are infected with EBV before the development of MS. Although there were no differences in reactivities of EBV-specific anti-early antigen (EA)-immunoglobulin G (IgG), -IgM, and -IgA antibodies between each group, MS patients had significant lower anti-Epstein-Barr nuclear antigen (EBNA)1-IgG antibody titers as a possible serological sign for a defective control of the persistent latent EBV carrier state and EBV reactivations. Longitudinal studies of MS patients are necessary to further determine the implications of EBV reactivations on the course and disease activity of MS.

The dominant source of CD4+ and CD8+ T-cell activation in HIV infection is antigenic stimulation

To distinguish between antigenic stimulation and CD4+ T-cell homeostasis as the cause of T-cell hyperactivation in HIV infection, we studied T-cell activation in 47 patients before and during highly active antiretroviral therapy (HAART). We show that expression of human leukocyte antigen (HLA)-DR, CD38, and Ki67 on T cells decreased during HAART but remained elevated over normal values until week 48 of therapy. We confirm previous reports that T-cell activation correlates positively with plasma HIV RNA levels (suggesting antigenic stimulation), and negatively with CD4 count (suggesting CD4+ T-cell homeostasis). However, these correlations may be spurious, because misleading, due to the well-established negative correlation between CD4 count and plasma HIV RNA levels. To resolve this conflict, we computed partial correlation coefficients. Correcting for CD4 counts, we show that plasma HIV RNA levels contributed to T-cell hyperactivation. Correcting for plasma HIV RNA levels, we show that CD4+ T-cell depletion contributed to T-cell activation. Correcting for both, activation of CD4+ and CD8+ T cells remained positively correlated. Because this suggests that CD4+ and CD8+ T-cell activation is caused by a common additional factor, we conclude that antigenic stimulation by HIV or other (opportunistic) infections is the most parsimonious explanation for T-cell activation in HIV infection. Persistence of HIV antigens may explain why T-cell activation fails to revert to levels found in healthy individuals after 48 weeks of therapy.