Avidity of EBV VCA-specific IgG antibodies: distinction between recent primary infection, past infection and reactivation

Dimethyl Fumarate Treatment Reduces the Amount but Not the Avidity of the Epstein-Barr Virus Capsid-Antigen-Specific Antibody Response in Multiple Sclerosis: A Pilot Study

(1) Multiple sclerosis (MS) is a chronic inflammatory disease of autoimmune origin. The Epstein−Barr virus (EBV) is associated with the onset of MS, as almost all patients have high levels of EBV-specific antibodies as a result of a previous infection. We evaluated longitudinally the effects of dimethyl fumarate (DMF), a first-line treatment of MS, on the quantity and quality of EBV-specific IgG in MS patients. (2) Serum samples from 17 MS patients receiving DMF were taken before therapy (T0) and after 1 week (T1) and 1 (T2), 3 (T3) and 6 (T4) months of treatment. Anti-EBV nuclear antigen (EBNA)-1 and capsid antigen (CA) IgG levels and anti-CA IgG avidity were measured in all samples. (3) Serum levels of anti-CA IgG were lower at T1 (p = 0.0341), T2 (p = 0.0034), T3 (p < 0.0001) and T4 (p = 0.0023) than T0. These differences were partially confirmed also in anti-EBNA-1 IgG levels (T3 vs. T0, p = 0.0034). All patients had high-avidity anti-CA IgG at T0, and no changes were observed during therapy. (4): DMF can reduce the amount but not the avidity of the anti-EBV humoral immune response in MS patients from the very early stages of treatment.

Hemophagocytic Lymphohistiocytosis Following BNT162b2 mRNA COVID-19 Vaccination

Although serious adverse events have remained uncommon, cases of myocarditis induced by messenger RNA (mRNA) COVID-19 vaccines have been reported. Here, we presented a rare but potentially fatal disorder, hemophagocytic lymphohistiocytosis, in a 14-year-old previously healthy adolescent after BNT162b2 mRNA vaccination. The initial evaluation showed splenomegaly, pancytopenia, hyperferritinemia, and hypofibrinogenemia. Further examination revealed positive blood EBV DNA, and other infectious pathogen surveys were all negative. Hemophagocytosis was observed in the bone marrow aspiration and biopsy. HLH was confirmed and intravenous immunoglobulin (IVIG) and methylprednisolone pulse therapy were given. Venoarterial extracorporeal membrane oxygenation (VA-ECMO) was set up for cardiopulmonary support for 3 days due to profound hypotension. The patient was kept on oral prednisolone treatment for 28 days with the following gradual tapering. The hemogram and inflammatory biomarkers gradually returned to normal, and the patient was discharged. The fulminant presentation of HLH in our case could be the net result of both acute immunostimulation after COVID-19 vaccination and EBV infection. Our case suggests that the immune activation after COVID-19 vaccination is likely to interfere with the adequate immune response to certain infectious pathogens, resulting in a hyperinflammatory syndrome.

Role of serum EBV-VCA IgG detection in assessing gastric cancer risk and prognosis in Northern Chinese population

The study aimed to investigate the role of serum EBV‐VCA IgG in assessing gastric cancer (GC) risk and prognosis. A total of 1790 Northern Chinese participants with pathologically confirmed disease underwent EBV‐VCA IgG serologic testing using enzyme‐linked immunosorbent assay (ELISA), including 821 controls, 410 atrophic gastritis (AG) patients, and 559 GC patients. We found that positive EBV‐VCA IgG was significantly associated with GC and its precursor, conferring a 1.55‐ and 1.36‐fold increased risk of GC and AG, respectively (P = 0.001, 95% CI = 1.21‐1.99; P = 0.011, 95% CI = 1.07‐1.72, respectively). The risk effects were more remarkable in younger, female, and Helicobacter pylori‐negative individuals than in older, male, and H. pylori‐positive individuals. EBV‐VCA IgG‐positive subjects had a lower PGI/II ratio than EBV‐VCA IgG‐negative subjects (median 8.0 vs 8.8, P = 0.001), especially those in the H. pylori‐positive (median 6.1 vs 6.8, P = 0.027) and GC subgroups (median 6.4 vs 7.9, P = 0.020). In the intestinal GC subgroup, the survival of EBV‐VCA IgG‐positive patients was worse than that of EBV‐VCA IgG‐negative patients (P = 0.041, HR = 2.45, 95% CI = 1.04‐5.78). Our study suggests that EBV‐VCA IgG seropositivity has potential in predicting the risk of GC and its precursor as well as the prognosis of histologically classified GC.

This is an innovative report about the role of serum EBV‐VCA IgG detection in assessing the risk of gastric cancer (GC) and its precursor as well as GC prognosis. And this is the first report about the relationship between EBV‐VCA IgG serology assay and gastric function status. Our study provides theoretical and experimental basis for evaluating the potential of serum EBV‐VCA IgG as a biomarker in prediction of GC risk and prognosis.

Possible infectious causes of spontaneous splenic rupture: a case report

Introduction

Spontaneous atraumatic splenic rupture is a rare but dramatic occurrence that is most commonly attributed to infection or neoplasia. Deciphering the etiology can be challenging with many cases remaining unclear despite full investigation.

Case presentation

We report the case of a previously healthy and immunocompetent 52-year-old Caucasian woman with a remote history of clinically diagnosed infectious mononucleosis who experienced sudden atraumatic splenic rupture after an untreated stray cat bite.

Conclusions

The differential diagnosis for atraumatic splenic rupture, specifically its infectious causes, is reviewed. Key clinical and laboratory findings that differentiate Bartonella henselae infection and Epstein–Barr virus reinfection are reviewed.

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.

The role of IgG avidity determination in diagnosis of Epstein-Barr virus infection in immunocompetent and immunocompromised patients

There is a high degree of variability in the serologic response to Epstein-Barr virus (EBV) infection, especially in viral capsid antigen (VCA)-IgM antibodies. Therefore, additional tests are needed to confirm primary infection. We evaluated the value of IgG avidity determination in diagnosis of EBV infection in immunocompetent and immunocompromised patients. A total of 236 serum samples from immunocompetent patients with symptoms suggestive of EBV infection were tested for the presence of VCA-IgM/IgG antibodies and IgG avidity. Using IgG avidity, acute primary infection was confirmed in 56.7% of the immunocompetent patients with positive and in 1.8% of patients with negative VCA-IgM. Recent primary infection was documented in 8.9% of the IgM positive and 3.5% of the IgM negative patients. In patients with indeterminate serology (equivocal IgM), 6.7% were classified by avidity index (AI) as acute primary infection, 10.0% as post-acute and 83.3% as past infection cases. Concerning the 32 immunocompromised patients, recent primary infection was documented in 3 of the 14 IgM positive patients. High AI was detected in 11 of these patients, indicating an IgM response due to reactivation. Determination of IgG avidity in combination with classical serologic markers seems to be a reliable method to confirm primary infection both in immunocompetent and immunocompromised patients. It may be especially useful to differentiate cases of primary infection in patients with undetectable VCA-IgM antibodies or indeterminate routine EBV serology.

Epstein-Barr virus and breast cancer: serological study in a high-incidence area of nasopharyngeal carcinoma

We investigated IgA and IgG levels against EBV viral capsid antigen (VCA) and nuclear antigen-1 (EBNA-1) in serum of 223 women with breast cancer (BC) and 309 controls in Guangzhou, China. VCA IgA levels were significantly associated with an elevated risk of BC, with adjusted ORs (95%CIs) of 1.70 (1.05-2.76) (seropositivity) and 2.21 (1.11-4.40) (unit increases in OD value). This association was stronger among young, lean, and HER2+ women. The EBNA-1 IgA levels in OD value, but not seropositivity, were associated with an increased risk of BC among ER+, PR+, and HER2+ patients. None of the IgG variables was related to BC. These results suggest the EBV association with BC in an endemic area of nasopharyngeal carcinoma.

Development of two avidity-based assays to detect recent HIV type 1 seroconversion using a multisubtype gp41 recombinant protein

Current laboratory methods to detect recent HIV-1 infection for the estimation of incidence have various limitations, including varying performance in different subtypes or populations. Therefore, new methods are needed to detect recent infections with increased specificity. We developed a recombinant protein, rIDR-M, that covered divergent sequences from the immunodominant region (IDR) of gp41 from all major subtypes and recombinants of HIV-1 group M and expressed in Escherichia coli. The rIDR-M protein was highly reactive with HIV antibodies in sera from different subtypes and equivalently detected antibodies to divergent subtypes B and AE from Thailand, in contrast to individual gp41 peptides derived from respective subtypes, suggesting that it can be used for incidence assays. The protein was used in two different assay formats to measure antibody avidity: (1) a two-well avidity index assay (AI-EIA) and (2) a new one-well limiting antigen avidity assay (LAg-avidity EIA), both with a pH 3.0 buffer to dissociate low-avidity antibodies present during early infection. Limiting the amount of antigen allowed detection of recent HIV-1 infection, with or without dissociation buffer, but the detection was most efficient when the pH 3.0 dissociation buffer was included. When a well-characterized 41-member seroincidence panel (20 recent and 21 long-term) was used, both the two-well AI-EIA and one-well LAg-avidity EIA efficiently distinguished recent and long-term infections. The new avidity-based assays using rIDR-M antigen may improve the accuracy of detecting recent HIV-1 infection and allow a better estimation of incidence in diverse HIV-1 subtypes.

Evaluation of an immunofiltration assay that detects immunoglobulin M antibodies against the ZEBRA protein for the diagnosis of Epstein-Barr virus infectious mononucleosis in immunocompetent patients

The performance of an immunofiltration assay (IMFA) that detects immunoglobulin M (IgM) antibodies to the Epstein-Barr virus (EBV) ZEBRA (BamHI Z EBV replication activator) protein was evaluated for the diagnosis of EBV infectious mononucleosis (IM) in immunocompetent patients. The test panel consisted of 47 sera displaying an EBV-specific antibody profile compatible with an acute primary EBV infection from patients with clinical and biological features of EBV IM, 20 sera from healthy individuals either with a past EBV infection or who were EBV seronegative, 20 sera displaying an equivocal EBV antibody pattern (viral capsid antigen IgG positive [VCA IgG+], VCA IgM+, and EBV nuclear antigen-1 IgG+), and 15 sera obtained from patients with a mononucleosis-like syndrome owing to cytomegalovirus, human herpesvirus 6, or parvovirus B19. Overall, the sensitivity and the specificity of the assay were found to be 92.5%, and 97.3%, respectively. The sensitivity of the assay for the diagnosis of heterophile antibody-negative EBV IM was 86.2%. The IMFA is rapid, easy to perform, and, thus, suitable for point-of-care testing, and it may be used as a first-line test for the diagnosis of acute EBV IM in immunocompetent patients.

Levels of autoantibodies, unlike antibodies to all extrinsic antigen groups, fall following B cell depletion with Rituximab

Many autoantibodies have variable-region sequences indicating their production in an affinity-matured antibody response involving germinal centers (GC). Plasma cells from GC can be long-lived, do not express CD20 and thus should not be depleted by a therapeutic monoclonal Ab against human CD20 - Rituximab. Nevertheless, autoantibody titers often fall following Rituximab treatment. To test if this reflects exclusive production by short-lived plasma cells in extrafollicular Ab responses, we monitored, after Rituximab treatment, levels of natural Ab and Ab against extrinsic antigens that do not induce productive GC. Eleven patients with active vasculitis and anti-proteinase-3 (PR3) Ab were assessed before and during 5 months after Rituximab therapy. Blood B cells were undetectable within 2 wk, and all patients achieved clinical remission. Levels of natural Ab - isohemagglutinins and anti-phosphorylcholine Ab - and Ab levels against thymus-independent and thymus-dependent extrinsic antigens were little affected. By contrast, 5 months after Rituximab, IgG autoantibody against PR3 had fallen to a median of 22% of pretreatment values. While the kinetics of this fall do not suggest an intrinsically short lifespan of autoantibody-producing cells, the data are consistent with Rituximab causing loss of sites within inflammatory tissues that selectively sustain autoantibody-producing cells.

Native early antigen of Epstein-Barr virus, a promising antigen for diagnosis of nasopharyngeal carcinoma

The Epstein-Barr virus (EBV) early antigen (EA) complex consists of multiple proteins with relevance for diagnosis of acute, chronic and malignant EBV related diseases, including nasopharyngeal carcinoma (NPC). In a recent study, it was found that the molecular diversity of EBV-specific IgG and IgA antibody responses in NPC patients and demonstrated that these reflect independent B-cell triggering leading to distinct EBV antigen-recognition profiles. The fine-specificity of NPC-related IgG and IgA responses was explored further against defined recombinant and synthetic EBV-EA antigens using immunofluorescence, immunoblot and ELISA techniques and determined their diagnostic value in a large panel of sera from NPC (n = 154), non-NPC tumor patients (n = 133), acute mononucleosis patients (n = 70) and healthy EBV carriers (n = 259). Individual recombinant EBV-EA markers yielded sensitivity/specificity values not exceeding 86%, whereas selected EA-specific peptide epitopes were rather poorly recognized by IgG and IgA antibodies in NPC sera. Surprisingly, we found that a "low salt" native EA-protein extract reproducibly prepared from purified nuclei of EA-induced HH514 cells, and containing characteristic EA(D)-polypeptides, such as p47-54 (BMRF1), p138 (BALF2), p55-DNAse (BGLF5), and p65-TK (BXLF1), but without viral capsid (VCA) or nuclear antigen (EBNA) reactivity, gave highest sensitivity (90.4%) and specificity (95.5%) values for NPC diagnosis in both IgG and IgA ELISA. The data support further the notion that EBV-EA reactive IgG and IgA antibodies in NPC patients are directed against distinct conformational and-in part-linear epitopes on EBV-specific proteins, barely recognized in other EBV-related syndromes. The use of a defined native EBV EA-specific antigen opens the way to further improve serological diagnosis of NPC.

Prevalence of primary versus reactivated Epstein-Barr virus infection in patients with VCA IgG-, VCA IgM- and EBNA-1-antibodies and suspected infectious mononucleosis

BACKGROUND

In Epstein-Barr virus (EBV) infection, IgG- and IgM-antibodies to viral capsid antigen (VCA) and IgG-antibodies to Epstein-Barr nuclear antigen 1 (EBNA-1) can occur simultaneously both in late primary infection and during subclinical viral reactivation in immunocompetent persons, and the differential diagnosis is of importance.

OBJECTIVES

To study the prevalence of primary infection and serological reactivation in patients with suspected primary EBV infection and with all three parameters present.

STUDY DESIGN

Fifty serum samples from 43 consecutive patients referred for suspected infectious mononucleosis and positive for VCA IgG-, VCA IgM- and EBNA-1-antibodies by EIA, were tested for IgG-antibody avidity with an EBV IgG immunoblot. Sera were also tested for heterophile antibodies (HA). To verify the presence of IgM-antibodies an EBV IgM immunoblot was performed when high-avidity IgG-antibodies were found.

RESULTS AND CONCLUSIONS

Of 43 patients with suspected primary EBV infection and VCA IgG-, VCA IgM- and EBNA-1-antibodies present, only 18 patients (42%) had a late primary infection. Twenty-one patients (49%) had high-avidity IgG-antibodies, indicating an IgM response due to reactivation, thus suggesting other causes for their symptoms. In 10 of these 21 patients the presence of IgM-antibodies was confirmed by immunoblot, indicating reactivation as a cause of IgM-antibodies in at least 23% of the 43 patients studied. Of 18 patients with primary infection, HA were detected in 16 (94%) of 17 patients tested. Only one (5%) of the patients with high-avidity antibodies had HA. Absence of HA in patients with this serological pattern is therefore a good indicator of reactivation, and conversely, the presence of HA is a good indicator of primary infection. In HA negative patients, avidity testing could be used for differential diagnosis.

What delay should there be between primary infectious mononucleosis and renal transplantation?

A 17-yr-old girl in end-stage renal failure was due to undergo living-related pre-emptive renal transplantation when she developed acute infectious mononucleosis (AIM) from Epstein-Barr virus (EBV). In view of the risk of post-transplant lymphoproliferative disorder (PTLD) we were unsure as to the optimal delay between AIM and renal transplantation. This report describes the process used to determine maturation of the immune response to EBV using a combination of serology, immunophenotyping and molecular viral load estimation. These tests showed that EBV had not been cleared and dialysis was instituted rather than proceed directly to transplantation. After EBV viral load became undetectable in the blood, living-related donor was successfully performed 13 months after AIM. With 42-month post-transplant follow up there has been no evidence of PTLD.

Serum antibody response to Human papillomavirus (HPV) infections detected by a novel ELISA technique based on denatured recombinant HPV16 L1, L2, E4, E6 and E7 proteins

Background

Human papillomaviruses (HPVs) are the primary etiological agents of cervical cancer and are also involved in the development of other tumours (skin, head and neck). Serological survey of the HPV infections is important to better elucidate their natural history and to disclose antigen determinants useful for vaccine development. At present, the analysis of the HPV-specific antibodies has not diagnostic value for the viral infections, and new approaches are needed to correlate the antibody response to the disease outcome. The aim of this study is to develop a novel ELISA, based on five denatured recombinant HPV16 proteins, to be used for detection HPV-specific antibodies.

Methods

The HPV16 L1, L2, E4, E6 and E7 genes were cloned in a prokaryotic expression vector and expressed as histidine-tagged proteins. These proteins, in a denatured form, were used in ELISA as coating antigens. Human sera were collected from women with abnormal PAP smear enrolled during an ongoing multicenter HPV-PathogenISS study in Italy, assessing the HPV-related pathogenetic mechanisms of progression of cervical cancer precursor lesions. Negative human sera were collected from patients affected by other infectious agents. All the HPV-positive sera were also subjected to an avidity test to assess the binding strength in the antigen-antibody complexes.

Results

Most of the sera showed a positive reactivity to the denatured HPV16 proteins: 82% of the sera from HPV16 infected women and 89% of the sera from women infected by other HPV genotypes recognised at least one of the HPV16 proteins. The percentages of samples showing reactivity to L1, L2 and E7 were similar, but only a few serum samples reacted to E6 and E4. Most sera bound the antigens with medium and high avidity index, suggesting specific antigen-antibody reactions.

Conclusion

This novel ELISA, based on multiple denatured HPV16 antigens, is able to detect antibodies in women infected by HPV16 and it is not genotype-specific, as it detects antibodies also in women infected by other genital HPVs. The assay is easy to perform and has low cost, making it suitable for monitoring the natural history of HPV infections as well as for detecting pre-existing HPV antibodies in women who receive VLP-based HPV vaccination.

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.

Detection of EBV-DNA in serum samples of an immunosuppressed child during a three years follow-up: association of clinical and PCR data with active infection

Twenty-four whole blood and serum samples were drawn from an eight year-old heart transplant child during a 36 months follow-up. EBV serology was positive for VCA-IgM and IgG, and negative for EBNA-IgG at the age of five years old when the child presented with signs and symptoms suggestive of acute infectious mononucleosis. After 14 months, serological parameters were: positive VCA-IgG, EBNA-IgG and negative VCA-IgM. This serological pattern has been maintained since then even during episodes suggestive of EBV reactivation. PCR amplified a specific DNA fragment from the EBV gp220 (detection limit of 100 viral copies). All twenty-four whole blood samples yielded positive results by PCR, while 12 out of 24 serum samples were positive. We aimed at analyzing whether detection of EBV-DNA in serum samples by PCR was associated with overt disease as stated by the need of antiviral treatment and hospitalization. Statistical analysis showed agreement between the two parameters evidenced by the Kappa test (value 0.750; p < 0.001). We concluded that detection of EBV-DNA in serum samples of immunosuppressed patients might be used as a laboratory marker of active EBV disease when a Real-Time PCR or another quantitative method is not available.

Serum Epstein-Barr virus DNA load in primary Epstein-Barr virus infection

Specific viral laboratory diagnosis of primary Epstein-Barr Virus (EBV) infection is usually based on antibody-detection assays. During acute, lytic phase of infection, viral DNA can also be detected in serum. In the present study, the diagnostic utility of EBV DNA detection and quantitation in serum in primary EBV infection was investigated. The level of EBV DNA in the serum of 98 immunocompetent patients aged 1-47 years with symptomatic, antibody-confirmed EBV primary infection was assessed using a quantitative real-time PCR assay. The association between viral load and time after onset of disease, age and clinical and laboratory data was investigated. Quantitative PCR detected EBV DNA in 93 of 98 samples (94.9%), and the measured viral loads ranged from 3.8 x 10(1) to 6.6 x 10(4) copies/ml. EBV DNA detection exhibited a sensitivity of 94.9% and a specificity of 97.4% for primary EBV infection. EBV DNA was always detectable until day 12 after onset of symptoms, whereas no further positive PCR results were found after a period of 22 days after onset of disease. Detection of EBV DNA also showed a clearer association with the clinical manifestation of disease than the presence of EBV specific VCA IgG antibodies of low avidity. EBV DNA load was found to correlate inversely with the time after onset of disease (P < 0.001), and higher viral load levels were detected in younger (P = 0.009) and in hospitalized patients (P = 0.038). The results indicate that real-time PCR is a reliable tool for diagnosis of primary EBV infection early in the course of disease. In addition, EBV DNA detection may serve as a useful diagnostic supplement in serologically indeterminate EBV infections.

Seroepidemiology of group C rotavirus infection in England and Wales

A total of 3199 serum samples collected in 1993--1994 from two population cohorts from England and Wales were tested for the prevalence of IgG antibodies specifically directed against group C rotavirus VP6. Seroprevalence was 39% (95% confidence intervals: 37.0-40.4%). Seroprevalence was highest (46.0%) in the oldest age group (61-70 years of age). Infection with group C rotaviruses occurred at an earlier age and with higher incidence in rural than in urban populations. These results may suggest transmission from animals to humans, however further work is required to identify the reservoir of group C rotavirus for human infection.

Development and use of a type-specific antibody avidity test based on herpes simplex virus type 2 glycoprotein G

OBJECTIVES

It is difficult to discriminate between lesions resulting from recently acquired versus established genital herpes simplex virus type 2 (HSV-2) infection. Methods not based on history or serum IgM status are needed.

GOAL

Our goal was to use type-specific gG-2 antibody avidity determinations based on HerpeSelect HSV-2 enzyme-linked immunosorbent assay (ELISA) to identify new infections.

STUDY

Sera (N = 168) from 71 patients with first-episode genital herpes and 45 sera from 21 patients with recurrent episodes were tested.

RESULTS

Median avidity increased from 30.2 in sera drawn </=6 weeks to 54.9 >6 weeks after infection (P <0.001). Patients with recurrent episodes and established HSV-2 infections (median, 6.1 years' duration) had higher avidity antibodies (median, 92.7; range, 55.1-100) than patients after first episodes (median, 33.7; range, 6.4-73.9; P <0.001).

CONCLUSION

Avidity testing based on HerpeSelect ELISA could be a cost-effective method to identify patients with new HSV-2 infections.

A new method for determination of varicella-zoster virus immunoglobulin G avidity in serum and cerebrospinal fluid

Background

Avidity determination of antigen-specific immunoglobulin G (IgG) antibodies is an established serological method to differentiate acute from past infections. In order to compare the avidity of varicella-zoster virus (VZV) IgG in pairs of serum and cerebrospinal fluid (CSF) samples, we developed a new technique of avidity testing, the results of which are not influenced by the concentration of specific IgG.

Methods

The modifications introduced for the new VZV IgG avidity method included the use of urea hydrogen peroxide as denaturing reagent, the adaptation of the assay parameters in order to increase the sensitivity for the detection of low-level VZV IgG in CSF, and the use of a new calculation method for avidity results. The calculation method is based on the observation that the relationship between the absorbance values of the enzyme immunoassays with and without denaturing washing step is linear. From this relationship, a virtual absorbance ratio can be calculated. To evaluate the new method, a panel of serum samples from patients with acute and past VZV infection was tested as well as pairs of serum and CSF.

Results

For the serum panel, avidity determination with the modified assay gave results comparable to standard avidity methods. Based on the coefficient of variation, the new calculation method was superior to established methods of avidity calculation.

Conclusions

The new avidity method permits a meaningful comparison of VZV IgG avidity in serum and CSF and should be of general applicability for easy determination of avidity results, which are not affected by the concentration of specific IgG.

Use of an immunoglobulin G avidity test to discriminate between primary and secondary dengue virus infections

An enzyme-linked immunosorbent assay-based immunoglobulin G (IgG) antibody avidity test was evaluated by using sera from 57 patients with acute dengue infection. Overall, 55 of 57 patients were correctly classified (27 of 27 with primary dengue and 28 of 30 with secondary dengue). We conclude that the IgG avidity test can be useful for differentiating between acute, primary, and secondary dengue infections.

Noticeable differences in bacterial defence on tonsillar surfaces between bacteria-induced and virus-induced acute tonsillitis

OBJECTIVE

Oral and pharyngeal cavities harbor a commensal bacterial flora which is kept in check by several innate and acquired agents. In this study, we focused on the proportions in which some antibacterial moderators (lysozyme, lactoferrin, IgG and S-IgA) coat the tonsillar surface bacteria in healthy individuals, in patients with acute tonsillitis (AT) culture-positive for Streptococcus pyogenes, and in patients with infectious mononucleosis (IM) caused by Epstein-Barr virus (EBV).

METHODS

Bacterial samples were collected for aerobic culturing and immunocytochemical evaluation from the tonsillar surfaces of eight healthy individuals (four males, four females; age range 16-22 years), eight patients with current AT (two males, six females; age range 16-29 years) and seven patients with IM (four males, three females; age range 15-21 years). The immunocytochemical assay was based on gold-labeled antiserum to human lysozyme, lactoferrin, IgG and S-IgA followed by gold particle tracing in the transmission electron microscope.

RESULTS

During AT, a significant increase in lysozyme coating (P<0.05) and lactoferrin coating (P<0.0005) of the bacteria was noted, whereas the S-IgA coating was significantly reduced (P<0.0005). During IM infection, a significant increase in lactoferrin coating was noted (P<0.0005) whereas immunoglobulin coating was significantly reduced (IgG P<0.025; S-IgA P<0.0005) compared with healthy controls. During IM, all antibacterial moderators evaluated were significantly reduced compared with the situation during AT.

CONCLUSIONS

Noticeable changes in the local innate and acquired bacterial defence system were observed during tonsillar infections, particularly during IM.

Measurement of EBV-IgG anti-VCA avidity aids the early and reliable diagnosis of primary EBV infection

Current serological methods for the diagnosis of Epstein-Barr virus (EBV) infection still differentiate poorly between primary infection and reactivation. This is particularly true when IgG and IgM antibodies are present simultaneously and only a single serum sample is provided for analysis. The demonstration of the IgG avidity state has the potential to distinguish recent from past or reactivated infection. An analysis of the kinetics of avidity maturation of anti-VCA antibodies in primary EBV infection was undertaken with longitudinally collected sets of sera from 28 well-characterised EBV cases and in sera from 35 cases with previous EBV infection and recent primary infection due to HIV, CMV, or hepatitis A. Antibodies directed against the viral capsid antigen (VCA) and Epstein-Barr nuclear antigen (EBNA-1) were sought, using a commercial enzyme immunoassay (EIA). In parallel with standard IgG anti-VCA detection, serum was incubated with 8 M urea to disrupt low-avidity complexes to allow calculation of the percentage avidity. In cases with primary EBV infection, the mean avidity rose from 54% at 6 weeks to 82% by 28 weeks after the onset of symptoms, but remained lower than that of the control sera (96%). The addition of the avidity measurement improved the sensitivity of IgG and IgM anti-VCA testing in diagnosis of primary EBV infection from 93% to 100%. The specificity of IgM anti-VCA testing alone was poor, with 14 of 35 cases (49%) demonstrating false-positive results, but it improved to 97% by the demonstration of high-avidity IgG anti-VCA. The combination of negative IgG anti-EBNA and low-avidity IgG anti-VCA had a sensitivity and specificity of 100%. The routine addition of IgG anti-VCA avidity estimation to diagnostic EBV serology is recommended.

Immunoglobulin G antibody avidity assay for serodiagnosis of hepatitis C virus infection

It has been reported that the avidity of specific IgG antibody is lower in primary viral infection than in chronic viral infection. However, few studies have been reported on the IgG avidity in hepatitis C virus (HCV) infection. In the present study, 36 patients with antibody to HCV (anti-HCV) were examined for IgG avidity by an enzyme immunoassay with or without urea elution. The avidity index was significantly low in patients with primary HCV infection (7.7 +/- 6.8%, mean +/- SD), compared with patients with chronic HCV infection (77.0 +/- 21.8%) and individuals with past HCV infection (44.5 +/- 12.6%). Temporal changes of IgG avidity were examined in six patients with primary HCV infection. The avidity index was low in the acute phase of the infection and then increased with time. These results suggest that the avidity assay for IgG anti-HCV is a useful method for distinguishing primary HCV infection from chronic or past HCV infection.

Causes for massive bacterial colonization on mucosal membranes during infectious mononucleosis: implications for acute otitis media

OBJECTIVE

A common complication of virus-induced upper respiratory tract infections is acute otitis media caused by bacterial pathogens. Simultaneously, increased bacterial colonization in the nasopharynx occurs. Our intention in this study was to identify the causes of this increased colonization of bacteria by evaluating their coating with the antibacterial substances lysozyme, lactoferrin and immunoglobulins IgG, S-IgA and IgM and their ability to penetrate epithelial cells during infectious mononucleosis (IM) caused by Epstein-Barr virus.

METHODS

Cellular samples were collected from the oropharynx of 21 patients (16 males, five females; age range 10-21 years) with current IM. An immunocytochemical assay using gold-labelled antiserum to human lysozyme, lactoferrin, IgG, S-IgA and IgM followed by gold particle and epithelial cell tracing in the transmission electron microscope.

RESULTS

A significant reduction in bacterial coating with IgG (P<0.05) and S-IgA (P<0.01) was noted, whereas there was a significant increase in coating with lactoferrin (P<0.01) and IgM (P<0.01). No significant change in lysozyme coating of the bacteria was noted, compared with healthy controls. Bacterial penetration into epithelial cells was seen particularly in patients culture-positive for beta-haemolytic streptococci.

CONCLUSIONS

Reduced bacterial coating with IgG and S-IgA immunoglobulins, combined with bacterial penetration into epithelial cells, may exacerbate the bacterial colonization on oropharyngeal mucosal membranes observed during IM.

Epstein-Barr virus (EBV) DNA in sera of patients with primary EBV infection

Detection of Epstein-Barr Virus (EBV) DNA by PCR in serum had a sensitivity of 80%, a specificity of 94%, and positive and negative predictive values of 95 and 79%, respectively, for the diagnosis of primary EBV infection. We suggest that this is a useful addition to the panel of tests used for this purpose.

Epstein-Barr virus (EBV) DNA in sera of patients with primary EBV infection

Detection of Epstein-Barr Virus (EBV) DNA by PCR in serum had a sensitivity of 80%, a specificity of 94%, and positive and negative predictive values of 95 and 79%, respectively, for the diagnosis of primary EBV infection. We suggest that this is a useful addition to the panel of tests used for this purpose.

Coupled particle light scattering: a new technique for serodiagnosis of Epstein-Barr virus infection

The Coupled Particle Light Scattering technique was evaluated for serological diagnosis of Epstein-Barr Virus (EBV) infection. Two hundred ninety-six patient sera selected from several clinical categories (acute infection, non-primary infection, interfering non-EBV infection, non-infected) were tested for IgM and IgG antibodies (anti-VCA, anti-EBNA and anti-EA). Determination of EBV IgG with Copalis multiplex was accurate when compared with Enzygnost Anti-EBV/IgG ELISA. Although the sensitivity of Copalis IgM for acute infections was 100% a positive IgM result did not always indicate an acute infection. Strong reactivity to IgG EA (ratio 3, 1) and IgG VCA (ratio 13, 3) correlated with persistent infection or reactivation. The CopalisI has many advantages over the existing methods, such as the possibility to measure three semi-quantitative IgG responses to three different EBV antigens simultaneously.

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.

The use of semi-automated EBV IgG avidity determination for the diagnosis of infectious mononucleosis

The diagnosis of acute Epstein-Barr virus (EBV) infection is based frequently on the combination of positive viral capsid antigen (VCA) IgM antibodies and negative EB viral nuclear antigen 1 (EBNA-1) IgG antibodies. However, both VCA IgM and EBNA-1 IgG can provide false positive and false negative results. Therefore, situations in which the EBV serology remains unclear are not uncommon. Determination of EBV IgG avidity can clarify the EBV status in these patients. So far, mainly immunofluorescence assays have been used for this purpose. These tests are laborious, their evaluation is subjective, and automation is difficult. Therefore, two commercially available microtiter plate enzyme immunoassays (EIA) were compared for their usefulness for semi-automated EBV IgG avidity determination. One assay is based on a mixture of EBV antigens, the other assay uses a synthetic peptide of the VCA-complex. Patient sera of confirmed acute and past EBV infections were tested for avidity by both assays. The results with the antigen mixture assay proved to be highly sensitive (100%) and specific (100%). Avidity index calculations on the basis of one-point-quantification titers gave better results than calculations using OD values. Determination of EBV IgG avidity by the peptide assay was complicated by the fact that it was less sensitive than the antigen mixture assay for IgG detection in acute EBV infections. On the other hand, about 30% of the samples had to be retested with the peptide assay in a higher dilution because the IgG units in initial testing fell outside the range covered by the standard curve. Using OD values of the peptide EIA, the sensitivity was 99% but the specificity of detection of acute EBV infections was only 86%. Thus, while the peptide EBV avidity assay is unsuitable as a confirmatory assay, avidity testing with the antigen mixture assay is a useful tool to resolve equivocal EBV serologies. Avidity assays on the basis of EIA can be automated which should lead to wider use of this methodology.

A simple, rapid enzyme-linked immunosorbent assay for evaluating immunoglobin G antibody avidity in toxoplasmosis

This article describes an enzyme-linked immunosorbent assay (ELISA) for evaluating the avidity of Toxoplasma-specific immunoglobin (Ig) G. The test was standardized with the Falcon assay screening test (F.A.S.T) ELISA system using 6 M urea in phosphate-buffered saline for dissociating low-avidity antibodies after the antigen-antibody interaction. The avidity indices for 25 serum samples from patients with a recent Toxoplasma infection ranged from 10 to 40% (mean index = 25.3%), whereas for sera from 25 subjects with preexisting Toxoplasma immunity, the indices ranged from 58 to 94% (mean index = 73.1%). In sequential serum samples obtained over a period of up to 15 months from three patients exhibiting a persistent IgM antibody response to T. gondii, the avidity indices gradually increased during the course of infection. Avidity indices compatible with a recent infection were found in serum samples taken during the first 3 months after the onset of toxoplasmic lymphadenopathy, whereas indices compatible with the presence of a long-term infection were found in serum samples taken 7 or more months after the onset of toxoplasmic lymphadenopathy. The simplicity and short assay time (less than 1 h) make the test a potentially useful tool in assessing the avidity of Toxoplasma-specific IgG.

An investigation of the high-avidity antibody response to glycoprotein 120 of human immunodeficiency virus type 1

The avidity of antibodies for antigens can be measured by determining what remains bound after exposing the antibody-antigen complex to a chaotropic agent such as urea. This method has been gaining popularity for assessing the immune response to the human immunodeficiency virus type 1 (HIV-1) surface glycoprotein gp120 (or its counterpart from simian immunodeficiency virus), during natural infection or after subunit vaccination. High-avidity antibodies have been considered to be a possible correlate of protection. We have examined the avidity assay to determine what it, in fact, measures. First, we studied the development of the anti-gp120 response in seroconverting individuals. Urea elution reduced the polyclonal anti-gp120 titers by 3- to 10-fold. After allowing for the consequent reduction in assay sensitivity, there was no obvious change in the rate of development of the high-avidity and unfractionated antibody responses. Furthermore, in the one individual who developed a strong autologous, virus-neutralizing response, the appearance of neutralizing antibodies and high-avidity antibodies did not coincide. Antibodies to the V3 loop, when present, comprised a major fraction of the polyclonal response that survives urea elution. We next examined the effect of urea elution on the binding to gp120 of a panel of monoclonal antibodies (MAbs). Urea treatment preferentially eluted MAbs to discontinuous rather than continuous epitopes, independent of their affinities. Furthermore, these patterns of epitope stability were unaltered by the presence of polyclonal anti-gp120 antibodies. As most broadly neutralizing anti-gp120 antibodies recognize discontinuous epitopes, this skewing effect must be taken into account when interpreting studies using polyclonal sera.

Evolution of envelope-specific antibody responses in monkeys experimentally infected or immunized with simian immunodeficiency virus and its association with the development of protective immunity

Previous studies of attenuated simian immunodeficiency virus (SIV) vaccines in rhesus macaques have demonstrated the development of broad protection against experimental challenge, indicating the potential for the production of highly effective immune responses to SIV antigens. However, the development of this protective immune status was found to be critically dependent on the length of time postvaccination with the attenuated virus strain, suggesting a necessary maturation of immune responses. In this study, the evolution of SIV envelope-specific antibodies in monkeys experimentally infected with various attenuated strains of SIV was characterized by using a comprehensive panel of serological assays to assess the progression of antibodies in longitudinal serum samples that indicate the development of protective immunity. In parallel studies, we also used the same panel of antibody assays to characterize the properties of SIV envelope-specific antibodies elicited by inactivated whole-virus and envelope subunit vaccines previously reported to be ineffective in producing protective immunity. The results of these studies demonstrate that the evolution of protective immunity in monkeys inoculated with attenuated strains of SIV is associated with a complex and lengthy maturation of antibody responses over the first 6 to 8 months postinoculation, as reflected in progressive changes in antibody conformational dependence and avidity properties. The establishment of long-term protective immunity at this time in general parallels the absence of further detectable changes in antibody responses and a maintenance of relatively constant antibody titer, avidity, conformational dependence, and the presence of neutralizing antibody for at least 2 years postinoculation. In contrast to the mature antibody responses elicited by the attenuated SIV vaccines, the whole-virus and envelope subunit vaccines in general elicited only immature antibody responses characterized by poor reactivity with native envelope proteins, low avidity, low conformational dependence, and the absence of neutralization activity against the challenge strain. Thus, these studies establish for the first time an association between the effectiveness of experimental vaccines and the capacity of the vaccine to produce a mature antibody response to SIV envelope proteins and further indicate that a combination of several antibody parameters (including titer, avidity, conformational dependence, and virus neutralization) are superior to any single antibody parameter as prognostic indicators to evaluate candidate AIDS vaccines.

Differentiation of primary from nonprimary genital herpes infections by a herpes simplex virus-specific immunoglobulin G avidity assay

An immunoglobulin G (IgG) antibody avidity assay which uses protein-denaturing agents and a modification of an enzyme-linked immunosorbent assay have been investigated for their usefulness in distinguishing primary genital herpes simplex virus (HSV) infections from nonprimary infections. Forty-nine serum specimens from patients with primary, recurrent, and nonprimary first-episode genital herpes were studied. The clearest separation was obtained with 6 M urea treatment, giving mean avidity indices of 0.398 for sera < or = 100 days after the infection and 0.879 for sera > 100 days after the infection (P < 0.001). No significant difference in avidity indices was observed between the recurrent and nonprimary first-episode infections. Determination of the avidity of HSV-specific IgG will improve the diagnostic potential of HSV serology.

Difficulties with the serologic diagnosis of infectious mononucleosis: a review of the RCPA quality assurance programs

The Royal College of Pathologists of Australasia's Quality Assurance Programs (QAP) on serologic assays for infectious Mononucleosis (IM) have identified a number of important problems in laboratory diagnosis of this condition. A wide range of assays for the diagnosis of acute Epstein-Barr virus (EBV) infection are available, although heterophile antibody tests are still the most frequently performed procedures for the diagnosis of IM. In 1993, eighty-six (54%) of the 159 participating laboratories performed only a heterophile test; of these, 71% did not provide an interpretation of their results and none mentioned the need for confirmatory EBV-specific antibody testing. This revealed a lack of appreciation that heterophile tests should only be used for screening, due to their inferior sensitivity of less than 50% in children and 80-90% in adults and specificity of 95% compared to EBV-specific assays. For these reasons the use of heterophile tests is discouraged. Although EBV-specific serology has traditionally been done by immunofluorescence (IF), the use of reliable ELISA methods using purified EBV-antigens is increasing. False negative EBV VCA IgM ELISA test results were obtained by laboratories using unpurified or unspecified VCA antigens. As only five laboratories used these tests in the 1992 QAP, the tests' true performances could not be properly assessed, suggesting the need for independent studies. Variable results were obtained by laboratories using commercial EBNA IgG assays (in addition to EBV IgM) suggesting that an assessment of these kits would also be worthwhile. The QAP reaffirm that reliable EBV IgM detection is the most useful test for the diagnosis of IM, even where other EBV markers are also used. In the 1992 and 1993 QAP, laboratory performance of both heterophile and EBV-specific tests was better with non-reactive serum specimens (99% (correct) than with reactive serum specimens (90% correct).