Viral antibodies in infectious mononucleosis

Follow-up after infectious mononucleosis in search of serological similarities with presymptomatic multiple sclerosis

BACKGROUND

A two- to three-fold increase in the risk of multiple sclerosis (MS) after infectious mononucleosis (IM) has been observed in cohort and case control studies. However, this association has not been investigated prospectively from IM. It remains to be determined whether long-term immunospecific sequelae with features consistent with presymptomatic MS occur after IM.

METHODS

Sera were obtained from individuals with acute IM from 2003-2007 (n = 42) and from the same individuals at a follow-up (FU) study approximately 10 years after IM. These were assayed for antibodies against a variety of Epstein-Barr virus (EBV) antigens, including gp350, a novel recombinant glycoprotein from the EBV envelope. Similarly, single-protein antigens were used to assess measles and varicella-zoster reactivity (Ncore and varicella-zoster glycoprotein E [VZVgE]). The FU study also included cerebrospinal fluid (CSF) samples from 21 of these individuals to test for IgG antibodies against the same viral antigens. As controls, CSF and serum samples were obtained from 15 EBV-seropositive volunteers who denied a history of IM, and serum samples were obtained from 24 EBV-seropositive blood donors. Anti-gp350, anti-Ncore and anti-VZVgE IgG levels were also analysed in sera and CSF samples from 22 persons with MS.

RESULTS

The FU assays showed higher anti-gp350 IgG (p = 0.007, univariate) than among healthy controls, with no difference in serum anti-VCA or anti-EBNA1 IgG levels and no difference in anti-gp350 in the CSF samples. Anti-Ncore IgG and anti-VZVgE were higher in acute IM samples (p < 0.001 and p < 0.0001, respectively) than at FU, although anti-Ncore remained heightened in an age-adjusted analysis at FU (p = 0.014) compared to the control group. In the MS group, the serum anti-gp350 and anti-Ncore IgG levels were significantly higher than among the control group, but the anti-VZVgE levels were not. The CSF anti-gp350 and VZVgE levels were slightly higher among persons with MS than among the control group, whereas anti-Ncore IgG was markedly higher in persons with MS than in the control group.

CONCLUSION

In the present study IM showed certain similarities with MS. Increased anti-gp350 reactivity persisted more than a decade after IM, reminiscent of the established increased anti-EBV reactivity in presymptomatic MS. Acute IM was associated with increased anti-measles and anti-VZV immunoreactivity, similar to the MRZ reaction in MS, with some evidence suggesting that this measles reactivity persisted after a decade.

The vagaries of IgM: a case report of EBV infection with concomitantly false-positive IgM for CMV, VZV, and HSV

Background

Serum IgM (immunoglobulin M) testing is commonly used to diagnose acute viral infections. However, most clinicians are unaware of the vagaries of IgM testing, including antigenic cross-reactivity between multiple viruses and risk misdiagnosis.

Case presentation

We report a case of infectious mononucleosis with concomitantly positive IgM for EBV, CMV, VZV, and HSV.

A 26-year-old man presented with acute infectious mononucleosis picture. His blood work showed a total bilirubin level of 7.7 mg/dl, ALT 1077 U/L, AST 806 U/L, ALP 325 U/L, and INR 1.0. Monospot was positive; peripheral blood smear showed atypical lymphocytes; however, because EBV infectious mononucleosis does not typically cause elevation of liver enzymes over 1000, other etiologies were explored. Tests for hepatitis A, B, C, HIV, ANA, and ASMA returned negative. IgM for EBV-VCA, CMV, HSV, and VZV all returned positive, and the diagnosis of EBV IM was called into question. Subsequent tests of CMV and HSV PCR for viral load were negative (VZV was not clinically suspected), and later on, EBV-EBNA returned negative and EBV-VCA IgM and IgG returned positive, confirming the diagnosis of acute EBV infection.

Conclusion

We believe that IgM seropositivity can result from cross-reactivity among several viruses (especially herpes viruses), and although often relied on, a positive IgM should not serve as the sole determinant for diagnosis of acute viral infections.

Clinical laboratory investigation of a patient with an extremely high D-dimer level: A case report

BACKGROUND

D-dimer, a soluble degradation product of cross-linked fibrin, is commonly used as an important marker for the diagnosis of disseminated intravascular coagulation and differential diagnosis of thrombosis. Herein, we present a geriatric case with an unusually elevated D-dimer level.

CASE SUMMARY

An 82-year-old woman, admitted to the ward with a diagnosis of chronic heart failure, was noted to have a remarkably elevated D-dimer level, beyond the qualified range (> 100 mg/L), utilizing the Innovating D-dimer for Sysmex CS-5100 System™. However, no evidence, including clinical symptoms, radiographic evidence of thromboembolic disease, and parallel fibrinogen degradation product values, suggested that this patient was at high risk of thrombopenia. To confirm the discrepancy, a series of approaches including sample dilution, re-analysis via alternative methods, and sample treatment with blockage of specific heterophilic antibodies were performed. A remarkable disappearance of the elevated D-dimer values was observed in the samples after they were subjected to these approaches (4.49, 9.42, 9.06, and 12.58 mg/L, respectively). This confirmed the presence of heterophilic antibodies in this case. In addition, a reduction in cardiac output due to the presence of cardiac failure could also be responsible for the existence of a hypercoagulable state in this case.

CONCLUSION

In conclusion, the presence of heterophilic antibodies should be considered when an elevated D-dimer value is not in conformity with the clinical evidence, and a viral infection should be considered when interference by a heterophilic antibody exists.

EBV VCA IgM and cytomegalovirus IgM dual positivity is a false positive finding related to age and hepatic involvement of primary Epstein-Barr virus infection in children

Primary Epstein-Barr virus (EBV) infection is common in childhood, and dual positivity of serum EBV IgM and cytomegalovirus (CMV) IgM antibodies occur in some cases. This study aimed to evaluate the cause of EBV and CMV IgM dual positivity to determine whether it represents a false-positive finding or a true coinfection.A total of 494 children diagnosed with primary EBV infection, manifesting as infectious mononucleosis, were recruited. The diagnosis was based on positive EBV viral capsid antigen (VCA) IgM antibodies, and serum CMV IgM antibodies and liver enzymes were also evaluated in 149 subjects.Of 149 children with primary EBV infection, 40 (26.8%) had serum EBV VCA IgM and CMV IgM dual positivity. However, true CMV infection was confirmed only in 1 child of 40 (2.5%) who was positive for both serum CMV Ag and urine CMV polymerase chain reaction (PCR) and negative for serum CMV IgG antibody. Among the children with primary EBV infection, the rate of dual positivity was higher in infants and lower in adolescents (P = .013). Liver enzymes were more significantly elevated in children with dual positivity than in those with negative results for CMV IgM antibodies (P = .026), which correlated with the serum EBV and CMV IgM titers.Serum EBV and CMV IgM dual positivity are more prevalent in children with primary EBV infection than what was previously reported. Our results indicate that serum EBV and CMV IgM dual positivity represents a false-positive finding, as opposed to an actual CMV coinfection, possibly due to antigenic cross-reactivity.

Prevalence and causes of abnormal PSA recovery

BACKGROUND

Prostate-specific antigen (PSA) test is of paramount importance as a diagnostic tool for the detection and monitoring of patients with prostate cancer. In the presence of interfering factors such as heterophilic antibodies or anti-PSA antibodies the PSA test can yield significantly falsified results. The prevalence of these factors is unknown.

METHODS

We determined the recovery of PSA concentrations diluting patient samples with a standard serum of known PSA concentration. Based on the frequency distribution of recoveries in a pre-study on 268 samples, samples with recoveries <80% or >120% were defined as suspect, re-tested and further characterized to identify the cause of interference.

RESULTS

A total of 1158 consecutive serum samples were analyzed. Four samples (0.3%) showed reproducibly disturbed recoveries of 10%, 68%, 166% and 4441%. In three samples heterophilic antibodies were identified as the probable cause, in the fourth anti-PSA-autoantibodies. The very low recovery caused by the latter interference was confirmed in serum, as well as heparin- and EDTA plasma of blood samples obtained 6 months later. Analysis by eight different immunoassays showed recoveries ranging between <10% and 80%. In a follow-up study of 212 random plasma samples we found seven samples with autoantibodies against PSA which however did not show any disturbed PSA recovery.

CONCLUSIONS

About 0.3% of PSA determinations by the electrochemiluminescence assay (ECLIA) of Roche diagnostics are disturbed by heterophilic or anti-PSA autoantibodies. Although they are rare, these interferences can cause relevant misinterpretations of a PSA test result.

Interference from heterophilic antibodies in D-dimer assessment. A case report

We describe the case of a 3-year-old girl, admitted to the pediatric ward for three repeated episodes of severe migraine associated with vertigo, with onset 1 week after complete remission from an episode of chicken pox (i.e., varicella-zoster virus infection). All radiological and laboratory examinations were normal, except for a markedly elevated value of D-dimer (i.e. 8998 ng/ml; local reference range: < 243 ng/ml), measured with a commercial latex-enhanced immunoturbidimetric assay. After physical and Doppler ultrasound examination, possible presence of thrombosis was ruled out, and the patient was discharged. In the following year, however, her plasma D-dimer values always remained frankly elevated, so that an analytical interference was suspected. A plasma sample was treated with a specific heterophilic antibodies blocking reagent and then assayed along with the untreated sample, with these showing a marked discrepancy of D-dimer values, that is 232 versus 2877 ng/ml. These results, highly indicative for the presence of heterophilic antibodies, are discussed in the light of the serious challenges that this type of analytical interference may pose on quality and reliability of D-dimer testing.

Application of a commercial immunoblot to define EBV IgG seroprofiles

BACKGROUND

Immunoblot (IB) techniques using different Epstein-Barr virus (EBV) antigens have been applied for detecting specific antibodies, making possible to obtain EBV seroprofiles in a single determination. The aim of this study was to evaluate a commercial IB for the detection of EBV-specific IgG (Euroimmun, Lübeck, Germany).

METHODS

A total of 117 samples classified as EBV primary recent infections (n = 70), past infections (n = 29), or not infected (n = 18) have been used. The samples were characterized by immunofluorescence, by testing EBV capsid antigens IgM and IgG (using indirect approaches) and EBV nuclear antigen (by anticomplement technique; Meridian Bioscience Inc.).

RESULTS

Using the cut-off value as defined by the IB manufacturer, the concordance, relative sensitivity, and relative specificity were 85.5 (100/117), 94.3% (66/70), and 72.3% (34/47), respectively. If a corrected cut-off value was considered to classify the samples, the corresponding corrected figures were 89.7, 88.6, and 91.5%, respectively.

CONCLUSION

Being a useful serological diagnostic tool, IB for testing EBV IgG seems to be an adequate approach to define EBV seroprofiles. However, efforts to better define the cut-off value should be made in order to improve the performance of the assay in evaluation.

Interference from heterophilic antibodies in troponin testing. Case report and systematic review of the literature

Heterophilic antibodies, comprising both "true" heterophilic antibodies and human anti-mouse antibodies (HAMA), represent an important source of interference in laboratory medicine, thus including cardiospecific troponin(s) testing. We describe the case of a 76-years-old woman with implausible and persistent elevation of cardiospecific troponin I, which was finally attributed to interference from heterophilic antibodies. According to literature data, the frequency of this interference ranges between 0.1 and 3.1%, is almost unpredictable and unsuspected, may involve both cardiospecific troponins I and T, and may virtually affect any type of immunoassay, either one- or two-step. The presence of interfering antibodies should always be suspected when test results do not go hand in hand with the clinics, or with the results of additional radiological and laboratory investigations. Once other causes of interference have been ruled out, test repetition with an alternative assay and removal of interfering antibodies with heterophilic antibodies blocking reagent, normal mouse serum, immobilized protein A column or polyethylene glycol may be advisable. As a simple alternative, measurement of serial dilutions of suspected samples usually shows nonlinearity of test results in the presence of heterophilic antibodies.

Primary human immunodeficiency virus infection presenting as elevated aminotransferases

BACKGROUND/PURPOSE

Primary human immunodeficiency virus type 1 (HIV-1) infection is often under-diagnosed because of its nonspecific presentations. Elevated aminotransferase levels is one of its clinical manifestations, but is infrequently reported in the literature. The objective of this study was to investigate cases of elevated aminotransferases as a manifestation of primary HIV-1 infection.

METHODS

A retrospective chart review from October 1990 to May 2009 of HIV-1 infected patients in a registered database at a tertiary hospital was conducted to identify patients diagnosed with primary HIV-1 infection. An elevated aminotransferase level was broadly defined as above-normal values of alanine or aspartate aminotransferases. Acute hepatitis markers were determined using stored serum samples.

RESULTS

Twenty-three of the 827 (2.8%) patients were identified as having a primary HIV-1 infection. All were male, with a median age of 26 years (range, 19-77 years), and the majority were men who had sex with men (19/23, 82.6%). The most common clinical manifestations were fever (95.7%), elevated aminotransferases (65.2%), fatigue (47.8%), and pharyngitis (47.8%). The median CD4 lymphocyte count was 374/μL (range, 109-674/μL) and the median log HIV viral load was 5.0 (range, 4.3-5.9). For the 15 patients with abnormal liver function tests, the median aspartate aminotransferase level was 112 U/L (range, 62-969 U/L) and the median alanine aminotransferase level was 146 U/L (range, 42-1,110 U/L).

CONCLUSION

Elevated aminotransferases may be an initial manifestation of primary HIV infection and is more common than expected. Primary HIV-1 infection should be one of the differential diagnoses considered in young men presenting with unexplained, new-onset liver function impairment.

Evaluation of four commercial systems for the diagnosis of Epstein-Barr virus primary infections

To compare the performance of four diagnostic commercial systems for Epstein-Barr virus (EBV) serology (for IgM and IgG virus capsid antigen [VCA] and EBV nuclear antigen [EBNA] antibodies), a collection of 125 samples from clinically suspected infectious mononucleosis cases was studied. Indirect immunofluorescence (IIF) for VCA IgM and IgG antibodies and anticomplement immunofluorescence for EBNA antibodies (Meridian Bioscience Inc.) were used as reference methods. By these methods, the cases were classified EBV primary infection (presence of IgM to VCA or IgG to VCA in the absence of EBNA antibodies; n = 82), EBV past infection (presence of VCA IgG and EBNA antibodies in the absence of VCA IgM; n = 26), or no infection (negative for the three markers; n = 17). The following systems were tested: two chemiluminescent immunoassays (CLIAs; the Liason [CLIA-L; DiaSorin] and the Immulite 2000 [CLIA-I; Siemens]), immunofiltration (IF; All.Diag), and an enzyme-linked immunosorbent assay (ELISA; DiaSorin). In the IgM assays, sensitivities ranged from 67.1% (ELISA) to 92.2% (CLIA-L) and specificities ranged from 93.8% (CLIA-L) to 100% (IF). In the VCA IgG assays, sensitivities varied from 79.4% (IF) to 94.4% (CLIA-I) and specificities varied from 94.4% (IF and CLIA-L) to 100% (CLIA-I and ELISA). In EBNA assays, sensitivities ranged from 78.1% (IF) to 93.8% (CLIA-I) and specificities ranged from 32.3% (CLIA-L) to 91.4% (IF). In relation to EBV profiles, the corresponding figures for sensitivity (in detecting primary infection) for IF, CLIA-L, CLIA-I, and ELISA were 92.7%, 93.8%, 89%, and 89.6%, respectively, and those for specificity (to exclude primary recent infection) were 90.7%, 94.6%, 97.7%, and 95.2%, respectively. Although there were limitations in some individual markers, especially CLIA-L for EBNA IgG, the systems evaluated appear to be useful for diagnosis of EBV infection.

Absence of human bocavirus from deceased fetuses and their mothers

BACKGROUND

The human bocavirus (HBoV), a newly discovered parvovirus, is closely related to the bovine parvovirus and the canine minute virus, which are known to cause adverse pregnancy outcomes. Another human parvovirus, B19, can lead to fetal hydrops, miscarriage and intrauterine fetal death (IUFD).

OBJECTIVES

To determine the prevalence of HBoV DNA in aborted fetuses and IUFDs. The HBoV serology of the mothers was also studied.

STUDY DESIGN

We retrospectively studied all available fetuses (N=535) autopsied during 7/1992-12/1995, and 1/2003-12/2005 in Helsinki, Finland. All available formalin-fixed paraffin-embedded fetal tissues - placenta, heart and liver - of 120 miscarriages, 169 IUFDs, and 246 induced abortions were studied by quantitative PCR. We also measured the HBoV IgM and IgG antibodies in the corresponding maternal sera (N=462) mostly of the first trimester. The IgM-positive sera underwent HBoV PCR.

RESULTS

None of the fetal tissues harbored HBoV DNA. A total of 97% (448/462) of the mothers were positive for IgG antibodies to HBoV, while only 0.9% (4/462) exhibited HBoV-specific IgM antibodies without viremia or respiratory symptoms. One IgM-positive mother had an unexplained fetal loss.

CONCLUSIONS

We did not find HBoV DNA in any of the deceased fetuses. Almost all pregnant women were HBoV-IgG positive.

Emergence of anti-red blood cell antibodies triggers red cell phagocytosis by activated macrophages in a rabbit model of Epstein-Barr virus-associated hemophagocytic syndrome

Hemophagocytic syndrome (HPS) is a fatal complication frequently associated with viral infections. In childhood HPS, Epstein-Barr virus (EBV) is the major causative agent, and red blood cells (RBCs) are predominantly phagocytosed by macrophages. To investigate the mechanism of RBC phagocytosis triggered by EBV infection, we adopted a rabbit model of EBV-associated HPS previously established by using Herpesvirus papio (HVP). The kinetics of virus-host interaction was studied. Using flow cytometry, we detected the emergence of antibody-coated RBCs, as well as anti-platelet antibodies, at peak virus load period at weeks 3 to 4 after HVP injection, and the titers increased thereafter. The presence of anti-RBCs preceded RBC phagocytosis in tissues and predicted the full-blown development of HPS. The anti-RBC antibodies showed cross-reactivity with Paul-Bunnell heterophile antibodies. Preabsorption of the HVP-infected serum with control RBCs removed the majority of anti-RBC activities and remarkably reduced RBC phagocytosis. The RBC phagocytosis was specifically mediated via an Fc fragment of antibodies in the presence of macrophage activation. Therefore, the emergence of anti-RBC antibodies and the presence of macrophage activation are both essential in the development of HPS. Our observations in this animal model provide a potential mechanism for hemophagocytosis in EBV infection.

Cross-reactivity of Epstein-Barr virus-specific immunoglobulin M antibodies with cytomegalovirus antigens containing glycine homopolymers

Timely and reliable detection of acute primary human cytomegalovirus (HCMV) infection is important in prenatal screening programs and for differential diagnosis of infectious mononucleosis-like disease. Enzyme-linked immunosorbent assays (ELISAs) based on HCMV proteins enable the sensitive detection of immunoglobulin M (IgM) antibodies during primary infection. However, concerns have been raised about possible cross-reactivities of the HCMV antigens used for the design of such ELISAs with IgM antibodies induced by Epstein-Barr Virus (EBV). In this study we investigated whether IgM antibodies generated during acute EBV infection reacted with recombinant HCMV antigens. Serum samples from patients with primary EBV infection frequently scored positive when tested in different HCMV IgM ELISAs, irrespective of whether conventional or recombinant antigens were used for the design of the HCMV IgM assays. Such cross-reactive IgM antibodies were found to be directed against short glycine-rich motifs contained within the nonstructural HCMV proteins pUL44 and pUL57. Further analyses revealed that these glycine-rich motifs were major antigenic domains for IgM antibodies induced during HCMV infection. Their deletion from recombinant proteins abrogated reactivity with IgM synthesized during HCMV infection. EBV-induced IgM antibodies that reacted with HCMV antigens showed similar kinetics of reactivity in HCMV- or EBV-specific assays in the course of primary EBV infection, indicating that the two populations of antibodies were highly overlapping. The results demonstrate that primary EBV infection leads to the induction of IgM antibodies that specifically bind to widely used diagnostic antigens of HCMV. This has to be considered in the interpretation of HCMV-specific IgM assays.

Raised levels of antibodies to human viruses at the clinical onset of autoimmune chronic active hepatitis

Patients with autoimmune chronic active hepatitis (AICAH) often have very high titres of antibodies to rubella and/or measles virus. In the present study a young girl at the clinical onset of AICAH exhibited very high titres of antibodies against influenza viruses A and B, parainfluenza viruses, rubella virus and varicella-zoster virus. The titres normalized over 2 months except for rubella and varicella-zoster antibodies. Strong reactivities were seen against the rubella structural proteins E1, E2 and C in Western blot but IgM antibodies were not demonstrated. Total IgG was increased with normal ratios of subclasses. The IgG1 was the dominant antibody to E1 and E2, while IgG4 dominated the anti-C response. There was no significant shift in subclass reactivities over one year from onset. The polymerase chain reaction (PCR), using a nested primer set, was negative for rubella virus RNA in a liver biopsy obtained at the clinical onset and in peripheral blood mononuclear cells (PBMC) 1 year later. Co-cultivation experiments using PBMC and permissive cell lines were also negative for rubella virus. Hence, in the very early phase of AICAH there may be a transiently enhanced antibody response to various unrelated viruses.