Effect of primary Epstein-Barr virus infection on human herpesvirus 6, cytomegalovirus, and measles virus immunoglobulin G titers

Epstein-Barr Virus: Clinical Diagnostics

The vast majority of the human adult population is infected with Epstein-Barr virus (EBV), and the majority of the EBV-infected individuals tolerates the infection well, without any further symptoms after primary infection. In cases of individuals which undergo primary infection in the form of an infectious mononucleosis, or which have undergone primary infection in their past, it is sometimes important to appraise symptomatic disease or differentiate infectious mononucleosis from other conditions. In these cases, serological methods, i.e., immunofluorescence, ELISA, or Western blot, are the methods of choice to come to an unequivocal diagnostic conclusion, while the detection and quantification of viral DNA through PCR plays a minor role.On the other hand, in a minority of the human population, EBV infection is associated or causally linked with autoimmune or malignant disease. Especially in the bone marrow or solid organ transplanted, or in otherwise severely immune-suppressed patients, prolonged EBV primary infection or EBV reactivation from latency may be a serious and life-threatening complication which needs to be diagnosed the faster the better, in order to take therapeutic steps in time. Determining the serostatus correctly is also important in these cases. However, the direct and quantitative detection of viral DNA are of importance for the diagnosis of serious EBV disease and its monitoring.In the following, we give an overview of diagnostic methods to accurately determine EBV serostatus and viral load. We evaluate the advantages and disadvantages of each method and report on the diagnostic significance of each and how to resolve diagnostic problems in case of uncertainties. For practical procedures, we refer to the detailed instruction manuals of the respective test kit manufacturers which have to be closely followed for reliable results.

The etiology of Rubella IgM positivity in patients with rubella-like illness in Iran from 2011 to 2013

Rubella is a mild self-limiting contagious viral disease caused by the rubella virus (RV). Although symptoms are often mild, the concern is centralized around the possible effect on a fetus growth and development in case of primary infection during early months of pregnancy. Recently acquired rubella is commonly confirmed by RV-specific IgM antibody detection in the serum. However, rubella primary infection is not always the only cause of IgM positivity. Other possible causes of rubella IgM positivity may include IgM persistence following vaccination or naturally acquired infection or even re-infection. Moreover, nonspecific IgM reactivity can cause false-positive results. There are few articles to differentiate the aetiology of rash in rubella-like illnesses. However, limited studies have been conducted on clarifying the source of IgM positivity in these cases. This article reports the study of 10,896 clinical cases demonstrating rubella-like illness between 2011 and 2013 in Iran. The rate of IgM positivity among these cases was 0.52% (57 cases). As predicted based on the high coverage of vaccination in Iran fewer than 16% of cases with ELISA IgM positive result, were due to current rubella primary infections. The greater part of the positive IgM reactions occurred in cross reactivity with other viruses (31.6%) or in prolonged IgM response post vaccination (24.6%). This research confirmed that the positive result of rubella IgM assay in vaccinated individuals is mainly caused by prolonged IgM production, rubella re-infection, and false positivity due to infection with other viruses, rather than the rubella primary infection itself.

Identification of continuous human B-cell epitopes in the VP35, VP40, nucleoprotein and glycoprotein of Ebola virus

Ebola virus (EBOV) is a highly virulent human pathogen. Recovery of infected patients is associated with efficient EBOV-specific immunoglobulin G (IgG) responses, whereas fatal outcome is associated with defective humoral immunity. As B-cell epitopes on EBOV are poorly defined, we sought to identify specific epitopes in four EBOV proteins (Glycoprotein (GP), Nucleoprotein (NP), and matrix Viral Protein (VP)40 and VP35). For the first time, we tested EBOV IgG+ sera from asymptomatic individuals and symptomatic Gabonese survivors, collected during the early humoral response (seven days after the end of symptoms) and the late memory phase (7–12 years post-infection). We also tested sera from EBOV-seropositive patients who had never had clinical signs of hemorrhagic fever or who lived in non-epidemic areas (asymptomatic subjects). We found that serum from asymptomatic individuals was more strongly reactive to VP40 peptides than to GP, NP or VP35. Interestingly, anti-EBOV IgG from asymptomatic patients targeted three immunodominant regions of VP40 reported to play a crucial role in virus assembly and budding. In contrast, serum from most survivors of the three outbreaks, collected a few days after the end of symptoms, reacted mainly with GP peptides. However, in asymptomatic subjects the longest immunodominant domains were identified in GP, and analysis of the GP crystal structure revealed that these domains covered a larger surface area of the chalice bowl formed by three GP₁ subunits. The B-cell epitopes we identified in the EBOV VP35, VP40, NP and GP proteins may represent important tools for understanding the humoral response to this virus and for developing new antibody-based therapeutics or detection methods.

Herpesvirus infections and allergic sensitization in children of families with anthroposophic and non-anthroposophic lifestyle - the ALADDIN birth cohort

BACKGROUND

Growing up in families with an anthroposophic lifestyle has been associated with reduced risk of allergic disease in children. The aim of this report was to assess whether children with this lifestyle are infected earlier with Epstein-Barr virus (EBV), which has been associated with reduced risk of allergic disease, and three other herpesviruses potentially involved in allergy development, namely Human herpesvirus 6 (HHV6), Human herpesvirus 7 (HHV7) and cytomegalovirus (CMV).

METHODS

Within the ALADDIN (Assessment of Lifestyle and Allergic Disease During Infancy), birth cohort study 157 children were categorized according to lifestyle into anthroposophic and non-anthroposophic. IgG-levels for EBV, HHV6, HHV7 and CMV were determined in plasma samples collected at ages 12 and 24 months and from parents. IgE levels against seven common allergens were analyzed at 24 months.

RESULTS

No significant differences in seroprevalence of EBV, HHV7 or CMV were detected at any age between the two lifestyle groups. The seroprevalence of HHV6 was significantly lower in the anthroposophic group at 24 months of age (74.6% vs. 87.5%, p-value 0.048). Further, no significant associations between allergic sensitization and seropositivity to any of the viruses were detected; however, an interaction effect of lifestyle could not be ruled out.

CONCLUSIONS

Our results indicate that there is no strong influence of exposure to the anthroposophic lifestyle on the time for infection with EBV, HHV6, HHV7 or CMV. These infections can therefore not be assumed to be important factors in the allergy-protective effect of this lifestyle.

Human herpesvirus 6 and chronic fatigue syndrome

The cause of chronic fatigue syndrome (CFS) is still enigmatic. Using indirect immunofluorescence testing for measuring antibody against human herpesvirus 6 (HHV-6), this study investigated the association of CFS with infection by HHV-6. Seventeen patients (group A) fulfilling the Centers for Disease Control (CDC) definition for CFS were compared with eight patients (group B) with chronic fatigue but not meeting the CDC criteria. No significant difference was found between the two groups for 30 parameters including sex, age, exposure to children and serology for Epstein-Barr virus, cytomegalovirus, herpes simplex virus, and toxoplasma. Univariate analysis showed that patients in group A complained more frequently of a sore throat, headache and of recurrent type of fatigue. These three parameters are discriminant in identifying patients who will meet the CDC case definition of CFS. The titre of antibody against HHV-6 in group A (1:99) was significantly higher than in group B (1:15) (P=0.007). Elevated HHV-6 titres suggests that this virus could be a cofactor in the pathogenesis of CFS.

Lack of evidence for systemic cytomegalovirus reactivation in maintenance hemodialysis patients

The risk of cytomegalovirus (CMV) reactivation among hemodialysis (HD) patients is unknown. In 52 HD patients from a single center, CMV serology and quantitative PCR were performed. The detection limit of PCR was 20 copies/ml. Here, PCR ruled out CMV viremia, despite CMV-IgM seropositivity in 15.4% patients.

High-dose ganciclovir in HHV-6 encephalitis of an immunocompetent child

Encephalitis and other neurologic complications, including acute necrotizing encephalopathy, are associated with human herpesvirus-6 infection. Antiviral treatment against human herpesvirus-6 infection is indicated only for immunocompromised patients. We describe a 15-month-old immunocompetent child with severe human herpesvirus-6-induced encephalitis. The primary infection was characterized by human herpesvirus-6 DNA in cerebrospinal fluid and serum, the presence of serum human herpesvirus-6 immunoglobulin M antibodies, and a rise in serum human herpesvirus-6 immunoglobulin G antibodies. Magnetic resonance imaging demonstrated multiple, partly symmetric, necrotic lesions in the pons, medulla oblongata, thalamus, external capsules, and occipital subcortical and cortical areas. High-dose ganciclovir (18 mg/kg/day) was used as antiviral treatment, without side effects. A pharmacokinetic analysis of ganciclovir was performed. The initial recovery from severe disease was good. At 3-year follow-up, neurologic sequelae included epilepsy and ataxia. This case suggests that treatment with ganciclovir should be considered in human herpesvirus-6 central nervous system infections because the neurologic sequelae may otherwise be severe. Controlled, prospective, clinical trials are warranted, to analyze the pharmacokinetics of ganciclovir in infants.

Herpesvirus serology, aberrant specific immunoglobulin G2 and G3 subclass patterns and Gm allotypes in individuals with low levels of IgG3

One objective of this study was to determine whether IgG3-deficient individuals have an increased frequency of reactivated herpesvirus infections. Serum titres to Epstein-Barr virus (EBV) and human herpesvirus-6 were examined in 10 healthy and in 10 symptomatic persons with serum IgG3 < 0·1 g/l. Atypical titres were found in 16% of the IgG3-deficient individuals. Reactivations of these viruses thus do not seem common in IgG3 deficiency. Antigen-specific IgG responses were also determined. A lowered frequency of IgG3 to an EBV-derived peptide was found only in symptomatic, IgG3-deficient individuals. Levels of IgG2 to a bacterial polysaccharide were lowered in the same group, despite normal serum levels of total IgG2. A functional IgG2 deficiency may contribute to symptoms in IgG3 deficiency. The G3(g) allotype, known to be associated with low total IgG3, dominated in IgG3-deficient persons (13/17) independently of presence or absence of symptoms. A linkage of G3(g) to the G2(n) negative allotype, associated with low IgG2, was equally common irrespective of symptoms. G3(g) and absence of G2(n) seem to be one prerequisite for most of IgG3 deficiency combined with low specific IgG2.

Limitations of polymerase chain reaction testing for diagnosing acute Epstein-Barr virus infections

Clinicians use molecular tests to detect Herpesviridae from blood without fully appreciating limitations of testing. Studies are needed to enhance our understanding of the impact of Herpesviridae latency on molecular testing. We retrospectively performed quantitative Epstein-Barr virus (EBV) on sera from patients between the ages of 1 and 30 who demonstrated serologic evidence of acute EBV (n = 50) or remote EBV (n = 50) infection. Epstein-Barr virus DNA was detected in 70% of acutely infected and 4% of remotely infected patients. Sera from acutely infected patients had higher EBV copy number than convalescent sera. Our results suggest that serology should be performed as the initial diagnostic test for acute EBV. The role for polymerase chain reaction in immunocompromised patients with impaired antibody responses or as a 2nd-line diagnostic test when serologic results are equivocal deserves further study.

Does early EBV infection protect against IgE sensitization?

Background

There is indirect evidence that an increased infectious burden is associated with a decreased prevalence of IgE-mediated allergy during childhood.

Objective

To determine whether there is a relation between the serostatus of 13 different viruses and parentally reported infections and IgE sensitization in 2-year-old children. To investigate whether there is an interaction between cytomegalovirus (CMV) and Epstein-Barr virus (EBV) in relation to IgE sensitization.

Methods

A total of 246 infants were followed prospectively to 2 years of age with clinical examinations, skin prick test, and specific IgE analyses and through analysis of seropositivity against adenovirus, influenza, parainfluenza, respiratory syncytial virus, CMV, EBV, herpes simplex virus, human herpesvirus 6, and varicella-zoster virus.

Results

There was some evidence that IgE sensitization (24%) tended to be more common among children who were seropositive against few compared with children who were seropositive against many viruses, but this was not statistically significant, and there was no consistent trend across the groups. IgE sensitization was statistically significantly less prevalent at 2 years of age among infants who were seropositive against EBV but not other viruses (adjusted odds ratio, 0.34; 95% CI, 0.14-0.86). The interaction of seropositivity against both CMV and EBV antibodies indicated a further reduction in the risk for IgE sensitization (adjusted odds ratio for interaction, 0.10; 95% CI, 0.01-0.92), indicating effect modification associated with seropositivity against CMV.

Conclusion

Our results indicate that acquisition of EBV infection during the first 2 years of life is associated with a reduced risk of IgE sensitization, and this effect is enhanced by CMV coinfection.

Significant liver injury with dual positive IgM antibody to Epstein-Barr virus and cytomegalovirus as a puzzling initial manifestation of infectious mononucleosis

A 35-year-old man was admitted because of significant hepatic dysfunction with mild splenomegaly and intra-abdominal lymphadenopathy of unknown cause. Infectious mononucleosis was suggested by subsequently detected high fever, pharyngotonsillitis and cervical lymphadenopathy, but IgM to Epstein-Barr virus (EBV) and cytomegalovirus (CMV) showed dual positivity. A definite diagnosis of EBV-induced infectious mononucleosis was established 3 months later on the basis of seroconversion to Epstein-Barr nuclear antigen (EBNA)-IgG positivity and reduced CMV-IgM titer with persistently negative CMV-IgG. This case highlights the initial diagnostic difficulties of EBV-induced infectious mononucleosis particularly in older patients, due to concomitant abnormal humoral immunity and unusual initial manifestations such as significant liver injury and extensive intra-abdominal lymphadenopathy.

Human herpesvirus 6 infection and cytomegalovirus-specific lymphoproliferative responses in allogeneic stem cell transplant recipients

The aim of this study was to investigate the effects of HHV-6 DNAemia on the CMV specific lymphoproliferative response after allogeneic stem cell transplantation. Twenty-one allogeneic stem cell transplantation (allo-SCT) patients were included in the study. The patients were either CMV seropositive and/or had CMV seropositive donors. We studied the effects of HHV-6 infection, documented by PCR, on CMV-specific lymphocyte proliferation response and on CMV infection documented by PCR. HHV-6 DNAemia correlated with the absence of CMV-specific lymphocyte proliferation responses after allo-SCT. Three of nine patients with persistent HHV-6 DNA had a CMV-specific lymphocyte proliferative response compared to 11 of 12 patients without persistent HHV-6 DNAemia (P = 0.02). Patients with higher HHV-6 DNA levels (>100 copies) were more likely than those with lower copy numbers not to develop a CMV-specific immune response (six of nine vs one of eight; P < 0.05). Patients who were repeatedly HHV-6 positive in three or more consecutive blood samples were also more likely to need repeated courses of preemptive antiviral therapy against CMV during the first 6 months after transplantation (P < 0.001). Our data indicate the possibility that HHV-6 can suppress the development of CMV-specific immune responses and thereby could predispose to development of late CMV disease.

Differentiation of bacterial and viral pneumonia in children

BACKGROUND

A study was undertaken to investigate the differential diagnostic role of chest radiographic findings, total white blood cell count (WBC), erythrocyte sedimentation rate (ESR), and serum C reactive protein (CRP) in children with community acquired pneumonia of varying aetiology.

METHODS

The study population consisted of 254 consecutive children admitted to hospital with community acquired pneumonia diagnosed between 1993 and 1995. WBC, ESR, and CRP levels were determined on admission. Seventeen infective agents (10 viruses and seven bacteria) were searched for. Chest radiographs were retrospectively and separately reviewed by three paediatric radiologists.

RESULTS

A potential causative agent was found in 215 (85%) of the 254 cases. Bacterial infection was found in 71% of 137 children with alveolar infiltrates on the chest radiograph, while 72% of the 134 cases with a bacterial pneumonia had alveolar infiltrates. Half of the 77 children with solely interstitial infiltrates on the chest radiograph had evidence of bacterial infection. The proportion of patients with increased WBC or ESR did not differ between bacterial and viral pneumonias, but differences in the CRP levels of >40 mg/l, >80 mg/l, and >120 mg/l were significant although the sensitivity for detecting bacterial pneumonia was too low for use in clinical practice.

CONCLUSIONS

Most children with alveolar pneumonia, especially those with lobar infiltrates, have laboratory evidence of a bacterial infection. Interstitial infiltrates are seen in both viral and bacterial pneumonias.

The pathogenesis of febrile seizures: is there a role for specific infections?

Although fever is regarded as the main trigger in the pathogenesis of febrile seizures (FS), it is not supposed to be the unique causative factor. In FS, there is a strong familial predisposition. This does not exclude infections as a causative factor because subtle genetic polymorphisms have been demonstrated to affect the course of infections. We review the literature on: (1) the role of fever, especially the height of temperature, its cause, and metabolic effects induced by temperature; (2) the role of heredity; (3) the role of cytokines which play a role in the induction of fever; and (4) the role of type of infection, with emphasis on newly identified agents and improved diagnostic techniques. With modern molecular techniques such as PCR, viruses have been detected in the CSF far more often than previously thought, even in the absence of pleocytosis of the CSF. This makes it difficult to distinguish FS from acute encephalitis. FS may be caused by neuroinvasion or intracerebral activation of viruses. Further studies should focus on these options because therapeutic intervention is possible and may prevent late sequelae such as recurrent FS and subsequent epilepsy.

Etiology of community-acquired pneumonia in 254 hospitalized children

BACKGROUND

Childhood community-acquired pneumonia is a common illness, but there have been relatively few comprehensive studies of the viral and bacterial etiology in developed countries. The aim of the present investigation was to determine the etiology of community-acquired pneumonia in hospitalized children by several laboratory methods.

METHODS

In a 3-year prospective study a nasopharyngeal aspirate for viral studies and acute and convalescent serum samples for viral and bacterial serology were taken from 254 children with symptoms of acute infection and infiltrates compatible with pneumonia in the chest radiograph. The role of 17 microbes was investigated.

RESULTS

A potential causative agent was detected in 215 (85%) of the 254 patients. Sixty-two percent of the patients had viral infection, 53% had bacterial infection and 30% had evidence of concomitant viral-bacterial infection. Streptococcus pneumoniae (37%), respiratory syncytial virus (29%) and rhinovirus (24%) were the most common agents associated with community-acquired pneumonia. Only one patient had a positive blood culture (S. pneumoniae) of 125 cultured. A dual viral infection was detected in 35 patients, and a dual bacterial infection was detected in 19 patients.

CONCLUSIONS

The possible causative agent of childhood community-acquired pneumonia can be detected in most cases. Further studies are warranted to determine what etiologic investigations would aid in the management of pneumonia. With effective immunization for S. pneumoniae and respiratory syncytial virus infections, more than one-half of the pneumonia cases in this study could have been prevented.

Studies on the antibodies to human herpesvirus type 6 among Hungarian patients with asymptomatic HIV infection

The occurrence and the possible role in promoting HIV infection by human herpesvirus type 6 (HHV-6) have not yet been revealed in Hungary. In different groups of patients, serum titre of IgM and IgG antibodies, as well as avidity of IgG were quantitated by indirect immunofluorescence and an enzyme-linked immunosorbent assay, using isolate U1102 of HHV-6 variant A as antigen. In 60% of HIV-seronegative adult controls, high avidity IgG antibodies were found in low titre suggesting childhood infection. In HIV-seronegative persons with high risk behaviour for HIV-infection, both IgM and low avidity IgG were frequently found in higher titre, representing either primary or frequent reinfections, or reactivation of latent HHV-6. In asymptomatic HIV-seropositive patients, high titre of high avidity IgG antibodies was predominant, proving virus infection in the near past. These results indicate the contribution of HHV-6 to immunosuppression prior to AIDS, predisposing the organism to HIV infection.

Viral etiology of acute childhood encephalitis in Beijing diagnosed by analysis of single samples

OBJECTIVE

To understand the viral etiology of acute childhood encephalitis in Beijing.

METHODS

Ninety-seven Chinese children (between 7 months and 13 years of age) with acute encephalitis were retrospectively investigated. They were treated in Beijing Children's Hospital between June, 1991, and October, 1994. Different serologic methods (immunofluorescence assay, enzyme-linked immunosorbent assay, solid phase reverse immunosorbent test) were used for detection of IgM antibody to enteroviruses, herpesviruses, mumps, measles, rubella and Japanese encephalitis virus. The viral DNA of six herpesviruses was detected by polymerase chain reaction.

RESULTS

Viral etiology was identified in 35 of 97 (36.0%) cases. The most frequently identified pathogens were enteroviruses (15; 15.4%), followed by mumps (7; 7.2%), rubella (6; 6.1%), Japanese encephalitis virus (5; 5.1%), human herpesvirus 6 (2; 2.0%), herpes simplex virus (2; 2.0%) and Epstein-Barr virus (1; 1.0%). IgM antibody in cerebrospinal fluid was detected for enterovirus, mumps and rubella viruses.

CONCLUSIONS

Enteroviruses were the most frequent viral pathogens of acute childhood encephalitis in Beijing. Detection of IgM in cerebrospinal fluid may be useful for diagnosis in certain cases of viral encephalitis.

Human herpesvirus-6 infections

HHV-6 is ubiquitous in the community, appears to be acquired early in life, and has been proved to cause the clinical syndrome of exanthem subitum, and rarely to cause encephalitis. Like other herpesviruses, HHV-6 is capable of establishing latent infection and reactivating under a variety of stimuli. Improved diagnostic techniques have led to increased recognition of HHV-6 in the presence of many diseases, but much of the evidence for an aetiological role is inconclusive. There is accruing evidence for possible pathological roles in the immunocompromised host, but the evidence is less convincing for the range of associations otherwise listed for the normal host at the present time.

Upregulated local cytokine production in recurrent tonsillitis compared with tonsillar hypertrophy

In children with recurrent tonsillitis there may be persistent antigen deposition in tonsil tissue. even between exacerbations. If so, upregulation of immunocompetent cells should occur continuously, in contrast to tonsil tissue from children with tonsillar hypertrophy. The cytokine pattern was studied in cell suspensions prepared from tonsils obtained from 12 children undergoing tonsillectomy. The study group comprised 6 children with recurrent tonsillitis and 6 who had a history of tonsillar hypertrophy causing sleep apnea. Cytokine-producing cells (IL-1alpha, IL-1beta, TNFalpha, IL-6, IL-8, IL-2, IFNgamma, TNFbeta, IL-10 and IL-4) were characterized at the single-cell level by use of cytokine-specific monoclonal antibodies and indirect immunofluorescence technique. A constitutive production of IL-1alpha, IL-1beta, TNFalpha, and IL-8 was found in both groups (10-300/10(5) cells). However, the frequency of spontaneous IL-2, IFNgamma, TNFalpha, IL-6 and IL-10 was consistently low (10 +/- 10 cells) in both groups. Following restimulation by T-cell receptor ligation, using immobilized anti-CD3 mAb, with concentrations chosen so that it did not activate resting cells, increased frequencies of TNFalpha, IL-6, IL-8, IL-2, IFNgamma, IL-4 and 1L-10 synthesizing cells were induced in the recurrent tonsillitis group. Significantly higher incidences of IL-1beta, IL-6 and IL-2 producing cells were found in the recurrent tonsillitis group (60-200/10(5) cells, p <0.05). Microbiological evaluation in the tonsil tissue could not reveal tiny differences between the studied groups regarding bacterial or viral pathogens. However, this does not exclude persistent increased intracellular deposition of microbial antigens as a possible explanation for the elevated incidence of IL-1beta, TNF-alpha, IL-6, IL-8, IL-2, IFNgamma, IL-10 and IL-4 expressing cells noticed in patients with recurrent tonsillitis.

Chronic intestinal candidiasis as a possible etiological factor in the chronic fatigue syndrome

The chronic candidiasis syndrome, also known as the Candida-related complex, putatively caused by the overgrowth of Candida albicans in the gastrointestinal tract and secondarily in the genital organs, is briefly described. Patients with this disorder have many of the same symptoms as those with the chronic fatigue syndrome, except for the recurrent flu-like symptoms of the latter disorder. The positive response of a large number of patients with the chronic fatigue syndrome (CFS) to an oral antifungal agent and a diet for intestinal candidiasis has been described by another clinician. There is evidence that Candida albicans infection of the mucous membranes depresses T cell and natural killer (NK) cell function. Similar abnormalities of immune function are found in the CFS. The function of cytotoxic T cells, T helper cells, and NK cells is important in preventing reactivation of infections from Epstein-Barr virus, cytomegalovirus, and other herpesviruses. Reactivation of one or more of these viruses could lead to the expression of the flu-like symptoms in the CFS. Yet the immune dysfunction found in this disorder has been considered the primary underlying causal factor. It is proposed that chronic intestinal candidiasis may be an agent which leads to immune depression in many CFS patients and therefore that it could be a causal factor in CFS.

Serological response of paediatric oncology patients to human herpesvirus-6

The serological response of paediatric oncology patients to human herpesvirus-6 (HHV-6) was investigated at presentation and during treatment. Sera from 66 patients presenting with malignancy and 66 controls were examined for anti-HHV-6 IgG by indirect immunofluorescence test (IFA) and enzyme linked immunosorbent assay (ELISA), and for anti-HHV-6 IgM by IFA. Serial samples from 45 children on chemotherapy were examined for anti-HHV-6 IgG by ELISA and sera from selected patients on chemotherapy were examined for IgM by IFA. The response of these patients to four other herpesviruses was also investigated. Ninety percent of presenting patients and controls were IgG positive for HHV-6 by IFA and ELISA. Anti-HHV-6 IgG as measured by the HHV-6 ELISA index declined over time in patients on chemotherapy. Two presenting controls and one leukaemic child with a primary cytomegalovirus seroconversion were anti-HHV-6 IgM positive. In the patient group seropositivity to herpesviruses (types 1-6) increased with age, the mean age of those with IgG to HHV-6 alone was 3.7 years compared to 6.8 years for those with antibodies to all five viruses. At the time of presentation paediatric oncology patients have a similar serological response to HHV-6 as age-matched controls and this IgG response wanes with treatment. Whether this is significant in terms of viral pathogenicity is not known and will require investigation of viral activity in these patients.

An enzyme-linked immunosorbent assay for the detection of IgG and IgM antibodies to human herpesvirus type 6

A lysate of human herpesvirus type 6 (HHV6) infected HSB2 cells was used as antigen for an enzyme-linked immunosorbent assay (ELISA) for the detection of IgG and IgM antibody to HHV6. 78 clinical samples were tested for the presence of HHV6-specific IgM. Nine specimens, all from children under 4.5 years of age, were found to be reactive indicating probable acute infection with HHV6. Sera from 12 healthy adult blood donors and from 88 of 90 adults over the age of 35 with unspecified health conditions tested negative for HHV6 IgM, indicating a minimum specificity estimate of nearly 98% in these patients. Cross-reactivity of antibody to other herpes viruses with the HHV6 ELISA antigen was not detected. Six hundred and ninety-six serum samples from individuals of different age groups were examined for IgG antibody status. In 94% of these samples, IgG antibody was detected. Our data suggests that most Canadians possess antibody to HHV6 by 1 yr of age and that on average, antibody levels remain high through early adulthood but begin to decline with advancing age. The ELISA described is a reliable test for the measurement of IgG and IgM antibodies for both clinical diagnosis and epidemiological studies.

Avidity of IgG antibodies to human herpesvirus-6 distinguishes primary from recurrent infection in organ transplant recipients and excludes cross-reactivity with other herpesviruses

A newly developed IgG antibody avidity test for human herpesvirus-6 (HHV-6) was used in a study of primary and recurrent HHV-6 antibody responses in immunocompromised solid organ graft recipients. In a primary HHV-6 infection low avidity antibody was detected which matured to high avidity within 5 months whereas, in contrast, high avidity antibody was found in three recurrent infections thus showing the ability of the test to discriminate between primary and recurrent infection in immunosuppressed patients. Six HHV-6 seropositive transplant patients who experienced a subsequent primary human cytomegalovirus (CMV) infection had high avidity concurrent HHV-6 antibody rises, thus excluding a cross-reaction from the low avidity antibodies generated in the primary CMV response and providing evidence of recurrent HHV-6 infection. Four further HHV-6 seropositive patients with proven primary Epstein-Barr virus (EBV) infection were also studied; in each of these cases high avidity HHV-6 antibody rises were seen likewise suggesting recurrent HHV-6 infection. The test is therefore of value in the investigation of herpesvirus infections in transplant patients.

Herpesvirus serology, aberrant specific immunoglobulin G2 and G3 subclass patterns and Gm allotypes in individuals with low levels of IgG3

One objective of this study was to determine whether IgG3-deficient individuals have an increased frequency of reactivated herpesvirus infections. Serum titres to Epstein-Barr virus (EBV) and human herpesvirus-6 were examined in 10 healthy and in 10 symptomatic persons with serum IgG3 < 0.1 g/l. Atypical titres were found in 16% of the IgG3-deficient individuals. Reactivations of these viruses thus do not seem common in IgG3 deficiency. Antigen-specific IgG responses were also determined. A lowered frequency of IgG3 to an EBV-derived peptide was found only in symptomatic, IgG3-deficient individuals. Levels of IgG2 to a bacterial polysaccharide were lowered in the same group, despite normal serum levels of total IgG2. A functional IgG2 deficiency may contribute to symptoms in IgG3 deficiency. The G3(g) allotype, known to be associated with low total IgG3, dominated in IgG3-deficient persons (13/17) independently of presence or absence of symptoms. A linkage of G3(g) to the G2(n) negative allotype, associated with low IgG2, was equally common irrespective of symptoms. G3(g) and absence of G2(n) seem to be one prerequisite for most of IgG3 deficiency combined with low specific IgG2.

Seroprevalence of antibodies against human herpesvirus 6 in the Quebec City area

Seroprevalence of antibodies against human herpesvirus 6 was determined in a sample of 303 randomly selected individuals from the Quebec City area. The influence of different variables on antibody litres was also evaluated. Human herpesvirus 6 was grown in the HSB-2 cell line, and antibody litres were measured by indirect immunofluorescence. Serum samples were collected from 177 females and 126 males ranging in age from two months to 88 years. Ninety-nine per cent (300 of 303) of this population had an antibody titre of at least 1:10, whereas 75% had a titre of at least 1:80. Women had a higher geometric mean litre than men (P=0.06). This difference between sexes varied according to age and became statistically significant in subjects older than 20 years of age (P=0.04). It was found that this difference was attributable to higher antibody litres in women in the 15 to 40 year age group who had previously had children.

Primary and recurrent cytomegalovirus infections have different effects on human herpesvirus-6 antibodies in immunosuppressed organ graft recipients: absence of virus cross-reactivity and evidence for virus interaction

The relationship between serum antibodies to human herpesvirus-6 (HHV-6) and cytomegalovirus (CMV) infection was studied in immunosuppressed adult organ graft recipients all of whom had IgG to both HHV-6 and Epstein-Barr virus capsid antigen (EBVCA) before operation and who had received an organ or organs from HHV-6 seropositive donors. In primary CMV infection the titre of IgG to HHV-6 rose substantially (between 32- and 512-fold) in eight out of eight patients whereas IgG to EBVCA only rose 32-fold in two patients. Moreover, the HHV-6 responses coincided closely with the CMV seroconversion. Serum absorption studies gave no evidence for antibody cross-reaction between CMV and HHV-6 because the CMV antibody titre could be reduced specifically without affecting HHV-6 antibody titres and vice versa. In recurrent CMV infection, HHV-6 antibody levels rose (32-fold) in three out of eight patients but these changes did not coincide with the CMV antibody response. Similarly, in the complete absence of CMV infection, five out of eight patients showed antibody rises to HHV-6 (between four- and 16-fold). IgG titres to EBVCA were stable in both these groups of patients. It is concluded that there is serological evidence (rising titre greater than or equal to four-fold) for genuine HHV-6 reactivation or, alternatively, for reinfection in 16 out of the 24 patients. This phenomenon was most frequent in primary CMV infection where the largest HHV-6 antibody responses were seen probably because of an, as yet, undetermined interaction between the two viruses.

An enzyme-linked immunosorbent assay for IgG antibodies to human herpes virus 6

An indirect enzyme-linked immunosorbent assay (ELISA) with human herpes virus 6 (HHV6) membrane antigen was compared with indirect immunofluorescence assay (IFA) for measurement of HHV6 IgG antibodies. Five hundred serum samples from 403 Swedish patients with suspected symptomatic Epstein-Barr virus (EBV) infections were examined. The specificity of the ELISA compared with IFA was 98.7% and the sensitivity was 98.4%. In 90% of the patients, IgG antibodies to HHV6 were detected with both assays. The highest HHV6 IgG titers were found mainly in patients with EBV or CMV infections, but HHV6 mononucleosis was not diagnosed. The same HHV6 antigen was assessed for IgM ELISA but was found to be of limited value due to high IgM reactivity with the control antigen. The HHV6 IgM ELISA requires further investigation. The IgG ELISA described is a reliable alternative to IFA for measurement of HHV6 IgG antibodies and for large scale epidemiological studies.