Seroconversion to human herpesvirus 6 and human herpesvirus 7 among Brazilian children with clinical diagnoses of measles or rubella.
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We collected acute-phase and convalescent-phase serum samples from Brazilian patients who presented with exanthem of unknown origin and evaluated these samples by means of an immunoblot assay for seroconversion to human herpesvirus 6 (HIV-6) or human herpesvirus 7 (HIV-7). Measles or rubella had been clinically diagnosed in all these patients, but their sera were negative for antibodies to both measles virus and rubella virus. Twenty percent of the patients clearly seroconverted to HHV-6 after manifestation of the exanthem, and 8% seroconverted to HHV-7. All seroconversions to HHV-6 occurred in children aged < or = 5 years; a 41% frequency of seroconversion to HHV-6 was noted among children between 3 months and 23 months of age, whereas seroconversions to HHV-7 were detected during infancy and through adulthood. Our data indicate that primary infections due to HHV-6 or HHV-7 can be misdiagnosed as measles or rubella. (+info)
Apoptosis of CD4+ T lymphocytes in human herpesvirus-6 infection.
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The present authors have recently reported that inoculation with human herpesvirus-6 (HHV-6) renders CD4+ T lymphocytes susceptible to apoptosis in vitro. In order to confirm that apoptosis of CD4+ T lymphocytes also occurs in HHV-6 infection in vivo, apoptosis of lymphocytes isolated from nine patients with exanthem subitum and from an adult patient with severe HHV-6 infection was examined. Peripheral blood mononuclear cells were cultured for 3 days and apoptosis of lymphocytes was then examined by flow cytometry of propidium iodide-stained DNA. The percentages of hypodiploid DNA, indicating apoptosis, in lymphocytes from 10 patients with HHV-6 infection were significantly higher than those from five infant patients with noninfectious diseases and five healthy adults (P < 0-0002). DNA fragmentation was also detected by agarose gel electrophoresis in lymphocytes from patients with HHV-6 infection. Apoptosis appeared to occur predominantly in CD4+ T lymphocytes and HHV-6 was isolated from the CD4+ T lymphocyte fraction. These data demonstrate that HHV-6 renders CD4+ T lymphocytes susceptible to apoptosis in vivo. (+info)
Early diagnosis of primary human herpesvirus 6 infection in childhood: serology, polymerase chain reaction, and virus load.
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Qualitative and quantitative polymerase chain reaction (PCR) for human herpesvirus 6 (HHV-6) DNA in whole blood and plasma was correlated with serology and clinical assessment in 143 children hospitalized for undifferentiated febrile illness to evaluate options for diagnosis of primary HHV-6 infection on the acute blood specimen. PCR and serology for HHV-7 were done in parallel to define serologic cross-reactions. Using HHV-6 seroconversion as the reference standard, detection of HHV-6 DNA in whole blood in the absence of antibody in the plasma was the most reliable evidence of primary HHV-6 infection. Detection of HHV-6 DNA in plasma and a high virus load in whole blood (>3.3 log10 copies/5 microL) had a sensitivity of 90% and 100%, respectively, in diagnosing primary HHV-6 infection. However, both were occasionally found in patients with other infections, possibly associated with HHV-6 reactivation. Maternal antibody may confound interpretation of serology in patients under 3 months of age. (+info)