Neutralizing antibody responses to human herpesviruses 6 and 7 do not cross-react with each other, and maternal neutralizing antibodies contribute to sequential infection with these viruses in childhood.
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Seroprevalence of human herpesvirus 6 (HHV-6) and HHV-7 infections is very high throughout the world, and almost all people are exposed first to HHV-6 and second to HHV-7 in their childhood. However, it is not clear whether the neutralizing (NT) antibody response between each virus is cross-reactive or not. To elucidate the NT antibody response between each virus, 55 serum samples from an adult group (subjects 22 to 88 years old) and 60 serum samples from a young group (subjects 2 to 18 years old) were examined by a dot blot method for detecting viral late antigen. Thirty-nine serum samples obtained from cord bloods and a few serum samples obtained from pediatric patients with exanthem subitum were also examined to assess the maternal transferred NT antibodies against each virus. The NT antibody titers against HHV-7 in the adult group remained high throughout all the individuals, and none were negative. Those against HHV-6 were high values in the young group but low values, including negative values (three samples), in the adult group. These results suggested that the NT antibody response to either HHV-6 or HHV-7 in each individual was specific to each virus and did not cross-react with each other. In the adult group, the NT antibody response to HHV-6 decreased, while that to HHV-7 remained high throughout all the individuals. Maternal transferred NT antibody titers against HHV-7 were higher and remained longer after birth than those of HHV-6, and these findings were in accord with the clinical observation that HHV-6 infection usually occurs earlier than HHV-7 infection. (+info)
Antibody status to HHV-6 in children with leukaemia.
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Forty children with acute lymphoblastic (33) or myeloid leukaemia (seven) were studied for IgG and IgM antibodies and IgG avidity against human herpesvirus 6 (HHV-6) at the time of diagnosis, and compared with age-, sex- and season-matched children with various neurological diseases of suspected viral origin. Of the children with leukaemia, 97.5% had IgG antibodies and 40% IgM antibodies to HHV-6 compared with 92.3% and 7.7% of reference subjects (P = 0.005). A seronegative child with leukaemia seroconverted 3 weeks after the diagnosis. The avidity of IgG antibodies (based on the resistance to urea treatment) was high in all children with leukaemia. One reference child had HHV-6-specific IgG antibodies with low avidity, which together with his positive IgM indicated an acute infection. The presence of specific IgM antibodies in 40% of children with leukaemia and the high avidity of IgG suggest a reactivation or an inaproppriate primary response to HHV-6 infection. The results support the conclusion of the role of the HHV-6 infection at the onset of childhood leukaemia. (+info)
Salazosulfapyridine induced hypersensitivity syndrome associated with reactivation of humanherpes virus 6.
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A 22-year-old woman with ulcerative colitis developed skin eruptions, liver dysfunction, and atypical lymphocytes in the peripheral blood two weeks after she started taking salazosulfapyridine (SASP). Skin eruptions and liver damage were severe. Drug-induced lymphocyte stimulation test (DLST) for SASP was positive. She was diagnosed as having SASP-induced hypersensitivity syndrome (HS). Corticosteroid therapy was needed to suppress these reactions. The transient elevation of HHV-6 IgG titer paralleled the symptoms, which indicated that these reactions were associated with the reactivation of HHV-6. We suggest that HHV-6 IgG titer is one of the modalities for the diagnosis and the prediction of the clinical course of HS. (+info)
Viral exanthems.
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Viral exanthems are mostly associated with self-limited diseases. However, in some cases diagnosis of an exanthem may be crucial to patients and their contacts. Certain exanthems have fairly characteristic morphology, but in many cases an accurate diagnosis cannot be made on the basis of morphology alone. Historical factors may be helpful when evaluating these patients, specifically their disease contacts, immunization record, previous exanthematous illnesses, and associated prodromal symptoms. Some illnesses are seasonal and this knowledge may be useful. This manuscript reviews a number of common childhood exanthems. We included the most common viral exanthems encountered by primary-care physicians and dermatologists. (+info)
Fatal encephalitis/encephalopathy in primary human herpesvirus-6 infection.
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An encephalitic illness with a fatal outcome occurred in a 9 month old girl with virologically confirmed exanthem subitum. Human herpes-virus-6 (HHV-6) DNA was found in the cerebrospinal fluid at the acute stage of the disease by the polymerase chain reaction, but the virus antigen was not detected in her brain tissue. This suggests that HHV-6-induced encephalitis/encephalopathy may be due to a non-infectious process. (+info)
Nervous complications of exanthem subitum.
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For many years it was generally believed that all convulsions associated with exanthem subitum were febrile in origin. More recently several investigators have suggested that the causative agent of this disease has a selective action on brain tissue aside from the effect of high temperature. In support of this concept are a variety of neurological manifestations sometimes observed during the course of exanthem subitum. These include prolonged and repeated convulsions, hemiparesis, headache, vomiting, bulging fontanelle, vertigo, cervical rigidity, extreme irritability and a reversal of the time of sleep. Abnormalities in the spinal fluid have been reported on a few occasions. By chance the authors observed a case of exanthem subitum that began with a prolonged and severe afebrile convulsion and transient left hemiparesis. Serial electroencephalograms showed a focal lesion with suppression and slowing in the right parietal area. Behavior disorders of brief duration were noted. This case is interpreted as additional evidence of the presence of an encephalitic process. The nature of the cerebral lesion remains unknown. The remote possibility of disturbed behavior in later life deserves consideration. (+info)
Rapid diagnosis of human herpesvirus 6 infection by a novel DNA amplification method, loop-mediated isothermal amplification.
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A novel nucleic acid amplification method, termed loop-mediated isothermal amplification (LAMP), which amplifies DNA with high specificity, efficiency, and rapidity under isothermal conditions, may be a valuable tool for the rapid detection of infectious agents. LAMP was developed for human herpesvirus 6 (HHV-6), and its reliability was evaluated in this study. Although LAMP products were detected in HHV-6 B and HHV-6 A DNA, they were not detected in HHV-7 and human cytomegalovirus DNA. The sensitivity of the original HHV-6 LAMP protocol was 50 copies/tube. In order to increase the method's sensitivity, HHV-6 LAMP was modified by increasing the primer concentration. As a result of the modification, sensitivity increased to 25 copies/tube. After these initial validation studies, 13 patients with fever were tested for HHV-6 by viral isolation, serological analysis, and HHV-6 LAMP. In three of the eight patients with primary HHV-6 infection, HHV-6 DNA was detected in whole blood by the original HHV-6 LAMP protocol in not only the acute phase but also the convalescent phase. HHV-6 DNA was detected by modified HHV-6 LAMP in all eight plasma samples collected in the acute phase; however, no HHV-6 DNA was detected in plasma samples collected in the convalescent phase. Although HHV-6 DNA was detected in both the acute and convalescent phases of whole-blood samples in patients with past HHV-6 infection, it was not detected in plasma samples that did not contain latent viral DNA. Thus, detection of HHV-6 DNA in plasma by using this modified HHV-6 LAMP protocol is appropriate for diagnosis of active HHV-6 infection. (+info)
A population-based study of primary human herpesvirus 6 infection.
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BACKGROUND: Serologic studies indicate that human herpesvirus 6 (HHV-6) infects 90 percent of children by two years of age. Little is known about the acquisition, virologic course, and clinical manifestations of HHV-6 infection. METHODS: We prospectively studied a cohort of 277 children from birth through the first two years of life to define the pattern of acquisition of HHV-6. The children's saliva was tested weekly for HHV-6 DNA with the use of the polymerase chain reaction. Parents maintained a daily log of signs and symptoms of illness in their children. RESULTS: Primary HHV-6 infection occurred in 130 children, with cumulative percentages of 40 percent by the age of 12 months and 77 percent by the age of 24 months. The peak age of acquisition was between 9 and 21 months. The acquisition of HHV-6 was associated with female sex (adjusted hazard ratio, 1.7; 95 percent confidence interval, 1.2 to 2.4) and having older siblings (adjusted hazard ratio, 2.1; 95 percent confidence interval, 1.4 to 2.9). Among 81 children with a well-defined time of acquisition of HHV-6, 93 percent had symptoms, and 38 percent were seen by a physician. None had seizures. As compared with children who had other illnesses, those with primary HHV-6 infection were more likely to have fever (P=0.003), fussiness (P=0.02), diarrhea (P=0.03), rash (P=0.003), and roseola (P=0.002) and were more likely to visit a physician (P=0.003). CONCLUSIONS: The acquisition of HHV-6 in infancy is usually symptomatic and often results in medical evaluation. Roseola occurs in a minority of patients, and febrile seizures are infrequently associated with primary HHV-6 infection. Older siblings appear to serve as a source of HHV-6 transmission. (+info)