Sadao Suga

Fatal encephalitis/encephalopathy in primary human herpesvirus-6 infection.

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.

Human herpesvirus 6 viremia in bone marrow transplant recipients: clinical features and risk factors.

Human herpesvirus 6 (HHV-6) infection was studied in 82 bone marrow transplant (BMT) recipients (72 allogeneic, 10 autologous). All recipients and 30 donors were seropositive for HHV-6 antibody at the time of bone marrow transplantation. Thirty-one recipients (37.8%) had HHV-6 viremia 2-4 weeks after transplantation. The incidence of HHV-6 viremia was significantly higher among allogeneic BMT recipients than in autologous BMT recipients (P=.011). Therefore, the following analyses of allogeneic BMT recipients were carried out (n=72). Geometric mean antibody titers (log(10)) were significantly higher in recipients without viremia than in those with viremia (1.84+/-0.39 vs. 1.61+/-0.42; P=.022). Logistic regression analysis demonstrated that leukemia or lymphoma is an independent risk factor (P=.031) for HHV-6 viremia. Rash occurring within 1 month after transplantation was observed in 17 (54.8%) of 31 recipients with HHV-6 viremia but in only 8 (19.5%) of 41 recipients without HHV-6 viremia (P=.001).

Viremia and neutralizing antibody response in infants with exanthem subitum

Mononuclear cell-associated viremia caused by human herpesvirus type 6 was detected in 39 (66%) of 59 blood samples from 38 children with exanthem subitum between day 0 and day 7 of the disease. The rate of virus isolation from mononuclear cells was 100% (26/26) on days 0 to 2 (just before appearance of skin rash), 82% (9/11) on day 3, 20% (2/10) on day 4, 7% (2/12) on days 5 to 7, and 0% (0/37) on day 8 and thereafter. The cell-free virus was detected in blood in 10 (21%) of 47 blood samples during the same period. The antibody activity to the virus, evaluated by a newly developed neutralization assay, was first detected on day 3 of the disease with a positive rate of 18% (2/11). It became 60% (6/10) on day 4, 75% (9/12) on days 5 to 7, and 100% on day 8 and thereafter. Thus the disappearance of the virus from blood was associated with the induction of specific immunity to the virus.

Rapid Diagnosis of Herpes Simplex Virus Infection by a Loop-Mediated Isothermal Amplification Method

ABSTRACT Primers for herpes simplex virus type 1 (HSV 1)-specific loop-mediated isothermal amplification (LAMP) method amplified HSV-1 DNA, while HSV-2-specific primers amplified only HSV-2 DNA; no LAMP products were produced by reactions performed with other viral DNAs. The sensitivities of the HSV-1- and HSV-2-specific LAMP methods, determined by agarose gel electrophoresis, reached 500 and 1,000 copies/tube, respectively. The turbidity assay, however, determined the sensitivity of the HSV-1- and HSV-2-specific LAMP methods to be 1,000 and 10,000 copies/tube, respectively. After initial validation studies, 18 swab samples (in sterilized water) collected from patients with either gingivostomatitis or vesicular skin eruptions were examined. HSV-1 LAMP products were detected by agarose gel electrophoresis in the 10 samples that also demonstrated viral DNA detection by real-time PCR. Nine of these 10 samples exhibited HSV-1 LAMP products by turbidity assay. Furthermore, both the agarose gel electrophoresis and the turbidity assay directly detected HSV-1 LAMP products in 9 of the 10 swab samples collected in sterilized water. Next, we examined the reliability of HSV type-specific LAMP for the detection of viral DNA in clinical specimens (culture medium) collected from genital lesions. HSV-2 was isolated from all of the samples and visualized by either agarose gel electrophoresis or turbidity assay.

Clinical characteristics of febrile convulsions during primary HHV-6 infection

OBJECTIVE To clarify clinical characteristics of children with febrile convulsions during primary human herpesvirus 6 (HHV-6) infection. SUBJECTS AND METHODS The clinical characteristics of first febrile convulsion were compared between those with and without primary HHV-6 infection in 105 children. HHV-6 infection was verified by culture or acute/convalescent anti-HHV-6 antibody titres. RESULTS Primary infection with HHV-6 was seen in 21 of 105 patients with febrile convulsions (3 upper respiratory infection, 1 lower respiratory infection, and 17 exanthem subitum). 13 of 23 patients < 1 year, 19 of 79 patients with first febrile convulsion, and 2 of 15 with second convulsion were infected with HHV-6. The median age of patients with first febrile convulsion and HHV-6 was significantly lower than those without infection. The frequency of clustering seizures, long lasting seizures, partial seizures, and postictal paralysis was significantly higher among those with primary HHV-6 infection than among those without. The frequency of atypical seizures in 19 patients with first febrile convulsion associated with primary infection was significantly higher than in 60 patients without primary infection. The frequency in infants younger than 1 year of age was also significantly higher than that in 10 age matched infants without primary infection. CONCLUSIONS These findings suggest that primary infection with HHV-6 is frequently associated with febrile convulsions in infants and young children and that it often results in the development of a more severe form of convulsions, such as partial seizures, prolonged seizures, and repeated seizures, and might be a risk factor for subsequent development of epilepsy.

Rapid Diagnosis of Human Herpesvirus 6 Infection by a Novel DNA Amplification Method, Loop-Mediated Isothermal Amplification

ABSTRACT 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 methods 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.

A prospective study of human herpesvirus-6 infection in renal transplantation

Sixty-five kidney transplant recipients and their (22 living related and 43 cadaveric) donors were studied prospectively to determine the relationship between kidney transplantation and human herpesvirus-6 (HHV-6) infection. The virus isolation from peripheral blood and other tissues and sequential determination of neutralizing antibodies to HHV-6 were performed during 3 months following the transplantation. All of the donors and their recipients examined had neutralizing antibodies to HHV-6 at the time of renal transplantation and the virus was not isolated from them. HHV-6 was isolated from 3 renal tissues (2 living related and 1 cadaveric) obtained during transplant surgery, but not from their blood at that time. HHV-6 viremia occurred in 9 (14%) of the 65 recipients around 2 to 4 weeks after the transplantation. An additional 27 recipients showed a significant rise in the antibody titer. Thus, the infection with HHV-6 was confirmed in 36 (55%) of the 65. These results indicate that the virus is activated in many cases in the early posttransplant period and that HHV-6 establishes in vivo latency in the kidney tissue. There was no correlation between HHV-6 infection and acute rejection or the antirejection prophylaxis.

Analysis of rotavirus antigenemia and extraintestinal manifestations in children with rotavirus gastroenteritis.

OBJECTIVE. This study was conducted to examine the association between rotavirus antigenemia and clinical features, particularly extraintestinal manifestations, and the association between serum cytokine levels and rotavirus antigen quantity. METHODS. Sixty hospitalized children who received a diagnosis of acute rotavirus gastroenteritis were enrolled in this study. Paired serum samples were collected from the 60 children when admitted to and discharged from the hospital. Associations among viral antigen levels and fever, elevated transaminase levels, and seizures were evaluated to determine whether antigenemia correlated with disease severity. Viral antigen was measured by using an in-house enzyme-linked immunosorbent assay that detected VP6 antigen. A flow-cytometric bead array was used to measure serum cytokine levels. RESULTS. Rotavirus antigen levels were significantly higher in serum collected at the time of hospital admission than at the time of discharge. Serum rotavirus antigen levels peaked on day 2 of the illness (2.02 ± 0.73), followed by a gradual decrease in antigen levels to nearly undetectable levels by day 6. The quantity of rotavirus antigen was significantly higher in serum collected from patients with fever than those without fever. The presence or absence of elevated transaminase levels and seizures was not associated with serum rotavirus antigen levels. A weak but significantly positive association was observed between interleukin 8 levels and antigenemia. A weak but significantly negative association was observed between interleukin 10 levels and antigenemia. CONCLUSIONS. Rotavirus antigenemia is frequently observed in a patients serum during the acute phase, and viral antigen levels change dramatically during the acute phase of the illness. Because patients with fever had higher rotavirus antigen levels, antigenemia severity might contribute to fever. The host immune response plays an important role in controlling antigenemia levels.

Severity of human herpesvirus-6 viremia and clinical findings in infants with exanthem subitum.

The degree of viremia with human herpesvirus-6 was evaluated in 176 blood samples from 89 infants with exanthem subitum and viremia, and compared with the severity of clinical features and complications of the disease. Fever persisted for 3 to 4 days in 73% of infants and for more than 5 days in 22%, followed by a rubella- or measles-like rash. The viremia was observed between the first day of fever (day 0) and day 4 of the disease. The number of infected cells per 10 million mononuclear cells was 3.45 +/- 1.00 (log10, mean +/- SD) on days 0 to 2, 3.30 +/- 1.14 on day 3, and 3.09 +/- 2.05 on day 4 of the disease. The number of infected cells on days 3 to 4 in infants with a febrile period longer than 4 days and free virus in plasma was significantly greater than that in infants with a febrile period of less than 3 days and without free virus in plasma. The amount of virus in blood on days 0 to 2 did not relate to the duration of fever, and that on days 0 to 4 did not relate to the presence or absence of diarrhea, bulging fontanelle, or bronchopneumonia. These findings suggest that the magnitude of the virus replication in infants with exanthem subitum is reflected in the severity of the disease.

Detection of Human Herpesvirus 7 DNA by Loop-Mediated Isothermal Amplification

ABSTRACT The reliability of loop-mediated isothermal amplification (LAMP), initially developed for the detection of human herpesvirus 7 (HHV-7), was evaluated in this study. Although a LAMP product was detected in HHV-7 DNA, neither HHV-6 nor human cytomegalovirus DNA produced a product. When agarose gel electrophoresis was used for the detection of LAMP products, the sensitivity of a 30-min HHV-7 LAMP reaction reached 250 copies/tube. The use of turbidity for the detection of the LAMP products gave a sensitivity of 500 and 250 copies/tube for 30- and 60-min reactions, respectively. Following these initial validation studies, clinical samples collected from two patients with primary HHV-7 infections were examined by HHV-7 LAMP. By use of agarose gel electrophoresis, HHV-7 LAMP products could be detected in acute-phase plasma samples but no LAMP product was detectable in convalescent-phase plasma samples from either patient. Since a turbidity assay is less sensitive than agarose gel electrophoresis, no HHV-7 LAMP product could be detected in plasma samples after a 30-min LAMP reaction. After a 60-min LAMP reaction, HHV-7 LAMP product could be detected in acute-phase plasma samples.