Yuji Kajita

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.

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.

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.

Prospective study of persistence and excretion of human herpesvirus 6 in patients with exanthem subitum and their parents.

Objective. To elucidate persistence of human herpesvirus-6 (HHV-6) in the blood and excretion of the virus into several body fluids of patients with exanthem subitum (ES), and to examine serologic and virologic findings of the parents caring for the patients in the family setting. Materials and Methods. During a 15-month period, 20 infants from 20 families (11 boys and 9 girls; mean age, 7.7 months; range, 4–11 months) with primary HHV-6 infection and a typical clinical course of ES, and 15 parents from the 20 families (2 males and 13 females; mean age, 28.2 years; range, 21–34 years) were enrolled in the study and examined clinically and virologically. Primary infection with HHV-6 was confirmed by isolation of the virus from peripheral blood mononuclear cells (MNCs), and seroconversion or a significant increase in the antibody titers to HHV-6 by a neutralization test. Viral persistence or excretion was examined by amplifying the viral deoxyribonucleic acid (DNA) in serially collected peripheral blood MNCs, plasma, saliva, stool, and urine samples with a nested polymerase chain reaction method. Data on saliva from the parents were compared with those of 21 age-matched controls. Results. Twenty infants with virologically confirmed ES had HHV-6 DNA in MNCs persistently during and after the disease but in plasma only in the first 5 days of ES. The viral DNA was also detected persistently or intermittently in saliva and stool during and after the disease but rarely in urine. On the other hand, the 15 parents examined of the 20 infants had no HHV-6 viremia nor viral DNA in peripheral blood MNCs and plasma except 1, but half of them excreted viral DNA in saliva during and after ES. The frequency of excretion of viral DNA into saliva was not significantly different from that of 21 control parents. Only 1 of the 15 showed a fourfold increase in antibody titers to HHV-6 after possible exposure from their children. Conclusions. After systemic replication of HHV-6 in the blood of patients with ES during the first 5 days of the disease, the virus is excreted into saliva and stool persistently or intermittently but rarely into urine. The presence of HHV-6 DNA in plasma suggested active infection with the virus. Excretion of the virus into the saliva of infants with ES and their parents suggests the source and transmission route of infection with HHV-6.

Experience with live attenuated varicella vaccine (Oka strain) in healthy Japanese subjects; 10-year survey at pediatric clinic

Live attenuated varicella vaccine (Oka strain, Biken Institute, Osaka, Japan) was administered to 973 healthy individuals over a 10-year period (1987-1997) at the pediatric clinic of Showa Hospital in Japan. We evaluated the relevant serological and clinical data, which were collected by questionnaire. Seroconversion by the immune adherence hemagglutination method was documented in 94% (805/860) of the initially seronegative subjects. Of the initially seropositive subjects, 56% (63/113) showed enhancement of antibody after vaccination. Reactions to the vaccine were generally insignificant, except for a rash at the injection site, seen in the first 3 days post-administration in 17% (41/241) of the recently vaccinated subjects. In March 1998, we conducted a survey of 559 of the initially seronegative subjects who had received the vaccine 0.6-10. 8 (mean 5.4) years earlier. Of these subjects, 21% (119/559) contracted breakthrough varicella. However, their symptoms were milder than those caused by natural varicella seen in unvaccinated children. Seroconversion was demonstrated in 92% (109/119) of these cases. The incidence of breakthrough disease decreased with a rise in postvaccination antibody titer to >==32. Four of the subjects (0.7% of 559) developed herpes zoster following vaccination, two of whom had earlier exhibited breakthrough varicella. Lesions in one case of zoster, without breakthrough varicella, appeared on the cervical dermatome at the injection site. The vaccine was safe and effective. However, there was a relatively high incidence of rash at the injection site with certain lot numbers used in recent years which warrants investigation.

Characterization of acyclovir susceptibility and genetic stability of varicella-zoster viruses isolated during acyclovir therapy

We have characterized the susceptibility and genetic stability of varicella-zoster viruses (VZV) isolated from skin lesions of three patients with herpes zoster and six patients with varicella treated with conventional short-term acyclovir (ACV) administration. The susceptibilities to ACV of the serial isolates from the patients were examined, and there was no significant difference in the susceptibility to ACV among the isolates before and during the ACV treatment, indicating that conventional short-term ACV treatment did not generate ACV-resistant VZV infections. Polymerase chain reaction (PCR) analyses of these as well as seven thymidine kinase-deficient VZV strains derived from in vitro ACV treatment were carried out to examine their genomic stability. Five regions containing tandem direct reiterations (R1-R5) were amplified by PCR and compared, and the region containing the Pst I-site was also examined. PCR analyses demonstrated that the R1, R5 and the Pst I-sites were stable and useful in epidemiological studies even after ACV treatment. The R2, R3 and R4 sites were far less stable in these experimental conditions. In this paper we discuss the results of the PCR analyses with regard to the dynamics of VZV population in patients with VZV infection treated with conventional short-term ACV administration.

Isolation of varicella-zoster virus from vesicles in children with varicella.

Varicella‐zoster virus (VZV) was isolated from 29 samples of the vesicular fluid in 13 otherwise healthy children with varicella who were aged from 7 months to 7 years. Human embryonic lung cells were used for viral isolation, and VZV was identified by a characteristic cytopathic effect and an indirect immunofluorescence assay. VZV was found in 17 samples; in two (12%) of which it was also detected after filtration (0.45 μm). The rate of isolation was 100% in the first two days after the onset of the disease. It declined gradually with time to 1 of 6 in the samples 6 days after the clinical onset. Specific IgG antibody to VZV was investigated in the same materials. The positive rate was 0% (0/13) in the first 3 days and increased to 7 of 16 in the following 3 days after the onset. VZV was not isolated from samples with specific antibody. In conclusion, VZV can be isolated easily from vesicles within the first 3 days of onset, but the filtration of samples affects its isolation. Infective VZV disappears gradually in vesicles after the first 3 days, and this may be related to the establishment of immune reactions including specific antibody.

Clinical and serological studies on CAM-70 live attenuated measles vaccine: an 18-year survey at a pediatric clinic in Japan

Live attenuated measles vaccine chorioallantonic membrane-70 (CAM-70) was administered to 471 healthy individuals over an 18-year period (1982-1999) at the pediatric clinic of Showa Hospital in Japan. Seroconversion occurred in 95.4% (418/438) of initially seronegative subjects. Reactions to the vaccine were generally insignificant, except for vaccine-related fever in about 20%. In February 2000, we made a questionnaire survey of 272 initially seronegative subjects who were vaccinated, from 0.7 to 18.1 years (mean: 5.5 years) earlier. Six (2.2%) of them contracted breakthrough measles during follow-up. The vaccine was generally safe and effective. However, it warrants investigation that the incidence of breakthrough measles may increase in the future in Japan.