Human Herpesvirus 6 Antibodies in Β-thalassemia/ Hemoglobin E Pediatric Patients

Human herpesvirus 6 (HHV-6) is a viral pathogen that causes exanthem subitum in children. It has also been identified as the cause of life-threatening illness in immunocompromised pediatric patients and transplant recipients. We undertook a serological study of HHV-6 IgM and IgG antibody among 29 children (12 females and 17 males) with β-thalassemia/ HbE disease. The rate of infection was 86.2%; the rates of early recent infection (IgM positive only), recent infection (both IgM and IgG positive) and past infection (IgG positive only) were 13.8%, 41.4% and 31.0%, respectively. The geometric means of the IgM and IgG titers of the splenectomy group (9 cases) were 10.15 units and 11.18 units, respectively. The geometric means of the IgM and IgG titers of the non-splenectomy group (20 cases) were 10.10 units and 12.84 units, respectively. According to this study, the prevalence of HHV6 infection among pediatric patients with β-thalassemia/HbE is very high; morever, the significantly higher titer among these patients may imply a high risk for further possible bone marrow transplantation. Increased awareness of HHV-6 infection among this population is necessary. We conducted a seroprevalence survey of HHV-6 serology among children with β-thalassemia/ HbE disease, a common congenital hematological disorder in Southeast Asia. This group can be classified as being at risk of infection. Most of these patients require frequent blood transfusions, which puts them at risk of acquiring blood-borne infections. In addition, the virus replicates in the salivary glands, is secreted in saliva, which is a proven source of infection. Other possible modes of transmission warrant investigations, such as the transfusion of blood products, especially as HHV-6 infection in immunocompromised hosts can lead to severe complications and even death (Crawford, 1993; Sayers, 1994; Campadelli-Fiume, 2000). MATERIALS AND METHODS Subjects Twenty-nine children (aged 0 to 15 years) with βthalassemia/HbE disease who visited the Pediatric Hematology Clinic, Department of Pediatrics, Faculty of Medicine, Chulalongkorn University between April and December 2000 were enroled in the study. All cases were transfusion-dependent with regular follow-up at the clinic; none had a past history of HIV or viral hepatitis. Informed consent was obtained from each subject’s parents before the collection of blood samples. Laboratory investigation Three milliliters of clotted blood were collected from each subject. All samples were allowed to clot at room temperature and then centrifuged. The sera INTRODUCTION Human herpes virus type 6 (HHV6) is a member of the herpes virus group. It was first isolated in 1985 and was included in the Herpesviridae family and the beta-herpes virinae subfamily, mainly on the basis of its genomic similarities with the human cytomegalovirus (HCMV). HHV-6 is widely distributed in the population. Seroconversion takes place very early, most often before three years of age (Tirdei et al, 1994). The majority of infections are self-limiting, asymptomatic, and occur before 2 years of age. Symptomatic infections include exanthem subitum. Seroprevalence in adults may reach 100%. A recent study suggests that there are clinical syndromes associated with the presence of anti-HHV-6 IgM, in which serological screening for evidence of acute HHV-6 infection may be useful (Irving et al, 1990). More severe primary infections may include hepatitis, meningoencephalitis, interstitial pneumonitis, and mononucleosis-like syndrome (Irving et al, 1990; Liedtke et al, 1995). In immunosuppressed patients (such as transplant recipient), primary HHV-6 infection or reactivation may induce a rejection of transplanted organs which may prove fatal (Brion et al, 1995). Correspondence: Chaiyaporn Boonchalermvichian, Department of Laboratory Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok 10300, Thailand. SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH 150 Vol 33 (Suppl 3) 2002 Ig G ( un its ) 20.00