PERSISTENCE OF HUMAN-HERPESVIRUS-6 ACCORDING TO SITE AND VARIANT - POSSIBLE GREATER NEUROTROPISM OF VARIANT-A

Little is known of the persistence and pathogenicity of human herpesvi rus 6 (HHV-6) after primary infection, including the role of strain va riant. Over 2 to 5 years, 2,716 children and 149 families were studied . Peripheral blood mononuclear cell (PBMC), saliva, and cerebrospinal fluid (CSF) specimens were examined for HHV-6 DNA and variant, Ninety- nine percent of isolates causing primary infection were HHV-6 variant B (HHV-6B), which predominated in 95%-98% of the variants persisting i n PBMC and saliva specimens from children and adults. Of 668 CSF sampl es, 13% contained HHV-6 DNA; of 77 children examined after primary inf ection, 61% had HHV-6 DNA detected only in their CSF and 39% had HHV-6 DNA in both CSF and PBMCs. HHV-6 variant A (HHV-6A) was detected sign ificantly (P = .0001) more frequently in CSF than in PBMCs or saliva. in children for whom HHV-6 was identified in both CSF and PBMCs, PBMCs contained only HHV-6B, while CSF contained HHV-6A or HHV-6B, not both . Thus, in patients with dual infection, only HHV-6A persisted in CSF, which suggests that HHV-6A has greater neurotropism. Findings for adu lts indicate that dual infection occurs; variant persistence is simila r to that for children, The frequency of HHV-6A infection increased li ttle with age, thereby indicating that HHV-6A infection remains uncomm on into adulthood. This study suggests that HHV-6 variants have differ ent immunobiologic courses and neurotropism.