To investigate the biological and immunological characteristics of the Nanjing local strains of HHV-7,four strains of herpesvirus were isolated from saliva specimens of one healthy individual and three children suffering from a kidney disease in Nanjing.The viruses were identified by transmission electron microscopy (EM),indirect immunofluorescence assay(IFA) with a specific monoclonal antibody;nested polymerase chain reaction,restriction mapping and DNA sequencing.The virus-infected cells showed the typical cytophathic effect(CPE) under microscopy and could be detected by IFA with the human herpesvirus-7(HHV-7) specific antibody.Under EM,herpesvirus-like and virions capsids could be found in their cytoplasm or nucleoplasm. HHV-7 DNA fragments amplified from infected cells by nested PCR were confirmed by restriction mapping and DNA sequencing.Similarly to DC strain,an known HHV-7 strain used in the present study as the positive control,the virus could be inactivated by ultraviolet irradiation for 10 min,heated at 45℃ for 30 min,pH<5 or>9 at 4℃ for 2 h and ether or chloroform for 10 h.The virus induced the production of TNF-α,IL-10 and IL-12p70 while inhibited IFN-γ secretion,increased the percentage of CD2^+ cells while decreased that of CD4^+ or CD45RA^+ cells.The results indicate that the viruses isolated in Nanjing are HHV-7,which has similar biological characteristic to the known HHV-7 strain,DC.Infection with HHV-7 in vitro could affect immune function of lymphocytes by disturbing cytokine production and CD antigen expression.Cellular & Molecular Immunology.2004;1(5):367-372.
