Comparison of seroprevalences of human herpesvirus-6 and -7 in healthy blood donors from nine countries

Background and objectives: The purpose of the study was to register antibod y prevalences of HHV-7 in various locations of the world in comparison to t he closely related HHV-6. Materials and Methods: Sera of healthy blood dono rs from nine countries in five continents were titered by indirect immunofl uorescent assays using HHV-6 infected HSB2 and HHV-7 infected SupT1 cells. Results: Antibody prevalence for HHV-7 is high (75-98%) in practically all countries except for Northern Japan (44%), with no simple correlation to el evated HHV-6 antibody titers. There were regions of low, intermediate and h igh mean antibody titers against HHV-7 such as 78.5-91.3 for Belgium, Israe l, Japan, USA and Australia, 175.4-182.6 for Mexico and Cologne/Germany, an d 389.2 for South Africa for which geographic characteristics may be respon sible. Conclusion: HHV-7, similar to HHV-6 is a widespread human herpesviru s with elevated antibody titers in the healthy human population essentially everywhere. The data warrant further studies to evaluate its possible path ologic potential, preferentially in persons with defective immune responses .