Absence of antibodies to human herpesvirus-6 in patients with slowly-progressive human immunodeficiency virus type I infection

To evaluate a possible role for Human Herpesvirus-type 6 (HHV-6) coinfection as a co-factor in the progression of HIV-1 disease, we investigated the prevalence of seropositivity for HHV-6 in a cohort of HIV-1 infected patients. These patients were retrospectively divided into two groups according to the decline of CD4+ T cells during the follow up: 11 were classified as rapid decliners (<400 CD4+/cmm within 1 year), and 38 as slow decliners (> 400 CD4+/cmm after at least 4 years' follow up). HHV-6 antibodies were detected by a commercial immunofluorescence assay and by a Western blotting assay developed in our laboratory. Our results show that Western blot appears to provide results satisfactorily free of false positivities. We found that the frequency of HHV-6 seropositivity was significantly lower in the group of slow decliners, compared both to rapid decliners and to the general population. These data suggest a role for HHV-6 co-infection in the progression of HIV-1 disease.