Inhibition of human immunodeficiency virus 1 (HIV-1) by variant B of humanherpesvirus 6 (HHV-6)

Four HHV-6 strains were initially isolated during attempts to observe HIV-1 replication in cultured primary lymphocytes from 48 patients with AIDS. HH V-6 DNA from each strain was extracted from primary cell cultures and ampli fied using specific primers in a nested polymerase chain reaction (PCR) ass ay. All HHV-6 strains were classified as B variants by submitting the PCR p roducts to the digestion of two restriction enzymes (Hind III and Bgl II). Since in primary cultures, the appearance of HHV-6 cytopathic effect was fo llowed by a progressive reduction of HIV-1 replication, we tried to reprodu ce the observed inhibition in vitro. Two HHV-6 strains, used throughout the experiments, showed their ability to suppress HIV-1 replication when the v iruses coinfected CD4+T lymphocyte cultures. While the intrinsic mechanism of this finding still remains unclear, the inhibition of HIV-1 replication was observed only when a high multiplicity of infection (M.O.I.) of HHV-6 a nd a low M.O.I. of HIV-1 were used in dually infected cell cultures. By usi ng a semiquantitative determination of HIV-1 cDNA by PCR, it appears that t he inhibition begins in infected cell cultures and, once established, does not allow any further HIV-1 replication.