Negatively charged
albumins (NCAs, with the prototypes
Suc-HSA and
Aco-HSA), modified
proteins with a potent anti-HIV-1 activity in the nanomolar concentration range, were studied for several aspects of their
antiviral mechanism. In addition we investigated the
antiviral activity of combinations and covalent conjugates of these NCAs and the
reverse transcriptase inhibitor AZT. Addition of NCAs to HIV-1-infected target cells in time-of-addition experiments could be delayed for 30 min after
infection before significant loss of activity occurred. Syncytium formation of HIV-infected and uninfected T-cells was inhibited by the NCAs at concentrations of 1-4 microg/ml. The gp120-mediated virus/cell binding, however, was only inhibited by the NCAs at a 10-fold higher concentrations. The combined data are compatible with a preferential influence on virus/cell fusion. A subsynergistic activity against HIV-1 was observed with the non-covalent mixture of
Aco-HSA and AZT. When AZT was covalently coupled to the NCAs, and added one hour after
infection of the target cells, the anti-HIV-1 activity of NCA-
AZTMP was diminished by only 2-6-fold, while this was diminished at least 120-fold for the NCAs. Furthermore the addition of NCA-
AZTMP could be delayed up to at least 3 h after
infection without loss of
antiviral activity. It is concluded that AZT that was coupled to the NCAs significantly contributes to the overall
antiviral activity of the conjugates leading to complementary effects. These results highlight the potential of using NCA-
AZTMP as dual-targeting preparations against HIV-1 in which both the carrier and the coupled
drug contribute to the therapeutic efficacy acting at a different level in the replication cycle.