Preferential Targeting of CD4-CCR5 Complexes with Bifunctional Inhibitors: A Novel Approach to Block HIV-1 Infection

Two receptors, CD4 and one of several chemokine receptors, are required for cellular HIV-1 infection, with CCR5 being the main coreceptor for macrophage-tropic strains. We have designed bifunctional fusion proteins, consisting of RANTES/CCL5 and a single-chain Fv Ab fragment against CD4 to simultaneously block CD4 and CCR5. The fusion proteins bind to both receptors, compete with RANTES/CCL5 binding, and induce down-modulation of CCR5 ∼10 times more efficiently on CD4+ compared with CD8+ T cells. Moreover, after short incubation and subsequent washout, a significant down-modulation of CCR5 was only seen with the fusion proteins and only on CD4+ cells, but not with unmodified RANTES or on CD4− cells, indicating a preferential targeting of CCR5 on CD4+ T cells. The fusion proteins block M-tropic HIV infection more efficiently than RANTES/CCL5 and CD4 Abs alone or in combination. To our knowledge this is the first report of simultaneous blockade of an HIV-1 receptor and coreceptor with bifunctional inhibitors.