Targeted cleavage of HIV-1 coreceptor-CXCR-4 by RNA-cleaving DNA-enzyme: inhibition of coreceptor function.

HIV needs the chemokine receptors (HIV-1 coreceptors) to initiate infection and gain entry into a susceptible cell. CCR5 receptor is used by macrophage tropic viruses to establish infection, and CXCR-4 is used by T lymphocyte tropic virus which are usually found at the terminal stages of the disease. These chemokine receptors are, therefore, attractive targets to interfere with the entry as well as spread of HIV-1 in the host. As our antiviral approach, we have earlier assembled a DNA-enzyme-916 against CCR5 (Goila and Banerjea, 1998). We have now designed against the CXCR-4 gene a mono-DNA-enzyme, which showed sequence specific cleavage activity. When CXCR-4-DNA-enzyme was placed in tandem with CCR5-DNA-enzyme, specific cleavage of their respective target sites were observed using a 60 bases long synthetic target RNA which possessed the target sites for both the DNA-enzymes. The cleavage by the CXCR-4 DNA-enzyme was found to be significantly more efficient than by the CCR5-DNA-enzyme. Analyses of the cleaved fragments by mono- and di-DNA-enzyme indicated strongly that hybridization of the CCR5-DNA-enzyme with its cognate target RNA, actually facilitated the cleavage by the CXCR-4 DNA-enzyme. Furthermore, the di-DNA-enzyme was able to cleave the substrate RNA to completion. These DNA-enzymes, when introduced into a mammalian cell line expressing the appropriate chemokine receptor, interfered specifically with the HIV-1 coreceptor functions. Using this strategy, it may be possible to interfere with the infection and spread of R5 as well as X4 viruses.