Using mAbs and genomic probe to the CD4 molecule, the HIV receptor, we demonstrated that HIV replication induces the disappearance of its functional receptor from the cell surface by two distinct mechanisms. First, after being expressed onto the cell surface, HIV envelope gp110 will complex CD4, efficiently masking the CD4 epitope used by the virus to bind its receptor. This phenomenon occurs on the surface of each infected cell and is not due to the release of soluble gp110; infection with recombinant HIV/vaccinia viruses expressing a mutated HIV env gene designed to prevent gp110 release from the cell surface induces a similar gp/CD4 complexes formation. Second, virus replication induces a dramatic and rapid loss of CD4 mRNA transcripts, preventing new CD4 molecules from being synthesized. These two mechanisms of receptor modulation could have been developed to avoid reinfection of cells replicating the virus as well as to produce more infectious particles. These results suggest that the classical virus interference documented for other retroviruses might not only be due to receptor/envelope interaction, but might also depend on receptor gene expression.

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