In the life cycle of HIV, the Rev protein regulates the temporal switch from the early regulatory to the late lytic phase by binding to a highly structured RRE (Rev Responsive Element) RNA. Two questions regarding Rev:RRE RNA interactions still remain unanswered, namely: 1) the primacy of sequence or secondary structure of RNA in determining REV binding, and 2) the roles of oligomerization and effector domains of REV protein in RNA binding. We performed real time kinetic studies of REV:RRE interactions by the SPR biosensor technique. For this purpose, we developed a novel method of immobilizing RNA on the sensor surface that may also be of general use for detecting novel nucleic acid binding proteins. To more precisely locate the RNA binding domain(s) on Rev, a series of REV peptides representing the minimal REV motifs were evaluated for RNA binding by SPR. A minimal sequence between the 23rd and 87th residues comprising the RNA binding, NLS, oligomerization and effector motifs of REV exhibited in vitro RNA binding kinetics reminiscent of REV. We have extended our studies on the effect of HIV-1 NEF protein on T lymphocyte CD4 receptor. We demonstrated that Nef downregulates CD4 expression through a bi-modal mechanism through endocytosis of cell surface receptor and repression of biosynthesis and transport of nascent CD4. We have tried to follow-up a recent report that Nef may also induce a rapid endocytosis of MHC class I receptor and the implication that Nef effect on two unrelated receptors, namely CD4 and MHC class I may derive from the ability of Nef to recruit plasma membrane adaptin molecules to the potential endocytosis targets. This interaction may subsequently serve to internalize the receptors. During the past year, two distinct sets of chemokine co-receptors have been shown to be required for HIV entry in the CD4 positive cells. They are the CCR5 and CXCR4 receptors that are used by the macrophage (M)-tropic and T cell (T)-tropic strains of HIV respectively. Both the CD4 and the chemokine receptor have to be present on the cell to allow HIV entry. The dynamics of the ternary interaction between the HIV envelope and CD4 and the co-receptors is not understood. Also, not understood is whether other viral gene products may directly or indirectly modulate this interaction. Although HIV entry takes place in cells that express mutant coreceptors that have lost the ability to signal through chemokines, it is not clear whether the magnitude of early virus replication events are influenced by the chemokine signalling pathways. Our interests in the chemokine receptor biology were motivated by the findings that the Nef protein enhances viral replication particularly in the cells of macrophage lineage and that Nef protein may be physically associated with a p62 member of the PAK kinase family that are components of the alternative chemokine receptor signalling pathway. Therefore, we directed our efforts towards studying the effects of Nef on this pathway.