Immunogenicity of the extracellular domains of C-C chemokine receptor 5 and the in vitro effects on simian immunodeficiency virus or HIV infectivity

The C-C chemokine receptor CCR5 serves an important function in chemotaxis of lymphocytes, monocytes, and dendritic cells. CCR5 is also the major core ceptor in most macrophage-tropic HIV-1 infections. Immunization of rhesus m acaques with a baculovirus-generated CCR5 construct or peptides derived fro m the sequences of the four extracellular domains of CCR5 elicited IgG and IgA Abs, inhibition of SIV replication, and CD4(+) T cell proliferative res ponses to three of the extracellular domains of CCR5. The immune sera react ed with cell surface CCR5 expressed on HEK 293 cells. T and B cell epitope mapping revealed major and minor T and B cell epitopes in the N-terminal, f irst, and second loops of CCR5. The three C-C chemokines, RANTES, macrophag e-inflammatory protein-lee, and macrophage-inflammatory protein-1 beta, wer e up-regulated by immunization with the CCR5-derived peptides, and the cell surface expression of CCR5 was decreased. The CCR5 Abs were complementary to the C-C chemokines in inhibiting HIV replication in vitro. Immunization with the four extracellular domains of CCR5 suggests that three of them are immunogenic, with maximal T cell responses being elicited by the second lo op peptide. However, maximal Abs to the cell surface CCR5 or viral inhibito ry Abs in vitro were induced by the N-terminal peptide. Up-regulation of th e three C-C chemokines and down-modulation of cell surface CCR5 were elicit ed by the second loop, N-terminal, and first loop peptides. The data sugges t that a dual mechanism of C-C chemokines and specific Abs may engage and d own-modulate the CCR5 coreceptors and prevent in vitro HIV or SIV replicati on.