ABSTRACT
The identification of chemokine receptors as HIV-1 coreceptors has focused research on developing strategies to prevent HIV-1 infection. We generated CCR2-01, a CCR2 receptor-specific monoclonal antibody that neither competes with the chemokine CCL2 for binding nor triggers signaling, but nonetheless blocks replication of monotropic (R5) and T-tropic (X4) HIV-1 strains. This effect is explained by the ability of CCR2-01 to induce oligomerization of CCR2 with the CCR5 or CXCR4 viral coreceptors. HIV-1 infection through CCR5 and CXCR4 receptors can thus be prevented in the absence of steric hindrance or receptor downregulation by acting in trans on a receptor that is rarely used by the virus to infect cells.
Subject(s)
HIV Infections/prevention & control , HIV-1/immunology , HIV-1/metabolism , Receptors, CCR5/metabolism , Receptors, CXCR4/metabolism , Receptors, Chemokine/metabolism , Amino Acid Substitution , Antibodies, Monoclonal/biosynthesis , Antibodies, Monoclonal/metabolism , Blotting, Western , Calcium/metabolism , Cell Line , Chemokine CCL2/pharmacology , Chemokines, CC/metabolism , Chemotaxis , Culture Media, Serum-Free , Dimerization , Down-Regulation , Electrophoresis, Polyacrylamide Gel , Flow Cytometry , Genes, Reporter , HIV Infections/metabolism , Humans , Isoleucine/metabolism , Kinetics , Ligands , Monocytes/drug effects , Monocytes/metabolism , Precipitin Tests , Receptors, CCR5/genetics , Receptors, CCR5/immunology , Receptors, CXCR4/genetics , Receptors, CXCR4/immunology , Receptors, Chemokine/genetics , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
Hematopoietic cell growth, differentiation, and chemotactic responses require coordinated action between cytokines and chemokines. Cytokines promote receptor oligomerization, followed by Janus kinase (JAK) kinase activation, signal transducers and transactivators of transcription (STAT) nuclear translocation, and transcription of cytokine-responsive genes. These include genes that encode a family of negative regulators of cytokine signaling, the suppressors of cytokine signaling (SOCS) proteins. After binding their specific receptors, chemokines trigger receptor dimerization and activate the JAK/STAT pathway. We show that SOCS3 overexpression or up-regulation, stimulated by a cytokine such as growth hormone, impairs the response to CXCL12, measured by Ca(2+) flux and chemotaxis in vitro and in vivo. This effect is mediated by SOCS3 binding to the CXC chemokine receptor 4 receptor, blocking JAK/STAT and Galpha(i) pathways, without interfering with cell surface chemokine receptor expression. The data provide clear evidence for signaling cross-talk between cytokine and chemokine responses in building a functional immune system.
