The cytoplasmic tail of CD4 is required for inhibition of human immunodeficiency virus type 1 replication by antibodies that bind to the immunoglobulin CDR3-like region in domain 1 of CD4

M Benkirane, H Schmid-Antomarchi, D R Littman, M Hirn, B Rossi, C Devaux
1995 Journal of Virology  
Monoclonal antibodies (MAb) directed against the immunoglobulin complementary determining region 3 (CDR3)-like region of the CD4 molecule inhibit human immunodeficiency virus type 1 (HIV-1) transcription. We report here data showing that the cytoplasmic tail of CD4 is required for such inhibition to be achieved. To this aim, we studied the effect of MAb 13B8-2 treatment on (i) HIV-1 production in A2.01 cells, which express different forms of the CD4 gene, (ii) Tat-induced HIV-1 promoter
more » ... -1 promoter activation, and (iii) mitogenactivated protein kinase (MAPK) activation, which is induced in CD4-positive cells by HIV-1 cross-linking of CD4. Inhibition of HIV production by 13B8-2 MAb treatment was consistently observed in cells expressing wild-type CD4 and cells expressing a hybrid CD4-CD8 molecule (amino acids 1 to 177 of CD4 fused to the hinge, transmembrane, and cytoplasmic domains of CD8). However, no delay in HIV-1 production was observed in cells expressing a truncated CD4 which lacks the cytoplasmic domain (CD4.401). Chloramphenicol acetyltransferase assays demonstrated that Tat-dependent activation of the HIV-1 long terminal repeat promoter was inhibited by MAb 13B8-2 in A2.01/CD4 and A2.01/CD4-CD8 but not in A2.01/CD4.401 cells. Finally, we found that MAb 13B8-2 treatment inhibited the activation of MAPK induced in A2.01/CD4 and A2.01/CD4-CD8 following cross-linking of CD4 by HIV-1. The primary high-affinity cellular receptor for human immunodeficiency virus type 1 (HIV-1) is the CD4 molecule (reviewed in reference 31). This integral membrane glycoprotein of approximately 58 kDa contains four extracellular domains showing structural homology with immunoglobulin (Ig) V regions (30, 36). The amino-terminal domain (D1) of CD4 shows a protruding ridge corresponding to the second immunoglobulin-like complementary determining region (CDR2-like region) identified as the primary binding site for the external HIV-1 envelope glycoprotein (reviewed in reference 1). Anti-CD4 monoclonal antibodies (MAb) which bind to this region interfere with the HIV-1 life cycle by inhibiting virion binding to cell surface CD4. Although the CDR3-like region in D1 of CD4 is not required for HIV entry, it plays an important role during HIV-1 replication (reviewed in reference 8). We previously demonstrated that an anti-CD4 MAb that binds to the CDR3-like region inhibited HIV transcription in cells containing an integrated provirus(es) (4). It is therefore of major importance to determine the molecular mechanism by which viral transcription is turned off following the binding of an MAb to the CDR3-like region of the CD4 molecule. The transcription of virus genes follows integration of the provirus into the host cell genome. This process is directed by the 5Ј long terminal repeat (LTR) of the provirus, which acts as a promoter for proviral transcription and contains recognition sequences for several constitutively expressed or inducible host cell transcription factors (reviewed in reference 13). As a consequence, the activation state of the host cell greatly influences viral gene transcription and virion production (32-34, 37, 38). We have demonstrated that the binding of HIV to CD4 can modulate the activation of T cells which express a native CD4 molecule by inducing NF-B translocation, which in turn stimulates HIV-1 promoter activity (6). Most recently, we have observed that HIV-1 binding to CD4 activates tyrosine phosphorylation of a number of transducing proteins, including PI-3k and mitogen-activated protein kinases (MAPK), which are possible intermediates in the activation pathway(s) that regulates the activity of the viral promoter (31a). We demonstrate here that the cytoplasmic tail of CD4 is required for 13B8-2-mediated inhibition of HIV transcription and viral production. Moreover, we show that MAb 13B8-2 treatment prevents the activation of MAPK that follows HIV-1-mediated CD4 cross-linking at the T-cell surface. These results provide the first evidence that 13B8-2-mediated inhibition of HIV transcription involves the inactivation of one or several signaling pathways that likely participate in the control of virus production. MATERIALS AND METHODS MAb and reagents. Purified anti-CD4 MAb OKT4 was purchased from Ortho Diagnostic Systems, Inc. (Raritan, N.J.). Purified anti-CD4 MAb 13B8-2 was
doi:10.1128/jvi.69.11.6904-6910.1995 fatcat:gyp2cikpxnh6vh4e24sudoyuuu