title: Human immunodeficiency virus type 1 (HIV-1) superinfection of a cell clone converting it from production of defective to infectious HIV-1 is mediated predominantly by CD4 regions other than the major binding site for HIV-1 glycoproteins.
abstract: A cell clone, L-2, which produces non-infectious doughnut-shaped human immunodeficiency virus type 1 (HIV-1) particles, was permissive for HIV-1 superinfection, which resulted in the production of infectious particles. The superinfection showed slow kinetics compared with primary HIV-1 infection of M10 cells, the parent of the L-2 cell clone. Inhibition studies on the superinfection of L-2 cells using several CD4-related reagents showed that the CD4 molecule was an essential component of the receptor for superinfection. Strong inhibitory effects were obtained using CD4 peptides such as CD4(68-130), which includes a portion homologous to the immunoglobulin third complementarity-determining region (CDR3), as well as recombinant soluble CD4. In contrast, a CD4(45-60) peptide, which includes most of the CDR2-related region, was not effective, although the Leu-3a monoclonal antibody (MAb), which recognizes a site near the CDR2-related region, did slightly, but significantly, delay the superinfection kinetics. Comparative flow cytometry of L-2 and M10 cells revealed that the cell surface of L-2 cells despite expressing HIV-1 env protein, reacted slightly with OKT4 or anti-CD4(68-130) MAb, but not with Leu-3a or OKT4A MAb. In contrast, no reaction was detected with any of these anti-CD4 MAbs on the surface of another HIV-1 superinfection-resistant cell clone, MOLT-#8IIIB-14, which expresses HIV-1 env proteins but does not produce infectious HIV-1 particles. These results strongly suggest that expression of the CD4 major receptor site for primary HIV-1 infection is preferentially decreased on the surface of L-2 cells, but that the OKT4 epitope and the nearby region corresponding to immunoglobulin CDR3 remain exposed on the cell surface. Consequently, the CD4 CDR3-related region could play a major role as the receptor for the superinfection reported here.
authors.affiliation: Institute of Immunological Science, Hokkaido University, Sapporo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ohki
authors.forename: M
authors.initials: M
authors.lastname: Kishi
authors.forename: K
authors.initials: K
authors.lastname: Ohmura
authors.forename: Y
authors.initials: Y
authors.lastname: Morikawa
authors.forename: I M
authors.initials: IM
authors.lastname: Jones
authors.forename: I
authors.initials: I
authors.lastname: Azuma
authors.forename: K
authors.initials: K
authors.lastname: Ikuta
mesh_terms: D001665:Binding Sites; D015704:CD4 Antigens / Q000235:genetics / Q000502:physiology*; D002999:Clone Cells; D003673:Defective Viruses / Q000254:growth & development*; D006023:Glycoproteins / Q000378:metabolism*; D015497:HIV-1 / Q000254:growth & development*; D006801:Humans; D007135:Immunoglobulin Variable Region; D012333:RNA, Messenger / Q000032:analysis; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: D015704:CD4 Antigens; D006023:Glycoproteins; D007135:Immunoglobulin Variable Region; D012333:RNA, Messenger; D014764:Viral Proteins