@article{mbs:/content/journal/jgv/10.1099/0022-1317-73-7-1761, author = "Ohki, Kohji and Kishi, Masahiko and Ohmura, Kazutaka and Morikawa, Yuko and Jones, Ian M. and Azuma, Ichiro and Ikuta, Kazuyoshi", 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", journal= "Journal of General Virology", year = "1992", volume = "73", number = "7", pages = "1761-1772", doi = "https://doi.org/10.1099/0022-1317-73-7-1761", url = "https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-73-7-1761", publisher = "Microbiology Society", issn = "1465-2099", type = "Journal Article", 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 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.", }