title: Role of the carbohydrate-binding sites of griffithsin in the prevention of DC-SIGN-mediated capture and transmission of HIV-1.
abstract: BACKGROUND
  The glycan-targeting C-type DC-SIGN lectin receptor is implicated in the transmission of the human immunodeficiency virus (HIV) by binding the virus and transferring the captured HIV-1 to CD4(+) T lymphocytes. Carbohydrate binding agents (CBAs) have been reported to block HIV-1 infection. We have now investigated the potent mannose-specific anti-HIV CBA griffithsin (GRFT) on its ability to inhibit the capture of HIV-1 to DC-SIGN, its DC-SIGN-directed transmission to CD4(+) T-lymphocytes and the role of the three carbohydrate-binding sites (CBS) of GRFT in these processes.
  
  
  RESULTS
  GRFT inhibited HIV-1(IIIB) infection of CEM and HIV-1(NL4.3) infection of C8166 CD4(+) T-lymphocytes at an EC50 of 0.059 and 0.444 nM, respectively. The single mutant CBS variants of GRFT (in which a key Asp in one of the CBS was mutated to Ala) were about ∼20 to 60-fold less potent to prevent HIV-1 infection and ∼20 to 90-fold less potent to inhibit syncytia formation in co-cultures of persistently HIV-1 infected HuT-78 and uninfected C8166 CD4(+) T-lymphocytes. GRFT prevents DC-SIGN-mediated virus capture and HIV-1 transmission to CD4(+) T-lymphocytes at an EC50 of 1.5 nM and 0.012 nM, respectively. Surface plasmon resonance (SPR) studies revealed that wild-type GRFT efficiently blocked the binding between DC-SIGN and immobilized gp120, whereas the point mutant CBS variants of GRFT were ∼10- to 15-fold less efficient. SPR-analysis also demonstrated that wild-type GRFT and its single mutant CBS variants have the capacity to expel bound gp120 from the gp120-DC-SIGN complex in a dose dependent manner, a property that was not observed for HHA, another mannose-specific potent anti-HIV-1 CBA.
  
  
  CONCLUSIONS
  GRFT is inhibitory against HIV gp120 binding to DC-SIGN, efficiently prevents DC-SIGN-mediated transfer of HIV-1 to CD4(+) T-lymphocytes and is able to expel gp120 from the gp120-DC-SIGN complex. Functionally intact CBS of GRFT are important for the optimal action of GRFT.
authors.affiliation: Rega Institute for Medical Research, KU Leuven, Leuven, Belgium.
authors.forename: Bart
authors.initials: B
authors.lastname: Hoorelbeke
authors.forename: Jie
authors.initials: J
authors.lastname: Xue
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: LiWang
authors.forename: Jan
authors.initials: J
authors.lastname: Balzarini
mesh_terms: D019380:Anti-HIV Agents / Q000737:chemistry* / Q000494:pharmacology; D001665:Binding Sites; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism / Q000821:virology; D015815:Cell Adhesion Molecules / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D015699:HIV Envelope Protein gp120 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D015658:HIV Infections / Q000517:prevention & control / Q000635:transmission; D015497:HIV-1 / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D006801:Humans; D037181:Lectins, C-Type / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D037121:Plant Lectins / Q000737:chemistry* / Q000494:pharmacology; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D053586:Virus Internalization / Q000187:drug effects; D000099215:DC-Specific ICAM-3 Grabbing Nonintegrin
chemical_list: D019380:Anti-HIV Agents; D015815:Cell Adhesion Molecules; D015699:HIV Envelope Protein gp120; D037181:Lectins, C-Type; D037121:Plant Lectins; D011956:Receptors, Cell Surface; D000099215:DC-Specific ICAM-3 Grabbing Nonintegrin; C499654:griffithsin protein, Griffithsia