title: MiniCD4 protein resistance mutations affect binding to the HIV-1 gp120 CD4 binding site and decrease entry efficiency.
abstract: BACKGROUND
  Binding of the viral envelope protein (Env), and particularly of its gp120 subunit, to the cellular CD4 receptor is the first essential step of the HIV-1 entry process. The CD4 binding site (CD4bs) of gp120, and especially a recessed cavity occupied by the CD4 Phe43 residue, are known to be highly conserved among the different circulating subtypes and therefore constitute particularly interesting targets for vaccine and drug design. The miniCD4 proteins are a promising class of CD4bs inhibitors. Studying virus evolution under pressure of CD4bs inhibitors could provide insight on the gp120-CD4 interaction and viral entry.
  
  
  RESULTS
  The present study reports on the resistance induction of two subtype B HIV-1 against the most active miniCD4, M48U1, and its ancestor, M48, and how these mutated positions affect CD4bs recognition, entry efficiency, and sensitivity to other CD4bs inhibitors. Resistance against M48U1 was always associated with S375R/N substitution in both BaL and SF162; M48 resistance was associated with D474N substitution in SF162 and with H105Y substitution in BaL. In addition, some other mutations at position V255 and G471 were of importance for SF162 resistant viruses. Except for 474, all of these mutated positions are conserved, and introducing them into an SF162 Env expressing infectious molecular clone (pBRNL4.3 SF162) resulted in decreased entry efficiency. Furthermore, resistant mutants showed at least some cross-resistance towards other CD4bs inhibitors, the V3 monoclonal antibody 447-52D and some even against the monoclonal antibody 17b, of which the epitope overlaps the co-receptor binding site.
  
  
  CONCLUSIONS
  The mutations H105Y, V255M, S375R/N, G471R/E, and D474N are found to be involved in resistance towards M48 and M48U1. All mutated positions are part of, or in close proximity to, the CD4bs; most are highly conserved, and all have an impact on the entry efficiency, suggesting their importance for optimal virus infectivity.
authors.affiliation: Virology Unit, Department of Biomedical Sciences, Institute of Tropical Medicine of Antwerp, Antwerp, Belgium.
authors.forename: Katrijn
authors.initials: K
authors.lastname: Grupping
authors.forename: Philippe
authors.initials: P
authors.lastname: Selhorst
authors.forename: Johan
authors.initials: J
authors.lastname: Michiels
authors.forename: Katleen
authors.initials: K
authors.lastname: Vereecken
authors.forename: Leo
authors.initials: L
authors.lastname: Heyndrickx
authors.forename: Pascal
authors.initials: P
authors.lastname: Kessler
authors.forename: Guido
authors.initials: G
authors.lastname: Vanham
authors.forename: Loïc
authors.initials: L
authors.lastname: Martin
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Ariën
mesh_terms: D000911:Antibodies, Monoclonal / Q000378:metabolism; D001665:Binding Sites; D015704:CD4 Antigens / Q000378:metabolism*; D024882:Drug Resistance, Viral; D000939:Epitopes / Q000378:metabolism; D057809:HEK293 Cells; D015483:HIV Antibodies / Q000378:metabolism; D015699:HIV Envelope Protein gp120 / Q000378:metabolism*; D023581:HIV Fusion Inhibitors / Q000494:pharmacology*; D015658:HIV Infections / Q000821:virology; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics / Q000472:pathogenicity; D054884:Host-Pathogen Interactions; D006801:Humans; D008826:Microbial Sensitivity Tests; D009154:Mutation; D010455:Peptides / Q000494:pharmacology; D010649:Phenylalanine / Q000378:metabolism; D011487:Protein Conformation; D053585:Virus Attachment; D053586:Virus Internalization / Q000187:drug effects*
chemical_list: D000911:Antibodies, Monoclonal; D015704:CD4 Antigens; D000939:Epitopes; D015483:HIV Antibodies; D015699:HIV Envelope Protein gp120; D023581:HIV Fusion Inhibitors; D010455:Peptides; C514793:gp120 protein, Human immunodeficiency virus 1; D010649:Phenylalanine