title: The prolonged culture of human immunodeficiency virus type 1 in primary lymphocytes increases its sensitivity to neutralization by soluble CD4.
abstract: Primary strains of human immunodeficiency virus type 1 (HIV-1) are known to adapt to replication in cell lines in vitro by becoming sensitive to soluble CD4 (sCD4) and neutralizing antibodies (NAb). T-cell lines favor isolation of variants that use CXCR4 as a co-receptor, while primary isolates predominantly use CCR5. We have now studied how a primary R5 isolate, CC1/85, adapts to prolonged replication in primary human peripheral blood mononuclear cells (PBMC). After 19 passages, a variant virus, CCcon.19, had increased sensitivity to both sCD4 and NAb b12 that binds to a CD4-binding site (CD4BS)-associated epitope, but decreased sensitivity to anti-CD4 antibodies. CCcon.19 retains the R5 phenotype, its resistance to other NAbs was unaltered, its sensitivity to various entry inhibitors was unchanged, and its ability to replicate in macrophages was modestly increased. We define CCcon.19 as a primary T-cell adapted (PTCA) variant. Genetic sequence analysis combined with mutagenesis studies on clonal, chimeric viruses derived from CC1/85 and the PTCA variant showed that the most important changes were in the V1/V2 loop structure, one of them involving the loss of an N-linked glycosylation site. Monomeric gp120 proteins expressed from CC1/85 and the PTCA variant did not differ in their affinities for sCD4, suggesting that the structural consequences of the sequence changes were manifested at the level of the native, trimeric Env complex. Overall, the adaptation process probably involves selection for variants with higher CD4 affinity and hence greater fusion efficiency, but this also involves the loss of some resistance to neutralization by agents directed at or near to the CD4BS. The loss of neutralization resistance is of no relevance under in vitro conditions, but NAbs would presumably be a counter-selection pressure against such adaptive changes in vivo, at least when the humoral immune response is intact.
authors.affiliation: Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, NY 10021, USA.
authors.forename: Pavel
authors.initials: P
authors.lastname: Pugach
authors.forename: Shawn E
authors.initials: SE
authors.lastname: Kuhmann
authors.forename: Joann
authors.initials: J
authors.lastname: Taylor
authors.forename: Andre J
authors.initials: AJ
authors.lastname: Marozsan
authors.forename: Amy
authors.initials: A
authors.lastname: Snyder
authors.forename: Thomas
authors.initials: T
authors.lastname: Ketas
authors.forename: Steven M
authors.initials: SM
authors.lastname: Wolinsky
authors.forename: Bette T
authors.initials: BT
authors.lastname: Korber
authors.forename: John P
authors.initials: JP
authors.lastname: Moore
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000276:immunology; D001665:Binding Sites; D065100:CCR5 Receptor Antagonists; D015704:CD4 Antigens / Q000737:chemistry / Q000276:immunology* / Q000494:pharmacology; D002478:Cells, Cultured; D016384:Consensus Sequence; D015699:HIV Envelope Protein gp120 / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D015497:HIV-1 / Q000187:drug effects / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000821:virology*; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D019713:Receptors, CCR5 / Q000235:genetics; D012995:Solubility; D014779:Virus Replication
chemical_list: D000911:Antibodies, Monoclonal; D065100:CCR5 Receptor Antagonists; D015704:CD4 Antigens; D015699:HIV Envelope Protein gp120; D019713:Receptors, CCR5