title: Phenotypic switch in a Spanish HIV type 1 isolate on serial passage on MT-4 cells.
abstract: A biological clone (F0) of a syncytium-inducing (SI) isolate (S61) was unable to produce syncytia in MT-4 cells. On serial passage on MT-4 cells this virus [F15(-3)] became capable of inducing syncytia (Sánchez-Palomino S, et al.: J Virol 1993;67:2938). After sequencing different regions of the env gene including V1-V2, V3, and the fusion domain of both viruses, we have found only an asparagine (N)-to-isoleucine (I) change in position 7 of the V3 loop. By mutagenesis and in vitro recombination, using infectious molecular clones, we have identified this amino acid change as the only one responsible for the syncytial phenotypic switch. However, this cytopathic change was not accompanied by a change in the replication rate, indicating that these two properties are not linked genotypic traits. Thus serial passaging of an HIV-1 isolate on MT-4 cells has produced a nonsyncytial-to-syncytial switch through a point mutation in position 7 of the V3 loop.
authors.affiliation: Centro Nacional de Biología Fundamental (formerly Centro Nacional de Biología Celular y Retrovirus), Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Olivares
authors.forename: G
authors.initials: G
authors.lastname: Shaw
authors.forename: C
authors.initials: C
authors.lastname: Lopez-Galindez
mesh_terms: D000595:Amino Acid Sequence; D002460:Cell Line; D003588:Cytopathogenic Effect, Viral; D015726:Giant Cells / Q000821:virology*; D015699:HIV Envelope Protein gp120 / Q000235:genetics*; D015497:HIV-1 / Q000235:genetics / Q000502:physiology*; D008214:Lymphocytes; D008969:Molecular Sequence Data; D009154:Mutation / Q000502:physiology; D010446:Peptide Fragments / Q000235:genetics*; D010641:Phenotype; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012692:Serial Passage; D013030:Spain; D014779:Virus Replication / Q000235:genetics*
chemical_list: D015699:HIV Envelope Protein gp120; C059762:HIV envelope protein gp120 (305-321); D010446:Peptide Fragments