A highly defective HIV-1 strain isolated from a healthy Gabonese individual presenting an atypical western blot.
In central equatorial Africa the frequency of uninterpretable or atypical Western blots (WB)--ie. antibodies to gag proteins only--can represent up to 50% of enzyme-linked immunosorbent assay (ELISA)-positive samples. To date the significance of such serology remains unknown. Nevertheless, an unusual HIV-1 strain has been isolated from the blood of a healthy Gabonese individual who presented an atypical WB. This virus, identified as isolated HIV-1OYl, grew to low titres of reverse transcriptase activity (less than 50,000 cpm/ml) and was not obviously cytopathic. Radioimmunoprecipitation and peptide ELISA studies indicated that the lack of env-specific reactivity was probably due to the absence of antibodies to the viral glycoproteins, rather than the virus encoding a highly divergent envelope protein. Molecular cloning and sequencing of the provirus proved it to be a string of HIV-1 which was genetically closer to European and North American than to African strains. Furthermore the envelope protein sequence contained all the features of a typical HIV-1 env gene. However, the tat gene derived from the proviral clone was functionally defective. Site-directed mutagenesis of this gene showed that this was due to the substitution of an essential cysteine residue for a serine. Polymerase chain reaction amplification of the tat gene, as well as parts of the gag and env gene sequences of HIV-1OYl, showed that essentially all of the proviruses were defective. These data emphasize the need to view HIV isolates as populations of distinct genomes capable of complementing each other.
Huet
T
T
Laboratoire de Biologie et Immunologie Moléculaires des Rétrovirus, Institut Pasteur, Paris, France.
Dazza
M C
MC
Brun-Vézinet
F
F
Roelants
G E
GE
Wain-Hobson
S
S
D000163:Acquired Immunodeficiency Syndrome / Q000175:diagnosis / Q000382:microbiology*; D000595:Amino Acid Sequence; D001483:Base Sequence; D015153:Blotting, Western; D005681:Gabon; D015686:Gene Products, env / Q000235:genetics; D015683:Gene Products, gag / Q000235:genetics; D015696:Gene Products, tat / Q000235:genetics; D005814:Genes, Viral; D015752:Genes, env; D015750:Genes, gag; D015756:Genes, tat; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011533:Proviruses / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D015533:Transcriptional Activation; D054322:tat Gene Products, Human Immunodeficiency Virus
D015686:Gene Products, env; D015683:Gene Products, gag; D015696:Gene Products, tat; D054322:tat Gene Products, Human Immunodeficiency Virus