title: Functional complementation of the envelope hypervariable V3 loop of human immunodeficiency virus type 1 subtype B by the subtype E V3 loop.
abstract: The hypervariable V3 loop within gp120 of human immunodeficiency virus type 1 (HIV-1) is the major determinant of cell tropism and the entry coreceptor usage of the virus. However, the information obtained thus far has been from only subtype B from North America and Europe, and little is known about other subtypes whose V3 amino acids differ by as much as 50% from subtype B V3. In this study, we examined the functional potential of the V3 element of the HIV-1 subtype E, the most crucial variant causing the AIDS epidemic throughout southeast Asia. A panel of HIV-1LAI recombinants was constructed by the overlap extension method, by which the LAI V3 loop was precisely replaced by that of the subtype E nonsyncytium-inducing (NSI) or syncytium-inducing (SI) variant. All of the recombinant viruses infected peripheral blood mononuclear cells, whereas only those with SI V3 infected MT2 cells, a CD4(+) T cell line. Consistently, the SI V3 recombinants used CXCR4, while the NSI V3 recombinants used CCR5 for infection of HOS-CD4(+) cells. Finally, only the NSI V3 sequence conferred CC-chemokine sensitivity on the parental virus. The data support the notion that the HIV-1 V3 loop consists of a relatively independent domain in gp120 and suggest that the subtype E V3 loop indeed contains the functional element to dictate the cell tropism, coreceptor preference, and chemokine sensitivity of the virus. These findings are of immediate importance in understanding V3 structure-function relationship and for examining phenotypic evolution of HIV-1 subtype E.
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015496:CD4-Positive T-Lymphocytes; D002460:Cell Line; D002461:Cell Line, Transformed; D004279:DNA, Viral; D015699:HIV Envelope Protein gp120 / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000166:cytology; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D019713:Receptors, CCR5 / Q000378:metabolism; D019718:Receptors, CXCR4 / Q000378:metabolism