The genetic analysis of the HIV envelope binding domain on CD4

Mechanistic Effect of NMSO3 on Replication of Human Immunodeficiency Virus

NMSO3, a sulphated sialyl lipid, was evaluated for its efficacy against human immunodeficiency virus type 1 (HIV-1). The compound exhibited concentration-dependent inhibition of HIV-1 replication in primary infection cell culture systems. Substantial inhibition was observed at concentrations of NMSO3 that showed little cytotoxicity. NMSO3 also exhibited anti HIV-1 activity in chronically HIV-1 infected cultures. The production of progeny viruses was completely abolished without cytotoxicity by continuous addition of NMSO3 to chronically infected U937 cells. Furthermore, in attempting to define the inhibitory mechanism of NMSO3, we investigated its effect on several steps of the HIV-1 replication cycle. NMSO3 competes with gp120 for binding to CD4 receptors on cells and inhibits the entry of HIV-1. By epitope analysis of the human CD4 molecule, NMSO3 inhibits the binding of antibodies, which recognize the D1 domain of CD4. Moreover, semi-quantitative reverse transcribed polymerase chain reaction (RT-PCR) showed that the integrated provirus is transcriptionally inactive in NMSO3-treated cells, supporting the lack of progeny in the culture supernatant of chronically HIV-1-infected cells treated with NMSO3. These findings indicate that NMSO3 has a unique mechanism of action against HIV-1 in both primary and chronic infection, and may be a valuable compound for the treatment of HIV-1 infection.

Small-molecule CD4 mimics interact with a highly conserved pocket on HIV-1 gp120

Human immunodeficiency virus (HIV-1) interaction with the primary receptor, CD4, induces conformational changes in the viral envelope glycoproteins that allow binding to the CCR5 second receptor and virus entry into the host cell. The small molecule NBD-556 mimics CD4 by binding the gp120 exterior envelope glycoprotein, moderately inhibiting virus entry into CD4-expressing target cells and enhancing CCR5 binding and virus entry into CCR5-expressing cells lacking CD4. Studies of NBD-556 analogs and gp120 mutants suggest that (1) NBD-556 binds within the Phe 43 cavity, a highly conserved, functionally important pocket formed as gp120 assumes the CD4-bound conformation; (2) the NBD-556 phenyl ring projects into the Phe 43 cavity; (3) enhancement of CD4-independent infection by NBD-556 requires the induction of conformational changes in gp120; and (4) increased affinity of NBD-556 analogs for gp120 improves antiviral potency during infection of CD4-expressing cells.

Genetic subspecies diversity of the chimpanzee CD4 virus-receptor gene

Chimpanzees are naturally and asymptomatically infected by simian immunodeficiency virus (SIV). Pathogenic properties of SIV/HIV vary and differences in susceptibility and pathogenicity of SIV/HIV depend in part on host-specific factors such as virus-receptor/co-receptor interactions. Since CD4 plays a primary role in virus binding and since SIVcpz have been found only in two African chimpanzee subspecies, we characterized the genetic diversity of CD4 receptors in all four recognized subspecies of chimpanzees. We found noticeable variation in the first variable region V1 of CD4 and in intron six among the subspecies of chimpanzees. We found the CD4 receptor to be conserved in individuals belonging to the P. t. verus subspecies and divergent from the other three subspecies, which harbored highly variable CD4 receptors. The CD4 receptor of chimpanzees differed from that of humans. We question whether the observed diversity can explain the species-specific differences in susceptibility to and pathogenicity of SIV/HIV.