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113 Inhibition of sCD4-Induced Conformational Changes of gp41 Ectodomain by C Peptide
L. Yi, L. Hong, and T Hattori*
Graduate Sch. of Med., Tohoku Univ., Sendai, Japan
Purpose: Anti-fusogenic activities of C peptides are well known, but their inhibitory mechanisms have not been well clarified. Upon interaction of gp120 with sCD4, gp41 changes conformation from prefusogenic to fusogenic structure. 2F5 mAb is believed to recognize a linear prefusogenic epitope of C peptide that could be cryptic in the presence of N peptide. 50.69 mAb recognizes the epitope that appears on the mixture of N and C peptides and was believed to be anti-fusogenic gp41 mAb. The effects of gp41-derived peptides (N peptides: N36 and DP107; C peptides: C34 and DP178) on the conformational changes induced by sCD4 were examined to see if their effects could be detected by flow-cytometric analysis.
Methods: Either human anti-prefusogenic gp41 mAb (2F5) or anti-
fusogenic gp41 mAb (50.69) was used with mouse anti-gp120 mAb (902) for 2-color flow-cytometric analysis of H9/IIIB cells.
Results: In the mAbs 902/50.69, soluble CD4 (sCD4) treatment decreased the 902+/50.69( and increased the 902(/50.69+ and 902(/50.69( populations. Simultaneous addition of C34 or DP178 inhibited these changes. In the case of mAbs 902/2F5,
sCD4 treatment decreased the 902+/2F5+ population and increased the 902( /2F5( population, and these changes were also blocked by C34. However, N peptides did not inhibit the sCD4-nduced changes. Higher amounts of N peptides than C peptides are required to inhibit the fusion mediated by H9/IIIB and HeLa CD4.
Conclusions: These findings strongly suggested that C34 and DP178 inhibit the conformational changes of gp41 induced by sCD4 on the cell surface.
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