Higher Western blot immunoreactivity of glycoprotein 120 from R5 HIV type 1 isolates compared with X4 and X4R5 isolates

The envelope glycoprotein of human immunodeficiency virus 1 (HIV-1) plays i mportant roles in viral life cycle and pathogenesis. Understanding the immu ne responses the protein elicits during the course of a viral infection in patients is important in designing an effective vaccine candidate against t he virus or for better diagnosis of the disease. In this study, we report t hat gp120 of R5 isolates have higher Western blot (WB) immunoreactivity to antibodies elicited against the protein in virus-infected human patients co mpared with that of X4 and X4R5 isolates. Analyses of WE immunoreactivity o f chimeric gp120s constructed between R5 (AD8) and X4R5 (DH12) HIV-1 isolat es indicate that there are complex tertiary interdomain interactions even a fter a complete denaturation of the protein. Our data suggest that the dete rminant(s) responsible for the high WE immunoreactivity might be present in all gp120s, but are accessible to antibodies only for R5 gp120s in the WE assay. The V1/V2 and/or V3 regions of X4 and X4R5 gp120s likely interfere w ith either the formation or surface exposure of the WE immunoreactive deter minant, Supplementing HIV-1 WE diagnosis kits with purified R5 gp120 could improve their sensitivity and facilitate earlier diagnosis of virus infecti on.