Probing the conformation of the human T-lymphotropic virus I envelope protein complex with monoclonal antibodies.

We are investigating the binding of a series of monoclonal antibodies to native and detergent-treated human T-lymphotropic virus I (HTLV-I) envelope proteins to explore their conformation. A comparison of our data with previously published findings suggests that a central neutralization domain (aa 175-200) is folded such that only short stretches are exposed at the surface of the native envelope protein complex. However, the complete domain becomes accessible after treatment with mild non-ionic detergents, suggesting that envelope subunit interaction may partially obscure this domain. We further provide immunochemical evidence that a region containing a heptad repeat in the extracellular part of the transmembrane protein is folded towards the interior of the HTLV-I envelope complex.