Two mechanisms for escape from immune surveillance by neurotropic retroviruses

The mechanism(s) by which lentiviruses and related non‐oncogenic retroviruses (e.g. HTLV‐III, the etiologic agent of AIDS) escape immune surveillance, and thereby create long term progressive disease conditions, has been unknown until recently. Studies with two lentiviruses have begun to illuminate the mechanisms. In one, antigenic drift in the virus appears to be the primary mechanism of escape from immune surveillance; in the second, selective masking of the viral envelope glycoprotein epitope, which normally elicits neutralizing anti‐body, appears to provide the means of escape.