Simian retrovirus receptor and neutralization mechanism by antibodies to the envelope glycoprotein

Type D simian retroviruses (SRV) cause an acquired immunodeficiency syndrom e (AIDS) in monkeys. Results of infection with SRV range from complete reco very with absence of viremia to a viremic state, which produces AIDS-like s ymptoms and culminates in death. These varied outcomes render the interacti on of the host and SRV an attractive model for the study of immunosuppressi ve retrovirus resulting in different pathologic consequences. We describe h ere the isolation and determination of the molecular weight of the receptor for SRV, We demonstrate that a cell receptor with the same molecular weigh t is bound by the envelope protein of all five serotypes of SRV, We also sh ow that the receptor recognizes a region containing amino acids 142-167 of the envelope protein of SRV serotype 1 (SRV-1), In addition, we show that a different region of SRV serotype 2 (SRV-2) envelope protein containing ami no acids 93-106, interacts with a cell receptor of identical molecular weig ht. Furthermore, polyclonal and monoclonal antibodies that are directed to envelope epitopes 142-167 of SRV-1 or to 93-106 of SRV-2, specifically neut ralize only the respective viral serotype, Our results indicate that the ne utralization of SRV infectivity by antibodies is achieved through blocking the interaction between the virus and its cell receptor.