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

Type D simian retroviruses (SRV) cause an acquired immunodeficiency syndrome (AIDS) in monkeys. Results of infection with SRV range from complete recovery with absence of viremia to a viremic state, which produces AIDS-like symptoms and culminates in death. These varied outcomes render the interaction of the host and SRV an attractive model for the study of immunosuppressive retrovirus resulting in different pathologic consequences. We describe here the isolation and determination of the molecular weight of the receptor for SRV. We demonstrate that a cell receptor with the same molecular weight is bound by the envelope protein of all five serotypes of SRV. We also show 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 amino acids 93-106, interacts with a cell receptor of identical molecular weight. Furthermore, polyclonal and monoclonal antibodies that are directed to envelope epitopes 142-167 of SRV-1 or to 93-106 of SRV-2, specifically neutralize only the respective viral serotype. Our results indicate that the neutralization of SRV infectivity by antibodies is achieved through blocking the interaction between the virus and its cell receptor.