Proteins specified by Herpesvirus saimiri: purification and properties of a single polypeptide which elicits virus-neutralizing antibody.

A virus-specified polypeptide of 160,000 mol. wt. (160K) was purified more than 1000-fold from the soluble proteins present in the culture medium of cells productively infected with herpesvirus saimiri (HVS). Purified preparations of the 160K polypeptide gave rise to high titre precipitating and neutralizing antibodies in immunized rabbits, which cross-neutralized independent isolates of HVS (neutralization rate constants, k, of between 3.8 and 4.8) and specifically precipitated the 160K polypeptide from extracts of cells infected with the homologous or heterologous strains of this virus. Antiserum to the 160K polypeptide of HVS also gave low (k = 0.02) levels of neutralization of the related herpesvirus ateles. Purified preparations of the 160K polypeptide were capable of removing most or all of the neutralizing antibody sera of squirrel monkeys with naturally acquired antibodies to HVS. The 160K polypeptide was previously shown to form part of the surface of enveloped virus particles. However, we show here that the 160K polypeptide is not extensively glycosylated in infected cells. The majority of glucosamine incorporation specific to HVS-infected cells was into eight regions with apparent mol. wt. of 170K to 220K, 125K to 145K, 115K to 120K, 83K to 88K, 65K to 75K, 52K to 58K, 25K to 27K and 12.5K to 13K. It remains possible that alternative cleaved or glycosylated forms of the 160K polypeptide are also present on the virus particle or that precipitating antibody to 160K and virus-neutralizing antibodies are not identical. However, our inability to detect precipitating antibody to virus-induced proteins or glycoproteins other than the 160K polypeptide and the high titre of neutralizing antibody present in this serum, provides reasonable evidence that it is the antibodies which react with the 160K polypeptide that are responsible for virus neutralization.