Neutralization of mouse xenotropic virus by lipoproteins involves binding to the virions.

We examined the properties of the mouse serum lipoprotein responsible for specific neutralization of the endogenous mouse xenotropic (X-tropic) type C retrovirus. The anti-X-tropic virus activity of the mouse lipoprotein neutralizing factor (NF) could not be blocked by sugars or lectins. Moreover, neutralization did not involve rupture of the virion core. Sucrose density gradient analysis of X-tropic virus mixed with various lipoprotein preparations demonstrated that the binding of complete virions to NF is associated with the neutralization.