Mechanism of neutralization of budded Autographa californica nuclear polyhedrosis virus by a monoclonal antibody: Inhibition of entry by adsorptive endocytosis.

Autographa californica nuclear polyhedrosis virus (AcNPV) is characterized by two different phenotypes, each with a specific role in the life cycle of the virus in nature. They differ widely in infectivity both in vivo and in vitro, and are neutralized by different populations of antibodies. A monoclonal antibody designated AcV1 neutralizes one phenotype, BV, by reacting with a major envelope antigen not present on the other phenotype. BV can functionally enter cells by two different pathways and AcV1 neutralizes BV by preventing it from using its preferred pathway, adsorptive endocytosis. Further, a "nonneutralizable" fraction of BV in the presence of antibody excess enters by the alternative pathway. The difference in infectivity between the two phenotypes of AcNPV can be attributed to mechanisms of functional entry, as only BV can enter by the more efficient adsorptive endocytosis.