Site of action of a synergistic factor of a granulosis virus of the armyworm, Pseudaletia unipuncta

Abstract

A synergistic factor (SF), which is present in the capsule matrix protein of a granulosis virus of the armyworm, Pseudaletia unipuncta, enhances baculovirus infection in armyworm larvae. The site of action of the SF was investigated. The oral inoculation of SF did not enhance the infectious hemolymph virions which had been inoculated into the hemocoel. The SF also did not enhance the infection of purified enveloped virions when both virus and SF were inoculated into the hemocoel, but enhancement occurred when they were inoculated orally. Thus, the activity of the SF was confined to the midgut lumen. Observations with ferritin-conjugated antibody indicated that the site of action of SF was the cell membrane of the microvillus. There were more ferritin particles attached to midgut cell membranes of larvae inoculated orally with SF than to those of control larvae inoculated with buffer. © 1980.