Early events in the infection of Heliothis zea midgut cells by a baculovirus

Abstract

Virus adsorption, penetration and uncoating were observed in midgut cells of laboratoryreared larvae of Heliothis zea (cotton bollworm) fed per os with the H. zea nuclear polyhedrosis virus. Within 2 hr post-inoculation (p.i.), enveloped virions interacted with microvilli of columnar cells resulting in the apparent fusion of the viral envelope and microvillus membrane. The viral envelope was lost during the entry process inasmuch as only nonenveloped nucleocapsids were observed within microvilli. After entry into the cell cytoplasm, the intact nucleocapsids appeared to gain access into the nucleoplasm by interacting end-on with nuclear pores. Within 2 to 4 hr post-inoculation, numerous nucleocapsids could be seen in the nucleoplasm, a number of which appeared to be empty or partially empty. These findings show that uncoating of this virus took place within the nucleus and not at the site of the nuclear pores as suggested for some baculoviruses.