Effect of tunicamycin on the structural proteins and infectivity of budded Autographa californica nuclear polyhedrosis virus.

The budded phenotype of Autograha californica nuclear polyhedrosis virus (AcNPV BV) has a 64K glycoprotein in its envelope which is important in the ability of the virus to functionally enter host cells. Tunicamycin (TM), an inhibitor of N-linked glycosylation, was used to determine whether the sugar moiety was essential for the normal function of the 64K protein. At 10 mug/ml TM, glycosylation was completely inhibited. Infectivity of AcNPV BV was reduced to 2% of control while extracellular particles formed were 28% of control. Particles produced in the presence of 10 mug/ml TM were neutralizable by a monoclonal antibody reactive with the 64K envelope protein and their infectivity was sensitive to chloroquine. These results indicated that the major envelope protein, though unglycosylated, was still able to function normally in viral entry. Particles grown in the presence of 10 mug/ml TM however, contained on average, only 30% of the normal concentration of this major envelope protein. The combination of reduced number of extracellular particles and reduced amount of major envelope protein on these particles could account for the observed reduction in infectivity.