BACULOVIRUS-MEDIATED TRANS-EPITHELIAL TRANSPORT OF PROTEINS IN INFECTED CATERPILLARS

Baculovirus-mediated abnormal protein trafficking was studied in infec ted caterpillars by using heterologous proteins. The gene for human co mplement C1r was expressed in larvae of Mamestra brassicae by a recomb inant Autographa californica nuclear polyhedrosis virus (AcMNPV) vecto r, By following the time-course of recombinant C1r distribution among various tissues, cell types and cell organelles, we concluded that the dominant site of recombinant protein synthesis was the fat body, alth ough some production in the haemocytes and midgut was also observed, O nly about 4% of the cells of the infected organs expressed recombinant C1r, which was then secreted into the haemolymph. The tracheal and in tegumental cuticle was rich in recombinant protein from the fourth day after infection although epidermal cells did not synthesize recombina nt C1r, The morphological picture suggested that the accumulation was a consequence of a trans-epithelial transport, This transport process was checked by following the fate of the 49 kDa haemolymph protein and injected ovalbumin in AcMNPV-infected Mamestra brassicae and in Lyman tria dispar nuclear polyhedrosis virus-infected Lymantria dispar larva e, Both proteins were able to pass the basal membrane of the epidermis and accumulated in the cuticle, while in control larvae neither was t ransported, The observed transepithelial transport points to the role of baculoviruses in directing recombinant, endo- and exogenous protein s to cuticulated tissues. Based on these results we conclude that the permeability of basal membranes undergoes a characteristic change duri ng the course of baculovirus infection.