IMMUNE-RESPONSES IN TRICHOPLUSIA-NI CHALLENGED WITH BACTERIA OR BACULOVIRUSES

Last instar larvae of Trichoplusia ni respond to injections of bacteria with a set of inducible immune proteins. The induced proteins are related to the known immune proteins attacins, cecropins and lysozyme from Hyalophora cecropia. The antibacterial response was elicited most effectively by bacteria. An injection of Autographa californica nuclear polyhedrosis virus did not cause an induction any larger than that caused by an injection of Ringer's saline. No antibacterial response was observed at all when the virus was given orally. Immune hemolymph was fractionated electrophoretically and the gel probed both with a bacterial overlay and Western blotting. There were three to four antibacterial bands, some of which cross-reacted with anti-Hyalophora cecropin antibodies. In SDS-Western blots one band had the same mobility as attacin. Isoelectric focusing gels indicate multiple forms of attacin from T. ni. Lysozyme activity was also shown to be induced. A suppression of the hemolymph's ability to melanize was noted in larvae injected with baculovirus or bacteria and to a lesser extent with Ringer's solution. The virus titer in the hemolymph increased similarly, whether the immune system had been induced with bacteria or not. The viral infection also caused some breakdown of many hemolymph proteins including the antibacterial proteins. © 1990.