Regulation of Antibacterial Protein Synthesis Following Infection and During Metamorphosis of Manduca sexta^a

Abstract

Larvae of the tobacco hornworm, Manduca sexta, respond to intrahemocoelic injection of bacteria or bacterial cell wall peptidoglycan with induced synthesis of a suite of antibacterial proteins. Previous studies have demonstrated peptidoglycan regulation of the synthesis of these antibacterial proteins. In addition to eliciting enhanced synthesis of antibacterial proteins, peptidoglycan fragments also elicit a "malaise syndrome" characterized by decreased feeding and growth, delayed metamorphosis, and altered excretion. We speculate that these symptoms may be components of a mechanism to flush out and sterilize the midgut lumen, one of the primary sources of bacterial infection in insects. Studies of naive larvae have demonstrated the accumulation of lysozyme in the differentiating pupal midgut epithelium and release of lysozyme into the pupal midgut lumen after the larval midgut epithelium has been sloughed off. These observations have been extended by the identification of potent bactericidal activity against E. coli and immunoreactive hemolin, together with lysozyme, in the lumen of the newly differentiated pupal midgut.

Parasitic suppression of feeding in the tobacco hornworm,Manduca sexta: Parallels with feeding depression after an immune challenge

“…Both an immune challenge (Dunn et al, 1994; Fig. 1) and the wasp larvae (Adamo et al, 1997) depressed feeding.…”

Prior infection of Manduca sexta with non-pathogenic Escherichia coli elicits immunity to pathogenic Photorhabdus luminescens: Roles of immune-related proteins shown by RNA interference

“…There was no sign in our experiments of any decline in immunity during the 48 h period of the experiment. We considered it inappropriate to extend the duration of the experiment beyond this time, because at later times the control insects would be preparing to pupate, when new immune defences begin to appear according to a developmental programme (Dunn et al, 1994). In previous work with Galleria mellonella larvae (Stephens, 1959(Stephens, , 1962 immunity induced by injection of killed P. aeruginosa cells was found to decline after about 24 h. The possibility that the progressive loss of immunity with time seen in Stephens' experiment was due to the onset of pupation cannot be excluded.…”

Molecular approaches to mosquito parasite interactions

“…As shown above, midgut cells can mount an active lytic defense against malaria parasites . Midgut cells have also been shown to produce lysozyme (Dunn et al, 1994) as well as phenoloxidase . Flight muscle cells and Malpighian tubules can also mount an encapsulation response to microfilariae infection (see below).…”