Drosophila immunity

Role of the bactericidal/permeability-increasing protein in host defence

Much has been learned recently about the structure and function of 55 kDa bactericidal/permeability-increasing protein (BPI), a member of a genomically conserved lipid-interactive protein family. Analysis of BPI fragments and the crystal structure of human BPI have established that BPI consists of two functionally distinct domains: a potently antibacterial and anti-endotoxin amino-terminal domain (approximately 20 kDa) and a carboxy-terminal portion that imparts opsonic activity to BPI. A recombinant amino-terminal fragment (rBPI21) protects animals against the effects of Gram-negative bacteria and endotoxin. In man, rBPI21 is nontoxic and non-immunogenic and is in Phase II/III clinical trials with apparent therapeutic benefit.

Drosophila host defense: differential induction of antimicrobial peptide genes after infection by various classes of microorganisms

Insects respond to microbial infection by the rapid and transient expression of several genes encoding potent antimicrobial peptides. Herein we demonstrate that this antimicrobial response of Drosophila is not aspecific but can discriminate between various classes of microorganisms. We first observe that the genes encoding antibacterial and antifungal peptides are differentially expressed after injection of distinct microorganisms. More strikingly, Drosophila that are naturally infected by entomopathogenic fungi exhibit an adapted response by producing only peptides with antifungal activities. This response is mediated through the selective activation of the Toll pathway.

Eicosanoids mediate induction of immune genes in the fat body of the silkworm, Bombyx mori

The expression of cecropin and lysozyme genes is induced in response to bacterial peptidoglycan in the fat body of the silkworm, Bombyx mori. Specific inhibitors of either phospholipase A2, cyclooxygenase or lipoxygenase significantly inhibit the induction of the immune genes both in vivo and in cultured fat body as detected by means of Northern hybridization. Arachidonic acid injected into the larvae induces the expression of the cecropin and lysozyme genes. The findings support the idea that eicosanoids mediate some process leading to the expression of immune genes in the fat body following recognition of peptidoglycan as a signal for invading bacteria.