How insects fight infections: Kill as much as you can first, AMPs take care of the rest

Posted by: Kasra Hassani

Recently antimicrobial peptides (AMPs) have received a lot of attention due to their ubiquitous presence in defence systems along with diversity of structure and function and of course putative commercial and therapeutics usages. Organisms as diverse as bacteria, fungi, insects and vertebrates possess a ‘personalized’ set of AMPs that fight invaders with low or no effect on hosts; interestingly, AMPs seems to be highly tolerant to emergence of resistance.

A study in Science by Haine et al. has suggested that insects use a two step mechanism in fighting infections. Firstly, up to 99.5% of the bacteria are killed by the phagocytic haematocytes and other immune mechanisms of the insects within the first few hours. Secondly and interestingly, the remaining low percentage which have been selected due resistance to the first immune response are ‘mopped up’ by a load of AMPs secreted from the host for the following days (up to two weeks). Because different AMPs with different properties and functions (pore forming, modulatory, inhibitory…) are secreted at the same time, very low chances for emergence of resistance remains for the surviving bacteria. The authors have highlighted that when thinking of AMPs for therapeutic purposes, their exact ecological role in nature has to be kept in mind.

Picture from Schneider and Chambers, Science 2008

Picture from Schneider and Chambers, Science 2008