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

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

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

  1. can you explain more how dose secretion of different AMPs help avoiding resistance?!
    it is like using different antibiotics, in long term the result would be resistance to all types of treatments. Also, do all the secreted AMPs attack the bacteria effectively? because if we assume only one or a few of AMPs are able to knock that specific type of bacteria then that explanation does not justify the results. tnx;)

    p.s: i think the more important reason for not evolving resistance is that a large share of the bacterial population is engulfed at the first step. Because of this, number of bacterias that experience effect of AMPs is not large enough to effect gene pool of that population.

    • Some AMPs (especially in vertebrates) work by means that are very unlikely to promote resistance, such as modifying the immune response of the host, instead of acting directly on the pathogen. During infection, a large variety of AMPs are secreted against the pathogen, which act in very different ways (such as membrane permeabilization, or binding internal targets and inhibiting different vital cellular actions). Therefore, even if the bacteria are resistant to one or two AMPS, they will be killed by the others and the chances of mutations arising for resistance to all of them at the same time are very little; plus, bear in mind that AMPs are also evolving and changing relatively rapidly through time.
      Furthermore, the study suggests that the insects are able to ‘mop up’ all of the bacteria that have survived the AMP attack, so even if there exist a few number that have been selected after the killing by AMPS, they are killed by another means and cannot propagate to spread the resistance genes.
      All together, this does not mean that resistance would not arise. It only says that the chances are much much lower.

      – Kasra

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