Microbial infection routes and immune priming in an insect: effects of development stage and sex

Started in october 2021

Funding: doctoral grant

Supervisor: Yannick Moret ; cosupervisor: Thierry Rigaud

Defended the 18 march 2025

Abstract

Immune priming is a phenomenon observed in many invertebrates which refers to a sustained increase in an individual’s immunocompetence following an initial non-lethal contact with a pathogen, thereby increasing its chances of surviving a second infection. As this phenomenon can be pathogen-specific, immune priming should be particularly advantageous for individuals at high risk of reinfection by the same pathogens. This risk could depend in particular on the effectiveness of the individual’s immune system, which varies according to their stage of development and sex. However, this aspect of immune priming remains little studied. In this context, the infection route could play a key role in the evolution of immune priming, given that a septic infection does not necessarily involve the same host-pathogen interactions as an oral infection.

The aim of this thesis was to study the modalities and consequences of immune priming in the mealworm beetle, Tenebrio molitor (Coleoptera, Tenebrionidae), in particular by testing the possibility of oral infection, which has been little studied in this species. Our experiments revealed that the environment of T. molitor was not very conducive to the persistence of entomopathogenic bacteria, but that individuals killed by infection could constitute infectious reservoirs favouring the spread of these pathogens. The immune priming itself only proved beneficial in the case of a first septic infection in adults, which may be explained by the high prevalence of body injuries in this stage. However, an oral infection can also protect adults from a second septic infection over a very short period of time. Furthermore, even in the absence of priming, larvae appear to be able to limit the deleterious effects of a septic or oral infection via several behavioural and physiological mechanisms. These results provide new insights into the evolution of immune priming, and more generally, host-pathogen interactions in T. molitor.

Key words

Tenebrio molitor, evolutionary ecology, immune priming, oral infection, septic infection, bacterial persistence

thesis advisory panel

Romain Pigeault, EBI, UMR 7267, université de Poitiers
Lionel Ranjard, UMR Agroécologie, INRAE Dijon

Jury

Aurélie Tasiemski, université de Lille – reviewer
Joël Meunier, université de Tours – reviewer
Romain Pigeault, université de Poitiers – examiner
Gabriele Sorci, Université Bourgogne Europe – examiner
Yannick Moret, Université Bourgogne Europe – supervisor
Thierry Rigaud, Université Bourgogne Europe – cosupervisor

extrait:

lien_externe:

titre:

Persistance microbienne et évolution du transfert maternel d’immunité chez un insecte

date_de_debut_these:

octobre 2021

nom:

Goerlinger

date_de_debut_these_numerique:

202110

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kc_raw_content:

Microbial infection routes and immune priming in an insect: effects of development stage and sex

Started in october 2021

Funding: doctoral grant

Supervisor: Yannick Moret ; cosupervisor: Thierry Rigaud

Defended the 18 march 2025

 

Abstract

Immune priming is a phenomenon observed in many invertebrates which refers to a sustained increase in an individual's immunocompetence following an initial non-lethal contact with a pathogen, thereby increasing its chances of surviving a second infection. As this phenomenon can be pathogen-specific, immune priming should be particularly advantageous for individuals at high risk of reinfection by the same pathogens. This risk could depend in particular on the effectiveness of the individual's immune system, which varies according to their stage of development and sex. However, this aspect of immune priming remains little studied. In this context, the infection route could play a key role in the evolution of immune priming, given that a septic infection does not necessarily involve the same host-pathogen interactions as an oral infection.

The aim of this thesis was to study the modalities and consequences of immune priming in the mealworm beetle, Tenebrio molitor (Coleoptera, Tenebrionidae), in particular by testing the possibility of oral infection, which has been little studied in this species. Our experiments revealed that the environment of T. molitor was not very conducive to the persistence of entomopathogenic bacteria, but that individuals killed by infection could constitute infectious reservoirs favouring the spread of these pathogens. The immune priming itself only proved beneficial in the case of a first septic infection in adults, which may be explained by the high prevalence of body injuries in this stage. However, an oral infection can also protect adults from a second septic infection over a very short period of time. Furthermore, even in the absence of priming, larvae appear to be able to limit the deleterious effects of a septic or oral infection via several behavioural and physiological mechanisms. These results provide new insights into the evolution of immune priming, and more generally, host-pathogen interactions in T. molitor.

 

Key words

Tenebrio molitor, evolutionary ecology, immune priming, oral infection, septic infection, bacterial persistence

 

thesis advisory panel

Romain Pigeault, EBI, UMR 7267, université de Poitiers
Lionel Ranjard, UMR Agroécologie, INRAE Dijon

 

Jury

Aurélie Tasiemski, université de Lille – reviewer
Joël Meunier, université de Tours – reviewer
Romain Pigeault, université de Poitiers – examiner
Gabriele Sorci, Université Bourgogne Europe – examiner
Yannick Moret, Université Bourgogne Europe – supervisor
Thierry Rigaud, Université Bourgogne Europe – cosupervisor