Insect immune priming: ecology and experimental evidences

Abstract

Abstract. 1. Immune priming refers to improved protection of the host after a second encounter with the same parasite or pathogen. This phenomenon is similar to that of adaptive immunity in vertebrates.2. There is evidence to suggest that this improved protection can be species/ strain-specific and can protect organisms for a lifetime. These two attributes, along with a biphasic immune response, are essential characteristics of immune priming and form the basis for the effectiveness of resistance to parasites and pathogens.3. This paper considers the effect of immune priming within and across generations, the influence of a heterologous challenge during immune priming and the importance of testing the immune response with natural pathogens.4. The analysis presented takes into account the multifaceted nature of the invertebrate immune response. The lack of evidence suggesting that the bacterial microbiome plays a complementary role in the immune priming outcome is discussed.5. Finally, the cost of immune priming is explored. This is a poorly investigated issue, which could help to explain why there is a paucity of evidence in support of immune priming.

Evolution of transgenerational immunity in invertebrates

“…In conclusion, there is a growing interest regarding the biology and ecology of transgenerational immune priming in invertebrates [64], not least owing to the key role some of them play as pollinators, vectors of diseases, and agricultural and stored product pests. Transgenerational immune priming is predicted to have not only a strong effect on disease prevalence [65,66], but also on the age structure [65] and population dynamics of invertebrates [66].…”

Methylation on RNA: A Potential Mechanism Related to Immune Priming within But Not across Generations

“…In addition, we propose that the full kinetics of methylation in RNA before and after the first and second challenge, together with the knowledge of which form of RNA is methylated, will provide more information to address the importance on immune priming. This kinetics, as well as the gene expression during immune priming, deserves further investigation because the exact mechanism of immune priming remains unknown for all invertebrate species (Tate and Graham, 2015; Contreras-Garduño et al, 2016; Milutinović and Kurtz, 2016). …”

“…Recent evidence suggests that invertebrates have properties that resemble vertebrate immune memory (Contreras-Garduño et al, 2016; Milutinović and Kurtz, 2016). The process has been termed immune priming, and it refers to enhanced protection (i.e., resistance, immune response, and survival) to a pathogen or parasite in a second encounter after a first specific exposure (Kurtz and Franz, 2003; Little and Kraaijeveld, 2004; Kurtz, 2005).…”

Sustainable farming of the mealworm Tenebrio molitor for the production of food and feed

“…Whereas immune priming increases host resistance to pathogens during second and subsequent encounters, transgenerational immune priming allows the offspring of the host to benefit from the same resistance even on their first encounter with the pathogen (Figure 3) [129][130][131][132][133]. However, individual immune priming by systemic injection would prove difficult in mass-reared insects due to their relatively small size and great number.…”

“…The application of transgenerational immune priming to reduce disease outbreaks has also been considered in the aquaculture industry [145]. The specific mechanism of (transgenerational) immune priming in insects is not fully understood [132]. One assumption is that antimicrobial peptides (AMPs) are involved in this seemingly more specific immune response in insects [146].…”