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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.

Scorpine is an antimicrobial peptide whose structure resembles a hybrid between a defensin and a cecropin. It exhibits antibacterial activity and inhibits the sporogonic development of parasites responsible for murine malaria. In this communication we report the production of scorpine in a heterelogous system, using a specific vector containing its cloned gene. The recombinantly expressed scorpine (RScp) in (Anopheles gambie) cells showed antibacterial activity against (Bacillus subtilis) and (Klebsiella pneumoniae), at 5 and 10 microM, respectively. It also produced 98% mortality in sexual stages of (Plasmodium berghei) at 15 microM and 100% reduction in (Plasmodium falciparum) parasitemia at 5 microM. RScp also inhibited virus dengue-2 replication in C6/36 mosquito cells. In addition, we generated viable and fertile transgenic (Drosophila) that overexpresses and correctly secretes RScp into the insect hemolymph, suggesting that the generation of transgenic mosquitoes resistant to different pathogens may be viable.

Summary 1.The role of the juvenile hormone (JH) as a potential mediator in the trade-off between malemale competition and immune response has not been tested, but its study could reveal a potential mechanism that mediates resource allocation between these two traits. 2. Controlling for body size, we tested whether males of the territorial damselfly Calopteryx virgo administrated with methoprene acid, an analog of the JH (JHa), compared to control males, increased their aggression and occupation time on territories but decreased their phenoloxidase (PO) activity (a key enzyme used during immune response after a bacterial challenge). We found an increase in aggression in JHa treated males compared to control males, but the opposite was found for PO activity. 3. As fat load and muscle mass are also important traits during a contest, we tested whether JHa males compared to control males showed more fat and muscle content 2 h after JHa administration. Our results did not show a significant difference between both male groups, suggesting that JHa only increased aggression. 4. These results and a review of other published articles, which have documented an effect of JH on a variety of functions in insects, suggest that JH may be a target of sexual selection: this hormone not only promotes the expression of secondary sexual characters but also seems condition-dependent and so its titers may indicate male condition.

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