Differential proteome profiling of bacterial culture supernatants reveals candidates for the induction of oral immune priming in the red flour beetle.

Most organisms are host to symbionts and pathogens, which led to the evolution of immune strategies to prevent harm. Whilst the immune defences of vertebrates are classically divided into innate and adaptive, insects lack specialized cells involved in adaptive immunity, but have been shown to exhibit immune priming: the enhanced survival upon infection after a first exposure to the same pathogen or pathogen-derived components. An important piece of the puzzle are the pathogen-associated molecules that induce these immune priming responses. Here, we make use of the model system consisting of the red flour beetle (Tribolium castaneum) and its bacterial pathogen Bacillus thuringiensis, to compare the proteomes of culture supernatants of two closely related B. thuringiensis strains that either induce priming via the oral route, or not. Among the proteins that might be immunostimulatory to T. castaneum, we identify the Cry3Aa toxin, an important plasmid-encoded virulence factor of B. thuringiensis. In further priming-infection assays we test the relevance of Cry-carrying plasmids for immune priming. Our findings provide valuable insights for future studies to perform experiments on the mechanisms and evolution of immune priming.

Comparative Mortality and Adaptation of a Smurf Assay in two Species of Tenebrionid Beetles Exposed to Bacillus thuringiensis.

Bacillus thuringiensis is a spore-forming bacterium which infects insect larvae naturally via the oral route. Its virulence factors interact with the epithelium of the digestive tract of insect larvae, disrupting its function and eventually leading to the death of susceptible hosts. The most cited B. thuringiensis killing mechanism is the extensive damage caused to the insect midgut, leading to its leakage. The mortality caused by B. thuringiensis has been shown to vary between serovars and isolates, as well as between host life stages. Moreover, whether susceptibility to B. thuringiensis-induced gut leakage is generalized to all host species and whether there is individual variation within species is unclear. In this study, we adapted a non-invasive "Smurf" assay from Drosophila melanogaster to two species of tenebrionid beetles: The mealworm beetle Tenebrio molitor and the red flour beetle Tribolium castaneum, during exposure to B. thuringiensis. We highlight a differential mortality between two age/size classes of T. molitor larvae, as well as different killing dynamics between B. thuringiensis var. tenebrionis and var. tolworthi in T. castaneum. The Smurf assay did not reveal a high occurrence of extensive gut disintegration in both host species upon ingestion during B. thuringiensis exposure.

Treatment of Plasmodium chabaudi Parasites with Curcumin in Combination with Antimalarial Drugs: Drug Interactions and Implications on the Ubiquitin/Proteasome System.

Antimalarial drug resistance remains a major obstacle in malaria control. Evidence from Southeast Asia shows that resistance to artemisinin combination therapy (ACT) is inevitable. Ethnopharmacological studies have confirmed the efficacy of curcumin against Plasmodium spp. Drug interaction assays between curcumin/piperine/chloroquine and curcumin/piperine/artemisinin combinations and the potential of drug treatment to interfere with the ubiquitin proteasome system (UPS) were analyzed. In vivo efficacy of curcumin was studied in BALB/c mice infected with Plasmodium chabaudi clones resistant to chloroquine and artemisinin, and drug interactions were analyzed by isobolograms. Subtherapeutic doses of curcumin, chloroquine, and artemisinin were administered to mice, and mRNA was collected following treatment for RT-PCR analysis of genes encoding deubiquitylating enzymes (DUBs). Curcumin was found be nontoxic in BALB/c mice. The combination of curcumin/chloroquine/piperine reduced parasitemia to 37% seven days after treatment versus the control group's 65%, and an additive interaction was revealed. Curcumin/piperine/artemisinin combination did not show a favorable drug interaction in this murine model of malaria. Treatment of mice with subtherapeutic doses of the drugs resulted in a transient increase in genes encoding DUBs indicating UPS interference. If curcumin is to join the arsenal of available antimalarial drugs, future studies exploring suitable drug partners would be of interest.