Drosophila immunity

Nora Virus VP4b and ORF1 Circulate in Hemolymph of Infected D. melanogaster with Coordinate Expression of Vago and Vir-1

Study of the novel RNA virus, Nora virus, which is a persistent, picorna-like virus that replicates in the gut of Drosophila melanogaster offers insight into human innate immunity and other picorna-like viruses. Nora virus infection leads to a locomotor abnormality and upregulation of two candidate target proteins, Vago and Virus-induced RNA 1 (Vir-1). These proteins are uncharacterized in response to Nora virus. We hypothesize that Nora virus is circulating in the hemolymph of Nora virus-infected D. melanogaster, allowing for migration beyond the primary site of replication in the gut. Analysis by qRT-PCR demonstrated biphasic viral load and corresponding vago and vir-1 transcription levels, suggesting transcription of vago and vir-1 occurs in response to viral infection. However, Vir-1 is also present in virus-free D. melanogaster suggesting basal expression or alternative functions. Presence of Nora virus RNA and the Viral Protein 4b (VP4b), in hemolymph of infected D. melanogaster supports the hypothesized circulation of Nora virus in the hemolymph. The study suggests that impaired locomotor function may be due to transport of Nora virus from the gut to the brain via the hemolymph.

Molecular cloning and characterization of FADD from the manila clam Ruditapes philippinarum

Fas-associated protein with death domain (FADD) is an essential element in cell death, and also implicates in cell cycle progression, inflammation and innate immunity. In the study, an FADD (designated as RpFADD) was identified and characterized from manila clam, Ruditapes philippinarum. Multiple alignments and phylogenetic analysis strongly suggested that RpFADD was a new member of the FADD family. The RpFADD transcripts were constitutively expressed in a wide range of tissues, and dominantly expressed in hemocytes. After challenged with Vibrio anguillarum or Micrococcus luteus, the expression level of RpFADD transcripts was significantly induced and reached the maximum level at 72 h and 48 h, respectively. Knockdown of RpFADD down-regulated the transcript levels of RpIKK, RpTAK1 and RpNF-κB with the exception of RpIκB. Moreover, RpFADD primarily localized in the cell cytoplasm, and its over-expression promoted the apoptosis of HeLa cells. These results revealed that RpFADD perhaps regulated the NF-κB signaling pathways positively, which provided a better understanding of RpFADD in innate immunity.

Allatostatin C modulates nociception and immunity in Drosophila

Bacterial induced inflammatory responses cause pain through direct activation of nociceptive neurons, and the ablation of these neurons leads to increased immune infiltration. In this study, we investigated nociceptive-immune interactions in Drosophila and the role these interactions play during pathogenic bacterial infection. After bacterial infection, we found robust upregulation of ligand-gated ion channels and allatostatin receptors involved in nociception, which potentially leads to hyperalgesia. We further found that Allatostatin-C Receptor 2 (AstC-R2) plays a crucial role in host survival during infection with the pathogenic bacterium Photorhabdus luminescens. Upon examination of immune signaling in AstC-R2 deficient mutants, we demonstrated that Allatostatin-C Receptor 2 specifically inhibits the Immune deficiency pathway, and knockdown of AstC-R2 leads to overproduction of antimicrobial peptides related to this pathway and decreased host survival. This study provides mechanistic insights into the importance of microbe-nociceptor interactions during bacterial challenge. We posit that Allatostatin C is an immunosuppressive substance released by nociceptors or Drosophila hemocytes that dampens IMD signaling in order to either prevent immunopathology or to reduce unnecessary metabolic cost after microbial stimulation. AstC-R2 also acts to dampen thermal nociception in the absence of infection, suggesting an intrinsic neuronal role in mediating these processes during homeostatic conditions. Further examination into the signaling mechanisms by which Allatostatin-C alters immunity and nociception in Drosophila may reveal conserved pathways which can be utilized towards therapeutically targeting inflammatory pain and chronic inflammation.

Genome-wide miRNA screening reveals miR-310 family members negatively regulate the immune response in Drosophila melanogaster via co-targeting Drosomycin

Although innate immunity mediated by Toll signaling has been extensively studied in Drosophila melanogaster, the role of miRNAs in regulating the Toll-mediated immune response remains largely unknown. In this study, following Gram-positive bacterial challenge, we identified 93 differentially expressed miRNAs via genome-wide miRNA screening. These miRNAs were regarded as immune response related (IRR). Eight miRNAs were confirmed to be involved in the Toll-mediated immune response upon Gram-positive bacterial infection through genetic screening of 41 UAS-miRNA lines covering 60 miRNAs of the 93 IRR miRNAs. Interestingly, four out of these eight miRNAs, miR-310, miR-311, miR-312 and miR-313, are clustered miRNAs and belong to the miR-310 family. These miR-310 family members were shown to target and regulate the expression of Drosomycin, an antimicrobial peptide produced by Toll signaling. Taken together, our study implies important regulatory roles of miRNAs in the Toll-mediated innate immune response of Drosophila upon Gram-positive bacterial infection.

Endogenous Pulmonary Antibiotics

The human lung produces a variety of peptides and proteins which have intrinsic antimicrobial activity. In general these molecules have broad spectra of antimicrobial activity, kill micro-organisms rapidly, and evade resistance generated by pathogens. In recent years it has become increasingly apparent that the antimicrobial peptides (AMPs) simultaneously possess immunomodulatory functions, suggesting complex roles for these molecules in regulating the clearance of, and immune response to, invading pathogens. These collective properties have stimulated considerable interest in the potential clinical application of endogenous AMPs.

This article outlines the biology of AMPs, their pattern of expression in the lung, and their functions, with reference to both antimicrobial and immunomodulatory activity. We then consider the biological importance of AMPs, before concentrating on the potential to use AMPs to therapeutic effect. The principles discussed in the article apply to innate immune defence throughout the body, but particular emphasis is placed on AMPs in the lung and the potential application to pulmonary infection.

Susceptibility and Immune Defence Mechanisms of Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) against Entomopathogenic Fungal Infections

Insects infected with entomopathogenic fungi, experience physiological changes that influence their growth and immune defence. The potential of nine isolates of entomopathogenic fungi was evaluated after determining percent germination and relative conidial hydrophobicity. However, nutritional indices were evaluated after immersing eighth-instar Rhynchophorus ferrugineus larvae into each isolate suspension (1 × 10⁷ conidia/mL). The results showed that isolates B6884 and M9374 had 44.51% and 39.02% higher conidial hydrophobicity compared with isolate I03011 (least virulent). The results of nutritional index assays revealed a significant reduction in growth indices after infection with different isolates. Compared with control, B6884 and M9374 greatly decreased larval growth by reducing the efficacy of conversion of ingested food (36%-47%) and Efficacy of conversion of digested food (50%-63%). Furthermore, only isolate B6884 induced 100% mortality within 12 days. Compared with control, isolate I03011, possessing the lowest conidial hydrophobicity, only reduced 0.29% of the efficacy of conversion of ingested food (ECI) and 0.48% of the efficacy of conversion of digested food (ECD). Similarly, transcriptomic analysis of genes related to the Red palm weevil (RPW) immune response, including pathogen recognition receptors (C-type lectin and endo-beta-1,4-glucanse), signal modulator (Serine protease-like protein), signal transductors (Calmodulin-like protein and EF-hand domain containing protein) and effectors (C-type lysozyme, Cathepsin L., Defensin-like protein, Serine carboxypeptidase, and Thaumatin-like protein), was significantly increased in larval samples infected with B6884 and M9374. These results suggest that for an isolate to be virulent, conidial hydrophobicity and germination should also be considered during pathogen selection, as these factors could significantly impact host growth and immune defence mechanisms.

LPS-induced immune response in Drosophila

The study of the regulation of the inducible synthesis of antimicrobial peptides in Drosophila melanogaster has established this insect as a powerful model in which to study innate immunity. In particular, the molecular characterization of the regulatory pathway controlling the antifungal peptide drosomycin has revealed the importance of Toll receptors in innate immunity. We report here that injection of LPS into flies induces an immune response, suggesting that LPS receptors are used in Drosophila to detect Gram-negative bacteria infection. We have identified in the recently sequenced genome of Drosophila eight genes coding for Toll-like receptors in addition to Toll, which may function as LPS receptors. However, overexpression of a selection of these genes in tissue-culture cells does not result in up-regulation of the antibacterial peptide genes. These results are discussed in light of the recent data from genetic screens aimed at identifying the genes controlling the antibacterial response in Drosophila.

Toll-dependent and Toll-independent immune responses in Drosophila

The multifaceted response of the fruitfly Drosophila melanogaster to infection by a wide range of microbes is complex and remarkably efficient. Its most prominent aspect is the immune-inducible expression of a set of potent antimicrobial peptides. Genetic analysis of the regulation of the genes encoding these peptides has led to the identification of the receptor Toll as an essential component of the fly's host defense system. In addition, these studies have revealed that the response to Gram-negative bacterial infections involves Toll-independent mechanisms, and that the sensing of infection involves two structurally distinct sets of molecules — the PGRPs and the GNBPs/βGRPs.

Fat body and hemocyte contribution to the antimicrobial peptide synthesis in Calliphora vicina R.-D. (Diptera: Calliphoridae) larvae

Antimicrobial peptides accumulated in the hemolymph in response to infection are a key element of insect innate immunity. The involvement of the fat body and hemocytes in the antimicrobial peptide synthesis is widely acknowledged, although release of the peptides present in the hemolymph from the immune cells was not directly verified so far. Here, we studied the presence of antimicrobial peptides in the culture medium of fat body cells and hemocytes isolated from the blue blowfly Calliphora vicina using complex of liquid chromatography, mass spectrometry, and antimicrobial activity assays. Both fat body and hemocytes are shown to synthesize and release to culture medium defensin, cecropin, diptericins, and proline-rich peptides. The spectra of peptide antibiotics released by the fat body and hemocytes partially overlap. Thus, the results suggest that insect fat body and blood cells are capable of releasing mature antimicrobial peptides to the hemolymph. It is notable that the data obtained demonstrate dramatic difference in the functioning of insect antimicrobial peptides and their mammalian counterparts localized into blood cells' phagosomes where they exert their antibacterial activity.

Transcriptomic insight into the immune defenses in the ghost moth, Hepialus xiaojinensis, during an Ophiocordyceps sinensis fungal infection

Hepialus xiaojinensis is an economically important species of Lepidopteran insect. The fungus Ophiocordyceps sinensis can infect its larvae, which leads to mummification after 5-12 months, providing a valuable system with which to study interactions between the insect hosts and pathogenic fungi. However, little sequence information is available for this insect. A time-course analysis of the fat body transcriptome was performed to explore the host immune response to O. sinensis infection. In total, 50,164 unigenes were obtained by assembling the reads from two high-throughput approaches: 454 pyrosequencing and Illumina Hiseq2000. Hierarchical clustering and functional examination revealed four major gene clusters. Clusters 1-3 included transcripts markedly induced by the fungal infection within 72 h. Cluster 4, with a lower number of transcripts, was suppressed during the early phase of infection but returned to normal expression levels sometime before 1 year. Based on sequence similarity to orthologs known to participate in immune defenses, 258 candidate immunity-related transcripts were identified, and their functions were hypothesized. The genes were more primitive than those in other Lepidopteran insects. In addition, lineage-specific family expansion of the clip-domain serine proteases and C-type lectins were apparent and likely caused by selection pressures. Global expression profiles of immunity-related genes indicated that H. xiaojinensis was capable of a rapid response to an O. sinensis challenge; however, the larvae developed tolerance to the fungus after prolonged infection, probably due to immune suppression. Specifically, antimicrobial peptide mRNAs could not be detected after chronic infection, because key components of the Toll pathway (MyD88, Pelle and Cactus) were downregulated. Taken together, this study provides insights into the defense system of H. xiaojinensis, and a basis for understanding the molecular aspects of the interaction between the host and the entomopathogen.

Parkin-mediated responses against infection and wound involve TSPO-VDAC complex in Drosophila

Parkin, an E3 ubuquitin ligase associated with Parkinson's disease (PD), has recently been implicated in mediating innate immunity. However, molecular details regarding parkin-mediated immune response remain to be elucidated. Here, we identified mitochondrial TSPO-VDAC complex to genetically interact with parkin in mediating responses against infection and wound in Drosophila. The loss-of-function mutation in parkin results in defective immune response against bacterial infection. Additionally, parkin mutant larvae showed hypersensitivity against wound regardless of bacterial infection. Interestingly, the combinatorial trans-heterozygotic mutations in parkin and TSPO, or parkin and VDAC showed similar lethal tendency with parkin homozygous mutants. Furthermore, knockdown of TSPO alone also resulted in defective responses to infection and wound analogously to parkin mutants. Taken together, we propose that parkin cooperates with TSPO-VDAC complex to mediate responses against infection and wound.

Immune-related transcriptome of Coptotermes formosanus Shiraki workers: the defense mechanism

Formosan subterranean termites, Coptotermes formosanus Shiraki, live socially in microbial-rich habitats. To understand the molecular mechanism by which termites combat pathogenic microbes, a full-length normalized cDNA library and four Suppression Subtractive Hybridization (SSH) libraries were constructed from termite workers infected with entomopathogenic fungi (Metarhizium anisopliae and Beauveria bassiana), Gram-positive Bacillus thuringiensis and Gram-negative Escherichia coli, and the libraries were analyzed. From the high quality normalized cDNA library, 439 immune-related sequences were identified. These sequences were categorized as pattern recognition receptors (47 sequences), signal modulators (52 sequences), signal transducers (137 sequences), effectors (39 sequences) and others (164 sequences). From the SSH libraries, 27, 17, 22 and 15 immune-related genes were identified from each SSH library treated with M. anisopliae, B. bassiana, B. thuringiensis and E. coli, respectively. When the normalized cDNA library was compared with the SSH libraries, 37 immune-related clusters were found in common; 56 clusters were identified in the SSH libraries, and 259 were identified in the normalized cDNA library. The immune-related gene expression pattern was further investigated using quantitative real time PCR (qPCR). Important immune-related genes were characterized, and their potential functions were discussed based on the integrated analysis of the results. We suggest that normalized cDNA and SSH libraries enable us to discover functional genes transcriptome. The results remarkably expand our knowledge about immune-inducible genes in C. formosanus Shiraki and enable the future development of novel control strategies for the management of Formosan subterranean termites.

A comprehensive analysis of the Manduca sexta immunotranscriptome

As a biochemical model, Manduca sexta has substantially contributed to our knowledge on insect innate immunity. The RNA-Seq approach was implemented in three studies to examine tissue immunotranscriptomes of this species. With the latest and largest focusing on highly regulated process- and tissue-specific genes, we further analyzed the same set of data using BLAST2GO to explore functional aspects of the larval fat body (F) and hemocyte (H) transcriptomes with (I) or without (C) immune challenge. Using immunity-related sequences from other insects, we found 383 homologous contigs and compared them with those discovered based on relative abundance changes. The major overlap of the two lists validated our previous research designed for gene discovery and transcript profiling in organisms lacking sequenced genomes. By concatenating the contigs, we established a repertoire of 232 immunity-related genes encoding proteins for pathogen recognition (16%), signal transduction (53%), microbe killing (13%) and others (18%). We examined their transcript levels along with attribute classifications and detected prominent differences in nine of the 30 level 2 gene ontology (GO) categories. The increase in extracellular proteins (155%) was consistent with the highly induced synthesis of defense molecules (e.g., antimicrobial peptides) in fat body after the immune challenge. We identified most members of the putative Toll, IMD, MAPK-JNK-p38 and JAK-STAT pathways and small changes in their mRNA levels. Together, these findings set the stage for on-going analysis of the M. sexta immunogenome.

Integrating nutrition and immunology: a new frontier

Nutrition is critical to immune defence and parasite resistance, which not only affects individual organisms, but also has profound ecological and evolutionary consequences. Nutrition and immunity are complex traits that interact via multiple direct and indirect pathways, including the direct effects of nutrition on host immunity but also indirect effects mediated by the host's microbiota and pathogen populations. The challenge remains, however, to capture the complexity of the network of interactions that defines nutritional immunology. The aim of this paper is to discuss the recent findings in nutritional research in the context of immunological studies. By taking examples from the entomological literature, we argue that insects provide a powerful tool for examining the network of interactions between nutrition and immunity due to their tractability, short lifespan and ethical considerations. We describe the relationships between dietary composition, immunity, disease and microbiota in insects, and highlight the importance of adopting an integrative and multi-dimensional approach to nutritional immunology.

Antagonistic regulation, yet synergistic defense: effect of bergapten and protease inhibitor on development of cowpea bruchid Callosobruchus maculatus

The furanocoumarin compound bergapten is a plant secondary metabolite that has anti-insect function. When incorporated into artificial diet, it retarded cowpea bruchid development, decreased fecundity, and caused mortality at a sufficient dose. cDNA microarray analysis indicated that cowpea bruchid altered expression of 543 midgut genes in response to dietary bergapten. Among these bergapten-regulated genes, 225 have known functions; for instance, those encoding proteins related to nutrient transport and metabolism, development, detoxification, defense and various cellular functions. Such differential gene regulation presumably facilitates the bruchids' countering the negative effect of dietary bergapten. Many genes did not have homology (E-value cutoff 10(-6)) with known genes in a BlastX search (206), or had homology only with genes of unknown function (112). Interestingly, when compared with the transcriptomic profile of cowpea bruchids treated with dietary soybean cysteine protease inhibitor N (scN), 195 out of 200 coregulated midgut genes are oppositely regulated by the two compounds. Simultaneous administration of bergapten and scN attenuated magnitude of change in selected oppositely-regulated genes, as well as led to synergistic delay in insect development. Therefore, targeting insect vulnerable sites that may compromise each other's counter-defensive response has the potential to increase the efficacy of the anti-insect molecules.

Immune response and anti-microbial peptides expression in Malpighian tubules of Drosophila melanogaster is under developmental regulation

Malpighian tubules (MT) of Drosophila melanogaster are osmoregulatory organs that maintain the ionic balance and remove toxic substances from the body. Additionally they act as autonomous immune sensing organs, which secrete antimicrobial peptides in response to invading microbial pathogens. We show that the antimicrobial peptides (AMP) diptericin, cecropinA, drosocin and attacinA are constitutively expressed and are regulated in developmental stage specific manner. Their developmental expression begins from 3^rd instar larval stage and an immune challenge increases the expression several folds. Spatial variatons in the level of expression along the MT tissue are observed. The mortality of 3^rd instar larvae fed on bacterial food is much less than that of the earlier larval stages, coinciding with the onset of innate immunity response in MT. Ectopic expression of AMP imparts better resistance to infection while, loss of function of one of the AMP through directed RNAi reduces host survival after immune challenge. The AMP secreted from the MT exhibit bactericidal activity. Expression of the NF-κB transcription factor, Relish, also coincides with activation of immune responsive genes in MT, demonstrating that immune regulation in MT is under developmental control and is governed by the Imd pathway.

Isolation, characterization and anti-cancer activity of SK84, a novel glycine-rich antimicrobial peptide from Drosophila virilis

We report herein the isolation and characterization of a novel glycine-rich antimicrobial peptide purified from the larvae of Drosophila virilis. A range of chromatographic methods was used for isolation and its antibacterial activity against Bacillus subtilis was employed to screen for the most active fractions. The peptide, termed SK84 due to its N-terminal serine, C-terminal lysine and a total of 84 residues, was completed sequenced using RT-PCR cDNA cloning. SK84 contains a high level of glycine (15.5%) and a hexaglycine cluster motif in the N-terminal part. SK84 displayed antibacterial activity against the tested Gram-positive bacteria (B. subtilis, Bacillus thuringiensis and Staphylococcus aureus), but had no effect on Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli) and fungi (Saccharomyces cerevisiae, Candida albicans). SK84 had specific inhibitory effects on the proliferation of several cancer cell lines (Human leukemia THP-1, liver cancer HepG2, and breast cancer MCF-7 cells), but no hemolytic activity. The results from scanning electron microscopy observations revealed that SK84 killed THP-1 cells by destroying the cell membranes. Alignment results show that SK84 is a mature protein processed from the pseudoprotein GJ19999 from D. virilis, and is very similar to several pseudoproteins from different Drosophila species. Our results show that SK84 represents a novel glycine-rich peptide family in Drosophila species with antimicrobial and anti-cancer cell activities.

A genomewide assessment of inbreeding depression: gene number, function, and mode of action

Although the genetic basis of inbreeding depression is still being debated, most fitness effects are thought to be the result of increased homozygosity for recessive or partially recessive deleterious alleles rather than the loss of overdominant genes. It is unknown how many loci are associated with inbreeding depression, the genes or gene pathways involved, or their mode of action. To uncover genes associated with variation in fitness following inbreeding, we generated a set of inbred lines of Drosophila melanogaster for which only the third chromosome varied among lines and measured male competitive reproductive success among these lines to estimate inbreeding depression. Male competitive reproductive success for different lines validated our prediction that equally inbred lines show variation in inbreeding depression. To begin to assess the molecular basis of inbreeding depression for male competitive reproductive success, we detected variation in whole-genome gene expression across these inbred lines with commercially available high-density oligonucleotide microarrays. A total of 567 genes were differentially expressed among these inbred lines, indicating that inbreeding directly or indirectly affects a large number of genes: genes that are disproportionately involved in metabolism, stress and defense responses. Subsequently, we generated a set of outbred lines by crossing the highest inbreeding depression lines to each other and contrasted gene expression between parental inbred lines and F(1) hybrids with transcript abundance as a quantitative phenotype to determine the mode of action of the genes associated with inbreeding depression. Although our results indicated that approximately 75% of all genes involved in inbreeding depression were additive, partially additive, or dominant, about 25% of all genes expressed patterns of overdominance. These results should be viewed with caution given that they may be confounded by issues of statistical inference or associative overdominance.

Cowpea bruchid midgut transcriptome response to a soybean cystatin--costs and benefits of counter-defence

The insect digestive system is the first line of defence protecting cells and tissues of the body from a broad spectrum of toxins and antinutritional factors in its food. To gain insight into the nature and breadth of genes involved in adaptation to dietary challenge, a collection of 20 352 cDNAs was prepared from the midgut tissue of cowpea bruchid larvae (Callosobruchus maculatus) fed on regular diet and diets containing antinutritional compounds. Transcript responses of the larvae to dietary soybean cystatin (scN) were analysed using cDNA microarrays, followed by quantitative real-time PCR (RT-PCR) confirmation with selected genes. The midgut transcript profile of insects fed a sustained sublethal scN dose over the larval life was compared with that of insects treated with an acute high dose of scN for 24 h. A total of 1756 scN-responsive cDNAs was sequenced; these clustered into 967 contigs, of which 653 were singletons. Many contigs (451) did not show homology with known genes, or had homology only with genes of unknown function in a Blast search. The identified differentially regulated sequences encoded proteins presumptively involved in metabolism, structure, development, signalling, defence and stress response. Expression patterns of some scN-responsive genes were consistent in each larval stage, whereas others exhibited developmental stage-specificity. Acute (24 h), high level exposure to dietary scN caused altered expression of a set of genes partially overlapping with the transcript profile seen under chronic lower level exposure. Protein and carbohydrate hydrolases were generally up-regulated by scN whereas structural, defence and stress-related genes were largely down-regulated. These results show that insects actively mobilize genomic resources in the alimentary tract to mitigate the impact of a digestive protease inhibitor. The enhanced or restored digestibility that may result is possibly crucial for insect survival, yet may be bought at the cost of weakened response to other stresses.

Drosomycin-like defensin, a human homologue of Drosophila melanogaster drosomycin with antifungal activity

Innate antifungal defense in Drosophila melanogaster relies on the activation of the Toll molecule and the release of drosomycin, a defensin-like molecule with antifungal properties. Ten human homologues of Toll have been described, with central roles in activation of the innate host defense. In the present study, we report a putative human homologue of the Drosophila-derived drosomycin, designated drosomycin-like defensin (DLD). Synthetic DLD displays a broad spectrum of activity against Aspergillus spp. and other clinically relevant filamentous fungi. These effects are specific for filamentous fungi; no activity has been found against yeasts or gram-positive or gram-negative bacteria. Synthetic DLD also displays immunomodulatory effects on Aspergillus-stimulated cytokine production. In addition, we show the expression of DLD mRNA in several human tissues, particularly in the skin, consistent with its putative role as a defensin against invading microorganisms. This is the first indication of an endogenous human peptide with specific antifungal activity, which is probably central in the defense against infections with molds.

Tissue expressions of nine genes important to immune defence of the Pacific white shrimp Litopenaeus vannamei

The tissue expressions of nine immune related genes in apparently healthy Pacific white shrimp Litopenaeus vannamei were analyzed by conventional RT-PCR, quantitative real time PCR (qPCR) and in situ hybridisation. The nine genes were beta-glucan binding protein-high density lipoprotein (BGBP-HDL), lipopolysaccharide-beta-glucan binding protein (LGBP), haemocyanin, prophenoloxidase (proPO), transglutaminase (TGase), crustins, penaeidins (PEN), cytosolic manganese superoxide dismutase (cMnSOD), and lysozyme. Transcripts of all nine genes were detected in all tissues with differential expression levels when examined by RT-PCR and qPCR. BGBP-HDL, LGBP and haemocyanin were mainly expressed in the hepatopancreas and their expressions levels were about 1/10-1/3 those of beta-actin. Their expressions in other tissues were relatively limited. ProPO, TGase, crustins, PEN-3, and lysozyme showed the highest levels of expression in haemocytes and the lowest in hepatopancreas. Their expression levels in the haemocytes were 3 (PEN-3) to 10(-2) (proPO) times those of beta-actin. In contrast to the other genes, cMnSOD showed higher expression levels in haemolymph related organ, stomach and muscle; and lower expression levels in haemocyte, migut, neural ganglion and hepatopancreas. When examined by in situ hybridisation, hepatopancreatic F cells were found to be the major cell type that produced transcripts of BGBP-HDL, LGBP and haemocyanin. On the other hand, circulatory haemocytes and haemocytes infiltrated in various tissues contributed to the expressions of proPO, TGase, crustins, PEN-3 and lysozyme. Both hepatopancreatic F cell and haemocyte generated cMnSOD transcripts. Using in situ hybridisation, the present study is the first to show the tissue distributions of BGBP-HDL, LGBP, haemocyanin, TGase, crustins and cMnSOD in healthy white shrimp. The present results provide a baseline data of physiological expressions for the genes that are important in immune activation and modulation in Pacific white shrimp and a guideline of tissue or organ sampling for effective gene expression analyses for future immunological studies.

Geographical distribution and diversity of bacteria associated with natural populations of Drosophila melanogaster

Drosophila melanogaster is one of the most widely used model systems in biology. However, little is known about its associated bacterial community. As a first step towards understanding these communities, we compared bacterial 16S rRNA gene sequence libraries recovered from 11 natural populations of adult D. melanogaster. Bacteria from these sequence libraries were grouped into 74 distinct taxa, spanning the phyla Proteobacteria, Bacteroidetes, and Firmicutes, which were unevenly spread across host populations. Summed across populations, the distribution of abundance of genera was closely fit by a power law. We observed differences among host population locations both in bacterial community richness and in composition. Despite this significant spatial variation, no relationship was observed between species richness and a variety of abiotic factors, such as temperature and latitude. Overall, bacterial communities associated with adult D. melanogaster hosts are diverse and differ across host populations.

Translocation of proteins homologous to human neutrophil p47phox and p67phox to the cell membrane in activated hemocytes of Galleria mellonella

Activation of the superoxide forming respiratory burst oxidase of human neutrophils, crucial in host defence, requires the cytosolic proteins p47phox and p67phox which translocate to the plasma membrane upon cell stimulation and activate flavocytochrome b558, the redox centre of this enzyme system. We have previously demonstrated the presence of proteins (67 and 47kDa) in hemocytes of the insect Galleria mellonella homologous to proteins of the superoxide-forming NADPH oxidase complex of neutrophils. The work presented here illustrates for the first time translocation of homologous hemocyte proteins, 67 and 47kDa from the cytosol to the plasma membrane upon phorbol 12-myristate 13 acetate (PMA) activation. In hemocytes, gliotoxin (GT), the fungal secondary metabolite significantly suppressed PMA-induced superoxide generation in a concentration dependent manner and reduced translocation to basel nonstimulated levels. Primarily these results correlate translocation of hemocyte 47 and 67kDa proteins with PMA induced oxidase activity. Collectively results presented here, demonstrate further cellular and functional similarities between phagocytes of insects and mammals and further justify the use of insects in place of mammals for modelling the innate immune response to microbial pathogens.

Expression pattern of Filamin-240 in Drosophila blood cells

The expression pattern of Filamin-240 was studied in subsets of Drosophila blood cells by means of immunofluorescent staining and Western blot analysis with use of an antibody specific to a "filamin-folding domain", a consensus motif profile generated from the 20 existing filamin repeats. Expression of Filamin-240 is restricted to lamellocytes - a special blood cell type of the cellular immune response - and is involved in the regulation of lamellocyte development. In the cher1 homozygous larvae, which lack Filamin-240 protein, a vigorous lamellocyte differentiation occurs which is further enhanced upon in vivo immune challenge by a parasitic wasp, Leptopilina boulardi. By introducing a full-length transgene encoding the Drosophila Filamin-240 protein into the cher1 Filamin-deficient homozygous mutant, the mutant blood cell phenotype was rescued. These data demonstrate that the expression of Filamin-240 is strictly lamellocyte specific in Drosophila blood cells and that the protein is a suppressor of lamellocyte development.

A novel association between clustered NF-kappaB and C/EBP binding sites is required for immune regulation of mosquito Defensin genes

A comparative analysis identified key cis-acting regulatory elements responsible for the temporal control of mosquito Defensin gene expression. The promoters of Anopheles gambiae Defensin 1 and two isoforms of Aedes aegypti Defensin A are up-regulated by immune challenge. This stimulated activity depends upon a cluster of three NF-kappaB binding sites and closely associated C/EBP-like motifs, which function as a unit for optimal promoter activity. Binding of NF-kappaB and C/EBP like transcription factors is confirmed by electrophoretic mobility shift assay, including supershifts with antibodies to C/EBP. KappaB-like motifs are abundant within antimicrobial peptide gene promoters and most are very closely associated with putative C/EBP binding sites. This novel association between NF-kappaB and C/EBP binding sites may, therefore, be of widespread significance.

How to kill a mocking bug?

All metazoans have evolved means to protect themselves from threats present in the environment: injuries, viruses, fungi, bacteria and other parasites. Insect protection includes innate physical barriers and both cellular and humoral responses. The insect innate immune response, best characterized in Drosophila melanogaster, is a rapid broad response, triggered by pathogen-associated molecular patterns (PAMPs) recognition, which produces a limited range of effectors that does not alter upon continued pathogen exposure and lacks immunological memory. The Drosophila response, particularly its humoral response, has been investigated by both low and high-throughput methods. Three signalling pathways conserved between insects and mammals have been implicated in this response: Toll (equivalent to mammalian TLR), Imd (equivalent to TNFalpha) and Hop (equivalent to JAK/STAT). This review provides an entry point to the insect immune system literature outlining the main themes in D. melanogaster bacterial pathogen detection and humoral and cellular immune responses. The Drosophila immune response is compared with other insects and the mammalian immune system.

Role of Toll-like receptors in infection and immunity: clinical implications

The remarkable discovery of the Toll-like receptors (TLRs) over the past 5 years has opened up an entirely new era in the understanding of the molecular events that initiate the inflammatory response. These type 1 transmembrane receptors are expressed on a large number of immune cells as well as epithelial cells and play an essential role in the activation of the innate immune response to microbial pathogens. They impact on adaptive immune reactions and contribute to the initiation and maintenance of the inflammatory response to a multitude of potential microbial pathogens through recognition of pathogen-associated molecular patterns. TLRs also interact with a variety of endogenous human ligands and influence the activity of a wide range of tissues and cell processes. Among the common and important processes in which TLRs play a role are asthma, acute respiratory distress syndrome, cardiac ischaemia, coronary artery disease, ventricular remodelling, vascular collapse, inflammatory bowel disease, acute tubular necrosis, psoriasis, rheumatoid arthritis, pre-term birth, fertility, cancer angiogenesis and transplant rejection. From this strikingly diverse list, many important opportunities for disease modification through TLR manipulation can be imagined. Their role as potential targets for therapeutic intervention is just beginning to be appreciated, and the current status of these treatment strategies is reviewed in this article.

Design of multifunctional peptides expressing both antimicrobial activity and shiga toxin neutralization activity

We have designed novel short peptides expressing both antimicrobial and Shiga-toxin (Stx) neutralization activities by combining nuclear localization signal (NLS) peptides (RIRKKLR, PKKKRKV, and PRRRK) tandemly with globotriaoside (Gb3) mimic peptide (WHWTWL). These fusion peptides exhibited excellent antimicrobial activity against both gram-positive and gram-negative bacteria. A peptide WHWTWLRIRKKLR (Trp-His-Trp-Thr-Trp-Leu-Arg-Ile-Arg-Lys-Lys-Leu-Arg), especially, exhibited about 100 times higher activity than the original NLS peptide. SPR analysis demonstrated that the binding of this peptide to both Stxs was strong: K(d) = 6.6 x 10(-6) to Stx-1 and 6.8 x 10(-6) to Stx-2. The in vitro assay against Stx-1 using HeLa cells showed that this peptide increased the survival rate of HeLa cells against the infection of Stx-1. The peptide has been found to maintain high antimicrobial activity, Stx neutralization activity, and no cytotoxicity at its concentration of 7.8-31.3 microg/mL (4.2-16.7 microM). The present peptide design has a prospect of developing potent multifunctional drugs to destroy proteinaceous toxin-producing bacteria and to simultaneously neutralize the toxins released by bacteriolysis.

The Toll-like receptors and their role in septic shock

The Toll-like receptors (TLRs) are a class of pattern recognition molecules with unique functions in the innate and the acquired immune systems. The innate immune response has evolved as the immediate host defence system in response to foreign structures and it also serves to prime the adaptive immune response. As such, the TLRs set the tone and pace of the inflammatory response that follows initial contact with a microbial pathogen over the course of the following minutes, hours and days. Sepsis, a leading cause of death in critically ill patients worldwide, is defined as 'the systemic inflammatory response syndrome that occurs during infection' [1]; that is, sepsis is the orchestration of the events controlled by the gene products triggered by signals transduced through the TLRs. Through analysis of the human genome, ten TLRs have been identified, and several of them have been characterised with respect to their associated ligands. Following engagement of the cognate ligand to the ectodomain of each TLR, the assembly of intracellular homo- or heterodimers or multimers induces cell signalling. The receptors are variably expressed on different types of cells, such as neutrophils, dendritic cells, lymphocytes, endothelial cells etc. and can be up- and downregulated, blocked or triggered by mimetic substances. By controlling or modifying TLR responses, the trajectory of the entire septic process may be modified. This review covers the events responsible for TLR activation in detail, with an emphasis on possible points of pharmacological intervention.

Genome-wide gene expression in response to parasitoid attack in Drosophila

BACKGROUND

Parasitoids are insect parasites whose larvae develop in the bodies of other insects. The main immune defense against parasitoids is encapsulation of the foreign body by blood cells, which subsequently often melanize. The capsule sequesters and kills the parasite. The molecular processes involved are still poorly understood, especially compared with insect humoral immunity.

RESULTS

We explored the transcriptional response to parasitoid attack in Drosophila larvae at nine time points following parasitism, hybridizing five biologic replicates per time point to whole-genome microarrays for both parasitized and control larvae. We found significantly different expression profiles for 159 probe sets (representing genes), and we classified them into 16 clusters based on patterns of co-expression. A series of functional annotations were nonrandomly associated with different clusters, including several involving immunity and related functions. We also identified nonrandom associations of transcription factor binding sites for three main regulators of innate immune responses (GATA/srp-like, NF-kappaB/Rel-like and Stat), as well as a novel putative binding site for an unknown transcription factor. The appearance or absence of candidate genes previously associated with insect immunity in our differentially expressed gene set was surveyed.

CONCLUSION

Most genes that exhibited altered expression following parasitoid attack differed from those induced during antimicrobial immune responses, and had not previously been associated with defense. Applying bioinformatic techniques contributed toward a description of the encapsulation response as an integrated system, identifying putative regulators of co-expressed and functionally related genes. Genome-wide studies such as ours are a powerful first approach to investigating novel genes involved in invertebrate immunity.

The Role of Ubiquitination in Drosophila Innate Immunity

Infection of Drosophila by Gram-negative bacteria triggers a signal transduction pathway (the IMD pathway) culminating in the expression of genes encoding antimicrobial peptides. A key component in this pathway is a Drosophila IkappaB kinase (DmIKK) complex, which stimulates the cleavage and activation of the NF-kappaB transcription factor Relish. Activation of the DmIKK complex requires the MAP3K dTAK1, but the mechanism of dTAK1 activation is not understood. In human cells, the activation of TAK1 and IKK requires the human ubiquitin-conjugating enzymes Ubc13 and UEV1a. Here we demonstrate that the Drosophila homologs of Ubc13 and UEV1a are similarly required for the activation of dTAK1 and the DmIKK complex. Surprisingly, we find that the Drosophila caspase DREDD and its partner dFADD are required for the activation of DmIKK and JNK, in addition to their role in Relish cleavage. These studies reveal an evolutionarily conserved role of ubiquitination in IKK activation, and provide new insights into the hierarchy of signaling components in the Drosophila antibacterial immunity pathway.

Structural and functional differences of Litopenaeus vannamei crustins

Penaeid crustins were described in Litopenaeus vannamei and L. setiferus as proteins belonging to an antibacterial peptide family with similar sequences but different sizes. Six crustin-coding clones were isolated from a cDNA library from L. vannamei hemocytes, sequenced and compared. Two different isoforms (named I and P) were found, based on two nucleotide differences that produce one change in amino acid sequence (Ile/Pro). Other single differences in nucleotide sequences were also noted, but they did not change the translated product. The mRNA steady state levels of crustin I, but not of crustin P, were down regulated by Vibrio alginolyticus inoculation. Thus, the differences among penaeid crustins seem to be associated with one amino acid substitution, which affects their expression after bacterial inoculation. By structural similarity, shrimp crustins seem to belong to an antibacterial WAP-domain containing protein family.

Unravelling complexities in human malaria transmission dynamics in Africa through a comprehensive knowledge of vector populations

Malaria transmission dynamics is highly variable throughout Africa: inoculation rates vary from almost null to more than a 1000 infective bites per year, transmission can occur throughout the year or only during a couple of months, and heterogeneities are also observed between years within the same locale. Depending on the area, as much as five different anophelines species can transmit parasites to the human population. Major vectors are Anopheles gambiae, Anopheles arabiensis, Anopheles funestus, Anopheles nili and Anopheles moucheti. They all belong to species complexes or groups of closely related species that are very difficult to set apart on morphological grounds. Recent research on the bionomics, morphology and genetics of these mosquito species and populations produced innovative results. New species were described and straightforward molecular identification tools were implemented. We review here these recent findings and discuss research opportunities in light of recent advances in molecular entomology and genomics.

In vivo dynamics of an immune response in the bumble bee Bombus terrestris

Concepts from evolutionary ecology have recently been applied to questions of immune defences. However, an important but often neglected aspect is the temporal dynamics of the simple immune measures used in ecological studies. Here, we present observations for workers of the bumble bee Bombus terrestris on the dynamics of the phenoloxidase (PO) system, antibacterial activity, and the total number of haemocytes following a challenge with immune elicitors (LPS, Laminarin), over a time-span ranging from 1min to 14 days. The dynamics of the PO measurement showed a complex pattern and was correlated with haemocyte counts. Antibacterial activity, on the other hand, increased sharply between 2 and 24h post-challenge followed by a slow decrease. Surprisingly, the effects of a challenge lasted up to 14 days.

Exploiting the potential of insects for in vivo pathogenicity testing of microbial pathogens

Conventional assays for quantifying the virulence of microbial pathogens and mutants have traditionally relied upon the use of a range of mammalian species. A number of workers have demonstrated that insects can be used for evaluating microbial pathogenicity and provide results comparable to those that can be obtained with mammals since one component of the vertebrate immune system, the innate immune response, remains similar to that found in insects. Larvae of the Greater Wax Moth Galleria mellonella have been used to evaluate the virulence of a range of bacterial and fungal pathogens and a correlation with the virulence of these microbes in mice has been established. This review highlights the similarities of the vertebrate and insect innate immune responses to infection and identifies the potential use of insects for the in vivo evaluation of the microbial pathogenicity.

Induced immunity in Antheraea assama Ww larvae against flacherie causing Pseudomonas aeruginosa AC-3

This study reports for the first time the induction of immunity in Antheraea assama Ww larvae against bacterial flacherie. In silkworms group of disease caused by bacteria are collectively called "flacherie." This refers to the flaccid condition of the larvae due to the infections of bacterial strains pathogenic to muga silkworm. Antibacterial activity against pathogenic Pseudomonas aeruginosa AC-3 causing flacherie, was induced by injection of heat-killed cells of the same strain. Experiments on larval survivability and viable cell count revealed peak immune response on third day. Comparison of the amount of food ingested, excreta produced and larval weight of the saline-injected control, live bacteria-challenged larvae and heat-killed bacteria-injected larvae "(vaccinated)" confirmed the development of immunity against bacterial infection in the "vaccinated" set. The haemolymph of A. assama larvae was analyzed for proteins associated with bacterial infection. Out of the total 32 detected proteins, eleven (A1-2, A15-20, A22-23, and A29) were constitutively synthesized in both the control and live bacteria-injected larvae. Four inducible proteins A4, A9-10, and A21 were detected in the haemolymph of the live bacteria-injected larvae. Synthesis of rest of the proteins varied between the control and their live bacteria-injected counterparts. General protein profile of "vaccinated" larvae injected with live bacteria were found to be similar to that of the saline-injected control.

Molecular evidence for the expression of angiotensin converting enzyme in hemocytes of Locusta migratoria: stimulation by bacterial lipopolysaccharide challenge

The presence of angiotensin converting enzyme (ACE) in insects has been reported many times, but numerous questions about the functional role of this enzyme in insects remain. Here we show by RT-PCR experiments that ACE has a wide tissue distribution in Locusta migratoria, suggesting diverse roles for this enzyme in the locust. Immune challenge through injection of bacterial lipopolysaccharides resulted in a tenfold increase of ACE gene transcripts in the hemocytes and is suggestive for a role of ACE in the cellular defense of the locust. However, phenotypic knockout experiments with the ACE inhibitor captopril showed that ACE is not essential for the efficient clearance of injected E. coli bacteria.

Drosophila melanogaster antimicrobial defense

The Drosophila melanogaster host defense is complex but remarkably efficient. It is a multifaceted response to a variety of fungal, bacterial, and parasitic invaders. Current knowledge is discussed on recognition of infectious microorganisms and on the activation of intracellular signaling cascades that concur with the expression of numerous immune-responsive genes, among which, to date, the most prominent appear to encode potent antimicrobial peptides.

Caenorhabditis elegans: an emerging genetic model for the study of innate immunity

Invaluable insights into how animals, humans included, defend themselves against infection have been provided by more than a decade of genetic studies that have used fruitflies. In the past few years, attention has also turned to another simple animal model, the nematode worm Caenorhabditis elegans. What exactly have we learned from the work in Drosophila? And will research with C. elegans teach us anything new about our response to pathogen attack?

Cross-species infections and their analysis

The ability of certain pathogens to infect multiple hosts has led to the development of genetically tractable nonvertebrate hosts to elucidate the molecular mechanisms of interactions between these pathogens and their hosts. The use of plant, insect, nematode, and protozoan hosts to study human pathogens has facilitated the elucidation of molecular nature of pathogenesis and host responses. Analyses of virulence of multihost pathogens on their respective hosts revealed that pathogens utilize many universal offensive strategies to overcome host defenses, irrespective of the evolutionary lineage of the host. Likewise, genetic dissections of the defense response of the nonvertebrate hosts have also shown that key features underlying host defense responses are highly conserved. This review summarizes how the information gained from the analysis of cross-species infections contributes to our understanding of host-pathogen interactions.