Expression Of Antibacterial Peptides Research Articles

Colonic epithelial cell-specific TFEB activation: a key mechanism promoting anti-bacterial defense in response to Salmonella infection.

Colitis caused by infections, especially Salmonella, has long been a common disease, underscoring the urgency to understand its intricate pathogenicity in colonic tissues for the development of effective anti-bacterial approaches. Of note, colonic epithelial cells, which form the first line of defense against bacteria, have received less attention, and the cross-talk between epithelial cells and bacteria requires further exploration. In this study, we revealed that the critical anti-bacterial effector, TFEB, was primarily located in colonic epithelial cells rather than macrophages. Salmonella-derived LPS significantly promoted the expression and nuclear translocation of TFEB in colonic epithelial cells by inactivating the mTOR signaling pathway in vitro, and this enhanced nuclear translocation of TFEB was also confirmed in a Salmonella-infected mouse model. Further investigation uncovered that the infection-activated TFEB contributed to the augmentation of anti-bacterial peptide expression without affecting the intact structure of the colonic epithelium or inflammatory cytokine expression. Our findings identify the preferential distribution of TFEB in colonic epithelial cells, where TFEB can be activated by infection to enhance anti-bacterial peptide expression, holding promising implications for the advancement of anti-bacterial therapeutics.

1,25-Dihydroxyvitamin D3 potentiates the innate immune response of peripheral blood mononuclear cells from Japanese Black cattle.

1,25-Dihydroxyvitamin D3 (1,25(OH)2 D3 ), a bioactive vitamin D, is known to regulate immune responses in mammals. However, its impact on the innate immune responses of Japanese Black cattle, which are beef cattle endemic to Japan, remains unknown. Thus, in this study, we investigated the effect of 1,25(OH)2 D3 on the immune responses of peripheral blood mononuclear cells from Japanese Black cattle. As a result, the treatment of 1,25(OH)2 D3 upregulated the expression of antibacterial peptides, bovine beta-defensin 10 (DEFB10), and lingual antimicrobial peptide (LAP), in the presence and absence of lipopolysaccharide (LPS) stimulation. Moreover, 1,25(OH)2 D3 enhanced the inflammatory responses, including C-X-C motif ligand 8 (CXCL8) and nitric oxide synthase (NOS2), while reducing the expression of anti-inflammatory cytokine IL10, leading to an inflammatory phenotype. However, in contrast to humans and mice, 1,25(OH)2 D3 did not alter the expression of tumor necrosis factor (TNF) and downregulated triggering receptor expressed on myeloid cell 1 (TREM1) with LPS treatment. These results suggest that 1,25(OH)2 D3 potentiates the innate immune responses of Japanese Black cattle, albeit with different effects and mechanisms as compared to humans and mice.

Identification of a dorsal transcription factor (MnDorsal) from Macrobrachium nipponense and its role in innate immunity

Rel/nuclear factor (NF)-κB family of transcription factors paly vital roles in innate immunity response to bacterial and viral infection. Here, we cloned and identified a dorsal homologue (named as MnDorsal) from Macrobrachium nipponense. The full-length cDNA of MnDorsal is 2573 bp with a 1986 bp open reading frame that encodes 661 amino acids. Predicted MnDorsal protein contained a RHD (Rel homology domain), an IPT (Iglike, plexins, and transcriptions factors) domain, and two low complexity regions. Phylogenetic analysis showed that MnDorsal has a closer genetic distance with dorsal homologues from invertebrates. MnDorsal was widely expressed in a variety of tissues, including hemocytes, heart, hepatopancreas, gills, stomach, and intestine. Expression patterns analysis showed that the transcriptional level of MnDorsal in the gills was evidently up-regulated after Staphylococcus aureus, Vibrio parahaemolyticus, white spot syndrome virus, or polyinosinic-polycytidylic acid challenge, suggesting that MnDorsal participates in the immune defenses against pathogens and stimulant challenges. Additionally, the dsRNA-mediated RNA interference analysis showed that knockdown of MnDorsal can significantly inhibit the expression of anti-lipopolysaccharide factor (ALF) and crustin. Further studies revealed that the up-regulated expression of ALFs (MnALF2, MnALF3, and MnALF4) and crustins (MnCrustin3 and MnCrustin4) caused by S. aureus infection were obviously decreased after silencing MnDorsal. These findings suggest that MnDorsal positively regulate the expression of antibacterial peptides (AMPs) during S. aureus infection. Our study will promote to better understand the role of Toll-Dorsal-AMPs pathway in innate immunity response to gram-positive bacterial infection in crustacean.

20-Hydroxyecdysone enhances Immulectin-1 mediated immune response against entomogenous fungus in Locusta migratoria.

Entomogenous fungi are important factors in biological control, but innate immunity of insects restricts the efficiency of fungus infection. 20-hydroxyecdysone (20E) is involved in regulating the immune response of insects. Our previous studies have revealed that 20E enhances the expression of antibacterial peptides in the worldwide pest Locusta migratoria. However, the mechanism by which 20E controls innate immunity against entomogenous fungi is still unknown. In the present study, based on the transcriptome of L. migratoria fat bodies challenged by 20E, immulectin-1 (LmIML-1) was screened and identified to be involved in modulating antifungal immunity. Spatio-temporal expression analysis showed LmIML-1 was highly expressed in the fifth instar nymph stage, and mainly distributed in the fat bodies and hemolymph. Both exogenous and endogenous 20E could increase the transcription of LmIML-1. In contrast, transcription of LmIML-1 did not increase when the 20E signal was blocked by RNAi of LmEcR (ecdysone receptor). The expressed recombinant protein rLmIML-1 possessed agglutination activity and promoted the encapsulation. RNA interference of LmIML-1 reduced the encapsulation of hemocytes, decreased the antifungal activity of plasma against Metarhizium anisopliae and accelerated the death of nymphs under the stress of entomogenous fungus. Meanwhile, 20E did not increase the antifungal activity with silence of LmIML-1 in L. migratoria. 20E enhances antifungal immunity by activating immulectin-1 in L. migratoria. Our findings indicate a potential mechanism of 20E systematically regulating innate immune response to resist pathogens and provide a well-defined molecular target for improving biological control. © 2019 Society of Chemical Industry.

A20 in dendritic cells restrains intestinal anti-bacterial peptide expression and preserves commensal homeostasis.

Microbial dysbiosis commonly occurs in patients with inflammatory bowel diseases (IBD). Exogenous causes of dysbiosis such as antibiotics and diet are well described, but host derived causes are understudied. A20 is a potent regulator of signals triggered by microbial pattern molecules, and A20 regulates susceptibility to intestinal inflammation in mice and in humans. We now report that mice lacking A20 expression in dendritic cells, A20FL/FL CD11c-Cre mice (or A20dDC mice), spontaneously develop colitogenic intestinal dysbiosis that is evident upon weaning and precedes the onset of colitis. Intestines from A20dDC mice express increased amounts of Reg3β and Reg3γ, but not Ang4. A20 deficient DCs promote gut microbiota perturbation in the absence of adaptive lymphocytes. Moreover, A20 deficient DCs directly induce expression of Reg3β and Reg3γ but not Ang 4 in normal intestinal epithelial cell enteroid cultures in the absence of other cell types. These findings reveal a pathophysiological pathway in which defective expression of an IBD susceptibility gene in DCs drives aberrant expression of anti-bacterial peptides and luminal dysbiosis that in turn confers host susceptibility to intestinal inflammation.

Effects of Bombyx mori nuclear polyhedrosis virus on serpin and antibacterial peptide expression in B. mori

The silkworm (Bombyx mori) is a typical and economically important lepidopteran species, and research has resulted in the development and accumulation of breeding lines. Studies of immune-related silkworm genes not only promote our understanding of silkworm immune response mechanisms, but they also inform insect immune molecular diversity research. Here, silkworm proteins were screened using proteomics after Bombyx mori nuclear polyhedrosis virus (BmNPV) infection, and 2368 silkworm proteins were identified, including six antimicrobial peptides and 12 serpins. The mRNA expression levels of these 18 proteins were examined at different times. The results indicated that attacin had the highest expression level, while serpin-5 and cecropin-D exhibited a negative regulatory correlation. These results provide a significant step toward a deeper understanding of B. mori immunoregulation.

Peyer's patch-specific Lactobacillus reuteri strains increase extracellular microbial DNA and antimicrobial peptide expression in the mouse small intestine.

Specific Lactobacillus reuteri is autochthonous Lactobacillus species in humans with potential application in food production as a probiotic. The difference in colonizing Peyer's patches (PP) might decide their health-promoting properties. We aimed to investigate the difference between PP- and lumen-specific L. reuteri on antimicrobial peptide expression in this study. L. reuteri strains were isolated from PP and the lumen of C57BL/6J mice, which were used to treat mice. PP-specific L. reuteri cells stimulate RegIIIγ mRNA expression of the crypt epithelial sample. PP-specific L. reuteri induces accumulation of extracellular DNA (eDNA) in the bottom of crypts. eDNA was extracted from the small-intestinal mucus, the yield of which was significantly increased after the PP-specific L. reuteri treatment. And it increased cytokine production in RAW264.7 murine macrophages. PP-specific L. reuteri significantly increased the relative abundance of Bacteroidetes-, Lactobacillus-, and Proteobacteria-derived eDNA. However, the levels of Strentrophomonas-derived eDNA decreased. These results provide a rationale for the screening of human derived L. reuteri with an immune-modulatory property.

Knockdown of HMGN2 increases the internalization of Klebsiellapneumoniae by respiratory epithelial cells through the regulation of α5β1 integrin expression.

Integrin receptors, a large family of adhesion receptors, are involved in the attachment of Klebsiella pneumoniae to respiratory epithelial cells, and subsequently cause the internalization of K. pneumoniae by host cells. Although a number of molecules have been reported to regulate the expression and activity of integrin receptors in respiratory epithelial cells, the specific underlying molecular mechanisms remain largely unknown. High mobility group nucleosomal binding domain 2 (HMGN2), a non-histone nuclear protein, is present in eukaryotic cells as a ubiquitous nuclear protein. Our previous studies have demonstrated that HMGN2 affects chromatin function and modulates the expression of antibacterial peptide in A549 cells exposed to lipopolysaccharide, which indicates the critical role of HMGN2 in innate immune responses. In addition, our cDNA microarray analysis suggested that HMGN2 knockdown induced the enhanced expression of α5β1 integrin in A549 cells. Therefore, we hypothesized that intercellular HMGN2 may mediate the internalization of K. pneumoniae by altering the expression of α5β1 integrin. Using the A549 cell line, we demonstrated that HMGN2 knockdown induced the increased expression of α5β1 integrin on cell membranes, which resulted in a significant increase in K. pneumoniae internalization. Further results revealed that HMGN2 silencing induced the expression of talin and the activation of α5β1 integrin, which led to actin polymerization following the phosphorylation of FAK and Src. This study suggests a possible therapeutic application for bacterial internalization by targeting HMGN2 in order to treat K. pneumoniae infection.

Interleukin-29: Just an extra string in the bow of Th17 cells or a target for therapeutic exploitation?

In this issue, Witte and colleagues describe the ability of IL-29, a type III interferon, to induce keratinocyte expression of CXCL9, CXCL10 and CXCL11, three chemokines implicated in the trafficking of activated Th1 T cells into sites of inflammation [1]. Given that Th17 cells may be the principal source of IL-29, this finding both strengthens the role of Th17 cells in antiviral defenses and may help explain the mixed Th1/Th17 phenotype seen in psoriasis, a common inflammatory skin disease. Immune competence at the epithelial barriers of the gut, lungs and skin takes a concerted effort from the epithelial cells themselves, antibodies, complement, and both resident and infiltrating immune cells to be able to mount a timely response to a barrier breach and invasion by potentially pathogenic microbes. T cells fulfill a vital defensive role in the epithelia, with non-recirculating tissue resident memory T cells providing rapid specific immune protection against the pathogens most commonly encountered in barrier tissues, supported by innate immune cells and circulating T cells that can be called upon as needed [2, 3]. One trade-off of having a battalion of heavily armed T cells within the tissues is that loss of control or dysregulation of these cells can initiate and sustain chronic autoimmune and inflammatory diseases, such as Crohn’s disease, multiple sclerosis and psoriasis. Over the last decade, the contribution of Th17 cells has been recognized as a vital aspect of immunity at epithelial barriers [4]; however, Th17 cells and IL-17A have also been implicated in a number of their pathologies [5]. IL-17A is a potent inducer of antimicrobial protein and peptide expression by epithelia. In the skin, IL-17A works synergistically with several cytokines including IFN-γ [6] and TNF-α [7] to potently drive the induction of a range of antimicrobial peptides and proteins including S100A7, A8 and A9, the cathelicidin LL-37 and human β-defensins (HBD)-2, 3 and 4. Working in concert, these antimicrobial peptides provide a broad spectrum of antibacterial activity and have also been demonstrated to have efficacy against some viruses [8]. In addition to their antimicrobial activities, the defensins have roles in the regulation of both innate and acquired immunity. HBD-2, 3 and 4 induce pro-inflammatory cytokine expression (IL-6, CXCL10, CCL2, CCL5 and CCL20), and the migration and proliferation of keratinocytes, promot ing wound heal ing [9] . HBD-2 is a lso a chemoattractant for macrophages, mast cells, activated neutrophils, memory T cells and dendritic cells (DCs) [10]. The converse is also true: when used at a high enough concentration, chemokines like CCL20 have been shown to possess antimicrobial activities [11]. Plaque psoriasis is a common inflammatory disease of the skin, thought to be driven by Th1 and Th17 Tcells unleashing a Bcytokine storm^, inducing keratinocyte hyperproliferation and perturbed epidermal maturation, resulting in a compromised epidermal barrier characteristic of the disease [12]. Elevated expression of antibacterial peptides and proteins in lesional psoriasis skin is well established, with an extensive inflammatory cytokine milieu driving antimicrobial peptide expression [13], some of which are amongst the most highly upregulated molecules in lesional psoriatic skin [14]. IL-17A is also a potent inducer of an array of antiviral genes such as myxovirus resistance A (MX1) and oligoadenylate synthetases (OAS); thus, Th17 T cells have the potential to contribute to antiviral defenses at epithelial barriers. In addition to increased expression of antimicrobial peptides, antiviral * Andrew Johnston andjoh@med.umich.edu

Flagellin/Toll‐like Receptor 5 Induces Interleukin‐17C in Human Nasal Epithelia

Objectives: Recently, it has been reported that IL-17C mediates innate immune responses against microbial infection and inflammation in mucosal epithelium. However, little is known about the expression and biological function of IL-17C in human airway epithelium. Methods: The family of Interleukin-17 (IL-17) cytokine is involved in host defense responses and various inflammatory diseases. Many studies indicate that IL-17A and IL-17F play an important role in the pathogenesis of airway inflammatory diseases. In this study, we found that IL-17C mRNA expression was strongly induced by inflammatory cytokines such as TNF-α or IL-1Î2 and bacterial flagellin, recognized by toll-like receptor 5 (TLR5), in primary cultured normal human nasal epithelial (NHNE) cells. We also confirmed that IL-17C protein production was enhanced by TNF-α, IL-1Î2 and flagellin. Results: We demonstrated that pretreatment of neutralizing antibody against TLR5 completely inhibited flagellin-induced IL-17C expression, indicating elevated IL-17C expression is specifically mediated by flagellin/TLR5 engagement. Moreover, IL-17C stimulation induced innate immune responses including the expression of antibacterial peptides and proinflammatory cytokines in NHNE cells. Taken together, these results show that IL-17C expression is enhanced in response to inflammation and flagellin/TLR5 activation and involved in inflammatory process in human nasal epithelial cells. Conclusions: Our findings suggest that IL-17C cytokine may play an important role in TLR5-dependent innate immune responses of human airway epithelia.

Genome analysis and signature discovery for diving and sensory properties of the endangered Chinese alligator

Crocodilians are diving reptiles that can hold their breath under water for long periods of time and are crepuscular animals with excellent sensory abilities. They comprise a sister lineage of birds and have no sex chromosome. Here we report the genome sequence of the endangered Chinese alligator (Alligator sinensis) and describe its unique features. The next-generation sequencing generated 314 Gb of raw sequence, yielding a genome size of 2.3 Gb. A total of 22 200 genes were predicted in Alligator sinensis using a de novo, homology- and RNA-based combined model. The genetic basis of long-diving behavior includes duplication of the bicarbonate-binding hemoglobin gene, co-functioning of routine phosphate-binding and special bicarbonate-binding oxygen transport, and positively selected energy metabolism, ammonium bicarbonate excretion and cardiac muscle contraction. Further, we elucidated the robust Alligator sinensis sensory system, including a significantly expanded olfactory receptor repertoire, rapidly evolving nerve-related cellular components and visual perception, and positive selection of the night vision-related opsin and sound detection-associated otopetrin. We also discovered a well-developed immune system with a considerable number of lineage-specific antigen-presentation genes for adaptive immunity as well as expansion of the tripartite motif-containing C-type lectin and butyrophilin genes for innate immunity and expression of antibacterial peptides. Multifluorescence in situ hybridization showed that alligator chromosome 3, which encodes DMRT1, exhibits significant synteny with chicken chromosome Z. Finally, population history analysis indicated population admixture 0.60-1.05 million years ago, when the Qinghai-Tibetan Plateau was uplifted.

The Clinical Impact of Vitamin D in Children With Atopic Dermatitis

The Clinical Impact of Vitamin D in Children With Atopic Dermatitis

IL-17RE is the functional receptor for IL-17C and mediates mucosal immunity to infection with intestinal pathogens

Interleukin 17 receptor E (IL-17RE) is an orphan receptor of the IL-17 receptor family. Here we show that IL-17RE is a receptor specific to IL-17C and has an essential role in host mucosal defense against infection. IL-17C activated downstream signaling through IL-17RE-IL-17RA complex for the induction of genes encoding antibacterial peptides as well as proinflammatory molecules. IL-17C was upregulated in colon epithelial cells during infection with Citrobacter rodentium and acted in synergy with IL-22 to induce the expression of antibacterial peptides in colon epithelial cells. Loss of IL-17C-mediated signaling in IL-17RE-deficient mice led to lower expression of genes encoding antibacterial molecules, greater bacterial burden and early mortality during infection. Together our data identify IL-17RE as a receptor of IL-17C that regulates early innate immunity to intestinal pathogens.

Genetic evidence for a protective role of the peritrophic matrix against intestinal bacterial infection in Drosophila melanogaster

The peritrophic matrix (PM) forms a layer composed of chitin and glycoproteins that lines the insect intestinal lumen. This physical barrier plays a role analogous to that of mucous secretions of the vertebrate digestive tract and is thought to protect the midgut epithelium from abrasive food particles and microbes. Almost nothing is known about PM functions in Drosophila, and its function as an immune barrier has never been addressed by a genetic approach. Here we show that the Drosocrystallin (Dcy) protein, a putative component of the eye lens of Drosophila, contributes to adult PM formation. A loss-of-function mutation in the dcy gene results in a reduction of PM width and an increase of its permeability. Upon bacterial ingestion a higher level of expression of antibacterial peptides was observed in dcy mutants, pointing to an influence of this matrix on bacteria sensing by the Imd immune pathway. Moreover, dcy-deficient flies show an increased susceptibility to oral infections with the entomopathogenic bacteria Pseudomonas entomophila and Serratia marcescens. Dcy mutant flies also succumb faster than wild type upon ingestion of a P. entomophila toxic extract. We show that this lethality is due in part to an increased deleterious action of Monalysin, a pore-forming toxin produced by P. entomophila. Collectively, our analysis of the dcy immune phenotype indicates that the PM plays an important role in Drosophila host defense against enteric pathogens, preventing the damaging action of pore-forming toxins on intestinal cells.

A phytoceramide analog stimulates the production of chemokines through CREB activation in human endothelial cells

Innate immunity is the front-line of self-defense against microbial infection. In mammals, innate immunity interacts with adaptive immunity and has a key role in the regulated immune response. From a pharmaceutical point of view, innate immunity is an ideal target for the development of immunoregulators. Therefore, we aimed to isolate and characterize a novel mammalian immunoregulator isolated from the thermophilic cellulotic fungus Talaromyces sp. 2′-(R)-hydroxy-C24 phytoceramide (C24(2′OH)Phy) was isolated from Talaromyces sp. using a Drosophila ex vivo culture system. C24(2′OH)Phy suppressed the immune deficiency (IMD) pathway-dependent expression of antibacterial peptides in Drosophila, whereas it stimulated the production of chemokines in human cells. Structure activity relationship studies of C24(2′OH)Phy analogs revealed that both the 2′-(R)-hydroxylignoceroyl group and phytoceramide backbone are essential for the biologic activity of C24(2′OH)Phy. Microarray analysis revealed that C24(2′OH)Phy selectively activates the transcription of inflammatory response genes, including chemokines. Furthermore, a reporter gene assay and small interfering RNA analysis demonstrated that C24(2′OH)Phy stimulates chemokine production through cAMP response element-binding protein activation in human cells. C24(2′OH)Phy may be a lead immunostimulating compound in humans.

Lactobacillus paracaseiReduces Intestinal Inflammation in Adoptive Transfer Mouse Model of Experimental Colitis

Studies showed that specific probiotics provide therapeutic benefits in inflammatory bowel disease. In vitro evidence suggested that Lactobacillus paracasei also called ST11 (CNCM I-2116) is a potent strain with immune modulation properties. However, little is known about its capacity to alleviate inflammatory symptoms in vivo In this context, the main objective of this study was to investigate the role of ST11 on intestinal inflammation using the adoptive transfer mouse model of experimental colitis. Rag2−/− recipient mice were fed with ST11 (109 CFU/day)a month prior toinduce colitis by adoptive transfer of naive T cells. One month later, in clear contrast to nonfed mice, weight loss was significantly reduced by 50% in ST11-fed mice. Further analysis of colon specimens revealed a significant reduction neutrophil infiltration and mucosal expression of IL1β, IL-6, and IL12 proinflammatory cytokines, whereas no consistent differences in expression of antibacterial peptides or tight junction proteins were observed between PBS and ST11-fed mice. All together, our results demonstrate that oral administration of ST11 was safe and had a significant preventive effect on colitis. We conclude that probiotics such as Lactobacillus paracasei harbor worthwhile in vivo immunomodulatory properties to prevent intestinal inflammation by nutritional approaches.

Smt3 is required for the immune response of silkworm, Bombyx mori

SUMO works in a similar way as ubiquitin to alter the biological properties of a target protein by conjugation. The homologous gene of SUMO named BmSmt3 was identified for the first time in silkworm. The expression of BmSmt3 was enhanced in the fat body of silkworm after immune challenge. However, the expression of BmSmt3 after immune challenge was almost invariant in silk gland, which is the nonimmune organ in silkworm. In addition, the expression of BmRelA and CecropinB1 was decreased significantly in pupae after the BmSmt3 was knocked down in vivo. According to our results, BmSmt3 might participate in the immune response through regulating the expression of BmRelA gene, which can further regulate the expression of antibacterial peptide subsequently in silkworm.

Propionibacterium acnes and Sebaceous Lipogenesis: A Love–Hate Relationship?

In this issue, Iinuma et al. show that Propionibacterium acnes (P. acnes)-conditioned medium and formalin-killed P. acnes augment intracellular lipid formation in hamster sebocytes by increasing the de novo synthesis of triacylglycerols. This commentary summarizes the current knowledge of the association of P. acnes with sebaceous lipogenesis, inflammation, and innate immunity, and points out the concurrent evidence that P. acnes-induced lipids may represent a recruitment of allies and/or enemies of the human skin.

Mammary Gland Expression of Antibacterial Peptide Genes to Inhibit Bacterial Pathogens Causing Mastitis

As a step toward prevention of bovine mastitis, a plasmid-mediated gene transfer technique was used to enable mammary cells to synthesize and secrete bovine lactoferricin and bovine tracheal antibacterial peptides. For this purpose, a series of mammary tissue-specific expression vectors, harboring the antibacterial peptide gene, the 5′-flanking regulation sequence of goat β-casein, and the bovine growth hormone polyadenylation signal sequence, were constructed using a eukaryotic expression vector pIRES1-neo. The mammary gland tissue-specific expression vector carrying the antimicrobial peptide genes dissolved in physiologic saline was injected directly into the lactating mammary glands of goats. The milk samples after injection were checked by Tricine-SDS-PAGE and bacterium inhibition zone assay. The results of these tests showed that the mammary gland tissue-specific expression vector driven by the goat β-casein gene promoter could efficiently direct the expression of antibacterial peptides in goat milk; the expression of antibacterial proteins lasted for 3 to 6 d. All of the milk samples collected from the mammary glands that had been injected with different vectors harboring the antibacterial peptide gene(s) exhibited bacteriostatic activity against different bacterial pathogens. These results demonstrated that the mammary gland tissue-specific expression vector could be used to introduce antibacterial peptide gene into the goat mammary gland, enabling secretion of a bioactive form of antibacterial peptide in the milk. This successful expression of antibacterial peptides in goat mammary glands provided a possible method to prevent mastitis in ruminants.

Effect of nucleopolyhedrovirus infection on antibacterial activity and antibacterial peptide production in larvae of the silkworm, Bombyx mori (Lepidoptera: Bombycidae)

Effects of nucleopolyhedrovirus (NPV) on antibacterial peptide gene expression and peptide production in Bombyx mori larvae remain unclear. Antibacterial activity was first examined with the hemolymph from B. mori larvae infected with B. mori NPV (BmNPV) and injected with bacterial lipopolysaccharide (LPS) 72 h postinfection (p.i.). No antibacterial activity was detected. Expression of four antibacterial peptide genes were next analyzed in B. mori larvae infected with BmNPV. Although antibacterial peptide genes were activated upon injection of LPS in the larvae infected with BmNPV, none were triggered by BmNPV alone. Production of the antibacterial peptide cecropin B was next examined by Western blotting. Cecropin B was not detected from 72 to 96 h p.i. The absence of cecropin B was coincident with an increase in BmNPV cysteine proteinase (CP) activity. Cecropin B production was confirmed at 96 h p.i. in the larvae infected with CP-deficient BmNPV, indicating that the antibacterial peptides are degraded by BmNPV-CP at a very late stage of viral infection. These results suggest that BmNPV neither activates nor suppresses gene expression of antibacterial peptides and that absence of antibacterial activity is due to BmNPV-CP in B. mori larvae.