Characterization of antiviral and antibacterial activity ofBombyx moriseroin proteins

Abstract

SummaryLepidopterans as other insects have a very potent innate immune system, which basically comprises cellular and humoral defence mechanisms against bacterial and fungal infections. In lepidopterans, not much is known about the defence mechanisms against viral pathogens, such as baculoviruses. Here we show that small silk proteins of the domesticated silkworm, Bombyx mori, called seroins, act as antiviral agents against a baculovirus pathogen, Bombyx mori nucleopolyhedrovirus (BmNPV). Involvement of these proteins in the inhibition of baculovirus infection was revealed by estimating the viral load upon their dsRNA-mediated knockdown. Additionally, we found through antimicrobial assays that seroins are potent inhibitors of bacterial growth. Binding competition assays followed by antimicrobial assays showed that seroins bind to peptidoglycan, a cell wall component of bacteria. Analysis of bacterial load upon knockdown of seroins resulted in higher proliferation of bacteria. Phylogenetic analysis showed the recent origin of seroins in a few moth species and duplication only in Bombycids. The antiviral and antibacterial activity of seroins shown in this study using several biochemical and molecular biological assays provide strong evidence to characterize them as antimicrobial proteins. Hence, we hypothesize that seroins are potent candidates for use in development of transgene-based disease resistant silkworm strains.

Comparative Proteome Analysis of Multi-Layer Cocoon of the Silkworm, Bombyx mori

“…From the inner layers towards the outer layers, sericin1 increased, sericin3 decreased and then increased and sericin2 showed very low abundance or absence in all cocoon layers ( Fig 2C ). Two major small molecular seroins are known to be antimicrobial proteins [ 4 , 9 , 10 ]. Seroin1 had the highest abundance in the innermost layer and seroin2 had low abundance with slight differences in the cocoon layers ( Fig 2D ).…”

“…Besides fibroins and sericins, proteins with low molecular weights such as seroins and protease inhibitors are found in B . mori cocoon extracts [ 4 , 9 , 10 ]. Recently, we identified 169 proteins in cocoon silk using shotgun liquid chromatography-tandem mass spectrometry (LC-MS/MS) [ 11 ].…”

Novel antibacterial peptides induced by probiotics in Hermetia illucens (Diptera: Stratiomyidae) larvae

“…At the same time, the prevalence of acute infectious diseases due to drug-resistant organisms has caused a serious global challenge, in spite of various efforts being undertaken to cope with them. Among various approaches to solve the above-mentioned problems, biological resources formulated in traditional oriental medicine or ethnomedicine such as centipede, scorpion, leech, and silkworm have been studied widely due to their pharmacological advantages (Feng et al 2007;Calvino and Szczupak, 2008;Xu et al 2010;Zhou et al 2011;Singh et al 2013Singh et al , 2014Lee et al 2015). Nevertheless, the occurrence of infectious pathogens has not been reduced globally, which is still causing serious concerns and problems in the public health field.…”

“…Moreover, the overuse of antibiotics has increased the incidence rate of multidrug-resistant bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and multi-drug-resistant tuberculosis (MDR-TB), demanding immediate action and overhaul in treatment strategy. Among various approaches to solve the above-mentioned problems, biological resources formulated in traditional oriental medicine or ethnomedicine such as centipede, scorpion, leech, and silkworm have been studied widely due to their pharmacological advantages (Feng et al 2007;Calvino and Szczupak, 2008;Xu et al 2010;Zhou et al 2011;Singh et al 2013Singh et al , 2014Lee et al 2015). The larvae of insect have been especially utilized as useful therapeutic resources in Asia and Europe.…”

Silk recycling in larvae of the wax moth, Galleria mellonella (Lepidoptera: Pyralidae)

“…It is proposed that minor silk components such as seroins and proteinase inhibitors protect cocoons against microorganisms and possibly also against mites, insects and other omnivorous animals (Nirmala et al, 2001a, b;Shaik & Sehnal, 2009;Singh et al, 2014). To answer both questions, we fed larvae with raw or processed silk and determined their feeding rate and silk production.…”