Variability and function of immune genes in the mussel Mytilus galloprovincialis

Mytilus galloprovincialis is a bivalve mollusc of great commercial interest worldwide that lives anchored to the rocks and has a filtering way of life. Despite being constantly exposed to pathogens, no mass mortality events have been recorded in the natural environment (something that has occurred with other bivalve species such as oysters or clams). This immune resistance seems to reside in the great variability of immune molecules that the mussel genome encodes. Because of that, it has become interesting to study the immune response in infection situations, as well as the analysis of variability and function of some key peptides in the defense to diseases of these animals

AG5 is a potent non-steroidal anti-inflammatory and immune regulator that preserves innate immunity

12 pages, 5 figures.-- This is an open access article under the CC BY-NC-ND licenseAn archetypal anti-inflammatory compound against cytokine storm would inhibit it without suppressing the innate immune response. AG5, an anti-inflammatory compound, has been developed as synthetic derivative of andrographolide, which is highly absorbable and presents low toxicity. We found that the mechanism of action of AG5 is through the inhibition of caspase-1. Interestingly, we show with in vitro generated human monocyte derived dendritic cells that AG5 preserves innate immune response. AG5 minimizes inflammatory response in a mouse model of lipopolysaccharide (LPS)-induced lung injury and exhibits in vivo anti-inflammatory efficacy in the SARS-CoV-2-infected mouse model. AG5 opens up a new class of anti-inflammatories, since contrary to NSAIDs, AG5 is able to inhibit the cytokine storm, like dexamethasone, but, unlike corticosteroids, preserves adequately the innate immunity. This is critical at the early stages of any naïve infection, but particularly in SARS-CoV-2 infections. Furthermore, AG5 showed interesting antiviral activity against SARS-CoV-2 in humanized miceThis work has been supported by NextGenerationEU Recovery and Resilience Facility (RRF) through the PTI+ Global Health Platform of Spanish National Research Council, grants SGL2103023 (PBA), SGL2103053 (MMA) and SGL2103015 (MM); by Spanish National Research Council through the program “Ayudas extraodinarias a proyectos de investigacion en el marco de las medidas urgentes extraodinarias para hacer frente al impacto económico y social del COVID-19”, grants CSIC-COV19-093 (PBA) and CSIC-COV19-117 (MM); by Generalitat Valenciana through the program “Ayudas urgentes para proyectos de investigación, desarrollo tecnológico e innovación (I+D+i) por la COVID-19”, grant GVA-COVID19/2021/059 (PBA); by the Conference of Rectors of the Spanish Universities, Spanish National Research Council and Banco Santander through the FONDO SUPERA COVID-19, grant CAPriCORn (JSM, JMB); by Severo Ochoa center of excellence program (grant CEX2021-001230-S) (PBA)Peer reviewe

Comparative Genomics Reveals a Significant Sequence Variability of Myticin Genes in Mytilus galloprovincialis

Myticins are cysteine-rich antimicrobial peptides highly expressed in hemocytes of Mytilus galloprovincialis. Along with other antimicrobial peptides (AMPs), myticins are potent effectors in the mussel immune response to pathogenic infections. As intertidal filter-feeders, mussels are constantly exposed to mutable environmental conditions, as well as to the presence of many pathogens, and myticins may be key players in the great ability of these organisms to withstand these conditions. These AMPs are known to be characterized by a remarkable sequence diversity, which was further explored in this work, thanks to the analysis of the recently released genome sequencing data from 16 specimens. Altogether, we collected 120 different sequence variants, evidencing the important impact of presence/absence variation and positive selection in shaping the repertoire of myticin genes of each individual. From a functional point of view, both the isoelectric point (pI) and the predicted charge of the mature peptide show unusually low values compared with other cysteine-rich AMPs, reinforcing previous observations that myticins may have accessory functions not directly linked with microbe killing. Finally, we report the presence of highly conserved regulatory elements in the promoter region of myticin genes, which might explain their strong hemocyte-specific expression

Comparative Genomics Reveals a Significant Sequence Variability of Myticin Genes in Mytilus galloprovincialis

© 2020 by the authors.Myticins are cysteine-rich antimicrobial peptides highly expressed in hemocytes of Mytilus galloprovincialis. Along with other antimicrobial peptides (AMPs), myticins are potent effectors in the mussel immune response to pathogenic infections. As intertidal filter-feeders, mussels are constantly exposed to mutable environmental conditions, as well as to the presence of many pathogens, and myticins may be key players in the great ability of these organisms to withstand these conditions. These AMPs are known to be characterized by a remarkable sequence diversity, which was further explored in this work, thanks to the analysis of the recently released genome sequencing data from 16 specimens. Altogether, we collected 120 different sequence variants, evidencing the important impact of presence/absence variation and positive selection in shaping the repertoire of myticin genes of each individual. From a functional point of view, both the isoelectric point (pI) and the predicted charge of the mature peptide show unusually low values compared with other cysteine-rich AMPs, reinforcing previous observations that myticins may have accessory functions not directly linked with microbe killing. Finally, we report the presence of highly conserved regulatory elements in the promoter region of myticin genes, which might explain their strong hemocyte-specific expression.This research was funded by the Spanish Ministerio de Ciencia, Innovación y Universidades (AEI/EU-FEDER RTI2018-095997-B-I00) and the EU-H2020 VIVALDI (678589). Our laboratory is funded by EU Feder Programa Interreg España-Portugal 0474_BLUEBIOLAB and IN607B 2019/01 from Consellería de Economía, Emprego e Industria (GAIN), Xunta de Galicia. M.R.-C. was supported by a Spanish AEI/EU-FEDER predoctoral contract BES-2016-076302.Peer reviewe

Metatranscriptomics to unmask marine mollusca virome

Poster.-- XVI Congreso Nacional de Virología, Málaga, 6-9 de septiembre de 2022The high abundance of microorganisms that inhabit the sea is a potential threat to marine metazoans. For instance, it is estimated that 1023 viral infections occur every second in oceans. Therefore, marine metazoans must show viral entities naturally constituting their microbiome. In the last years, the use of metatranscriptomics as an unbiased method to describe microbial variability, has gained interest. Due to their filter-feeding behaviour that force most molluscs to be in touch and even accumulate potential pathogens, in the present work, about 60 SRA datasets belonging to molluscs from 16 geographical origins and 17 different tissues were analyzed looking for viral sequences. Among the results, viruses typically identified in molluscs such as Abalon herpesvirus type 2 Taiwan/2007, Wenzhou gastropodes virus 2, Mytilus mediterranean mussel adintovirus or Southern pygmy squid flavivirus were found. Moreover, we could identify some others that are relatively new and remain unclassified such as Barns Ness breadcrumb sponge aquatic picorna-like virus 2, Beihai picorna-like virus 56 and Wenzhou picorna-like virus 51. Finally, the studied samples also showed in some cases viral sequences belonging to mammalian viruses or plant virusesN

Exposure of zebrafish (Danio rerio) to an environmentally relevant concentration of antibiotics impairs the intestinal complement pathway and increases susceptibility to diseases

Poster.-- 2nd International Symposium Mucosal Health in Aquaculture, Madrid, 3-6 October 2022N

Mussel antiviral transcriptome response and elimination of viral haemorrhagic septicaemia virus (VHSV)

12 pages, 6 figures.-- Under a Creative Commons licenseAs filter-feeding bivalves, mussels have been traditionally studied as possible vectors of different bacterial or viral pathogens. The absence of a known viral pathogen in these bivalves makes it particularly interesting to study the interaction of the mussel innate immune system with a virus of interest. In the present work, mussels were challenged with viral haemorrhagic septicaemia virus (VHSV), which is a pathogen in several fish species. The viral load was eliminated after 24 h and mussels evidenced antiviral activity towards VHSV, demonstrating that the virus was recognized and eliminated by the immune system of the host and confirming that mussels are not VHSV vectors in the marine environment. The transcriptome activating the antiviral response was studied, revealing the involvement of cytoplasmic viral sensors with the subsequent activation of the JAK-STAT pathway and several downstream antiviral effectors. The inflammatory response was inhibited with the profound downregulation of MyD88, shifting the immune balance towards antiviral functions. High modulation of retrotransposon activity was observed, revealing a mechanism that facilitates the antiviral response and that had not been previously observed in these species. The expression of several inhibitors of apoptosis and apoptosis-promoting genes was modulated, although clear inhibition of apoptosis in bivalves after severe viral infection and subsequent disease was not observed in this study. Finally, the modulated expression of several long noncoding RNAs that were correlated with genes involved in the immune response was detectedThis work was supported by the Ministerio de Ciencia e Innovación (PID2021-124955OB-I00) and Xunta de Galicia (IN607B 2022/13). AS was supported by a Spanish AEI/EU-FSE predoctoral contract PRE2019-090760Peer reviewe

Mussels: deciphering the keys behind a successful immune system

Poster.-- Close Encounters IIM (3rd Kind), Vigo, 23 June 2022N

Interaction between Vibrio splendidus and the immune system of Mytilus galloprovincialis

Poster.-- 19th International Conference on Diseases of Fish and Shellfish, Porto, 9th-12th September 2019Bivalves are susceptible to numerous diseases that compromise their culture, producing economic losses all over the world. Mussels that cohabitate in the same areas as oysters and clams have experienced massive mortalities due to viral and bacterial infections. As an example, the ostreid herpesvirus 1 (OsHV-1) has caused massive mortalities in oysters (Crassostrea gigas) in different parts of the world. However, until now, high mortalities have never been reported in the field for Mediterranean mussel (Mytilus galloprovincialis). This resistance could be due to the high expression of antimicrobial peptides that has been observed in musselEU, Horizon 2020, VIVALDI (678589) and the Spanish project AGL2015-65705-RPeer reviewe

An environmentally relevant concentration of antibiotics impairs the immune system of zebrafish (Danio rerio) and increases susceptibility to virus infection

18 pages, 10 figures.-- This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY)In this work, we analysed the transcriptome and metatranscriptome profiles of zebrafish exposed to an environmental concentration of the two antibiotics most frequently detected in European inland surface water, sulfamethoxazole (SMX) and clarithromycin (CLA). We found that those animals exposed to antibiotics (SMX+CLA) for two weeks showed a higher bacterial load in both the intestine and kidney; however, significant differences in the relative abundance of certain bacterial classes were found only in the intestine, which also showed an altered fungal profile. RNA-Seq analysis revealed that the complement/coagulation system is likely the most altered immune mechanism, although not the only one, in the intestine of fish exposed to antibiotics, with numerous genes inhibited compared to the control fish. On the other hand, the effect of SMX+CLA in the kidney was more modest, and an evident impact on the immune system was not observed. However, infection of both groups with spring viremia of carp virus (SVCV) revealed a completely different response to the virus and an inability of the fish exposed to antibiotics to respond with an increase in the transcription of complement-related genes, a process that was highly activated in the kidney of the untreated zebrafish after SVCV challenge. Together with the higher susceptibility to SVCV of zebrafish treated with SMX+CLA, this suggests that complement system impairment is one of the most important mechanisms involved in antibiotic-mediated immunosuppression. We also observed that zebrafish larvae exposed to SMX+CLA for 7 days showed a lower number of macrophages and neutrophilsThis work was funded by projects PID2020-119532RB-I00 of the Spanish Ministerio de Ciencia e Innovación. PP’s postdoctoral contract (Juan de la Cierva Incorporación; IJC2020-042682-I) was funded by the Spanish Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033) and the European Union “NextGenerationEU/PRTR”Peer reviewe