Transcriptome-wide analysis of wild Asari (=Manila) clams affected by the Brown Muscle Disease: Etiology and impacts of the disease

Recently, we reported an emerging pathology named Brown Muscle Disease (BMD) affecting Asari clams inhabiting the most productive area for this species in France, the Arcachon Bay. The main macroscopic feature of the pathology relies on the atrophy of the posterior adductor muscle, affecting the ability of clams to burry. The research of the etiological agent of BMD privileged a viral infection. Contrary to healthy clams, infected animals are always found at the surface of the sediment and exhibit 30 nm virus-like particles in muscle, granulocytic and rectal cells. In order to get more insights on the etiology and impacts of the BMD on clams, we took advantage in the present study of next generation sequencing technologies. An RNA-Seq approach was used (i) to test whether viral RNA sequences can be specifically found in the transcriptome of diseased animals and (ii) to identify the genes that are differentially regulated between diseased and healthy clams. Contrary to healthy buried animals, in diseased clams one sequence showing extensive homologies with retroviridae-related genes was detected. Among the biological processes that were affected in diseased clams, the synaptic transmission process was the most represented. To deepen this result, a new sampling was carried out and the transcription level of genes involved in synaptic transmission was determined in healthy and diseased clams but also in clams with no visible sign of pathology but located at the surface of the sediment. Our findings suggest that muscle atrophy is a latter sign of the pathology and that nervous system could be instead a primary target of the BMD agent.

Virulence of a chimeric recombinant infectious haematopoietic necrosis virus expressing the spring viraemia of carp virus glycoprotein in salmonid and cyprinid fish

Infectious haematopoietic necrosis virus (IHNV) and spring viraemia of carp virus (SVCV) are both rhabdoviruses of fish, listed as notifiable disease agents by the World Organization for Animal Health. Recombinant rhabdoviruses with heterologous gene substitutions have been engineered to study genetic determinants and assess the potential of these recombinant viruses for vaccine development. A recombinant IHNV (rIHNV), containing the full-length genome of a European IHNV strain, was modified by deleting the glycoprotein (G) gene and replacing it with a European SVCV G-gene to make the rIHNV-Gsvcv. The chimeric rIHNV-Gsvcv level of virulence in rainbow trout, common carp and koi was assessed, and its ability to induce a protective immune response in surviving koi against wild-type SVCV infection was tested. The rIHNV-Gsvcv infection of trout led to high mortality, ranging from 78% to 92.5%, after immersion. In contrast, no deaths occurred in juvenile common carp after infection with rIHNV-Gsvcv by either immersion or intraperitoneal (IP) injection. Similarly, koi infected with rIHNV-Gsvcv via IP injection had little to no mortality (≤9%). Koi that survived initial infection with a high dose of recombinant virus rIHNV-Gsvcv were protected against a virulent SVCV challenge resulting in a high relative per cent survival of 82.5%.

[Triggers of bulimia and compulsion attacks: validation of the "Start" questionnaire]

AIM

There are few published studies on the triggers of binge eating in anorexia nervosa of binge/purging subtype (BPAN), bulimia nervosa (BN) and binge eating disorder (BED).

PATIENTS AND METHODS

We validated in 29 patients (10 BPAN, 10 BN and 9 BED) the perspicuity, the clarity and the intra- (doubles) and inter- (test-retest) reproducibility of a 24-item Start questionnaire on the triggers of binge eating. Then the Start questionnaire was administered to 176 patients (65 BPAN, 62 BN and 59 BED patients) being 27.5+9.1 yr old, having 15+9 binge eating (BE) episodes/week, with a mean binge duration of 1 hr 36min (+ 38min)/day.

RESULTS

BE episodes occurred mainly during the second part of the day: afternoon after work (67% of the patients), "tea" time (55%), evening after dinner (42%) and at night (22%). The principal place for BE episodes was at home (96%). The BED patients avoided binges at the parents' home (89%) more often than the BPAN (62%, P<0.02). The binges occurred mainly in the living room (44%), in the kitchen (43%), and less in the bedroom (31%). Hunger pangs seemed to be a trigger of binges in 31% of the patients, and a stronger trigger in BED (42%) than in the BPAN and BN patients (24%; P=0.04). Binge eating episodes could occur despite a high satiety level (just after lunch or dinner) in 29% of the BN and in 16% of the BED patients (P<0.02). Concerning food, the major triggers were high energy-density food (77%) and comfort food (60%), such as chocolate, cakes, bread and pasta. The food consumed for binge episodes (in-binge food) was more often a strong trigger than the other food (not used for binges): olfaction (19% versus 10%), sight (52% versus 25%) and placing in the mouth (71% versus 26%; P<0.02 for all, in the 3 groups). Being tired could be a strong trigger in 37% of the patients, but "being aroused" in the other 38 % of the patients. Stressful events (65%), anxiety (74%), "being under pressure" or irritated (51% and 55%) were of course major triggers in a majority of the patients, as well as sadness (61%), feeling of powerlessness (62%), inefficiency (73%) and depressive state (71%). Flashback from traumatism (sexual trauma in 17% of the patients) was a strong trigger of binges more often in BPAN and BED (44%) than in BN (23%; P<0.05). The binge eating was painful (and "not at all a pleasure") in 69% of the patients, but could also be a relaxing behavior in 31% of the patients, more often in the BED (43%) than in the BPAN patients (20%; P<0.05). The binge eating behavior was quoted as obsessive in 63% of BPAN, 92% of BN and only 34% of BED patients (P<0.001). The patients said that they were unable to avoid the binge (76% of the patients), more often in BPAN and BN than in BED patients (P<0.01). As a whole, 62% of BPAN, 89% of BN and only 4 % of BED patients (P<0.05) were unable to avoid purging (vomiting). In 12% of the cases, there was a pleasure felt when binging. For the other patients, shame, filth and incapacity were the feelings related to binges in 58% of the BPAN, 45% of BN and 43% of BED patients (P<0.04). The global score of addiction (zero=not addicted, 10=very addicted) was 8.56+1.2 in BPAN, 8.42+1.5 in BN and 6.74+1.1 in BED patients (NS between BPAN and BN; P<0.01 between BPAN and BN on the one hand and BED on the other).

CONCLUSION

The present study has demonstrated the usefulness of the Start questionnaire. It also evidences the key role of intrinsic factors, both metabolic and emotional, as strong triggers for binge eating episodes in BPAN, BN and BED. It has also demonstrated the role of environmental determinants.

Reverse genetics on fish rhabdoviruses: tools to study the pathogenesis of fish rhabdoviruses

Rhabdoviruses, mainly in rainbow trout, are among the most devastating viruses for worldwide aquaculture. To date no effective treatments to fight against these viruses are available. During the past years, several approaches to develop efficient vaccines have been undertaken such as the use of immunogenic recombinant viral proteins, naked DNA or inactivated viruses. However, although these vaccines have been proven to be very effective on a small scale, they have never been used in the field because the vaccines would have to be injected into thousands of yearling trouts. The only alternative to injection consists of the development of attenuated live vaccines that can be administrated to trouts by bath immersion. Reverse genetics on trout rhabdoviruses offer the possibility of recovering a series of live recombinant viruses in which the viral genome has been irreversibly modified to generate cost-effective live, safe vaccines.

Recovery of NV knockout infectious hematopoietic necrosis virus expressing foreign genes

Infectious hematopoietic necrosis virus (IHNV) is a Novirhabdovirus and is the causative agent of a devastating acute, lethal disease in wild and farmed rainbow trout. The virus is enzootic throughout western North America and has spread to Asia and Europe. A full-length cDNA of the IHNV antigenome (pIHNV-Pst) was assembled from subgenomic overlapping cDNA fragments and cloned in a transcription plasmid between the T7 RNA polymerase promoter and the autocatalytic hepatitis delta virus ribozyme. Recombinant IHNV (rIHNV) was recovered from fish cells at 14 degrees C, following infection with a recombinant vaccinia virus expressing the T7 RNA polymerase (vTF7-3) and cotransfection of pIHNV-Pst together with plasmids encoding the nucleoprotein N (pT7-N), the phosphoprotein P (pT7-P), the RNA polymerase L (pT7-L), and the nonvirion protein NV (pT7-NV). When pT7-N and pT7-NV were omitted, rIHNV was also recovered, although less efficiently. Incidental mutations introduced in pIHNV-Pst were all present in the rIHNV genome; however, a targeted mutation located in the L gene was eliminated from the recombinant genome by homologous recombination with the added pT7-L expression plasmid. To investigate the role of NV protein in virus replication, the pIHNV-Pst construct was engineered such that the entire NV open reading frame was deleted and replaced by the genes encoding green fluorescent protein or chloramphenicol acetyltransferase. The successful recovery of recombinant virus expressing foreign genes instead of the NV gene demonstrated that the NV protein was not absolutely required for viral replication in cell cultures, although its presence greatly improves virus growth. The ability to generate rIHNV from cDNA provides the basis to manipulate the genome in order to engineer new live viral vaccine strains.

Rainbow trout sleeping disease virus is an atypical alphavirus

Sleeping disease (SD) is currently a matter of concern for salmonid fish farmers in most parts of the world. A viral etiology of SD has recently been suspected, since virus-like particles have been observed in infected rainbow trout cells. In salmonid-derived cell lines, the maximal rate of virus production was observed at 10 degrees C, while little virus was produced at 14 degrees C. Through biochemical, physicochemical, and morphological studies, SD virus (SDV) was shown to be an enveloped virus of roughly 60 nm in diameter. The genome consists of 12 kb of RNA, with the appearance of a 26S subgenomic RNA during the time course of SDV replication. The screening of a random-primed cDNA library constructed from the genomic RNA of semipurified virions facilitated the identification of a specific SDV cDNA clone having an open reading frame related to the alphavirus E2 glycoproteins. To extend the comparison between SDV structural proteins and the alphavirus protein counterparts, the nucleotide sequence of the total 4.1-kb subgenomic RNA has been determined. The 26S RNA encodes a 1,324-amino-acid polyprotein exhibiting typical alphavirus structural protein organization. SDV structural proteins showed several remarkable features compared to other alphaviruses: (i) unusually large individual proteins, (ii) very low homology (ranging from 30 to 34%) (iii) an unglycosylated E3 protein, and (iv) and E1 fusion domain sharing mutations implicated in the pH threshold. Although phylogenetically related to the Semliki Forest virus group of alphaviruses, SDV should be considered an atypical member, able to naturally replicate in lower vertebrates.

Partial mapping and sequencing of a fish iridovirus genome reveals genes homologous to the frog virus 3 p31, p40 and human eIF2alpha

Iridovirus-like pathogens have been recognized as a cause of serious systemic diseases among feral, cultured and ornamental fish in the recent years. Mortalities of fish due to systemic iridovirus infection reaching 30-100% were observed in Europe, Australia, Japan and Thailand. Up to now, the molecular biology of these important pathogens has been poorly documented. To get better insights on the genomic organization of these piscine iridoviruses, we have constructed a cosmid viral DNA library from the epizootic hematopoietic necrosis virus (EHNV). Two recombinant cosmids (Cos7 and Cos12) have been selected for systematic sequencing. Cos7 and 12 are localized side by side along the genome and cover the 2/3 part of the total EHNV genome which has been estimated to be approximately 101.47 kb in length. Thirty five kilobase pairs (kbps) from Cos7 and 10 kbps from Cos12 have been determined. Sequence analysis revealed open reading frames (ORF) sharing homologies with sequences from the Frog virus 3 such as the p31 and p40 proteins. Among the others identified ORFs, some of them presented homologies with known protein sequences, such as the human eIF2alpha protein, and some did not show any significant homologies with sequences available in the databases. But, none were related to Lymphocystis virus, a member of the Iridoviridae family, for which the full genome nucleotide sequence has been determined.

An RNA-binding domain in the viral haemorrhagic septicaemia virus nucleoprotein

The gene encoding the nucleoprotein (N) and PCR-derived subfragments from viral haemorrhagic septicaemia virus (VHSV), a salmonid rhabdovirus, were overexpressed in Escherichia coli BL21(DE3) transformed by recombinant expression vector pET-14b containing N and PCR-generated sub-fragment cDNAs under the control of the T7 RNA polymerase promoter. Following induction with IPTG, recombinant His-tagged proteins were expressed, purified by affinity metal chelation chromatography under denaturing conditions and renatured. Protein blots were hybridized with various radiolabelled nucleic acid probes. Results obtained using genomic or messenger virus RNA as a probe indicated that the middle part of N was possibly an RNA-binding domain. To confirm this observation, two more accurate approaches were undertaken: (i) a gel retardation assay of RNA and purified protein complexes was done; and (ii) RNA-protein complexes were cross-linked by UV light and analysed on a denaturing polyacrylamide gel. All these experiments led us to conclude that the middle part of N is the domain which interacts with RNA, despite the absence of homology with known consensus amino acid sequences of other RNA-binding proteins.

Cloning, sequencing and expression of a cDNA encoding an antigen from the Myxosporean parasite causing the proliferative kidney disease of salmonid fish

A pool of monoclonal antibodies (MAbs) raised against the unknown organism causing the proliferative kidney disease of salmonid fish (PKX) has been used to screen a cDNA expression library constructed from poly (A+) RNA extracted from PKX infected kidney. Four immunopositive lambda ZapII recombinant phages were selected. Sequencing of the cDNAs revealed identical 3' ends. The longest cDNA clone (2652 nucleotides) had an open reading frame (ORF) of 872 amino acids and encoded a protein with a predicted size of 101 kDa (PKX101). Sequence analysis of PKX101 revealed two leucine zipper motifs, a putative transmembrane region and a microbody targeting signal at its C-terminal end. Three cDNA fragments were subcloned in pET-14b expression vector and the ORF verified by an in vitro transcription/translation procedure. Recombinant clones were expressed in Escherichia coli and the antigenicity of fusion proteins was studied by Western blotting using monoclonal antibodies directed against PKX cells and a pool of serum from preimmune or PKX-infected rainbow trout. Western blotting of enriched PKX cell antigen probed with one MAb or with sera from infected trout revealed a single protein with relative mobility of 13 kDa (PKX13). This discrepancy between PKX101 and PKX13 observed in Western blot suggests post-translational modifications of the full-length PKX antigen.

Expression of the major capsid protein VP6 of group C rotavirus and synthesis of chimeric single-shelled particles by using recombinant baculoviruses

VP6 of group C (Cowden strain) rotavirus was expressed in the baculovirus system. The recombinant protein, expressed to a high level in insect cells, was purified by ion-exchange chromatography. The purified protein was proven to be trimeric. The effect of pH on the trimer's stability was investigated. Coexpression of VP6 from group A (bovine strain RF) and VP6 from group C in the baculovirus system did not result in the formation of chimeric trimers. Coexpression of VP2 from group A rotavirus (bovine strain RF) and VP6 from group C in the baculovirus system led to the formation of chimeric, empty, single-shelled particles. These results demonstrate conservation in the domains necessary for binding to VP2 in different serogroups of VP6. The locations of the domains involved in trimerization and in the interaction with VP2 are discussed.