Molecular characterization of two isoforms of defensin from hemocytes of the oyster Crassostrea gigas

Antimicrobial peptides (AMPs) are important components of the host innate immune response against microbial invasion. We previously characterized the first AMP from an oyster, a defensin, that was shown to be continuously expressed in the mantle of Crassostrea gigas. In this study, we report the cDNA cloning of two new isoforms of the defensin AMP family (Cg-defh1 and Cg-defh2) from the hemocytes of the oyster. The deduced amino acid sequences reveal two peptides of 73 amino acid residues with a mature portion consisting of 43 amino acid residues. Cg-Defh1 and Cg-Defh2 share 86% amino acid identity and belong to the "arthropod-molluscs defensin family". qRT-PCR analyses indicate that Cg-defh2 is continuously expressed in the hemocytes of C. gigas. In addition, after a bacterial challenge, the level of Cg-defh2 transcripts decreases dramatically in the circulating hemocyte population and this decrease can be correlated with an increase of Cg-defh2 transcripts in the gill and the mantle tissue, suggesting a possible migration of the hemocytes expressing Cg-defh2 towards the tissues implicated in the first defense barrier of the oyster. These results would suggest an important role of Cg-Defh2 in the oyster response to a microbial challenge.

A sandwich enzyme linked immunosorbent assay (S-ELISA) for detection of MrNV in the giant freshwater prawn, Macrobrachium rosenbergii (de Man)

A sandwich enzyme-linked immunosorbent assay (S-ELISA) was developed to improve diagnosis of white tail disease of the giant freshwater prawn, Macrobrachium rosenbergii, caused by the nodavirus, MrNV. Polyclonal antibodies were produced by immunization of Balb/C mice using a purified suspension of the virus and IgG anti-MrNV were purified from ascitic fluid. A sandwich method was successfully developed, coating first with unlabelled antibody and detecting trapped antigens with a second biotinylated antibody. Reaction was demonstrated using an avidin-peroxidase conjugate. Tissue extracts from M. rosenbergii infected with MrNV or purified viral extracts (control) were successfully identified in an individual ELISA, thus confirming the validity of the method. This S-ELISA should be the technique of choice for epidemiological studies of this disease and is a rapid and inexpensive assay with high specificity and sensitivity.

Protease inhibitors and haemagglutinins associated with resistance to the protozoan parasite, Perkinsus marinus, in the Pacific oyster, Crassostrea gigas

Perkinsus marinus is a protozoan responsible for dramatic mortality in the Eastern oyster, Crassostrea virginica, but not in the Pacific oyster, C. gigas. To understand the host-parasite relationship, we inoculated P. marinus trophozoites into the shell cavity of C. gigas and measured, over 2 months, (i) intensity of infection, (ii) protease inhibitory activities against P. marinus proteases and against bovine z-chymotrypsin, (iii) plasma haemagglutinin titre, (iv) plasma protein concentration, (v) plasma lysozyme activity and (vi) total haemocyte count. We observed that the highest protease inhibitory activities and haemagglutinin titres (3-10 days post-challenge) preceded parasite elimination (initiated 7 days post-challenge). In contrast, plasma protein concentration, lysozyme activity and total haemocyte count showed no significant modification following the challenge. It is hypothesized that the capacity of C. gigas to increase its protease inhibitors represents the key event in resistance to parasite infection by neutralizing the proteases secreted by P. marinus, thus preserving the oyster haemagglutinins from degradation. Such haemagglutinins will be ready to act as opsonins stimulating phagocytosis of parasites.

Differential distribution and defence involvement of antimicrobial peptides in mussel

In previous papers, we characterised 3 types of 4-kDa, cysteine-rich, cationic antimicrobial peptides: MGDs (for Mytilus galloprovincialis defensins), mytilins and myticins, which are abundant in the mussel hemocytes. In the present work, we revealed a differential distribution of the cells expressing the different genes. In addition, using confocal and electron microscopy, we confirmed that defensins and mytilins were partially located in different sub-types of circulating hemocytes although the peptides can be located in the same cell, and even in the same granule. We also demonstrated that mytilins exert their microbicidal effect within the cells through the process of phagosome-mytilin granule fusion leading to the co-location of ingested bacteria and mytilins.

In vitro production of superoxide and nitric oxide (as nitrite and nitrate) by Mytilus galloprovincialis haemocytes upon incubation with PMA or laminarin or during yeast phagocytosis

The phagocytic process is one of the most important elements of the self-defence system in mammals as well as in molluscs. In mammalian phagocytes, superoxide participates in the innate defence system by combining with nitric oxide to generate peroxynitrite, a strong oxidant that possesses highly cytotoxic properties against bacteria. To evidence a role of nitric oxide in the self-defence system of the marine bivalve Mytilus galloprovincialis similar to the role observed in the mammalian defence system, we measured the generation of superoxide and nitrite/nitrate (the stable end products of nitric oxide) upon in vitro stimulation of M. galloprovincialis haemocytes with PMA, laminarin, LPS and by phagocytosis of Saccharomyces cerevisiae (yeast cells). We show that stimulation with PMA, laminarin and yeast cell phagocytosis promotes superoxide and nitrite/nitrate generation from M. galloprovincialis haemocytes. Inhibitors of NADPH oxidase and inhibitors of NO synthase decreased the nitrite/nitrate levels generated by M. galloprovincialis haemocytes showing that both NADPH oxidase and NO synthase pathways are involved in the self-defence system of M. galloprovincialis.

Ribosomal DNA sequences of Glugea anomala, G. stephani, G. americanus and Spraguea lophii (Microsporidia): phylogenetic reconstruction

The microsporidian species Glugea anomala, G. stephani, G. americanus and Spraguea lophii were compared by using sequence data derived from their small subunit rDNA genes which were amplified by polymerase chain reaction and directly sequenced. These sequence data and published data of G. atherinae were analyzed and were used to infer a phylogenetic tree. The 5 microsporidian fish parasites appeared to be closely related. The higher sequence similarities demonstrated among G. anomala, G. stephani and G. atherinae suggest that these 3 parasites are in fact only 1 species of Glugea. Moreover, the higher sequence similarities between S. lophii and G. americanus support the transfer of the latter Glugea species into the genus Spraguea.

Insulin during the early postembryonic development of the gilt-head sea bream, Sparus aurata: ultrastructural, immunohistochemical, and biochemical studies

Insulin was sought during the early postembryonic development of gilt-head sea bream, Sparus aurata, using ultrastructural, immunohistochemical and biochemical techniques. The endocrine pancreas appeared at hatching (Day 0) as a single cluster of morphologically similar cells. Secretory granules formed from Day 1 onwards but the cells could only be identified as insulin-producing B cells at the end of the endotrophic period (Day 3-Day 4). Insulin-immunoreactive cells were detected in the pancreatic primordium from hatching onwards and their number increased after the end of the endo-exotrophic period. Early insulin production was also found using an ELISA method on homogenates of prelarvae and larvae. Insulin levels were fairly high during the endotrophic period, decreased strongly at mouth opening, and then increased at the end of the endo-exocrine period. The origin and role of the large amount of hormone detected during the strictly endotrophic phase of ontogenesis are discussed in light of data on other vertebrates.

Identification and phylogenetic relationships of microsporidia by riboprinting

The SSUrDNA and the ITS of different microsporidia from eight fishes, four insects and a shrimp were amplified and digested with restriction enzymes. The generated riboprints suggest a close evolutionary relationship between Glugea americanus and Spraguea lophii suggesting that Glugea americanus should be renamed Spraguea americanus and that the tissue infected and host origin should be considered of greater taxonomic importance for defining a genus than previously considered. Phylogenetic analysis of the riboprints demonstrates an unidentified microsporidium from a bumper fish (Chloroscombrus chrysurus) is related although not identical to Microgemma ovoidea, a parasite from red band fish. We were also able to distinguish between Glugea anomala and Glugea atherinae and Glugea stephani but were not able to differenciate among the latter two. Insects isolates, Nosema costelytrae, N. bombycis, N. trichoplusiae, Nosema sp. and a shrimp isolate, Agmasoma penaei, are not related to the fish isolates.

Development, characterization and future prospects of monoclonal antibodies against spores of Glugea atherinae (protozoa-microsporidia-fish parasites)

Monoclonal antibodies against spores of Glugea atherinae were obtained after lymphocytic hybridization made from immunized mouse splenocytes. Screening using an indirect enzyme linked immunosorbent assay (ELISA), revealed seven monoclonal antibodies with an intense but variable reaction with the spores of fish microsporidia, and a moderate reaction with those of an insect microsporidium (Nosema sp.). The reaction was weaker with spores of Encephalitozoon intestinalis found in HIV+ patients. FITC and Dot Blot confirmed the majority of these results. After biotinylation of the seven antibodies, inhibition tests allowed the localization of two different recognition domains on the spores of Glugea atherinae. The multiple antigenic determinants and their probable polysaccharide nature seem to be in accord with the class IgM of the antibodies produced. This work confirms the potential of these antibodies for microsporidian taxonomy and diagnosis, especially the use of Mabs 12F9 and 12H5 for detection of spores in stools of HIV+ patients.

Use of cross-reactive antigens of the microsporidian Glugea atherinae for the possible detection of Enterocytozoon bieneusi by western blot

The microsporidia Enterocytozoon bieneusi is reported in 10-30% of those infected with the human immunodeficiency virus. The parasite appears to be a cause of gastralgia, malabsorption, and diarrhea. A Western blot technique using another microsporidian species, Glugea atherinae, has demonstrated an antigenic similarity between this parasite and E. bieneusi. Preliminary results show the variability of the antigenic profiles obtained from the sera of immunodeficient patients infected with E. bieneusi and also of the cross-reactivity to Glugea sp. antigens of some sera from patients with cryptosporidiosis. The origin of this cross-reactivity is undetermined. The possibility of coinfection with undetected microsporidia is not excluded. These results raise questions concerning the interpretation of serologic data and of the potential immunodiagnostic value of microsporidian antigens.

Direct, simplified, and sensitive assay of angiotensin II in plasma extracts performed with a high-affinity monoclonal antibody

A very simple, fast, and sensitive RIA of angiotensin (Ang) II has been developed, based on a monoclonal antibody with high affinity and specificity, making possible the direct measurement of circulating Ang II in human plasma after solid-phase extraction. The purified monoclonal antibody 4D8 has an association constant of 1.3 x 10(11) L/mol with Ang II and a cross-reactivity of < 1% for Ang I. The assay can detect as little as 0.8 fmol of Ang II in 2 mL of plasma and is not influenced by the presence of Ang I. Analytical recoveries between 112% and 116% were obtained for Ang II added to human plasma at physiological concentrations. Comparison of the RIA with a reversed-phase, high-performance liquid chromatographic method followed by RIA to measure Ang II in human plasma samples from normal and hypertensive subjects--and from normotensive subjects before and after an acute inhibition of angiotensin-converting enzyme with captopril (50 mg)--showed a high degree of correlation (r2 = 0.93) between the two methods.

Direct, Simplified, and Sensitive Assay of Angiotensin II in Plasma Extracts Performed with a High-Affinity Monoclonal Antibody

A very simple, fast, and sensitive RIA of angiotensin (Ang) II has been developed, based on a monoclonal antibody with high affinity and specificity, making possible the direct measurement of circulating Ang II in human plasma after solid-phase extraction. The purified monoclonal antibody 4D8 has an association constant of 1.3 x 10(11) L/mol with Ang II and a cross-reactivity of &lt; 1% for Ang I. The assay can detect as little as 0.8 fmol of Ang II in 2 mL of plasma and is not influenced by the presence of Ang I. Analytical recoveries between 112% and 116% were obtained for Ang II added to human plasma at physiological concentrations. Comparison of the RIA with a reversed-phase, high-performance liquid chromatographic method followed by RIA to measure Ang II in human plasma samples from normal and hypertensive subjects--and from normotensive subjects before and after an acute inhibition of angiotensin-converting enzyme with captopril (50 mg)--showed a high degree of correlation (r2 = 0.93) between the two methods.

Highly sensitive immunoassay for direct diagnosis of viral hemorrhagic septicemia which uses antinucleocapsid monoclonal antibodies

An antigen capture enzyme-linked immunosorbent assay (ELISA) based on the detection of the viral nucleocapsid (anti-N system) was developed for the diagnosis of viral hemorrhagic septicemia. Four monoclonal antibodies directed against the viral nucleocapsid were produced; they all recognized the four viral hemorrhagic septicemia virus (VHSV) serotypes. Three of these monoclonal antibodies were used in a new antigen capture ELISA. The efficiency of the anti-N system in detecting purified and crude viruses as well as the virus in infected-organ extracts and infected blood was compared with that of a recently described antigen capture ELISA based on the detection of viral envelope glycoprotein Gp (anti-G system). For the detection of purified virus, the anti-N system was found to be as sensitive as the anti-G system (detection limit, 1 ng of total viral protein per ml), but the anti-N system was much more sensitive than the anti-G system for the detection of crude VHSV I (detection limits, 1 x 10(4) PFU/ml versus 5 x 10(5) PFU/ml). In organ extracts, VHSV I could be detected by both systems 3 days postinfection. The signal for the assay of VHSV I in blood 24 h postinfection was higher with the anti-N system than the anti-G system. Furthermore, VHSV I could be detected in 80% of the brain samples of surviving trout by the anti-N system and also by the anti-G system, but with a lower signal. In conclusion, we have developed a highly sensitive immunoassay for VHSV I that is more rapid and easier to perform than the currently used plaque assay.

[Water transfer in relation to the salinity of the medium in two isopods Cymothoidae: Meinertia oestroides (Risso, 1862) and Anilocra physodes (L., 1758) (parasites of marine fishes)]

Meinertia oestroides and Anilocra physodes (Isopoda Cymothoidae) respectively buccal and skin parasites of the teleostean Fish Boops boops are isosmotic with the surrounding medium in sea water (SW), hyperosmotic and hyperionic in diluted media. The drinking rate of meinertia is 0.73 microliter in SW and 5.30 microliter h-1 g-1 wet weight in 5/10 SW; Anilocra shows 0.31 microliter in SW and 0.21 microliter h-1 g-1 wet weight in 6/10 SW. The distribution space of [51Cr] EDTA in Meinertia reaches 32.7% in SW and 28.9% of wet weight in 5/10 SW; Anilocra indicates 29.6% in full SW and 19.2% of wet weight in 6/10 SW. The rate of primary urine production in Meineria evaluated from the biological period of [51Cr] EDTA is 130 mg in SW and 338 mg 24 h-1 g-1 wet weight in 6/10 SW. The area of pleopoda is 826 mm2 for Anilocra, 336 mm2 for Meinertia and 277 mm2/g wet weight for Emetha audouini (another buccal parasite); 92.6% for Anilocra, 84.1% for Meinertia and 81.8% for Emetha of the apparent water diffusion outflux take place through the pleopoda. The apparent permeability diffusion coefficient Pd in SW is 1.63 x 10(-4) cm/sec for Anilocra, 2.80 x 10(-4) cm/sec for Meinertia and 3.31 x 10(-4) cm/sec for Emetha. In dilute media Pd is 1.30 x 10(-4) cm/sec for Anilocra and 3.44 x 10(-4) cm/sec in Meinertia. The results are compared with those already obtained for other non parasitic Crustaceans and according to the parasitic localization of the species above mentionned. An hypothesis concerning the mechanisms of feeding (hameatophgia) is proposed. The accuracy of results is discussed.

[Metazoan parasites of Boops boops (Linnaeus, 1758) (Teleostean Sparidae) in the "Golfe du Lion", faunistic and ecology (author's transl)]

A global study of the Metazoan parasites of Boops boops (L., 1758) have been made in the "golfe du Lion". Fourteen different species (eight Platyhelmintha, one Nematoda and five Crustacea) have been inventorized. Their respective localisation on the hosts, globals and specifics corresponding prevalences as well as their variations according to the size of the fish, and their abundance have been precised. Parasitics associations have also been examined.

[Influence of the cymothoid isopods Meinertia oestroides, Meinertia parallela, and Anilocra physodes (Crustacea; parasites of fish) on the growth of hosts, Boops boops and Pagellus erythrinus (Sparidae) (author's transl)]

Studies of weight-size (W = aLb) and growth (L = aT + b) in fish (Boops boops and Pagellus erythrinus), potential hosts of some Cymothoid isopods (Meinertia oestroides, Meinertia parallela, and Anilocra physodes) have been performed. Infested fishes show a slight decrease in weight compared to normal fish. Cymothoid do not exert a significant influence on the weight-size ratio; on the other hand, a delay in growth does occur.

[Ecophysiological study on the parasitic action of Cymothoids (author's transl)]

An ecophysiological study on certain parasitisms by Cymothoids allows the elucidation of the following points: --occurrence of oesophagien-side glands producing an anticoagulant effect on the blood of host, the absorption and metabolism of haemoglobin derivatives (hematin and iron) are performed by the hepatopancreas; --existence of immunological reactions between host and Cymothoids; --existence of biochemical, histological, haemotological and biometrical variations among fishes infected by these parasites.

[Degeneration of the tongue of Boops [(Boops boops L., 1758) (Teleost, Sparidae)] parasitized by Meinertia oestroides (Risso, 1826) (Isopoda, Flabellifera, Cymothoidae) (author's transl)]

Host fishes (Boops boops) parasitized by the cymothoid isopod Meinertia oestroides show an atrophied tonuge: its length and its initial weight can decrease of about 50%. These morphological variations are connected with deep histological alterations, such as: A more or less important vanishing of epidermis. A disorganization of the connective tissue, by numerous invading blood cells. A total vanishing of cargilage and a partial vanishing of bone, resulting from the lysis of their own fundamental substance.

[Influence of cymothoidae (Crustacea, Isopoda, Flabellifera) on some hematological constants of the host-fishes (author's transl)]

Some hematological constants (number of erythrocytes--hemaglobin rate--hematocrit--mean blood corpuscule volume--mean corpuscular hemoglobin concentration--mean corpuscular hemoglobin) are studied in non-parasitized and parasitized Teleost fishes (parasites are Cymothoid Isopods). The parasitized fishes show an anaemia, resulting from a decreasing number of erythrocytes in circulation. The spleen undergoes a hypertrophy and a hypervascularization.

[Tissular alterations and defence reactions in cymothoids parasited teleosteans (Crustacea - Isopoda - blood sucking) (author's transl)]

Some tissual alterations of the parasitic microbiotope are shown in fishes harbouring Cymothoidae (blood-sucking Isopods). These alterations consist mainly in a hypertrophied epidermis and a deeply disturbed conjunctive tissue; moreover, it can be observed an important production of mucus on the tegument surface and a rush of blood cells (lymphocytes, eosenophilic granulated cells) and of cells of histiocytary origin (giant multinucleated cells).

[Free amino acids in sera of Cymothoidae (crustacean, isopods, parasites of fishes) and some teleosts]

The free amino-acid composition of the sera of 4 species of Isopods Cymothoidae (Meinertia oestroides, Meinertia parallela, Emetha audouini, Anilocra physodes) are very similar, and present the same characteristics, both quantitatively and qualitatively, as those of free marine Isopods of the family Sphaeromatidae and Idoteidae. Five amino acids are preponderant (serin, prolin, glycin, alanin and taurin). The total concentration is relatively high (154.6-356.4 mg/100 ml) with respect to Decapods. In the parasites studied so far, the free amino-acid pattern (except prolin) is rather like that of the Teleost Fishes, whether they are potential hosts of Cymothoidae or not. The free amino-acid concentration of the blood of the Fishes does not seem to be impaired by the Cymothoidae parasitism.

[About a substance with antithrombinic activity, found in the latero-oesophageal glands of Meinertia oestroides (Risso, 1826) (Isopoda, Flabellifera, Cymothoidae; parasite of fishes) (author's transl)]

An anticlotting factor was found recently in the cephalothoracic latero-oesophageal glands (G.L.O.) of Cymothoid Isopods (blood-sucking fishparasites). This substance is efficient on the blood of hosts such as Boops boops (L.), and also on the human plasma. The way of action and the chemical kind of this factor were investigated: Plasmatic coagulation-tests (Howell, Quick, Cephalin-kaolin, Stypven, Stypven-cephalin, Thrombin and Thrombin coagulase times) were realized on citrated plasmas of Boops and man; enzymatic activities of latero-esophageal glands and hepatopancreas of Meinertia oestroides (Risso, 1826) were also studied. Our results show that the anticlotting action of G.L.O. extracts proceeds from an anti-thrombinic factor, certainly carbohydrate-like as heparin.