Grass carp which survive Dactylogyrus ctenopharyngodonid infection also gain partial immunity against Ichthyophthirius multifiliis

Dactylogyrus ctenopharyngodonid and Ichthyophthirius multifiliis are 2 important ectoparasites of fish. Both parasites can induce an immune response in fish that leads to a decrease in parasitic infection intensity and the development of resistance against parasitic reinfection. The present study evaluated whether grass carp Ctenopharyngodon idella that survived a D. ctenopharyngodonid infection could develop immunity against infection by D. ctenopharyngodonid and I. multifiliis. The results demonstrated that when grass carp were infected with D. ctenopharyngodonid, the number of red blood cells and the percentages of thrombocytes, monocytes, and neutrophils in the white blood cells increased significantly in the early stage of infection. The percentage of lymphocytes increased over time following parasitic infection. The mean infection intensity of D. ctenopharyngodonid decreased to 0 on Day 28. The activities of serum acid phosphatase, alkaline phosphatase, lysozyme, and superoxide dismutase increased significantly after D. ctenopharyngodonid infection. In addition, the grass carp that survived a previous D. ctenopharyngodonid infection could completely resist D. ctenopharyngodonid reinfection and partially resist I. multifiliis infection.

Molecular identification and expression analysis of TLR5M and TLR5S from orange-spotted grouper (Epinepheluscoioides)

Toll-like receptor 5 (TLR5) is an important receptor that interacts with bacterial flagellin and regulates host immune response in mammal. Recent studies demonstrate that piscine contains two types of TLR5, namely membrane form of TLR5 (TLR5M) and soluble form of TLR5 (TLR5S), and both of which perform crucial role in flagellin response. In the present study, a TLR5M and a TLR5S sequence was cloned from orange-spotted grouper (Epinepheluscoioides), and their ORFs are respectively 2466 bp (821 aas) and 1935 bp (644 aas). EcTLR5M has the typical TLR structure of a LRR domain, a transmembrane region and a TIR domain, while EcTLR5S only contains a LRR domain like other species' TLR5S. Both molecules have 23 LRR motifs, a LRR-NT and a LRR-CT in the LRR domain, similar to those of other species. Phylogenetic and sequence alignment indicated that both EcTLR5s respectively displayed closer relationship and higher sequence identity with those in other fish species. In healthy grouper, EcTLR5M was highly expressed in the skin, head kidney and spleen, while EcTLR5S was mainly detected in the liver. Ciliate Cryptocaryon irritans infection could significantly up-regulate the expression level of EcTLR5s in the gill and spleen from day 1 to day 3, and higher expression fold change was observed in the spleen. Taken together, the present studies contributed to understanding the function of piscine TLR5M/S and clarify their possible role in fish immune response against ciliate infection.

The expressed TCRβ CDR3 repertoire is dominated by conserved DNA sequences in channel catfish

We analyzed by high-throughput sequencing T cell receptor beta CDR3 repertoires expressed by αβ T cells in outbred channel catfish before and after an immunizing infection with the parasitic protozoan Ichthyophthirius multifiliis. We compared CDR3 repertoires in caudal fin before infection and at three weeks after infection, and in skin, PBL, spleen and head kidney at seven and twenty-one weeks after infection. Public clonotypes with the same CDR3 amino acid sequence were expressed by αβ T cells that underwent clonal expansion following development of immunity. These clonally expanded αβ T cells were primarily located in spleen and skin, which is a site of infection. Although multiple DNA sequences were expected to code for each public clonotype, each public clonotype was predominately coded by an identical CDR3 DNA sequence in combination with the same J gene in all fish. The processes underlying this shared use of CDR3 DNA sequences are not clear.

Analysis of liver and gill miRNAs of Larimichthys crocea against Cryptocryon irritans challenge

The white-spot disease caused by marine ciliate Cryptocryon irritans hindered the sustainable development of large yellow croaker Larimichthys crocea industry. Better understandings about the parasite-host interactions in the molecular level will facilitate the prevention of mass mortality of the L. crocea caused by white-spot disease. MicroRNAs (miRNAs) are a class of small RNA molecules about 20-22 nucleotides which post-transcriptionally regulated many protein-coding genes and involved in many biological processes, especially in host-pathogen responses. In this study, we identified known and novel miRNAs in the gill and liver of L. crocea challenged by C. irritans by high throughput sequencing using Solexa technology. The data were further studied to screen differentially expressed miRNAs, and predict their target genes. The differential expression (p < 0.05) between libraries was observed in 103 miRNAs in liver tissue, among which 65 and 38 were conserved and novel miRNAs, 67 and 36 were up- and down-regulated miRNAs. While in gill tissue, 122 significant differentially expressed miRNAs were identified, among which 83 and 39 were conserved and novel miRNAs, 79 and 43 were up- and down-regulated miRNAs. In addition, these differentially expressed miRNAs target a series of genes which involved in many important biological processes including immune response. Here via deep sequencing, we for the first time characterize L. crocea miRNAs in response to C. irritans challenge, the results should help for better understandings about the immune response of the L. crocea under C. irritans challenge.

Cryptocaryon irritans recombinant proteins as potential antigens for sero-surveillance of cryptocaryonosis

Cryptocaryonosis is a major problem for mariculture, and the absence of suitable sero-surveillance tools for the detection of cryptocaryonosis makes it difficult to screen Cryptocaryon irritans-infected fish, particularly asymptomatic fish. In this study, we proposed a serum-based assay using selected C. irritans proteins to screen infected and asymptomatic fish. Eight highly expressed genes were chosen from an earlier study on C. irritans expressed sequence tags and ciliate glutamine codons were converted to universal glutamine codons. The chemically synthesized C. irritans genes were then expressed in an Escherichia coli expression host under optimized conditions. Five C. irritans proteins were successfully expressed in E. coli and purified by affinity chromatography. These proteins were used as antigens in an enzyme-linked immunosorbent assay (ELISA) to screen sera from experimentally immunized fish and naturally infected fish. Sera from both categories of fish reacted equally well with the expressed C. irritans recombinant proteins as well as with sonicated theronts. This study demonstrated the utility of producing ciliate recombinant proteins in a heterologous expression host. An ELISA was successfully developed to diagnose infected and asymptomatic fish using the recombinant proteins as antigens.

Immobilization antigen vaccine adjuvanted by parasitic heat shock protein 70C confers high protection in fish against cryptocaryonosis

The immobilization antigen (iAg) has been demonstrated as a protective immunogen against Cryptocaryon irritans infection. In this study, C-terminal domain of heat shock protein 70 cloned from C. irritans (Hsp70C) was tested for its immuno-stimulatory effects. The iAg and Hsp70C cDNAs were constructed independently in secretory forms and were encapsulated in chitosan nanoparticles. In the first immunization trial, grouper fingerlings orally intubated with iAg and iAg:Hsp70C presented 96% and 100% relative percent survival (RPS), respectively, after a lethal challenge. In the second trial, both iAg and iAg:Hsp70C groups showed 100% RPS and the skin trophont burden was significantly lowered. The iAg:Hsp70C still provides a significantly high protection of 51% RPS at 49 days post immunization, when an even more serious lethal infection occurs. RT-qPCR results showed that Hsp70C could up-regulate the expression of i) T cell markers: Cluster of Differentiation 8 alpha (CD8α) and CD4, ii) cytokine genes: Interferon gamma (IFNγ), Tumor Necrosis Factor alpha (TNFα) and Interleukin 12 p40 (IL-12/P40), iii) antibody genes: Immunoglobulin M heavy chain (IgMH) and IgTH, and iv) major histocompatibility complex (MHC-I & MHC-II), in the spleen of iAg:Hsp70C group. Furthermore, significantly high levels of iAg-specific IgM was detected in skin mucus which efficiently immobilized live theronts in iAg- and iAg:Hsp70C-immunized fish at 5 weeks post immunization. Hsp70C significantly increased the number of nonspecific CD8(+) skin leucocytes which exerted cytotoxicity against theronts, although cytotoxic activity showed no difference among the various groups. Because of this complementary cooperation of cellular and humoral immune responses, Hsp70C enhances the efficacy of iAg vaccine and constrains C. irritans infection. In view of the severe loss caused by cryptocaryonosis, application of this parasitic vaccine in farmed and ornamental fish, is worthy to be considered.

Antibacterial efficacy of recombinant Siganus oramin L-amino acid oxidase expressed in Pichia pastoris

Siganus oraminl-amino acid oxidase is a novel natural protein (named SR-LAAO) isolated from serum of the rabbitfish (S. oramin), which showed antibacterial activity against both Gram-positive and Gram-negative bacteria and had a lethal effect on the parasites Cryptocaryon irritans, Trypanosoma brucei brucei and Ichthyophthirius multifiliis. In order to test whether recombinant SR-LAAO (rSR-LAAO) produced by the eukaryotic expression system also has antimicrobial activity, the yeast Pichia pastoris was used as the expression host to obtain rSR-LAAO in vitro. Crude rSR-LAAO produced by P. pastoris integrated with the SR-LAAO gene had antibacterial activity against both Gram-positive and Gram-negative bacteria as shown by inhibition zone assay of the antibacterial spectrum on agar plates. The average diameter of the inhibition zone of crude rSR-LAAO against the Gram-positive bacteria Staphylococcus aureus and Streptococcus agalactiae was 1.040 ± 0.045 cm and 1.209 ± 0.085 cm, respectively. For the Gram-negative bacteria Aeromonas sobria, Escherichia coli, Vibrio alginolyticus, Vibrio cholera and Photobacterium damselae subsp. piscicida, the average diameter of inhibition zone was 1.291 ± 0.089 cm, 0.943 ± 0.061 cm, 0.756 ± 0.057 cm, 0.834 ± 0.023 cm and 1.211 ± 0.026 cm, respectively. These results were obtained at the logarithmic growth phase of S. agalactiae and A. sobria cell suspensions after incubation with 0.5 mg/mL crude rSR-LAAO for 24 h. The final bacterial growth rate was decreased significantly. The relative inhibition rate can reach 50% compared to crude products from P. pastoris integrated with an empty vector at the same concentration of protein. The antimicrobial activity of crude rSR-LAAO was likely associated with H2O2 formation, because its inhibition zones were disturbed significantly by catalase. Scanning electron microscopy results showed crude rSR-LAAO-treated bacterial surfaces became rough and particles were attached, cell walls were retracted and cell membranes were ruptured. Together, the results of this study indicated rSR-LAAO from the P. pastoris expression system is a potential antibiotic for application as a therapeutic agent against bacterial diseases.

Characterization of E3 ubiquitin ligase neuregulin receptor degradation protein-1 (Nrdp1) in the large yellow croaker (Larimichthys crocea) and its immune responses to Cryptocaryon irritans

Neuregulin receptor degradation protein-1 (Nrdp1) was recently identified in humans as an important immune factor responding to the challenge of virus, LPS or cytokine. Its role in fish immune defense and whether it is involved in anti-parasite immunity have not been proven yet. In this report, the full-length cDNA sequence and genomic structure of Nrdp1 in the large yellow croaker Larimichthys crocea (LcNrdp1) were identified and characterized. The full-length cDNA of LcNrdp1 was 1248bp, including a 5' untranslated region (UTR) of 32bp, a 3' UTR of 259bp and an open reading frame (ORF) of 937bp, encoding a polypeptide of 318 amino acid residues. The full-length genomic DNA sequence of LcNrdp1 was composed of 2635 nucleotides, including four exons and three introns. The putative LcNrdp1 protein had no signal peptide sequence and contained a characteristic Nrdp1 consensus motif C3HC3D ring finger and a Coiled-coil domain. Phylogenetic analysis showed that Nrdp1 in fish was closer with that in other vertebrates (79%-90% amino acid identity) than in invertebrates and bacteria (27%-65%). In fishes, Nrdp1 in large yellow croaker was closer with that in Takifugu rubripes. The expression profile showed that LcNrdp1 was constitutively expressed in all tested tissues, especially highly expressed in brain, muscle and kidney. Post-infection (PI) with Cryptocaryon irritans, an increased expression of LcNrdp1 was induced in infection sites (skin and gill), whereas in immune organs, the expression of LcNrdp1 was up-regulated in spleen (except the 1st d and 10th d PI) but suppressed in head kidney. These results suggested that LcNrdp1 might play an important immune role in the finfish L. crocea in the defense against the parasite C. irritans.

Molecular characterization and functional analysis of TRAF6 in orange-spotted grouper (Epinephelus coioides)

Tumor necrosis factor receptor (TNFR)-associated factor 6 (TRAF6) is a crucial signal transducer in both the TNFR superfamily and Toll-like receptor/interleukin 1R family. Although significant progress has been made in clarifying the role of TRAF6 in mammals, the function of TRAF6 in fish is still poorly understood. In this study, we cloned the orange-spotted grouper (Epinephelus coioides) TRAF6 (EcTRAF6) cDNA, with an open reading frame of 1713bp encoding 570 amino acids. Sequence analysis indicated that EcTRAF6 contains the four characteristic domains conserved in the TRAF family, including an N-terminal RING finger, two zinc fingers, a coiled-coil domain, and a C-terminal MATH domain. Homology alignment and phylogenetic analysis demonstrated that EcTRAF6 shares high sequence identity with TRAF6 of other fish species. The EcTRAF6 gene contains seven exons and six introns, which is similar to the organization in ayu, but not in the common carp, human, or mouse (six exons and five introns). EcTRAF6 transcripts were broadly expressed in all tissues tested, and increased after infection with Cryptocaryon irritans. Intracellular localization showed EcTRAF6 was distributed mainly in the cytoplasm. Over-expression of wild type (WT) EcTRAF6, truncated forms of EcTRAF6, including ΔZinc finger 2 and ΔMATH, and a mutant of C78A activated NF-κB strongly in HEK293T cells; whereas truncations, including ΔRING, ΔZinc finger 1 and Δcoiled-coiled, and a mutant of K132R induced the activity of NF-κB slightly compared to WT EcTRAF6, implying the latter has a more crucial role in downstream signal transduction. Together, these results suggested EcTRAF6 functions like that of mammals to activate NF-κB, and it might have an important role in host defense against parasitic infections.

Reprint of "fish immunity to scuticociliate parasites"

Some species of scuticociliates (Ciliophora) behave as facultative parasites and produce severe mortalities in cultured fish. Pathogenic scuticociliates can cause surface lesions and can also penetrate inside the body, where they feed on tissue and proliferate in the blood and most internal organs, killing the host in a few days. In this review, we describe the current knowledge on the protective role of fish cellular and humoral immune responses against these parasites. Immune humoral factors, especially complement, are of particular importance in defending fish against these ciliates. However, knowledge about how the fish immune system responds to scuticociliates is scant, and the cellular and molecular events that occur during the response are not known. We also describe the possible mechanisms used by scuticociliates to avoid or resist the defensive reaction of the host. For example, the release of proteases can help parasites enter fish tissues and impair the fish cellular and humoral responses. Several vaccine formulations containing scuticociliates have induced a good antibody response and protection in fish immunized and challenged with homologous strains of particular species. However, protection was not achieved in fish immunized and challenged with heterologous strains, and the antigens involved in protection and the antigenic differences between heterologous strains have not yet been determined.

Siganus oramin recombinant L-amino acid oxidase is lethal to Cryptocaryon irritans

A novel antimicrobial and antiparasitic protein (APP/SR-LAAO) isolated from serum of the rabbitfish (Siganus oramin) was confirmed to be lethal to Cryptocaryon irritans, an important marine parasitic ciliate that causes marine white spot disease in a variety of wild and cultured fish. In this study, a recombinant SR-LAAO (rSR-LAAO) was expressed on a large scale in Escherichia coli Rosetta-gami™(DE3)pLysS cells. rSR-LAAO was expressed as an inactive form in the inclusion bodies. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that after purification, refolding and ultrafiltration, rSR-LAAO had a significantly cytotoxic effect on C. irritans theronts. Using light microscopy, scanning electron microscopy and fluorescence microscopy, we found that theronts rapidly became weakly motile, cilia became detached, cells became rounded, membranes eventually lysed in different cell positions and cytoplasmic contents leaked out of the cell. These results suggested the recombinant SR-LAAO was significantly lethal to C. irritans and the death process of the parasite incubated with rSR-LAAO was remarkably similar compared to the SR-LAAO group as reported earlier.

Fish immunity to scuticociliate parasites

Some species of scuticociliates (Ciliophora) behave as facultative parasites and produce severe mortalities in cultured fish. Pathogenic scuticociliates can cause surface lesions and can also penetrate inside the body, where they feed on tissue and proliferate in the blood and most internal organs, killing the host in a few days. In this review, we describe the current knowledge on the protective role of fish cellular and humoral immune responses against these parasites. Immune humoral factors, especially complement, are of particular importance in defending fish against these ciliates. However, knowledge about how the fish immune system responds to scuticociliates is scant, and the cellular and molecular events that occur during the response are not known. We also describe the possible mechanisms used by scuticociliates to avoid or resist the defensive reaction of the host. For example, the release of proteases can help parasites enter fish tissues and impair the fish cellular and humoral responses. Several vaccine formulations containing scuticociliates have induced a good antibody response and protection in fish immunized and challenged with homologous strains of particular species. However, protection was not achieved in fish immunized and challenged with heterologous strains, and the antigens involved in protection and the antigenic differences between heterologous strains have not yet been determined.

Immune responses and immune-related gene expression profile in orange-spotted grouper after immunization with Cryptocaryon irritans vaccine

In order to elucidate the immune-protective mechanisms of inactivated Cryptocaryon irritans vaccine, different doses of C. irritans theronts were used to immunize orange-spotted grouper (Epinephelus coioides). We measured serum immobilization titer, blood leukocyte respiratory burst activity, serum alternative complement activity, and serum lysozyme activity weekly. In addition, the expression levels of immune-related genes such as interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), major histocompatibility complexes I and II (MHC I and II), and transforming growth factor-β1 (TGF-β1) were determined in spleen and gills. The results showed that the immobilization titer, respiratory burst activity, and alternative complement activity of immunized fish were significantly increased, and the levels of the last two immune parameters in the high-dose vaccine group were significantly higher than in the low-dose vaccine group. Serum lysozyme activity in the high-dose vaccine group was significantly higher than in the PBS control group. Vaccination also regulated host immune-related gene expression. For example, at 2- and 3- weeks post immunization, IL-1β expression in the high-dose vaccine group spleen was significantly increased. At 4-weeks post immunization, the fish were challenged with a lethal dose of parasite, and the survival rates of high-dose vaccine group, low-dose vaccine group, PBS control group, and adjuvant control group were 80%, 40%, 0%, and 10% respectively. These results demonstrate that inactivated C. irritans vaccination improves specific and nonspecific immune responses in fish, enhancing their anti-parasite ability. These effects are vaccine antigen dose-dependent.

B cell memory following infection and challenge of channel catfish with Ichthyophthirius multifiliis

B cell responses in channel catfish to infection with the parasitic ciliate Ichthyophthirius multifiliis were followed for 3 years. High titers of serum IgM antibodies recognizing I. multifiliis immobilization antigens were present 5weeks after immunizing infection, but by 1 year titers were at low or undetectable levels. Two to three years after infection the numbers of antibody secreting cells recognizing immobilization antigens in skin and head kidney of immune fish had decreased to the level found in uninfected controls. Challenge of immune fish showed they remained immune and that the numbers of antibody secreting cells recognizing immobilization antigens increased in skin but not head kidney. This suggests that antigen-specific memory B cells persisted for 3 years after infection and upon challenge differentiated into antibody secreting cells that localized in skin. Our results suggest that humoral immunity in channel catfish is maintained through IgM(+) memory B cells.

Expression profile of immune-related genes in Lates calcarifer infected by Cryptocaryon irritans

Cryptocaryon irritans causes Cyptocaryonosis or white spot disease in a wide range of marine fish including Lates calcarifer (Asian seabass). However, the immune response of this fish to the parasite is still poorly understood. In this study, quantitative polymerase chain reaction (qPCR) was performed to assess the expression profile of immune-related genes in L. calcarifer infected by C. irritans. A total of 21 immune-related genes encoding various functions in the fish immune system were utilized for the qPCR analysis. The experiment was initiated with the infection of juvenile fish by exposure to theronts from 200 C. irritans cysts, and non-infected juvenile fish were used as controls. Spleen, liver, gills and kidney tissues were harvested at three days post-infection from control and infected fish. In addition, organs were also harvested on day-10 post-infection from fish that had been allowed to recover from day-4 up to day-10 post-infection. L. calcarifer exhibited pathological changes on day-3 post-infection with the characteristic presence of white spots on the entire fish body, excessive mucus production and formation of a flap over the fish eye. High quality total RNA was extracted from all tissues and qPCR was performed. The qPCR analysis on the cohort of 21 immune-related genes of the various organs harvested on day-3 post-infection demonstrated that most genes were induced significantly (p < 0.05) in all tissues, particularly liver (11/21 genes) and kidney (11/21). The expression profile demonstrated that induction of the MHC Class IIα gene was the highest compared to the other genes followed by serum amyloid A, CC chemokine and hepcidin-2 precursor genes. In fish that were allowed to recover from the C. irritans infection (10 days post-infection), expression of the immune-related genes was down-regulated to levels similar to the control fish. These results provide insights into the interaction between C. irritans and L. calcarifer and suggest that the innate immune system plays an important role in early defence against parasite infection allowing the fish to eventually recover from the infection.

Cryptocaryon irritans infection induces the acute phase response in Lates calcarifer: a transcriptomic perspective

Cryptocaryoniasis (also known as marine white spot disease) is mediated by Cryptocaryon irritans. This obligate ectoparasitic protozoan infects virtually all marine teleosts, which includes Lates calcarifer, a highly valuable aquaculture species. Little is known about L. calcarifer-C. irritans interactions. This study was undertaken to gain an informative snapshot of the L. calcarifer transcriptomic response over the course of C. irritans infection. An in-house fabricated cDNA microarray slides containing 3872 probes from L. calcarifer liver and spleen cDNA libraries were used as a tool to investigate the response of L. calcarifer to C. irritans infection. Juvenile fish were infected with parasites for four days, and total RNA was extracted from liver tissue, which was harvested daily. We compared the transcriptomes of C. irritans-infected liver to uninfected liver over an infection period of four days; the comparison was used to identify the genes with altered expression levels in response to C. irritans infection. The greatest number of infection-modulated genes was recorded at 2 and 3 days post-infection. These genes were mainly associated with the immune response and were associated in particular with the acute phase response. Acute phase proteins such as hepcidin, C-type lectin and serum amyloid A are among the highly modulated genes. Our results indicate that an induced acute phase response in L. calcarifer toward C. irritans infection is similar to the responses observed in bacterial infections of teleosts. This response demonstrates the importance of first line defenses in teleost innate immune responses against ectoparasite infection.

Molecular cloning of orange-spotted grouper (Epinephelus coioides) TLR21 and expression analysis post Cryptocaryon irritans infection

TLR21, a non-mammalian Toll like receptor, was recently identified in chicken as a pattern recognition receptor of unmethyl-CpG ODN, functionally similar to that of mammalian TLR9. Its role in fish immune defense and whether it is involved in anti-parasite immunity has not yet been proven. In this study, we identified a cDNA sequence encoding orange-spotted grouper Toll-like receptor 21 (EcTLR21), the open reading frame (ORF) was 2937 bp encoding a putative polypeptide of 979 amino acid residues. Some conserved motifs in mammalian TLR9 were also conserved in grouper and other fish species' TLR9 and TLR21. Tissue distribution analysis indicated that EcTLR21 is broadly expressed in all the tissue we tested except muscle. High expression levels were found in the head kidney, trunk kidney, spleen and heart. Post Cryptocaryon irritans infection, TLR21 and TLR9 transcripts were induced at the local infection sites (skin and gill), while suppressed in systemic immune organs (spleen and head kidney), indicating that these two receptors may play a role in host anti-parasitic immune responses.

Effect of a mixed herb-enriched diet on the innate immune response and disease resistance of Paralichthys olivaceus against Philasterides dicentrarchi infection

We investigated the effect of a mixed herb-enriched diet obtained from pomegranate Punica granatum, Dalmatian chrysanthemum Chrysanthemum cinerariaefolium, and mastic-leaved prickly-ash Zanthoxylum schinifolium on innate immune mechanisms (e.g., phagocytosis activity, respiratory burst activity, alternative complement activity, lysozyme activity, and disease resistance) of olive flounder Paralichthys olivaceus against the scuticociliate Philasterides dicentrarchi. All experimental groups were challenged with P. dicentrarchi (1 x 10(5) ciliates/mL) through intraperitoneal administration of the pathogen (50 microL) on day 1. On day 7, the infected groups were fed 0, 5, 50, and 100 mg/kg of the enriched diets. The innate immune parameters, cumulative mortality, and relative percent survival (RPS) were assessed at weeks 1, 2, 3, and 4. Administration of 50 or 100 mg/kg of the herbal-enriched diet enhanced immunity throughout the experimental period. However, at the 5-mg/kg dosage, the enriched diet did not enhance the innate immune estimates at any time. At doses of 50 and 100 mg/kg, administration of the diet preceding the challenge with P. dicentrarchi decreased the percentage cumulative mortality in the experimental groups and thereby increased RPS values. This study reports that administration of 50 or 100 mg/kg mixed herbal-enriched diet could positively influence the innate immune response to P. dicentrarchi and enhance the health status of olive flounder with respect to this microbe.

A novel protein isolated from the serum of rabbitfish (Siganus oramin) is lethal to Cryptocaryon irritans

The susceptibility of eight marine fish species cultured in South China were tested for infection by the parasitic ciliate, Cryptocaryon irritans, via a challenge examination and an immobilization assay. All species of fish (representing six different families) that we investigated were infected by C. irritans except the rabbitfish (Siganus oramin), which displayed resistance to C. irritans infection. The infection intensity of rabbitfish (0.92+/-0.97, p<0.05) was significantly lower while the immobilization titres of rabbitfish serum were significantly higher (44.51+/-22.98, p<0.05) than the other seven species of fish. Additionally, the serum of the rabbitfish presented a strong killing effect to C. irritans in vitro. Light microscopy, scanning electron microscopy and fluorescence microscopy confirmed that rabbitfish serum could induce the theront cilia fall off, rupture of the cell membrane because of the swell and rupture of the macronucleus. Rabbitfish serum could also induce the rupture of the trophont membrane and content efflux. Herein a novel antiparasitic protein (APP) was isolated and purified from the serum of rabbitfish (S. oramin) by using a series of salting-out, cation exchange chromatography and two step of reversed phase high performance liquid chromatography (RP-HPLC). Analysis of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that APP was a homogenous polymeric protein with an N-terminal amino acid sequence of SSVEKNLAACLRDND. Its monomeric molecular mass, determined by matrix-assisted laser desorption ionization tandem time-of-flight mass spectrometer (MALDI-TOF-TOF-MS), was found to be 61,739.87 Da. Results of homology analyses indicated that this protein was a newly discovered functional protein in the rabbitfish serum. Laser confocal fluorescence microscopy conformed that the action site of the APP was mainly on the cell membrane and nucleus of theront, which agreed with the results of light microscopy, fluorescence microscopy and scanning electron microscopy. These findings suggest that this protein may contribute considerably to the innate host defence mechanism to combat microbes of the rabbitfish.

Scuticociliatosis and its recent prophylactic measures in aquaculture with special reference to South Korea Taxonomy, diversity and diagnosis of scuticociliatosis: Part I Control strategies of scuticociliatosis: Part II

Scuticociliatosis caused by about 20 species belonging to the Phylum Ciliophora has been recognized as an emerging problem inflicting significant economic loss in aquaculture industry in the world. Among these Philasterides dicentrarchi, Miamiensis avidus, and Uronema marinum are the three species responsible for scuticociliatosis in olive flounder farms of South Korea. Some of the parasites living or scavenger ciliates also have become parasites of aquaculture fish. The major clinico-pathological manifestations of scuticociliatosis infected fishes are anemia, weight loss, dark coloration, enteritis, excessive body mucus, yellowish intestinal mucus, loss of scales, hemorrhagic and/or bleached spots on the skin, and dermal necrotic lesions that finally destroy tissues lead to high mortalities. Affected fish exhibit organ-specific pathological changes in the brain, eyes, muscle, gills, liver, kidney, intestine, and stomach that lead to severe mortality. At present, farmers in South Korea manage scuticociliatosis by using therapeutic measures, such as application of antibiotics like oxytetracycline, gentamycine, tetracycline, amoxycililin, and cefazolin and chemicals, such as formalin, hydrogen peroxide, malachite green, and jenoclean at a concentration of 350 +/- 150 ppm. However till date, no systematic scientific study has been conducted under field condition on the efficacy of these management measures. Under laboratory condition the ciliate can be effectively controlled with the antibiotics and chemicals while on the host, but on entering the host no systemic chemotherapeutic treatment has been yet proven effective. Furthermore the indiscriminate uses of harmful chemicals in aquaculture are increasingly becoming a cause of concern. Recently formalin and malachite green, the most widely used chemicals have been banned in food fish production by FDA as not consumer friendly and being carcinogenic respectively. Vaccines and immunostimulants can induce good immune response and protect against scuticociliatosis as it has been proved in the case of freshwater Ich. Now a days a number of probiotics and herbal formulations are in use against freshwater bacterial and fungal diseases, while, little information is available regarding the different prophylactic measures against marine scuticociliatosis. This review attempts to provide information on the various prophylaxic measures practiced against scuticociliatosis with special reference to olive flounder farms in South Korea.

Antibody responses of turbot Psetta maxima against various antigen formulations of scuticociliates Ciliophora

The kinetics of the antibody production and the protection at challenge were studied in turbot inoculated with various scuticociliate antigen preparations: live ciliates putatively attenuated through long-term in vitro culture (Trial 1) and formalin-killed ciliates without or with GERBU adjuvant in Trials 2, 3, and 4. Antigen used in killed preparations was a mixture of 3 different ciliate isolates (V3) in the case of Trials 2 and 3, whereas in Trial 4, monovalent (V1), trivalent (V3) or pentavalent (V5) antigens were used. A booster injection was administered 28 to 29 d post-priming in all trials. Fish were challenged with virulent live ciliates after the immunization protocol, testing 2 challenge times in Trial 2 (t1 and t2). No protection was obtained in Trial 1 with live ciliates, which in turn were not completely attenuated. Using killed-ciliate formulations, protection was high only in Trial 3 when a low dose (50 000 ciliates fish(-1)) was used for challenge. In Trial 1, heat-inactivated sera of antigen-inoculated fish agglutinated the homologous ciliate, although no specific antibodies were detectable by ELISA. In contrast, high specific antibody levels were detected in antigen-inoculated fish in Trials 2 and 4, and their amount increased progressively, usually peaking after challenge. No advantage was obtained from the use of V5 antigens compared to V1 or V3. No good correlation was observed in most cases between serum antibody levels and protection. Although the use of GERBU adjuvant generally increased the specific immune response, some undesired side effects indicate a need to adjust dosage and/or improve the formulation.

Antigenic and cross-protection studies on two turbot scuticociliate isolates

The protection induced in turbot by inactivated vaccines containing either of two isolates (I(1) and C(1)) of the scuticociliate parasite Philasterides dicentrarchi, which causes important mortalities in turbot cultures, was evaluated in the present study. The results obtained after challenging the fish with the two isolates show that vaccination protected fish only against the homologous isolate, but did not confer cross-protection. The two isolates constitute two serotypes, as shown in the immobilization tests with mouse and turbot anti-I(1) and anti-C(1) antisera, in which only the homologous antisera immobilized the ciliates. ELISA assays, using total antigen free of proteases (TAWP), cytosolic antigens (CYA), ciliar antigens (CA) or membrane protein fraction (MPF), were also carried out. Differences in the levels of antibodies produced in mouse against the homologous and heterologous antigens were observed; these differences were significantly different when the antigen preparations used in the ELISA were TAWP, CYA or CA. Nevertheless, ELISA assays using turbot sera against TAWP did not show significant differences in the levels of antibodies against the homologous and heterologous antigens. Antigenic cross-reactivity was also detected in the Western blot assays, as well as significant differences in the patterns of antigenic recognition in the two isolates - in both reduced and non-reduced TAWP antigens, but which was noteworthy when mouse antisera were used. The results obtained in the present study demonstrate for the first time the existence of serotypes of the ciliate parasite of turbot Philasterides dicentrarchi that display clear antigenic differences, which must be taken into consideration in the future development of a vaccine against scuticociliatosis.

Immune-relevant genes expressed in rainbow trout following immunisation with a live vaccine against Ichthyophthirius multifiliis

Rainbow trout Oncorhynchus mykiss were immunised by intra-peritoneal injection using a live vaccine based on Ichthyophthirius multifiliis (Ich) theronts, which previously has shown protection against white spot disease. Samples were taken pre-vaccination and on Day 1, 7, 21 and 28 post-immunisation (p.i.). Expression of immune relevant genes in the liver, spleen and head kidney was monitored by qPCR. To describe the immune reaction following this immunisation, a series of genes encoding cytokines, complement factors, immunoglobulins and acute phase reactants were studied. Genes encoding acute phase reactants in the liver were up-regulated with serum amyloid A (SAA) as the most pronounced with a 2299-fold increase at 24 h p.i. Hepcidin and pre-cerebellin were also up-regulated in the liver 24 h p.i., by 7- and 4-fold, respectively. Complement factors C3, C5 and factor B (Bf) were up-regulated in the spleen and the head kidney 24 h and 28 d p.i. Genes encoding immunoglobulins were not up-regulated, but a specific low titer IgM response (titer 25) against parasite antigens was detected by a modified ELISA 4 wk p.i.

Can the surface immobilization antigens of Philasterides dicentrarchi (Ciliophora: Scuticociliatida) be used as target antigens to develop vaccines in cultured fish?

In order to test whether immobilization antigens (i-antigens) of Philasterides dicentrarchi could be suitable antigenic targets against scuticociliatosis, polyclonal olive flounder (Paralichthys olivaceus) sera were raised against P. dicentrarchi by immunization with lysates of ciliates grown using chinook salmon epithelial (CHSE) cells, and the ability of the immune sera to kill the ciliates via classical complement pathway was analyzed in relation to agglutination activity. The immune sera showed clear agglutination activity against the CHSE-cultured ciliates. However, the agglutinated ciliates were not killed but escaped from the agglutinated mass within a few hours. Ciliates isolated from fish artificially infected with the same population of CHSE-cultured ciliates were not agglutinated by the immune sera even at the lowest dilution. In antibody-dependent complement-mediated killing (ADCK), the immune sera completely killed the CHSE-cultured ciliates at relatively higher serum dilutions (showing low or no agglutination activity). However, CHSE-cultured ciliates were not killed completely at lower immune serum dilutions (showing high agglutination activity). In contrast to CHSE-cultured ciliates, the ciliates isolated from infected fish were killed at lower dilutions of the immune sera in spite of no agglutination response. Considering the presence of various i-antigen types, ability to change i-antigen type in response to corresponding antibody, and relatively low ADCK activity at high agglutination titer, i-antigens of P. dicentrarchi may not be good targets for subunit vaccine development. To develop subunit vaccines against scuticociliatosis, other surface antigens expressed constitutively or expressed specifically under the infection state for survival of the ciliates in the host fish might be more favorable to elicit protective antibodies than the surface i-antigens.

Immune response of turbot, Psetta maxima (L.) (Pisces: Teleostei), to formalin-killed scuticociliates (Ciliophora) and adjuvanted formulations

The increasing frequency of scuticociliatosis in turbot culture has stressed the need of knowledge on the immune responses to these parasites, for further developing of prevention and control strategies. The immune response of turbot to killed parasites, alone (Ag) or in combination with Montanide ISA 763A (MON), was studied in a laboratory-scale experiment. The variations of several innate immune factors and the antibody response were analysed in immunized vs. non-immunized fish at different times after immunization, and also after a challenge with live ciliates. Amongst innate immune factors, serum lysozyme increased progressively in all inoculated groups. Differences in innate immune factors in Ag and Ag-MON fish with respect to controls were mainly evidenced after challenge, especially for serum complement. Serum antibody levels increased in immunized fish after booster and particularly after challenge. In addition, certain protection was obtained for immunized groups compared to controls or to fish receiving MON alone, and the levels of specific antibodies were also the highest in immunized groups. The obtained information could be useful for further design of immunoprophylactic formulations against scuticociliatosis.

Evidence for a relationship between bovine erythrocyte lipid membrane peculiarities and immune pressure from ruminal ciliates

Erythrocytes of bovines and other ruminants have a strikingly anomalous phospholipid composition, with low or absent phosphatidylcholine (PC) together with high sphingomyelin (SM) content. Here, we report the presence in normal bovine serum of high levels of anti-phospholipid antibodies of IgM isotype against, PC and the phosphono analogue of phosphatidylethanolamine, aminoethylphosphonolipid (AEPL), normally produced by rumen ciliates. In contrast, no antibodies were detected against SM or N-acyl-phosphatidylethanolamine (NAPE), the major components of bovine erythrocytes. In addition, we found that exposure of the ciliate Tetrahymena thermophila to bovine serum results in rapid lysis, an effect that was inhibited by adsorption of the serum with SM/AEPL liposomes. Furthermore, incubation with bovine serum had a similar effect on freshly obtained ruminal ciliates, and the lytic activity was eliminated by pre-adsorption of the serum with SM/PE liposomes. The ruminant mode of life with its concomitant ciliate fauna is hereby linked to the peculiar conformation of bovine erythrocyte membranes. We propose that the unique phospholipid composition of bovine erythrocytes appears as an evolutionary adaptation to tolerate the lytic effects of anti-phospholipid antibodies generated against AEPL, a membrane component of the huge mass of ruminal ciliates, necessary commensals of this group of mammals.

Reponses of sheep to a vaccination of entodinial or mixed rumen protozoal antigens to reduce rumen protozoal numbers

Two rumen protozoa vaccine formulations containing either whole fixed Entodinium or mixed rumen protozoa cells were tested on Merino sheep with the aim of decreasing the number and/or activity of protozoa in the rumen. Negative control (no antigen) and positive control (Tetrahymena corlissi antigens) treatments were also included in the experiment. Blood and saliva were sampled to measure the specific immune response. Protozoal numbers in the rumen were monitored by microscopic counts. Vaccination with protozoal formulations resulted in the presence of specific IgG in plasma and saliva, but saliva titres were low. Titres after secondary vaccination were higher (P < 0·05) than after primary vaccination. There was a moderate (r2 0·556) relationship (P < 0·05) between plasma and saliva titres for the rumen protozoal vaccine formulations. Rumen protozoa were not decreased (P>0·05) by the vaccination and there was also no difference (P>0·05) between treatments in rumen fluid ammonia-N concentration or wool growth. In vitro studies investigated the binding ability of the antibodies and estimated the amount of antibody required to reduce cell numbers in the rumen. The studies showed that the antibodies did bind to and reduced protozoa numbers, but the amount of antibody generated by vaccination was not enough to produce results in an in vivo system. It is suggested that the vaccine could be improved if specific protozoal antigens are determined and isolated and that improved understanding of the actions of protozoa antibodies in rumen fluid and the relationships between levels of antibodies and numbers of protozoa in the rumen is needed.

Protective immunity in grouper (Epinephelus coioides) following exposure to or injection with Cryptocaryon irritans

The protective immunity of grouper (Epinephelus coioides) against Cryptocaryon irritans was determined after immunisation by surface exposure or intraperitoneal injection. Specific antibody titres of immunised fish serum and skin culture supernatant were determined by enzyme-linked immunosorbent assay and immobilisation assays. Specific antibody can be detected in some immunised fish at Week 1 and in all immunised fish at Week 2, and the peaks were between Weeks 4-6. Specific antibody was still evident in the serum and skin of immunised fish at Week 8, and provided good protection against challenge with C. irritans. These findings indicated that humoral and skin mucosal immunity play important roles in fish against C. irritans infection.

Scuticociliate proteinases may modulate turbot immune response by inducing apoptosis in pronephric leucocytes

The role of proteinases of the histiophagous ciliate Philasterides dicentrarchi, purified by affinity chromatography in bacitracin-Sepharose, on apoptosis (programmed cell death) of turbot pronephric leucocytes (PL) was investigated. The results showed that more than 90% of proteinases purified by bacitracin-Sepharose were cysteine proteinases, which lacked significant caspase-3-like activity and generated three main gelatinolytic bands of molecular weights 36, 45 and 77 kDa as determined by gelatine-SDS-PAGE and immunoblot. Viability of PL cells after 24 h stimulation with P. dicentrarchi cysteine proteinases did not differ from that of non-stimulated cells. Apoptosis was confirmed by: (i) caspase activity, (ii) DNA fragmentation, and (iii) nucleus fragmentation. The caspase-3-like activity in PL incubated for 4h in the presence of 125, 250 and 500 microg/ml of proteinases increased in a dose-dependent fashion. The PL DNA was fragmented following 24-h exposure to P. dicentrarchi cysteine proteinases and characteristic DNA ladders consisting of multimers of approximately 180-200 pb were produced. Morphological changes, such as chromatin condensation and nucleus fragmentation, were observed under fluorescence microscopy after DAPI staining of the PL cells incubated with cysteine proteinase-incubated for 24 h. The results suggest that the pathogenic scuticociliate P. dicentrarchi may induce host leucocyte programmed cell death via the production of cysteine proteinases, as a mechanism of pathogenesis and evasion of the turbot innate immune response.

Temperature-dependent protection against Ichthyophthirius multifiliis following immunisation of rainbow trout using live theronts

Rainbow trout Oncorhynchus mykiss Walbaum, 1792 fingerlings were vaccinated by intraperitoneal (i.p.) injection using live theronts of the skin parasitic ciliate Ichthyophthirius multifiliis Fouquet, 1876 at 2 temperatures (12 and 20 degrees C), and protection against challenge infections was subsequently evaluated by bath exposure to live theronts. Vaccination conferred a relative protection (evaluated as the decrease in the number of established theronts) at 12 degrees C and almost complete immunity at 20 degrees C. Significantly increased immobilisation titers (using plasma immobilisation of live theronts) were found in immunised fish at Week 2 and 4 post-vaccination. Lysozyme activity of plasma from vaccinated fish increased from Week 1 to 4. Both immobilisation titers and lysozyme activity were significantly higher at 20 degrees C. This study demonstrated that live theronts are good candidates for an antigen source for development of effective vaccines against white spot disease in this fish host, and further indicated that the protection of rainbow trout against I. multifiliis infection is highly temperature dependent and may be associated with both adaptive and innate response mechanisms.

Localization of centrins in the hypotrich ciliate Paraurostyla weissei

Centrins are ubiquitous cytoskeletal proteins that are generally associated with the centrosome and form large cytoskeletal networks in protists. To obtain more data on the respective role of different centrin proteins, we studied their distribution and behavior in one ciliate species, Paraurostyla weissei, using specific antibodies. In this species, only two major proteins of 21 and 24 kDa corresponding to centrins, were identified by 1D and 2D electrophoresis. Immunofluorescence analysis showed that these two proteins displayed non-overlapping localization in the interphase cell and during morphogenesis. Both centrin proteins localize on the fibrous network linking the oral basal bodies in the interphase cell and in the form of marginal dots, which correspond to the proximal ends of the striated rootlets; the 21 kDa centrin was also detected within the basal bodies, whereas the 24 kDa centrin allowed identifying new structures, the frontal dashes. During morphogenesis, the 21 kDa centrin locates at the basal bodies, while the 24 kDa centrin is detected along the striated rootlets and in close association with the basal bodies pairs. These data are discussed in terms of the potential roles of the two centrins in different cellular functions.

Cadmium effects on Ichthyophthirius: evidence for metal-sequestration in fish tissues following administration of recombinant vaccines

We are developing Tetrahymena thermophila as a delivery system for recombinant vaccines against parasitic protozoa, including the common fish parasite, Ichthyophthirius multifiliis. T. thermophila cell lines expressing I. multifiliis genes under the control of a cadmium-inducible metallothionein gene promoter conferred strong protection against a lethal parasite challenge when administered parenterally to naive fish. Nevertheless, given that heavy metals can be toxic to parasites, a question arose as to whether protection resulted from Cd residues carried over with the vaccine, rather than acquired immunity per se. To address this issue, we examined the sensitivity of I. multifiliis to Cd in vitro and determined Cd concentrations in different host tissues following i.p. injection of juvenile channel catfish with the recombinant vaccine. We found that CdCl2 at concentrations > or = 50 ppb were lethal to I. multifiliis theronts in vitro. Furthermore, Cd concentrations were clearly elevated in fish tissues and reached levels equivalent to 74 ng/g wet weight (74 ppb) in the skin within 14 days of injection with recombinant T. thermophila. Nevertheless, fish injected with non-transformed Tetrahymena grown in the presence or absence of CdCl2 showed no significant difference in either relative survival or parasite load following direct challenge with I. multifiliis.

Environmental factors influencing the immune responses of the common European starfish (Asterias rubens)

The influence of handling, salinity, temperature, parasitism, and gender on the immune responses (reactive oxygen species (ROS) production and coelomic amoebocyte concentration (CAC) of the starfish Asterias rubens was investigated in experimental conditions. Additionally, a year-round monthly survey in two distant sites was conducted in order to understand which of these factors most influences the immunity of A. rubens in field conditions. All considered factors, except gender and handling stress, influenced the studied immune responses of A. rubens in experimental conditions. Amoebocyte ROS production was increased at low salinity and at the lowest temperature tested (6 degrees C). Amoebocyte concentration in the coelomic fluid was increased in starfish infested by the ciliate Orchitophrya stellarum. However, among all these factors, only temperature could be linked with the variability in ROS production measured in the field during the monthly survey. The variability in amoebocyte concentration in the field does not seem to be linked to any of the factors considered in this study; it appears to reflect mostly an inter-individual variation rather than seasonal fluctuations. Recommended periods and indicative values of immune responses are proposed for field studies using A. rubens.

Protective effect of cutaneous antibody produced by channel catfish, Ictalurus punctatus (Rafinesque), immune to Ichthyophthirius multifiliis Fouquet on cohabited non-immune catfish

Fish which survive a sublethal ichthyophthiriasis acquire protective immunity against Ichthyophthirius multifiliis Fouquet (Ich). This study evaluated the protective effect of cutaneous antibody secreted by channel catfish, Ictalurus punctatus (Rafinesque), immune to Ich on cohabited non-immune catfish. Non-immune and immune fish controls were separately maintained and infected with theronts. The Ich infection was assessed by scoring 0, < 50, 50-100, and > 100 trophonts fish(-1) at 5 days post-infection. The results of infection showed that cohabited fish at the ratio of 15 non-immune to two immune fish had < 50 trophonts fish(-1). Eighty per cent of the cohabited fish at the ratio of 10 non-immune to two immune fish showed 0 or < 50 trophonts fish(-1). The 76% of control non-immune fish had more than 100 trophonts fish(-1). The control immune fish had 0 trophonts fish(-1). Anti-Ich antibody was detected using enzyme-linked immunosorbent assay in water samples taken from tanks containing immune fish after the water samples were concentrated 40-fold. The study suggests that immune fish cohabited with non-immune fish may protect non-immune fish against Ich infection.

Inhibition of chemiluminescent response of olive flounder Paralichthys olivaceus phagocytes by the scuticociliate parasite Uronema marinum

Experiments were conducted to evaluate the in vitro capacity of the scuticociliatian parasite Uronema marinum to inhibit chemiluminescence (CL) of olive flounder Paralichthys olivaceus phagocytes. Luminol-enhanced CL was used to measure the production of reactive oxygen intermediates (ROIs) generated by respiratory bursts of phagocytes using zymosan as a stimulant. Cytotoxic and antioxidative activities of excretory-secretory (ES) products of the parasite were evaluated as well. Live U. marinum and its ES products had a negative and dose-dependent effect on luminol-enhanced CL responses of zymosan-stimulated phagocytes of olive flounder. After CL assay, the number of phagocytes showing viability was significantly reduced in the cells incubated with live U. marinum at ratios of 2:1 and 1:1 phagocytes:ciliates or ES products with 0.3 mg protein ml(-1) compared to controls. Lysis of phagocytes by exposure to ES products was observed also. ES products from U. marinum showed considerably high activities of superoxide dismutase (SOD) and catalase. The results of this study suggest that U. marinum can protect itself against host's phagocytes mediated oxidative damage by destroying phagocytes and scavenging ROIs.

[Serotypes of the lower ciliate Dileptus anser]

The author's data on the serotype composition in various clones of Dileptus anser are reviewed. This species is a novel subject of choice for studying the serotype problem in ciliates. The results obtained for serotypes of D. anser demonstrated several features shared also by some higher ciliates of the genera Paramecium and Tetrahymena, i.e. the well known classical models for serotype research. At the same time, some particular data obtained for D. anser do not fit in with the generally accepted picture of relevant events. Special attention is paid to a poor knowledge of the sexual process in this ciliate, which obviously hampers the true understanding of many events. Nevertheless, D. anser may be regarded as a suitable model for studying such important problems of general biology as epigenetic variability or inheritance.

Surface immobilization antigen of the parasitic ciliate Ichthyophthirius multifiliis elicits protective immunity in channel catfish (Ictalurus punctatus)

Channel catfish (Ictalurus punctatus) that survive infection with the parasitic ciliate Ichthyophthirius multifiliis acquire immunity to subsequent challenge and produce specific antibodies in serum that immobilize the parasite in vitro. Cellular surface protein antigens targeted by these antibodies are referred to as immobilization antigens (i-antigens). By using an immobilizing mouse monoclonal antibody as a ligand, the i-antigen of I. multifiliis isolate G5 was purified to homogeneity by immunoaffinity chromatography, and its immunogenicity was confirmed by inoculating rabbit and channel catfish to produce immobilizing antisera. To test the purified i-antigen as a subunit vaccine, channel catfish fingerlings were injected intraperitoneally (i.p.) with purified i-antigen at a dose of 10 microg/fish in complete Freund's adjuvant on day 1, followed by a second i.p. injection of the same amount of i-antigen in incomplete Freund's adjuvant on day 15. Negative control fish were immunized similarly with either bovine serum albumin (BSA) or an immobilization-irrelevant I. multifiliis protein. On day 84, the fish were challenged with live I. multifiliis G5 theronts at a dose of 15,000 cells per fish. Seventy-two percent of the fish immunized with i-antigen survived the challenge. All negative control fish died within 16 days of exposure. There was a significant difference in the median days to death between the negative control fish injected with BSA and the fish that died following vaccination with i-antigen. Fish injected with i-antigen developed high immobilizing antibody titers in serum. This is the first demonstration of a direct role for i-antigens in the elicitation of protective immunity, suggesting that these proteins by themselves serve as effective subunit vaccines against I. multifiliis.

[Re-expression of various i-antigens in Dileptus anser after temporary transformation of serotype]

RNP particles containing 20S prosomes (alpha RNP) isolated from human epidermoid carcinoma cell line A-431 are shown to posses strong and regulated endonuclease activity specific for high-molecular-weight RNA, particularly, specific mRNAs. Furthermore, alpha-RNP destabilize the 3'-untranslated regions of c-myc mRNA, creating a specific cleavage pattern. Cleavage point within Alu sequence in high-molecular-weight RNA has been localized by primer-extension method. This RNase activity is induced under the action of EGF. alpha-RNP involvement in the coordinated control of processing and stability of specific messenger RNA molecules is suggested. The endoribonuclease activity of alpha-RNP can represent a link between EGF signalling pathway and RNA processing and degradation.

Host responses against the fish parasitizing ciliate Ichthyophthirius multifiliis

Recent studies have shown that fish are able to mount protective immune responses against various parasites. One of the best characterized parasite-host system in this context is the ciliate Ichthyophthirius multifiliis (Ich) parasitizing a range of freshwater fishes. Both specific and non-specific host defence mechanisms are responsible for the protection of fish against challenge infections with this ciliate. The specific humoral components comprise at least specific antibodies. The non-specific humoral elements included are the alternative complement pathway and probably lectins. Cellular factors involved in the specific response are B-cells and putative T-cells. The non-specific effector cells recognized are various leukocytes. In addition, goblet-cells and mast cells (EGC-cells) may have a function. The NCC-cell (suggested analogue to NK-cells in mammals) seems to play a role in the non-specific response. This well documented protective response in freshwater fishes against Ich has urged the development of anti-parasitic vaccines. Indeed, such products based on formalin killed parasites have been developed and found to offer the vaccinated host a satisfactory protection. However, the collection of parasites for vaccine production is extremely laborious. It involves keeping infected fish due to the fact that in vitro propagation of the parasite is still insufficiently developed. Gaining knowledge of amino acid sequences and its encoding DNA-sequences for the protective antigens (i-antigens) in the parasite was a major breakthrough. That achievement made it possible to produce a recombinant protein in E. coli and preliminary results indicated a certain protection of fish vaccinated with this product. Recent work has shown that the free-living and easily cultivated ciliate Tetrahymena can be transformed and express the i-antigen. This path seems to be promising for future development of vaccines against Ich. A novel approach in fish is the development of DNA-vaccines. Successful DNA-vaccination trials have been conducted in fish against viral infections and the technology also makes it possible to develop a DNA-vaccine against Ich. Other approaches to immuno-protection against Ich have been the use of heterologous vaccines. Thus, both bath and injection vaccination using live or killed (un-transformed) Tetrahymena has been reported to offer treated fish a certain level of protection. Such protection could be explained by non-specific reactions and the efficacy and duration of this vaccination type should be further evaluated.

The I-antigens of Ichthyophthirius multifiliis are GPI-anchored proteins

The parasitic ciliate Ichthyophthirius multifiliis has abundant surface membrane proteins (i-antigens) that when clustered, trigger rapid, premature exit from the host. Similar antigens are present in free-living ciliates and are GPI-anchored in both Paramecium and Tetrahymena. Although transmembrane signalling through GPI-anchored proteins has been well-documented in metazoan cells, comparable phenomena have yet to be described in protists. Since premature exit of Ichthyophthirius is likely to involve a transmembrane signalling event, we sought to determine whether i-antigens are GPI-anchored in these cells as well. Based on their solubility properties in Triton X-114, the i-antigens of Ichthyophthirius are amphiphilic in nature and partition with the detergent phase. Nevertheless, following treatment of detergent lysates with phospholipase C, the same proteins become hydrophilic. Concomitantly, they are recognized by antibodies against a cross-reacting determinant exposed on virtually all GPI-anchored proteins following cleavage with phospholipase C. Finally, when expressed in recombinant form in Tetrahymena thermophila, full-length i-antigens are restricted to the membrane, while those lacking hydrophobic C-termini are secreted from the cell. Taken together, these observations argue strongly that the i-antigens of Ichthyophthirius multifiliis are, in fact, GPI-anchored proteins.

[Mode of serotype inheritance in exoconjugant progeny of the ciliate Dileptus anser]

Two clones of Dileptus anser, originally isolated from natural reservoirs and referred to below as B and D clones, were found to display different serotypes, when cultured under identical laboratory conditions. On being tested with two different polyclonal rabbit immune sera against each particular clone (the classic immobilization test) these clones showed no cross-reaction. At a standard dilution (1:50) and at a standard exposure time (4 h), either of the two immune sera immobilized 100% or commonly 0% of homologous and heterologous clone cells, respectively. In addition, the difference in serotypes was confirmed by the immunofluorescence analysis. By crossing (conjugation) between B (mating type I) and D (mating type III) cells, exconjugant F1 clones were obtained. Their serotypes were then tested (the same immobilization test) with antisera against both the "parental" clones: some clones were tested before their sexual maturation in ca. one month after conjugation, while others were examined in approximately 4 months after conjugation, i.e. after reaching maturity. Each of the F1 clones could react with both immune sera, which means that they possessed the intermediate, "hybrid" phenotype. Five different F1 clones were selected, and each of them was back-crossed to both "parental" clones, B and D. We succeeded in raising 25 exconjugant F2 (B1, to be more exact) clones from F1 x B crosses and 26 clones from F1 x D crosses. The conventional testing of these clones in 5-10 weeks after conjugation provided quite unexpected results, since among them no segregation for "parental" serotypes was observed. Each of the 51 tested clones demonstrated the "hybrid" serotype--seemingly the same as that of F1 clones. Such a non-Mendelian inheritance of the character is hardly to explain from the standard, canonical assumptions on the genetic control of serotype difference between original "parental" clones (different alleles in one locus? different loci?). Also it does not seem likely that the absence of segregation could result from differential survival of various phenotypes in F2 (although the total viability of exconjugant clones appeared rather low). The above data obviously need further confirmations and experimental analyses. We attempt to discuss the obtained results in terms of the epigene hypothesis (Tchuraev, 1975) and in relation to the epigenetic control of serotype expression in species of the Paramecium aurelia complex and in Tetrahymena thermophila, which are "the chosen few" subjects in ciliate genetics.

Different types of response to foreign antigens by leech leukocytes

We used morphological and immunocytochemical approaches to characterize and to show the behavior of cells involved in leech inflammatory responses. Leeches were injected with bacterial lipopolysaccharide, fluoresceinated yeasts, sulfate spheres and ciliates (Protozoa). Shortly after injection, migrating cells appeared in the area of injection. The response of the cells occurred in relation to the injected micro or macro antigens. Each injection first provoked a migration of cells towards the non-self material. Afterwards, different responses (degranulation, phagocytosis, encapsulation, melanization) occurred. The migrating cells involved in these series of processes have a similar behavior and are characterized by CD markers of macrophages, NK cells and granulocytes, which are typical of many invertebrates and vertebrates.

A nuclear protein involved in apoptotic-like DNA degradation in Stylonychia: implications for similar mechanisms in differentiating and starved cells

Ciliates are unicellular eukaryotic organisms containing two types of nuclei: macronuclei and micronuclei. After the sexual pathway takes place, a new macronucleus is formed from a zygote nucleus, whereas the old macronucleus is degraded and resorbed. In the course of macronuclear differentiation, polytene chromosomes are synthesized that become degraded again after some hours. Most of the DNA is eliminated, and the remaining DNA is fragmented into small DNA molecules that are amplified to a high copy number in the new macronucleus. The protein Pdd1p (programmed DNA degradation protein 1) from Tetrahymena has been shown to be present in macronuclear anlagen in the DNA degradation stage and also in the old macronuclei, which are resorbed during the formation of the new macronucleus. In this study the identification and localization of a Pdd1p homologous protein in Stylonychia (Spdd1p) is described. Spdd1p is localized in the precursor nuclei in the DNA elimination stage and in the old macronuclei during their degradation, but also in macronuclei and micronuclei of starved cells. In all of these nuclei, apoptotic-like DNA breakdown was detected. These data suggest that Spdd1p is a general factor involved in programmed DNA degradation in Stylonychia.

Anti-immunoglobulin antisera used in an ELISA to detect antibodies in barramundi Lates calcarifer to Cryptocaryon irritans

Immunoglobulins (Ig) in serum from barramundi vaccinated with bovine serum albumin (BSA) were purified by ammonium sulphate precipitation and affinity chromatography using BSA as the ligand. The BSA-binding activity of eluted putative Ig fractions was assessed by enzyme-linked immunosorbent assay (ELISA) before being pooled and characterised by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Double affinity purification did not improve the purity of the Ig preparation compared to single affinity purification. Barramundi Ig were injected into sheep to produce anti-Ig antisera which were assessed in an indirect ELISA as the secondary antibody to detect serum Ig in barramundi vaccinated with Cryptocaryon irritans theronts. Affinity-purified Ig induced a more specific reagent for use as secondary antibody in ELISA than did normal whole-barramundi sera. The heavy (H) chain of barramundi Ig had an apparent molecular weight of 70 kDa while that of the light (L) chain was 27 kDa in SDS-PAGE studies. Under non-reducing conditions 2 putative populations of Ig were identified, at 768 and 210 kDa. The N-terminal sequence of the barramundi Ig H chain showed 78% homology with channel catfish Ictalurus punctatus Ig H chain sequence.

Distribution of a centrosomal antigen during morphogenesis in the ciliated protozoan Euplotes

Ciliates assemble basal bodies in great number at many stages of the life-cycle. In order to understand their assembly mechanisms, we screened a library of monoclonal antibodies directed against pericentriolar material. One of these antibodies, CTR210, was used previously to follow steps of this assembly process: in Paraurostyla, new basal bodies appear along a scaffold of linear structures recognized by this antibody. The very unusual behavior of this antigen deserved confirmation in other species. In the present study, we show by immunofluorescence that, in another phylogenetically very distant species, Euplotes, basal bodies are assembled in the same pathway during division. In addition, this antibody recognizes a filamentous ring located at the division furrow and linking many basal body assemblages. By cell fractionation and cytoskeletal extraction, we obtained fractions enriched in basal bodies and associated material. Such fractions still display a high complexity in protein composition. These fractions were used to characterize the main target of the antibody as a doublet of 45 kDa. These results confirm previous results in terms of functionality of the protein recognized by the antibody, but raise new questions in terms of the assignment of the recognized protein to the HSP70 family as hypothesized previously.

Characterization of centrin genes in Paramecium

Centrins are highly conserved, ubiquitous cytoskeletal components which belong to the EF-hand superfamily of Ca2+-modulated proteins. We report here the molecular characterization of new members of the centrin family, Paramecium centrins. Previous studies described the organization of the infraciliary lattice (ICL), the innermost cortical cytoskeletal network of Paramecium, and showed that it was composed of a set of low-molecular-mass, Ca2+-binding polypeptides [Garreau de Loubresse, N., Klotz, C., Vigues, B., Rutin, J & Beisson, J. (1991) Biol. Cell 71, 217-225]. In this paper we show that these polypeptides are recognized by specific anti-centrin polyclonal antibodies. Their microsequences revealed four distinct N-termini. For one of them, ICL1, N-terminal and internal peptide sequences were used for PCR amplification and cloning of a DNA fragment containing a complete centrin coding sequence. The deduced amino acid sequence presents about 50% identify with those of centrins from other species. Further molecular analysis allowed us to identify two additional closely related, co-expressed ICL1 genes, providing the first example of a centrin multigenic family in a microorganism.

Polypeptides of hydrogenosome-enriched fractions from rumen ciliate protozoa and trichomonads: immunological studies

The evolution of hydrogenosomes, energy-generating organelles of rumen ciliate protozoa and the flagellate trichomonads has been the subject of much speculation. Polypeptides of the hydrogenosome-enriched fractions from the rumen ciliates, Dasytricha ruminantium, Isostricha spp., Polyplastron multivesiculatum and Eudiplodinium maggii were separated by SDS-PAGE and compared to analogous polypeptide preparations from Tritrichomonas foetus. Immunoblotting with antisera specific to the hydrogenosomes of T. foetus identified common immunoreactive polypeptides present at estimated molecular masses of 28, 35, 38, 44, 48, 58, 100 and 120 kDa. That at 120 kDa corresponds to a single subunit of the purified pyruvate:ferredoxin oxidoreductase from the hydrogenosome of Trichomonas vaginalis.

Specific and common epitopes in mating pheromones of Euplotes raikovi revealed by monoclonal antibodies

Polypeptide mating pheromones Er-1 and Er-2, purified from the supernatant of Euplotes raikovi cultures of mating type I and mating type II, respectively, were used to immunize mice and obtain monoclonal antibodies. Five hybridoma clones producing antibodies specific to the mating pheromones were selected. They were analyzed for immunospecificity by immunoperoxidase assay, immunoblotting, and for their efficacy in inhibition of mating pheromone activity. Monoclonal antibodies from two hybridoma clones recognized only the mating pheromone used as antigen: those from the other three clones reacted, to comparable extents, with both mating pheromones. On the basis of these results it was assumed that two immunogenic sites exist in Er-1 and Er-2, one specific and the other common to both mating pheromones.

Icthyophthirius multifiliis has membrane-associated immobilization antigens

Sera from fish that survive infections with the ciliated protozoon, Ichthyophthirius multifiliis, immobilize the parasite in vitro. In order to identify cell surface antigens involved in the immobilization response, integral membrane proteins were extracted from tomites with Triton X-114 and used to immunize rabbits. The rabbit antisera immobilized the parasite in vitro and antigens were localized to cell and ciliary plasma membranes by indirect immunofluorescent microscopy. The membrane protein fractions from both whole cells and tomite cilia were characterized by 1- and 2-dimensional SDS-PAGE. A 43,000-dalton (D) glycoprotein with an isoelectric point of 7.0 is the predominant protein in these fractions, comprising 12% and 60% of the total protein of whole cell and ciliary membranes, respectively. Western blot analysis of ciliary proteins with immune rabbit sera indicated that the 43,000-D glycoprotein is the principal antigen.