Varying disease-mediated selection at different life-history stages of Atlantic salmon in fresh water.

Laboratory studies on associations between disease resistance and susceptibility and major histocompatibility (MH) genes in Atlantic salmon Salmo salar have shown the importance of immunogenetics in understanding the capacity of populations to fight specific diseases. However, the occurrence and virulence of pathogens may vary spatially and temporally in the wild, making it more complicated to predict the overall effect that MH genes exert on fitness of natural populations and over several life-history stages. Here we show that MH variability is a significant determinant of salmon survival in fresh water, by comparing observed and expected genotype frequencies at MH and control microsatellite loci at parr and migrant stages in the wild.

Contrasting responses to selection in class I and class IIα major histocompatibility-linked markers in salmon.

Comparison of levels and patterns of genetic variation in natural populations either across loci or against neutral expectation can yield insight into locus-specific differences in the strength and direction of evolutionary forces. We used both approaches to test the hypotheses on patterns of selection on major histocompatibility (MH)-linked markers. We performed temporal analyses of class I and class IIα MH-linked markers and eight microsatellite loci in two Atlantic salmon populations in Ireland on two temporal scales: over six decades and 9 years in the rivers Burrishoole and Delphi, respectively.

Genomic organisation analysis of novel immunoglobulin-like transcripts in Atlantic salmon (Salmo salar) reveals a tightly clustered and multigene family.

Background: Several novel immunoglobulin-like transcripts (NILTs) which have previously been identified in the salmonid species rainbow trout (Oncorhynchus mykiss) contain either one or two extracellular Ig domains of the V-type. NILTs also possess either an immunoreceptor tyrosine-based activating motif (ITAM) or immunoreceptor tyrosine-based inhibitory motifs (ITIMs) in the cytoplasmic region resulting in different signalling abilities. Here we report for the first time the genomic organisation and structure of the multigene family of NILTs in Atlantic salmon (Salmo salar) using a BAC sequencing approach.

Rainbow trout (Oncorhynchus mykiss) possess multiple novel immunoglobulin-like transcripts containing either an ITAM or ITIMs.

The recognition of pathogens by the innate immune system relies on a wide range of inhibitory and activating receptors. Some of these non-rearranging receptors belong to the immunoglobulin superfamily (IgSF) and in teleost fish the novel immune-type receptor (NITR) and the novel immunoglobulin-like transcript (NILT) have been reported. Here we describe the identification and characterisation of three new NILTs from rainbow trout (Oncorhynchus mykiss), with one NILT alternatively spliced into a long isoform containing two Ig domains and a short isoform containing one Ig domain.

Atlantic salmon eggs favour sperm in competition that have similar major histocompatibility alleles.

Polyandry and post-copulatory sexual selection provide opportunities for the evolution of female differential sperm selection. Here, we examined the influence of variation in major histocompatibility (MH) class I allelic composition upon sperm competition dynamics in Atlantic salmon. We ran in vitro fertilization competitions that mimicked the gametic microenvironment, and replicated a paired-male experimental design that allowed us to compare differences in sperm competition success among males when their sperm compete for eggs from females that were genetically either similar or dissimilar at the MH class I locus.

Classical crosses of common carp (Cyprinus carpio L.) show co-segregation of antibody response with major histocompatibility class II B genes.

In cyprinids, two paralogous groups of major histocompatibility (MH) class II B genes, DAB1 and DAB3, have been reported but have not been studied in detail. In our study on MH association with immune responsiveness in common carp (Cyprinus carpio L.) we have taken a long-term approach using divergent selection for antibody production.

Application of PCR-RF-SSCP to study major histocompatibility class II B polymorphism in common carp (Cyprinus carpio L.).

A variety of methods have been applied for the characterization of major histocompatibility (MH) polymorphism in fish. We optimized a technique designated polymerase chain reaction-restriction fragments-single strand conformation polymorphism (PCR-RF-SSCP) for screening a large number of individuals for the Cyca-DAB1 and Cyca-DAB2 genes polymorphism in common carp. The advantages of this technique are simplicity, high sensitivity and low costs.

Expression and characterization of recombinant single-chain salmon class I MHC fused with beta2-microglobulin with biological activity.

Heterodimeric class I major histocompatibility complex (MHC) molecules consist of a putative 45-kDa heavy chain and a 12-kDa beta2-microglobulin (beta2m) light chain. The knowledge about MHC genes in Atlantic salmon accumulated during the last decade has allowed us to generate soluble and stable MHC class I molecules with biological activity. We report here the use of a bacterial expression system to produce the recombinant single-chain MHC molecules based on a specific allele Sasa-UBA*0301.

Peptide-binding motif prediction by using phage display library for SasaUBA*0301, a resistance haplotype of MHC class I molecule from Atlantic Salmon (Salmo salar).

The structure of the peptide-binding specificity of major histocompatibility complex (MHC) class I has been analyzed extensively in human and mouse. For fish, there are no crystallographic models of MHC molecules, neither are there data on the peptide-binding specificity. In this study, we describe for the first time the identification of a fish class I peptide-MHC ligand binding motif.

Molecular cloning, differential expression and 3D structural analysis of the MHC class-II beta chain from sea bass (Dicentrarchus labrax L.).

The major histocompatibility complex class I and II molecules (MHC-I and MHC-II) play a pivotal role in vertebrate immune response to antigenic peptides. In this paper we report the cloning and sequencing of the MHC class II beta chain from sea bass (Dicentrarchus labrax L.).

Molecular cloning and expression of a Toll receptor in the giant tiger shrimp, Penaeus monodon.

Invertebrates rely completely for their protection against pathogens on the innate immune system. This non-self-recognition is activated by microbial cell wall components with unique conserved molecular patterns. Pathogen-associated molecular patterns (PAMPs) are recognised by pattern recognition receptors (PRRs).

Natural selection acts on Atlantic salmon major histocompatibility (MH) variability in the wild.

Pathogen-driven balancing selection is thought to maintain polymorphism in major histocompatibility (MH) genes. However, there have been few empirical demonstrations of selection acting on MH loci in natural populations. To determine whether natural selection on MH genes has fitness consequences for wild Atlantic salmon in natural conditions, we compared observed genotype frequencies of Atlantic salmon (Salmo salar) surviving in a river six months after their introduction as eggs with frequencies expected from parental crosses.

Head kidney-derived macrophages of common carp (Cyprinus carpio L.) show plasticity and functional polarization upon differential stimulation.

Cells from the myeloid lineage are pluripotent. To investigate the potential of myeloid cell polarization in a primitive vertebrate species, we phenotypically and functionally characterized myeloid cells of common carp (Cyprinus carpio L.) during culture.

Biocomplexity in a highly migratory pelagic marine fish, Atlantic herring.

The existence of biologically differentiated populations has been credited with a major role in conferring sustainability and in buffering overall productivity of anadromous fish population complexes where evidence for spatial structure is uncontroversial. Here, we describe evidence of correlated genetic and life history (spawning season linked to spawning location) differentiation in an abundant and highly migratory pelagic fish, Atlantic herring, Clupea harengus, in the North Sea (NS) and adjacent areas. The existence of genetically and phenotypically diverse stocks in this region despite intense seasonal mixing strongly implicates natal homing in this species.

ISAG/IUIS-VIC Comparative MHC Nomenclature Committee report, 2005.

Nomenclature for Major Histocompatibility Complex (MHC) genes and alleles in species other than humans and mice has historically been overseen either informally by groups generating sequences, or by formal nomenclature committees set up by the International Society for Animal Genetics (ISAG). The suggestion for a Comparative MHC Nomenclature Committee was made at the ISAG meeting held in Göttingen, Germany (2002), and the committee met for the first time at the Institute for Animal Health, Compton, UK in January 2003. To publicize its activity and extend its scope, the committee organized a workshop at the International Veterinary Immunology Symposium (IVIS) in Quebec (2004) where it was decided to affiliate with the Veterinary Immunology Committee (VIC) of the International Union of Immunological Societies (IUIS).

Immune functions in crustaceans: lessons from flies.

In recent years insects, notably Drosophila, have emerged as a popular model for studying immune responses to bacterial and fungal pathogens. Due to the availability of the complete genome sequence, genome-wide scans of immune responses have been performed using microarray analyses. These analyses have revealed the presence of two major pathways: Toll and Imd.

Patterns of variability at the major histocompatibility class II alpha locus in Atlantic salmon contrast with those at the class I locus.

In order to investigate the mechanisms creating and maintaining variability at the major histocompatibility (MH) class II alpha (DAA) locus we examined patterns of polymorphism in two isolated Atlantic salmon populations which share a common post-glacial origin. As expected from their common origin, but contrary to the observation at the MH class I locus, these populations shared the majority of DAA alleles: out of 17 sequences observed, 11 were common to both populations. Recombination seems to play a more important role in the origin of new alleles at the class II alpha locus than at the class I locus.

Novel immunoglobulin-like transcripts in teleost fish encode polymorphic receptors with cytoplasmic ITAM or ITIM and a new structural Ig domain similar to the natural cytotoxicity receptor NKp44.

Members of the immunoglobulin superfamily (IgSF) include a group of innate immune receptors located in the leukocyte receptor complex (LRC) and other small clusters such as the TREM/NKp44 cluster. These receptors are characterised by the presence of immunoglobulin domains, a stalk, a transmembrane domain, and a cytoplasmic region containing either an immunoreceptor tyrosine-based inhibitory motif (ITIM) or are linked to an adapter molecule with an activation motif (ITAM) for downstream signalling. We have isolated two carp cDNA sequences encoding receptors in which the extracellular Ig domain structurally resembles the novel V-type Ig domain of NKp44.

Major histocompatibility genes in the Lake Tana African large barb species flock: evidence for complete partitioning of class II B, but not class I, genes among different species.

The 16 African 'large' barb fish species of Lake Tana inhabit different ecological niches, exploit different food webs and have different temporal and spatial spawning patterns within the lake. This unique fish species flock is thought to be the result of adaptive radiation within the past 5 million years. Previous analyses of major histocompatibility class II B exon 2 sequences in four Lake Tana African large barb species revealed that these sequences are indeed under selection.

Rapid evolution of the MH class I locus results in different allelic compositions in recently diverged populations of Atlantic salmon.

We compared major histocompatibility class I allelic diversity in two currently reproductively isolated Atlantic salmon (Salmo salar) populations (Irish and Norwegian) with a common postglacial origin in order to test for among-population differences in allelic composition and patterns of recombination and point mutation. We also examined the evidence for adaptive molecular divergence at this locus by analyzing the rate of amino acid replacement in relation to a neutral expectation. Contrary to our prediction, and in contrast to the situation for other genetic markers, the two populations have almost nonoverlapping sets of major histocompatibility class I alleles.

The molecular evolution of the interleukin-1 family of cytokines; IL-18 in teleost fish.

The cytokine network is an important homeostatic system with potent activities in immune surveillance, growth, developmental and repair processes. Although interleukin-1beta (IL-1beta) is considered a pivotal pro-inflammatory cytokine, merely focussing on its inflammatory role would be too narrow an approach. Elucidation of the human, the mouse and the Fugu rubripes (pufferfish) genome now enables a more comprehensive overview of this cytokine family and its receptors in several vertebrate classes.

Major histocompatibility lineages and immune gene function in teleost fishes: the road not taken.

It has become increasingly clear over the course of the past decade that the immune system genes of teleosts and tetrapods are plainly derived from common ancestral genes. The last 5 years, however, have also made it abundantly clear that in the teleost genome some of these genes are organized in a manner very different from that seen in mammals. These differences are probably the result of differences in life history traits, such as fecundancy, within each group of species when faced with an evolutionary fork in the road shortly after their divergence from each other.

Analysis of genomic and expressed major histocompatibility class Ia and class II genes in a hexaploid Lake Tana African 'large' barb individual (Barbus intermedius).

Expression of too many co-dominant major histocompatibility complex (MHC) alleles is thought to be detrimental to proper functioning of the immune system. Polyploidy of the genome will increase the number of expressed MHC genes unless they are prone to a silencing mechanism. In polyploid Xenopus species, the number of MHC class I and II genes has been physically reduced, as it does not increase with higher ploidy genomes.

Differential expression and haplotypic variation of two interleukin-1beta genes in the common carp (Cyprinus carpio L.).

Interleukin-1beta (IL-1beta) is a central component in innate immunity and the inflammatory response of mammals. Only recently, the first non-mammalian IL-1beta sequences were published. In this study, we describe a second IL-1beta sequence (IL-1beta2) in carp with 74% amino acid identity to the carp IL-1beta1 sequence.

MHC polymorphism and disease resistance in Atlantic salmon (Salmo salar); facing pathogens with single expressed major histocompatibility class I and class II loci.

Few studies have yet addressed the functional aspects of MHC molecules in fish. To lay the foundation for this, we evaluated the association between disease resistance and MHC class I and class II polymorphism in Atlantic salmon. Standardized disease challenge trials were performed on a semi-wild Atlantic salmon population with subsequent MHC typing and statistical analysis.