Audun Helge Nerland

Human T-cell clones recognize a major M. leprae protein antigen expressed in E. coli

Leprosy is a chronic infectious disease caused by Mycobacterium leprae. As with other intracellular parasites, protective immunity is dependent on T cells and cell-mediated immunity1. In animal models, immunization with killed armadillo-derived M. leprae elicits strong T-cell responses, delayed-type hypersensitivity and protection against viable challenge2–5. We have recently shown that killed M. leprae can induce delayed-type hypersensitivity in healthy human volunteers6. Identification of the M. leprae antigens that are recognized by T cells and may be involved in protection has been hampered by the inability to cultivate the organism in vitro and by difficulties in antigen purification from limited quantities of armadillo-derived bacillus. Because genes for the major protein antigens of M. leprae as seen by mouse monoclonal antibodies have been isolated7,8, it has become possible to test whether these individual antigens are recognized by T cells. We screened crude λ gtll phage lysates of Escherichia coli containing individual M. leprae antigens using M. leprae-specific T-cell clones isolated from M. leprae-vaccinated volunteers. Using this method, we find that nearly half of the M. leprae-specific T-cell clones are stimulated to proliferate by lysates containing an epitope of a M. leprae protein of relative molecular mass 18,000 (18K).

A DNA vaccine directed against a rainbow trout rhabdovirus induces early protection against a nodavirus challenge in turbot.

A DNA vaccine encoding the envelope glycoprotein from a fish rhabdovirus, viral hemorrhagic septicemia virus (VHSV), has previously been shown to induce both early and long time protection against the virus in rainbow trout. Challenge experiments have revealed that the immunity established shortly after vaccination is cross-protective against heterologous fish rhabdoviruses. In this study, we show that the DNA vaccine encoding the VHSV glycoprotein also induces early protection against a non-enveloped, positive-sense RNA virus belonging to the Nodavirus family, the Atlantic halibut nodavirus (AHNV). In a vaccine efficacy test using juvenile turbot as model fish, the fish injected with the VHSV vaccine were completely protected against a nodavirus challenge performed 8 days post vaccination, while the cumulative mortality in the control group reached 54%. A DNA vaccine carrying the gene encoding the capsid protein of AHNV revealed no protective properties against the nodavirus challenge. Histological examination of muscle tissue sections from the vaccine injection site showed that the DNA vaccine against VHSV triggered a pronounced inflammatory response in turbot similar to what has earlier been observed in rainbow trout.

Evaluation of potential reference genes for real time RT-PCR studies in Atlantic halibut ( Hippoglossus Hippoglossus L.); during development, in tissues of healthy and NNV-injected fish, and in anterior kidney leucocytes

BackgroundReal time RT-PCR has become an important tool for analyzing gene expression in fish. Although several housekeeping genes have been evaluated in Atlantic halibut (Hippoglossus Hippoglossus L.), appropriate reference genes for low copy mRNA transcripts at the earliest developmental stages have not been identified. No attempts have been reported to identify suitable reference genes in halibut infected with NNV or in stimulated halibut leucocytes. In this study, β-actin1 (ACTB1), elongation factor 1 alpha (EF1A1), hypoxanthine-guanine phosphoribosyltransferase 1 (HPRT1), ribosomal protein L7 (RPL7), tubulin beta 2C (Tubb2C), and ubiquitin-conjugating enzyme (UbcE) were evaluated as reference genes for normalization of real time RT-PCR data during Atlantic halibut development, in tissue of healthy and NNV-infected fish, and in in vivo and in vitro stimulated anterior kidney leucocytes.ResultsThe expression of all six genes was relatively stable from the unfertilized egg until 12 day degrees post fertilization (ddpf). However, none of the selected genes were found to be stably expressed throughout halibut development. The mRNA levels of the six genes increased from 18 ddpf, when zygotic transcription is likely to be activated, and stabilized at different time points. The Excel-based software programs BestKeeper, geNorm, and NormFinder ranked EF1A1 and UbcE as the best candidate reference genes before activation of zygotic transcription, and RPL7 and EF1A1 as the best candidates after hatching. EF1A1 and RPL7 were also listed as the best reference genes when exploring the expression levels of the six genes in various halibut organs, both in non-injected fish and in mock- and NNV-injected fish. None of the reference genes were found optimal for normalization of real time RT-PCR data from in vitro stimulated anterior kidney leucocytes.ConclusionGenerally, it was found that EF1A1 and RPL7 were the genes that showed least variation, with HPRT1 and UbcE as intermediate genes, and ACTB1 and Tubb2C as the least stable ones. None of the six reference genes can be recommended as reference gene candidates in ConA-PMA stimulated leucocytes. However, UbcE can be a good candidate in other experimental setups. This study emphasizes the need for reference gene evaluation, as universal reference genes have not been identified.

Characterisation and expression analysis of the Atlantic halibut (Hippoglossus hippoglossus L.) cytokines: IL-1β, IL-6, IL-11, IL-12β and IFNγ

Genes encoding the five Atlantic halibut (Hippoglossus hippoglossus L.) cytokines; interleukin (IL)-1β, IL-6, IL-11b, IL-12βc, and interferon (IFN) γ, were cloned and characterised at a molecular level. The genomic organisation of the halibut cytokine genes was similar to that seen in mammals and/or other fish species. Several mRNA instability motifs were found within the 3′-untranslated region (UTR) of all cytokine cDNA sequences. The putative cytokine protein sequences showed a low sequence identity with the corresponding homologues in mammals, avian and other fish species. Nevertheless, important structural features were presumably conserved such as the presence, or absence in the case of IL-1β, of a signal peptide, secondary structure and family signature motifs. The relative expression pattern of the cytokine genes was analyzed in several halibut organs, revealing a constitutive expression in both lymphoid and non-lymphoid organs. Interestingly, the gills showed a relatively high expression of IL-1β, IL-12βc and IFNγ. The real time RT-PCR data also showed that the mRNA level of IL-1β, IL-6, IL-12βc and IFNγ was high in the thymus, while IL-11b was relatively highly expressed in the posterior kidney and posterior gut. Moreover, the halibut brain showed a relatively high level of IL-6 transcripts. Anterior kidney leucocytes in vitro stimulated with imiquimod showed a significant increase in mRNA level of the five halibut cytokine genes. The sequence and characterisation data presented here will be useful for further investigation of both innate and adaptive immune responses in halibut, and be helpful in the design of vaccines for the control of various infectious diseases.

Immunological responses of turbot (Psetta maxima) to nodavirus infection or polyriboinosinic polyribocytidylic acid (pIC) stimulation, using expressed sequence tags (ESTs) analysis and cDNA microarrays.

To investigate the immunological responses of turbot to nodavirus infection or pIC stimulation, we constructed cDNA libraries from liver, kidney and gill tissues of nodavirus-infected fish and examined the differential gene expression within turbot kidney in response to nodavirus infection or pIC stimulation using a turbot cDNA microarray. Turbot were experimentally infected with nodavirus and samples of each tissue were collected at selected time points post-infection. Using equal amount of total RNA at each sampling time, we made three tissue-specific cDNA libraries. After sequencing 3230 clones we obtained 3173 (98.2%) high quality sequences from our liver, kidney and gill libraries. Of these 2568 (80.9%) were identified as known genes and 605 (19.1%) as unknown genes. A total of 768 unique genes were identified. The two largest groups resulting from the classification of ESTs according to function were the cell/organism defense genes (71 uni-genes) and apoptosis-related process (23 uni-genes). Using these clones, a 1920 element cDNA microarray was constructed and used to investigate the differential gene expression within turbot in response to experimental nodavirus infection or pIC stimulation. Kidney tissue was collected at selected times post-infection (HPI) or stimulation (HPS), and total RNA was isolated for microarray analysis. Of the 1920 genes studied on the microarray, we identified a total of 121 differentially expressed genes in the kidney: 94 genes from nodavirus-infected animals and 79 genes from those stimulated with pIC. Within the nodavirus-infected fish we observed the highest number of differentially expressed genes at 24 HPI. Our results indicate that certain genes in turbot have important roles in immune responses to nodavirus infection and dsRNA stimulation.

Associations of MHC Class II Alleles in Norwegian Primary Sjogren's Syndrome Patients: Implications for Development of Autoantibodies to the Ro52 Autoantigen

Sjögrens syndrome (SS) is a chronic autoimmune disease characterized by dryness of the eyes and mouth. Currently, the highly polymorphic major histocompatibility complex (MHC) genes are the best documented genetic risk factor for the development of autoimmune disease. We examined the MHC class II alleles DRB1, DRB3, DRB4, DRB5, DQA1 and DQB1 in a group of Norwegian pSS patients and compared with a group of healthy controls. Because a number of studies have shown that some of the MHC class II alleles are not associated with the disease as a whole, but rather to the development of autoantibodies, anti‐Ro52 autoantibodies in serum were measured and compared to MHC class II allele status. A clear association with pSS was detected for the DRB1*0301 and DRB3*0101 alleles, but these alleles were more closely associated with the presence of anti‐Ro52 autoantibodies than with pSS itself. Moreover, the DQA1*0501 and DQB1*0201 alleles were only associated with the presence of anti‐Ro52 autoantibodies. This study shows that the production of anti‐Ro52 autoantibodies in pSS is associated with the DRB1*0301, DRB3*0101, DQA1*0501 and DQB1*0201 alleles which are in strong linkage disequilibrium.

CD8α and CD8β in Atlantic halibut, Hippoglossus hippoglossus: Cloning, characterization and gene expression during viral and bacterial infection

CD8 is expressed on cytotoxic T-cells where it functions as a co-receptor for the TCR by binding to MHC class I proteins that present peptides on the cell surface. In this study we describe the cloning and sequencing of full length cDNAs encoding CD8alpha and CD8beta from Atlantic halibut (Hippoglossus hippoglossus L.) and subsequent isolation and characterization of the CD8alpha and CD8beta genes. The predicted halibut CD8alpha and CD8beta proteins are similar to those of mammals and other fish. Real time RT-PCR revealed that the highest levels of CD8 mRNA were found in the thymus, while some expression was also seen in the spleen, the gills, and the anterior and posterior kidney. In situ hybridization confirmed that the halibut thymus contained numerous CD8alpha and CD8beta expressing cells, while the anterior kidney had no CD8alpha positive cells but only a few CD8beta expressing cells. Only moderate changes in CD8 mRNA expression in other organs during either nodavirus or Vibrio anguillarum infection were observed. Both CD8alpha and CD8beta were significantly (P<0.05) down-regulated in spleen at 48h compared to their levels at 12h post-infection with nodavirus and V. anguillarum.

Cytokine profile during latent and slowly progressive primary tuberculosis: a possible role for interleukin- 15 in mediating clinical disease

Recently, mouse models for latent (LTB) and slowly progressive primary tuberculosis (SPTB) have been established. However, cytokine profiles during the two models are not well established. Using quantitative reverse transcription‐polymerase chain reaction (qRT‐PCR) we studied the expression levels of interleukin (IL)‐2, IL‐4, IL‐10, IL‐12, IL‐15, interferon (IFN)‐γ and tumour necrosis factor (TNF)‐α during the course of LTB and SPTB in the lungs and spleens of B6D2F1Bom mice infected with the H37Rv strain of Mycobacterium tuberculosis (Mtb). The results show that, except for IL‐4, cytokine expression levels were significantly higher during SPTB than LTB in both the lungs and spleens. During LTB, all the cytokines (except IL‐2 in the lungs) had higher expression levels during the initial period of infection both in the lungs and spleens. During SPTB, the expression levels of IL‐15 increased significantly from phases 1 to 3 in the lungs. The expression levels of IL‐10, IL‐12 and IFN‐γ increased significantly from 2 to 3 in the lungs. IL‐10 and IL‐15 increased significantly from phases 2 to 3, whereas that of TNF‐α decreased significantly and progressively from phases 1 to 3 in the spleens. Over‐expression of proinflammatory cytokines during active disease has been well documented, but factor(s) underlying such over‐expression is not known. In the present study, there was a progressive and significant increase in the expression levels of IL‐15, together with Th1 cytokines (IL‐12 and IFN‐γ) during SPTB but a significant decrease during LTB. IL‐15 is known to up‐regulate the production of proinflammatory cytokines, IL‐1β, IL‐8, IL‐12, IL‐17, IFN‐γ and TNF‐α and has an inhibitory effect on activation‐induced cell death. IL‐15 is known to be involved in many proinflammatory disease states such as rheumatoid arthritis, sarcoidosis, inflammatory bowel diseases, autoimmune diabetes, etc. Our results, together with the above observations, suggest that IL‐15 may play an important role in mediating active disease during Mtb infection.

Genomic and Proteomic Analyses Reveal Non–Neofunctionalized Vitellogenins in a Basal Clupeocephalan, the Atlantic Herring, and Point to the Origin of Maturational Yolk Proteolysis in Marine Teleosts

Oocyte hydration is a unique event in oviparous marine teleosts that provides the single-celled egg with an essential pool of water for survival during early development in the saline oceanic environment. A conserved mechanism of maturational yolk proteolysis of a neofunctionalized vitellogenin (VtgAa) has been shown to underlie the hydration event in all teleosts that spawn pelagic eggs (pelagophils), and is argued to be a key adaptation for teleost radiation in the oceanic environment 55 Ma. We have recently shown that a small pool of free amino acids (FAAs) significantly contributes to the osmolarity of the ovulated egg in an ancestral marine teleost, the Atlantic herring that spawns benthic eggs (benthophil). To determine whether multiple forms of vtg exist and whether neofunctionalization of the gene products are related to the egg FAA pool in this species, genomic sequences conserved between the exons of Atlantic herring and zebrafish were amplified. This approach identified a small polymorphic intron between exons 9 and 10 in Atlantic herring and demonstrated that two closely related major vtg transcripts (chvtgAc1 and chvtgAc2) are expressed during oogenesis. A separate polymerase chain reaction-based approach identified a more ancestral phosvitinless transcript (chvtgC). Proteomic analyses of the translated products of the major vtg forms demonstrated that the yolk proteins are similarly processed during deposition, and oocyte maturation and reveal that vtgs have duplicated but not neofunctionalized in this species. Phylogenetic analyses consistently clustered the transcripts and proteins as the basal sister group to the Ostariophysi in full congruence with the Clupeocephalan rank, and suggest that expansion of ostariophysan vtgAo1 and vtgAo2 genes occurred in a lineage-specific manner after separation from the Clupeiformes. Three-dimensional modeling of the ChvtgAc1 sequence against the resolved lamprey lipovitellin module revealed that the tertiary structure is highly conserved, with most substitutions occurring on the outside of the molecule. The data indicate that the phosvitin domain, the smallest yet reported for teleosts, and an N-terminal fragment of the lipovitellin light chain contribute to the FAA pool. The present findings thus show that yolk proteolysis and the generation of an organic osmolyte pool of FAAs was an adaptive response to spawning in seawater also for the Clupeiformes, but that this process was not evolutionarily successful in terms of biodiversity until vtg gene neofunctionalization occurred in the Acanthomorpha.

Ontogeny of lymphoid organs and development of IgM-bearing cells in Atlantic halibut (Hippoglossus hippoglossus L.).

In teleost fish, the head kidney, thymus, and spleen are generally regarded as important immune organs. In this study, the ontogeny of these organs was studied in Atlantic halibut (Hippoglossus hippoglossus), larvae at various stages of development. We observed that the kidney was present at hatching, the thymus at 33days post hatch (dph), while the spleen was the last organ to be detected at 49dph. All three lymphoid organs were morphologically well developed during late metamorphic stages. Real time RT-PCR analysis showed that IgM mRNA expression could be observed at 66dph and later, which correlates well with in situ hybridisation data showing that a few IgM positive cells could be detected in the anterior kidney and spleen from 66dph. Our data also showed that the highest levels of IgM mRNA could be detected in halibut spleen. Immunostaining using a monoclonal antibody against halibut IgM detected IgM positive cells at 94dph in both the head kidney and the spleen, which is much later than the IgM mRNA. Numerous cells expressing both IgM mRNA and protein could be detected in the spleen and anterior kidney and also to some extent in thymus specimens from adult halibut.