Narcolepsy: autoimmunity, effector T cell activation due to infection, or T cell independent, major histocompatibility complex class II induced neuronal loss?

Human narcolepsy with cataplexy is a neurological disorder, which develops due to a deficiency in hypocretin producing neurons in the hypothalamus. There is a strong association with human leucocyte antigens HLA-DR2 and HLA-DQB1*0602. The disease typically starts in adolescence. Recent developments in narcolepsy research support the hypothesis of narcolepsy being an immune-mediated disease. Narcolepsy is associated with polymorphisms of the genes encoding T cell receptor alpha chain, tumour necrosis factor alpha and tumour necrosis factor receptor II. Moreover the rate of streptococcal infection is increased at onset of narcolepsy. The hallmarks of anti-self reactions in the tissue--namely upregulation of major histocompatibility antigens and lymphocyte infiltrates--are missing in the hypothalamus. These findings are questionable because they were obtained by analyses performed many years after onset of disease. In some patients with narcolepsy autoantibodies to Tribbles homolog 2, which is expressed by hypocretin neurons, have been detected recently. Immune-mediated destruction of hypocretin producing neurons may be mediated by microglia/macrophages that become activated either by autoantigen specific CD4(+) T cells or superantigen stimulated CD8(+) T cells, or independent of T cells by activation of DQB1*0602 signalling. Activation of microglia and macrophages may lead to the release of neurotoxic molecules such as quinolinic acid, which has been shown to cause selective destruction of hypocretin neurons in the hypothalamus.

Genetics of male nuptial colour divergence between sympatric sister species of a Lake Victoria cichlid fish

The hypothesis of sympatric speciation by sexual selection has been contentious. Several recent theoretical models of sympatric speciation by disruptive sexual selection were tailored to apply to African cichlids. Most of this work concludes that the genetic architecture of female preference and male trait is a key determinant of the likelihood of disruptive sexual selection to result in speciation. We investigated the genetic architecture controlling male nuptial colouration in a sympatric sibling species pair of cichlid fish from Lake Victoria, which differ conspicuously in male colouration and female mating preferences for these. We estimated that the difference between the species in male nuptial red colouration is controlled by a minimum number of two to four genes with significant epistasis and dominance effects. Yellow colouration appears to be controlled by one gene with complete dominance. The two colours appear to be epistatically linked. Knowledge on how male colouration segregates in hybrid generations and on the number of genes controlling differences between species can help us assess whether assumptions made in simulation models of sympatric speciation by sexual selection are realistic. In the particular case of the two sister species that we studied a small number of genes causing major differences in male colouration may have facilitated the divergence in male colouration associated with speciation.

Monomeric and dimeric IgG fractions show differential reactivity against pathogen-derived antigens

Polyvalent Ig preparations, derived from the pooled plasma of thousands of healthy donors, contain a complex mix of both 'acquired' and natural antibodies directed against pathogens as well as foreign and self/auto antigens (Ag). Depending on their formulation, donor pool size, etc., liquid Ig preparations contain monomeric and dimeric IgG. The dimeric IgG fraction is thought to represent mainly idiotype-antiidiotype Ab pairs. Treatment of all IgG fractions at pH 4 effectively monomerizes the IgG dimers resulting in separated idiotype-antiidiotype Ab pairs and thus in a comparable F(ab')(2) binding site availability of the different IgG fractions. Previously, we identified an increased anti-self-reactivity within the monomerized dimer fraction. This study addressed if, among the different IgG fractions, an analogous preferential reactivity was evident in the response against different pathogen-derived protein and carbohydrate antigens. Therefore, we assessed the activity of total unseparated IgG, the monomeric and dimeric IgG fractions against antigenic structures of bacterial and viral antigens/virulence factors. All fractions showed similar reactivity to protein antigens except for exotoxin A of Pseudomonas aeruginosa, where the dimeric fraction, especially when monomerized, showed a marked increase in reactivity. This suggests that the production of antiidiotypic IgG antibodies contributes to controlling the immune response to certain categories of pathogens. In contrast, the monomeric IgG fractions showed increased reactivity towards pathogen-associated polysaccharides, classically regarded as T-independent antigens. Taken together, the differential reactivity of the IgG fractions seems to indicate a preferential segregation of antibody reactivities according to the nature of the antigen.

In vitro induction of lymph node cell proliferation by mouse bone marrow dendritic cells following stimulation with different Echinococcus multilocularis antigens

The immune response of mice experimentally infected with Echinococcus multilocularis metacestodes becomes impaired so as to allow parasite survival and proliferation. Our study tackled the question on how different classes of E. multilocularis antigens (crude vesicular fluid (VF); purified proteinic rec-14-3-3; purified carbohydrate Em2(G11)) are involved in the maturation process of bone-marrow-derived dendritic cells (BMDCs) and subsequent exposure to lymph node (LN) cells. In our experiments, we used BMDCs cultivated from either naïve (control) or alveolar echinococcosis (AE)-infected C57BL/6 mice. We then tested surface markers (CD80, CD86, MHC class II) and cytokine expression levels (interleukin (IL)-10, IL-12p40 and tumour necrosis factor (TNF)-α) of non-stimulated BMDCs versus BMDCs stimulated with different Em-antigens or lipopolysaccharide (LPS). While LPS and rec-14-3-3-antigen were able to induce CD80, CD86 and (to a lower extent) MHC class II surface expression, Em2(G11) and, strikingly, also VF-antigen failed to do so. Similarly, LPS and rec-14-3-3 yielded elevated IL-12, TNF-α and IL-10 expression levels, while Em2(G11) and VF-antigen didn't. When naïve BMDCs were loaded with VF-antigen, they induced a strong non-specific proliferation of uncommitted LN cells. For both, BMDCs or LN cells, isolated from AE-infected mice, proliferation was abrogated. The most striking difference, revealed by comparing naïve with AE-BMDCs, was the complete inability of LPS-stimulated AE-BMDCs to activate lymphocytes from any LN cell group. Overall, the presenting activity of BMDCs from AE-infected mice seemed to trigger unresponsiveness in T cells, especially in the case of VF-antigen stimulation, thus contributing to the suppression of clonal expansion during the chronic phase of AE infection.

Genetics of GHRH, GHRH-receptor, GH and GH-receptor: its impact on pharmacogenetics

When a child is not following the normal, predicted growth curve, an evaluation for underlying illnesses and central nervous system abnormalities is required and, appropriate consideration should be given to genetic defects causing GH deficiency (GHD). Because Insulin-like-Growth Factor-I (IGF-I) plays a pivotal role, GHD could also be considered as a form of IGF-I deficiency (IGFD). Although IGFD can develop at any level of the GHRH-GH-IGF axis, a differentiation should be made between GHD (absent to low GH in circulation) and IGFD (normal to high GH in circulation). The main focus of this review is on the GH-gene, the various gene alterations and their possible impact on the pituitary gland. However, although transcription factors regulating the pituitary gland development may cause multiple pituitary hormone deficiency they may present initially as GHD. These defects are discussed in various different chapters within this book, whereas, the impact of alterations of the GHRH-, GHRH-receptor- --as well as the GH-receptor (GHR) gene--will be discussed here.

Immune pathomechanism of drug hypersensitivity reactions

Drug hypersensitivity research has progressed enormously in recent years, and a greater understanding of mechanisms has contributed to improved drug safety. Progress has been made in genetics, enabling personalized medicine for certain drugs, and in understanding drug interactions with the immune system. In a recent meeting in Rome, the clinical, chemical, pharmacologic, immunologic, and genetic aspects of drug hypersensitivity were discussed, and certain aspects are briefly summarized here. Small chemicals, including drugs, can induce immune reactions by binding as a hapten to a carrier protein. Park (Liverpool, England) demonstrated (1) that drug haptens bind to protein in patients in a highly restricted manner and (2) that irreversibly modified carrier proteins are able to stimulate CD4(+) and CD8(+) T cells from hypersensitive patients. Drug haptens might also stimulate cells of the innate immune system, in particular dendritic cells, and thus give rise to a complex and complete immune reaction. Many drugs do not have hapten-like characteristics but might gain them on metabolism (so-called prohaptens). The group of Naisbitt found that the stimulation of dendritic cells and T cells can occur as a consequence of the transformation of a prohapten to a hapten in antigen-presenting cells and as such explain the immune-stimulatory capacity of prohaptens. The striking association between HLA-B alleles and the development of certain drug reactions was discussed in detail. Mallal (Perth, Australia) elegantly described a highly restricted HLA-B∗5701-specific T-cell response in abacavir-hypersensitive patients and healthy volunteers expressing HLA-B∗5701 but not closely related alleles. Expression of HLA-B∗1502 is a marker known to be necessary but not sufficient to predict carbamazepine-induced Stevens-Johnson syndrome/toxic epidermal necrolysis in Han Chinese. The group of Chen and Hong (Taiwan) described the possible "missing link" because they showed that the presence of certain T-cell receptor (TCR) clonotypes was necessary to elicit T-cell responses to carbamazepine. The role of TCRs in drug binding was also emphasized by Pichler (Bern, Switzerland). Following up on their "pharmacological interactions of drugs with immune receptors" concept (p-i concept), namely that drugs can bind directly to TCRs, MHC molecules, or both and thereby stimulate T cells, they looked for drug-binding sites for the drug sulfamethoxazole in drug-specific TCRs: modeling revealed up to 7 binding sites on the CDR3 and CDR2 regions of TCR Vα and Vβ. Among many other presentations, the important role of regulatory T cells in drug hypersensitivity was addressed.

HLA-A*3101 and carbamazepine-induced hypersensitivity reactions in Europeans

Carbamazepine causes various forms of hypersensitivity reactions, ranging from maculopapular exanthema to severe blistering reactions. The HLA-B*1502 allele has been shown to be strongly correlated with carbamazepine-induced Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS-TEN) in the Han Chinese and other Asian populations but not in European populations.

Community Genetics Reveal Elevated Levels of Sympatric Gene Flow among Morphologically Similar but Not among Morphologically Dissimilar Species of Lake Victoria Cichlid Fish

We examined genetic structure among five species of Lake Victoria haplochromine cichlids in four island communities, using a full factorial sampling design that compared genetic differentiation between pairs of species and populations of varying morphological similarity and geographical proximity. We found that allopatric conspecific populations were on average significantly more strongly differentiated than sympatric heterospecific populations of morphologically similar species. Allopatric heterospecific populations of morphologically dissimilar species were most differentiated. Our work demonstrates that phenotypic divergence can be maintained and perhaps even evolve in sympatry despite considerable gene flow between species. Conversely, phenotypic resemblance among conspecific populations can be maintained despite geographical isolation. Additionally we show that anthropogenically increased hybridization does not affect all sympatric species evenly but predominantly affects morphologically similar and closely related species. This has important implications for the evolution of reproductive isolation between species These findings are also consistent with the hypothesis of speciation reversal due to weakening of divergent selection and reproductive isolation as a consequence of habitat homogenization and offers an evolutionary mechanistic explanation for the observation that species poor assemblages in turbid areas of the lake are characterized by just one or two species in each of a few morphologically distinct genera.

Bacillus anthracis: Molecular taxonomy, population genetics, phylogeny and patho-evolution

Bacillus anthracis, the etiological agent of anthrax, manifests a particular bimodal lifestyle. This bacterial species alternates between short replication phases of 20-40 generations that strictly require infection of the host, normally causing death, interrupted by relatively long, mostly dormant phases as spores in the environment. Hence, the B. anthracis genome is highly homogeneous. This feature and the fact that strains from nearly all parts of the world have been analysed for canonical single nucleotide polymorphisms (canSNPs) and variable number tandem repeats (VNTRs) has allowed the development of molecular epidemiological and molecular clock models to estimate the age of major diversifications in the evolution of B. anthracis and to trace the global spread of this pathogen, which was mostly promoted by movement of domestic cattle with settlers and by international trade of contaminated animal products. From a taxonomic and phylogenetic point of view, B. anthracis is a member of the Bacillus cereus group. The differentiation of B. anthracis from B. cereus sensu strict, solely based on chromosomal markers, is difficult. However, differences in pathogenicity clearly differentiate B. anthracis from B. cereus and are marked by the strict presence of virulence genes located on the two virulence plasmids pXO1 and pXO2, which both are required by the bacterium to cause anthrax. Conversely, anthrax-like symptoms can also be caused by organisms with chromosomal features that are more closely related to B. cereus, but which carry these virulence genes on two plasmids that largely resemble the B. anthracis virulence plasmids. (C) 2011 Elsevier B.V. All rights reserved.

Effects of housing, perches, genetics, and 25-hydroxycholecalciferol on keel bone deformities in laying hens

Several studies have shown a high prevalence of keel bone deformities in commercial laying hens. The aim of this project was to assess the effects of perch material, a vitamin D feed additive (25-hydroxyvitamin D(3); HyD, DSM Nutritional Products, Basel, Switzerland), and genetics on keel bone pathology. The study consisted of 2 experiments. In the first experiment, 4,000 Lohmann Selected Leghorn hens were raised in aviary systems until 18 wk of age. Two factors were investigated: perch material (plastic or rubber-coated metal) and feed (with and without HyD). Afterward, the hens were moved to a layer house with 8 pens with 2 aviary systems. Daily feed consumption, egg production, mortality, and feather condition were evaluated. Every 6 wk, the keel bones of 10 randomly selected birds per pen were palpated and scored. In the second experiment, 2,000 Lohmann Brown (LB) hens and 2,000 Lohmann Brown parent stock (LBPS) hens were raised in a manner identical to the first experiment. During the laying period, the hens were kept in 24 identical floor pens but equipped with different perch material (plastic or rubber-coated metal). The same variables were investigated as in the first experiment. No keel bone deformities were found during the rearing period in either experiment. During the laying period, deformities gradually appeared and reached a prevalence of 35% in the first experiment and 43.8% in the second experiment at the age of 65 and 62 wk, respectively. In the first experiment, neither HyD nor the aviary system had any significant effect on the prevalence of keel bone deformities. In the second experiment, LBPS had significantly fewer moderate and severe deformities than LB, and rubber-coated metal perches were associated with a higher prevalence of keel bone deformities compared with plastic perches. The LBPS laid more but smaller eggs than the LB. Again, HyD did not affect the prevalence of keel bone deformities. However, the significant effect of breed affiliation strongly indicates a sizeable genetic component that may provide a basis for targeted selection.

Intraperitoneal and intra-nasal vaccination of mice with three distinct recombinant Neospora caninum antigens results in differential effects with regard to protection against experimental challenge with Neospora caninum tachyzoites

Recombinant NcPDI(recNcPDI), NcROP2(recNcROP2), and NcMAG1(recNcMAG1) were expressed in Escherichia coli and purified, and evaluated as potential vaccine candidates by employing the C57Bl/6 mouse cerebral infection model. Intraperitoneal application of these proteins suspended in saponin adjuvants lead to protection against disease in 50% and 70% of mice vaccinated with recNcMAG1 and recNcROP2, respectively, while only 20% of mice vaccinated with recNcPDI remained without clinical signs. In contrast, a 90% protection rate was achieved following intra-nasal vaccination with recNcPDI emulsified in cholera toxin. Only 1 mouse vaccinated intra-nasally with recNcMAG1 survived the challenge infection, and protection achieved with intra-nasally applied recNcROP2 was at 60%. Determination of cerebral parasite burdens by real-time PCR showed that these were significantly reduced only in recNcROP2-vaccinated animals (following intraperitoneal and intra-nasal application) and in recNcPDI-vaccinated mice (intra-nasal application only). Quantification of viable tachyzoites in brain tissue of intra-nasally vaccinated mice showed that immunization with recNcPDI resulted in significantly decreased numbers of live parasites. These data show that, besides the nature of the antigen, the protective effect of vaccination also depends largely on the route of antigen delivery. In the case of recNcPDI, the intra-nasal route provides a platform to generate a highly protective immune response.