Constitutive polymorphic cyanogenesis in the Australian rainforest tree, Ryparosa kurrangii (Achariaceae)

Cyanogenesis, the liberation of volatile hydrogen cyanide from endogenous cyanide-containing compounds, is a proven plant defence mechanism and the particular cyanogens involved have taxonomic utility. The cyclopentenoncyanhydrin glycoside gynocardin was the only cyanogen isolated from foliar tissue of the rare Australian rainforest tree, Ryparosa kurrangii (Achariaceae). Mechanical damage simulating foliar herbivory did not induce a significant increase in the expression of cyanogenesis over a 24h period, indicating cyanogenic herbivore defence in R. kurrangii is constitutive. The cyanogenic potential of mature leaves was quantitatively polymorphic between trees in a natural population, ranging from 0.54 to 4.77 mg CN g(-1) dry wt leaf tissue.     

A Markov chain Monte Carlo strategy for sampling from the joint posterior distribution of pedigrees and population parameters under a Fisher-Wright model with partial selfing

A simple population genetic model is presented for a hermaphrodite annual species, allowing both selfing and outcrossing. Those male gametes (pollen) responsible for outcrossing are assumed to disperse much further than seeds. Under this model, the pedigree of a sample from a single locality is loop-free. A novel Markov chain Monte Carlo strategy is presented for sampling from the joint posterior distribution of the pedigree of such a sample and the parameters of the population genetic model (including the selfing rate) given the genotypes of the sampled individuals at unlinked marker loci. The computational costs of this Markov chain Monte Carlo strategy scale well with the number of individuals in the sample, and the number of marker loci, but increase exponentially with the age (time since colonisation from the source population) of the local population. Consequently, this strategy is particularly suited to situations where the sample has been collected from a population which is the result of a recent colonisation process.     

Efficacy of orally administered praziquantel against Zeuxapta seriolae and Benedenia seriolae (Monogenea) in yellowtail kingfish Seriola lalandi

We investigated the efficacy of praziquantel (PZQ) administered orally to yellowtail kingfish (Seriola lalandi in sea-cage aquaculture in South Australia) against the monogeneans Zeuxapta seriolae and Benedenia seriolae infesting gills and skin, respectively. PZQ was administered to fish by surface-coating feed pellets (Trial 1) or by direct intubation of the stomach (Trial 2). In both trials 4 daily doses were administered: 50 and 75 mg kg(-1) body weight (BW) d(-1) for 6 d, and 100 and 150 mg kg(-1) BW d(-1) for 3 d. Mean parasite intensity was compared between medicated fish and unmedicated control fish. In Trial 1, fish fed lower daily doses of PZQ for 6 d (50 and 75 mg kg(-1) BW d(-1)) had fewer Z. seriolae and B. seriolae than fish fed higher daily doses for 3 d (100 and 150 mg kg(-1) BW d(-1)). Fish rejected feed pellets surface-coated with PZQ, suggesting PZQ affected palatability of feed, and may explain differences in efficacy between treatments. In Trial 2, where PZQ was administered by intubation, there were fewer Z. seriolae and B. seriolae in medicated fish than control fish. Intubated PZQ was also effective against newly recruited Z. seriolae and B. seriolae. PZQ could be developed as a useful treatment for Z. seriolae and B. seriolae parasitising S. lalandi in sea-cage aquaculture if suspected palatability problems are resolved.     

Analysis of the role of bleomycin hydrolase in antigen presentation and the generation of CD8 T cell responses

Long oligopeptides (>10 residues) are generated during the catabolism of cellular proteins in the cytosol. To be presented to T cells, such peptides must be trimmed by aminopeptidases to the proper size (typically 8-10 residues) to stably bind to MHC class I molecules. Aminopeptidases also destroy epitopes by trimming them to even shorter lengths. Bleomycin hydrolase (BH) is a cytosolic aminopeptidase that has been suggested to play a key role in generating MHC class I-presented peptides. We show that BH-deficient cells from mice are unimpaired in their ability to present epitopes from N-extended precursors or whole Ags and express normal levels of MHC class I molecules. Similarly, BH-deficient mice develop normal CD8(+) T cell responses to eight epitopes from three different viruses in vivo. Therefore, BH by itself is not essential for the generation or destruction of MHC class I peptides. In contrast, when BH(-/-) mice are crossed to mice lacking another cytosolic aminopeptidase, leucine aminopeptidase, the resulting BH(-/-)leucine aminopeptidase(-/-) progeny show a selective increase in CD8(+) T cell responses to the gp276 epitope from lymphocytic choriomeningitis virus, whereas the ability to present and respond to several other epitopes is unchanged. Therefore, BH does influence presentation of some Ags, although its role is largely redundant with other aminopeptidases.     

Regulation of Th2 cytokine genes by p38 MAPK-mediated phosphorylation of GATA-3

GATA-3 plays a critical role in allergic diseases by regulating the release of cytokines from Th2 lymphocytes. However, the molecular mechanisms involved in the regulation of GATA-3 in human T lymphocytes are not yet understood. Using small interfering RNA to knock down GATA-3, we have demonstrated its critical role in regulating IL-4, IL-5, and IL-13 release from a human T cell line. Specific stimulation of T lymphocytes by costimulation of CD3 and CD28 to mimic activation by APCs induces translocation of GATA-3 from the cytoplasm to the nucleus, with binding to the promoter region of Th2 cytokine genes, as determined by chromatin immunoprecipitation. GATA-3 nuclear translocation is dependent on its phosphorylation on serine residues by p38 MAPK, which facilitates interaction with the nuclear transporter protein importin-alpha. This provides a means whereby allergen exposure leads to the expression of Th2 cytokines, and this novel mechanism may provide new approaches to treating allergic diseases.     

Murine dendritic cell type I IFN production induced by human IgG-RNA immune complexes is IFN regulatory factor (IRF)5 and IRF7 dependent and is required for IL-6 production

Dendritic cell (DC) activation by nucleic acid-containing IgG complexes is implicated in systemic lupus erythematosus (SLE) pathogenesis. However, it has been difficult to definitively examine the receptors and signaling pathways by which this activation is mediated. Because mouse FcgammaRs recognize human IgG, we hypothesized that IgG from lupus patients might stimulate mouse DCs, thereby facilitating this analysis. In this study, we show that sera and purified IgG from lupus patients activate mouse DCs to produce IFN-alpha, IFN-beta, and IL-6 and up-regulate costimulatory molecules in a FcgammaR-dependent manner. This activation is only seen in sera with reactivity against ribonucleoproteins and is completely dependent on TLR7 and the presence of RNA. As anticipated, IFN regulatory factor (IRF)7 is required for IFN-alpha and IFN-beta production. Unexpectedly, however, IRF5 plays a critical role in IFN-alpha and IFN-beta production induced not only by RNA-containing immune complexes but also by conventional TLR7 and TLR9 ligands. Moreover, DC production of IL-6 induced by these stimuli is dependent on a functional type I IFNR, indicating the need for a type I IFN-dependent feedback loop in the production of inflammatory cytokines. This system may also prove useful for the study of receptors and signaling pathways used by immune complexes in other human diseases.     

Salmonella induces a switched antibody response without germinal centers that impedes the extracellular spread of infection

T-dependent Ab responses are characterized by parallel extrafollicular plasmablast growth and germinal center (GC) formation. This study identifies that, in mice, the Ab response against Salmonella is novel in its kinetics and its regulation. It demonstrates that viable, attenuated Salmonella induce a massive early T-dependent extrafollicular response, whereas GC formation is delayed until 1 mo after infection. The extrafollicular Ab response with switching to IgG2c, the IgG2a equivalent in C57BL/6 mice, is well established by day 3 and persists through 5 wk. Switching is strongly T dependent, and the outer membrane proteins are shown to be major targets of the early switched IgG2c response, whereas flagellin and LPS are not. GC responses are associated with affinity maturation of IgG2c, and their induction is associated with bacterial burden because GC could be induced earlier by treating with antibiotics. Clearance of these bacteria is not a consequence of high-affinity Ab production, for clearance occurs equally in CD154-deficient mice, which do not develop GC, and wild-type mice. Nevertheless, transferred low- and high-affinity IgG2c and less efficiently IgM were shown to impede Salmonella colonization of splenic macrophages. Furthermore, Ab induced during the infection markedly reduces bacteremia. Thus, although Ab does not prevent the progress of established splenic infection, it can prevent primary infection and impedes secondary hemogenous spread of the disease. These results may explain why attenuated Salmonella-induced B cell responses are protective in secondary, but not primary infections.