Dendritic Cell-Mediated-Immunization with Xenogenic PrP and Adenoviral Vectors Breaks Tolerance and Prolongs Mice Survival against Experimental Scrapie

In prion diseases, PrPc, a widely expressed protein, is transformed into a pathogenic form called PrPSc, which is in itself infectious. Antibodies directed against PrPc have been shown to inhibit PrPc to PrPSc conversion in vitro and protect in vivo from disease. Other effectors with potential to eliminate PrPSc-producing cells are cytotoxic T cells directed against PrP-derived peptides but their ability to protect or to induce deleterious autoimmune reactions is not known. The natural tolerance to PrPc makes difficult to raise efficient adaptive responses. To break tolerance, adenovirus (Ad) encoding human PrP (hPrP) or control Ad were administered to wild-type mice by direct injection or by transfer of Ad-transduced dendritic cells (DCs). Control Ad-transduced DCs from Tg650 mice overexpressing hPrP were also used for immunization. DC-mediated but not direct administration of AdhPrP elicited antibodies that bound to murine native PrPc. Frequencies of PrP-specific IFNγ-secreting T cells were low and in vivo lytic activity only targeted cells strongly expressing hPrP. Immunohistochemical analysis revealed that CD3+ T cell infiltration was similar in the brain of vaccinated and unvaccinated 139A-infected mice suggesting the absence of autoimmune reactions. Early splenic PrPSc replication was strongly inhibited ten weeks post infection and mean survival time prolonged from 209 days in untreated 139A-infected mice to 246 days in mice vaccinated with DCs expressing the hPrP. The efficacy appeared to be associated with antibody but not with cytotoxic cell-mediated PrP-specific responses

In vitro propagation of Araucaria cunninghamii and other species of the araucariaceae via axillary meristems

Stem segments with 3-5 leaf axils, excised from the upper portion of the mainstem of 2-year-old hoop pine (Araucaria cunninghamii Aiton ex D. Don) seedlings, produced orthotropic buds from the concealed axillary meristems when cultured on a basal medium (BM) of half-strength Murashige and Skoog (MS) inorganic salts, the medium level of growth factors and amino acids of de Fossard, 20 g L sucrose and 6.5 g/L agar. This procedure was also successful with A. balansae, A. bidwillii, A. colurnnaris, A. hunsteinri, A. luxurians, A. montana, A. rulei, A. scopulorum and Agathis robusta and with stem segments from orthotropic coppice shoots of juvenile morphology collected from the stumps of 20-year old hoop pines felled near ground level. The hoop pine explants were highly sensitive to cytokinin; 1 µM and 10 µM 6-benzylaminopurine caused the formation of distorted buds and total inhibition of bud development respectively. Lofier concentrations (0.001-0.1 µM) did not noticeably influence bud formation or development. A low rate of multiplication was induced by reculturing the stem segments after the excision of the initial shoots. New buds developed in the leaf axils of that part of the initial shoot which remained attached to the primary stem explant. Shoots derived from seedling and coppice cultures of hoop pine and seedling cultures of Agathis robusta rooted in vitro on BM + 0.1-10.0 µM indole-3-butyric acid (IBA), but with only 5-20% success. Up to 80% rooting was obtained if both hoop pine shoot types (i. e. from seedling and coppice cultures) were cultured on modified BM (quarter strength MS salts, 10 µM IBA plus no agar) for 2 weeks, before being transferred to a mixture of non-sterile peat and perlite or vermiculite and perlite, maintained under a high humidity (90-95%). Plantlets were subsequently transferred to normal glasshouse conditions and then to the field with less than 5% mortality. Thus hoop pine can be added to the relatively small number of conifers for which the capacity to micropropagate juvenile and mature plants and successfully establish their clones in the field has been demonstrated

Correlations between pure and hybrid combining abilities for slash pine parents

Four trials were analysed to provide taxa comparisons for growth and stem quality as well as genetic parameters for Queensland bred Pinus elliottii (Pee) and P. elliottii × P. caribaea var. hondurensis (Pch) F1 hybrids. Of particular interest was the genetic correlation between related progenies in pure species and hybrid combination (rph), or equivalently the correlation between the general combining ability (GCA) and general hybridising ability (GHA). Pee families produced less volume than either the PCH controls or the F1 hybrid families and exhibited slightly more crown defects than either of the other two taxa. The heritability estimates were very high for the F1 hybrid trials but moderate to low in the pure Pee trials. Type-B genetic correlations were high within the same taxa giving further evidence of the low levels of genotype by environment interaction found within southeast Queensland for these two taxa. Pearson correlations between univariate GCA and GHA estimates provided similar rph estimates to those obtained directly from multivariate analyses. There was no correlation between the GHA and GCA estimates for the 56 Pee parents represented in this study for growth traits; however, a high and positive correlation was found for straightness. While straightness in hybrids may be selected for using pure Pee progeny trial data, growth traits in pure and hybrid progeny of Pee appear to be uncorrelated. Field testing of F1 hybrid families or poly-crossed Pee parents prior to operational deployment or inclusion in more intensive clonal screening programs will continue to be necessary if resources are to be focused on the very best hybrid families

Phylogenetic position of hoop pine (Araucaria cunninghamii)

A variety of gymnosperms (13 species of conifer from 5 families and 2 species of non-conifer) were collected and the small ribosomal subunit (18S rRNA) was sequenced by direct sequencing. Fifteen species were examined in the study, which included widely separated provenances of Araucaria cunninghamii, to determine the phylogenetic relationship of these gymnosperms. Two of the four conifer families found in Australia that were included in the study (Araucariaceae and Podocarpaceae) separated as expected with further separation of genera and species within these families. Homologies between the gymnosperms varied from 89% to 98%. Four geographically distinct groups within A. cunninghamii were separated phylogenetically. This study suggests that A. cunninghamii was the most recent Araucaria species to evolve, with the Papua New Guinean provenances undergoing the fastest evolutionary changes. This type of analysis has provided molecular evidence to support the taxonomy of the Coniferales. It has shown, contrary to an established understanding in angiosperms, that sequence information of the 18S rRNA genes provides a useful means of studying phylogeny in the gymnosperms at the species and within-species levels

Genetic parameters for F1 hybrids of Pinus caribaea var. hondurensis with both Pinus oocarpa and Pinus tecunumanii

Genetic parameters were estimated from 5-year data collected in two 11 x 6 factorial matings, one between Pinus caribaea var. hondurensis Barr. & Golf. (PCH) and Pinus oocarpa Schiede (Pooc) and the other between PCH and Pinus tecunumanii (Schw.) Eguiluz et Ferry (PTEC), that were planted on two sites in Queensland, Australia. The data were also used to predict the general hybridizing ability (GHA) of the 11 PCH parents common to the POOC and PTEC factorials. Genetic parameter estimates obtained from an across-sites analysis were generally of similar magnitude in the two different hybrids. Unbiased heritability estimates from the across-sites analysis were usually intermediate between those obtained from the analysis of the data from the single sites, and estimates from the female (PCH) and male (POOC or PTEC) parents were often substantially different. Type B genetic correlations (r(gB)) between the same trait measured in the two tests were high (ranging from 0.76 to 0.95) for all traits except DBH of the Pea x PTEC hybrids (r(gB)=0.36). Estimates of r(gB) for DBH from the female parents were generally higher than estimates for PCH between pairs of tests in these same locations, while estimates for DBH of the PCH x PTEC hybrids are similar to estimates for height in pairs of PTEC tests grown in different countries. The ratio of additive to dominance variance was 1.4 for diameter, but all other traits showed relatively little dominance variance. The ranking of the 11 PCH parents based on the GHA predictions was very similar in both the Pooc and PTEC hybrid crosses for traits that were controlled primarily by additive variance (i.e., straightness and wind-firmness, where correlations between the two sets of breeding values exceeded 0.92); however, for diameter the correlation was low (r=0.45) and not significant(at the p=0.05 level). The implications of these results are discussed in relation to the genetic improvement of hybrids