Side reactions in the synthesis of phosphotyrosine-containing peptides

Summary A series of phosphopeptides Tyr(PO₃H₂)-Val-Pro-Xxx-Leu (Xxx=Met, Met(O), Nle, Dab or Cys), derived from the native platelet-derived growth factor- receptor (PDGF-) sequence, has been prepared to study their interaction with the src-homology 2 (SH2) domains of the p85 subunit of PI3 kinase. The phosphopeptides were synthesized using Fmoc methodology incorporating N-Boc dibenzyl-protected phosphotyrosine (Boc-Tyr[PO₃(Bzl)₂]) as the N-terminal amino acid, since the benzyl groups can be removed during resin cleavage with TFA. Only peptides containing methionine were found to exist partially as S-benzyl sulfonium salts after TFA cleavage from the resin. The desired peptide could be obtained from the S-benzyl sulfonium salt by hydrogenolysis.     

Identifying historical and future global change drivers that place species recovery at risk

Ecosystem management in the face of global change requires understanding how co-occurring threats affect species and communities. Such an understanding allows for effective management strategies to be identified and implemented. An important component of this is differentiating between factors that are within (e.g. invasive predators) or outside (e.g. drought, large wildfires) of a local manager's control. In the global biodiversity hotspot of south-western Australia, small- and medium-sized mammal species are severely affected by anthropogenic threats and environmental disturbances, including invasive predators, fire, and declining rainfall. However, the relative importance of different drivers has not been quantified. We used data from a long-term monitoring program to fit Bayesian state-space models that estimated spatial and temporal changes in the relative abundance of four threatened mammal species: the woylie (Bettongia penicillata), chuditch (Dasyurus geoffroii), koomal (Trichosurus vulpecula) and quenda (Isoodon fusciventor). We then use Bayesian structural equation modelling to identify the direct and indirect drivers of population changes, and scenario analysis to forecast population responses to future environmental change. We found that habitat loss or conversion and reduced primary productivity (caused by rainfall declines) had greater effects on species' spatial and temporal population change than the range of fire and invasive predator (the red fox Vulpes vulpes) management actions observed in the study area. Scenario analysis revealed that a greater extent of severe fire and further rainfall declines predicted under climate change, operating in concert are likely to further reduce the abundance of these species, but may be mitigated partially by invasive predator control. Considering both historical and future drivers of population change is necessary to identify the factors that risk species recovery. Given that both anthropogenic pressures and environmental disturbances can undermine conservation efforts, managers must consider how the relative benefit of conservation actions will be shaped by ongoing global change.     

The B-cell response in lymphoid tissue of mice immunized with various antigenic forms of the influenza virus hemagglutinin.

Protection of BALB/c (H-2d) mice against secondary challenge with influenza A viruses is primarily dependent on appropriate recognition of the hemagglutinin (HA) molecule by effectors of humoral immunity, the B lymphocytes and their product the immunoglobulin molecules. The influence of the antigenic form of the HA in eliciting protective antibodies is not clearly defined. We directly monitored the kinetics, character, localization, and helper T-cell dependence of the primary antibody-forming cell (AFC) response and the development of B-cell memory in lymphoid tissues associated with the upper and lower respiratory tracts, and in the spleen and bone marrow, to three forms of HA with various degrees of antigenic organization. Our results show that the antigenic organization of HA substantially influences B-cell immunity, namely, the capacity to generate both primary AFCs and memory B cells responsive to lethal challenge. Immunization by infection is the most efficient means of generating protective memory B cells, in contrast to subunit vaccine. The data also indicate that memory AFCs are predominantly localized to the regional lymphoid tissue where challenge HA is found, unlike primary AFCs, which are restricted to the priming site and which require in vivo CD4+ T-cell help.     

Isolation of arboviruses from insects collected at Beatrice Hill, Northern Territory of Australia, 1974-1976

Between October 1974 and May 1976, 57 596 mosquitoes, 169 957 Culicoides, 5923 Lasiohelea and 1043 phlebotomines were collected for virus isolation at Beatrice Hill (lat. 12 degrees 39'S.,long. 131 degrees 20'E.) in the Northern Territory of Australia. A total of 94 viruses belonging to 22 different serological groupings was isolated. The following species of insect yielded viruses which were identified and those viruses marked with an asterisk represent a new record of insect host: Culex annulirostris: Ross River, Kokobera, Barmah Forest, Corriparta, Eubenangee*, Wongorr; Anopheles amictus: Mapputta*; An bancroftii: bovine ephemeral fever*; An farauti: Eubenangee*; An annulipes: Mapputta; Culicoides marksi: Barmah Forest*, Belmont, Eubenangee*, Wallal, Warrego, Leanyer*, Parker's Farm*, Humpty Doo*; C. peregrinus: Beatrice Hill*; C. oxystoma: Bunyip Creek*, Marrakai*; C. pallidothorax: Wongorr*; C. histrio: Thimiri*; Lasiohelea spp.: Humpty Doo*. Pools of mixed species of Culicoides yielded bluetongue, Belmont, CSIRO Village, Warrego and Facey's Paddock viruses. Filter-passing agents not yet identified, were isolated from Cx annulirostris and An bancroftii. As well as providing new locality records for all but one of the 22 viruses isolated, the study yielded five new viruses (bluetongue serotype 20, CSIRO Village, Marrakai, Beatrice Hill and Humpty Doo viruses) and a new record for Thimiri virus which had not been recorded previously in Australia nor had it been isolated from an arthropod. Nine of the viruses isolated occur in more than one family of Diptera.     

A monoclonal antibody to viral glycoprotein blocks virus-immune effector T cells operating at H-2Dd but not at H-2Kd1.

A particular monoclonal antibody that binds to the influenza virus HA molecule inhibits HA-specific thymus-derived lymphocytes mediating cytotoxicity in the context of H-2Dd but not of H-2Kd. Another monoclonal antibody blocks both sets of HA-specific effector T cells. This observation, together with related findings from other laboratories, is considered to support the idea that T cell recognition is directed against some association of viral and H-2 glycoproteins, as proposed in the original formulation of the "altered self" concept.     

The isolation of Saumarez Reef virus, a new flavivirus, from bird ticks Ornithodoros capensis and Ixodes eudyptidis in Australia.

Strains of a new flavivirus, for which the name Saumarez Reef Virus is proposed, were isolated from seabird ticks collected from four localities. Two strains were isolated from ticks of the species Ornithodoros capensis Neumann 1901 collected from the nests of Sooty Terns, Sterna fuscata Linnaeus 1766 on coral cays off the east coast of Queensland, Australia. The other three strains were isolated from ticks of the species Ixodes eudyptidis Maskell 1885 taken from two dead Silver Gulls Larus novaehollandiae Stephens 1826 in northern Tasmania. The new virus was compared serologically with 50 other flaviviruses at the Yale Arbovirus Research Unit and was found to be most closely related to Tyuleniy virus.     

Immune responses to the 18-kDa protein of Mycobacterium leprae. Similar B cell epitopes but different T cell epitopes seen by inbred strains of mice.

Antibody responses to the 18-kDa protein of Mycobacterium leprae have been analyzed in different strains of mice. High, intermediate, and low responder strains have been identified and these response patterns show clear linkage to genes encoded in the H-2 complex. Three peptides, residues 1-50, 51-100, and 101-148 have been synthesized, as well as a series of 20-mer peptides, which span the entire 18-kDa protein. Repeated immunization of different strains of mice with the 18-kDa protein resulted in IgG responses to epitopes found on all three synthetic peptides. Immunization of BALB/cJ and B10.BR mice, two high responder strains, with 18-kDa protein resulted in high levels of IgG antibody to epitopes found on peptides 1-20, 16-35, 31-50, 46-65, and 76-95. B10.BR mice also contained IgG that bound peptide 61-80 and BALB/cJ mice produced IgG that bound peptide 91-110. Although B10.BR mice produced IgG that bound the 50-mer peptide 101-148, this IgG was not detected by binding to peptides 91-110, 106-125, 121-140, and 131-148. Immunization of B10.BR mice with individual overlapping 20-mer peptides as Ag revealed that peptides 1-20, 16-35, 31-50, and 76-95 elicited high titers of IgG that bound both the immunizing peptide as well as 18-kDa protein. As these peptides induce antibody synthesis they must contain both B cell and T cell epitopes. By contrast, immunization of BALB/cJ mice with the same 20-mer peptides, all of which contain B cell epitopes for this strain, failed to elicit IgG responses with one exception. Peptide 91-110 induced IgG that bound peptide 91-110, but not the intact 18-kDa protein. We conclude that peptides 1-20, 16-35, 31-50, and 76-95 either lack T cell epitopes for BALB/cJ mice, or activate different T cell subpopulations in the two strains. We suggest that the induction of IgG responses to small peptide Ag is an in vivo assay of the activity of Th2 cell subpopulations.     

Ganglioside modulation of neural cell adhesion molecule and N-cadherin- dependent neurite outgrowth

We have used monolayers of control 3T3 cells and 3T3 cells expressing transfected human neural cell adhesion molecule (NCAM) or chick N-cadherin as a culture substrate for PC12 cells. NCAM and N-cadherin in the monolayer directly promote neurite outgrowth from PC12 cells via a G-protein-dependent activation of neuronal calcium channels. In the present study we show that ganglioside GM1 does not directly activate this pathway in PC12 cells. However, the presence of GM1 (12.5-100 micrograms/ml) in the co-culture was associated with a potentiation of NCAM and N-cadherin-dependent neurite outgrowth. Treatment of PC12 cells with GM1 (100 micrograms/ml) for 90 min led to trypsin-stable increases in both beta-cholera toxin binding to PC12 cells and an enhanced neurite outgrowth response to N-cadherin. The ganglioside response could be fully inhibited by treatment with pertussis toxin. These data are consistent with exogenous gangliosides enhancing neuritic growth by promoting cell adhesion molecule-induced calcium influx into neurons.     

Characteristics of secondary cytotoxic T-cell responses in mice infected with influenza A viruses.

The cytotoxic T-cell response in mice infected with type A influenza viruses is dominated by a highly cross-reactive component. Previous experiments showed that after primary immunization the cytotoxic T-cell response apparently consists of a small but significant portion which is specific for the immunizing virus, and a larger component which is highly cross-reactive among all A strain viruses. The present study concentrates on the specificity of the T-cell response after secondary stimulation, using various combinations of type A virus strains. The underlying rationale was to determine whether there was any discernable pattern in the T-cell response which parallels the serologically defined antigenic pattern of influenza.That a virus strain-specific set of precursors does exist was evident in the primary response and even more so upon secondary challenge with the homologous virus (using an adoptive transfer protocol). However, upon secondary challenge with a heterologous influenza virus, this specific component was not evident no matter how closely related serologically the two challenge viruses were. No obvious relationships could be found between serologically defined antigenic patterns and the capacity to stimulate a secondary T-cell response specific for a particular type A influenza virus.