Identification of a human immunodominant B-cell epitope within the GRA1 antigen of Toxoplasma gondii by phage display of cDNA libraries

Excreted secreted antigens of the protozoan parasite Toxoplasma gondii play a key role in stimulating the host immune system during acute and chronic infection. With the aim of identifying the immunodominant epitopes of T. gondii antigens involved in the human B-cell response against the parasite, we employed a novel immunological approach. A library of cDNA fragments from T. gondii tachyzoites was displayed as fusion proteins to the amino-terminus of lambda bacteriophage capsid protein D. The lambdaD-tachyzoite library was then affinity-selected by using a panel of sera of pregnant women, all infected with the parasite. Some of the clones identified through this procedure matched the sequence of the dense granule GRA1 protein (p24), allowing us to identify its antigenic regions. In particular, the analysis of human antibody response against the recombinant GRA1 antigen fragments revealed the existence of an immunodominant epitope (epi-24 peptide).     

Cerebral Circulation Time is Prolonged and Not Correlated with EDSS in Multiple Sclerosis Patients: A Study Using Digital Subtracted Angiography

Literature has suggested that changes in brain flow circulation occur in patients with multiple sclerosis. In this study, digital subtraction angiography (DSA) was used to measure the absolute CCT value in MS patients and to correlate its value to age at disease onset and duration, and to expand disability status scale (EDSS). DSA assessment was performed on eighty MS patients and on a control group of forty-four age-matched patients. CCT in MS and control groups was calculated by analyzing the angiographic images. Lesion and brain volumes were calculated in a representative group of MS patients. Statistical correlations among CCT and disease duration, age at disease onset, lesion load, brain volumes and EDSS were considered. A significant difference between CCT in MS patients (mean = 4.9s; sd = 1.27s) and control group (mean = 2.8s; sd = 0.51s) was demonstrated. No significant statistical correlation was found between CCT and the other parameters in all MS patients. Significantly increased CCT value in MS patients suggests the presence of microvascular dysfunctions, which do not depend on clinical and MRI findings. Hemodynamic changes may not be exclusively the result of a late chronic inflammatory process.     

The antiapoptotic OPA1/Parl couple participates in mitochondrial adaptation to heat shock

The mitochondria-shaping protein optic atrophy 1 (OPA1) has genetically distinguishable roles in mitochondrial morphology and apoptosis. The latter depends on the presenilin associated rhomboid like (PARL) protease, essential for the accumulation of a soluble intermembrane space form of OPA1 (IMS-OPA1). Here we show that OPA1 and PARL participate in the heat shock response, a stereotypical cellular process of adaptation to thermal stress. Upon heat shock, long forms of OPA1 are lost and mitochondria fragment. However, mitochondrial fusion is dispensable to maintain viability, whereas IMS-OPA1 is required. Upon conditioning-a process of mild heat shock and recovery-IMS-OPA1 accumulates, OPA1 oligomers increase and mitochondria release less cytochrome c, ultimately resulting in cellular resistance to subsequent apoptotic inducers. In Parl(-/-) cells accumulation of IMS-OPA1 is blunted and conditioning fails to protect from cytochrome c release and apoptosis. Thus, the OPA1/PARL dependent pathway of cristae remodeling is implicated in heat shock. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).     

Different DNA repair strategies to combat the threat from 8-oxoguanine

Oxidative DNA damage is one of the most common threats to genome stability and DNA repair enzymes provide protection from the effects of oxidized DNA bases. In mammalian cells, base excision repair (BER) mediated by the OGG1 and MYH DNA glycosylases prevents the accumulation of 8-oxoguanine (8-oxoG) in DNA. When steady-state levels of DNA 8-oxoG were measured in myh(-/-) and myh(-/-)/ogg1(-/-) mice, an age-dependent accumulation of the oxidized purine was found in lung and small intestine of doubly defective myh(-/-)/ogg1(-/-) mice. Since there is an increased incidence of lung and small intestinal cancer in myh(-/-)/ogg1(-/-) mice, these findings are consistent with a causal role for unrepaired oxidized DNA bases in cancer development. We previously presented in vitro evidence that mismatch repair (MMR) participates in the repair of oxidative DNA damage and msh2(-/-) mouse embryo fibroblasts also have increased steady state levels of DNA 8-oxoG. To investigate whether DNA 8-oxoG also accumulates in vivo, basal levels were measured in several organs of 4-month-old msh2(-/-) mice and their wild-type counterparts. Msh2(-/-) mice had significantly increased levels of DNA 8-oxoG in spleen, heart, liver, lung, kidney and possibly small intestine but not in bone marrow, thymus or brain. The tissue-specificity of DNA 8-oxoG accumulation in msh2(-/-) and other DNA repair defective mice suggests that DNA protection of different organs is mediated by different combinations of repair pathways.     

Protein kinase B/Akt is present in activated form throughout the entire replicative cycle of deltaU(S)3 mutant virus but only at early times after infection with wild-type herpes simplex virus 1

The product of the herpes simplex virus 1 (HSV-1) US3 gene is a multifunctional serine-threonine protein kinase that can block apoptosis induced by proapoptotic cellular proteins, exogenous agents, or replication-defective viruses. Earlier studies showed that the U(S)3 kinase activates and functionally overlaps cellular protein kinase A (PKA). In this study we examined the status of phosphatidylinositol 3-kinase [PI3K] and of its effector, protein kinase B/Akt (PKB/Akt), a component of a major pathway of mammalian antiapoptotic signaling systems. We report the following. (i) Infection of target cells with HSV-1 induces transient phosphorylation of serine 473 of PKB/Akt early in infection, with a mechanism that is dependent on PI3K. Inhibition of PI3K induced apoptosis in mock-infected or deltaU(S)3 mutant-virus-infected but not in wild-type-virus-infected cells and reduced the accumulation of specific viral gene products, including the U(S)3 protein kinase, but had a marginal effect on virus yields. (ii) At later times after infection, the total amounts of PKB/Akt decreased and phosphorylated PKB/Akt forms disappeared in a U(S)3-dependent and protein phosphatase 2A-independent manner. (iii) Activation of PKA by forskolin did not mediate significant dephosphorylation of PKB/Akt. Our results are consistent with the model that PKB/Akt is activated early in infection and acts to block apoptosis in infected cells prior to the accumulation of U(S)3 protein kinase and that it persists and continues to function as an antiapoptotic protein in the absence of U(S)3 but becomes redundant or even inimical once U(S)3 protein kinase accumulates in effective amounts.     

Functional characterization of a synthetic abscisic acid analog with anti-inflammatory activity on human granulocytes and monocytes

The phytohormone abscisic acid (ABA), in addition to regulating several important physiological functions in plants, is also produced and released by human granulocytes and monocytes where it stimulates cell activities involved in the innate immune response.Here we describe the properties of an ABA synthetic analog that competes with the hormone for binding to human granulocyte membranes and to purified recombinant LANCL2 (the human ABA receptor) and inhibits several ABA-triggered inflammatory functions of granulocytes and monocytes in vitro: chemotaxis, phagocytosis, reactive oxygen species production and release of prostaglandin E₂ (PGE₂) by human granulocytes, release of PGE₂ and of monocyte chemoattractant protein-1 by human monocytes. This observation provides a proof of principle that ABA antagonists may represent a new class of anti-inflammatory agents.     

Diet and feeding patterns in the kipunji (<Emphasis Type=Italic>Rungwecebus kipunji</Emphasis>) in Tanzania’s Southern Highlands: a first analysis

The diet and feeding behaviour of the kipunji (Rungwecebus kipunji) was studied over 45 months, the first dietary analysis for this species. During 9498 h of direct observation of 34 kipunji groups, a list of 122 identified foodplants was recorded. The list represents 60 families, including 64 trees, 30 herbs, 9 climbers, 7 shrubs, 6 lianas, 3 grasses and 3 ferns. Kipunji were observed eating bark, young and mature leaves, ripe and unripe fruits, flowers, pith, seed pods, rhizomes, tubers, shoots and stalks. Invertebrates, fungi, moss, lichen, and soil were also eaten. Macaranga capensis var. capensis, an early successional tree, was the most commonly consumed species, with leaves, leaf stalks, pith, flowers and bark all eaten. We demonstrate that the kipunji is an omnivorous dietary generalist, favouring mature and immature leaves, ripe and unripe fruits and bark in similar proportions, with an almost comparable fondness for leaf stalks and flowers. Kipunji appear to be adaptable foragers able to modify their diet seasonally, being more folivorous in the dry season and more frugivorous in the wet. Whereas more ripe fruit is eaten in the wet season, the proportion of unripe fruit remains similar across the year. The proportion of mature leaves and pith increases throughout the dry season at the expense of ripe fruits and bark, and this may compensate nutritionally for the lack of available dry-season ripe fruits. Relatively more pith is eaten in the dry season, more stalks at the end of the dry and beginning of the wet seasons, and bark consumption increases as the rainfall rises.     

The Putative Mevalonate Diphosphate Decarboxylase from Picrophilus torridus Is in Reality a Mevalonate-3-Kinase with High Potential for Bioproduction of Isobutene

Mevalonate diphosphate decarboxylase (MVD) is an ATP-dependent enzyme that catalyzes the phosphorylation/decarboxylation of (R)-mevalonate-5-diphosphate to isopentenyl pyrophosphate in the mevalonate (MVA) pathway. MVD is a key enzyme in engineered metabolic pathways for bioproduction of isobutene, since it catalyzes the conversion of 3-hydroxyisovalerate (3-HIV) to isobutene, an important platform chemical. The putative homologue from Picrophilus torridus has been identified as a highly efficient variant in a number of patents, but its detailed characterization has not been reported. In this study, we have successfully purified and characterized the putative MVD from P. torridus. We discovered that it is not a decarboxylase per se but an ATP-dependent enzyme, mevalonate-3-kinase (M3K), which catalyzes the phosphorylation of MVA to mevalonate-3-phosphate. The enzyme''s potential in isobutene formation is due to the conversion of 3-HIV to an unstable 3-phosphate intermediate that undergoes consequent spontaneous decarboxylation to form isobutene. Isobutene production rates were as high as 507 pmol min⁻¹ g cells⁻¹ using Escherichia coli cells expressing the enzyme and 2,880 pmol min⁻¹ mg protein⁻¹ with the purified histidine-tagged enzyme, significantly higher than reported previously. M3K is a key enzyme of the novel MVA pathway discovered very recently in Thermoplasma acidophilum. We suggest that P. torridus metabolizes MVA by the same pathway.     

Activation of human ribosomal genes by 5-azacytidine

Cultured human fibroblasts were exposed to 5-azacytidine which inhibits methylation of newly synthesized DNA. A significant increase in the mean number of Ag-stained active nucleolus organizers has been observed in treated cells. This suggests that DNA methylation is involved in modulation of human rRNA synthesis.     

Biomaterials for the programming of cell growth in oral tissues: The possible role of APA

Examples of programmed tissue response after the interaction of cells with biomaterials are a hot topic in current dental research. We propose here the use of anodic porous alumina (APA) for the programming of cell growth in oral tissues. In particular, APA may trigger cell growth by the controlled release of specific growth factors and/or ions. Moreover, APA may be used as a scaffold to promote generation of new tissue, due to the high interconnectivity of pores and the high surface roughness displayed by this material.