Natural immunosurveillance against spontaneous, autochthonous breast cancers revealed and enhanced by blockade of IL-13-mediated negative regulation

Introduction We and others previously observed immunosurveillance against transplantable tumors in mice, and enhancement thereof by blockade of negative regulation by T reg cells or the NKT-IL-13-myeloid cell-TGF-β regulatory circuit. However, it was unknown whether natural immunosurveillance inhibits growth of completely spontaneous autochthonous tumors, and whether it can be improved by inhibition of negative regulation. Materials and methods To examine the existence of T cell-mediated immunosurveillance against spontaneous tumors, BALB-neuT mice were treated with anti-CD4 and/or anti-CD8. A role for IL-13 in the suppression of immunosurveillance was investigated by treating mice with IL-13 inhibitor. Results We show that even spontaneous autochthonous breast carcinomas arising in Her-2/neu transgenic mice appear more quickly when the mice are depleted of T cells, evidence for T-cell mediated immunosurveillance slowing tumor growth. This immunosurveillance could be further enhanced by blockade of IL-13 (but not IL-4) which slowed the appearance of these autologous tumors compared to control antibody-treated mice. Conclusion Thus, even completely spontaneous, autochthonous breast cancers can be controlled in part by natural immunosurveillance, and blockade of negative regulation can improve this control. This work was in part supported by the Intramural Research Program of the NIH, National Cancer Institute, Center for Cancer Research.     

Tree spatial patterns and environmental relationships in the forest–alpine tundra ecotone at Niwot Ridge,Colorado, USA

Forest–alpine tundra ecotones (FTEs) are dynamic transition zones between forest and alpine tundra ecosystems that play an important role in regulating ecological processes, which are in turn directly influenced by the spatial patterns of trees and environmental constraints such as topography and climate. Our objectives were to characterize the spatial patterns of tree species and size classes, determine whether spatial patterns of trees differed among three FTE types, and examine FTE- and tree-environmental relationships in our study area on Niwot Ridge, CO, USA. Overall, spatial aggregation was more extensive for seedlings than saplings or trees. Distributions were largely random in limber pine but were highly aggregated in Engelmann spruce and especially subalpine fir, reflecting these species’ relative shade tolerance and expected sequence of establishment following disturbance. Fragmented and patchy tree distributions were observed in the FTE with the most heterogeneous topography, characterized by high relief and associated physical disturbances. The least patchy distributions were associated with the FTE containing a relative absence of disturbance. Intermediate levels of tree aggregation were associated with low topographic relief and presence of meadows and wetlands. Our results emphasize the importance of spatial structure as an initial controlling factor of vegetation pattern in FTEs occurring in the same landscape.     

From PMTCT to a more comprehensive AIDS response for women: a much-needed shift

Half of the 33.2 million people living with HIV today are women. Yet, responses to the epidemic are not adequately meeting the needs of women. This article critically evaluates how prevention of mother-to-child transmission (PMTCT) programs, the principal framework under which women's health is currently addressed in the global response to AIDS, have tended to focus on the prevention of HIV transmission from HIV-positive women to their infants. This paper concludes that more than ten years after their inception, PMTCT programs still do not successfully ensure the adequate treatment, care and support of HIV-infected women. Of particular concern is the continued widespread use of single-dose nevirapine despite World Health Organization recommendations to employ more effective combination therapies that do not potentially jeopardize women's future treatment outcomes. In response, the article calls for a more comprehensive approach that places women's health needs at the centre of AIDS responses. This is critical in settings where the pandemic is generalized and there is a push to greatly expand PMTCT programs, as a more effective and equitable way of meeting the needs of women in the context of HIV. Without such a comprehensive approach, women will continue to be impacted disproportionately by the pandemic, and current strategies for prevention, including PMTCT, and treatment will not be as effective and responsive as they need to be.     

Plasma Levels of Nitrite and Nitrate in Early and Recent Classes of Fish

The stable metabolite of nitric oxide in plasma is NO_x, the sum of nitrite plus nitrate. Measures of plasma NO_x may provide information about the nitric oxide tonus of the entire endothelium including capillary microvessels. Although data are available for mammalian species, plasma NO_x measurements in early vertebrate species are scarce. The purpose of this study was to test the hypothesis that plasma NO_x would be similar to the NO_x in the water environment for fish in early classes (Agnatha and Chondrichthye) and would exceed water NO_x levels in the known nitrite-sensitive fish (Osteichthye). Plasma samples were obtained from 18 species of adult fish (n = 167) and from their housing or natural water environment. NO_x was measured by using chemiluminescence. Plasma NO_x was detected in all species and ranged from 0.5 nmol/ml (skate) to 453.9 nmol/ml (shortnose gar). Average plasma NO_x was significantly higher in sea lamprey than in Atlantic hagfish whereas that of little skate was 3-fold lower than in spiny dogfish shark. Plasma NO_x differed significantly among early bony fish (paddlefish, pallid sturgeon, gar) yet was similar among modern bony fish, with the exception of rainbow trout. Plasma NO_x reflected water NO_x in only 2 species (hagfish and shark), and levels did not coincide with nitrite sensitivity. This study provides an expanded comparative view of plasma NO_x levels across 3 groups of early fish. The data obtained suggest a nitric oxide system in early and modern fish.Abbreviations: NOS, nitric oxide synthaseNitric oxide is generated from oxygen and L-arginine by nitric oxide synthase (NOS), an enzyme with 3 isoforms: constitutive (or endothelial cell), neuronal, and inducible. In mammals, nitric oxide is an important signaling molecule that is responsible for functions in the cardiovascular, nervous, and immune systems.¹⁹ The role that nitric oxide plays as a vasodilator molecule in the peripheral circulation is of particular importance because it serves to regulate vascular tone and total peripheral resistance.⁹Comparative studies focused on nitric oxide provide valuable information about the conserved nature of this ubiquitous molecule. Staining for NADPH-diaphorase (an enzyme equivalent to NOS) or testing for reactivity of vessels isolated from the species of interest have been used to investigate the phylogenetic roots of NOS. Insects^13,20 as well as marine invertebrates, including the horseshoe crab with its copper-containing erythrocytes,²⁶ display NOS activity and produce measurable amounts of nitric oxide. Nitric oxide appears to be responsible for a wide variety of physiology including immune function, growth, development, and neural responses.Nitric oxide is released continuously into surrounding tissues as well as into circulation. From biochemistry studies nitric oxide apparently interacts with platelets and leukocytes²⁸ as well as with hemoglobin inside red blood cells, albeit more slowly than had been thought.³⁴ In addition to their interactions with cells, nitric oxide molecules bind to various proteins in plasma, including albumin, the most abundant protein in circulation.^28,29In vivo, nitric oxide also may exist in its unbound form.²⁷ The region along the vascular wall that remains free of erythrocytes has been suggested as 1 location of unbound nitric oxide with a biologic lifetime in the range of 100 to 500 s.⁶ This length of time allows nitric oxide to affect vessels downstream from its release point, thus performing a hormone-like function.²⁸The stable metabolite of nitric oxide in the plasma portion of blood is referred to as NO_x and is the sum of the oxidative products of nitric oxide, nitrite plus nitrate. Measures of plasma NO_x provide information about chronic basal NOS activity for the entire endothelium including capillary microvessels (accounting for the largest surface area of endothelial cells). Although nitrite appears to reflect acute changes in endothelial cell NOS activity in humans,¹⁴ reports indicate uniformity in both nitrite and NO_x levels across a range of mammalian species,^12,35 likely reflecting similarities in chronic basal NOS activity, that is, nitric oxide tonus.Few studies report measures of NO_x in the plasma of early vertebrate species. Previous work indicated differences in NO_x levels of 8 mammalian species compared with the other vertebrates that were tested.³⁵ One observation from that study was that NO_x was higher and more variable in plasma sampled from fish in the classes Agnatha, Chondrichthye, and Osteichthye. In the present study, the observations were expanded to include plasma NO_x levels for a range of fishes sampled from 3 groups of fish with a spectrum of nitrite sensitivity and from a variety of natural and research housing habitats. Water NO_x levels were measured also. Our hypothesis was that levels of NO_x circulating in plasma would be similar to NO_x in the water environment for fish in the early classes (Agnatha and Chondrichthye) and above water NO_x levels only in the nitrite-sensitive fish of the Osteichthye class. Average NO_x for lamprey, skate, and trout have been published previously.³⁵     

Prevention of rectal SHIV transmission in macaques by daily or intermittent prophylaxis with emtricitabine and tenofovir

Background

In the absence of an effective vaccine, HIV continues to spread globally, emphasizing the need for novel strategies to limit its transmission. Pre-exposure prophylaxis (PrEP) with antiretroviral drugs could prove to be an effective intervention strategy if highly efficacious and cost-effective PrEP modalities are identified. We evaluated daily and intermittent PrEP regimens of increasing antiviral activity in a macaque model that closely resembles human transmission.

Methods and Findings

We used a repeat-exposure macaque model with 14 weekly rectal virus challenges. Three drug treatments were given once daily, each to a different group of six rhesus macaques. Group 1 was treated subcutaneously with a human-equivalent dose of emtricitabine (FTC), group 2 received orally the human-equivalent dosing of both FTC and tenofovir-disoproxil fumarate (TDF), and group 3 received subcutaneously a similar dosing of FTC and a higher dose of tenofovir. A fourth group of six rhesus macaques (group 4) received intermittently a PrEP regimen similar to group 3 only 2 h before and 24 h after each weekly virus challenge. Results were compared to 18 control macaques that did not receive any drug treatment. The risk of infection in macaques treated in groups 1 and 2 was 3.8- and 7.8-fold lower than in untreated macaques (p = 0.02 and p = 0.008, respectively). All six macaques in group 3 were protected. Breakthrough infections had blunted acute viremias; drug resistance was seen in two of six animals. All six animals in group 4 that received intermittent PrEP were protected.

Conclusions

This model suggests that single drugs for daily PrEP can be protective but a combination of antiretroviral drugs may be required to increase the level of protection. Short but potent intermittent PrEP can provide protection comparable to that of daily PrEP in this SHIV/macaque model. These findings support PrEP trials for HIV prevention in humans and identify promising PrEP modalities.     

Pectin structure and biosynthesis

Pectin is structurally and functionally the most complex polysaccharide in plant cell walls. Pectin has functions in plant growth, morphology, development, and plant defense and also serves as a gelling and stabilizing polymer in diverse food and specialty products and has positive effects on human health and multiple biomedical uses. Pectin is a family of galacturonic acid-rich polysaccharides including homogalacturonan, rhamnogalacturonan I, and the substituted galacturonans rhamnogalacturonan II (RG-II) and xylogalacturonan (XGA). Pectin biosynthesis is estimated to require at least 67 transferases including glycosyl-, methyl-, and acetyltransferases. New developments in understanding pectin structure, function, and biosynthesis indicate that these polysaccharides have roles in both primary and secondary cell walls. Manipulation of pectin synthesis is expected to impact diverse plant agronomical properties including plant biomass characteristics important for biofuel production.     

Assessing the risk to nontarget organisms from Bt corn resistant to corn rootworms (Coleoptera: Chrysomelidae): Tier-I testing with Orius insidiosus (Heteroptera: Anthocoridae)

A 14-d continuous dietary exposure bioassay using nymphs of the insidious flower bug, Orius insidiosus (Say) (Heteroptera: Anthocoridae), was conducted to assess nontarget impacts of genetically modified corn event MON 863 expressing the Cry3Bb1 protein for management of corn rootworms, Diabrotica spp. (Coleoptera: Chrysomelidae). Nymphs of O. insidiosus were continuously fed a bee pollen diet inoculated with a maximum hazard exposure dose (930 microg/g of diet) of the Cry3Bb1 protein for 14 d. The Cry3Bb1 protein at a concentration of 930 microg/g of diet had no adverse effect on the survival and development (to adults) of O. insidiosus nymphs. In contrast, when O. insidiosus nymphs were fed bee pollen diet treated with a hazard dose of the protease inhibitor E64 (53 microg/g of diet) or the stomach poison potassium arsenate (8.9 microg/g of diet), all nymphs died before developing to adults. Furthermore, statistical power analysis indicated that at levels of 80% power and a 5% type I error rate, the study design would have been able to detect a minimum 30% reduction in survival of test nymphs and a 20% reduction in nymphal development to the adults relative to the buffer control groups. Based on the maximum level (93 microg/g) of the Cry3Bb1 protein expressed in MON 863 corn tissues including leaves, roots, and pollen, findings from this study indicate that corn hybrids containing the MON 863 event have a minimum 10 times safety factor for nymphs of O. insidiosus and thus pose minimal risk to this beneficial insect.     

Separation of light-induced linear, cyclic and stroma-sourced electron fluxes to P700+ in cucumber leaf discs after pre-illumination at a chilling temperature

Pre-illumination of cucumber leaf discs at 4 degrees C with low-irradiance white light (i) led to a marked decrease in the extent of photo-oxidation of P700 (the special chlorophyll pair in the PSI reaction center) in actinic light at room temperature and (ii) hastened the post-illumination re-reduction of P700+. Quantifying the linear, cyclic and stroma-sourced electron fluxes to P700+ in two actinic light regimes, we found that there was no increase in cyclic or linear electron fluxes to account for these changes. Rather, we observed a decrease in the maximum extent of P700 photo-oxidation assayed by a strong flash superimposed on continuous, background light of wavelength 723 nm, which we interpret to represent a loss of stable charge separation in PSI due to enhanced charge recombination as a result of the pre-illumination treatment. The funneling of electrons towards fewer non-damaged PSI complexes could explain the hastened post-illumination re-reduction of P700+, aided by a slight increase in a stroma-sourced electron flux after prolonged pre-illumination at 4 degrees C. Quantifying the separate fluxes to P700+ helps to elucidate the effects of chilling of cucumber leaf discs in the light and the reasons for the hastened post-illumination re-reduction of P700+.     

An Arabidopsis purple acid phosphatase with phytase activity increases foliar ascorbate

Ascorbate (AsA) is the most abundant antioxidant in plant cells and a cofactor for a large number of key enzymes. However, the mechanism of how AsA levels are regulated in plant cells remains unknown. The Arabidopsis (Arabidopsis thaliana) activation-tagged mutant AT23040 showed a pleiotropic phenotype, including ozone resistance, rapid growth, and leaves containing higher AsA than wild-type plants. The phenotype was caused by activation of a purple acid phosphatase (PAP) gene, AtPAP15, which contains a dinuclear metal center in the active site. AtPAP15 was universally expressed in all tested organs in wild-type plants. Overexpression of AtPAP15 with the 35S cauliflower mosaic virus promoter produced mutants with up to 2-fold increased foliar AsA, 20% to 30% decrease in foliar phytate, enhanced salt tolerance, and decreased abscisic acid sensitivity. Two independent SALK T-DNA insertion mutants in AtPAP15 had 30% less foliar AsA and 15% to 20% more phytate than wild-type plants and decreased tolerance to abiotic stresses. Enzyme activity of partially purified AtPAP15 from plant crude extract and recombinant AtPAP15 expressed in bacteria and yeast was highest when phytate was used as substrate, indicating that AtPAP15 is a phytase. Recombinant AtPAP15 also showed enzyme activity on the substrate myoinositol-1-phosphate, indicating that the AtPAP15 is a phytase that hydrolyzes myoinositol hexakisphosphate to yield myoinositol and free phosphate. Myoinositol is a known precursor for AsA biosynthesis in plants. Thus, AtPAP15 may modulate AsA levels by controlling the input of myoinositol into this branch of AsA biosynthesis in Arabidopsis.     

Hybridization and Stratification of Nuclear Genetic Variation in Macaca mulatta and M. fascicularis

We used genotypes for 13 short tandem repeats (STRs) to assess the genetic diversity within and differentiation among populations of rhesus macaques (Macaca mulatta) from mainland Asia and long-tailed macaques (M. fascicularis) from mainland and insular Southeast Asia. The subjects were either recently captured in the wild or derived from wild-caught founders maintained in captivity for biomedical research. A large number of alleles are shared between the 2 macaque species but a significant genetic division between them persists. The distinction is more clear-cut among populations that are not, or are unlikely to have recently been, geographically contiguous. Our results suggest there has been significant interspecific nuclear gene flow between rhesus macaques and long-tailed macaques on the mainland. Comparisons of mainland and island populations of long-tailed macaques reflect marked genetic subdivisions due to barriers to migration. Geographic isolation has restricted gene flow, allowing island populations to become subdivided and genetically differentiated. Indonesian long-tailed macaques show evidence of long-term separation and genetic isolation from the mainland populations, whereas long-tailed macaques from the Philippines and Mauritius both display evidence of founder effects and subsequent isolation, with the impact from genetic drift being more profound in the latter.