Phenology, distribution, and host specificity of Solenopsis invicta virus-1

Studies were conducted to examine the phenology, geographic distribution, and host specificity of the Solenopsis invicta virus-1 (SINV-1). Two genotypes examined, SINV-1 and -1A, exhibited similar seasonal prevalence patterns. Infection rates among colonies of S. invicta in Gainesville, Florida, were lowest from early winter (December) to early spring (April) increasing rapidly in late spring (May) and remaining high through August before declining again in the fall (September/October). Correlation analysis revealed a significant relationship between mean monthly temperature and SINV-1 (p<0.0005, r=0.82) and SINV-1A (p<0.0001, r=0.86) infection rates in S. invicta colonies. SINV-1 was widely distributed among S. invicta populations. The virus was detected in S. invicta from Argentina and from all U.S. states examined, with the exception of New Mexico. SINV-1 and -1A were also detected in other Solenopsis species. SINV-1 was detected in Solenopsis richteri and the S. invicta/richteri hybrid collected from northern Alabama and Solenopsis geminata from Florida. SINV-1A was detected in S. geminata and Solenopsis carolinensis in Florida and the S. invicta/richteri hybrid in Alabama. Of the 1989 arthropods collected from 6 pitfall trap experiments from Gainesville and Williston, Florida, none except S. invicta tested positive for SINV-1 or SINV-1A. SINV-1 did not appear to infect or replicate within Sf9 or Dm-2 cells in vitro. The number of SINV-1 genome copies did not significantly increase over the course of the experiment, nor were any cytopathic effects observed. Phylogenetic analyses of SINV-1/-1A nucleotide sequences indicated significant divergence between viruses collected from Argentina and the U.S.     

Genomic variation of the fibropapilloma-associated marine turtle herpesvirus across seven geographic areas and three host species

Fibropapillomatosis (FP) of marine turtles is an emerging neoplastic disease associated with infection by a novel turtle herpesvirus, fibropapilloma-associated turtle herpesvirus (FPTHV). This report presents 23 kb of the genome of an FPTHV infecting a Hawaiian green turtle (Chelonia mydas). By sequence homology, the open reading frames in this contig correspond to herpes simplex virus genes UL23 through UL36. The order, orientation, and homology of these putative genes indicate that FPTHV is a member of the Alphaherpesvirinae. The UL27-, UL30-, and UL34-homologous open reading frames from FPTHVs infecting nine FP-affected marine turtles from seven geographic areas and three turtle species (C. mydas, Caretta caretta, and Lepidochelys olivacea) were compared. A high degree of nucleotide sequence conservation was found among these virus variants. However, geographic variations were also found: the FPTHVs examined here form four groups, corresponding to the Atlantic Ocean, West pacific, mid-Pacific, and east Pacific. Our results indicate that FPTHV was established in marine turtle populations prior to the emergence of FP as it is currently known.     

Detection and differentiation of Xylella fastidiosa strains acquired and retained by glassy-winged sharpshooters (Hemiptera: Cicadellidae) using a mixture of strain-specific primer sets

Xylella fastidiosa Wells is a bacterial pathogen that causes a variety of plant diseases, including Pierce's disease (PD) of grapevine, almond leaf scorch, alfalfa dwarf, citrus variegated chlorosis, and oleander leaf scorch (OLS). Numerous strains of this pathogen have been genetically characterized, and several different strains occur in the United States. The dominant vector in southern California is the glassy-winged sharpshooter, Homalodisca coagulata (Say) (Hemiptera: Cicadellidae). The high mobility of this insect, and its use of large numbers of host plant species, provides this vector with ample exposure to multiple strains of X. fastidiosa during its lifetime. To learn more about the ability of this vector to acquire, retain, and transmit multiple strains of the pathogen, we developed a polymerase chain reaction (PCR)-based method to detect and differentiate strains of X. fastidiosa present in individual glassy-winged sharpshooter adults. Insects were sequentially exposed to plants infected with a PD strain in grapevine and an OLS strain in oleander. After sequential exposure, a few insects tested positive for both strains (7%); however, in most cases individuals tested positive for only one strain (29% PD, 41% OLS). In transmission studies, individual adults transmitted either the PD or OLS strain of the pathogen at a rate (39%) similar to that previously reported after exposure to a single strain, but no single individual transmitted both strains of the pathogen. PD and OLS strains of X. fastidiosa remained detectable in glassy-winged sharpshooter, even when insects were fed on a plant species that was not a host of the strain for 1 wk.     

Comparative genomics of insect juvenile hormone biosynthesis

The biosynthesis of insect juvenile hormone (JH) and its neuroendocrine control are attractive targets for chemical control of insect pests and vectors of disease. To facilitate the molecular study of JH biosynthesis, we analyzed ESTs from the glands producing JH, the corpora allata (CA) in the cockroach Diploptera punctata, an insect long used as a physiological model species and compared them with ESTs from the CA of the mosquitoes Aedes aegypti and Anopheles albimanus. The predicted genes were analyzed according to their probable functions with the Gene Ontology classification, and compared to Drosophila and Anopheles gambiae genes. A large number of reciprocal matches in the cDNA libraries of cockroach and mosquito CA were found. These matches defined known and suspected enzymes of the JH biosynthetic pathway, but also several proteins associated with signal transduction that might play a role in the modulation of JH synthesis by neuropeptides. The identification in both cockroach and mosquito CA of homologs of the small ligand binding proteins from insects, Takeout/JH binding protein and retinol-binding protein highlights a hitherto unsuspected complexity of metabolite trafficking, perhaps JH precursor trafficking, in these endocrine glands. Furthermore, many reciprocal matches for genes of unknown function may provide a fertile ground for an in-depth study of allatal-specific cell physiology. ESTs are deposited in GenBank under the accession numbers DV 017592-DV 018447 (Diploptera punctata); DR 746432-DV 747949 (Aedes aegypti); and DR 747950-DR 748310 (Anopheles albimanus).     

Inhibitory receptor signals suppress ligation-induced recruitment of NKG2D to GM1-rich membrane domains at the human NK cell immune synapse

NKG2D is an activating receptor expressed on all human NK cells and a subset of T cells. In cytolytic conjugates between NK cells and target cells expressing its ligand MHC class I chain-related gene A, NKG2D accumulates at the immunological synapse with GM1-rich microdomains. Furthermore, NKG2D is specifically recruited to detergent-resistant membrane fractions upon ligation. However, in the presence of a strong inhibitory stimulus, NKG2D-mediated cytotoxicity can be intercepted, and recruitment of NKG2D to the immunological synapse and detergent-resistant membrane fractions is blocked. Also, downstream phosphorylation of Vav-1 triggered by NKG2D ligation is circumvented by coengaging inhibitory receptors. Thus, we propose that one way in which inhibitory signaling can control NKG2D-mediated activation is by blocking its recruitment to GM1-rich membrane domains. The accumulation of activating NK cell receptors in GM1-rich microdomains may provide the necessary platform from which stimulatory signals can proceed.     

The role of the prostaglandin D2 receptor, DP, in eosinophil trafficking

Prostaglandin (PG) D2 is a major mast cell product that acts via two receptors, the D-type prostanoid (DP) and the chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) receptors. Whereas CRTH2 mediates the chemotaxis of eosinophils, basophils, and Th2 lymphocytes, the role of DP has remained unclear. We report in this study that, in addition to CRTH2, the DP receptor plays an important role in eosinophil trafficking. First, we investigated the release of eosinophils from bone marrow using the in situ perfused guinea pig hind limb preparation. PGD2 induced the rapid release of eosinophils from bone marrow and this effect was inhibited by either the DP receptor antagonist BWA868c or the CRTH2 receptor antagonist ramatroban. In contrast, BWA868c did not inhibit the release of bone marrow eosinophils when this was induced by the CRTH2-selective agonist 13,14-dihydro-15-keto-PGD2. In additional experiments, we isolated bone marrow eosinophils from the femoral cavity and found that these cells migrated toward PGD2. We also observed that BWA868c inhibited this response to a similar extent as ramatroban. Finally, using immunohistochemistry we could demonstrate that eosinophils in human bone marrow specimens expressed DP and CRTH2 receptors at similar levels. Eosinophils isolated from human peripheral blood likewise expressed DP receptor protein but at lower levels than CRTH2. In agreement with this, the chemotaxis of human peripheral blood eosinophils was inhibited both by BWA868c and ramatroban. These findings suggest that DP receptors comediate with CRTH2 the mobilization of eosinophils from bone marrow and their chemotaxis, which might provide the rationale for DP antagonists in the treatment of allergic disease.     

Characterization of regulatory pathways in Xylella fastidiosa: genes and phenotypes controlled by algU

Many virulence genes in plant bacterial pathogens are coordinately regulated by "global" regulatory genes. Conducting DNA microarray analysis of bacterial mutants of such genes, compared with the wild type, can help to refine the list of genes that may contribute to virulence in bacterial pathogens. The regulatory gene algU, with roles in stress response and regulation of the biosynthesis of the exopolysaccharide alginate in Pseudomonas aeruginosa and many other bacteria, has been extensively studied. The role of algU in Xylella fastidiosa, the cause of Pierce's disease of grapevines, was analyzed by mutation and whole-genome microarray analysis to define its involvement in aggregation, biofilm formation, and virulence. In this study, an algU::nptII mutant had reduced cell-cell aggregation, attachment, and biofilm formation and lower virulence in grapevines. Microarray analysis showed that 42 genes had significantly lower expression in the algU::nptII mutant than in the wild type. Among these are several genes that could contribute to cell aggregation and biofilm formation, as well as other physiological processes such as virulence, competition, and survival.     

Swimbladder Leiomyosarcoma in Atlantic salmon (Salmo salar) in North America

Leiomyosarcoma with associated retrovirus were found in North America for the first time in adult Atlantic salmon (Salmo salar) held in a quarantine facility at the North Attleboro National Fish Hatchery (NANFH), Massachusetts, USA. The fish had been collected as age 1-2 yr animals from the Pleasant River, Maine, and were to be used as brood stock in a population augmentation program for that river. Neoplastic disease was observed at NANFH initially in older (age 4 yr) fish, followed by age 3 yr fish. Disease was not observed in age 2 yr fish. The mortality pattern was chronic.     

Activity of the corpora allata of adult female Aedes aegypti: effects of mating and feeding

The synthesis of juvenile hormone III (JH III) by the isolated corpora allata (CA) of Aedes aegypti adult female was studied using an in vitro radiochemical assay. We dissected the corpora allata-corpora cardiaca (CA-CC) complex attached to a piece of aorta. The complex was left connected to the intact head capsule to facilitate the visualization and transfer of the glands. A linear increase in the cumulative amount of biosynthesized JH III was found for at least the first 6 h of incubation; approximately 45% of the synthesized JH III was present in the medium. There was a dependence of JH III synthesis on exogenous methionine supply. Using reversed phase high performance liquid chromatography two major labeled products biosynthesized by the CA were separated. They co-migrated with JH III and methyl farnesoate (MF). The identity of the biosynthesized JH III was confirmed by gas chromatography-mass spectrometry. JH III synthesis was only 2.0 fmol/pair gland/h immediately after adult emergence, but increased to 32.6 fmol/ pair gland/h 18 h later in sugar-fed females. Two days after emergence, the CA biosynthetic activity slowly started to decrease, and reached values of around 5.3 fmol/pair gland/h by one week after emergence. Synthesis of JH was similar from either sugar-fed females mated or unmated. A blood meal resulted in a decrease of JH III synthesis in CA from mated females by 12 h after feeding and from virgin females by 24 h after feeding. JH III biosynthesis remained low for at least 96 h in mated females, but was back to higher levels 72 h after feeding in virgin females. Rates of JH III biosynthesis closely reflected the hemolymph levels of JH III both after emergence and after a blood meal described by Shapiro et al. (1986). The activity of the CA in Aedes aegypti females seems to be regulated by developmental changes and nutritional signals, and to be independent of mating stimulus.