Superior infectivity for mosquito vectors contributes to competitive displacement among strains of dengue virus

<p>Abstract</p> <p>Background</p> <p>Competitive displacement of a weakly virulent pathogen strain by a more virulent strain is one route to disease emergence. However the mechanisms by which pathogens compete for access to hosts are poorly understood. Among vector-borne pathogens, variation in the ability to infect vectors may effect displacement. The current study focused on competitive displacement in dengue virus serotype 3 (DENV3), a mosquito-borne pathogen of humans. In Sri Lanka in the 1980's, a native DENV3 strain associated with relatively mild dengue disease was displaced by an invasive DENV3 strain associated with the most severe disease manifestations, dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS), resulting in an outbreak of DHF/DSS. Here we tested the hypothesis that differences between the invasive and native strain in their infectivity for <it>Aedes aegypti </it>mosquitoes, the primary vector of DENV, contributed to the competitive success of the invasive strain</p> <p>Results</p> <p>To be transmitted by a mosquito, DENV must infect and replicate in the midgut, disseminate into the hemocoel, infect the salivary glands, and be released into the saliva. The ability of the native and invasive DENV3 strains to complete the first three steps of this process in <it>Aedes aegypti </it>mosquitoes was measured <it>in vivo</it>. The invasive strain infected a similar proportion of mosquitoes as the native strain but replicated to significantly higher titers in the midgut and disseminated with significantly greater efficiency than the native strain. In contrast, the native and invasive strain showed no significant difference in replication in cultured mosquito, monkey or human cells.</p> <p>Conclusion</p> <p>The invasive DENV3 strain infects and disseminates in <it>Ae. aegypti </it>more efficiently than the displaced native DENV3 strain, suggesting that the invasive strain is transmitted more efficiently. Replication in cultured cells did not adequately characterize the known phenotypic differences between native and invasive DENV3 strains. Infection dynamics within the vector may have a significant impact on the spread and replacement of dengue virus lineages.</p

Repertoire of virus-derived small RNAs produced by mosquito and mammalian cells in response to dengue virus infection

AbstractRNA interference (RNAi) is the major defense of many arthropods against arthropod-borne RNA viruses (arboviruses), but the role of RNAi in vertebrate immunity to arboviruses is not clear. RNA viruses can trigger RNAi in vertebrate cells, but the vertebrate interferon response may obscure this interaction. We quantified virus-derived small RNAs (vRNAs) generated by mosquito (U4.4) cells and interferon-deficient (Vero) and interferon-competent (HuH-7) mammalian cells infected with a single isolate of mosquito-borne dengue virus. Mosquito cells produced significantly more vRNAs than mammalian cells, and mosquito cell vRNAs were derived from both the positive- and negative-sense dengue genomes whereas mammalian cell vRNAs were derived primarily from positive-sense genome. Mosquito cell vRNAs were predominantly 21 nucleotides in length whereas mammalian cell vRNAs were between 12 and 36 nucleotides with a modest peak at 24 nucleotides. Hot-spots, regions of the virus genome that generated a disproportionate number of vRNAs, overlapped among the cell lines

Molecular systematics of two enigmatic genera Psittacella and Pezoporus illuminate the ecological radiation of Australo-Papuan parrots (Aves: Psittaciformes)

The platycercine parrots of Australia, usually recognized as the Platycercinae or Platycercini, are the broad-tailed parrots and their allies typified by the rosellas Platycercus spp. Debate concerning their circumscription has most recently centerd on the position of four genera, Neophema, Neopsephotus, Pezoporus and Psittacella, the last two having never been adequately included in sequence-based analyses. We use broad taxon sampling, mitochondrial and nuclear DNA sequence data from seven independent loci (two linked mitochondrial loci and six nuclear loci), and both gene tree and species tree approaches to reconstruct phylogenies and so determine the systematic placement all four genera. Analyses of two data sets, one of 48 taxa and five loci and one of 27 taxa and the same five plus three additional loci produced broadly congruent and consistently well-resolved phylogenies. We reject placement of any of these four genera within core platycercines. Pezoporus is closely allied to Neophema and Neopsephotus. These three genera are the likely sister group to core platycercines and we advocate their recognition as a subfamily. Psittacella is the sole extant representative of a lineage that branched very early in the history of Australo-Papuan parrot fauna and is not closely related to any of the mostly south-east Asian and Indonesian psittaculine taxa with which it is more often linked. We present a revised view of the extraordinary phylogenetic, phenotypic and ecological diversity that is the adaptive radiation of Australo-Papuan parrots. Finally, our analyses highlight the likely paraphyly of Mayr's (2008) Loricoloriinae

Higher classification of New World parrots (Psittaciformes; Arinae), with diagnoses of tribes

Schodde, Richard, Remsen, J. V., Schirtzinger, Erin E., Joseph, Leo, Wright, Timothy F. (2013): Higher classification of New World parrots (Psittaciformes; Arinae), with diagnoses of tribes. Zootaxa 3691 (5): 591-596, DOI: 10.11646/zootaxa.3691.5.

DNA-sequence data require revision of the parrot genus Aratinga (Aves: Psittacidae)

Remsen, J. V., Schirtzinger, Erin E., Ferraroni, Anna, Silveira, Luís Fábio, Wright, Timothy F. (2013): DNA-sequence data require revision of the parrot genus Aratinga (Aves: Psittacidae). Zootaxa 3641 (3): 296-300, DOI: http://dx.doi.org/10.11646/zootaxa.3641.3.

Old Drugs with New Tricks: Efficacy of Fluoroquinolones to Suppress Replication of Flaviviruses

Repurposing FDA-approved compounds could provide the fastest route to alleviate the burden of disease caused by flaviviruses. In this study, three fluoroquinolones, enoxacin, difloxacin and ciprofloxacin, curtailed replication of flaviviruses Zika (ZIKV), dengue (DENV), Langat (LGTV) and Modoc (MODV) in HEK-293 cells at low micromolar concentrations. Time-of-addition assays suggested that enoxacin suppressed ZIKV replication at an intermediate step in the virus life cycle, whereas ciprofloxacin and difloxacin had a wider window of efficacy. A129 mice infected with 1 &times; 105 plaque-forming units (pfu) ZIKV FSS13025 (n = 20) or phosphate buffered saline (PBS) (n = 11) on day 0 and treated with enoxacin at 10 mg/kg or 15 mg/kg or diluent orally twice daily on days 1&ndash;5 did not differ in weight change or virus titer in serum or brain. However, mice treated with enoxacin showed a significant, five-fold decrease in ZIKV titer in testes relative to controls. Mice infected with 1 &times; 102 pfu ZIKV (n = 13) or PBS (n = 13) on day 0 and treated with 15 mg/kg oral enoxacin or diluent twice daily pre-treatment and days 1&ndash;5 post-treatment also did not differ in weight and viral load in the serum, brain, and liver, but mice treated with enoxacin showed a significant, 2.5-fold decrease in ZIKV titer in testes relative to controls. ZIKV can be sexually transmitted, so reduction of titer in the testes by enoxacin should be further investigated

Evaluation of A Baculovirus-Expressed VP2 Subunit Vaccine for the Protection of White-Tailed Deer (Odocoileus virginianus) from Epizootic Hemorrhagic Disease

Epizootic hemorrhagic disease virus (EHDV) is an arthropod-transmitted RNA virus and the causative agent of epizootic hemorrhagic disease (EHD) in wild and domestic ruminants. In North America, white-tailed deer (WTD) experience the highest EHD-related morbidity and mortality, although clinical disease is reported in cattle during severe epizootics. No commercially licensed EHDV vaccine is available in North America. The objective of this study was to develop and evaluate a subunit vaccine candidate to control EHD in WTD. Recombinant VP2 (rVP2) outer capsid proteins of EHDV serotypes 2 (EHDV-2) and 6 (EHDV-6) were produced in a baculovirus-expression system. Mice and cattle vaccinated with EHDV-2 or EHDV-6 rVP2 produced homologous virus-neutralizing antibodies. In an immunogenicity/efficacy study, captive-bred WTD received 2 doses of EHDV-2 rVP2 or sham vaccine, then were challenged with wild-type EHDV-2 at 30 d post vaccination. None of the rVP2-vaccinated deer developed clinical disease, no viral RNA was detected in their blood or tissues (liver, lung, spleen, kidney), and no EHDV-induced lesions were observed. Sham-vaccinated deer developed clinical disease with viremia and typical EHD vascular lesions. Here, we demonstrate a rVP2 subunit vaccine that can provide protective immunity from EHDV infection and which may serve as an effective tool in preventing clinical EHD and reducing virus transmission

Multiple independent origins of mitochondrial control region duplications in the order Psittaciformes

mitochondrial genomes are generally thought to be under selection for compactness, due to their small size, consistent gene content, and a lack of introns or intergenic spacers. As more animal mitochondrial genomes are fully sequenced, rearrangements and partial duplications are being identified with increasing frequency, particularly in birds (Class Ayes). In this study, we investigate the evolutionary history of mitochondrial control region states within the avian order Psittaciformes (parrots and cockatoos). To this aim, we reconstructed a comprehensive multi-locus phylogeny of parrots, used PCR of three diagnostic fragments to classify the mitochondrial control region state as single or duplicated, and mapped these states onto the phylogeny. We further sequenced 44 selected species to validate these inferences of control region state. Ancestral state reconstruction using a range of weighting schemes identified six independent origins of mitochondrial control region duplications within Psittaciformes. Analysis of sequence data showed that varying levels of mitochondrial gene and tRNA homology and degradation were present within a given clade exhibiting duplications. Levels of divergence between control regions within an individual varied from 0-10.9% with the differences occurring mainly between 51 and 225 nucleotides 3' of the goose hairpin in domain I. Further investigations into the fates of duplicated mitochondrial genes, the potential costs and benefits of having a second control region, and the complex relationship between evolutionary rates, selection, and time since duplication are needed to fully explain these patterns in the mitochondrial genome. (C) 2012 Elsevier Inc. All rights reserved.NIHNIH [S06 GM008136]Sigma XiSigma XiFundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq