Time filter

Source Type

Fort Washington, MD, United States

Woodson S.E.,University of Texas Medical Branch | Woodson S.E.,U.S. National Institutes of Health | Freiberg A.N.,University of Texas Medical Branch | Holbrook M.R.,University of Texas Medical Branch | Holbrook M.R.,NIAID Integrated Research Facility
Virus Research | Year: 2013

Yellow fever virus (YFV) infection poses a great risk to un-vaccinated individuals living or traveling in the endemic regions of Africa and South America. It is estimated that approximately 30,000 people die each year of this disease. The liver is the main target of YFV, where as many as 80% of the hepatocytes may become involved in the infection. The overwhelming infection of the liver is associated with the observed hemorrhagic disease manifestations such as petechiae, ecchymoses, and hematemesis which are all thought to be linked with the observed coagulation abnormalities that include prolonged clotting times, reduction in clotting factors, fibrin-split products (D-dimers) and elevated prothrombin times. Many factors involved in the coagulation pathway are produced by hepatocytes, such as fibrinogen (FBG) and plasminogen activator inhibitor-1 (PAI-1). Both of these proteins have been indicated in another flavivirus related disease, dengue, as having roles related to the bleeding abnormalities observed and overall outcome of infection. In this study we wanted to determine if FBG and PAI-1 expression levels by human hepatocytes was disrupted or altered by infection with either wild-type Asibi or vaccine strain17-D YFVs. Our findings indicate that YFV infection does affect the transcriptional and translational expression of FBG and PAI-1 in human hepatocytes and that these results are further affected by IL-6 during early stages of infection. These results may lead to further understanding of the molecular mechanism associated with bleeding abnormalities observed during late stage YFV infection. © 2013 Elsevier B.V.

LaSala P.R.,West Virginia University | Holbrook M.,University of Texas Medical Branch | Holbrook M.,NIAID Integrated Research Facility
Clinics in Laboratory Medicine | Year: 2010

There has been a remarkable increase in tick-borne flaviviral disease incidence throughout the past 2 decades. Transmission of tick-borne viruses, like other vector-borne agents, is impacted by a very broad set of factors, both natural (eg, climate and ecology) and man-made (eg, human mobility and agricultural patterns). As our encroachment into areas of virus endemicity intensifies, and as changes in global economic and environmental conditions continue to promote the expansion of tick populations, we will undoubtedly continue to observe attendant increases in rates of disease attributable to these vector-borne pathogens. This article focuses on a some of the major tick-borne flaviviral diseases, caused in particular by tick-borne encephalitis virus, louping ill virus, Powassan virus, Kyasanur Forest disease virus, and Omsk hemorrhagic fever virus, as well as their subtypes. © 2010 Elsevier Inc.

Yoshii K.,Hokkaido University | Yoshii K.,University of Texas Medical Branch | Igarashi M.,Hokkaido University | Ito K.,Hokkaido University | And 4 more authors.
Virus Research | Year: 2011

Omsk hemorrhagic fever virus (OHFV) is a member of the tick-borne encephalitis serocomplex of flaviviruses, and causes hemorrhagic disease in humans. In this study, an infectious cDNA of OHFV was constructed to investigate the molecular mechanisms involved in OHFV pathogenesis for the first time. Our cDNA clone was capable of producing infectious virus which is genetically identical to the parental Guriev strain, and the recombinant virus showed similar biological properties to the parental virus including growth kinetics and virulence characteristics. While characterizing the cDNAs, fortuitous mutations at NS2A position 46 and NS5 position 836 were found to affect viral production. By using a viral replicon expressing luciferase, it was shown that both of the mutations produced a defect in RNA replication and that the NS5 mutation induced a temperature-sensitive phenotype, indicating the importance of these residues in RNA replication. This infectious cDNA will be a useful tool to study the replication and pathogenesis of OHFV. © 2010 Elsevier B.V.

Andersen K.G.,Harvard University | Andersen K.G.,Cambridge Broad Institute | Andersen K.G.,Scripps Research Institute | Shapiro B.J.,Harvard University | And 84 more authors.
Cell | Year: 2015

Summary The 2013-2015 West African epidemic of Ebola virus disease (EVD) reminds us of how little is known about biosafety level 4 viruses. Like Ebola virus, Lassa virus (LASV) can cause hemorrhagic fever with high case fatality rates. We generated a genomic catalog of almost 200 LASV sequences from clinical and rodent reservoir samples. We show that whereas the 2013-2015 EVD epidemic is fueled by human-to-human transmissions, LASV infections mainly result from reservoir-to-human infections. We elucidated the spread of LASV across West Africa and show that this migration was accompanied by changes in LASV genome abundance, fatality rates, codon adaptation, and translational efficiency. By investigating intrahost evolution, we found that mutations accumulate in epitopes of viral surface proteins, suggesting selection for immune escape. This catalog will serve as a foundation for the development of vaccines and diagnostics. © 2015 Elsevier Inc.

Lok S.-M.,Purdue University | Lok S.-M.,National University of Singapore | Costin J.M.,Florida Gulf Coast University | Hrobowski Y.M.,Florida Gulf Coast University | And 19 more authors.
PLoS ONE | Year: 2012

Dengue virus infects approximately 100 million people annually, but there is no available therapeutic treatment. The mimetic peptide, DN59, consists of residues corresponding to the membrane interacting, amphipathic stem region of the dengue virus envelope (E) glycoprotein. This peptide is inhibitory to all four serotypes of dengue virus, as well as other flaviviruses. Cryo-electron microscopy image reconstruction of dengue virus particles incubated with DN59 showed that the virus particles were largely empty, concurrent with the formation of holes at the five-fold vertices. The release of RNA from the viral particle following incubation with DN59 was confirmed by increased sensitivity of the RNA genome to exogenous RNase and separation of the genome from the E protein in a tartrate density gradient. DN59 interacted strongly with synthetic lipid vesicles and caused membrane disruptions, but was found to be non-toxic to mammalian and insect cells. Thus DN59 inhibits flavivirus infectivity by interacting directly with virus particles resulting in release of the genomic RNA.

Discover hidden collaborations