102,224 research outputs found
Comparative studies on Mopeia viruses and other Arenaviridae, particularly Lassa virus
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Serologically related arenaviruses have been isolated from West Africa, Mozambique, Zimbabwe and the Central African Republic. Human disease is only associated with the West African isolates. The virulence of Mozambique, Zimbabwe and Central African Republic isolates in humans is not known.
This Thesis is an account of work carried out by the author to compare the biological characteristics of isolates from West Africa, Mozambique and Zimbabwe. It describes the successful isolation and identification of the aetiological agents, their physicochemical and antigenic characteristics and describes in vivo studies using mice, guinea pigs and Rhesus monkeys.
A direct comparison was made with a patient diagnosed as having Lassa fever. The disease in man and monkeys following infection with Lassa virus was similar. The Rhesus monkey and guinea pig proved suitable experimental models in which to study and compare the pathogenic responses and also to evaluate various aspects of protection. These animal models when immunised with the viruses from Mozambique and Zimbabwe were protected when subsequently challenged with Lassa virus.
The Mozambique and Zimbabwe isolates proved to have morphological and physicochemical characteristics not dissimilar from West African Lassa viruses and those members of the arenavirus family from South America. Serological and immunochemical investigations suggest the existence of both common and unique antigenic determinants on the viruses from Mozambique, -Zimbabwe and West Africa. This grouping also coincides with the geographic separation of the viruses, i.e. Lassa - West Africa and Mopeia -southeast Africa. Similar differences in host susceptibility have also been demonstrated. Lassa virus produces a fatal haemorrhagic disease while Mopeia isolates produce only an asymptomatic infection. The combined data suggests the possibility of two virus groups within the 'Old World' arenavirus classification. The proposed name, 'Mopeia', forms one group and includes the viruses from Mozambique and Zimbabwe. The Lassa strains from West Africa form the second group.
It is suggested that the Mopeia viruses are minor antigenic variants of Lassa and should be included within the arenavirus family
Structural and functional studies of novel mechanisms of Lassa fever virus nucleoprotein in immune suppression, viral RNA transcription and replication
No full textLassa fever virus is one of the most dangerous viruses of arenaviridae family,
causing more than 500,000 infections per year in Africa. The fatality rate for
hospitalized patients is as high as 20%. Due to the high fatality and lack of efficient licensed drugs and vaccines to treat and prevent, Lassa fever virus is classified as a Category A priority pathogen and biosafety level-4 agent by the Centers for Disease Control and Prevention of the USA. Cases were also found in the Americas and European countries, highlighting its potency to be a
bioterrorism weapon.
Like other areanaviruses, Lassa virus has developed a unique interferon suppression mechanism to evade from the host immune system, in which Lassa
nucleoprotein plays the key role. To understand the LASV nucleoprotein functions, we tried to determine the first arenaviral nucleoprotein structure, LASV nucleoprotein. The LASV nucleoprotein (NP) was overexpressed and purified. The NP protein was crystallized and the structure was determined to 1.80 Å resolution. The crystals belong to space group P3, with the unit cell parameters a = b = 177.16 Å, c = 56.49 Å, α= β= 90° and γ= 120°. The LASV NP
structure contains two domains, which are not similar to any reported viral nucleoprotein structures. The N-terminal domain has a novel structure with a
cavity, which we proposed for cap binding, and the C-terminus is a 3’-5' ribonuclease, which is responsible for suppressing interferon production. To characterize the possible interaction between NP and other arenaviral protein, we also overexpressed and purified LASV Z. Interestingly, both NP and Z proteins have two forms and the purified NP protein and monomeric Z protein bind RNA.
It is surprising that only the oligomeric Z protein interacts with NP protein but
the monomeric Z protein does not as determined by Isothermal Titration
Calorimetry (ITC). Our studies have reported the first arenaviral nucleoprotein
structure, revealed the novel mechanism for the cap binding and immune
suppression, which set up a platform for the development of novel drugs and vaccines
to treat deadly arenaviral infections
J Infect Dis
No full textLassa fever is a viral zoonosis that can be transmitted from person to person, especially in the hospital setting. The disease is endemic to several countries in West Africa and can be a major contributor to morbidity and mortality in affected areas. There are no approved vaccines to prevent Lassa virus infection. In this work, we present a vaccine candidate that combines the scalability and efficacy benefits of a live vaccine with the safety benefits of single-cycle replication. The system consists of Lassa virus replicon particles devoid of the virus essential glycoprotein gene, and a cell line that expresses the glycoprotein products, enabling efficient vaccine propagation. Guinea pigs vaccinated with these particles showed no clinical reaction to the inoculum and were protected against fever, weight loss, and lethality after infection with Lassa virus.CC999999/Intramural CDC HHSUnited States
Lassa Virus Vaccine Design and Vaccination Regimen
No full text<div><p>(A) Left, schematic diagram of the recombinant VSV expressing the glycoprotein of Lassa virus. The VSV glycoprotein (G) was replaced with the Lassa virus glycoprotein (LV GPC). Shown are the nucleocapsid (N), phosphoprotein (P), matrix (M), and RNA-dependent RNA polymerase (L). Right, gold sphere labeling (10-nm spheres) of VSVΔG/LVGPC particles by immunoelectron microscopy using a pool of two murine monoclonal antibodies directed against Lassa virus GP1 and GP2; particles were negatively contrasted with 1% uranyl acetate.</p>
<p>(B) Time line for vaccination and Lassa viral challenge study. Vaccination of cynomolgus monkeys was done with a single intramuscular dose of 10<sup> 7</sup> PFU of either VSVΔG/LVGPC (four animals) or VSVΔG/ZEBOVGP (two animals). Challenge was performed with a single intramuscular dose of 10<sup>4</sup> PFU of Lassa virus, strain Josiah. Arrows indicate day of sampling (blood and swabs).</p></div
Detection of Lassa Virus, Mali
No full textTo determine whether Lassa virus was circulating in southern Mali, we tested samples from small mammals from 3 villages, including Soromba, where in 2009 a British citizen probably contracted a lethal Lassa virus infection. We report the isolation and genetic characterization of Lassa virus from an area previously unknown for Lassa fever
Lassa Fever: From a Nigerian Town to a Global Threat
No full textLassa fever is associated with high morbidity and mortality rate. This is due to the primary host of Lassa virus being a rodent of the genus Mastomy’s, also referred to as ‘multimammate rat’. Once infected, Mastomy’s rats do not become ill but can shed the virus in their urine and feces. Thus, there has been a call for educational interventions to improve the knowledge of Lassa fever among community members. It is important to point out that health workers have a prominent role to play in realizing this. In conclusion, Lassa Fever hasn\u27t been a main global threat in the past 10 years. (edited) 1:08 Lassa fever is an acute viral disease that is transmitted by the common African rat and is animal-borne, or zoonotic. It is indigenous to West Africa and is transmitted by consuming or coming into contact with food or objects that have been exposed to urine or rodent droppings. Ribavirin is the preferred treatment for Lassa Fever, but wearing protective gear and sterilizing all equipment is also advised. Third-trimester pregnant women have a 95% probability of dying from immunosuppression. There have only been seven instances of Lassa Fever reported in the United States.There is a need for educational interventions to increase community members\u27 understanding of Lassa fever, and health professionals may play a significant part in making this a reality. In summary, Lassa Fever hasn\u27t posed a significant threat to the world in the last ten years
Lassa virus circulating in Liberia: a retrospective genomic characterisation
No full textBackground An alarming rise in reported Lassa fever cases continues in west Africa. Liberia has the largest reported per capita incidence of Lassa fever cases in the region, but genomic information on the circulating strains is scarce. The aim of this study was to substantially increase the available pool of data to help foster the generation of targeted diagnostics and therapeutics.
Methods Clinical serum samples collected from 17 positive Lassa fever cases originating from Liberia (16 cases) and Guinea (one case) within the past decade were processed at the Liberian Institute for Biomedical Research using a targeted-enrichment sequencing approach, producing 17 near-complete genomes. An additional 17 Lassa virus sequences (two from Guinea, seven from Liberia, four from Nigeria, and four from Sierra Leone) were generated from viral stocks at the US Centers for Disease Control and Prevention (Atlanta, GA) from samples originating from the Mano River Union (Guinea, Liberia, and Sierra Leone) region and Nigeria. Sequences were compared with existing Lassa virus genomes and published Lassa virus assays.
Findings The 23 new Liberian Lassa virus genomes grouped within two clades (IV.A and IV.B) and were genetically divergent from those circulating elsewhere in west Africa. A time-calibrated phylogeographic analysis incorporating the new genomes suggests Liberia was the entry point of Lassa virus into the Mano River Union region and estimates the introduction to have occurred between 300–350 years ago. A high level of diversity exists between the Liberian Lassa virus genomes. Nucleotide percent difference between Liberian Lassa virus genomes ranged up to 27% in the L segment and 18% in the S segment. The commonly used Lassa Josiah-MGB assay was up to 25% divergent across the target sites when aligned to the Liberian Lassa virus genomes.
Interpretation The large amount of novel genomic diversity of Lassa virus observed in the Liberian cases emphasises the need to match deployed diagnostic capabilities with locally circulating strains and underscores the importance of evaluating cross-lineage protection in the development of vaccines and therapeutics
New Lineage of Lassa Virus, Togo, 2016
No full textWe describe a strain of Lassa virus representing a putative new lineage that was isolated from a cluster of human infections with an epidemiologic link to Togo. This finding extends the known range of Lassa virus to Togo
Evaluation of the diagnostic accuracy of the ReLASV Pan-Lassa Antigen Rapid Test for Lassa Fever in Nigeria.
No full textLassa fever is a zoonotic disease found in several countries across West Africa, with estimates of up to 300,000 infections and 10,000 deaths yearly. The highest incidence is in Nigeria. Suspected cases are often seen in areas with limited infrastructure and diagnostics capacity, hence the availability of an accurate rapid diagnostic test (RDT) that could be used in the community would be an important public health tool. Unfortunately, few RDTs for Lassa fever exist and have not been thoroughly validated. Toward that end, we conducted a Phase 2 performance evaluation to assess the diagnostic accuracy of the ReLASV Pan-Lassa Antigen Rapid Test (Zalgen Labs, Frederick, MD, USA) using archived, frozen whole blood, plasma, and serum samples collected from individuals in Nigeria to determine its suitability for widespread use as a screening tool for Lassa fever. The overall performance of this RDT was measured against the reference test, the Altona RealStar LASV real-time reverse transcription polymerase chain reaction 2.0 (Altona Diagnostics, Hamburg, Germany). The sensitivity and specificity of the ReLASV Pan-Lassa Antigen Test were 65% and 50.7%, respectively. The low diagnostic accuracy indicated in our and other independent evaluations of the ReLASV Pan-Lassa Antigen Rapid Test suggests that this test, at least until further developed, refined, and validated, is not suitable for making critical diagnostic or treatment decisions for Lassa fever, at least for lineages that commonly circulate in Nigeria. These findings underscore the importance of thoroughly assessing the performance characteristics of tests to ensure their reliability and accuracy
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