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Rift Valley fever: development of diagnostics and vaccines
Umeå University, Faculty of Medicine, Clinical Microbiology. Umeå University, Faculty of Medicine, Clinical Microbiology, Infectious Diseases. Umeå University, Faculty of Medicine, Clinical Microbiology, Virology. (Clas Ahlm)
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Rift Valley Fever virus (RVFV) causes an infection with severe impact on animal and human health. The disease is endemic throughout almost the entire African continent and large regions of the Arabian Peninsula. During epidemics, high mortality is observed in animals, especially among cattle, goats, and sheep. In humans, the symptoms vary from a benign influenza-like disease to a life-threatening hemorrhagic fever. Due to the devastating effect on communities in endemic regions and the possibility of further spread of this virus, there is an imperative need to improve and develop control measurements against this emerging disease. Therefore, this thesis focuses on diagnostics and vaccines against RVFV.

RVFV infection kinetics was studied in a mouse model system by detection and quantification of viral genomes, using a developed quantitative real-time PCR (QRT-PCR) method. This novel QRT-PCR method proved to be reliable and serves as a supplement to standard diagnostics, direct virus isolation and serological methods. High levels of viral RNA were found in blood and liver samples from experimentally infected mice during the first days post infection. Thereafter the levels declined rapidly and dropped below detection limit approximately seven days post infection. The QRT-PCR technique was also used in a study aimed to improve diagnosis of RVFV from field samples collected on filter strips.

Today, the available RVFV vaccines are only approved for animal use and these vaccines have several shortcomings. Since RVFV is a highly pathogenic organism requiring bio-safety level 3 laboratories, two different none-replicating vaccine approaches have been applied and evaluated using a mouse model. A DNA based vaccine, administered via gene-gun, and the use of virus-like particles (VLP), by the intra-peritoneal route. RVFV specific and neutralising antibodies were raised with both vaccine approaches. However, VLP vaccination against Rift valley Fever proved to be more promising as a future vaccine, since higher titres of neutralising antibodies and improved survival rate were found upon a lethal RVFV challenge in mice.

In conclusion, a sensitive and specific method for quantifying RVFV infection and a promising vaccine candidate against RVFV were developed.

Place, publisher, year, edition, pages
Umeå: Umeå university , 2010. , 64 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1323
Keyword [en]
Rift Valley Fever, vaccines, diagnostics
National Category
Medical and Health Sciences Microbiology in the medical area
Research subject
Medical Virology; Infectious Diseases
Identifiers
URN: urn:nbn:se:umu:diva-30676ISBN: 978-91-7264-883-8 (print)OAI: oai:DiVA.org:umu-30676DiVA: diva2:285540
Public defence
2010-02-05, Betula, byggnad 6M, 901 85 umeå universitet, NUS, 09:00 (English)
Opponent
Supervisors
Available from: 2010-01-18 Created: 2010-01-12 Last updated: 2010-01-18Bibliographically approved
List of papers
1. Kinetics of Rift Valley fever virus in experimentally infected mice using quantitative real-time RT-PCR
Open this publication in new window or tab >>Kinetics of Rift Valley fever virus in experimentally infected mice using quantitative real-time RT-PCR
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2008 (English)In: Journal of Virological Methods, ISSN 0166-0934, E-ISSN 1879-0984, Vol. 151, no 2, 277-282 p.Article in journal (Refereed) Published
Abstract [en]

Rift Valley Fever (RVF) is an important viral zoonosis in Africa affecting animals and humans. Since no protective vaccines or effective treatments are available for human use, accurate and reliable diagnostic methods are essential for surveillance of the disease in order to implement adequate public health actions. To study the kinetics of the RVF Virus (RVFV) infection, a SYBR Green-based quantitative real-time RT-PCR assay was developed. By using primers targeting the S-segment of RVFV, the detection limit of this assay was estimated to 30 RNA templates. Blood and organs of experimentally infected mice were sampled at different time points and RVFV RNA was quantified. High amounts of RVFV RNA were found in blood, brain, and liver samples shortly after infection with a 1-4 days post infection window for viral RNA detection. Mice developed symptoms after the appearance of serum antibodies, indicating that the host response plays an important role in the outcome of the disease. The RVFV quantitative RT-PCR proved to be a valuable diagnostic tool during the first days of infection, before detectable antibody levels and visual symptoms of RVF were observed.

Identifiers
urn:nbn:se:umu:diva-21109 (URN)10.1016/j.jviromet.2008.04.007 (DOI)18514921 (PubMedID)
Available from: 2009-04-02 Created: 2009-04-02 Last updated: 2017-12-13Bibliographically approved
2. PCR detection of a hantavirus and Rift Valley fever virus using dried whole blood spotted on filter strips
Open this publication in new window or tab >>PCR detection of a hantavirus and Rift Valley fever virus using dried whole blood spotted on filter strips
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Viral hemorrhagic fevers are serious and emerging infections among humans and animals worldwide. Presently, blood or serum samples are the main source for diagnostics. However, transportation of such samples from remote areas may be complicated and expensive. Previously, filter strips soaked with blood have been used for detection of antibodies for diagnostics and epidemiological studies of several infectious diseases.

In this study we evaluate if a similar approach could be applied for detection of viral RNA of Rift Valley Fever virus or Hantavirus (Puumala).

We have used whole blood spiked with known amounts of viruses. In addition, clinical samples from patients with acute hemorrhagic fever with renal syndrome have been analysed. The samples were collected on filter strips and dried before RNA was extracted at different time-points. For Puumala, the sensitivity was acceptable, although the absolute levels of viral RNA were found to be considerable lower when using filter strips. The viral RNA could be detected and analysed after 2-3 weeks storage of the dried filter strips. In contrast, for RVFV, no or very low copy numbers of viral RNA were detected. Still, RVFV filter strips contained viable virus particles up to 48 h of storage.

In conclusion, the use of dried whole blood samples spotted on filter strips for the detection of viral RNA seems to be a reliable and simple procedure for Hantaviruses. This procedure could be useful in field studies, especially in remote areas or low-income countries where transportation and storage of biological samples might be complicated. However, the result for RVFV was unexpected and further studies are needed to improve this technique.

Keyword
Rift Valley fever, hantavirus, filter strips
Research subject
Medical Virology
Identifiers
urn:nbn:se:umu:diva-30673 (URN)
Note
Ej publicerat. Not submitted.Available from: 2010-01-12 Created: 2010-01-12 Last updated: 2011-10-14Bibliographically approved
3. Characterisation of immune responses and protective efficacy in mice after immunisation with Rift Valley Fever virus cDNA constructs
Open this publication in new window or tab >>Characterisation of immune responses and protective efficacy in mice after immunisation with Rift Valley Fever virus cDNA constructs
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2009 (English)In: Virology journal, ISSN 1743-422X, Vol. 6, 6- p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Affecting both livestock and humans, Rift Valley Fever is considered as one of the most important viral zoonoses in Africa. However, no licensed vaccines or effective treatments are yet available for human use. Naked DNA vaccines are an interesting approach since the virus is highly infectious and existing attenuated Rift Valley Fever virus vaccine strains display adverse effects in animal trials. In this study, gene-gun immunisations with cDNA encoding structural proteins of the Rift Valley Fever virus were evaluated in mice. The induced immune responses were analysed for the ability to protect mice against virus challenge. RESULTS: Immunisation with cDNA encoding the nucleocapsid protein induced strong humoral and lymphocyte proliferative immune responses, and virus neutralising antibodies were acquired after vaccination with cDNA encoding the glycoproteins. Even though complete protection was not achieved by genetic immunisation, four out of eight, and five out of eight mice vaccinated with cDNA encoding the nucleocapsid protein or the glycoproteins, respectively, displayed no clinical signs of infection after challenge. In contrast, all fourteen control animals displayed clinical manifestations of Rift Valley Fever after challenge. CONCLUSION: The appearance of Rift Valley Fever associated clinical signs were significantly decreased among the DNA vaccinated mice and further adjustment of this strategy may result in full protection against Rift Valley Fever.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:umu:diva-30671 (URN)10.1186/1743-422X-6-6 (DOI)19149901 (PubMedID)
Available from: 2010-01-12 Created: 2010-01-12 Last updated: 2012-06-05Bibliographically approved
4. Vaccination with virus-like particles protects mice from lethal infection of Rift Valley fever virus
Open this publication in new window or tab >>Vaccination with virus-like particles protects mice from lethal infection of Rift Valley fever virus
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2009 (English)In: Virology, ISSN 0042-6822, E-ISSN 1096-0341, Vol. 385, no 2, 409-415 p.Article in journal (Refereed) Published
Abstract [en]

Rift Valley Fever virus (RVFV) regularly accounts for severe and often lethal outbreaks among livestock and humans in Africa. Safe and effective veterinarian and human vaccines are highly needed. We present evidence that administration of RVF virus-like particles (VLPs) induces protective immunity in mice. In an accompanying paper, (Habjan, M., Penski, N., Wagner, V., Spiegel, M., Overby, A.K., Kochs, G., Huiskonen, J., Weber, F., 2009. Efficient production of Rift Valley fever virus-like particles: the antiviral protein MxA can inhibit primary transcription of Bunyaviruses. Virology 385, 400-408) we report the production of these VLPs in mammalian cells. After three subsequent immunizations with 1x10(6) VLPs/dose, high titers of virus-neutralizing antibodies were detected; 11 out of 12 mice were protected from challenge and only 1 out of 12 mice survived infection in the control groups. VLP vaccination efficiently suppressed replication of the challenge virus, whereas in the control animals high RNA levels and increasing antibody titers against the nucleocapsid protein indicated extensive viral replication. Our study demonstrates that the RVF VLPs are highly immunogenic and confer protection against RVFV infection in mice. In the test groups, the vaccinated mice did not exhibit any side effects, and the lack of anti-nucleocapsid protein antibodies serologically distinguished vaccinated animals from experimentally infected animals.

Keyword
Rift Valley Fever virus
National Category
Infectious Medicine
Identifiers
urn:nbn:se:umu:diva-21105 (URN)10.1016/j.virol.2008.12.012 (DOI)19157482 (PubMedID)
Available from: 2009-04-02 Created: 2009-04-02 Last updated: 2017-12-13Bibliographically approved

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