By: Varun Natraj, Kenneth
Forward, and Connor Pennington
Semliki Forest Virus
Definitions
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Genome: Set of chromosomes
Trimer: A trimer is a polymer with 3 molecules
Alphavirus: A mosquito borne virus
Icosahedral: Twenty-sided figure
Bilayer: Two molecule layer
Glycoprotein: Protein with carbohydrate component
Capsid: Virus shell
Lipid: Constituent of fat
Arthropod: Invertebrate animal
Interconnective: Mutually connecting
Neuropathy: Disease of nervous system
Biological Vector: A vector that is vital to the life cycle of a
pathogenic cell
History/Background
• The Semliki Forest Virus was first isolated from mosquitoes in the
Semliki Forest in Uganda in 1942.
• The Semliki Forest Virus is an Alphavirus; There are a total of 27
alphaviruses able to infect mammals as well as humans. The
Semliki Forest Virus is an alphavirus because transmission of the
virus occurs via mosquitoes which is a major characteristic of
alphaviruses. This makes the alphavirus a contributor to Arthopod
borne viruses or Arboviruses.
What is the Semliki Forest Virus?
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The Semliki Forest Virus is a positive-stranded RNA based virus with an
icosahedral capsid. This is enveloped by a lipid bilayer, constructed from
the host cell.
The outermost surface of the virus is covered by different monomers of
various glycoproteins , which are arranged in interconnective trimers which
form the outer shell.
The Semliki Forest Virus is spread mainly through mosquito bites. The virus
is able to cause massive brain swelling, or encephalitis, in rodents, birds
and other small animals, but only one human death has ever been
attributed to the virus. However even in this case, the fatality of the victim
was caused more so by a faulty immune system and extreme amounts of
exposure to the virus rather than the viruses potency.
The Virus has been used extensively in biological research as a model of
the viral life cycle.
Also, due to its broad host range and efficient replication, it has been
developed as a vector for genes, encoding vaccines and anti-cancer
agents, and as a tool in gene therapy.
The Semliki Forest Genome
• The size of the Semliki Forest Virus genome is around
13,000 base pairs.
• Two-thirds of the genome encode non-structural
proteins, while the other third encodes structural
proteins.
• The expression of these proteins and the replication of
the viral chromosomes takes place in the cytoplasm of
the host cells.
• The composition and transportation of its three
glycoproteins through the endoplasmic reticulum and
golgi bodies has been used as a model for the synthesis
and export of the proteins in the plasma membrane
The Semliki Forest Virus,
Cancer, and other Diseases
• RNA interference is a system within living cells that helps
determine what genes are active and how active they
are.
• RNA interference has recently been discovered as a
mode of inhibition for slowly replicating viruses that can
cause diseases such as Hepatitis C.
• RNA interference has also been tested on SFV to figure
out whether RNA interference is a viable option to inhibit
rapidly replicating RNA viruses.
• Through research scientists have discovered that RNA
interference might improve the response to quickly
spreading virus based infections.
The Semliki Forest Virus, Cancer,
and other Diseases cont.
• The use of RNA interference has helped prove that faulty
genes can lead to cancer.
• The knowledge of the structure of the SFV suggests
alphaviruses use a common means for infection. This may
help in finding possible strategies to help prevent other
alphaviruses such as Yellow Fever, and the Dengue Virus.
• SFV has been widely used in biological research as a model
to illustrate the viral life cycle and to show the effects of the
neurological diseases caused by viruses.
• SFV has a wide host range and can replicate efficiently; with
these characteristics it has been used as a biological vector
for genes, encoding vaccines, and cancer agents.
The Semliki Forest Virus, Cancer,
and other Diseases
• Semliki Forest Virus based systems are becoming more
prevalent as the virus vector system used for research
therapy and diagnosis. They have also been used to
formulate vaccines for various pathogens.
• For all of these applications of SFV the virus is modified
through engineering the viral replicase gene and then
targeting specific cell types.
• Much of the research done on SFV has been conducted
in Europe, through European Union laboratories.
Reference
• en.wikipedia.org/wiki/Semliki_Forest_Virus
• www.liebertonline.com/doi/abs/10.1089/oli.2007.0079
• www.esrf.eu/UsersAndScience/Publications/Highlights/2001/li
fe-sciences/LS3 .htm
• www.sfvectors.ed.ac.uk/
• medicaldictionary.thefreedictionary.com/Semliki+Forest+Virus
• cancerweb.ncl.ac.uk/cgi-bin/omd?Semliki+forest+virus