1. SV 40
SIMIAN VIRUS 40
PRESENTED BY
KAVYA.H.DAS
2ND YEAR
M.SC.ZOOLOGY
PSG COLLEGE OF ARTS AND SCIENCE
2. VECTORS
• Vectors are autonomously replicating DNA molecules that can
be used to carry foreign DNA fragments.
• It is a vehicle used in gene cloning.
• DNA of interest is first cloned into an appropriate vector and
then by transfection, the gene can be inserted into the host for
its expression.
• For expressing heterologous genes in mammalian cells, usually
vectors derived from mammalian viruses are used.
• Retroviruses are the most common vectors at present.
3. SV40
• SV40 is a macaque polyomavirus consisting of
icosahedral particles of 45 nm in diameter.
• Each particle contains a single copy of the viral genome, a
circular 5.2 kilobase pairs long double-stranded DNA molecule
packaged with histones to form a mini-chromosome.
• The SV40 genomic DNA has two genes. The early gene encodes
two non-structural replication-associated proteins: small T
antigen and large T antigen. The late gene codes for the
structural viral proteins VP1, VP2, and VP3, respectively.
4. •The first vector used for mammalian cell was
based on SV40 virus genome.
•SV40 served as the model virus to study
molecular and biochemical processes in
eukaryote organisms.
•SV-40 is a small virus, that infects
monkey(simian).
•In macaques, SV40 causes chronic
5. •Children who received the SV40-contaminated
poliovirus vaccine did not develop an adaptive
immune response to the virus particles.
•Hence, SV40 is non-immunogenic.
•The viral particles prevent activation of TLRs,
escape from the proteasome, and thus evade
antigen presentation to cells of the host’s
immune system during this initial stage of
infection.
6. •This implies that SV40 after its entrance into
permissive cells is able to efficiently evade TLR
binding and prevents presentation of viral antigens
on MHC molecules to cells of the host’s immune
system.
•Genome of many viruses such as adenovirus and
papilloma viruses, which have a relatively high
insert capacity are used as vectors for
cloning/expression of genes in mammalian cells.
•REPLICATION - The circular double-stranded DNA
starts replicating from the ORI and proceeds as a
7. MULTIPLICITY REACTIVATION
• SV40 is capable of multiplicity reactivation (MR).
• MR is the process by which two or more virus genomes
containing otherwise lethal damage interact within an infected
cell to form a viable virus genome.
• Under conditions in which only a single virus particle entered
each host cell, approximately one DNA cross-link was lethal to
the virus and could not be repaired. In contrast, when multiple
viral genomes infected a host cell, MR occurred.
8. WHY CHOOSE SV40?
• rSV40s are good candidate vehicles for gene transfer: they are
easily modified to be non-replicative and they are non-
immunogenic.
• Further, they infect a wide variety of cells and allow long-
term transgene expression.
• The macaque polyomavirus Simian Virus 40 (SV40) is unique in
its capacity to evade intracellular antiviral defense responses
upon cell entry.
• The non-immunogenicity in its natural host is not only of
benefit to the virus but also to us in developing effective SV40
vector-based treatments for today’s major human diseases.
9. PRESENCE OF SV-40 IN HUMAN
POPULATION
• In humans, polyomaviral particles can be found in the
kidney and urine of immunocompetent individuals and
in kidney, brain, lung, or peripheral blood
mononuclear cells in immunocompromised
individuals.
10. SV40 AND CANCER
• Like other polyomaviruses, SV40 is a DNA virus that has the
potential to cause tumors in animals, but most often persists as
a latent infection.
• Simian virus 40 (SV40) is known to cause tumourigenesis.
• The main types of tumour induced by SV40 in laboratory
animals mirror the human cancers that have been found to
contain SV40 DNA or the viral oncoprotein.
• It is currently unclear whether SV40 has any role in causing
tumors.
