Download Virus vaccines

LECTURE 18:
Virus vaccines
Waqas Nasir Chaudhry
Viro100:
Virology
3 Credit hours
NUST Centre of Virology & Immunology
Live recombinant virus
vaccines
• A recombinant vaccinia virus engineered to
contain the gene for the rabies virus G protein
has been used to vaccinate wild mammals
against rabies
Live recombinant virus vaccines
Virus like particles
• Virus-like particles are structures assembled
from virus proteins
• The particles resemble virions, but they are
devoid of any nucleic acid
• Therefore be deemed safer than vaccines
containing attenuated or inactivated virions
• Hepatitis B virus (HBV) vaccine is produced in
recombinant yeast cells that have the gene for
the HBsAg inserted into the genome
• The cells are grown in bulk and then broken to
release the virus protein.
• After purification the HBsAg molecules receive
a chemical treatment that causes them to
aggregate into spherical structures similar to
the non-infectious of HBV
• The major capsid protein of papillomaviruses
can self assemble into virus-like particles that
bear the epitopes required for generating
neutralizing antibodies
Synthetic peptide vaccines
• Each protein antigen has one or more
epitopes
• These short amino acid sequences can be
synthesized in a machine and it was suggested
that the resulting peptides might be used as
vaccines
• Compared with traditional vaccines it would
be easier to ensure the absence of
contaminants such as viruses and proteins
• A lot of work has been done to try to develop
peptide vaccines against foot and mouth
disease virus
• In this virus there is an important epitope
within the virion protein VP1
• Synthetic peptides of this sequence induced
reasonable levels of neutralizing and
protective antibodies in laboratory animals
• but when vaccine trials were done in farm
animals the results were disappointing
DNA vaccines
• The most revolutionary approach to vaccination
is the introduction into the vaccinee of DNA
encoding an antigen, with the aim of inducing
cells of the vaccinee to synthesize the antigen
• One advantage of this approach is that there is a
steady supply of new antigen to stimulate the
immune system
• Because the antigen (a virus protein in this case)
is produced within the cells of the vaccinee, it is
likely to stimulate efficient T-cell-mediated
responses
Production of a DNA vaccine. The virus protein gene is inserted into a plasmid, which is
then cloned in bacteria. The plasmid is extracted from the bacterial cells, purified and
incorporated into a vaccine
Storage and transport of vaccines
• Once a vaccine has been manufactured there is a need
to preserve its efficacy until it is used
• For live vaccines this means preserving virus infectivity
• For vaccines containing inactivated virions, subunits
and virus-like particles it means preserving
immunogenicity
• Most vaccines are stored and transported at low
temperatures this minimizes losses of infectivity and
immunogenicity
• Substances that reduce the rate of infectivity loss are
included in some vaccines, an example being
magnesium chloride in live polio vaccines
Low temperature storage of virus vaccines