Virus vaccines LECTURE 18: Viro100: Virology 3 Credit hours NUST Centre of Virology & Immunology Waqas Nasir Chaudhry

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