With the advent of sequencing, emergence of novel strains could be tracked. These strains have emerged to favour the new environment. Simultaneously, these strains may have some potential to be a vaccine candidate. Please help us in searching for the criteria for a strain to be used in vaccinations.
A good starting point is to isolate the strain from an asymptomatic carrier. The carrier must be asymptomatic for a long time.
This is correct. Ideally said pathogenic genes should have disappeared during the attenuation
Vaccine candidate strain is to be fully characterised and tto be qualified to use and strain to demonstrate safety, immunogenecity /antigenicity and good yields.
I too believe the role of sequence conservation and protein families in evolution of pathogenesis.
The vaccine against human papillomavirus is a good example: The transforming proteins E6 and E7 are not included in the vaccine. He is protective with the included structural protein L1.
The foremost prerequisites for a strain to be used for vaccine development are
(i) vaccines made from the strains should be highly effective against wide range of pathogenic strains of a species (homologous and heterologous protection). This can be achieved by identifying one or more epitopes that are conserved among all disease-causing strains of a pathogenic species
(ii) Antigenic matching: How closely is the strain related to the field microbe against which the protection is desired.
Microbial cells and their derivatives used as the vaccine drug substance include whole cell vaccines (live or killed), crude lysate or purified immunogens, recombinant DNA products, conjugates, and plasmid DNA vaccines.
The history and characteristics of each strain used to produce the vaccine and a complete strain description should be provided, including:
• origin of isolate;
• species;
• biochemistry (fermentation profile, etc.);
• strain identifier and specific identifying characteristics (serotype, etc.);
• virulence (attenuation method, if performed);
• genetic characterization, if known (markers, inserts, deletions, etc.);
• plasmids; and
• genetic stability.
The selected strain for vaccine production should also be approved by the appropriate national regulatory agency (NRA). The vaccine produced from the strain should assure the quality, safety and efficacy parameters.
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