Despite frequently promising results in pre-clinical models, to date, in humans recombinant viral vaccines have been neutralised and cleared too quickly by the immune system defences before they are able to reach target cells. The human immune system is just "too good" and this has been shown to limit the effectiveness of many recombinant viral vaccine candidates. PolySTAR overcomes this basic problem faced by all recombinant viral vectors.
What is PolySTAR
PolySTAR is a polymer coated recombinant viral vector system that avoids pre-existing anti-vector immunity but still targets the vaccine to antigen presenting cells.
The need for PolySTAR
For over two decades, recombinant virally vectored vaccines have promised to revolutionise the field of vaccines. This approach utilises a safe, non-replicating virus particle (such as an adenovirus) that has been modified using recombinant technology to express important components of a harmful pathogen (such as influenza or HIV) directly within cells of the immune system. In a sense the vector virus is a Trojan horse for the antigens of interest. The logic of this recombinant approach is to use the advantages of live viral vaccines, including increased efficacy and cell mediated immunity, without the drawbacks of poor safety and reversion to wild type with resultant virulence.
The problem arises when the human immune system develops immunity to the vector itself. Leading vaccinology experts have described this problem.
"The results from the Merck trial are going to push people to come up with strategies in which pre-existing immunity is not going to be a problem,"
Gary Kobinger of the National Microbiology Laboratory, Public Health Agency of Canada, Manitoba.
"Increasing the vaccine dose seemed to overcome, at least partially, the impact of pre-existing immunity to Ad5, but the response rates were still much worse than in those subjects with low, less than [1:200], Ad5 antibody titers."
Robin Isaacs, executive director of HIV vaccine clinical research at Merck.
"If you vaccinate everyone in a population with an HIV adenovirus vaccine, you can't turn around and use the same vector against malaria,"
Hildegund Ertl, Wistar, Penn.
All quoted from: 1] Immunity's yin and yang: A successful vaccine must first avoid being eliminated by pre-existing immunity before it can promote a protective immune response (IAVI Report 10(1) 2006)
Market potential
Vaccines continue to be a phenomenal success story for pharmaceutical companies. The world market for preventative vaccines totaled over $22 billion in 2009, a 16% increase on 2008 and predicted to increase at a compound annual rate of 9.7% during the next five years [2]. The potential for significant growth and uptake of therapeutic vaccines will only add to this significant growth potential in the longer term.
In order to drive growth in the vaccine sector, and in particular in order to enter the demanding therapeutic vaccine sector, it is imperative to have new technologies that will enhance vaccine safety and efficacy. The hunger of the major players to develop new products in this sector is demonstrated particularly by the large corporate deals related to vaccine delivery and adjuvant platforms.
