Important step forward for safety of xenotransplantation --
Cambridge, MA, February 13, 2004 -- This week in the Journal of Virology (1 March 2004, Vol 78 No 5), researchers from Immerge BioTherapeutics, Inc., announced that the porcine endogenous retroviruses (PERVs) that are most infectious for human cells are not components of the germ line DNA of miniature swine, as previously thought. This is a crucial discovery with regard to developing modes of eliminating these viruses from pigs being developed for clinical xenotransplantation. It suggests that lengthy breeding programs, which were thought to be necessary to remove germ-line viruses, might no longer be required.
"Our identification that human-tropic PERV is acquired somewhere during life, rather than something the pig is born with is a major step forward. It allows us to develop measures that will ensure these viruses are not present in cells and organs of miniature swine destined for clinical use," said Dr Clive Patience, Director of the Safety Program at Immerge. "We did not identify any viruses in the germ-line DNA of the miniature swine that could infect human cells. On the rare occasion that we could infect human cells, the viruses were exogenous recombinants that we believe we can control through standard methods in breeding and raising microbiologically-clean pigs."
Although risk of PERV infection in xenotransplantation had previously been theoretical, the issue became of critical concern when it was reported that germ-line forms of PERV could infect some human cells in laboratory tissue cultures (Patience et al., Nature Medicine; 3: 282-6, 1997). The new data regarding exogenous PERV was generated in a collaborative effort between Immerge and the academic research group of Professor David Onions and Linda Scobie at the University of Glasgow, UK.
"PERV is of concern in developing xenotransplantation of porcine organs towards an accepted procedure in clinical medicine," commented Professor Onions. "This discovery is an important step toward the development of donor tissues and organs for clinical xenotransplantation that lack all infectious PERV."
There is a critical need to identify new sources of organs for the growing number of people needing life-saving transplants around the world. In the U.S. alone, there are more than 81,000 people on the waiting list for organs and an unknown number of additional people needing organs who did not qualify for the transplant list because of age, illness or other issues. Each day, 17 patients die while on this waiting list. The theoretical risk of PERV infection in humans has been considered a critical barrier to xenotransplantation. To address this barrier, Immerge BioTherapeutics Inc. has developed a broad safety program with a number of international experts collaborators.
"PERV research is an important part of our research and development program" stated Julia Greenstein, Ph.D., CEO and President of Immerge. "Our work continues to indicate that PERV appears to be a very manageable concern clinically, allowing us to continue our progress toward clinical xenotransplantation in the near future."
The depth of Immerge's safety program is unique among other companies conducting xenotransplantation research. The company has previously reported the identification of animals within its miniature swine herd that do not transmit PERV to human cell lines (Oldmixon et al. Journal of Virology 2002; 76: 3045-3048). In the past year, in collaborative efforts with the University of Missouri-Columbia and Infigen, Inc., Immerge also announced the birth of cloned, double knock-out miniature swine that lack expression of the GGTA1 gene. This gene is responsible for rapid rejection of organs and makes the animal organs more compatible for potential human transplant.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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