Conditional Knockout Alleles in Transgenic Pigs for Xenotransplantation
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Solution Overview
Problem
The challenge in xenotransplantation is the late graft loss due to chronic rejection and the toxicity of long-term immunosuppression required to prevent xenograft rejection, along with the lack of reliable markers for immunological tolerance, which affects the durability of mixed chimeric cells and the health of donor animals.
Innovation Solution
The development of transgenic pigs with conditional knockout alleles of target genes that express human transgenes under the native regulatory sequence, allowing for controlled expression of cytokines, adhesion molecules, and complement regulatory proteins, enhancing graft tolerance and longevity while minimizing deleterious effects on the donor animal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If human transgenes are introduced into porcine donor animals to overcome competitive disadvantage in hematopoiesis, then mixed chimerism durability and graft tolerance are improved, but the health of the donor animal deteriorates due to deleterious effects of long-term transgene expression
Solution Approach 1:
The patent applies preliminary action by inserting a conditional knockout allele upstream of the transgene before the transgene is activated. This allows the system to be prepared in advance with a control mechanism that can be activated later to prevent harmful effects. The conditional knockout allele is positioned to enable future deletion of the transgene or its regulatory elements, thereby preventing donor animal health deterioration while maintaining initial chimerism durability benefits.
Solution Approach 2:
The patent implements dynamics by making transgene expression conditional rather than constitutive. The expression of human transgenes in porcine donor animals is controlled by a conditional knockout allele that can be activated or deactivated based on physiological needs. This dynamic control allows the system to switch between states of transgene expression and non-expression, optimizing both chimerism durability and donor animal health at different time points.
2Duration of action of moving object
If transgenic expression is activated in donor animals to improve graft tolerance, then xenograft survival is improved, but the donor animal experiences toxic effects from long-term immunosuppression
Solution Approach 1:
The patent applies preliminary action by establishing a conditional knockout allele in the donor animal's genome before transplantation. This pre-positioned control element allows for later activation to terminate transgene expression or modify its levels, thereby preventing the accumulation of toxic immunosuppressive effects while maintaining the initial benefits for xenograft survival and tolerance.
Solution Approach 2:
The patent implements periodic action through the conditional knockout mechanism that allows transgene expression to be activated and deactivated in response to physiological conditions or treatment protocols. This periodic control enables the system to provide immunosuppression when needed for graft survival while allowing periods of reduced or eliminated immunosuppression to minimize toxic effects on the donor animal.
Data Source
AI summary
The invention provides for transgenic donor animals (e.g., pigs) whose cells, tissues and organs have a better long-term survival when transplanted into a human patient. The transgenic donor animal carries one or more human transgenes which is expressed only when the endogenous gene of the donor animal is knocked out shortly before a graft is harvested for transplantation. This “genetic switch” allows the donor animal to remain healthy during the majority of its lifetime, while still allowing expression of the human transgene for optimal transplant tolerance in a human recipient. The transgene may encode a cytokine receptor, an adhesion molecule, or a complement regulatory protein.