Alternative Start Sites Downstream of Non-Sense Mutations Drive Antigen Presentation and Tolerance Induction to...

Area of Science:

• Immunology
• Gene Therapy
• Molecular Biology

Background:

• Cytotoxic T lymphocyte (CTL) responses to transgene products are a key concern in gene therapy.
• Genetic mutations, particularly premature termination codons (PTCs), can alter T cell responses to gene therapy vectors.
• Individuals with PTCs may lack immune tolerance to C-terminal epitopes due to absent endogenous antigen presentation.

Purpose of the Study:

• To investigate if human ornithine transcarbamylase (OTC) genes with PTCs can generate and present epitopes downstream of the termination codon.
• To determine if expression of these PTC-containing OTC genes via adeno-associated virus (AAV) vectors can induce peripheral tolerance in mice.

Main Methods:

• Utilized human OTC genes with various PTC-inducing nonsense mutations.
• Employed adeno-associated virus (AAV) vectors for gene delivery in C57BL/6 mice.
• Analyzed epitope generation and presentation from alternative translation start sites downstream of the stop codon.

Main Results:

• PTC-inducing nonsense mutations in the human OTC gene can generate and present epitopes downstream of the termination codon.
• Alternative translation start sites downstream of the stop codon are the primary mechanism for epitope generation.
• AAV-mediated expression of these PTC-containing OTC genes induced peripheral tolerance to downstream epitopes in C57BL/6 mice.

Conclusions:

• Despite the absence of full-length endogenous protein, patients with PTC-inducing nonsense mutations may present T cell epitopes downstream of the PTC.
• This presentation of downstream epitopes can potentially induce tolerance to wild-type transgene products in gene therapy recipients.