Self-inactivating retroviral vectors with improved RNA processing

Area of Science:

• Molecular Biology
• Virology
• Gene Therapy

Background:

• Retroviral vectors are crucial for gene delivery, but optimizing transgene expression and safety remains a challenge.
• Key RNA features, including 5'UTR introns, absence of aberrant start codons, and 3'UTR post-transcriptional regulatory elements (PREs), enhance retroviral transgene expression.

Purpose of the Study:

• To engineer self-inactivating (SIN) retroviral vectors incorporating beneficial RNA elements for improved safety and expression.
• To evaluate the impact of vector design, specifically promoter insertion site and inclusion of a 5'UTR intron, on vector performance.

Main Methods:

• Excised the strong retroviral promoter from the 3' LTR and inserted it upstream or downstream of the Psi packaging signal to create SIN vectors.
• Compared three LTR and four SIN vector designs to assess titer, splice regulation, and transgene expression.
• Utilized various cell types including embryonic carcinoma cells, fibroblasts, primary T cells, and hematopoietic progenitor cells.

Main Results:

• SIN vectors exhibited approximately 20-fold lower titers than LTR vectors, but inclusion of the PRE enabled titers exceeding 10^6 infectious units/ml.
• Intron-containing SIN vectors demonstrated significantly improved splicing compared to state-of-the-art LTR vectors.
• Transgene expression in SIN vectors matched or surpassed LTR vectors across all tested cell types.

Conclusions:

• SIN vectors incorporating specific RNA elements, particularly a 5'UTR intron and PRE, offer a promising strategy for enhanced and safe gene therapy applications.
• The novel design of SIN vectors with upstream promoter insertion and 5'UTR introns facilitates efficient gene expression and splicing.
• These optimized SIN vectors represent a significant advancement for retroviral gene delivery systems.