Helpers for efficient encapsidation of SV40 pseudovirions

Area of Science:

• Molecular Biology
• Virology
• Gene Therapy

Background:

• Simian virus 40 (SV40) pseudovirions are effective for gene delivery into various cell types, including human hemopoietic cells.
• Preparation typically involves wild-type (wt) SV40 as a helper, but parameters influencing helper function require investigation.

Purpose of the Study:

• To investigate parameters essential for SV40 pseudovirion helper function.
• To identify efficient helper plasmids and viral constructs for pseudovirion production.
• To explore the role of T-antigen in gene amplification within human hemopoietic cells.

Main Methods:

• Evaluation of plasmid constructs (e.g., pBR322-containing plasmids, pSVPiC) for helper function.
• Construction and characterization of a defective SV40 virus (SLT3).
• Packaging efficiency assessment and analysis of pseudovirion composition (T-antigen positive/negative).

Main Results:

• Plasmids with prokaryotic sequences (pBR322) were inefficient helpers due to interference with SV40 late gene expression.
• Plasmid pSVPiC and defective virus SLT3 demonstrated efficient helper functions.
• SLT3, lacking prokaryotic sequences, was efficiently packaged into defective (T-antigen-negative) virions.
• Recombination of pSVPiC generated infectious SV40 particles.
• Mixtures of T-antigen positive and negative pseudovirions were produced.

Conclusions:

• Plasmid design significantly impacts helper function for SV40 pseudovirion production.
• SLT3 represents an efficient, small-sized helper for generating T-antigen-negative pseudovirions.
• The availability of both T-antigen positive and negative pseudovirions suggests T-antigen's role in driving gene amplification in human hemopoietic cells.