Protection of Baculovirus Vectors Expressing Complement Regulatory Proteins against Serum Complement Attack

Area of Science:

• Biotechnology
• Gene Therapy
• Virology

Background:

• Baculovirus vectors (BVs) are utilized for gene delivery in mammalian cells, including applications in gene therapy.
• BVs are susceptible to inactivation by the complement system, limiting their therapeutic potential.
• Previous work involved developing BVs expressing malaria sporozoite surface proteins for liver cell targeting.

Purpose of the Study:

• To develop BVs expressing complement regulatory proteins (CRPs) on their surface to inhibit complement-mediated inactivation.
• To evaluate the efficacy of BVs engineered with decay accelerating factor (DAF; CD55) and a CD46-DAF-CD59 fusion construct in resisting complement attack and enhancing gene delivery.

Main Methods:

• Baculovirus vectors were engineered to express DAF (CD55) or a CD46-DAF-CD59 fusion protein on their surface.
• The complement resistance of engineered BVs was assessed using HepG2 cells in the presence of complement-active serum.
• Transduction efficacy and the formation of the membrane attack complex (MAC) were measured to evaluate BV performance.

Main Results:

• BVs expressing DAF (DAF-type BVs) showed increased complement resistance compared to control BVs, but with reduced transduction efficacy.
• BVs expressing the CD46-DAF-CD59 fusion construct exhibited significantly higher transduction efficacy and enhanced complement resistance than both control and DAF-type BVs.
• Both DAF-type and CD46-DAF-CD59 type BVs effectively repressed the formation of the membrane attack complex induced by BV-mediated complement activation.

Conclusions:

• The CD46-DAF-CD59 fusion construct provides superior complement protection compared to the DAF-only construct for baculovirus-mediated gene delivery.
• Engineering BVs with specific CRPs can overcome complement-mediated inactivation, improving their utility in gene therapy and other applications.
• These findings highlight a promising strategy for enhancing the safety and efficiency of baculovirus vectors in complement-rich environments.