Blocking T-cell egress with FTY720 extends DNA vaccine expression but reduces immunogenicity

Area of Science:

• Immunology
• Vaccinology
• Molecular Biology

Background:

• Optimal nucleic acid vaccine immunogenicity depends on balancing antigen expression with immune clearance.
• Cellular responses can limit DNA vaccine antigen expression by destroying antigen-producing cells.

Purpose of the Study:

• To investigate the impact of cellular response and lymphocyte trafficking on DNA vaccine expression and immunogenicity.
• To determine if modulating lymphocyte trafficking affects DNA vaccine transgene expression duration and immune response.

Main Methods:

• Utilized a plasmid DNA construct expressing luciferase to study DNA vaccine expression.
• Administered FTY720 (Fingolimod), a sphingosine 1-phosphate receptor modulator, to block lymphocyte trafficking.
• Assessed transgene expression levels and duration following FTY720 administration.
• Evaluated immune responses (antibody and T-cell) to a DNA vaccine expressing HIV gp140 envelope antigen when co-administered with FTY720.

Main Results:

• Repeated intramuscular administration of DNA vaccine led to diminished luciferase expression, indicating immune-mediated clearance.
• FTY720 treatment significantly prolonged DNA transgene expression by maintaining a constant expression level.
• Blocking lymphocyte egress during primary vaccination did not increase expression during secondary vaccination.
• Increased transgene expression via FTY720 did not enhance overall immune response.
• Co-administration of FTY720 with an HIV DNA vaccine reduced antigen-specific antibody and T-cell responses.

Conclusions:

• The cellular immune response plays a critical role in clearing DNA vaccine expression.
• Effective development of antigen-specific immune responses requires lymphocyte access to the site of antigen expression.
• Modulating lymphocyte trafficking can prolong DNA vaccine expression but may not necessarily enhance immunogenicity and can potentially reduce it.