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5 Genetic Analysis of Cell Targeting and Immunogenicity of VEE Vectors
A. West*1, E. Richmond1, E. Reap2, S. Dryga2, M. Collier1, G. MacDonald1, M. Connell3, P. Johnson3, N. Davis1, and R. Johnston1
1Univ. of North Carolina, Chapel Hill, USA; 2AlphaVax, Inc., Res. Triangle Park, NC, USA; 3 Children's Res. Inst., Columbus, OH, USA
Background: Replicon vectors based on Venezuelan equine encephalitis virus (VEE) contain a self-replicating RNA encoding the VEE replicase proteins and expressing a gene of interest substituted for the VEE structural protein genes. Replicon RNA is encapsidated into VEE replicon particles (VRP) by supplying VEE capsid and envelope glycoproteins in trans. To enhance the safety of VRP vaccines, attenuating mutations have been embedded in the glycoprotein helper constructs. VRP expressing immunizing genes from a wide variety of pathogens have proven to be safe and effective vaccines in animal models, including primates. Effects of glycoprotein mutation on VRP targeting and immunogenicity were examined in this study.
Methods: Replicon vectors expressing gfp, influenza HA, or HIV clade C Gag were packaged into VRP using wild-type and mutant envelopes. Wild-type and mutant VRP were inoculated into mice by different routes to determine the effects on cell targeting in the draining lymph node, induction of serum antibodies and CTL.
Results: VRP enveloped with wild-type (V3000) glycoproteins target efficiently to dendritic cells (DC) in the draining lymph node from a footpad inoculation and efficiently induce both antibody and CTL at extremely low doses. VRP enveloped in mutant V3014 glycoproteins were much less efficient in DC targeting and immunogenicity. Mutant V3040 envelopes gave V3000-like targeting and immunogenicity, whereas mutant V3042 envelopes appeared less efficient in DC targeting yet were more immunogenic than V3000 enveloped VRP. The differential immunogenicity was especially apparent with subcutaneous inoculation. Analogous studies are underway in macaques.
Conclusions: V3014 was the mutant envelope used in mice and macaques for successful immunization and challenge studies with VRP vaccines against a number of pathogens, including Marburg, SIV, and influenza. These results suggest that significant improvement in these vaccines will be obtained using alternative envelopes that contain mutations to enhance the safety profile while maintaining or improving the immunogenicity characteristic of VRP enveloped in the wild-type glycoproteins.
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