Sustained protective rabies neutralizing antibody titers after administration of cationic lipid-formulated pDNA vaccine

Abstract

Published data indicate that formulation of pDNA with cationic lipids could greatly enhance the response to a pDNA vaccine in larger mammals. The present work tested the influence of several pDNA:cationic lipid formulations on rabies neutralizing titers. Plasmid expressing Rabies G protein (CVS strain) was evaluated in vivo for ability to elicit neutralizing titers. pDNA:DMRIE-DOPE formulated at two DNA:cationic lipid molar ratios was compared in mice to a Vaxfectin-pDNA formulation. Mouse data indicate that Vaxfectin is more effective than DMRIE-DOPE in eliciting neutralizing titers. In addition, the ratio of pDNA to DMRIE-DOPE can also affect neutralizing titers. Our data show that sustained neutralizing titers (120 days) can be obtained after a single administration of DMRIE-DOPE-formulated pDNA in rabbits.

Figure 1

Sustained High Protective Titers after pDNA vaccination. Two groups of three rabbits were vaccinated with either 1 mg of rabies G protein pDNA VR7203 (Days 1, 28 and 56) (Δ) or with a single administration of IMRAB^® 3 (●) as described in Materials and Methods. pDNA:cationic lipid molar ratio was kept at 4:1. Data points represent individual animal titers. Lines connect mean titer values for each group at each time point. Protective titer threshold (0.5 IU/mL) is indicated with a horizontal line. Vaccination days are indicated with downward arrows.

Figure 2

Neutralizing Titers after Single Administration of PDNA:DMRIE-DOPE in rabbits. Groups of three rabbits were vaccinated with either 300 μg (○; dotted line) or 10 μg (Δ; dashed line) of rabies G protein pDNA VR7203 as described in Materials and Methods. pDNA:cationic lipid molar ratio was kept at 4:1. Control group was vaccinated with IMRAB^® 3(●; solid line). Lines connect mean titer values for each group at each time point. Protection threshold (0.5 IU/mL) is indicated with a horizontal line.

Figure 3

Neutralizing Titers after single administration of cationic lipid-formulated pDNA in mice. Data points indicate individual animal neutralizing titers 48 Days after vaccination with either 2 μg or 5 μg of cationic lipid-formulated pDNA. GMT values for each group are also indicated (▬). pDNA was formulated with either DMRIE-DOPE (D:D; 4:1 or 2.5:1 molar ratio) or Vaxfectin™ (4:1 molar ratio) as described in Materials and Methods. Protection threshold (0.5 IU/mL) is indicated with a horizontal line.