Antibody responses elicited through homologous or heterologous prime-boost DNA and protein vaccinations differ in functional activity and avidity.

Using a gp120 envelope glycoprotein from the JR-FL strain of human immunodeficiency virus-1 (HIV-1) as a model antigen, the goal of the current study was to evaluate the level and quality of antibody responses elicited by different prime-boost vaccination regimens (protein only, DNA only, DNA plus protein) in rabbits. Our data demonstrated that incorporating DNA immunization as a prime in a heterologous prime-boost regimen was able to elicit a more diverse and conformational epitope profile, higher antibody avidity, and improved neutralizing activity than immunization with only protein. Additionally, this improved neutralizing activity was observed in spite of similar antibody specificities and avidities seen when only DNA vaccination was used, providing additional evidence that the use of a combination immunization regimen increases the protective antibody response. Insights gained from the current study confirmed that the heterologous DNA prime-protein boost approach is effective in eliciting not only high level but also improved quality of antigen-specific antibody responses, and thus may offer a new technology platform to develop better and safer subunit vaccines.