Woodchuck hepatitis virus core antigen-based DNA and protein vaccines induce qualitatively different immune responses that affect T cell recall responses and antiviral effects

- We characterized immune responses to three vaccines: pWHcIm, pCTLA-4-C and WHcAg.
- Pre-primed response determined the characteristics of recall response post challenge.
- The recall response reduced WHV loads in hydrodynamic injection and transgenic mice.
- PCTLA4-C vaccine is protective against hepadanavirus infection by inducing mixed Th1/Th2 responses.

T helper type 1 (Th1) immunity was considered to play a dominant role in viral clearance of hepadnaviral infection. However, pre-primed Th2 type responses were able to efficiently control hepadnaviral infection in animal models. We investigated how pre-primed Th1/2 responses control hepadnaviral replication using the newly established mouse models. DNA (pWHcIm, pCTLA-4-C) and protein vaccines based on the nucleocapsid protein (WHcAg) of woodchuck hepatitis virus (WHV) primed specific immune responses with distinct features. The pre-primed responses determined the characteristics of recall responses if challenged with a WHcAg-expressing adenoviral vector. Vaccination with pWHcIm and pCTLA4-C facilitated viral control in the hydrodynamic injection model and reduced WHV loads by about 3 and 2 logs in WHV-transgenic mice, respectively, despite of different kinetics of specific CD8+ T cell responses. Thus, pre-primed Th2-biased responses facilitate the development of CD8+ T cell responses in mice compared with naïve controls and thereby confer better viral control.