Enhanced HIV immune responses elicited by an apoptotic single-cycle SHIV lentivector DNA vaccine

Deepanwita Bose ¹ Kenneth A Rogers ¹ Lisa M Shirreff ¹ Yahia Chebloune ² Francois J Villinger ^1*

• ¹ New Iberia Research Center, University of Louisiana at Lafayette, New Iberia, United States
• ² Université Grenoble Alpes, Saint Martin d'Hères, Auvergne-Rhone-Alpes, France

Background: HIV remains a major public health issue in spite of ART. An innovative vaccine that can induce a long-lasting and effective immunity is required to curb the persistent high numbers of new infections worldwide.: A novel DNA vaccine was generated using a SHIV backbone with a Zambian T/F clade C envelope and under the control of the Caprine Arthritis Encephalitis virus LTRs for constitutive expression. Due to the deleted integrase, this DNA vaccine "CSH-DIN-T/F Z331" performs only a single replication cycle. To increase immunogenicity, we tested the coexpression of apoptotic genes (BAX, BAK, or Caspase 8) incorporated at the end of Pol to promote the release of apoptotic bodies taken up by dendritic cells leading to cross-presentation of antigen. The three vaccines (CSH-DIN-T/F Z331-BAX, CSH-DIN-T/F Z331-BAK and CSH-DIN-T/F Z331-Cas8) were tested in vitro for expression and in vivo in Balb/cJ mice for immunogenicity. Results: Transduced HEK293 cells co-cultured with CEMx174 confirmed the single replication cycle of the DNA vaccine and induction of apoptosis by the CSH-DIN-T/F Z331-Cas8 based on Annexin V expression. BALB/cJ mice were immunized with a combined intramuscular + intradermal/ electroporation approach. ICS from splenocytes collected 12 weeks post prime/6 weeks post boost demonstrated a clear superiority of the Caspase 8 expressing construct over the others, with higher proportions of IFN-γ, IL-2, and IL-21 producing CD8 T cells specific to Env, Gag, and Nef. The kinetics of immune response after various immunization schedules were also investigated. Conclusion: This novel single-cycle DNA vaccine with apoptotic genes demonstrated an enhanced immunogenicity primarily for antigen-specific CD8+ T-cell response.