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Boopathy AV, Nekkalapudi A, Sung J, Schulha S, Jin D, Sharma B, Ng S, Lu S, Wimmer R, Suthram S, Ahmadi-Erber S, Lauterbach H, Orlinger KK, Hung M, Carr B, Callebaut C, Geleziunas R, Kuhne M, Schmidt S, Falkard B. Flt3 agonist enhances immunogenicity of arenavirus vector-based simian immunodeficiency virus vaccine in macaques. J Virol 2024:e0029424. [PMID: 38829139 DOI: 10.1128/jvi.00294-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Accepted: 05/07/2024] [Indexed: 06/05/2024] Open
Abstract
Arenaviral vaccine vectors encoding simian immunodeficiency virus (SIV) immunogens are capable of inducing efficacious humoral and cellular immune responses in nonhuman primates. Several studies have evaluated the use of immune modulators to further enhance vaccine-induced T-cell responses. The hematopoietic growth factor Flt3L drives the expansion of various bone marrow progenitor populations, and administration of Flt3L was shown to promote expansion of dendritic cell populations in spleen and blood, which are targets of arenaviral vectors. Therefore, we evaluated the potential of Flt3 signaling to enhance the immunogenicity of arenaviral vaccines encoding SIV immunogens (SIVSME543 Gag, Env, and Pol) in rhesus macaques, with a rhesus-specific engineered Flt3L-Fc fusion protein. In healthy animals, administration of Flt3L-Fc led to a 10- to 100-fold increase in type 1 dendritic cells 7 days after dosing, with no antidrug antibody (ADA) generation after repeated dosing. We observed that administration of Flt3L-Fc fusion protein 7 days before arenaviral vaccine increased the frequency and activation of innate immune cells and enhanced T-cell activation with no treatment-related adverse events. Flt3L-Fc administration induced early innate immune activation, leading to a significant enhancement in magnitude, breadth, and polyfunctionality of vaccine-induced T-cell responses. The Flt3L-Fc enhancement in vaccine immunogenicity was comparable to a combination with αCTLA-4 and supports the use of safe and effective variants of Flt3L to augment therapeutic vaccine-induced T-cell responses.IMPORTANCEInduction of a robust human immunodeficiency virus (HIV)-specific CD4+ and CD8+ T-cell response through therapeutic vaccination is considered essential for HIV cure. Arenaviral vaccine vectors encoding simian immunodeficiency virus (SIV) immunogens have demonstrated strong immunogenicity and efficacy in nonhuman primates. Here, we demonstrate that the immunogenicity of arenaviral vectors encoding SIV immunogens can be enhanced by administration of Flt3L-Fc fusion protein 7 days before vaccination. Flt3L-Fc-mediated increase in dendritic cells led to robust improvements in vaccine-induced T- and B-cell responses compared with vaccine alone, and Flt3L-Fc dosing was not associated with any treatment-related adverse events. Importantly, immune modulation by either Flt3L-Fc or αCTLA-4 led to comparable enhancement in vaccine response. These results indicate that the addition of Flt3L-Fc fusion protein before vaccine administration can significantly enhance vaccine immunogenicity. Thus, safe and effective Flt3L variants could be utilized as part of a combination therapy for HIV cure.
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Affiliation(s)
| | | | - Janette Sung
- Drug Metabolism, Gilead Sciences, Inc., Foster, California, USA
| | | | - Debi Jin
- Protein Therapeutics, Gilead Sciences, Inc., Foster, California, USA
| | - Bhawna Sharma
- Discovery Virology, Gilead Sciences, Inc., Foster, California, USA
| | - Sarah Ng
- Oncology, Gilead Sciences, Inc., Foster, California, USA
| | - Sabrina Lu
- Protein Therapeutics, Gilead Sciences, Inc., Foster, California, USA
| | | | - Silpa Suthram
- Bioinformatics, Gilead Sciences, Inc., Foster, California, USA
| | | | - Henning Lauterbach
- Global Research and Development, Hookipa Pharma Inc., New York, New York, USA
| | - Klaus K Orlinger
- Global Research and Development, Hookipa Pharma Inc., New York, New York, USA
| | - Magdeleine Hung
- Protein Therapeutics, Gilead Sciences, Inc., Foster, California, USA
| | - Brian Carr
- Drug Metabolism, Gilead Sciences, Inc., Foster, California, USA
| | | | - Romas Geleziunas
- Clinical Virology, Gilead Sciences, Inc., Foster, California, USA
| | - Michelle Kuhne
- Oncology, Gilead Sciences, Inc., Foster, California, USA
| | - Sarah Schmidt
- Virology, Hookipa Pharma Inc., New York, New York, USA
| | - Brie Falkard
- Clinical Virology, Gilead Sciences, Inc., Foster, California, USA
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