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Modified mRNA Encoding the Crimean-Congo Hemorrhagic Fever Virus Nucleocapsid Protein Confers Robust Protection
Sercan Keskin1,2, Shaikh Terkis Islam Pavel3,4, Rabia Sak1,5
1Department of Biotechnology, Institute of Health Sciences, Bezmialem Vakif University, Istanbul, Türkiye.
Insights
A new messenger ribonucleic acid (mRNA) vaccine candidate shows promise for Crimean-Congo Hemorrhagic Fever Virus (CCHFV). This nucleocapsid protein (NP)-based vaccine demonstrated 100% survival in mice challenged with CCHFV, offering a potential breakthrough for this high-priority pathogen.
Area of Science:
- Virology and Immunology
- Vaccine Development
- Molecular Biology
Background:
- Crimean-Congo Hemorrhagic Fever Virus (CCHFV) is a WHO priority pathogen with high mortality (up to 40%) and no approved vaccine.
- CCHFV's widespread endemicity, human-to-human transmission potential, and lack of treatment necessitate urgent vaccine development.
- Messenger ribonucleic acid (mRNA) vaccine technology has proven successful, as demonstrated during the COVID-19 pandemic.
Purpose of the Study:
- To develop and evaluate an mRNA vaccine candidate targeting the CCHFV nucleocapsid protein (NP).
- To assess the preclinical efficacy of a pseudouridine-modified mRNA vaccine encoding CCHFV NP in mouse models.
Main Methods:
- Designed and synthesized pseudouridine-modified mRNA (IVT NP-ΨmRNA) encoding CCHFV NP.
- Confirmed biochemical and immunological properties of NP in vitro.
- Evaluated vaccine efficacy in immunocompetent BALB/c and immunosuppressed (IS) C57BL/6 mice, including challenge studies with lethal CCHFV doses.
- Administered two doses of naked or PLGA-encapsulated IVT NP-ΨmRNA or unmodified mRNA 14 days apart.
Main Results:
- Immunization with IVT NP-ΨmRNA induced robust CCHFV NP-specific humoral (IgM, IgG) and cellular (cytokine, lymphoproliferative) responses in BALB/c mice.
- Both naked and PLGA-encapsulated IVT NP-ΨmRNA achieved 100% survival in IS C57BL/6 mice following lethal CCHFV challenge.
- Unmodified IVT NP-mRNA vaccination resulted in only 20% survival, while inactivated CCHFV vaccine showed 100% survival.
- Viral clearance was observed in spleen, liver, and blood of protected mice by day 14 post-challenge.
Conclusions:
- Pseudouridine-modified mRNA encoding CCHFV NP provides significant survival benefits in a lethal CCHFV mouse model.
- The NP protein is a viable target for CCHFV vaccine development, demonstrating protective immunity.
- This study provides a strong foundation for further preclinical development of NP-based mRNA vaccines against CCHFV.
Abstract:
The Crimean-Congo Hemorrhagic Fever Virus (Orthonairovirus haemorrhagiae) causes a hemorrhagic fever with mortality rates reaching up to 40%. For years, this virus has maintained its position among the top priority pathogens identified by the World Health Organization (WHO). This is due to its endemic presence across a vast region-from Africa and Spain to the Balkans, the Middle East, and throughout Asia-its potential for human-to-human transmission, and the lack of an effective and approved vaccine or treatment. Therefore, the development of an effective vaccine against CCHFV is of critical importance. Building on the success of mRNA-based vaccines during the Coronavirus Disease 2019 (COVID-19) pandemic, this study reports the development of a messenger ribonucleic acid (mRNA) vaccine candidate expressing the nucleocapsid protein (NP) of CCHFV. The CCHFV NP in vitro transcript (IVT) was designed with pseudouridine (Ψ) nucleoside modification. As part of the preclinical characterization of the IVT vaccine candidate, the biochemical and immunological properties of NP were confirmed in Huh-7 cells transfected with IVT NP-ΨmRNA. Afterwards, the efficacy of IVT NP-ΨmRNA immunization was evaluated in immunocompetent BALB/c and transiently immunosuppressed (IS) C57BL/6 mice. In CCHFV challenge studies, IS C57BL/6 mice were used. IS C57BL/6 mice were immunized intramuscularly with 2 doses of IVT NP- ΨmRNA, either naked or encapsulated in Poly(lactic-co-glycolic acid) (PLGA) nanoparticles, administered 14 days apart. High levels of CCHFV NP-specific humoral (IgM and IgG) and cellular (cytokine and lymphoproliferative) responses were demonstrated in BALB/c mice immunized with IVT NP- ΨmRNA. In challenge experiments, 100% survival was observed with both the naked and PLGA-encapsulated IVT NP-ΨmRNA immunizations. These findings demonstrate 100% survival following lethal CCHFV challenge under the experimental conditions tested in this mouse model and support the potential of NP-encoding pseudouridine-modified mRNA vaccines. Additionally, 100% survival was observed in mice immunized with inactivated CCHFV, whereas only 20% survival was detected in the unmodified IVT NP-mRNA vaccinated animals. In the protected mice, viral clearance was observed in the spleen, liver tissues, and blood on day 14 post-challenge. This study demonstrates that NP, the most abundant protein of the virus, is capable of providing significant survival benefits in the tested mouse model. Furthermore, our report represents a significant step in identifying a potential vaccine candidate and provides a solid foundation for further preclinical studies necessary to support future clinical development.
