PF-D-Trimer, a protective SARS-CoV-2 subunit vaccine: immunogenicity and application

Area of Science:

• Vaccinology
• Virology
• Immunology

Background:

• The COVID-19 pandemic, caused by SARS-CoV-2, necessitates effective vaccines.
• The SARS-CoV-2 spike protein is a key target for host immune responses.

Purpose of the Study:

• To present preclinical studies of a broadly protective SARS-CoV-2 subunit vaccine candidate, PF-D-Trimer.
• To evaluate antigen design, purification, vaccine efficacy, and manufacturability.

Main Methods:

• Developed a pre-fusion trimerized Delta spike protein (PF-D-Trimer) using a Trimer Domain platform.
• Expressed and purified PF-D-Trimer using Chinese hamster ovary (CHO) cells and immunoaffinity chromatography.
• Formulated the vaccine with an adjuvant and assessed stability.

Main Results:

• PF-D-Trimer induced robust immune responses in mouse, rat, and Syrian hamster models.
• The vaccine protected K18-hACE2 transgenic mice against homologous viral challenge.
• Induced neutralizing antibodies showed cross-reactivity against ancestral, Delta, and Omicron variants (including BA.5.2).
• The vaccine formulation is stable for up to six months without refrigeration.

Conclusions:

• The Trimer Domain platform enables rapid production of SARS-CoV-2 vaccines.
• PF-D-Trimer demonstrates broad protective potential and stability, crucial for combating COVID-19.
• This platform technology can accelerate the development of updated SARS-CoV-2 vaccines.