Oral immunization with virus-like particles elicits Ebola virus-specific humoral and cellular immune responses in...

Ebola virus (EBOV) poses a significant public health threat due to its high case fatality rates and proved human-to-human transmission. While licensed vaccines exist for EBOV, their intramuscular administration presents some logistical challenges in outbreak settings. Oral vaccines offer advantages in accessibility, compliance, and scalability but have not been explored for EBOV.

We developed an orally-administered EBOV vaccine using virus-like particles (VLPs) incorporating the EBOV glycoprotein (GP), nucleoprotein (NP), and viral protein 40 (VP40). VLPs were produced via transfection of HEK-293T cells, concentrated through ultracentrifugation, and characterized by electron microscopy. Female C57BL/6 mice (n = 14) were immunized intramuscularly (30 μg/dose, n = 4) or orally (300 μg/dose, n = 8) with three doses at two-week intervals. Control mice (n = 2) received no immunization. Immune responses were evaluated by ELISA for anti-EBOV- GP, and anti-EBOV-NP antibodies, neutralization assays using recombinant vesicular stomatitis pseudovirus (rVSV-pseudotyped with EBOV-GP), and flow cytometry for the characterization of EBOV-NP-specific CD8⁺ T cells.

Oral immunization with EBOV FPLs induced antigen-specific IgG responses against EBOV-GP and EBOV-NP. Neutralization assays confirmed the presence of serum antibodies capable of inhibiting EBOV-GP pseudotyped virus infection, while flow cytometry analysis revealed development of EBOV-NP-specific CD8⁺ T cells in vaccinated mice. Notably, immune responses in orally vaccinated animals were slightly improved compared to those elicited by intramuscular administration.

This study provides a proof-of-concept that an oral VLP-based EBOV vaccine candidate can induce antigen-specific humoral and cellular immune responses in mice. However, additional studies are required to determine protective efficacy, durability of immunity, safety, optimal dosing regimens, and translatability across relevant animal models before clinical development can be considered.