• Vaccine Name: Human metapneumovirus HMPV-VLP F/GC-85473
• Target Pathogen: Human metapneumovirus
• Target Disease: Respiratory tract infection
• Type: Viral-like particles-based vaccine
• Status: Research
• Host Species for Licensed Use: None
• Host Species as Laboratory Animal Model: mouse
• Antigen: Retroviral-based VLP F/GC-85473 displaying HMPV glycoproteins (Lévy et al., 2013)
• Immunization Route: Intraperitoneal injection (i.p.)
• Description: Retroviral-based VLPs (virus like particles) displaying HMPV glycoproteins induced protection against homologous and heterologous HMPV challenge. (Lévy et al., 2013)

Mouse Response

• Vaccination Protocol: Groups of 4–6-week-old BALB/c mice (Charles River Laboratories) were immunized by intraperitoneal injection with 100 µl of concentrated HMPV-VLPs incorporating FC-85473 , F/GC-85473 , FCan98-75, or no GP or with PBS. (Lévy et al., 2013)
• Immune Response: Retroviral-derived VLPs incorporating F alone or in combination with G induced neutralizing antibody responses in mice. Maximal levels of neutralization could be reached after 2 consecutive injections. (Lévy et al., 2013)
• Challenge Protocol: Mice were immunized with VLPs as described above or were infected intranasally with 0.8 × 10^6 TCID50 of either C-85473 or Can98-75 at each time. Twenty-one days after the last immunization, mice were infected intranasally with HMPV strain C-85473 (8 × 10^5 TCID50 /mouse) or Can98-75 (1 × 10^6 TCID50 ) (Lévy et al., 2013)
• Efficacy: Infection by the Can98-75 strain led to 100% mortality by day 8 after challenge in control mice inoculated with PBS as well as with NoEnv-VLPs. In contrast, mice previously infected with the homologous virus, Can98-75, recovered and survived the challenge. Similarly, most mice immunized with HMPV-VLPs survived the challenge, indicating a cross-protection induced by immunization by VLPs harboring non-homologous F or F/G glycoproteins. Challenge with the C-85473 strain of HMPV was sub-lethal due to a slightly lower inoculum than that of Can98-75 virus, since mice immunized with PBS only or with NoEnv-VLPs exhibited profound weight loss yet with 67% survival by day 8 post-challenge. In contrast, mice previously immunized with the homologous virus, C-85473, or with homologous or het- erologous HMPV-VLPs exhibited partial weight loss and survived the challenge. (Lévy et al., 2013)