• Product Name: Yellow Fever vaccine using vaccinia virus expressing YFV prM and E proteins
• Vaccine Ontology ID: VO_0004152
• Type: Recombinant vector vaccine
• Status: Research
• E gene engineering:
  • Type: Recombinant vector construction
  • Description: The vaccinia virus was uses as recombinant vector (Pincus et al., 1992).
  • Detailed Gene Information: Click Here.
• Vector: Vaccinia virus
• Immunization Route: Intraperitoneal injection (i.p.)

• Type: Live, attenuated vaccine
• Status: Research
• Host Species for Licensed Use: None
• Host Species as Laboratory Animal Model: hamster
• Antigen: SARS-CoV-2 spike antigen (Ma et al., 2022)
• Vector: YF17D (Ma et al., 2022)
• Preparation: The live-attenuated YF17D vectored SARS-CoV-2 vaccine candidate (YF-S0) expresses the non-cleavable stabilized prefusion form of the SARS-CoV-2 spike antigen as in-frame fusion within the YF17D-E/NS1 intergenic region. (Ma et al., 2022)
• Immunization Route: Intraperitoneal injection (i.p.)
• Description: Live-attenuated YF17D-vectored COVID-19 vaccine protects from lethal yellow fever virus infection in mouse and hamster models. Vaccine induces protection against SARS-Cov-2 and YFV. (Ma et al., 2022)

Mouse Response

• Host Strain: Outbred Swiss Mice
• Vaccination Protocol: Groups of 20 3-week-old outbred Swiss mice were immunized by intraperitoneal (i.p.) injection with 10^7 PFU of vaccinia virus (VP869) or 10^6 PFU of YFV-17D, and 3 weeks later sera were collected from selected mice (Pincus et al., 1992).
• Challenge Protocol: One half of the mice in each group were then either reinoculated with the recombinant virus (VP869) or YFV-17D, or challenged by intracranial (i.c.) injection with a 1: 10^5 dilution of brain homogenate prepared from suckling mice infected with the French neurotropic YFV (approximately 100 LD50). Three weeks later, the boosted animals were bled and then challenged with the French neurotropic strain of YFV. Following challenge, mice were observed daily for 3 weeks(Pincus et al., 1992).
• Efficacy: Mice immunized once or twice with VP869 or YFV-17D were protected from French neurotropic virus challenge. Levels of protection achieved by immunization with VP869 were equivalent to those achieved by immunization with YFV-17D (Pincus et al., 1992).

Mouse Response

• Vaccination Protocol: Ifnar−/− mice were vaccinated intraperitoneally (i.p.) with a single 400 PFU dose of either YF-S0 or YF17D as positive control. Sham groups received a same volume of MEM containing 2% FBS (referred to as medium). (Ma et al., 2022)
• Immune Response: Single YF-S0 vaccination elicited approximately equivalent levels of YFV-specific nAbs (log10-transformed geometric mean titres, log10 GMT 3.7, 95% CI 3.5–3.9) and total IgG (log10 GMT of 5.2, 95% CI 4.8–5.5) as YF17D vaccination (log10 GMT 3.8, 95% CI 3.5–4.1 for nAbs; log10 GMT 5.4, 95% CI 5.1–5.7 for IgG). Moreover, high levels of spike-specific nAbs (log10 GMT 2.3, 95% CI 1.8–2.8) and IgG (log10 GMT 3.3, 95% CI 3.1–3.5) were conjointly induced after a single low YF-S0 dose in mice. (Ma et al., 2022)
• Challenge Protocol: Four weeks post-vaccination, mice were deeply anesthetized by intraperitoneal injection of a mixture of xylazine (16 mg kg−1, XYL-M, V.M.D.), ketamine (40 mg kg−1, Nimatek, EuroVet) and atropine (0.2 mg kg−1, Sterop), and then intracranially injected with 30μl containing 3 × 10^3 PFU YF17D. (Ma et al., 2022)
• Efficacy: All sham-immunized mice experienced acute weight loss and progressed rapidly to severe neurological disease with ruffled fur, hunched posture and hind limb paralysis, uniformly reaching human endpoint as early as five days post infection (dpi), whereas full protection was conferred in mice vaccinated with either YF-S0 or YF17D, as confirmed by the absence of any signs of disease, rapid recovery and weight gain. Data indicate that single YF-S0 vaccination provides full protection against YF17D i.c. challenge as well as YFV-induced inflammatory damage to the liver and other relevant target organs in mice, comparable to original YF17D. (Ma et al., 2022)

Hamster Response

• Vaccination Protocol: Hamsters were vaccinated i.p. with 10^4 PFU of either YF-S0 or YF17D as positive control at day 0, while sham groups received same volume of medium. (Ma et al., 2022)
• Immune Response: Single dose of YF-S0 induced consistently high levels of YFV-specific nAbs (log10 GMT 2.9, 95% CI 1.9–3.9) and IgG (log10 GMT 3.8, 95% CI 2.6–4.9) in 8 out of 9 vaccinated hamsters (primary vaccine failure in 1/9); comparable to original YF17D regarding IgG and somewhat lower for nAbs (YF17D: log10 GMT 4.2, 95% CI 4.0–4.4 and log10 GMT 4.0, 95% CI 3.8–4.1, respectively). (Ma et al., 2022)
• Challenge Protocol: Three weeks post-vaccination, animals were bled and challenged i.p. with 10^5 PFU of hamster-adapted YFV Asibi virus, a dose that has previously been shown to be 100% lethal in 3-weeks old hamsters. (Ma et al., 2022)
• Efficacy: After challenge, hamsters vaccinated with either YF17D or YF-S0 remained healthy, while sham-immunized animals suffered from clear signs of severe YFV-induced disease such as desiccation, lethargy, growth retardation and weight loss, and had to be euthanized as early as 5 dpi. Results indicate that single-dose YF-S0 vaccination provides full protection against YFV challenge and virus-induced viscerotropic disease in hamsters, comparable to original YF17D. (Ma et al., 2022)