• Vaccine Name: Y. pestis YscF subunit vaccine
• Target Pathogen: Yersinia pestis
• Target Disease: Plague
• Vaccine Ontology ID: VO_0000836
• Type: Subunit vaccine
• YscF from Y. pestis CO92 gene engineering:
  • Type: Protein
  • Description: YscF expressed and purified from E. coli was highly alpha-helical and formed relatively stable aggregates under physiological conditions.
  • Detailed Gene Information: Click Here.
• Adjuvant:
  • Adjuvant name:
  • VO adjuvant ID: VO_0000139
• Preparation: To facilitate its purification, YscF was cloned into the overexpression plasmid pET24b (Novagen) to yield a hexahistidine-tag on the C-terminus of YscF (HT-YscF). Purified HT-YscF with the adjuvant was then used for innoculation (Matson et al., 2005).
• Description: Due to the severity of plague and its potential for use as a bioweapon, better preventatives and therapeutics for plague are desirable. Subunit vaccines directed against the F1 capsular antigen and the V antigen (also known as LcrV) of Y. pestis are under development. However, these new vaccine formulations have some possible limitations: the F1 antigen is not required for full virulence of Y. pestis and LcrV has a demonstrated immunosuppressive effect. These limitations could damper the ability of F1/LcrV based vaccines to protect against F1-minus Y. pestis strains and could lead to a high rate of undesired side effects in vaccinated populations. Thus, the use of other antigens in a plague vaccine formulation may be advantageous. Desired features in vaccine candidates would be antigens that are conserved, essential for virulence and accessible to circulating antibody. Several of the proteins required for the construction or function of the type III secretion system (TTSS) complex could be ideal contenders to meet the desired features of a vaccine candidate. Accordingly, the TTSS needle complex protein, YscF, was selected to investigate its potential as a protective antigen (Matson et al., 2005).

Mouse Response

• Host Strain: 6-to 8-week-old female Swiss-Webster mice.
• Vaccination Protocol: Mice immunized 40 μg/mouse HT-YscF in PBS or PBS alone (control mice) emulsified 1:1 with CFA. Experimental mice were boosted with 40 μg/mouse HT-YscF in IFA after two weeks and with 20 μg/mouse HT-YscF in IFA at 4 weeks post-immunization. Negative control mice were boosted with PBS emulsified with IFA according to the same schedule. Two weeks following the final booster immunization, sera were collected from the HT-YscF-immunized and the PBS-immunized mice to assay for HT-YscF reactivity. Sera from 22 mice from the HT-YscF-immunized and the PBS-immunized groups were tested for total IgG reactivity (Matson et al., 2005).
• Side Effects: None noted.
• Challenge Protocol: After establishing that the HT-YscF immunized mice had developed a strong antibody response to HT-YscF, the mice were challenged with Y. pestis. Two weeks after the final immunization, groups of 10 mice were challenged i.v. via the retro-orbital sinus with 10^1 to 10^6 CFU Y. pestis KIM5 (pgm-) in PBS. The mice were observed for 19 days after challenge, and the average doses required to kill 50% of the mice (LD50) for the treatment groups were calculated.
• Efficacy: Mice immunized with HT-YscF demonstrated a strong antibody response to YscF and provided protection to the vaccinated mice from lethal Y. pestis challenge (Matson et al., 2005).