Fig 6. scMAYV-E protects immunized mice from MAYV challenge.

IFNAR^-/- mice aged 4–6 weeks old were immunized twice, two weeks apart with pVax1 or scMAYV-E using EP-enhanced i.m. injection. Groups of mice for immunogenicity studies were euthanized one week after the final immunization. (A) Evaluation of cellular responses in vaccinated IFNAR^-/- mice. IFN-γ ELISpot of pVax1 or scMAYV-E immunized splenocytes is shown (n = 4). (B) Evaluation of humoral responses in vaccinated IFNAR^-/- mice one week after the second immunization prior to viral challenge. Endpoint titers for rE1-IgG and rE2-IgG were evaluated for pVax1 or scMAYV-E immune sera (n = 4). Mice were challenged intraperitoneally (i.p.) one week after the second immunization (day 21) with 10² PFU of MAYV TRVL 15537. All mice were observed daily for clinical signs of disease up to 8 days post challenge. (C) Percent change in bodyweight from day 0 in individual immunized mice post challenge (n = 10); p = 0.0115 and (D) a Kaplan-Meier survival curve of scMAYV-E or pVax1 immunized mice post-MAYV challenge (n = 10; survival (%): scMAYV-E = 100, pVax1 = 0). (E) Representative pictures of rear footpad of uninfected mouse (naive), pVax1 immunized mouse (Infected/pVax1), and scMAYV-E immunized mouse (Infected/scMAYV-E) at 6 days post challenge. (F) Quantification of rear footpad size as measured by a caliper on day 6 post-MAYV challenge (n = 6 pVax1; n = 8 scMAYV-E). (G) MAYV PFU/ml in sera collected from pVax1 and scMAYV-E immunized mice at day 6 post MAYV challenge (n = 8).