FIG 3.

Vaccination with VSV-cHAs is superior to VSV-HAs at generating broadly reactive and stalk-specific serum HA antibodies. (A) Schematic of VSV-cHA versus VSV-HA prime-boost-boost experiment. Vaccinations were performed with 2 × 10⁶ PFU in each case. (B) Groups of BALB/c mice were primed (i.m.) and boosted (combined i.m. and i.n.) after 3 weeks, and again after another 3 weeks, with either VSV-cHAs or VSV-HAs. Serum was collected prior to each boost and 1 month after the final boost and then subjected to ELISA against a panel of HA substrates. Blue bars represent the reciprocal endpoint ELISA titer of pooled postprime serums, and red bars represent the total reciprocal endpoint ELISA titer after prime two boosting vaccinations. Both VSV-cHA and VSV-HA vaccination results in stalk-specific and cross-reactive serum antibody, although VSV-cHAs generate higher titer responses and improved boosting of these responses.