Figure 1.

SAM vaccine-induced alphavirus superinfection exclusion

(A) Schematic of experimental set-up; Vero cells were transduced with SAM (10 VRPs/cell) and infected with WT alphaviruses (10 TCID₅₀/cell), either at the same time or with a 1 h delay between SAM and WT alphavirus. Supernatant fractions were collected and titrated to quantify (B) the WT alphavirus progeny and (D) the level of SAM vaccine packaged in WT alphavirus particles. (B) WT alphavirus growth kinetics quantified as packaged WT alphavirus genomes (n = 2, detection limit 3 log₁₀TCID₅₀/mL). (C) Fluorescence microscopy of co-transduced/infected Vero cell; cell nuclei stained with Hoechst, WT alphavirus (CHIKV) stained with rabbit anti-CHIKV E2 antibody, and SAM vaccine mCherry expression (recolored green). Co-expression of SAM and WT alphavirus in the same cell is indicated in the enlargement using arrowheads. (D) Titer of SAM packaged in WT alphavirus particles based on SAM-encoded mCherry expression in serial dilutions of supernatant samples (n = 2, detection limit 3 log₁₀VRP/mL).