Fig. 5: Protection against SARS-CoV-2 variants of concern in pCTV-WS immunized K18-hACE2 mice.

a PRNT50 was evaluated using different SARS-CoV-2: Wuhan strain (B lineage), Delta, Gamma and Omicron variants in sera samples from pCTVØ (black circles) or pCTV-WS immunized K18-hACE2 mice (colored circles) [n = 4, pCTVØ and n = 4–8, pCTV-WS]. Body weight b and survival c of pCTVØ (black lines) or pCTV-WS immunized K18-hACE2 mice challenged with Delta (green lines). Viable viral load d, and SARS-CoV-2 RNA copy number e at 5DPI in pCTVØ (black circles) and pCTV-WS immunized mice challenged with Delta variant (green circles). [n = 4–6, pCTVØ and n = 4–8 pCTV-WS]. Body weight f and survival g of pCTVØ (black lines) or pCTV-WS immunized K18-hACE2 mice challenged with Gamma variant (blue lines). Viable viral load h and SARS-CoV-2 RNA copy number i at 5DPI in pCTVØ (black circles) and pCTV-WS immunized mice challenged with Gamma variant (blue circles). [n = 4–6, pCTVØ and n = 4–8 pCTV-WS]. Body weight j and survival k of pCTVØ (black lines) or pCTV-WS immunized K18-hACE2 mice challenged with Omicron variant (pink lines). Viral load in nasal wash l and lung m of pCTVØ (black bar) or pCTV-WS (pink bar) immunized K18-hACE2 mice and challenged with Omicron variant at 3 DPI [n = 4 mice/group]. SARS-CoV-2 RNA copy number in nasal wash n and lung o of pCTVØ (black circles) or pCTV-WS (pink circles) immunized K18-hACE2 mice and challenged with Omicron variant at 3 and 6 DPI [n = 4–6mice/group]. Histopathological sections of lungs from pCTVØ p or pCTV-WS q immunized K18-hACE2 mice and challenged with Omicron variant at 6 DPI. Inflammatory infiltrate (black arrow), perivascular inflammatory infiltrate (red arrow), vascular congestion (blue arrow), edema (arrow head) and hemorrhage (green arrow) at 1.1×, 10×, and 20× magnification. Data pooled from one or two independent experiments. The statistical analysis of weight curves was performed by area under curve followed by unpaired t-test or Mann-Whitney U test, according to the data distribution. The statistical analysis of survival was performed using the log-rank test. The statistical analysis of viral load and RNA copy number was performed using unpaired t-test or Mann-Whitney U test, according to data distribution. *p < 0.05; **p < 0.01; ***p < 0.001.