Fig. 1: Immunization schedule of ChulaCov19 in BALB/c mice.
a Experiment 1: mice were immunized twice intramuscularly (IM) with a 3-week interval with various dosages of ChulaCov19 at 0.2, 1, 10 and 30 µg. Experiment 2: heterologous prime-boost study, mice were primed with 1/10 of the approved human dosage of CoronaVac or AZD1222 and boosted 4 weeks later with 5 µg of ChulaCov19. Homologous prime/boost of each vaccine (CoronaVac, AZD1222, or ChulaCov19) were included as control groups. Experiment 3: antibody durability and effect of 3rd dose of ChulaCov19 study, mice were immunized twice with 3 weeks interval with 5 µg of ChulaCov19 (1/10 of human dose used in clinical trial) then boosted again at week 20. Bleeding was performed at 2 weeks following each dose (and at week 18 for Experiment 3). Splenocytes were collected at 2 weeks after the second dose (Experiment 1 & 2). n = 5 per group for Experiment 1, 2 and 3. b Challenge study in K18-hACE2 transgenic mice, n = 6 in vaccinated groups and n = 5 in control (PBS-receiving) group. Animals were immunized IM with 1 µg or 10 µg of ChulaCov19 at weeks 0 and 3. Sera were collected at weeks 0, 2, 3, 4 + 6 days, and 5 + 6 days for NAb measurements. At week 5, mice were challenged intranasally with 2×104 pfu of WT SARS-CoV-2. Tissues were collected at week 5 + 6 days for assessment of viral RNA. Figures were created with BioRender.com.
