Administration of a second booster dose further enhances
antibody response and neutralization capacity of
mCuMVTT-RBM
In a next step, we compared the efficacy of vaccinating mice with a
total of 2 doses of mCuMVTT-RBM (Prime/Boost) versus 3
doses (Prime/Boost/Boost) as illustrated in Figure 6A.
The results showed no significant difference in the induced RBD-specific
antibody titers following the 2nd dose in comparison
to sera following the 3rd dose (Fig. 6B and C).
Furthermore, the avidity of the induced antibodies induced after the
3rd dose did not show a higher value when compared to
the ones induced following the 2nd dose (Fig. 6D and
E).
To test the capacity of the induced antibodies to neutralize the real
virus, we have performed cytopathic effect (CPE) using 100
TCID50 of SARS-CoV-2/ABS/NL20. Titers are expressed as
the highest dilution that inhibits formation of CPE 100%. In contrast
to ELISA titers, a significant difference in neutralization capacity was
seen when comparing day 42 sera of vaccinated mice vs the control group
(p = 0.0014). However, sera from mice after the
3rd dose of the vaccine (day 63) showed further
enhanced neutralization titer when compared to the control group
(p . <0.00001) or the group received only the
2nd dose (p . 0.0021) (Fig. 6F). The obtained
results show the capacity of the vaccine candidate to completely block
the cytopathic effect of the virus.