siR-7-EM / peptide dendrimer KK-46 complexes exhibit
strong anti-SARS-CoV-2 activity in vitro
To examine whether the LNA-modification may influence the knockout
activity and to evaluate KK-46 transfection activity with siRNA Vero E6
cells were transfected with unmodified siR-7 or LNA- modified siR-7-EM/
KK-46 complexes and infected with SARS-CoV-2. Viral load in cells lysate
and supernatants was determined by qRT-PCR 48h after infection. Three
increasing concentrations of complex 21, 42 and 84 μg/per well which
included sum of siRNA/siLNA+KK-46, μg: 1+20, 2+40 and 4+80 were used,
respectively. As shown in Figure 4, up to a two-log reduction in vRNA
levels in cell lysates (Fig.4a; P<0.01) and supernatants (Fig.
4b; P<0.01, P<0.05), were achieved after 48h using
either 42 or 84 μg of both siR-7 and siR-7-EM /KK-46 complexes.
Complexes containing unspecified siLuc (targeting gene of firefly
luciferase) with SARS-CoV-2 infected cells were used as negative control
showing no significant reduction of vRNA levels as compared to
SARS-CoV-2-infected cells (Fig. 4). Significant reduction of vRNA in
both cell lysate and supernatants compared to unspecific siLuc and
infectious control was observed at a dose of 42 μg (P<0.01,
P<0.05). The target-specificity of the siR-7 or siR-7-EM
/KK-46 complexes was reflected by the use of a untargeted siLuc control,
which showed no significant off-target effects on the vRNA levels
neither in cell lysates nor in supernatants. We found no significant
difference in antiviral effects of unmodified siR-7 or LNA- modified
siR-7-EM but complexes with siR-7-EM seemed to be more effective than
siR-7 complexes which was also reflected by the fact that only the 21 µg
dose of siR-7-EM gave significant results compared to siLuc,
P<0.05.