LNP-IL-21 treatment successfully indued potent anti-HBV immune
responses
LNP-IL-21 induced HBV clearance in both BPS and rcccDNA persistence
mouse models was associated with HBsAb seroconversion (Figure 2B
and 4B ), suggesting LNP-IL-21 treatment is probably able to activate
HBsAg-specific humoral immune responses. To prove it, at 8 w.p.i., PBMC
were collected from LNP-IL-21-cured BPS mice achieving HBsAb
seroconversion (n = 6) and LNP-injected mice (5 out 6 mice
positive for HBsAg), and subjected to flow cytometry analysis for
HBsAg-specific B cells (Figure 6 A, C-D ). The percentages of
HBsAg-specific B cells in LNP-IL-21-cured mice were significantly higher
than those in LNP-injected mice (Figure 6 E ), and
representative images of two mice in each group were presented inFigure 6F .
On the other hand, ALT transient elevations were observed in above two
mouse models post LNP-IL-21 injection (Figure 2E and 4E ),
indicating acute liver injury. In order to investigate whether LNP-IL-21
treatment participated in activation of cellular immune responses, which
is responsible for the removal of HBV-harboring hepatocytes to achieve
cure, mouse liver tissues were collected form LNP-IL-21-and LNP-injected
mice at 2 and 8 w.p.i., and then subjected to H&E and anti-CD8 staining
(Figure 6 A, ). As shown in Figure 6B , marked
intrahepatic immune cell infiltration, including CD8+cell infiltration, was observed in LNP-IL-21-injected mice at 2 w.p.i.,
but not at 8 w.p.i., which roughly coincided with HBV clearance. No
obvious immune infiltration was observed in LNP-injected mice at 2 or 8
w.p.i.. What’s more, at 8 w.p.i., splenocytes from LNP-IL-21-cured mice,
but not LNP-injected mice, secreted much more IFN-γ post HBcAg or HBsAg
stimulation (Figure 6G ), indicating activated T cell immune
responses. In a summary, LNP-IL-21-based gene therapy successfully
induced both potent anti-viral humoral and cellular immune responses
contributing to HBV clearance.