[Generation of a novel HBeAg transgenic mice using CRISPR/Cas9 technique].

Objective: To generate a new strain of HBeAg transgenic mice using CRISPR/Cas9 technique.
Methods: Hepatitis B virus (HBV) HBeAg gene was cloned and inserted in the pliver-HBeAg expression frame at the site of Rosa26 gene using CRISPR/Cas9 and homologous recombination techniques to construct the pliver-HBeAg expression vector containing HBeAg gene. The linear DNA fragment containing HBeAg gene was obtained by enzyme digestion. Cas9 mRNA, gRNA and the donor vector were microinjected into fertilized eggs of C57BL/6J mice, which were then transplanted into the uterus of C57BL/6J female surrogate mice to obtain F0 generation mice. The F0 generation mice were identified by long fragment PCR to obtain F0 transgenic mice with HBeAg gene. The positive F0 generation mice were bred with wild-type C57BL/6J mice to produce the F1 mice, which were identified by PCR and sequencing. The positive F1 transgenic mice carrying HBeAg gene were backcrossed until the homozygous offspring transgenic mice were obtained. The genotypes of the offspring mice were identified. The expressions of HBeAg and HBeAb in the heterozygous and homozygous HBeAg transgenic mice were detected by automatic chemiluminescence immunoassay, immune colloidal gold technique and immunohistochemistry method.
Results: A total of 56 F0 mice were obtained, and 2 of them carried homologous recombined HBeAg gene. Six positive F1 mice were obtained, from which 22 homozygous and 29 heterozygous F2 generation HBeAg transgenic mice were obtained. High concentration of HBeAg protein was detected in the peripheral blood of all the positive HBeAg transgenic mice without HBeAb expression. HBeAg expression was detected in the hepatocytes of HBeAg transgenic mice.
Conclusions: We obtained a new strain of HBeAg transgenic mice with stable expression of HBeAg in the hepatocytes and immune tolerance to HBeAg using CRISPR/Cas9 technique, which provide a new animal model for studying HBV.