A genomic fragment of hepatitis B virus encoding the surface antigen (HBsAg) was inserted into the proviral genome of Moloney mouse sarcoma virus (MSV), obtained from the mouse cell line G8 ‐124. The recombinant DNA was introduced into NIH 3T3 mouse fibroblasts. Cells, morphologically transformed by the oncogene of MSV (v‐mosM) were selected, established as cell lines and tested for expression of HBsAg. An expression level of up to 4.5 micrograms/10(7) cells/day was detected.

We have constructed a recombinant pBR322 plasmid composed of a subgenomic transforming fragment of bovine papillomavirus DNA and the hepatitis B surface antigen gene from cloned hepatitis B virus DNA and used it for transfection of NIH 3T3 mouse fibroblasts. The transformed cells retain the plasmids in extrachromosomal form with a copy number of about 50 to 100 per cell. Expression of the hepatitis B surface antigen gene linked to bovine papillomavirus DNA is independent of its orientation relative to the bovine papillomavirus vector. Cell lines continuously secreting high amounts of hepatitis B surface antigen into the medium could be established. The antigen is released into the culture medium as 22-nm particles, having the same physical properties and constituent polypeptides as those found in the serum of hepatitis B virusinfected patients.

Hepatitis B virus (HBV) DNA was isolated from the recombinant plasmid pAO1-HBV and recircularzed. hnmediately after introduction of this DNA into mouse fibroblasts (NIH 3T3) we observed increasing release of hepatitis B surface antigen (HBsAg) into the culture medium. Later production of HBsAg declined to a lower but constant level. No dominant selective marker and foreign promoter were necessary in this system, which therefore can be used for the study of regulation of HBsAg expression.

We have constructed a recombinant pBR322 plasmid composed of a subgenomic transforming fragment of bovine papillomavirus DNA and the hepatitis B surface antigen gene from cloned hepatitis B virus DNA and used it for transfection of NIH 3T3 mouse fibroblasts. The transformed cells retain the plasmids in extrachromosomal form with a copy number of about 50 to 100 per cell. Expression of the hepatitis B surface antigen gene linked to bovine papillomavirus DNA is independent of its orientation relative to the bovine papillomavirus vector. Cell lines continuously secreting high amounts of hepatitis B surface antigen into the medium could be established. The antigen is released into the culture medium as 22-nm particles, having the same physical properties and constituent polypeptides as those found in the serum of hepatitis B virus-infected patients.

Summary A genomic fragment encoding the surface antigen of the Hepatitis B virus (HBsAg) was flanked by long terminal repeats (LTR) of the Moloney mouse sarcome virus and entrapped within REV‐liposomes. The DNA‐containing liposomes were injected into the blastocoele of preimplantation mouse embryos which were transfered to recipients immediately after micromanipulation. From 80 injected blastocysts 24 animals were born, 5 of which were transgenic. Both the antigen and antibodies were found in the blood serum of these animals. HBsAg‐specific RNA was detected in immunopoietic organs only. Zusammenfassung Gewebespezifische Expression des Hepatitis B Oberflächen‐Antigens in Mäusen nach Gentransfer in Blastozysten mittels Liposomen Das genomische Fragment des Oberflächen‐Antigens des Hepatitis B Virus wurde mit long terminal repeats (LTR) des Moloney Maus Sarkoma Virus versehen und in Liposomen eingehüllt. Die DNA‐enthaltenden Liposomen wurden in das Blastocoel von Mäuseembryonen injiziert. Anschließend wurden die Blastozysten in Empfängertiere transferiert. Von 80 injizierten Embryonen wurden 24 Tiere geboren, von denen 5 transgenisch waren. Sowohl HBs Antigene als auch Antikörper konnten im Serum nachgewiesen werden. HBsAg‐spezifische RNA wurde nur in immunopoietischen Organen exprimiert. Résumé Expression spécifique tissulaire de l'antigène de surface de l'hépatite B chez des souris après un transfert de gène dans des blastocytes au moyen de liposomes Le fragment de génome de l'antigène de surface du virus de l'hépatite B a été juxtaposé par de «long terminal repeats» (LTR) du virus du sarcome de Moloney de la souris et enveloppé dans des liposomes. Les liposomes contenant l'ADN ont été injectés dans la blastocèle des embryons de souris. Les blastocytes furent finalement transférés chez des animaux réceptifs. 24 animaux sur 80 embryons injectés sont nés, dont 5 étaient transgéniques. Aussi bien des antigènes HBs que des anticorps ont pu être mis en évidence dans le sérum. HBsAg‐spécifique ARN fut exprimé seulement dans des organes immunopoiétiques. Resumen La expresión hística específica del antígeno superficial hepatitis B en ratones tras traslado génico en blastoquistes mediante liposomas El fragmento genómico del antígeno superficial del virus hepatitis B fue provisto con repeticiones terminales largas (RTL) del virus sarcoma murino Moloney y fue envuelto dentro de liposomas REV. Los liposomas que contenían ADN fueron inyectados en el blastocele de embriones murinos preimplantados. Los blastoquistes se transfirieron a animales recipientes inmediatamente después de efectuada la micromanipulación. De 80 blastoquistes inyectados nacieron 24 animales, 5 de los cuales eran transgénicos. En el suero sanguíneo se hallaron tanto antígenos como anticuerpos HB. ARN específico de AgHB fue detectado solo en los órganos inmunopoyéticos.