B6;SJL-Tg(Mt1-HBV)28Bri/ChiJ

Stock number: 027527
Product name: MT-PSX transgenic line 23-3
Research areas: Cancer Research, Immunology, Inflammation and Autoimmunity Research, Internal/Organ Research, Research Tools, Virology Research

Description

MT-PSX transgenic line 23-3 mice (also called Tg[MT-1,HBV]Bri28) have the zinc-inducible mouse metallothionein I promoter sequences directing expression of the envelope/surface antigen coding region (HBsAg) of the hepatitis B virus (HBV). This results in high serum HBsAg before zinc treatment, and hepatocellular retention of HBsAg following zinc treatment. These mice are a model for studying the impact of secreted HBsAg on induction of HBsAg-specific adaptive immune responses during infection or to therapeutic vaccination. They are also useful in studying the immunopathogenesis of acute T cell mediated hepatitis, chronic T cell mediated hepatitis, and the downstream consequences of chronic hepatitis, especially hepatocellular carcinoma.

Detailed description

MT-PSX transgenic line 23-3 mice (also called Tg[MT-1,HBV]Bri28) have zinc-inducible expression of nontoxic quantities of the three hepatitis B virus envelope/surface antigen proteins (large, middle, and small; all containing hepatitis B surface antigen (HBsAg) determinants) in their hepatocytes, and are immunologically tolerant to HBsAg at the T cell level. Independent of zinc activation, these mice display no evidence of spontaneous liver disease nor hepatocellular carcinoma during their lifetime.
During the normal HBV replication cycle, the middle and small envelope proteins assemble to form the HBV major envelope polypeptide (a 22 nm spherical subviral particle containing HBsAg) that is rapidly-secreted secreted by the hepatocyte into the circulation. However, the ability of the hepatocytes to secrete these HBsAg subviral particles is inversely proportional to the abundance of the large envelope protein which, when coexpressed with the middle and small envelope proteins, forms long non-secretable filamentous particles that accumulate in the endoplasmic reticulum (where they are readily detectable immunohistochemically), thus precluding secretion of the 22 nm spherical forms.
The MT-PSX transgene is designed to have the zinc-inducible mouse metallothionein I promoter sequences directing expression of the HBV large envelope protein, but expression of the middle and small envelope proteins are regulated by a constitutively active internal promoter located within the envelope coding region on the transgene. Therefore, in the absence of dietary zinc supplementation, expression of the middle and small envelope proteins, but not the large envelope protein, is observed; this results in high serum HBsAg levels and very low hepatocellular HBsAg levels (barely detectable immunohistochemically).
Activation of the metallothionein I promoter by oral zinc administration leads to expression of the large envelope polypeptide by the hepatocyte; this results in the formation and retention of the non-secretable filamentous HBsAg particle in the hepatocyte endoplasmic reticulum (where it is detectable principally as cytoplasmic HBsAg in periportal hepatocytes close to the point of entry of the circulation into the hepatic lobule) and gives the hepatocytes a "ground glass" appearance. This renders the hepatocytes highly susceptible to destruction (MHC class I-restricted necro-inflammatory liver disease) after immune system ablation with subsequent adoptive transfer of HBsAg-specific cytotoxic T lymphocytes (CTLs).
MT-PSX transgenic line 23-3 mice exhibit no detectable liver expression (RNA or protein) from the transgenic HBV X gene.
Hemizygous mice are viable, fertile and healthy. To date (July 2015), it has not been attempted to make this strain homozygous.

Importantly, the donating investigator confirms that the MT-PSX transgenic line 23-3 mice do not produce the infectious HBV particle (hepatitis B virion aka Dane particle), independent of zinc administration. This is because the MT-PSX transgene does not have the sequences encoding the viral DNA polymerase (P gene) or the HBV core protein (pre-C [HBeAg] and C gene [HBcAg]).

Development

The MT-PSX transgene was designed by Dr. Francis V. Chisari (The Scripps Research Institute) in collaboration with Dr. Ralph L. Brinster (University of Pennsylvania) and Dr. Richard D. Palmiter (University of Washington). This MT-PSX transgene has the zinc-inducible mouse metallothionein I promoter sequences upstream of the hepatitis B virus HBsAg coding region (PSX). Specific details are further below.
The mouse metallothionein I promoter sequences were 1.1 kbp. The 3.5 kbp transgene was microinjected into the male pronucleus of fertilized one-cell ova of C57BL/6 x SJL hybrids. Founder males were bred to C57BL/6J females for germline transmission; producing six MT-PSX lineages. The donating investigator reports that mice from lineage 23-3 were backcrossed to C57BL/6J animals for 1-2 generations. These MT-PSX transgenic line 23-3 mice (also called Tg[MT-1,HBV]Bri28) were sent to The Jackson Laboratory Repository in 2015. Upon arrival, males were used to cryopreserve sperm. To establish the living mouse colony, an aliquot of the frozen sperm is used to fertilize oocytes from C57BL/6J inbred mice (Stock No. 000664).

In 2015, the first generation rederived mice at The Jackson Laboratory were all found to have C57BL/6 allele-type for specific markers (H-2K^b, H-2D^b CD45.2 and Thy1.2).

The HBsAg coding region (PSX) is the 2.3 kbp BglII A fragment from the hepatitis B virus (HBV; subtype ayw) genome spanning nucleotides 2839 and 1986 (from GenBank V01460.1). This region contained the entire HBV envelope/surface antigen (HBsAg) open reading frame (pre-S1, pre-S1 and S), the region between the S and X genes, and the X gene.
The HBsAg coding region consists of three translation initiation codons at nucleotides 2850, 3174, and 157 (which represent, respectively, the N termini of the large, middle, and major envelope polypeptides), and a stop codon at nucleotide 835. Additionally, transcriptional start sites in the vicinity of nucleotide 1/3182 and mRNA polyadenylation recognition sequence starting at nucleotide 1918 define the approximate termini of the HBV transcript which encodes the major envelope polypeptide.
The MT-PSX transgene is constructed such that the HBV large envelope protein can be produced only from a larger transcript emanating from the transcription start sites defined by the mouse metallothionein I promoter, but the middle and small envelope proteins are regulated by a constitutively active internal promoter located within the envelope coding region.

Allele

Symbol: Tg(Mt1-HBV)28Bri
Name: transgene insertion 28, Ralph L Brinster
MGI accession ID: MGI:5648219
Generation method: Transgenic
Attributes: Inserted expressed sequence
Synonyms: MT-PSX; Tg[MT-1,HBV]Bri28; TM 23-3
Marker symbol: Tg(Mt1-HBV)28Bri
Marker name: transgene insertion 28, Ralph L Brinster
Chromosome: UN
Strain of origin: C57BL/6 x SJL
Expressed genes: HBV,hepatitis B virus large envelope polypeptide,
Molecular note: The transgene contains the zinc-inducible mouse metallothionein I promoter sequences upstream of the hepatitis B virus HBsAg coding region. The HBsAg coding region is the 2.3 kbp BglII A fragment from the hepatitis B virus genome spanning nucleotides 2839 and 1986 (from GenBank V01460.1). This region contains the entire HBV envelope/surface antigen (HBsAg) open reading frame (pre-S1, pre-S1 and S), the region between the S and X genes, and the X gene. The HBV large envelope protein is produced only from a larger transcript emanating from the transcription start sites defined by the mouse metallothionein I promoter, but the middle and small envelope proteins are regulated by a constitutively active internal promoter located within the envelope coding region.