Secreted hepatitis B surface antigen polypeptides are derived from a transmembrane precursor.

Simon, Kay; Lingappa, Vishwanath R.; Ganem, Don

doi:10.1083/jcb.107.6.2163

Cited by 94 publications

(91 citation statements)

References 22 publications

(38 reference statements)

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“…Whereas the presence of HBsAg on the plasma membrane provides a target for the immune response, it also provides a target for siRNA therapeutics against HBV. [31][32][33][34][35] siRNA or siRNA-producing plasmids must enter the cytoplasm to initiate RNA interference cascades, so it is important to assess whether the antibodies being used for targeting can be efficiently internalized into antigen-positive cells. 36 In the current study, the scFv we used to target siRNA delivery can be effectively internalized into HBsAg-positive cells.…”

Section: Discussionmentioning

confidence: 99%

Targeted inhibition of HBV gene expression by single-chain antibody mediated small interfering RNA delivery

et al. 2007

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RNA interference is highly effective at inhibiting HBV gene expression and replication. However, before small interfering RNA (siRNA) can be used in the clinic, it is essential to develop a system to target their delivery. Antibody-mediated delivery is a novel approach for targeting siRNA to appropriate cells. In this report, we asked whether this siRNA delivery strategy would be effective against HBV. Of 5 candidates, a specific siRNA that effectively inhibited HBV gene expression and replication was determined. Two fusion proteins, s-tP and sC-tP, were constructed to contain a single chain of the human variable fragment, scFv, against hepatitis B surface antigen (HBsAg), a truncated protamine (tP), and in the case of sC-tP, a constant region of the chain (C). S-tP and sC-tP were developed to provide targeted delivery of the siRNA, siRNA expressing cassettes (SEC), and siRNA-producing plasmids. Fluorescein isothiocyanate-siRNA, fluorescein isothiocyanate-SEC, and plasmid DNA were specifically delivered into HBsAg-positive cells using the sC-tP fusion protein, and effectively inhibited HBV gene expression and replication. HBV gene expression was also inhibited by siRNA or siRNA-producing plasmids in HBV transgenic mice. Conclusion: Our results describe a potential method for the targeted delivery of siRNA or siRNAproducing plasmids against HBV, using anti-HBsAg fusion proteins. (HEPATOLOGY 2007;46: 84-94.) R ibonucleic acid interference is a naturally occurring mechanism for silencing homologous genes. 1,2 Synthetic and plasmid-based siRNA expression systems are both effective at suppressing HBV infection, in vitro and in vivo, [3][4][5][6][7][8][9] providing the basis for a new therapeutic strategy against HBV. However, the absence of a suitable delivery system presents a major obstacle against their clinical use. [10][11][12] Targeted delivery of small interfering RNA (siRNA) to relevant cell populations should increase the therapeutic index and minimize potential side effects and cellular toxicity.Antibody-mediated delivery is an effective method of targeting siRNA to particular cells. This involves fusing the nucleic acid-binding domain to a Fab fragment or scFv that recognizes a membrane receptor, resulting in a fusion protein that possesses cell recognition and nucleic acid-binding abilities. The fusion protein can then bind nucleic acids and deliver them into target cells through receptor-mediated endocytosis. This antibody-mediated uptake has been successfully used to deliver plasmid DNA and antisense oligonucleotides. [13][14][15][16][17] Song et al. 18 demonstrated that siRNA targeted delivered to human immunodeficiency virus-infected cells and HER2 positive cells by this strategy executed gene silencing. However, whether this promising strategy for siRNA delivery is applicable to other diseases remains unknown. 19 In this report, we provide evidence that antibody-mediated siRNA delivery is effectively targeted to HBV-infected cells.In a previous study, we have obtained 5 human antihepatitis B sur...

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Section: Discussionmentioning

confidence: 99%

Targeted inhibition of HBV gene expression by single-chain antibody mediated small interfering RNA delivery

et al. 2007

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“…The small (S) protein (226 amino acids) is expressed at the highest levels, predominates in both virions and subviral particles and is secreted without cleavage of amino acid residues during translocation because of its self-assembling capacity with host-derived lipids in the cell ER (10). The middle (M) protein (containing 55 extra residues of the pre-S2 domain) is regulated by the same promoter and is similarly secreted, while the transcription of the large protein (L) is regulated by a specific but weaker promoter (pre-S1) (11).…”

Section: Hbsag: Virologymentioning

confidence: 99%

Quantification of hepatitis B surface antigen: a new concept for the management of chronic hepatitis B

Moucari

Marcellin

2011

Liver International

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HBsAg is a very important clinical test that might not only indicate active hepatitis B virus (HBV) infection but might also be used to predict clinical and treatment outcome. Clearance of HBsAg in patients with chronic HBV infection is associated with a much better clinical outcome, although surveillance for early detection of hepatocellular carcinoma (HCC) should continue. HBV DNA quantification is currently used for selecting candidates for therapy, monitoring response to therapy and detecting the emergence of drug resistance. Assays for HBsAg quantification are less expensive than HBV DNA and fully automated with a high throughput capacity. HBsAg titering may be a useful tool to manage patients with chronic HBV, to more clearly define which patients may, and more importantly, may not, benefit from treatment. Baseline and on-treatment HBsAg quantification may help to refine future treatment algorithms for both immune-modulator therapy and nucleos(t)ide analogues. Both HBV markers provide complementary information on the status of HBV infection. However, the relevance of serum HBsAg levels and its use as a reliable replacement for both covalently closed circular DNA and HBV DNA remain unclear.

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“…According to an accepted view, HBsAg secretion is a multistep event in which HBV surface polypeptides fold across the ER bilayer in a polytopic orientation and oligomerize excluding host proteins. They subsequently undergo budding, and travel as soluble lipoprotein particles inside transport vesicles (Eble et al, 1986(Eble et al, , 1987Patzer et al, 1986;Simon et al, 1988;Bruss & Ganem, 1991a;Huovila et al, 1992). Whereas in HBV virions and HBsAg tubules the L protein is well represented (up to 20 %), it is much less abundant in HBsAg spherical particles.…”

Section: Intracellular Retention Of Hepatitis B Virus Surface Proteinmentioning

confidence: 99%

Intracellular retention of hepatitis B virus surface protein mutants devoid of amino-terminal pre-S1 sequences

Gallina

Koning²,

Rossi³

et al. 1994

Journal of General Virology

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To study the mechanism of L protein-mediated, intracellular (pre-Golgi) retention of hepatitis B virus (HBV) surface proteins, a collection of HBV preS-S open reading frame variants bearing wild-type or modified preS extensions was expressed in human cells. When the secretion phenotype of the corresponding proteins was analysed, all surface proteins with rearranged preS domains were found to be at least partially retained. This held true, in particular, for two variant proteins lacking preS1 amino acids 1 to 19 (ayw), the preS1 myristylated N terminus and a putative retention domain, and for another variant lacking the entire preS1 domain plus the N-terminal portion (amino acids 1 to 12) of the preS2 domain. All the retained variants underwent intracellular dimerization/oligomerization via disulphide bonds to a degree comparable to that observed in well exported natural proteins. Our results show that retention can take place in the absence of L Nterminal sequences and does not imply inhibition of covalent oligomerization.

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Secreted hepatitis B surface antigen polypeptides are derived from a transmembrane precursor.

Cited by 94 publications

References 22 publications

Targeted inhibition of HBV gene expression by single-chain antibody mediated small interfering RNA delivery

Targeted inhibition of HBV gene expression by single-chain antibody mediated small interfering RNA delivery

Quantification of hepatitis B surface antigen: a new concept for the management of chronic hepatitis B

Intracellular retention of hepatitis B virus surface protein mutants devoid of amino-terminal pre-S1 sequences

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