Mouse monoclonal antibodies to hepatitis B virus preS1 produced after immunization with recombinant preS1 peptide

Impact of preS1 Evaluation in the Management of Chronic Hepatitis B Virus Infection

Background and Objectives: The measurement of hepatitis B surface antigen (HBsAg) is essential for managing chronic hepatitis B virus infection (CHB). HBsAg consists of three different surface envelope proteins: large, middle, and small HB surface proteins. However, in clinical practice, it is not common to evaluate each of these HB surface proteins separately. Materials and Methods: In this study, we investigated preS1 expression using seven monoclonal antibodies (mAbs) in 68 CHB patients, as well as examining their antigenicity. Results: Although the seven mAbs had been derived from genotype (Gt) C, they could recognize preS1 with Gts A to D. The epitopes were concentrated within the aa33-47 region of preS1, and their antigenicity was significantly reduced by an aa45F substitution. We found that preS1 expression remained consistent regardless of HBsAg levels and different Gts in CHB patients, in contrast to what was observed in SHBs. Conclusions: These results suggest that the antigenic epitope is preserved among different Gts and that the expression pattern of preS1 is altered during CHB, highlighting its vital role in the HBV infection cycle. Our present results suggest preS1 is a promising therapeutic target in CHB.

Development of monoclonal antibodies to target the large surface protein of hepatitis B virus and their use in therapeutic and diagnostic applications

Over 250 million people are living with chronic infection caused by the hepatitis B virus (HBV). HBV has three surface proteins, namely small (SHBs), medium (MHBs) and large (LHBs), and they play different roles in the virus life cycle. The approved hepatitis B vaccine only contains the SHBs protein and many studies have focused on characterising the functional domains in SHBs. Although the LHBs protein is less studied, recent studies have shown that it plays important roles in mediating viral entry, replication and assembly. Over the years, there have been major advancements in monoclonal antibody (mAb) discovery tools and multiple mAbs have been developed to specifically target the preS1 domain in LHBs. We summarise the HBV infection systems and antibody discovery strategies that have been utilised by various research groups to assess the potential use of anti-preS1 mAbs as therapeutic antibodies against HBV or in the development of new diagnostic assays.

Advances in human monoclonal antibody therapy for HBV infection

HBV neutralizing antibodies target the viral envelope antigens (HBsAg) and confer long-term immune protection in vaccinees and infected humans who seroconvert. They recognize various HBsAg epitopes, and can be armed with Fc-dependent effector functions essential for eliminating infected cells and stimulating adaptive immunity. Hundreds of HBsAg-specific monoclonal antibodies (mAbs) were produced from the early 80's, but it is only recently that bona fide human anti-HBV mAbs were generated from vaccinees and seroconverters. Neutralizing HBV mAbs have in vivo prophylactic and therapeutic efficacy in animal models, and the capacity to decrease antigenemia and viremia in infected humans. Thus, polyfunctional, potent and broad human HBV neutralizing mAbs offer novel opportunities to develop effective interventions to prevent and treat HBV infection. Here, we summarize recent findings on the humoral immune response to HBV, and explore the potential of human HBV neutralizing mAbs as immunotherapeutics to help achieving a functional cure for HBV.

Construction of an anti-hepatitis B virus preS1 antibody and usefulness of preS1 measurement for chronic hepatitis B patients: Anti-HBV PreS1 antibody

OBJECTIVES

The preS1 region plays an essential role in hepatitis B virus (HBV) infection. We construct an antibody that binds to preS1 and a measurement system for serum preS1 in chronic HBV-infected patients.

METHODS

Hybridoma clones that produce anti-preS1 antibodies were obtained by the iliac lymph node method. Epitope mapping was conducted, and an enzyme-linked immunosorbent assay (ELISA)-based method was developed. Using this ELISA system, serum preS1 levels were measured in 200 chronic HBV-infected patients.

RESULTS

Eight types of hybridomas were obtained, of which antibody 3-55 using amino acids 38-47 as the epitope showed high binding affinity to preS1. Serum preS1 levels measured by ELISA using 3-55 antibody were correlated with HBsAg, HBcrAg and HBV DNA levels. Among HBeAg-negative patients without antiviral therapeutic objective (HBV DNA <3.3 log IU/mL or alanine aminotransferase ≤30 U/L), preS1 was significantly higher in subjects who had progressed to the point of requiring antiviral therapy compared to subjects who had maintained their status for the preceding three years (p<0.01).

CONCLUSIONS

We constructed an antibody against preS1 and an ELISA system capable of measuring serum preS1 levels. PreS1 may serve as a novel tool to predict the need for antiviral therapy in HBeAg-negative HBV-infected patients.

Improvement of Biophysical Properties and Affinity of a Human Anti-L1CAM Therapeutic Antibody through Antibody Engineering Based on Computational Methods

The biophysical properties of therapeutic antibodies influence their manufacturability, efficacy, and safety. To develop an anti-cancer antibody, we previously generated a human monoclonal antibody (Ab417) that specifically binds to L1 cell adhesion molecule with a high affinity, and we validated its anti-tumor activity and mechanism of action in human cholangiocarcinoma xenograft models. In the present study, we aimed to improve the biophysical properties of Ab417. We designed 20 variants of Ab417 with reduced aggregation propensity, less potential post-translational modification (PTM) motifs, and the lowest predicted immunogenicity using computational methods. Next, we constructed these variants to analyze their expression levels and antigen-binding activities. One variant (Ab612)—which contains six substitutions for reduced surface hydrophobicity, removal of PTM, and change to the germline residue—exhibited an increased expression level and antigen-binding activity compared to Ab417. In further studies, compared to Ab417, Ab612 showed improved biophysical properties, including reduced aggregation propensity, increased stability, higher purification yield, lower pI, higher affinity, and greater in vivo anti-tumor efficacy. Additionally, we generated a highly productive and stable research cell bank (RCB) and scaled up the production process to 50 L, yielding 6.6 g/L of Ab612. The RCB will be used for preclinical development of Ab612.

Recent Progress on Neutralizing Antibodies against Hepatitis B Virus and its Implications

BACKGROUND

Hepatitis B virus (HBV) infection remains a global health problem. As "cure" for chronic hepatitis B is of current priority, hepatitis B immunoglobulin (HBIG) has been utilized for several decades to provide post-exposure prophylaxis. In recent years, a number of monoclonal antibodies (mAbs) targeting HBV have been developed and demonstrated with high affinity, specificity, and neutralizing potency.

OBJECTIVE

HBV neutralizing antibodies may play a potentially significant role in the search for an HBV cure. In this review, we will summarize the recent progress in developing HBV-neutralizing antibodies, describing their characteristics and potential clinical applications.

RESULTS AND CONCLUSION

HBV neutralizing antibodies could be a promising alternative in the prevention and treatment of HBV infection. More importantly, global collaboration and coordinated approaches are thus needed to facilitate the development of novel therapies for HBV infection.

Enhanced humanization and affinity maturation of neutralizing anti-hepatitis B virus preS1 antibody based on antigen-antibody complex structure

To improve a previously constructed broadly neutralizing hepatitis B virus (HBV)-specific preS1 humanized antibody (HzKR127), we further humanized it through specificity-determining residue (SDR) grafting. Moreover, we improved affinity by mutating two residues in heavy-chain complementarity-determining regions (CDR), on the basis of the crystal structure of the antigen-antibody complex. HzKR127-3.2 exhibited 2.5-fold higher affinity and enhanced virus-neutralizing activity compared to the original KR127 antibody and showed less immunogenic potential than HzKR127. Enhanced virus-neutralizing activity was achieved by the increased association rate, providing insights into engineering potent antibody therapeutics for HBV immunoprophylaxis. HzKR127-3.2 may be a good candidate for HBV immunoprophylaxis.

A monoclonal antibody specific to the non-epitope region of hepatitis B virus preS1 contributes to more effective HBV detection

OBJECTIVES

The hepatitis B virus (HBV) preS1 protein is divided into an epitope region and a non-epitope region based on the respective antigenicities of these regions. Most of the antibodies that are currently used to detect the large surface protein of HBV (HBV LHB) are specific to the epitope region of preS1, which may contribute to the false negative results of HBV LHB detection assays. Here, we established a mouse monoclonal antibody (mAb) that could improve the efficiency of HBV LHB detection.

DESIGN AND METHODS

The HBV preS1 protein was expressed in E. coli strain BL21 and used to screen hybridoma clones. HBV preS1-specific mAb was produced by immunizing mice with a chemically synthesized peptide antigen derived from the non-epitope region of HBV preS1. The mAb was characterized by ELISA, Western blot, and immunocytochemistry and was subsequently used in serum sample tests.

RESULTS

Based on in silico B cell epitope predictions, the HBV preS1 aa 91-117 peptide was synthesized as an antigen. Recombinant HBV preS1 was expressed in E. coli and identified by SDS-PAGE. The mAb D8 (IgG2b) recognized the recombinant preS1 protein in both ELISA and Western blot assays and also recognized the preS1 protein expressed in plasmid-transfected HepG2.2.15 cells by immunocytochemistry. Furthermore, the D8 mAb, which is specific for the non-epitope region of preS1, contributed to the improved sensitivity and specificity of HBV detection.

CONCLUSIONS

We established an mAb that is specific to the non-epitope region of HBV preS1 and improved the detection of HBV LHB in an ELISA assay. This mAb could help increase the accuracy of the clinical measurement of preS1.

Detection of hepatitis B virus PreS1 antigen using a time-resolved fluoroimmunoassay

The hepatitis B virus (HBV) PreS1 antigen is expressed at the distal most region of the envelope protein and contains the hepatocyte receptor-binding site. The presence of the HBV PreS1 antigen in serum and liver of HBsAg-positive patients is a new marker used for diagnosing HBV infection, and is indicative of viral replication. Our objective is to establish a method of time-resolved fluoroimmunoassay (TRFIA) with higher sensitivity and broader detection range for detecting serum HBV PreS1 antigen. Eu(3+) labeling of antibodies was performed with respective labeling kits, and Eu(3+) fluorescence intensity was measured with an auto DELFIA1235 TRFIA analyzer. The established method was evaluated for its performance. Serum specimens (574 in total) from Wuxi People's Hospital were analyzed for PreS1 antigen using the TRFIA and ELISA. The precision, specificity, and sensitivity of the TRFIA were clearly better than ELISA. The detection limit was 0.01 ng/mL. The average recovery rate for PreS1 antigens was 103.3%. There was significant correlation between the PreS1 antigen results obtained by TRFIA and ELISA in 374 serum samples with HBV >10(3) IU/mL (χ(2) = 25.04, p < 0.01) and 183 HbeAg-positive serum samples (χ(2) = 12.07, p < 0.01). Normal reference ranges were established at 0-0.32 ng/mL based on the values obtained from 100 healthy controls. TRFIA is a significantly effective method for clinical detection of serum HBV PreS1 antigens.

A chimeric antibody to L1 cell adhesion molecule shows therapeutic effect in an intrahepatic cholangiocarcinoma model

Intrahepatic cholangiocarcinoma (ICC), a malignant tumor derived from the intrahepatic bile duct epithelium, has a poor prognosis and is refractory to conventional chemotherapy and radiation therapy. Thus, there is an urgent need to develop new effective therapeutic strategies for this disease. We previously found that L1 cell adhesion molecule (L1CAM) plays an important role in tumor progression of ICC, and we generated a murine mAb, A10-A3 (IgG1), that binds to the Ig1 domain of L1CAM. In the present study, we further characterized A10-A3, constructed a chimeric A10-A3 antibody (cA10-A3) containing the constant regions of human IgG1, and evaluated the therapeutic potential in a human ICC xenograft nude mice model. The affinities (KD) of A10-A3 and cA10-A3 for soluble L1CAM were 1.8 nM and 1.9 nM, respectively, as determined by competition ELISA. A10-A3 inhibited L1CAM homophilic binding and was slowly internalized into the tumor cells, but it did not significantly inhibit proliferation of ICC cells in vitro. cA10-A3 mediated antibody- dependent cell-mediated cytotoxicity in vitro and displayed anti-tumor activity in the ICC animal model. These results suggest that the humanized A10-A3 antibody may have potential as an anticancer agent for the treatment of ICC.

Immunocapture enzyme-linked immunosorbent assay for assessment of in vitro potency of recombinant hepatitis B vaccines

Quantification of hepatitis B surface antigen (HBsAg) or relative in vitro potency in the final vaccines is a prerequisite for hepatitis B vaccine batch release. The commercial kit for automated analysis (AxSYM) is expensive, and an alternative is required for the estimation of HBsAg in hepatitis B vaccines. Mouse monoclonal antibodies (MAbs) specific for HBsAg were developed and characterized. One of the monoclonal antibodies (HBs06) was used in development of an immunocapture ELISA (IC-ELISA) as an unlabeled capture antibody and biotin-labeled detection antibody. The IC-ELISA was standardized and validated using experimental hepatitis B vaccine batches with various HBsAg concentrations per dose and commercial vaccines. The vaccine was treated with an alkaline solubilizer to desorb the HBsAg from Algel-adjuvanted vaccines before testing, and the sensitivity of the test was 5 ng/ml. A good correlation could be observed between the HBsAg estimates derived by both formats, except for the higher HBsAg concentration range, where the IC-ELISA format could estimate closer to the actual values than AxSYM. There was a significant correlation between the estimated relative potencies of the two methods. There was lack of correlation between the in vivo potency and the relative in vitro potency. However, the estimates of IC-ELISA were comparable to the in vivo values when compared with the estimates of AxSYM. The IC-ELISA can therefore be considered to be a reliable test for deriving in vitro relative potency and antigen concentration in vaccine batches for batch control and release.

Selection of an affinity-matured antibody against a defined epitope by phage display of an immune antibody library

In a previous study, we generated a murine hepatitis B virus (HBV)-neutralizing monoclonal antibody (mAb), KR127, that binds to an epitope (amino acids 37-45, NSNNPDWDF) of the preS1 antigen. Furthermore, an epitope tag, S1 (NANNPDWDF), was developed for protein tagging. The aim of the present study was to develop a high-affinity antibody to the same preS1 epitope. Mice were immunized with the N-terminal domain of human thrombopoietin fused to the S1 tag (nTPO-S1), and a phage-displayed chimeric Fab library was constructed and screened by panning against nTPO-S1. A high-affinity antibody (3-34) was selected that binds to the preS1 antigen. The IgG molecules of 3-34 showed approximately nine-fold higher affinity (K(D) 1.2 nM) for preS1 compared with KR127 (K(D) 10.4 nM), competed with KR127 for binding to the epitope, and bound to HBV particles. This study provides a simple and efficient way to develop a high-affinity antibody to a defined epitope by phage display of an immune antibody library.

Improvement of Neutralizing Activity of Human scFv Antibodies Against Hepatitis B Virus Binding Using CDR3 VHMutant Library

CDR3 of the heavy-chain variable region of immunoglobulin is a region in which somatic mutation occurs heavily after secondary antibody response, resulting in an affinity maturation of antibodies in vivo. The aim of this study was to improve the affinity of a human single-chain variable fragment (scFv) specific for pre-S1 of hepatitis B virus (HBV) by introducing random mutagenesis in CDR3 variable region of heavy chain (V(H)) of the parental scFv clone 1E4. By using a BIAcore for panning and screening, we have selected three clones (A9, B2, and B9) with lower highest affinity (K(D)) than 1E4. Affinities of selected clones ranged from 1.7 x 10(7) mol/L to 6.3 x 10(8) mol/L, which were increased by factors of 1.4 to 4.0, respectively, compared to the parental clone. Binding inhibition assay using flow cytometry and polymerase chain reaction revealed that B2 (6.4 x 10(8) mol/L) had a higher neutralizing activity against pre-S1 or HBV virion binding to liver cell line. This anti-pre-S1 scFv can be considered as a potential therapeutic tool for a passive immunotherapy for HBV infection.

Identification of the immunogenic domains in HBsAg preS1 region using overlapping preS1 fragment fusion proteins

AIM: The incorporation of hepatitis B virus (HBV) preS1 region into epitope-based vaccines against HBV has been accepted widely, but the incorporate site and size of preS1 sequence is controversial. Therefore our purpose was to further investigate its immunogenic domains for the epitope-based hepatitis B vaccine design.

METHODS: Eight GST fusion proteins containing overlapping preS1 fragments in preS1 (21-119) region were expressed in E.coli. Using these purified fusion proteins, the immunogenic domains in preS1 region were identified in detail in mice and humans by Western blot analysis and ELISA.

RESULTS: The results in mice showed that the immu-nogenic domains mainly existed in preS1 (21-59) and preS1 (95-109). Similarly, these fragments had strong immunogenicity in humans; whereas the other parts except for preS1 (60-70) also had some immunogenicity. More importantly, a major immunogenic domain, preS1 (34-59), which has much stronger immunogenicity, was identified. Additionally, the antibodies against some preS1 fragments, especially preS1 (34-59), were speculated to be virus-neutralizing.

CONCLUSION: Eight GST fusion proteins containing overlapping preS1 fragments were prepared successfully. They were used for the study on the immunogenic dom-ains in preS1 (21-119) region. The preS1 (34-59) fragm-ents were the major immunogenic domains in the preS1 region, and the antibodies against these fragments were speculated to be virus-neutralizing. Therefore, the incorporation of preS1 (34-59) fragments into epitope-based HBV vaccines may be efficient for enhancement of immune response. Additionally, the results also imply that there are more complex immune responses to preS1 region and more abundant immunogenic domains in humans.

Expression and immunoactivity of chimeric particulate antigens of receptor binding site-core antigen of hepatitis B virus

AIM: To improve the immunogenicity of receptor binding site of hepatitis B virus (HBV) on preS1 antigen using HBV core antigen as an immuno-carrier.

METHODS: One to 6 tandem copies of HBV preS1 (21-47) fragment were inserted into HBcAg at the sites of aa 78 and 82, and expressed in E.coli. ELISA, Western blot and animal immunization were used to analyze the antigenicity and immmunogenicity of purified particulate antigens. The ability to capture HBV by antibodies elicited by chimeric particles was detected with immuno-capture PCR.

RESULTS: Recombinant antigens CI, CII, CIII carrying 1-3 copies of HBV preS1 (21-47) individually could form virus-like particles (VLPs), similar to HBcAg in morphology. But recombinant antigens carrying 4-6 copies of HBV preS1 (21-47) were poorly expressed in E.coli. Chimeric antigens were lacking of immunoreactivity with anti-HBc monoclonal antibodies (McAbs), but still reserved good immunoreactivity with anti-HBe McAbs. CI, CII, CIII could strongly react with anti-preS1 McAb, suggesting that preS1 (21-47) fragment was well exposed on the surface of chimeric VLPs. Three chimeric VLP antigens (CI, CII and CIII) could stimulate mice to produce high-level antibody responses, and their immunogenicity was stronger than non-particulate antigen 21-47*6, containing 6 copies of preS1 (21-47). Mouse antibodies to CI, CII and CIII were able to capture HBV virions in immuno-capture PCR assay in vitro.

CONCLUSION: Chimeric particulate antigens of receptor binding site-core antigen of HBV can elicit strong antibody responses to preS1. They have a potential to be developed into prophylactic or therapeutic vaccines against HBV infection.

In vivo neutralization of hepatitis B virus infection by an anti-preS1 humanized antibody in chimpanzees

Previously, we generated a murine monoclonal antibody (mAb), KR127, that recognizes amino acids (aa) 37-45 of the preS1 of hepatitis B virus (HBV). In this study, we have constructed a humanized version of KR127 and evaluated its HBV-neutralizing activity in chimpanzees. A study chimpanzee was given a single intravenous dose of the humanized antibody, followed by intravenous challenge with adr subtype of wild type HBV, while a control chimpanzee was only challenged with the virus. The result showed that the study chimpanzee did not develop HBV infection during 1 year, while the control chimpanzee was infected, indicating that the humanized antibody exhibited in vivo virus-neutralizing activity and thus protected the chimpanzee from HBV infection. In addition, the humanized antibody bound to the preS1 of all subtypes of HBV. We first demonstrate that an anti-preS1 mAb can neutralize HBV infection in vivo. This humanized antibody will be useful for the immunoprophylaxis of HBV infection.

A new epitope tag from hepatitis B virus preS1 for immunodetection, localization and affinity purification of recombinant proteins

Previously, a murine monoclonal antibody (mAb) KR127 (IgG2a/kappa) that binds specifically to the preS1 of hepatitis B virus (HBV) was generated and the fine epitope was mapped to amino acids (aa) 37-45 (NSNNPDWDF). In this current study, the epitope in combination with KR127 was tested for protein tagging. Initially, to evaluate the importance of each residue of the KR127 epitope in antibody binding, alanine substitution mutants of the epitope were constructed and characterized for KR127 binding by immunoblot analysis and competition ELISA. The results showed that substitution of Ser(38) by alanine (S38A) increased the affinity to KR127. The mutated epitope (NANNPDWDF), designated S1 tag, was fused to the amino (N)- or carboxyl (C)-terminus of three human recombinant proteins, soluble B lymphocyte stimulator (sBLyS), the N-terminal domain of thrombopoietin (nTPO), and a mitochondrial ribosomal protein (CGI-113) for expression in mammalian cells, while it was fused to the N- or C-terminus of two proteins, a single-chain antibody fragment (ScFv) and the carboxyl-terminal domain (PAc) of the protective antigen of Bacillus anthracis for expression in Escherichia coli. The immunodetection, immunoprecipitation, and affinity purification of the expressed S1-tagged proteins by KR127 were successfully demonstrated. In addition, a KR127 mutant (AP2) with higher affinity, K(d) (0.9 nM), for the S1 tag compared to that (20 nM) of KR127 was obtained by mutational analysis of the heavy chain CDR3 (HCDR3) of KR127. The AP2 antibody was 4-fold more sensitive in detecting the S1-tagged protein than KR127. The S1 tag-KR127 or AP2 combination could be universally used for monitoring protein expression, localizing proteins, and protein purification, as well as studying protein interactions.

The comparison of antibody response to different hepatitis b vaccines with and without pre-S2 antigen in children with cancer

Children with cancer are at an increased risk of hepatitis B infection and chronic liver disease. Since hepatitis B vaccines containing pre-S2 antigen has been recently reported as being more efficient in providing immunization in healthy individuals, the authors compared antibody response to pre-S2-containing vaccine with no-pre-S2-containing hepatitis B vaccine, when given in double doses to 100 children receiving chemotherapy. Patients, aged 1 to 16 years with negative HBV serology, were vaccinated with 2 different types of HBV vaccines between 1997 and 1999. Group 1 received Gen Hevac B containing pre-S2 (n = 41) in a dose of 20 microg for patients younger than 10 years old and 40 microg for older patients. Group 2 was vaccinated at the same dose with hepatitis B vaccines not containing pre-S2 antigen. All vaccinations were repeated at 0, 1, and 6 months. Serum samples were drawn for determination of anti-HBs titers at 1, 3, 6, and 8 months. After the third dose of vaccine, the seroconversion rate was 72% in group 1 and 62% in group 2. The anti-HBs levels were higher in the group receiving pre-S2-containing hepatitis B vaccine. However, the difference between groups was not statistically significant (p > .05). The administration of pre-S2-containing hepatitis B vaccines may give a better seroconversion and higher antibody response to vaccination in children with cancer. But a further large-scale study is needed to confirm this finding.

Detection of anti-preS1 antibodies for recovery of hepatitis B patients by immunoassay

AIM: To establish a convenient immunoassay method based on recombinant antigen preS1(21-119 aa) to detect anti-preS1 antibodies and evaluate the clinical significance of antibodies in hepatitis B.

METHODS: The expression plasmid pET-28a-preS1 was constructed, and a large quantity of preS1(21-119 aa) fragment of the large HBsAg protein was obtained. The preS1 fragment purified by Ni²⁺-IDA affinity chromatography was used as coated antigen to establish the indirect ELISA based on streptavidin-biotin system for detection of the anti-preS1 antibodies in sera from HBV-infected patients. For follow-up study, serial sera were collected during the clinical course of 21 HBV-infected patients and anti-preS1 antibodies, preS1 antigen, HBV-DNA and other serological HBV markers were analyzed.

RESULTS: preS1(21-119 aa) fragment was highly expressed from the plasmid pET-28a-preS1 in a soluble form in E. coli (30 mg•L⁻¹), and easily purified to high purity over 90% by one step of Ni²⁺-IDA-sepharose 6B affinity chromatography. The purity and antigenicity of the purified preS1(21-119 aa) protein was determined by 150 g•L⁻¹ SDS-PAGE, Western blot and a direct ELISA. Recombinant preS1(21-119 aa) protein was successfully applied in the immunoassay which could sensitively detect the anti-preS1 antibodies in serum specimens of acute or chronic hepatitis B patients. Results showed that more than half of 19 acute hepatitis B patients produced anti-preS1 antibodies during recovery of the disease, however, the response was only found in a few of chronic patients. In the clinical follow-up study of 11 patients with anti-preS1 positive serological profile, HBsAg and HBV-DNA clearance occurred in 6 of 10 acute hepatitis B patients in 5-6 mo, and seroconversion of HBeAg and disappearance of HBV-DNA occurred in 1 chronic patients treated with lavumidine, a antiviral agent.

CONCLUSION: The high-purity preS1(21-119 aa) coated antigen was successfully prepared by gene expression and affinity chromatography. Using this antigen, a conveniently detective system of anti-preS1 antibodies in sera was established. Preliminarily clinical trial the occurrence of anti-preS1 antibodies in acute hepatitis B patients suggests the clearance of HBV from serum in a short-term time, and anti-preS1 positive in chronic patients means health improvement or recovery from the disease.

Bioactivity of the vascular endothelial growth factor trapped in fibrin clots: production of IL-6 and IL-8 in monocytes by fibrin clots

The blood coagulation cascade is activated following vascular-wall injury. The serine protease thrombin is the final protease in this cascade that causes the formation of fibrin from fibrinogen. Thrombin also causes the activation of platelets, which are trapped in a fibrin net followed by hemostasis. Platelets gathered into fibrin clots release several growth factors such as platelet-derived growth factor and transforming growth factor beta. In the present study, we demonstrated that the vascular endothelial growth factor (VEGF) could be bound to fibrin clots in the plasma, and that incubation of the endothelial cells with these VEGF-bound fibrin clots induced proliferation of endothelial cells. Thus, it suggests that clot-bound VEGF may play a role in wound healing through the proliferation of endothelial cells and vascular smooth-muscle cells. On the other hand, a noticeable migration of monocytes was observed when they were cultured on dishes in the presence of VEGF-bound fibrin clots. Moreover, peripheral blood monocytes incubated in the presence of VEGF-bound fibrin clots strikingly increased the production of IL-6 and IL-8, demonstrating that VEGF trapped in fibrin clots not only induces proliferation of human umbilical vein endothelial cells and migration of monocytes but also enhances secretion of IL-6 and IL-8. Thus, our data suggest that fibrin clots that contain several growth factors act as a bioactive reservoir and may play an important role in hemostasis as well as wound healing.

Fine mapping of virus-neutralizing epitopes on hepatitis B virus PreS1

We identified the epitopes on the preS1 which induce antibodies that neutralize both ad and ay subtypes of hepatitis B virus (HBV). Previously we generated murine monoclonal antibodies KR359 and KR127 that bind specifically to the preS1 of HBV. In this study we have performed fine mappings of the epitopes of the antibodies by examining their reactivity with GST fusion proteins, which contain a series of deletion mutants of the preS1. KR359 and KR127 specifically recognize aa 19-26 and 37-45 of the preS1, respectively. The antibodies neutralized both adr and ayw subtypes of the virus in an in vitro neutralization assay using in vitro infection of adult human hepatocyte primary culture by HBV. The epitopes showed little sequence divergence and the antibodies bound to the preS1 of all the HBV subtypes and variants tested.