Identification of factors associated with sarcopenic obesity development: Literature review and expert panel voting

Sarcopenic obesity (SO) is defined as the combination of excess fat mass (obesity) and low skeletal muscle mass and function (sarcopenia). The identification and classification of factors related to SO would favor better prevention and diagnosis. The present article aimed to (i) define a list of factors related with SO based on literature analysis, (ii) identify clinical conditions linked with SO development from literature search and (iii) evaluate their relevance and the potential research gaps by consulting an expert panel. From 4746 articles screened, 240 articles were selected for extraction of the factors associated with SO. Factors were classified according to their frequency in the literature. Clinical conditions were also recorded. Then, they were evaluated by a panel of expert for evaluation of their relevance in SO development. Experts also suggested additional factors. Thirty-nine unique factors were extracted from the papers and additional eleven factors suggested by a panel of experts in the SO field. The frequency in the literature showed insulin resistance, dyslipidemia, lack of exercise training, inflammation and hypertension as the most frequent factors associated with SO whereas experts ranked low spontaneous physical activity, protein and energy intakes, low exercise training and aging as the most important. Although literature and expert panel presented some differences, this first list of associated factors could help to identify patients at risk of SO. Further work is needed to confirm the contribution of factors associated with SO among the population overtime or in randomized controlled trials to demonstrate causality.

Vitamin D deficiency contributes to overtraining syndrome in excessive trained C57BL/6 mice

Overtraining syndrome is a condition resulting from excessive training load associated with inadequate recovery and poor sleep quality, leading to performance decrements and fatigue. Here we hypothesized that vitamin D (VitD) deficiency is a lead factor in the development of the overtraining syndrome. To test this hypothesis, two groups of 60-week-old C57BL/6 mice followed a 16-week excessive eccentric-based overtraining by excessive downhill running with or without dietary VitD depletion (EX and EX-D- groups). Two control groups were trained by uphill running at the same load with or without VitD depletion (CX and CX-D- groups). Handgrip strength decreased throughout the protocol for all groups but the decrease was sharper in EX-D- group (VitD × training, p = 0.0427). At the end of the protocol, the mass of Triceps brachii muscle, which is heavily stressed by eccentric contractions, was reduced in eccentric-trained groups (training effect, p = 0.0107). This atrophy was associated with a lower concentration of the anabolic myokine IL-15 (training effect, p = 0.0314) and a tendency to a higher expression of the atrogene cathepsin-L (training effect, p = 0.0628). VitD depletion led to a 50% decrease of the fractional protein synthesis rate in this muscle (VitD effect, p = 0.0004) as well as decreased FGF21 (VitD effect, p = 0.0351) and increased osteocrin (VitD effect, p = 0.038) concentrations that would lead to metabolic defects. Moreover, the proportion of anti-inflammatory Th2 lymphocytes was significantly decreased by the combination of eccentric training with VitD depletion (vitD × training, p = 0.0249) suggesting a systemic inflammation. Finally, exploratory behavior time of mice was decreased by VitD depletion (VitD effect, p = 0.0146) suggesting a cognitive dysfunction. Our results suggest that VitD deficiency exacerbates the effects of overtraining.

Editorial Special Issue: 2021 consortium for trans-pyrenean investigations on obesity and diabetes

This Special Issue of the Journal of Physiology and Biochemistry contains 7 contributions that have been elaborated in the context of the mini-network "Consortium of Trans-Pyrenean Investigations on Obesity and Diabetes" (CTPIOD), which is on its 18th year of existence. This scientific community, mostly involving research groups from France and Spain, but also open to participants coming from all over the world, is focusing its attention on the prevention and the novel treatments of obesity, diabetes, non-alcoholic fatty liver disease, and other noncommunicable diseases. Accordingly, this special issue covers some nutritional, pharmacologic, and genetic aspects of the current knowledge of metabolic diseases. Some of these papers emerge from the lectures of the 18th Conference on Trans-Pyrenean Investigations in Obesity and Diabetes, organized by the University of Clermont-Ferrand and celebrated online in November 30, 2021.

Dataset of night-time emissions of the Earth in the near UV range (290-430 nm), with 6.3 km resolution in the latitude range -51.6<L<+51.6 degrees, acquired on board the International Space Station with the Mini-EUSO detector

The data presented in this article are related to the research paper entitled "Observation of night-time emissions of the Earth in the near UV range from the International Space Station with the Mini-EUSO detector" (Remote Sensing of Environment, Volume 284, January 2023, 113336, https://doi.org/10.1016/j.rse.2022.113336). The data have been acquired with the Mini-EUSO detector, an UV telescope operating in the range 290-430 nm and located inside the International Space Station. The detector was launched in August 2019, and it has started operations from the nadir-facing UV-transparent window in the Russian Zvezda module in October 2019. The data presented here refer to 32 sessions acquired between 2019-11-19 and 2021-05-06. The instrument consists of a Fresnel-lens optical system and a focal surface composed of 36 multi-anode photomultiplier tubes, each with 64 channels, for a total of 2304 channels with single photon counting sensitivity. The telescope, with a square field-of-view of 44°, has a spatial resolution on the Earth surface of 6.3 km and saves triggered transient phenomena with a temporal resolution of 2.5 µs and 320 µs. The telescope also operates in continuous acquisition at a 40.96 ms scale. In this article, large-area night-time UV maps obtained processing the 40.96 ms data, taking averages over regions of some specific geographical areas (e.g., Europe, North America) and over the entire globe, are presented. Data are binned into 0.1° × 0.1° or 0.05° × 0.05° cells (depending on the scale of the map) over the Earth's surface. Raw data are made available in the form of tables (latitude, longitude, counts) and .kmz files (containing the .png images). These are - to the best of our knowledge - the highest sensitivity data in this wavelength range and can be of use to various disciplines.

A Review of the EUSO-Balloon Pathfinder for the JEM-EUSO Program

EUSO-Balloon is a pathfinder for JEM-EUSO, the mission concept of a spaceborne observatory which is designed to observe Ultra-High Energy Cosmic Ray (UHECR)-induced Extensive Air Showers (EAS) by detecting their UltraViolet (UV) light tracks "from above." On August 25, 2014, EUSO-Balloon was launched from Timmins Stratospheric Balloon Base (Ontario, Canada) by the balloon division of the French Space Agency CNES. After reaching a floating altitude of 38 km, EUSO-Balloon imaged the UV light in the wavelength range ∼290-500 nm for more than 5 hours using the key technologies of JEM-EUSO. The flight allowed a good understanding of the performance of the detector to be developed, giving insights into possible improvements to be applied to future missions. A detailed measurement of the photoelectron counts in different atmospheric and ground conditions was achieved. By means of the simulation of the instrument response and by assuming atmospheric models, the absolute intensity of diffuse light was estimated. The instrument detected hundreds of laser tracks with similar characteristics to EASs shot by a helicopter flying underneath. These are the first recorded laser tracks measured from a fluorescence detector looking down on the atmosphere. The reconstruction of the direction of the laser tracks was performed. In this work, a review of the main results obtained by EUSO-Balloon is presented as well as implications for future space-based observations of UHECRs.

Enhanced glucocorticoid-induced leucine zipper in dendritic cells induces allergen-specific regulatory CD4(+) T-cells in respiratory allergies

BACKGROUND

Respiratory allergies rely on a defect of IL-10-secreting regulatory CD4(+) T-cells (IL-10-Tregs ) leading to excessive Th2-biased immune responses to allergens. According to clinical data, the restoration of allergen-specific IL-10-Tregs is required to control respiratory allergies and cure patients. The discovery of mechanisms involved in the generation of IL-10-Tregs will thus help to provide effective treatments. We previously demonstrated that dendritic cells (DCs) expressing high levels of the glucocorticoid-induced leucine zipper protein (GILZ) generate antigen-specific IL-10-Tregs .

OBJECTIVE

We suspect a defective expression of GILZ in the DCs of respiratory allergic patients and speculate that increasing its expression might restore immune tolerance against allergens through the induction of IL-10-Tregs .

METHODS

We assessed GILZ expression in blood DCs of patients and healthy nonallergic donors by qPCR. We compared the ability of patients' DCs to induce allergen-specific IL-10-Tregs before and after an in vivo up-regulation of GILZ expression by steroid administration, steroids being inducers of GILZ.

RESULTS

We report lower levels of GILZ in DCs of respiratory allergic patients that return to normal levels after steroid administration. We show that patients' DCs with increased levels of GILZ generate allergen-specific IL-10-Tregs again. We further confirm unequivocally that GILZ is required in patients' DCs to activate these IL-10-Tregs .

CONCLUSION

This proof of concept study shows that the re-establishment of GILZ expression in patients' DCs to normal levels restores their capacity to activate allergen-specific IL-10-Tregs . We thus highlight the up-regulation of GILZ in DCs as a new interventional approach to restore the immune tolerance to allergens.

Resistance to high-fat-diet-induced obesity and sexual dimorphism in the metabolic responses of transgenic mice with moderate uncoupling protein 3 overexpression in glycolytic skeletal muscles

AIMS/HYPOTHESIS

Uncoupling protein (UCP) 3 is a mitochondrial inner membrane protein expressed predominantly in glycolytic skeletal muscles. Its role in vivo remains poorly understood. The aim of the present work was to produce a mouse model with moderate overproduction and proper fibre-type distribution of UCP3.

METHODS

Transgenic mice were created with a 16 kb region encompassing the human UCP3 gene. Mitochondrial uncoupling was investigated on permeabilised muscle fibres. Changes in body weight, adiposity and glucose or insulin tolerance were assessed in mice fed chow and high-fat diets. Indirect calorimetry was used to determine whole-body energy expenditure and substrate utilisation.

RESULTS

Transgenic mice showed a twofold increase in UCP3 protein levels specifically in glycolytic muscles. Mitochondrial respiration revealed an increase of uncoupling in glycolytic but not in oxidative muscles. Transgenic mice gained less weight than wild-type littermates due to lower adipose tissue accretion when fed a high-fat diet. Animals showed a sexual dimorphism in metabolic responses. Female transgenic mice were more glucose-sensitive than wild-type animals, while male transgenic mice with high body weights had impaired glucose and insulin tolerance. Measurements of RQs in mice fed chow and high-fat diets suggested an impairment of metabolic flexibility in transgenic male mice.

CONCLUSIONS/INTERPRETATION

Our data show that physiological overproduction of UCP3 in glycolytic muscles results in mitochondrial uncoupling, resistance to high-fat diet-induced obesity and sex specificity regarding insulin sensitivity and whole-body substrate utilisation.

Chemokine receptor expression on allergen-specific T cells in asthma and allergic bronchopulmonary aspergillosis

BACKGROUND

Allergic bronchopulmonary aspergillosis (ABPA) is a rare variant of severe asthma resulting from hypersensitivity to Aspergillus fumigatus (Asp f) present in the airways.

AIMS OF THE STUDY

We analyzed the expression of a panel of six chemokine receptors (CCR3, CCR4, CCR8, CCR5, CXCR3 and CXCR4) on total blood CD4(+) T cells and Asp f-specific-T cells in ABPA patients. We hypothesized that chemokine receptor pattern on T cells differs between ABPA patients, non-ABPA allergic asthmatics sensitized to Dermatophagoides pteronyssinus (Der p) or Phleum pratense (Phl p) and healthy controls.

METHODS

We used the fluorescent dye PKH26, a membrane bound marker, to identify accumulated proliferating (cell-sorted PKH26(low)) CD4(+) T cells in response to allergens (Asp f, Der p, Phl p) or recall antigens (PPD and TT). Chemokine receptor expression was analyzed by flow cytometry on proliferating CD3(+) CD4(+) PKH26(low) cells.

RESULTS

Stimulation of CD4(+) T cells with the relevant allergen resulted in different patterns of chemokine receptor expression in ABPA and non-ABPA allergic asthmatics. Upon Asp f exposure, proliferating CD4(+) T cells from ABPA patients down-regulated the expression of CCR4 and CXCR3 while CCR4 and CXCR3 were up-regulated in allergen-specific T cells from non-ABPA allergic asthmatics. Considering each group of patients, the pattern of chemokine receptors expressed on proliferating allergen-specific CD4(+) T cells was similar to that expressed by recall antigen-specific T cells.

CONCLUSIONS

The down-regulation of CCR4 and CXCR3 after allergen exposure in Asp f-specific T cells seems to be a characteristic feature of ABPA patients and requires further evaluation.

Fractalkine-induced smooth muscle cell proliferation in pulmonary hypertension

Pulmonary hypertension is characterised by a progressive increase in pulmonary arterial resistance due to endothelial and smooth muscle cell proliferation resulting in chronic obstruction of small pulmonary arteries. There is evidence that inflammatory mechanisms may contribute to the pathogenesis of human and experimental pulmonary hypertension. The aim of the study was to address the role of fractalkine (CX3CL1) in the inflammatory responses and pulmonary vascular remodelling of a monocrotaline-induced pulmonary hypertension model. The expression of CX3CL1 and its receptor CX3CR1 was studied in monocrotaline-induced pulmonary hypertension by means of immunohistochemistry and quantitative reverse-transcription PCR on laser-captured microdissected pulmonary arteries. It was demonstrated that CX3CL1 was expressed by inflammatory cells surrounding pulmonary arterial lesions and that smooth muscle cells from these vessels had increased CX3CR1 expression. It was then shown that cultured rat pulmonary artery smooth muscle cells expressed CX3CR1 and that CX3CL1 induced proliferation but not migration of these cells. In conclusion, the current authors proposed that fractalkine may act as a growth factor for pulmonary artery smooth muscle cells. Chemokines may thus play a role in pulmonary artery remodelling.

Dexamethasone and IL-10 stimulate glucocorticoid-induced leucine zipper synthesis by human mast cells

BACKGROUND

Glucocorticoids (GCs) decrease tissue mast cell (MC) number and prevent their activation via their high-affinity IgE receptor. Glucocorticoid-induced leucine zipper (GILZ) is one of the GC-induced genes, which inhibits the functions of the transcriptional activators AP-1 and NF-kappaB. GILZ appears to be a critical actor in the anti-inflammatory and immunosuppressive effects of GCs in human T lymphocytes, macrophages and dendritic cells.

AIMS OF THE STUDY

We investigated whether GILZ was produced by human MCs and whether GILZ synthesis was stimulated by GCs. We also investigated whether GILZ production was modulated by (i) IL-10, because of its common immunosuppressive properties with GCs, (ii) histamine because of its pro-inflammatory properties and (iii) IL-4 and IL-5 because of their ability to favour MC survival and proliferation with SCF.

METHODS

The human MC lines HMC-1 5C6 and LAD-2, and cord blood-derived MCs (CB-MCs) were cultured alone or in the presence of GCs, IL-10, histamine, IL-4 or IL-5. The expression of GILZ was evaluated by using RT-PCR, Western blotting or immunocytochemistry.

RESULTS

We found that human MC lines and CB-MCs constitutively produce GILZ. We also show that GCs and IL-10 stimulate GILZ production by human MCs. Our present results indicate that histamine, IL-4 and IL-5 alone or in combination with SCF do not downregulate GILZ production by MCs.

CONCLUSIONS

These results show that GCs and IL-10 stimulate GILZ production by human MCs. As GILZ mediates anti-inflammatory effects of GCs in immune cells, we speculate that GILZ could account for the deactivation of MCs by GCs and IL-10.

Calcium overload increases oxidative stress in old rat gastrocnemius muscle

In order to challenge in vivo muscle Ca2+ homeostasis and analyze consequences on mitochondrial H2O2 release (MHR) and sarcopenia, we injected Ca2+ ionophore A23187 (200 microg/kg, ip) in adult and old rats and measured gastrocnemius mass and mitochondrial Ca2+ content (MCC) using radioactive Ca2+ 48 h after injection. In a second experiment performed in old rats, we measured isocitrate dehydrogenase (ICDH) activity as an index of MCC, MHR, mitochondrial respiration, citrate synthase, COX and antioxydant enzyme activities 24 h after a 150 microg/kg injection. In adult rats, muscle mass and MCC were unchanged by A23187. In old rats, MCC increased 24 h after injection as reflected by a significant increase in ICDH activity; measured MCC tended to increase at 48 h. MHR and Mn-SOD activity were significantly increased at 24 h, and GPX activity was reduced. Muscle mass was unchanged but was negatively correlated with MCC in control and treated old rats. In conclusion, in old rats, A23187 probably induced a mitochondrial Ca2+ overload responsible for the observed increase in MHR without leading to muscle atrophy on a short term basis.

Due to reverse electron transfer, mitochondrial H2O2 release increases with age in human vastus lateralis muscle although oxidative capacity is preserved

Age-related changes in mitochondrial H2O2 release (MHR) could be responsible for an increase in oxidative stress in skeletal muscle and participate in the development of sarcopenia. We compared MHR in vastus lateralis biopsies obtained from young (23.5+/-2.0 year, n=6) and elderly (67.3+/-1.5 year, n=6) healthy sedentary men. Isolated mitochondria were incubated in the presence of glutamate/malate/succinate, with or without rotenone. Muscle fat oxidative capacity, citrate synthase, complex II, complex III, and cytochrome c oxidase activities were also measured. In parallel, we analyzed in gastrocnemius of young male Wistar rats (n=6), the impact of lidocaine (local anesthetic used in humans) on mitochondrial respiration and MHR. In humans, muscle oxidative capacity was preserved with age but muscle MHR was markedly enhanced in elderly subjects compared to young adults (+175%, P<0.05). Rotenone abolished this increase, demonstrating that it was due to a free radical release during reverse electron transfer from complex II towards complex I. Lidocaine can interfere with MHR measurements (intra-muscular injection in rats) but it can be avoided by minimizing contact with muscle (small multiple subcutaneous injections in humans). Physiologic consequences of the observed increase in muscle MHR with aging remain to be determined.

Evaluation of CD4+ T cells proliferating to grass pollen in seasonal allergic subjects by flow cytometry

Our objective was to characterize T-cell responses to Phleum pratense in grass pollen allergic individuals and healthy controls using the fluorescent dye PKH26. Peripheral blood mononuclear cells were stimulated with P. pratense, or with recall antigens, and CD3+/CD4+ and CD3+/CD8+ T-cells that had proliferated were analysed by flow cytometry. In the presence of P. pratense CD4+/CD3+ T-cells proliferated more in grass pollen sensitive atopic patients than in nonallergic controls or in nongrass pollen sensitive atopic subjects. PPD and TT recall antigens elicited uniformly high proliferation in all T-cell subsets. Only half of pollen sensitive patients also had an increased proliferation of CD3+/CD8+ T-cells in response to P. pratense. We determined precursor frequency of CD4+ T cells in the original population that responded to P. pratense and found values ranging from 1 x 10-3 to 0.6 x 10-1, in the same range as those measured for PPD and TT. In conclusion, grass pollen sensitive atopic patients show enhanced CD4+ T-cell reactivity to P. pratense, and this could be related to the presence of elevated numbers of circulating allergen-specific CD4+ T cells. This flow cytometric method should allow the identification of other phenotypic markers such as intracellular cytokines in allergen specific responding CD4+ T cells.

Expression of Epstein-Barr virus-induced gene 3, an interleukin-12 p40-related molecule, throughout human pregnancy: involvement of syncytiotrophoblasts and extravillous trophoblasts

In human pregnancy, trophoblasts are the only cells of fetal origin in direct contact with the maternal immune system: syncytiotrophoblasts are in contact with maternal blood, whereas extravillous trophoblasts are in contact with numerous maternal uterine natural killer (NK) cells. Therefore, trophoblasts are thought to play a key role in maternal tolerance to the semiallogeneic fetus, in part through cytokine production and NK cell interaction. Epstein-Barr virus-induced gene 3 (EBI3) encodes a soluble hematopoietin receptor related to the p40 subunit of interleukin-12. Previous studies indicated that EBI3 is expressed in the spleen and tonsils, and at high levels in full-term placenta. To investigate further EBI3 expression throughout human pregnancy, we generated monoclonal antibodies specific for EBI3 and developed an EBI3 enzyme-linked immunosorbent assay. Immunohistochemical experiments with EBI3 monoclonal antibody on first-, second-, and third-trimester placental tissues demonstrated that EBI3 was expressed throughout pregnancy by syncytiotrophoblasts and extravillous trophoblasts (cytotrophoblast cell columns, interstitial trophoblasts, multinucleated giant cells, and trophoblasts of the chorion laeve). EBI3 expression was also induced during in vitro differentiation of trophoblast cell lines. In addition, large amounts of secreted EBI3 were detected in explant cultures from first-trimester and term placentae. Consistent with these data, EBI3 levels were strongly up-regulated in sera from pregnant women and gradually increased with gestational age. These data, together with the finding that EBI3 peptide is presented by HLA-G, suggest that EBI3 is an important immunomodulator in the fetal-maternal relationship, possibly involved in NK cell regulation.

Evaluation of an enzyme-linked immunosorbent assay for detection and quantification of hepatitis B virus PreS1 envelope antigen in serum samples: comparison with two commercial assays for monitoring hepatitis B virus DNA

An in-house sensitive and easy-to-use solid-phase enzyme-linked immunoassay (ELISA) was adapted for the detection and quantification of hepatitis B virus (HBV) PreS1 envelope antigen in serum, and compared with the HBV DNA Hybrid Capturetrade mark system from Murex and the polymerase chain reaction (PCR) Amplicortrade mark HBV Monitor assay from Roche. Twenty-five patients with chronic hepatitis B after liver transplantation were included in this study. The sensitivity of our ELISA was found to be 50 pg of HBsAg/PreS1Ag ml-1. The linearity was between 0.1 and 100 ng ml-1. Intra-assay reproducibility was obtained with a standard deviation of <1%. No correlation between the presence of serum PreS1 antigen and viral DNA detected by direct hybridization (Murex) was observed. In contrast, there was a significant 96% correspondence in the presence of PreS1 antigen and viral DNA detected and quantified by the PCR assay (Roche). In conclusion, the most important and reliable markers for monitoring residual HBV replication in serum were HBV DNA by the PCR assay, and virus envelope PreS1Ag by our in-house ELISA. Thus, PreS1Ag disappearance in serum could be used for evaluating the efficacy of antiviral therapies.

Phosphorylation of the hepatitis B virus core protein by glyceraldehyde-3-phosphate dehydrogenase protein kinase activity

In order to characterize the hepatitis B virus (HBV) hepatocellular receptor, several proteins have previously been identified in HepG2 hepatoma cells and in primary cultured normal human hepatocytes (PCHs) that reacted with an anti-idiotypic antibody against a preS1(21-47)-specific MAb (F35.25). Here, we report the identification of one of these preS1-binding proteins, a 35 kDa protein (preS1-BP35), as glyceraldehyde-3-phosphate dehydrogenase (GAPD). GAPD is well-known as a key enzyme involved in glycolysis and gluconeogenesis. Nevertheless, GAPD has also been shown to have many other functions such as protein kinase activity (GAPD-PK). HBV core particles derived from infected hepatocytes possess an associated kinase activity that phosphorylates HBcAg, and the nucleocapsid may acquire sequential functions through selective phosphorylation. Therefore, we have investigated the potential role of GAPD-PK in HBV replication. In this study, we found that the endogenous PK associated with human liver-derived HBV core particles (hL-HBcAg) and GAPD-PK were sensitive to the same types of inhibitors. Interestingly, capsid protein phosphorylation decreased in a concentration-dependent manner (at concentrations of 5-30 mM) in the presence of specific inhibitors for GAPD-PK (NADH and GAP). Furthermore, we demonstrated in vitro that GAPD-PK could phosphorylate the major core protein P22 in hL-HBcAg particles. The data suggest that GAPD is an additional cellular kinase which might interfere in the life-cycle of HBV.

Suppressive effect of hepatitis B virus on the induction of interleukin-1 beta and interleukin-6 gene expression in the THP-1 human monocytic cell line

The major target organ for Hepatitis B Virus (HBV) is the liver, but extrahepatic sites including monocytes express receptors for HBV and may become infected. Therefore, we investigated the effect of HBV on the in vitro expression of interleukin-beta (IL-1 beta) and interleukin-6 (IL-6) by the monocytoid cell line THP-1, exposed to various stimuli (LPS, PMA or both). Nonstimulated THP-1 cells did not synthesize IL-1 beta and IL-6, even after in vitro exposure to HBV. LPS stimulation alone induced moderate secretion of both IL-1 beta and IL-6 (300 pg/ml). After induction of macrophage differentiation by PMA, THP-1 cells acquired adherence and expressed a higher level of IL-1 beta (up to 2 ng/ml) but did not synthesize IL-6. Treatment of THP-1 cells with PMA and LPS caused the highest production of both IL-1 beta and IL-6 (> 5ng/ml). In vitro exposure of PMA + LPS-stimulated THP-1 cells to HBV resulted in secretion of both HBsAg and preS2Ag which was maintained over 10 days of culture. Southern blot technique was used to study the state of HBV DNA in the cells. Hybridization of non-digested cellular DNA showed only high molecular weight HBV DNA forms. The HindIII restriction pattern revealed bands corresponding to large DNA fragments and the presence of bands at the 3.2 kb position. Under these conditions (PMA + LPS), HBV inhibited the production of IL-1 beta and IL-6 proteins and completely suppressed the IL-1 beta and IL-6 mRNA. Thus, our findings (i) strongly support a relationship between the state of cell differentiation and susceptibility of cells to HBV infection, and (ii) demonstrate that HBV exerts an inhibitory effect on the induction of IL-1 beta and IL-6 genes expression in monocytic THP-1 cells. These results suggest that HBV leads to a fall of pro-inflammatory cytokine production by monocytes/macrophages, which may contribute to impaired host immune response during infection.

In vivo selection of a hepatitis B virus mutant with abnormal viral protein expression

We have investigated the molecular basis for the in vivo selective advantage of a hepatitis B virus (HBV) mutant. We have determined the complete nucleotide sequences of the major HBV forms identified at the beginning (B1-83) and end (B1-89) of a 6 year follow-up of a chronically infected patient. The B1-89 sequence showed marked nucleotide rearrangements (a nucleotide divergence of 11.3 % compared with the adw2 subtype), but sequence comparison showed that both viral molecules were of common origin (62/138 mutations were found on both molecules, compared to adw2). In vitro transfection of Huh7 cells showed important modifications in B1-89 viral protein expression. We observed a decrease in B1-89 envelope protein expression associated with a modification of the migration pattern of the large envelope protein. For the B1-89 capsid protein, an insertion of 36 nucleotides at the 5' end of the C gene resulted in increased expression of a core-specific protein of abnormal size (24 kDa versus 22 kDa). Finally, our data also suggest an increase in the transcomplementation efficiency of the mutated B1-89 polymerase protein. Thus, we were able to demonstrate distinct intrinsic properties of HBV DNA molecules isolated from a chronic carrier with virus multiplication at different times during infection. Modifications of viral protein expression in the mutated form illustrate strategies used by the virus to prevent clearance and to contribute to viral persistence.

Primary cultured normal human hepatocytes for hepatitis B virus receptor studies

BACKGROUND/AIMS

We analyzed the hepatitis B virus envelope specificities (HBs, preS2 and preS1) involved in virus attachment to normal human hepatocytes, and we performed in vitro hepatitis B virus infection experiments without addition of dimethyl sulfoxide and polyethylene glycol, which may affect cell membrane integrity, in order to study further the early steps of the life cycle of the hepatitis B virus.

METHODS

Primary normal human hepatocytes were prepared from surgical biopsies by the two-step collagenase perfusion technique, and cultured in a fetal calf serum-free medium supplemented with 10(-6) M dexamethasone. Cell-binding assays, ligand blotting and immunohistochemistry experiments were carried out using our anti-idiotypic (Ab2) antibodies (Ab2s/preS1, Ab2s/preS2 and Ab2s/HBs).

RESULTS

Probing primary normal human hepatocytes, the 35-kDa major preS1-binding protein (preS1-BP35) we have previously identified in human hepatoma HepG2 cells was recognized in blotting, whereas both HBs- and preS1-specificities of the hepatitis B virus envelope interacted strongly with normal human hepatocyte cell membrane in cell-binding assays and immunohistochemistry experiments. Hepatitis B virus infectivity studies confirmed a great inter-experimental variability depending on donors and liver perfusion, and demonstrated a great intra-experimental variability depending on the serum-derived hepatitis B virus isolate used for the inoculation. In our culture conditions, only increased detection of the RC and CCC DNA forms of hepatitis B virus in cells and of hepatitis B virus surface antigens in medium was observed 4 to 8 days after exposure of cells to hepatitis B virus.

CONCLUSION

These findings support a potential role for preS1-BP35 as a receptor protein for hepatitis B virus. In our hands, limitation(s) in the hepatitis B virus life cycle may occur at some step after virion binding, and likely result from complex regulation of reverse transcription of the RNA and translation of core protein by extrahepatic host factors or/and by the virus itself. However, the normal human hepatocyte model developed here is available for studying the initial steps in hepatitis B virus entry into cells.

[Clinical and virological evaluation of the detection of pre-S1 and pre-S2 antigens in serum from patients with chronic hepatitis B]

OBJECTIVES AND METHODS

We performed a prospective study to determine the clinical and virological significance of pre-S antigen detection in serum samples from patients with chronic hepatitis B virus infection. Four hundred thirty seven consecutive serum samples from 116 patients were tested for the presence of both pre-S1 and pre-S2 antigens by radioimmunoassay using specific monoclonal antibodies.

RESULTS

The pre-S1 antigen/HBs antigen ratio, gave an estimation of the number of pre-S1 epitopes expressed on the surface of circulating viral particles, and was positively correlated with the intensity of viral replication intensity (P < 0.05). Moreover, the pre-S1 antigen/HBs antigen ratio was significantly higher in patients suffering from chronic hepatitis associated with viral replication (24% +/- 13); in anti-HBe positive patients, the pre-S1 antigen/HBs antigen ratio was higher in patients replicating a HBe antigen minus variant of the hepatitis B virus and suffering from chronic hepatitis (17% +/- 9) than in asymptomatic HBs antigen carriers (5% +/- 6) (P < 0.05). The pre-S2 antigen/HBs antigen ratio was not correlated with the level of viral replication or with the patient's clinical status.

CONCLUSION

This study confirms that pre-S1 antigen detection is a reliable marker of hepatitis B virus replication which can be easily performed in chronically infected patients. This assay is especially useful in identifying anti-HBe positive carriers who replicate a minus pre-core mutant and could benefit from antiviral therapy.

In vivo and in vitro expression of defective hepatitis B virus particles generated by spliced hepatitis B virus RNA

The mechanisms involved in hepatitis B virus (HBV) persistence are still poorly understood. We have previously shown that the encapsidation of the singly spliced 2.2 kb-HBV RNA leads to the secretion of circulating HBV defective particles in patients with chronic hepatitis. We have now investigated the presence of the HBV defective particles in sera from patients with acute and chronic hepatitis, using polymerase chain reaction. These defective particles were detected in a larger amount in sera of patients with acute hepatitis that progressed to chronic hepatitis, or had already developed chronic hepatitis, as compared with those who recovered from acute hepatitis (the increase was estimated to be an average of 50-fold). In addition, we showed that the presence of these defective HBV particles is closely associated with the chronic course of hepatitis B virus infection and with viral multiplication. We also analyzed viral RNAs and proteins synthetized after in vitro transfection of Huh7 cell line with the corresponding defective hepatitis B virus DNA molecule. We showed that expression of the defective hepatitis B virus DNA alone leads to a marked intracellular accumulation of the major core protein (HBcAg) and to an increased secretion of hepatitis B e antigen (HBeAg). These observations may be consistent with a role of these defective hepatitis B virus (HBV) particles in viral persistence.

In vitro infection of human hepatoma cells (HepG2) with hepatitis B virus (HBV): spontaneous selection of a stable HBV surface antigen-producing HepG2 cell line containing integrated HBV DNA sequences

The degree of susceptibility of human hepatoma (HepG2) cells to direct hepatitis B virus (HBV) infection remains unknown. We previously observed a low level of Dane particle production and viral DNA replication after in vitro infection of HepG2 cells with serum-derived HBV. However, this culture system appeared to be affected by variations as human hepatocyte cultures. In the present study, HBV infection of HepG2 cells led to a significant increase in the secretion of three envelope antigens (HBsAg, preS2Ag and preS1Ag) at 4 days post-infection, and Northern blot analysis revealed the presence of both preS1 (2.6 kb) and preS2/S (2.2 kb) transcripts. Expression of preS1Ag and the corresponding viral RNA became undetectable on 21 days post-infection whereas the 2.2 kb RNA species persisted and was associated with secretion of subviral HBs particles expressing preS2-epitopes and banding between 30 and 35% sucrose. At 35 days post-infection (fifth passage), a sudden high level production of HBsAg and preS1Ag was observed, followed by a massive cell death (90%). A stable HBsAg-producing HepG2 cell line, designated HepG2-BV3, grew out of the surviving cells. HepG2-BV3 cells could integrate HBV DNA sequences and produce the three HBV surface antigens. Treatment with dexamethasone increased the HBsAg and preS1Ag secretion. Such a HBsAg-producing HepG2 cell line obtained by in vitro HBV infection seems to mimick events that occur in the naturally occurring persistent chronic infection, and therefore may be an efficient in vitro model for studying the contribution of viral integration in the dysregulation of HBV and liver-specific genes expression.

PreS1 antigen/antibody patterns following interferon therapy in acute and chronic hepatitis B

The relation between preS1 antigen/antibody system and different phases of hepatitis B virus infection were studied in 425 serum samples from 50 hepatitis B patients before, during and after antiviral therapy using interferon alone or in combination with corticosteroid withdrawal. A typical profile of self-limited acute hepatitis B was characterized by hepatitis B virus-DNA clearance using polymerase chain reaction and preS antigens using monoclonal radioimmunoassays and by antibody responses to the middle and the large HBs proteins (gp33/gp36 and p39/gp42) using immunoblotting quantitative analysis. After interferon therapy in patients with protracted hepatitis B, complete eradication of the virus was observed in 70% of patients, and antibody response directed to middle HBs and large HBs proteins could be induced. Conversely, this antibody response was never detected in follow-up studies of chronic active hepatitis B patients who responded well to antiviral therapy and lost HBs, preS2 and preS1 antigens. Most interesting, in 50% of patients with HBeAg-positive chronic active hepatitis B who received combination therapy and in 67% of patients with anti-HBe-positive chronic active hepatitis B given interferon alone, the elevated serum preS1Ag/HBsAg ratio persisted after treatment was discontinued and even increased until the end of the follow-up when hepatitis B virus DNA was undetectable in serum by the conventional hybridization technique. This rebound of preS1 antigen expression following antiviral therapy in patients with chronic active hepatitis B may indicate virus persistence, suggesting the possibility of relapse through wild-type hepatitis B virus or the emergence of hepatitis B virus mutants.

Significance and relevance of serum preS1 antigen detection in wild-type and variant hepatitis B virus (HBV) infections

These studies assessed whether the serum expression of preS1 antigen could be a useful HBV marker for monitoring the progress of antiviral therapy in the treatment of chronic active hepatitis B (CAH-B) virus infections. Our findings indicate that: 1) the rearrangements we observed in the preS region of mutated HBV DNA molecules during chronic infection did not effect the preS1 sequence (21-47) critical for HBV infectivity; 2) the persistence or even the rebound of preS1 antigen expression during follow-up in responders to antiviral therapy may indicate virus persistence, suggesting the possibility of relapse through wild-type HBV or the emergence of HBV variants following the immunoelimination phase.

PreS1-specific binding proteins as potential receptors for hepatitis B virus in human hepatocytes

Cellular receptors play an important role in viral pathogenesis. Until now, there has been no reliable information on the receptor(s) for hepatitis B virus (HBV). Therefore, we attempted to identify specific receptors in human hepatocytes using an immunological approach. Anti-idiotypic (Ab2) antibodies were raised in rabbits against our monoclonal antibody (MAb1) F35.25. MAb1 F35.25 (i) recognized the hepatocyte receptor binding site on HBV (located between amino acid residues 21 and 47 of the preS1 sequence) and (ii) blocked the attachment of preS1-positive HBV particles to human hepatocytes. The presence of Ab2 antibodies in rabbit sera was determined by the ability of antisera to inhibit Id (Ab1)/antigen (HBV) recognition. Affinity-purified Ab2 IgGs to F35.25 represented an internal image for the preS1 domain 12-53. Our present studies indicate that Ab2 IgGs to F35.25 (i) recognized the membrane-associated structure of the preS1-specific HBV receptor in a HepG2 cell binding assay, as visualized by immunoenzymatic staining; (ii) strongly bound to a major 35-kDa component and to three other related proteins of 50, 43, and 40 kDa in extracts of HepG2 cells; and (iii) reacted with several soluble and membrane-associated proteins in normal human liver cells. The binding was insensitive to reduction. All preS1 binding proteins were V8 protease sensitive and endoglycosidase H resistant. The 35-kDa species was trypsin resistant and generated a band of 32 kDa by endoglycosidase F treatment. Together, our results suggest that the identified preS1-specific binding proteins may be involved in the putative complex structure of the hepatocyte receptor for HBV.

PreS antigen expression and anti-preS response in hepatitis B virus infections: relationship to serum HBV-DNA, intrahepatic HBcAg, liver damage and specific T-cell response

The diagnostic value of preS antigens and anti-preS antibodies during Hepatitis B virus (HBV) infections have not yet been clearly elucidated. Therefore, the objectives of this study were: 1) to better understand the clinical significance of the expression of both preS1 and preS2 antigens (preS1Ag and preS2Ag) in the serum of chronic HBsAg carriers, and 2) to define the respective role of antibody responses to HBs-, preS2- and preS1-specific determinants in the course of acute hepatitis B (AH-B) infections with different outcomes. Our data showed that the serum preS1Ag/HBsAg ratio correlated well with the level of viral replication (serum HBV-DNA as monitored by PCR assay and liver HBcAg), especially in anti-HBe positive chronic carriers. The complete eradication of virions required a persistent antibody response to conformation-dependent HBs-epitopes, temporally associated with a vigorous T cell response to nucleocapsid antigens. Recovery from hepatitis B can be achieved when there is no early antibody response to preS2- and preS1-proteins, which was found to be transient, concomitant with a flare-up of the liver disease, and preceding anti-HBs production. Information on the patterns of preS antigens and their antibodies remained clouded because of the varying specificities and sensitivities of research methods used in studies to date. We have, therefore, developed original Polyclonal-Monoclonal RadioImmunoAssays (PAb-MAb RIAs) by using monoclonal antibodies (MAbs) having previously well-defined specificities. We could thus detect and quantify simultaneously the three distinct antigenicities of the HBV envelope, HBsAg, preS2Ag and preS1Ag, with the same sensitivity. In this way, the preS1Ag/HBsAg and preS2Ag/HBsAg ratios can be calculated to estimate the serum expression of both preS1Ag and preS2Ag in relation to total HBsAg activity during different stages of chronic HBV infection. For optimal management of the state of HBV replication in chronic viral infection, the detection of HBV-DNA in serum was monitored by the Polymerase Chain Reaction (PCR) assay. We extended our work by investigating the clinical significance of antibody response to preS-specific determinants in patients with AH-B showing different outcomes in both natural course or response to alpha-interferon therapy. In a first attempt, we chose to use the Western Immuno-Blotting Assay (WIBA) to obtain a qualitative assessment of the nature of preS antibody responses. Finally, the cell-mediated immune response to HBV antigens was also studied in several patients with self-limited AH-B leading to a relevant finding which may help to clarify the mechanisms responsible for complete clearance of HBV.

Hepatitis B defective virus with rearrangements in the preS gene during chronic HBV infection

We have found a defective form of HBV2 in a HBsAg- and anti-HBe-positive patient with liver cancer. Viral deletions were identified in the preS coding region using PCR. The presence of deleted HBV forms was observed in serum, PBMC, and liver samples. After sequencing 12 clones were analyzed (subtype adr). In 9 out of 12 clones a 183-bp in-frame deletion was recorded in the preS1 region (2995 to 3177). Three out of 9 clones also yielded rearrangements of the preS2 N-terminal part. Four out of 9 showed numerous point mutations in the preS1 and preS2 sequence. In addition, 3 out of 12 clones, which did not show the 183-bp preS1 deletion were found to have small deletions and insertions in the same part of the preS1 gene. Immunological mapping using monoclonal anti-preS antibodies showed loss of preS epitopes located at the 3'-part of preS1 and the 5'-part of preS2. On the other hand, epitopes mapped to the 5'-part of preS1 and 3' of preS2 were conserved. PBMC were also tested and solely PCR showed the major form of defective HBV with preS1 183-bp deletion. However, viral deletions in the preS gene eliminated the preS2 promotor region and B- and T-cell recognition sites. In contrast to this, the preS1 binding site to hepatocytes was conserved. Therefore, such deletions would potentially lead to an impairment in viral clearance without affecting viral penetration in liver cells, possibly accounting for chronic HBV infection.

Emergence of and takeover by hepatitis B virus (HBV) with rearrangements in the pre-S/S and pre-C/C genes during chronic HBV infection

We have shown, by analyzing serial serum samples from a chronic hepatitis B virus (HBV) carrier, the emergence of HBV DNA molecules with nucleotide rearrangements in the pre-S/S and pre-C/C genes. Serum samples were obtained at four different times (1983, 1985, 1988, and 1989) from an HBsAg- and HBeAg-positive carrier with chronic hepatitis. The polymerase chain reaction was used to amplify the pre-S/S and pre-C/C genes. The amplified products were cloned, and 8 to 10 independent clones were sequenced. In 1983 and 1985 only one type of HBV DNA molecule was observed. Nucleotide divergence relative to the adw2 subtype was 4.7, 7.2, and 1.6%, for the pre-S1, pre-S2, and S regions, respectively, and 2.2 and 3.9% for the pre-C and C regions, respectively. In 1988 and 1989, HBV DNA forms with marked rearrangements of both the pre-S/S and pre-C/C regions were evidenced. In the pre-S/S region, they comprised two distinct HBV DNA molecules. The first showed nucleotide divergence of 20.4, 14.8, and 3.3% for the pre-S1, pre-S2, and S regions when compared with the adw2 sequence. In addition, nucleotide deletions in the pre-S1 region led to the appearance of a stop codon. The second was created by recombination between the original and mutated HBV DNA. In the pre-C/C region, the mutated viral DNA showed 11.7% divergence when compared with the adw2 sequence. A point mutation led to the creation of a stop codon in the pre-C region, together with an insertion of 36 nucleic acids in the core gene. Most of this DNA insertion was identical to that reported in an independent HBV isolate but showed no significant homology with known sequences. Semiquantitative estimation of the proportion of wild-type and mutated HBV DNA molecules showed a marked increase in the mutated forms during the period of follow-up. Sucrose gradient analysis indicated that the defective HBV DNA molecules were present in circulating virions. Western immunoblot analysis showed the appearance of modified translation products. Our findings thus indicate the emergence of and gradual takeover by mutated HBV DNA forms during the HBV chronic carrier state. The rearrangements we observed in the pre-S/S and pre-C/C genes might lead to changes in the immunogenicity of the viral particles and thus affect the clearance of the virus by the immune system.

Inhibitory activity of monoclonal antibody F35.25 on the interaction between hepatocytes (HepG2 cells) and preS1-specific ligands

The capacity of a preS1-specific monoclonal antibody (McAb) F35.25 to block the attachment of preS1-specific ligands to human hepatoma HepG2 cells was studied. In order to define more precisely the fine epitope specificity of McAb F35.25, its reaction with synthetic peptides derived from the preS1 sequence (12-53) was investigated. McAb F35.25 was found to recognize better synthetic peptide preS(21-47) from the adw 2 and ayw sequences than the synthetic peptide preS(32-53) adw 2. The shortest sequence recognized by McAb F35.25 among the peptide sequence studied was preS(32-47). The corresponding amino acid sequence (for HBV subtype adw 2) is PAFGANSNNPDWDFNP. As expected, it was found that McAb F35.25 inhibited the attachment of HepG2 cells to HBsAg-cellulose, as well as to preS(21-47)-cellulose, corresponding to two HBV subtypes adw 2 and ayw. Finally, the inhibitory effect of different peptides on the interaction of McAb F35.25 with HBsAg particles containing the preS1 sequence was also studied. The peptide preS(12-47) appeared to be the most effective inhibitor. Therefore, the McAb F35.25 is specific for the sequence preS1(X to 47), where (12 less than or equal to X less than 32). These results indicate that McAb F35.25 is probably virus-neutralizing and represents a reagent of great value to study the interaction between HBV and hepatocytes independently of d/y subtype changes.

HepG2 cell binding activities of different hepatitis B virus isolates: inhibitory effect of anti-HBs and anti-preS1(21-47)

The antigenic relationships among different hepatitis B virus (HBV) isolates were investigated by using monoclonal antibodies (MAbs) specific for HBs, preS2 (pHSA binding site), and preS1 (hepatocyte receptor-binding site) epitopes in a double immunoradiometric assay. In order to define possible functional differences resulting from structural and antigenic differences in the HBV env protein, the HBV isolates were compared in an in vitro cell-binding assay based on the attachment of 125I-labeled HBV to human hepatoma HepG2 cells. We provided evidence for a variability of the expression of preS1 and preS2 specificities in the peplomer (glyco)protein of HBV depending on dly subtype of HBsAg, which could affect the viral infectivity. We showed that the integrity of the HBV envelope structure associated with a large expression of preS1(21-47) epitopes is an essential factor for effective binding to HepG2 cells. Interestingly, the HBs-specific MAbs directed to disulfide-bond-dependent epitopes were found to be the best inhibitors of the preS1-HepG2 cell interaction (greater than 50%, at the final concentration of 0.5 micrograms/ml). The MAb F35.25 directed to the preS1(21-47) sequence corresponding to the hepatocyte receptor recognition site was, however, also found to inhibit binding. Thus, our results demonstrate the abilities of both anti-HBs and anti-preS(21-41) to block the attachment of complete HBV particles to HepG2 cells, suggesting that these antibodies should be virus neutralizing and would be expected to confer protection against reinfection.

Correlation between HBV DNA detection by polymerase chain reaction and Pre-S1 antigenemia in symptomatic and asymptomatic hepatitis B virus infections

The presence of hepatitis B virus (HBV) genome in sera from 73 symptomatic and asymptomatic HBsAg carriers was studied by the polymerase chain reaction (PCR) with primers specific for the S and C regions. Pre-S proteins of the HBV envelope were detected in serum by a specific monoclonal antibody in a double immunoradiometric assay. Out of twenty-five symptomatic patients with chronic active hepatitis (14 with HBeAg and 11 with anti-HBe), all were positive for HBV DNA by PCR, while 14/14 HBeAg and 2/11 (18%) of the anti-HBe patients were positive by dot blot hybridization. All but one anti-HBe patient (96%) carried Pre-S1 proteins. Among the asymptomatic HBsAg carriers, HBV DNA was detected by PCR in 14/14 (100%) HBeAg positive patients and in 25/34 (73%) anti-HBe positive patients. Pre-S1 proteins were found, respectively, in 14/14 (100%) and 11/22 (50%) of the same cases tested in parallel. The 20 healthy blood donors devoid of HBV markers and with normal transaminases tested were found negative for HBV DNA using PCR. Out of 12 patients who recovered from acute hepatitis B, all were found negative by PCR analysis after a mean follow up of 1 year after seroconversion to anti-HBs. When serial samples from 2 patients (one with acute hepatitis B, the other with chronic hepatitis B) were tested for the presence of HBV DNA and of Pre-S1 proteins, both markers showed parallel development.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro infection of human hepatoma (HepG2) cells with hepatitis B virus

An in vitro system for production of hepatitis B virus (HBV) was established by infection of human hepatoma (HepG2) cells. HBV particles obtained from the serum of a chronic hepatitis B surface antigen (subtype ad) carrier were used to inoculate HepG2 cells. HBV envelope and core proteins were synthesized de novo by the infected cells and secreted into the medium 3 to 6 days postinfection. Viral covalently closed circular DNA, the putative template for viral RNA transcription, accumulated in the cells with increasing time postinfection. The HBV-infected HepG2 cells were maintained for several months (HepG2-BV cell line) and continued producing viral antigens. Both HBV DNA replicative intermediates and major HBV transcripts were identified in HepG2-BV cells. Complete HBV particles, which contain HBV DNA and DNA polymerase activity and express the three antigenic specificities of the envelope (hepatitis B surface antigen, pre-S2, and pre-S1), were released into the culture supernatant. Thus, successful in vitro infection of transformed human hepatocytes raising stable HBV-producing cells was achieved for the first time. This strongly suggests that HepG2 cells have a receptor(s) for virus attachment and penetration. Such a system represents a significant advance for the study of HBV-target cell interactions as the early events of HBV infection.

Variable expression of preS1 antigen in serum during chronic hepatitis B virus infection: an accurate marker for the level of hepatitis B virus replication

The expression of the preS1 antigen of hepatitis B virus in sera from chronic HBsAg carriers was studied using a specific monoclonal antibody F35.25 in an original, double-immunoradiometric assay. The antibody F35.25 recognized an epitope located between amino-acid residues 32 and 53 on the preS1 sequence of the large HBsAg protein. This domain could be involved in the recognition of hepatitis B virus by hepatocyte receptors. PreS1 antigen detection by monoclonal antibody F35.25 closely correlated with the presence of complete virions in the serum of HBsAg carriers, as demonstrated by ultracentrifugation-gradient experiments and electron-microscopical examination. Of the 19 HBsAg carriers with chronic liver disease, preS1 antigen was detected in 17 (90%): all of the 11 HBeAg- and hepatitis B virus-DNA--positive cases (group 1) and six of eight anti-HBe--positive cases with low levels of hepatitis B virus replication (group 2). PreS1 antigen/HBsAg ratios parallel to preS1 antigen titers were significantly higher in the HBeAg-positive group (34% and 1:10(6] than in the anti-HBe--positive group (18% and 1:10(2]. In contrast, preS1 antigen was not detected in 18 (90%) of the 20 HBsAg healthy carriers positive for anti-HBe and negative for serum hepatitis B virus-DNA (group 3). Our results show that in chronic HBsAg carriers the serum expression of preS1 antigen correlates well with the level of hepatitis B virus replication (serum hepatitis B virus-DNA and/or liver HBcAg) and that it may be useful in assessing the clinical importance of the chronic viral infection.

A monoclonal antibody specific for the hepatocyte receptor binding site on hepatitis B virus

The sequence of the preS1 region of the hepatitis B virus (HBV) envelope (env) proteins contains a dominant binding site for hepatocytes between residues preS21 and preS47. Purified HBV particles (subtype ad) were used as the immunogen to produce specific monoclonal antibodies (McAbs) against three antigenic regions (S, preS2 and preS1) of the HBV env protein. One McAb, F35.25, was found to be specific for the region 32-53 of the preS1 sequence of HBV, which largely overlapped the hepatocyte receptor binding site. The preS1-specific McAb F35.25 reacted with both HBV subtypes, ad and ay, in radioimmunoassays (RIA) and with the large surface proteins, P39 and GP42, as well as with tryptic fragments preS(1-99/103) and preS(1-113) in Western blotting experiments. This McAb F35.25 preferentially recognized, however, the homologous (ad) preS1 sequence in RIA. The ad/ay amino acid substitution within the hepatocyte receptor binding site at position 35 (Gly-Arg) may explain the relative subtype-specificity of F35.25. Finally, the F35.25 epitope was detected in all HBV particles purified from HBeAg-positive human sera, confirming that this preS1 region 32-53 is exposed at the surface of complete virions. Thus, we developed a RIA system allowing us to assess the infectivity of HBV particles by the detection of preS1 sequences associated with the viral hepatocyte receptor. Moreover, it is expected that F35.25 may be a virus-neutralizing antibody by blockage of the attachment of HBV to liver cells.

Antigenic mapping of the surface proteins of infectious hepatitis B virus particles

To identify further the surface proteins of the native virus, hepatitis B virus (HBV) particles purified from HBe antigen (Ag)-positive human sera were used as immunogens to produce murine monoclonal antibody (MAb)-secreting hybridomas. The specific binding of antibodies to the HBV envelope (env) proteins was determined in indirect radioimmunoassay and by Western blot analysis. Six MAbs directed against major hepatitis B surface antigen (HBsAg) recognized conformational epitopes on S proteins (P24s/GP27s). Three preS2-specific MAbs reacted with the middle env proteins (GP33s/GP36s) in the 22 nm HBsAg spherical particles. One MAb, F222, was found to react specifically with the two very large (VL) HBV surface proteins with Mr 54K and 66K. The epitope recognized by F222 was located on the protruding N terminus which, in the assembled virus particles, was readily split off by trypsin or V8 protease treatment. The presence of these VL proteins appeared to correspond to the presence of the large env proteins (P39s/GP42s). The data described here indicate that F222 probably recognized an assembled topographic site which could be involved in virus entry into hepatocytes. Moreover, our results suggest that the preS-coded part of the HBV env proteins, which is sensitive to proteases in vitro, could be unstable in vivo and stabilized by immunoglobulins.

Immunochemical structure of the hepatitis B surface antigen vaccine--II. Analysis of antibody responses in human sera against the envelope proteins

Antibody responses to the three envelope (env) proteins of hepatitis B viral particles (HB-VP): the S-encoded P25 polypeptide; the pre-S(2)- and S-encoded GP33/GP36 polypeptide; and the large entire env gene (pre-S + S) product, P39/GP42, were investigated using a Western immunoblotting assay (WIBA). HB-VP proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and transferred to nitrocellulose by electroblotting were used as antigenic probes to determine the polypeptide specificity of these antibodies present in immune individuals. Antisera from human subjects either after a natural HBV infection or after active immunization with the hepatitis B vaccine licensed in France were selected on the basis of a positive serological RIA test for antibodies against hepatitis B surface antigen (HBsAg). In all studied cases, the lack of reactivity of the anti-HBs/P25 antibodies in blots from reduced SDS gels confirms that the S-related-determinants have a conformation sensitive to denaturing agents. In contrast, the anti-pre-S(2)/GP33-GP36 antibodies and the anti-pre-S(1)/P39-GP42 antibodies can be easily detected in WIBA, providing these antibodies recognize the disulfide-bond independent pre-S determinants on the denatured env proteins. However, antisera raised in guinea-pigs against individual HBsAg polypeptides contain antibodies reacting with denatured S-proteins, suggesting that the sequential S-determinants are lost during HBV morphogenesis. Antibody responses in HBV convalescing patients or vaccinated healthy donors are shown to be characterized by: an early transient polypeptide specific-antibody response to pre-S(2)-sequences (detected in WIBA); a persistent antibody response to conformation-dependent S-determinants (detected in RIA). This implies that effective long-term protection against HBV infection requires antibodies directed to native env proteins.

Hepatitis B virus pre-S gene-encoded antigenic specificity and anti-pre-S antibody: relationship between anti-pre-S response and recovery

A solid-phase radioimmunoassay involving specific antibody was developed for determination of the pre-S gene-encoded epitopes of hepatitis B virus and anti-pre-S antibody in sera of hepatitis B patients. The reaction for pre-S determinants associated with HBsAg was quantitatively inhibited by soluble, polymerized human serum albumin, and the lower limit of the assay was about 1.6 ng of HBsAg per ml. Continuous expression of pre-S-coded antigenic sites on HBsAg particles in chronic hepatitis B patients seropositive for HBeAg or anti-HBe shows that these determinants may be considered as a marker of chronicity during hepatitis B virus infection. The anti-pre-S antibody was determined by inhibition of the reaction for pre-S determinants. This antibody, different from anti-HBs, was detected during HBsAg antigenemia in patients recovering from acute type B hepatitis, before anti-HBs response. Kinetics of synthesis of anti-pre-S antibody in the course of acute type B hepatitis, followed by elimination of HBsAg and recovery, suggest the possible role of this antibody in the immunological clearance of infective hepatitis B virus particles.

Demonstration of a firm association between hepatitis B surface antigen proteins bearing polymerized human albumin binding sites and core-specific determinants in serum hepatitis B viral particles

Hepatitis B viral particles (HB-VP) were purified from sera of chronic hepatitis B surface antigen (HBsAg) positive carriers by consecutive isopycnic and rate-zonal sedimentation in sucrose gradients. Their immunological properties [HBsAg, hepatitis B core antigen (HBcAg) and hepatitis B e-antigen (HBeAg) activities] were examined by a radioimmunoassay based upon the classical "sandwich principle". A double antibody specificity radioimmunoassay (DAS-RIA) was then developed to determine whether envelope proteins (HBsAg) with binding activity for polymerized human serum albumin (pHSA-BA) were associated with core-specific antigenicities (HBc/HBeAg). An e-antigen activity cosedimenting with intact HB-VP (negative for HBcAg reactivity) was detected in association with HBsAg and receptors for pHSA. The presence of HBcAg-specific determinant(s) on HBeAg molecules was also indicated by DAS-RIA. So, we postulated that such hepatitis B virion (HBV) specific molecules are involved in immune complexes with anti-HBc as antibodies in sera of patients with chronic HBV infection. To define the significance of these molecular forms in HB-VP morphogenesis, we studied the effects of a mild treatment with a chaotropic salt, NaSCN, on HB-VP-rich fractions (DNA polymerase positive). A small mol. wt HBeAg derived from HB-VP by dissociating treatment was detected. We found that core-specific determinants (HBe/HBcAg) were bound to large surface proteins (HBsAg) with pHSA-BA and therefore probably contained the pre-S sequence. The selective release from HB-VP of such molecular forms, which could be a product of the major S-region transcript, suggests that they may be components of complete virions.

[Presence of macromolecular HBe antigen linked to HBs antigen with masked epitopes in the serum of patients actively reproducing hepatitis B virus]

At the onset of hepatitis B and more generally in some other types of this infection implying active replication of hepatitis B virus, HBe Ag is detected in the serum as macromolecular complexes with more or less masked epitopes. At the same time, HBe Ag appears bound to HBs Ag as shown by a radioimmunological assay on solid phase, implying anti-HBs and anti-HBe specificities in the same test.