Effects of wheat bran in comparison to antibiotics on growth performance, intestinal immunity, barrier function, and microbial composition in broiler chickens

This experiment was conducted to evaluate the effects of wheat bran (WB) and antibiotics on growth performance, intestinal immunity, barrier function, and microbial composition in broiler chickens. A total of 168 one-day-old male Arbor Acre chicks were allocated to 3 treatments consisting of 7 replicates with 8 birds per replicate. The 3 treatments were: an antibiotic-free control diet (control, CON), CON + 75 mg/kg chlortetracycline as an antibiotic growth promoter (AGP), and CON + 3% WB. Birds fed AGP and WB had greater (P < 0.05) ADG during days 1 to 21 and lower (P < 0.05) feed-to-gain ratio during each phase than those fed CON. The WB supplementation reduced (P < 0.05) serum concentrations of tumor necrosis factor-α and diamine oxidase activity compared with CON on both day 21 and 42. The AGP and WB supplementation decreased (P < 0.05) interleukin-1β concentration in jejunal mucosa on day 21 and increased (P < 0.05) secretory immunoglobulin A concentration in jejunal mucosa on day 21 and 42. The relative expression of occludin in jejunal mucosa was upregulated (P < 0.05) in WB than in CON on day 21. Moreover, both AGP and WB supplementation upregulated (P < 0.05) the relative expression of zonula occludens-1 in jejunal mucosa on day 21 and 42. The WB supplementation enhanced the α-diversity of cecal microbiota, as evidenced by the increased Shannon index (P < 0.05). At the phylum level, the phylum Firmicutes was enriched (P < 0.05) in WB. At the genus level, the WB supplementation enriched (P < 0.05) Lachnoclostridium and Butyricicoccus. The WB supplementation increased (P < 0.05) cecal total short chain fatty acids concentrations on day 21 and 42, and butyric acid concentrations on day 42 compared with CON. Collectively, supplementation of 3% WB could promote growth by improving intestinal immunity, barrier function, and microbial composition in broilers. Thus, WB may have a role in replacing antibiotics for improved growth performance and intestinal health in broilers.

Weeping forsythia extract alleviates dexamethasone-induced oxidative injury of breast muscles in broilers

Antioxidants have been always used to improve post-slaughter meat quality in broilers subjected to stress. Forsythia suspensa extract (FSE), a traditional Chinese herbal medicine, is generally regarded as a natural source of antioxidants. Therefore, the objective of this study was to test the hypothesis that FSE could protect post-slaughter breast muscles against oxidative injury induced by dexamethasone (DEX) mimicking chronic physiological stress in poultry production. Average daily gain and feed efficiency of poultry were suppressed by DEX and improved by FSE (P < 0.05). Dexamethasone caused the decrease in the redness value and the increase in the lightness and yellowness values and drip loss of the breast muscles (P < 0.05), and FSE had the converse effects (P < 0.05). Dietary FSE supplementation decreased monounsaturated fatty acid (FA) and increased polyunsaturated FA in breast muscles of broilers (P < 0.05). In addition, FSE decreased malondialdehyde and carbonyl content in the breast muscles of DEX-treated broilers (P < 0.05). The inhibition of 1,1-diphenyl-2-picryl-hydrazyl in the breast muscles was decreased by DEX and increased by FSE (P < 0.05). Total-antioxidant capacity and glutathione peroxidase activity in the breast muscles were decreased in birds subjected to DEX and increased in birds supplemented with FSE (P < 0.05). Totally, DEX suppressed growth performance and induced breast muscle oxidative injury in broilers, and FSE supplementation improved antioxidant capacity to attenuate these adverse effects. Therefore, FSE could be a potential natural antioxidant to alleviate oxidative injury of the breast muscles in broilers and to improve the meat quality for human consumption.

[Expression patterns and prognostic values of Nrf2 and Keap1 in nasopharyngeal carcinoma]

Objective:To investigate the expression of Nrf2 and Keap1 in nasopharyngeal carcinoma (NPC) and to analyze the relationship between the expression of Nrf2 and Keap1 and the clinicopathological features and prognosis of patients with nasopharyngeal carcinoma. Method:A total of 108 patients with biopsy-proven nonkeratinizing squamous cell carcinoma-undifferentiated type with available biopsy specimens for tissue microarray (TMA) construction were selected. The relationship between Nrf2 and Keap1 protein expression and the prognosis of radiotherapy in patients with nasopharyngeal carcinoma was analyzed. Result: The overall 5-year disease free survival (DFS) and overall survival(OS) rates were 57.4% and 70.2%, respectively. The 5-year DFS rate was 59.4% in the low nuclear Nrf2 expression group, and 53.8% in the high nuclear Nrf2 expression group. The 5-year DFS rate was 42.2% in the low cytoplasmic Keap1 expression group, and 68.2% in the high cytoplasmic Keap1 expression group. The 5-year OS rate was 70.8% in the low nuclear Nrf2 expression group, and 69.2% in the high nuclear Nrf2 expression group. The 5-year OS rate was 55.6% in the low cytoplasmic Keap1 expression group, and 80.9% in the high cytoplasmic Keap1 expression group.Conclusion:We found that nuclear Nrf2 or cytoplasmic Keap1 expression had no significant association with clinicopathological features. The high expression of cytoplasmic Keap1 had higher DFS and OS. Keap1 is an independent prognostic factor for DFS and OS in NPC patient.

[Analysis of allergen spectrum and sensitization factors in children with allergic rhinitis]

Objective:The aim of this study is to analyze the distribution of common allergens in allergic rhinitis patients aged 2-15 in Zhangjiagang area,in order to provide a path to know the epidemic features of children with AR, and supports epidemiological materials to find better prevention, diagnosis and treatment for them.Method:From July.2015 to July.2018,1 320 children aged 2-15 who were suspected with allergic rhinitis by the doctors of ENT clinic in the Zhangjiagang Affiliated Hospital,were enrolled in this project.Using the serum specific IgE detection methods to detect common allergens in those patients,then analyze the relationship among allergens and gender,age and visiting time of every single patient.Result:The total positive rate of 1 320 children was 82.50%,and the total positive rate of 8 common inhaled allergens was 82.50%.The main allergens were dust mites and dogs. The total positive rate of Children aged in 7-12 was the highest,and the positive rate of dust mites of male was higher than female.The common food allergens total positive rate was 9.09%.And the top three food allergens were milk,shrimp,crab.The number of visitors in July and August was the most in a year.The dust mite had the highest positive rate among common inhaled allergen in a year,and the maximum value appeared in July.The rate of patients who were allergic to one inhalant allergen were lower than those who were allergic to two or more inhalant allergens.Conclusion:The dust mite is the major allergen above all.The total positive rate of Children aged in 7-12 was the highest,and the positive rate of dust mites of male was higher than female;the maximum value appeared in July and August.The rate of patients who were allergic to one inhalant allergen were lower than those who were allergic to two or more inhalant allergens.

Forsythia suspensa extract protects broilers against breast muscle oxidative injury induced by corticosterone mimicked pre-slaughter acute stress

Broilers were used to determine the protective effects of Forsythia suspensa extract (FSE) against breast muscle oxidative injury induced by corticosterone (CS) mimicking pre-slaughter acute stress. A total of 144 male Arbor Acre broilers was randomly allotted to one of 4 treatments in a 2 × 2 factorial arrangement that included FSE supplementation (0 or 100 mg/kg) and subcutaneous injection of CS (0 or 4 mg/kg) at 3 h before slaughter. Corticosterone increased live BW loss, and the adverse effect was attenuated by FSE in broilers subjected to CS (P < 0.05). Serum levels of CS, uric acid, and glucose were increased, and postmortem breast muscle pH values at 45 min and 24 h were decreased for CS-challenged broilers (P < 0.05). Corticosterone increased lightness and yellowness values and decreased redness of breast muscle (P < 0.05), and FSE decreased yellowness and increased redness of breast muscle (P < 0.05). Drip loss was increased by CS for birds supplemented without FSE (P < 0.05) and decreased by FSE for birds under CS challenge (P < 0.05). Corticosterone increased monounsaturated fatty acid (FA) and decreased polyunsaturated FA in breast muscle (P < 0.05), and saturated FA was decreased and polyunsaturated FA was increased by FSE (P < 0.05). Malondialdehyde and carbonyl contents in breast muscle were increased by CS and decreased by FSE (P < 0.05). Inhibition of 1,1-diphenyl-2-picryl-hydrazyl was decreased by CS and increased by FSE (P < 0.05). The activities of total-antioxidant capacity, glutathione peroxidase, and superoxide dismutase in breast muscle were lower in birds subjected to CS (P < 0.05) and were greater in birds supplemented with FSE (P < 0.05). Collectively, live BW loss and breast muscle oxidative injury were increased by CS in broilers, and these stress-related adverse effects could be attenuated by FSE supplementation via enhanced scavenging ability of free radicals and antioxidant capacity. Therefore, FSE could protect broilers against breast muscle oxidative injury when acute stress happens.

Chemical composition, energy, and amino acid digestibility in 7 cottonseed co-products fed to growing pigs

The objective of this study was to determine the chemical composition, DE and ME contents, and apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of AA in 7 cottonseed co-products fed to growing pigs. The 7 cottonseed co-products were: cottonseed meals (solvent extracted) with CP level of 46%, 50%, and 55% (46CSM, 50CSM, and 55CSM), cottonseed protein with CP level of 50% and 55% (50CSP and 55CSP), fermented cottonseed meal (CSMF), and expelled cottonseed meal (CSME). The DE and ME contents of the 7 test ingredients were measured using 48 crossbreed barrows (BW: 44.1 ± 4.2 kg) and 8 diets (including a corn-soybean meal basal diet) in a completely randomized design. The AID and SID of AA of the 7 test ingredients were determined using 7 crossbreed barrows (initial BW: 67.4 ± 8.5 kg) in a 6 × 8 Youden square design with 6 periods and 8 diets (including one N-free diet). The DE and ME values of the 7 cottonseed co-products varied from 12.72 to 15.63 MJ/kg and 12.24 to 14.83 MJ/kg, respectively. Among the 7 cottonseed co-products, 55CSP and CSME had the greatest (P < 0.05) ME and DE values compared to the other cottonseed co-products. In addition, 55CSP had the greatest (P < 0.05) AID and SID of all the AA tested except for Gly and Pro. In contrast, 46CSM or 55CSM had the lowest (P < 0.05) AID and SID of all the AA tested except for Gly and Pro. The 55CSP also had the greatest (P < 0.05) concentrations of standardized ileal digestible CP and all the AA tested except for Gly and Pro. In conclusion, the chemical composition, energy, and AA digestibility of cottonseed co-products with different processing techniques varied widely. Based on the energy and AA digestibility, cottonseed protein with CP level of 55% is a better dietary ingredient for growing pigs compared with the other cottonseed co-products.

Probiotic supplementation protects weaned pigs against enterotoxigenic Escherichia coli K88 challenge and improves performance similar to antibiotics

These studies evaluated the effects of probiotics (PB) as a potential substitute for antibiotics (AB) on diarrhea in relation to immune responses and intestinal health in weaned pigs challenged with enterotoxigenic (ETEC) K88 (Exp. 1) and the effects of PB on performance and nutrient digestibility in weaned pigs (Exp. 2). In Exp. 1, 24 weaned barrows (4.9 ± 0.4 kg initial BW) were randomly assigned to 1 of 4 treatments. The treatments consisted of pigs fed an unsupplemented corn-soybean meal basal diet and not challenged (NON-C) or challenged with ETEC K88 (CHA-C) on d 9 and pigs fed the same basal diet supplemented with AB (100 mg/kg zinc bacitracin, 50 mg/kg colistin sulfate, and 100 mg/kg olaquindox; CHA-AB) or 500 mg/kg PB ( and ; CHA-PB) and challenged with ETEC K88 on d 9. In Exp. 2, 108 weaned pigs (7.5 ± 0.9 kg initial BW) not challenged with ETEC K88 were randomly assigned to 1 of 3 treatments, including an AB-free basal diet (CON) and the basal diet with AB (ABD) or 500 mg/kg PB supplementation (PBD). In Exp. 1, after challenge, CHA-C decreased ( < 0.05) ADG and ADFI, whereas CHA-AB and CHA-PB revealed no significant change compared with NON-C. Compared with CHA-C, CHA-AB and CHA-PB improved ( < 0.05) ADG and ADFI and decreased ( < 0.05) the diarrhea incidence in pigs. Mucosal secretory Ig A contents in the jejunum and ileum were greater in CHA-C than in NON-C ( < 0.05) and lower than in CHA-PB ( < 0.05). The diet containing PB alleviated the increase in the endotoxin and diamine oxidase concentration and cecal count ( < 0.05) and the decrease in intestinal villus height, cecal count, and jejunal mucosal occludin protein abundance ( < 0.05). In Exp. 2, dietary supplementation with AB and PB had positive effects on ADG and feed efficiency ( < 0.05). Compared with CON, apparent digestibility of nutrients in PBD was improved ( < 0.05). Collectively, PB supplementation protected the pigs against ETEC K88 infection by enhancing immune responses and attenuating intestinal damage and improved the performance and nutrient digestibility of weaned pigs. Therefore, PB could be a potential effective alternative to AB for ameliorating diarrhea and improving performance in weaned pigs.

Concentration of digestible and metabolizable energy, standardized ileal digestibility, and growth performance of pigs fed diets containing sorghum produced in the United States or corn produced in China

The DE and ME content (Exp. 1) as well as the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of essential AA (EAA; Exp. 2) were compared between Chinese corn and U.S. sorghum. The effects of U.S. sorghum as a potential substitute for Chinese corn on growth performance of 114 weaned pigs (8.8 ± 1.0 kg BW; Exp. 3) and 60 growing pigs (23.4 ± 1.6 kg BW; Exp. 4) were evaluated, and the effect of protease supplementation on N utilization was determined in sorghum-based diets fed to growing pigs (Exp. 4). In Exp. 1, there was no difference in DE and ME content between corn and sorghum. In Exp. 2, the AID and SID of most EAA and the concentrations of standardized ileal digestible Lys, Met, Thr, and His were less in sorghum than in corn ( < 0.05). In Exp. 3, there was no difference in ADG and ADFI among treatments during the experimental period. The G:F and apparent total tract digestibility (ATTD) of CP was decreased for pigs fed diets with sorghum in the first 2 wk ( < 0.05) and for pigs fed diets containing 60% sorghum in the following 2 wk ( < 0.05). The fecal score for pigs fed diets with sorghum, regardless of the substitute level, was less ( < 0.05) or tended to be less ( = 0.086) than that for pigs fed diets containing 60% corn. In Exp. 4, no differences were observed in ADG and ADFI overall among pigs fed diets based on corn and soybean meal (CSBM) or sorghum and soybean meal (SSBM). Pigs fed CSBM or SSBM with protease supplementation had greater ( < 0.05) or tended to have greater ( = 0.062) G:F than pigs fed SSBM. Compared with CSBM, SSBM increased fecal N excretion by more than 25% and decreased the ATTD of CP by more than 7% during the whole experiment ( < 0.05). Protease supplementation reduced fecal N excretion by more than 12% and increased ATTD of CP by more than 6% ( < 0.05). In conclusion, based on optimal G:F and CP digestibility, diets for weaned pigs should contain less than 20% sorghum during the first 2 wk and no more than 40% during the subsequent 2 wk after weaning. Sorghum used as an alternative energy source for corn in diets fed to growing pigs decreases CP utilization by increasing manure N output, which might be partially offset by protease supplementation.

Effect of different inclusion level of condensed distillers solubles ratios and oil content on amino Acid digestibility of corn distillers dried grains with solubles in growing pigs

The purpose of this experiment was to determine and compare the digestibility of crude protein (CP) and amino acids (AA) in full-oil (no oil extracted) and de-oiled (oil extracted) corn distillers dried grains with solubles (DDGS) with different condensed distillers solubles (CDS) ratios. Six barrows (29.6±2.3 kg) fitted with ileal T-cannula were allotted into a 6×6 Latin square design. Each period was comprised of a 5-d adaption period followed by a 2-d collection of ileal digesta. The five test diets contained 62% DDGS as the sole source of AA. A nitrogen-free diet was used to measure the basal endogenous losses of CP and AA. Chromic oxide (0.3%) was used as an index in each diet. The results showed that CP and AA were very similar in 5 DDGS, but the standardized ileal digestibility (SID) of lysine (from 56.16% to 71.15%) and tryptophan (from 54.90% to 68.38%) had the lowest values and largest variation within the essential AA, which suggests reduced availability of AA and different levels of Maillard reactions in the five DDGS. The apparent ileal digestibility and SID of CP and most of AA in full-oil DDGS (sources 1 and 2) were greater (p<0.05) than de-oiled DDGS (sources 3, 4, and 5). Comparing the AA SID in the 5 DDGS, full-oil with low CDS ratio DDGS (source 1) had non-significantly higher values (p >0.05) than full-oil with high CDS ratio DDGS (source 2); however, the SID of most AA of de-oiled with low CDS ratios DDGS (source 3) were non-significantly lower (p>0.05) than de-oiled with high CDS ratio DDGS (source 4); and the de-oiled DDGS with middle CDS ratio (source 5) but with different drying processing had the lowest SID AA values. In conclusion, de-oiled DDGS had lower SID of CP and AA than full-oil DDGS; a higher CDS ratio tended to decrease the SID of AA in full-oil DDGS but not in de-oiled DDGS; and compared with CDS ratio, processing, especially drying, may have more of an effect on AA digestibility of DDGS.

Cloning and expression analysis of murine lupin, a member of a novel gene family that is conserved through evolution and associated with Lupus inclusions

We describe here the first full-length sequence of a member of a novel gene family encoding a protein in the mouse that we call Lupin. Lupin is homologous to a human protein previously called p36, which was purified from alpha-interferon-treated cells that formed lupus inclusions. Lupus inclusions are dense intracellular deposits found in endothelial cells and lymphocytes of patients with systemic lupus erythematosis and AIDS. Proteins closely related to Lupin exist in evolutionarily divergent species including Caenorhabditis elegans, Drosophila and zebrafish. At least one other lupin-related gene is expressed in the mouse and in man. Lupin is expressed in mouse embryos and adults, notably in liver, spleen, central nervous system, multiple epithelia and all types of muscle. In skeletal muscle, expression analysis suggests that Lupin associates with the contractile apparatus.

Thioredoxin fusion/HIV-1 protease coexpression system for production of soluble human IL6 in E. coli cytoplasm

In this paper, thioredoxin (TRX) fusion expression system has been modified to produce soluble human IL6 (hIL6) without TRX moiety in E. coli cytoplasm. A novel TRX gene fusion vector was developed that contained at the 3'-end of TRX gene a short DNA sequences encoding a linker peptide '-GSGSGVSQNYPIVQHHHHHH-', serving not only as a specific HIV-1 protease site but also providing six contiguous histidine (His) residues to foreign proteins. The cDNA for hIL6 was cloned into this vector resulting in plasmid pTRX@HISIL6. The cDNA for the HIV-1 protease has been cloned into another compatible plasmid pHMM2, resulting in plasmid pHMM2-PR. Both plasmids were transformed into E. coli strain GI724, and when induced for expression of both proteins, the correct processing of TRX@HISIL6 was obtained, producing hIL6 with His6-tag at the N terminus named HISIL6. A fraction of HISIL6 was found in soluble form and could be purified to homogeneity by Ni-NTA Superflow and ion-exchange chromatography. The biological activity of purified HISIL6 was measured by MTT method in an IL-6-dependent cell line 7TD1 to be 2.1 x 10(8) unit/mg.

Molecular cloning and expression of human interleukin-6 in insect cells

670-bp hIL-6 cDNA fragments have been amplified by polymerase chain reaction (PCR) using recombinant plasmid pBMIL-6A as templates and two synthetic oligonucleotides containing the optimized translation initiation sequence and restriction sites suitable for cloning as primers. The amplified IL-6 cDNA fragments have then been recombined with a non-fusion expression baculovirus vector pVL1393. The resultant recombinant plasmid pVL. IL-6 together with wtAcMNPV DNAs were transferred into cultured lepidopteran insect cells (Sf9) by calcium phosphate coprecipitation procedure. The recombinant baculoviruses were formed by homologous recombination in vivo between pVL. IL-6 and wtAcMNPV DNAs, screened for plaque assay, and identified by means of dot blotting hybridization. The expressed rhIL-6 was secreted into the culture medium, and its bioactivity was measured through half-maximum H-TdR incorporation into IL-6-dependent cells 7TD1. As a result, the supernatant collected from recombinant baculovirus rAc. IL-6-infected Sf9 cells showed IL-6 activity of 10(6) U/mL. The expression level of rhIL-6 of the supernatant determined by IL-6 ELISA quantitation kit was 1 microgram/mL.

A study of primary- and re-infection with hepatitis C virus in blood transfusion recipients

A nested polymerase chain reaction was used to assess viraemia in blood transfusion recipients with no serological evidence of hepatitis C virus (HCV) infection (naive recipients) and in recipients with prior or existing HCV infection (infected recipients), who were transfused with HCV-positive blood. In 10 hepatitis cases in naive recipients, defined as primary infection, nine showed clinical hepatitis, and one was sub-clinical; the time between transfusion and elevation of alanine aminotransferase (ALT) levels was 15-60 days (37.9 +/- 13.9). All 10 naive recipients showed abnormal ALT, and 10/10 and 7/10 were persistently positive for anti-HCV and HCV-RNA, respectively, for more than 1 year. Similarly, in five cases in previously infected recipients, defined as re-infection, 4/5 showed clinical hepatitis, the time to elevation of ALT was 30-46 days (34.8 +/- 6.4), and 5/5 and 3/5 were persistently positive for anti-HCV and HCV-RNA, respectively, for more than 1 year. All five infected recipients showed abnormal ALT. In conclusion, there was no significant difference (P = 0.05) in the frequency of the markers of infection resulting from primary or re-infection with HCV, suggesting that primary infection fails to induce a protective immune response.

[Use of baculovector for the expression of HBsAg gene in insect cells]

Based on the information of molecular biology of Autographa californica Nuclear Polyhedrosis virus (AcNPV), a recombinant transfer plasmid pAcMV was constructed by molecular procedures included using two synthetic localized probes, which provided an inserted position linked with BamHI sequences nearly at polyhedrin initiating ATG codon. Then an expression vector pAcMV-HBsAg was reconstructed, it contained HBsAg gene from subclone pYPSS-1 derived from adwserotype of HBV. The recombinant virus containing HBsAg gene was isolated and purified through 3 cycles plaques and hybridization experiment after cotransfection of Spodoptera frugiperda cells with DNA of pAcMV-HBsAg and AcNPV. The expression of HBsAg gene in S. frugiperda cells infected with recombinant virus AcRV-HBsAg was identified by ELISA as haemagglutination tests. The yield of HBsAg excreted from S. frugiperda cells (an appropriate density usually between 1-2 X 10(6) cells/ml) after 48-72 h infected with AcRV-HBsAg was 4-8 mg/L. HBsAg harvested from the infected culture medium was shown immunoelectromicroscopy to be composed of spherical particles of about 22 nm diameter. Using this purified HBsAg, Bal b/c mice was immunized, the titer of anti-HBsAg serum measured measured by RIA was similar to that of purified HBsAg from human blood. Stable recombinant virus was isolated and could be shown to replicate in corn borer (Ostrinia nubilalis) larvae. All of these results can be expected that this expression vector system will be commercially developed to its fullest potential for diagnosis and vaccine HBsAg.

Structure in the precore region of hepatitis B core gene affecting its expression in E. coli

Restriction fragments of HBV-DNA, cleaved by endonuclease HhaI, containing HBcAg gene were trimmed by BAL-31 exonuclease to remove different lengths of the precore sequence. They were inserted into plasmid pUR222 at EcoRI site through synthetic linker ligation. Transformants in E. coli BMH7118 showing different levels of HBcAg gene expression were screened and analyzed for their nucleotide sequences in the junction region both by Maxam and Gilbert's chemical degradation method and by M13 chain termination method. Results of sequence analysis of different transformants revealed a partial palindromic (loop and stem) structure, at -7 to -35 nucleotide with regard to ATG of the HBcAg gene as position +1, which has dramatic effect on the level of expression of the inserted gene using the same promoter, SD sequence and identical N-terminus. The amount of HBcAg synthesized differed from 9% in the high expressing plasmid to less than 0.01% of the total cell proteins in the low expressing transformants. The findings were compared to results obtained by other workers in studies of HBcAg expression in procaryotes and their significance in the expression of eucaryotic genes in procaryotic cells were discussed.

The effect of upstream sequences to initiator on the expression of gene coding for hepatitis B core antigen

The nucleotide sequences of cloned adw hepatitis B core antigens (HBcAg) which have different levels of expression have been determined by dideoxy chain-terminating method. The results indicate that the different levels of gene expression is primarily due to the different structures of upstream sequences before the initiator of HBcAg genes. The hepatitis B core gene in the low-expressed clone forms a secondary structure before the initiator. This secondary structure has been removed by Bal-31 exonuclease in the high-expressed clone and half of the structure removed in the mid-expressed clone. It is apparent that the transcription/translation of the hepatitis B core gene is somehow blocked because of the secondary structure. Therefore, the amount of HBcAg synthesized in E. coli is dramatically reduced.