Development of a candidate influenza vaccine based on virus-like particles displaying influenza M2e peptide into the immunodominant loop region of hepatitis B core antigen: Insertion of multiple copies of M2e increases immunogenicity and protective efficiency

The extracellular domain of the transmembrane protein M2 (M2e) of influenza A virus is a promising target for the development of “universal” vaccines against influenza. M2e is a poor immunogen by itself; however, when M2e is linked to an appropriate carrier, such as hepatitis B virus core (HBc) particles, it becomes highly immunogenic. Insertions of target peptides into the surface-exposed major immunodominant loop region (MIR) of the HBc antigen are especially immunogenic, but such insertions often affect the protein folding and formation of recombinant virus-like particles. To facilitate an appropriate conformation of the M2e insert, we introduced flexible linkers at the junction points between the insert and flanking HBc sequences. This approach allowed the construction of recombinant HBc particles carrying 1, 2 and 4 copies of M2e in the MIR region. These particles were produced in Escherichia coli and purified to homogeneity. The immune response and protective activity of hybrid HBc particles in mice correlated with the number of inserted M2e peptides: the highest immunogenicity and complete protection of mice against the lethal challenge by influenza virus was observed with particles carrying four copies of M2e. The possibility of the simultaneous presentation of M2e peptides from several important influenza strains on a single HBc particle could also facilitate the development of a broad-specificity vaccine efficient not only against influenza A strains of human origin but also for newly emerging strains of animal origin, such as the avian influenza.     

Inhibition effect produced by dominant negative mutant fusion protein PreS2-TLM-ScFv-HBcDN on HBV replication in vitro

A mammalian expression vector comprised of the PreS2-TLM (translocation motif), a single-chain variable fragment (ScFv) that binds to hepatitis B surface antigen (HBsAg) and the EGFP gene was constructed. A stably transformed cell line that could express and secrete the fusion protein (PreS2-TLM-ScFv-EGFP) was established. HBsAg-positive HepG2.2.15 cells and HepG2 and HeLa cells were incubated with the supernatant of the transformed cell line cultures for evaluating the cellular permeability of PreS2-TLM-ScFv-EGFP. The location of the fusion protein PreS2-TLM-ScFv-EGFP in HepG2.2.15 cells was observed with immunofluorescence staining. EGFP was next replaced by a dominant negative mutant of the hepatitis B virus core gene (HBcDN) for producing fusion protein PreS2-TLM-ScFv-HBcDN, which was detected by western blot. The supernatant containing fusion protein PreS2-TLM-ScFv-HBcDN was added to the cultures of HepG2.2.15 cells, and the packaged hepatitis B virus (HBV) pregenomic RNA expression levels in the cells were measured using qRT-PCR. The results of the in vitro study indicated that the packaged HBV pregenomic RNA expression levels in HepG2.2.15 cells significantly decreased when these cells were exposed to the supernatant at the dose of 25% for 24, 48 and 72 h, or at the dose of 12.5% for 72 h.     

Isolated serum hepatitis B core antibody seropositivity: A diagnostic risk factor for occult hepatitis B infection

Anti‐HBc screening and nucleic acid testing for hepatitis B viral DNA (HBV DNA) detection in blood donors are not routinely performed in clinical settings in Nigeria. This raises serious concerns for safety of blood at a time that global health standards advocate for transfusion safety. The aim of this research is to investigate if presence of anti‐HBc in blood donors is actually associated with occult hepatitis B infection through basic and advanced procedures. Prospective blood donors who were seronegative for HBsAg but sero‐positive for anti‐HBc (with or without other markers) among the four hundred and seventy enrolled in a cross‐sectional study were selected for this study. Samples were further screened for hepatitis B core immunoglobulin M by enzyme‐linked immunosorbent assay. Nucleic acid testing was performed for confirmation of occult hepatitis B infection. Anti‐HBc was detected in 20 (32.8%) of the sixty‐one HBsAg antigen‐negative blood donors which constituted 13.0% of the total number of enrolled blood donors. Anti‐HBc total‐positive differentiation showed eighteen (90.0%) anti‐HBc (IgG) and two (10%) anti‐HBc (IgM) were detected. Nucleic acid testing showed 5.0% prevalence of occult hepatitis B infection among the anti‐HBc‐positive blood donors with estimated HBV DNA viral load of 58 IU/ml. Demonstration of 5.0% occult hepatitis B prevalence showed the possibility of post‐transfusion hepatitis B infection in transfusion recipients with consequent possible liver damage should hepatitis B surface antigen alone be the continued practice in clinical settings. The inclusion of antibody to hepatitis B core antigen screening in addition to hepatitis B surface antigen marker is an essential step to ensuring optimal blood safety and prevent post‐transfusion hepatitis.     

The hepatitis B virus e antigen suppresses the respiratory burst and mobility of human monocytes and neutrophils

The Hepatitis B virus (HBV) e antigen (HBeAg) is a secretory, non-structural protein, and associated with persistent infection of HBV. Previous studies indicate that HBeAg is able to regulate T cell-mediated responses, however, the interaction between HBeAg and the innate immune system is poorly understood. In this study, we demonstrated that recombinant HBeAg (rHBe) bound to human peripheral blood monocytes, neutrophils, and B lymphocytes but not to T lymphocytes. We focused on investigating the effects of HBeAg on monocytes and neutrophils and found that rHBe decreased the respiratory burst in both types of cells. Furthermore, we observed that cell migration in monocytes and neutrophils was suppressed by rHBe in a transwell assay. The attenuation of rHBe was not caused by a general cytotoxic effect because rHBe treatment stimulated low levels of cytokine and chemokine production by monocytes and it promoted neutrophil survival. Since the recruitment of monocytes and neutrophils to the infected site is crucial for the initiation of inflammation, HBeAg may modulate innate immune responses by diminishing the respiratory burst and migration of monocytes and neutrophils, which might interfere with the subsequent innate and adaptive immune responses against HBV, leading to the establishment of chronic infection.     

Human T-lymphotropic virus type I among blood donors from Guadeloupe: donation, demographic, and biologic characteristics

BACKGROUND: Epidemiologic data on human T-lymphotropic virus type I (HTLV-I) in Guadeloupe (French West Indies) are scant. STUDY DESIGN AND METHODS: From January 1989 to December 1996, 59,426 blood donors were screened by enzyme immunoassay for antibodies to HTLV-I. All repeatedly reactive samples were confirmed by Western blot. Temporal trends in HTLV-I seropositivity rates were examined during the study period. A multivariate analysis of donation, demographic, and biologic characteristics was performed. RESULTS: Of the screened blood donors, 195 were confirmed as seropositive, for an overall prevalence of 0.33 percent (95% CI 0.28-0.38). A marked decrease in overall HTLV-I prevalence with time (from 0.47% in 1989 to 0.13% in 1996) was observed, which can be explained mainly by the decreasing percentage of recruited new donors during the study period. Four independent risk factors for HTLV-I were identified: new donor status (odds ratio [OR] 12.5), female sex (OR 1.7), increasing age (30-39 years: OR, 2.4; 40-49 years: OR, 3.7; >50 years: OR 6.6), and positive antibodies to hepatitis B virus core antigen (OR, 1.7). Selection of specific locations for blood collection was inversely associated with HTLV-I (OR 0.5). CONCLUSION: New donor status, advancing age, female sex, and positivity for hepatitis B virus core antibodies were the major factors associated with HTLV-I infection in Guadeloupe.     

抗人IgM（μ链）单克隆抗体的制备

本实验用可溶性抗原人 IgM 免疫 BALB/C 小鼠,按常规方法取免疫鼠脾细胞,分别与 NS-1、SP2/0细胞进行融合,ELISA 法筛选只与 IgM 反应阳性的抗体分泌杂交细胞,建立了6株杂交瘤株。经鉴定,此6株细胞分泌的抗体与 IgM 产生特异性反应,而不与其它免疫球蛋白重、轻链及 J 链交叉反应。经免疫电转印的硝酸纤维膜染色只显示分子量为72kD 的电泳带。放射免疫方法检测6个单克隆抗体,可分别识别4个不同的抗原决定簇。此组抗体识别 B 细胞胞浆内及膜表面μ链并可检测乙型病毒性肝炎患者血清中 HB_C-IgM 复合物。本组抗体间彼此加合可提高检测的灵敏性。抗 IgM(μ链)单克隆抗体对研究人 B 细胞的分化、成熟及功能提供了重要途径。     

Identification of a dominant immunogenic epitope of the nucleocapsid (HBc) of the hepatitis B virus

Four monoclonal antibodies to hepatitis B core antigen are described. The antibodies bind to the same or a very closely related epitope. Antibodies to this dominant epitope are present in the sera of patients with either acute or chronic hepatitis B virus (HBV) infection. A high percentage of inhibition of the binding of these antibodies to the core antigen by these four monoclonal antibodies suggests that the core antigen has a restricted antigenicity in man. Radiolabeled or peroxidase labeled forms of these monoclonal antibodies can be used to assay IgM and total anticore in serum.     

ELISA法检测HBVIgA型抗HBC的实验研究

目的：通过ＨＢＣＩｇＡ的水平，帮助临床诊断和治疗不同类型ＨＢＶ患者。方法：检测和比较了１１１份临床血清标本的ＨＢＶＩｇＡ水平，用酶联免疫试剂法。结果：在各种不同类型乙肝患者血清中，ＩｇＡ抗ＨＢＣ水平有所不同。肝脏损伤较重的肝癌、肝硬化、慢活肝和急性乙肝，其血清抗ＨＢＣＩｇＡ的阳性经及效价均明显高于肝损伤程度较轻的慢迁肝和携得，结论：从实验结果中我们发现抗ＨＢＶＩｇＡ与肝细胞损伤程度相关，是临床诊断     

Sensitivity and specificity of Anti‐HBc screening assays – which assay is best for blood donor screening?

Compared to HIV and hepatitis C virus, the residual infectious risk of hepatitis B virus (HBV) posed by blood products is about 10 times higher. In addition to HBsAg testing, screening for anti-HBc was recommended by the German Advisory Committee Blood in March 2005. Prevalence of anti-HBc in German blood donors was investigated at five test sites located in different geographic regions. In total, 12,000 blood donors were screened for anti-HBc by PRISM HBcore, and a statistically representative number of these were tested with Abbott Murex anti-HBc total, bioMérieux Hepanostika anti-HBc uniform, Bio-Rad Monolisa anti-HBc PLUS and Dade Behring Enzygnost anti-HBc. Anti-HBc repeat reactive samples were tested for anti-HBs, anti-HBe and HBV DNA by individual donation NAT. The mean prevalence of anti-HBc was 1.75% in donors that had not been tested for anti-HBc in the past. The percentage of anti-HBs in anti-HBc repeat reactive donors was 93.7%. Samples that were additionally reactive for anti-HBe were anti-HBc reactive in all tested assays. The sample to cut-off (S/Co) values for anti-HBc were lower (competitive assays) in samples that were also positive for anti-HBe, when compared to samples that were only anti-HBc reactive. Most commercially available anti-HBc assays provide sufficient sensitivity for routine screening purposes, and lacking specificity is no longer a serious issue for most of them. Assay differences were recognized for samples that were anti-HBc only reactive. The overall loss of 1.75% of positive testing donors can be significantly reduced to 0.45% by implementation of re-entry procedures for donors with an anti-HBs titre of over 100 IU/l and negative by sensitive ID-NAT.     

Can the serological status of “anti‐HBc alone” be considered a sentinel marker for detection of “occult” HBV infection?

Some individuals have "occult" infection with hepatitis B virus (HBV), defined as presence of HBV genome in the serum or liver tissue without HBV surface antigen (HBsAg) in the serum. The aim of this study was to investigate whether serum antibodies against HBV core antigen in isolation ("anti-HBc alone") are a useful marker of "occult" HBV in patients with or without hepatitis C virus (HCV) infection. "Anti-HBc alone" was detected in the sera of 119/6,544 (1.8%) asymptomatic outpatients referred to the diagnostic laboratory for routine testing for viral hepatitis, 62/607 (10.2%) drug users, and 42/195 (21.5%) patients with hepatocellular carcinoma. Using three in-house nested-PCR amplification assays to detect HBV preS-S (S), precore-core (C), and Pol viral regions, respectively, "occult" HBV sequences were found in 9 of the 223 sera (4.0%) with "anti-HBc alone." The highest prevalence of "occult" HBV sequences (5.9%) was detected in "anti-HBV alone" sera of individuals referred to the diagnostic laboratory without HCV antibodies. Direct sequencing of all PCR products confirmed the specificity of the PCR reactions and revealed the predominance of HBV genotype D. The data presented in this study suggest that detection of "anti-HBc alone" could reflect unrecognized "occult" HBV infection and that physicians should consider investigating such patients with HBV molecular tests.