Biomedical subjects

G Leroux-Roels

Publications and source records attributed to G Leroux-Roels.

At least 37 records · Page 2Linked to original sources

PubMed2001

In vivo inhibition of anti-hepatitis B virus core antigen (HBcAg) immunoglobulin G production by HBcAg-specific CD4(+) Th1-type T-cell clones in a hu-PBL-NOD/SCID mouse model.

Hepatitis B virus (HBV) core antigen (HBcAg)-specific CD4(+) T-cell responses are believed to play an important role in the control of human HBV infection. In the present study, HBcAg-specific, HLA-DR13*-restricted CD4(+) Th1-type T-cell clones were generated which secreted both gamma interferon and tumor necrosis factor alpha after in vitro antigen stimulation. These HBcAg-specific CD4(+) Th1-type T cells were able to lyse HBc peptide-loaded Epstein-Barr virus-transformed lymphoblastoid target cells in vitro. To examine whether these HLA-DR13*-restricted human CD4(+) Th1 T cells also display the same cytotoxic effects in vivo, we transferred peripheral blood leukocytes (PBL) derived from HBV-infected donors or an HBV-naïve donor sharing the DR13*, together with the HBcAg-specific CD4(+) Th1-type T cells and HBcAg, directly into the spleen of optimally conditioned Nod/LtSz-Prkdc(scid)/Prkdc(scid) (NOD/SCID) mice. The production of both secondary anti-HBc-immunoglobulin G (anti-HBc-IgG) and primary HBcAg-binding IgM in hu-PBL-NOD/SCID mice was drastically inhibited by HBcAg-specific CD4(+) Th1-type T cells. No inhibition was observed when CD4(+) Th1 cells and donor PBL did not share an HLA-DR13. These results suggest that HBcAg-specific CD4(+) Th1 T cells may be able to lyse HBcAg-binding, or -specific, B cells that have taken up and presented HBcAg in a class II-restricted manner. Thus, HBcAg-specific CD4(+) Th1-type T cells can modulate the function and exert a regulatory role in deleting HBcAg-binding, or -specific, human B cells in vivo, which may be of importance in controlling the infection.

Animals↗

PubMed2001

Long-term persistence of antibodies induced by vaccination and safety follow-up, with the first combined vaccine against hepatitis A and B in children and adults.

It is important to monitor the long-term persistence of antibodies induced by vaccination. Four cohorts were followed for their long-term immunity after vaccination with a combined hepatitis A and B vaccine (Twinrix; SmithKline Beecham Biologicals, Rixsenart, Belgium). Two cohorts of adults (ages 17-60 years), one of 1-6-year-olds, and one of 6-15-year-olds were vaccinated following a 0, 1, and 6-month schedule. Follow-up data until month 72 (adults) and month 60 (children) are available. At month 72, antibody to hepatitis A virus (anti-HAV) seropositivity (S+) was 100% for both adult cohorts (n = 40 and n = 47) and 95% and 89% of the vaccinees were seroprotected against hepatitis B virus (HBV), respectively. The geometric mean titres (GMTs; mIU/ml) for anti-HAV were 977 and 542 and the GMTs for the antibody to hepatitis B surface antigen (anti-HBs) were 322 and 90. For 1-6-year-olds at month 60 (n = 39), anti-HAV S+ was 100% with a GMT of 479 and 97% were protected against HBV with a GMT of 195. At month 60 for the 6-15-year-olds (n = 42), anti-HAV S+ was 100% with a GMT of 990 and 95% were protected against HBV with a GMT of 263. There have been no safety issues during the follow-up. In the past 5 years, a postmarketing surveillance system was available. Using this system, all spontaneous adverse events are collected and archived. Although infrequent, the most commonly reported adverse events after more than 13 million doses were allergic-type reactions followed by fever and injection site reactions. The combined hepatitis A and B vaccine is safe and is well tolerated. Immunity provided by the vaccine remains high in adults and children with comparable results to those obtained with monovalent vaccines.

Adolescent↗

PubMed2000

A comparison of two commercial recombinant vaccines for hepatitis B in adolescents.

The immunogenicity and reactogenicity profiles of three doses each of Engerix-B(R) (10 microg hepatitis B surface antigen) and Recombivax(R) (5 microg hepatitis B surface antigen), given on a 0, 1, 6 month schedule to healthy adolescents were compared in a single-blind, randomized clinical trial. One month following the third dose, seroprotection rates after Engerix-B and Recombivax were similar (99 and 98%, respectively). The geometric mean titre (GMT) was statistically significantly higher following vaccination with Engerix-B (3961 vs. 1001 mIU/ml; P=0.0001, Fisher's exact test). Most of the symptoms reported were mild or moderate in intensity and transient. There were no vaccine-related serious adverse events.

Adolescent↗

PubMed2000

A hepatitis B vaccine formulated with a novel adjuvant system.

Although more than 95% of the vaccinated population responds to the currently licensed vaccines against hepatitis B, some groups were found to be low responders. Lipid A as adjuvant, through its ability to activate macrophages, might improve humoral as well as cellular immune response. Therefore we evaluated the profile of a hepatitis B vaccine with the new adjuvant system SBAS4. 150 young adults were enrolled and randomized into three groups: one received the SBAS4 hepatitis B vaccine, the second Engerix-B(TM) and the third a hepatitis B vaccine with an alternative formulation on alum. Vaccinations were at 0 and 6 months. The vaccine was well tolerated. At month 7 all vaccinees were protected but with significant differences in GMTs between groups: 13,271 mIU/ml for the SBAS4 group versus 1203 and 1823 mIU/ml. Hence the hepatitis B vaccine with the new adjuvant system is more immunogenic compared to the other vaccines containing the same antigen and could be suitable for a two dose schedule.

Adjuvants, Immunologic↗

PubMed2000

Antigen-specific T cell responses in human peripheral blood leucocyte (hu-PBL)-mouse chimera conditioned with radiation and an antibody directed against the mouse IL-2 receptor beta-chain.

A weakness of the hu-PBL-SCID model for the study of human immune functions is the appearance of anergy and the consequent loss of T cell function. We demonstrate here that human T cells retain normal functions during the early stage of chimerism. At 1 and 2 weeks post-engraftment, T cells isolated from the peritoneal cavity of hu-PBL chimeras could be activated and proliferated upon stimulation with phytohaemagglutinin (PHA) or specific antigens to which the cell donor was known to be immune. T cells derived from hu-PBL-SCID and hu-PBL-NOD/LtSz-scid (NOD/SCID) mice not only proliferated but also produced interferon-gamma (IFN-gamma) and IL-5 following in vitro stimulation with tetanus toxoid (TT) or hepatitis B surface antigen (HBsAg). These antigen-specific T cells could only be demonstrated when cognate antigen was administered together with or immediately following the PBL transfer. Without an early rechallenge with antigen in vivo, no TT- or HBsAg-specific T cell responses could be elicited, showing the vulnerability and antigen-dependence of the T cell response. Vigorous anti-TT or anti-HBs responses could be observed in all chimeras. Administration of antigen together with the PBL graft enhanced the humoral anti-TT response in SCID and NOD/SCID mice but had little effect on the anti-HBs antibody response in NOD/SCID mice. These data confirm the observation that the B cell compartment in hu-PBL-SCID chimera is largely antigen-independent and extend this to SCID/NOD.

Animals↗

PubMed2000

Characterization of the T cell recognition of hepatitis B surface antigen (HBsAg) by good and poor responders to hepatitis B vaccines.

To study the regulation of the human cellular immune response to HBsAg we produced a series of HBsAg-specific T cell lines from good and poor responders to the hepatitis B vaccine. All T cell lines expressed CD4 on their membrane and could therefore be considered of the helper/inducer phenotype. The different HBsAg-specific T cell lines were restricted by HLA-DRB5*0101, DRB1*1201, -DRB1*0701, -DRB1*0301, -DPB1*0201, -DPB1*0402, and -DPB1*0901. In good responders to the hepatitis B vaccine different HLA molecules could act as restricting element. In poor responders the diversity of HLA class II restriction determinants was more limited. This leads us to conclude that the immune response to HBsAg is multispecific and polyclonal in good responders and paucispecific and oligoclonal in poor responders to the hepatitis B vaccine. By using a panel of synthetic peptides representing selected sequences of the HBsAg, the fine specificities of each of these T cell lines could be determined. Strikingly, the majority of the identified T cell epitopes was located in and around the first hydrophobic transmembranous region of the HBsAg. This was observed in T cell lines from good and poor vaccine responders, without distinction. The remarkable T cell immunogenicity of this region may reside in its richness in binding motifs for a variety of HLA class II determinants.

Adult↗

PubMed2000

Line probe assay for monitoring drug resistance in hepatitis B virus-infected patients during antiviral therapy.

Since the introduction of antiviral compounds such as lamivudine and famciclovir in the treatment schedules of patients with chronic hepatitis B virus (HBV) infection, the accumulation of a variety of mutations in the HBV polymerase gene has been observed. The selection of these mutations is generally considered the cause of viral nonresponsiveness and treatment failure. Therefore, the detection of these mutations is of clinical importance. Previously genotyped HBV strains isolated from treated and untreated patients were amplified with primers specific for the HBV polymerase region from amino acids 465 to 562. Amplified products were cloned into plasmid vectors. The clones were used as reference strains. A set of 38 highly specific oligonucleotide probes covering three different codon positions, L528M, M552V/I, and V/L/M555I, were selected. These probes were applied as 19 different lines on a membrane strip. The strips were then hybridized with PCR fragments from the reference panel, revealing the amino acids at the three codon positions simultaneously for each clone. PCR products generated from two patients infected with HBV genotypes A and C, respectively, and treated with nucleoside analogs were analyzed on these strips. A gradual increase in genetic HBV polymerase complexity was observed in follow-up samples compared to that in pretreatment samples. Additional analysis of HBV polymerase DNA fragments in recombinant plasmid clones demonstrated the existence of (i) clones with double mutations, (ii) clones with single mutations at either codon 528, 552, or 555, and (iii) the simultaneous occurrence of two or more viral populations within one sample. This line probe assay detected the complex quasispecies nature of HBV and provided some insight into the dynamics of resistance mutations.

Amino Acid Sequence↗

PubMed2000

Effects of Re-arterialization on early graft function and regeneration in the rat model of heterotopic auxiliary liver transplantation.

In the rat model of heterotopic auxiliary liver transplantation, graft re-arterialization may influence the outcome of inter-liver competition. This was investigated in the current study using two transplanted groups with or without graft re-arterialization. Immediately after reperfusion, the re-arterialized grafts showed significantly higher bile flow rate and bilirubin excretion than the grafts without re-arterialization. DNA synthesis rate was also increased more drastically in the re-arterialized group following the transplantation. Without re-arterialization, the rats developed more pronounced cytolysis and cholestasis. Among the long-term survivors, all healthy re-arterialized grafts regenerated, whereas 5/6 non-re-arterialized grafts atrophied. These data demonstrate that the re-arterialization increases graft survival by improving early hepatic function, enhancing regenerative response and preventing post-transplant biliary complications in this rat model.

Animals↗

PubMed2000

Long term response to interferon treatment in chronic hepatitis C patients is associated with a significant reduction in anti-E1 envelope antibody titers.

Interferon (IFN) alfa has been used widely for the treatment of chronic hepatitis C virus (HCV) infections but only a small number of patients treated have shown a sustained biochemical and virological response. Anti-envelope E1 and E2 antibody titers were assessed retrospectively before, during, and after treatment with IFN in order to evaluate their usefulness for the prediction and monitoring of therapy outcome in 115 patients infected chronically with HCV genotype 1b. At baseline, E2 induced more frequent and stronger immunogenic responses than E1, irrespective of patient response to therapy. E1 and E2 antibodies also tended to be higher in patients with a long-term or a transient response to IFN treatment than in patients who were absolute non-responders. In most patients, E1 and E2 antibody levels tended to be lower after treatment. This reduction was most pronounced and occurred most frequently in long-term responders to therapy. In this patient group, the reduction of E1 antibodies was more pronounced than that of E2 antibodies. In contrast to E2 antibodies, the decrease of E1 antibodies could already be observed at the end of therapy (week 24) and was significantly larger (p<0.05) than that observed in relapsers and non-responders. Thus, a sustained elevation of E1 antibodies seems to be associated with ongoing infection even when HCV RNA levels were undetectable in serum. Monitoring of E1 antibody titers may represent a useful additional marker to discriminate sustained responders from those who relapse in patients receiving interferon therapy.

Antigens, Viral↗

PubMed1999

The first combined vaccine against hepatitis A and B: an overview.

Hepatitis A and B infections are prevalent world-wide and are a significant cause of morbidity and mortality. A vaccine providing dual protection against hepatitis A and B is now available (Twinrix, SmithKline Beecham Biologicals). Six pivotal vaccine trials, involving 843 healthy adults, aged between 17 and 60 years and vaccinated following a 0, 1, 6 month schedule are discussed. At month 2 more than 99% of the vaccinees were seropositive for anti-HAV and 84% were protected against hepatitis B. The third dose induced a 12-fold increase in geometric mean titres (GMTs) to 5404 mIU/ml. One month after completion of the vaccination course nearly all vaccinees had protective titres against hepatitis B with a GMT of 4818 mIU/ml. Long term follow-up data until month 48 is available for two studies. At month 48 all 129 vaccinees sampled were still positive for anti-HAV antibodies and > 95% were still protected against hepatitis B. The combined hepatitis A and B vaccine Twinrix proves to be consistently safe, well tolerated and highly immunogenic and compares well with serological responses reached with monovalent vaccines. This combined hepatitis A and B vaccine offers more convenience, potentially better compliance and lower administration costs.

Adolescent↗

PubMed1998

Murine IL-2 receptor beta chain blockade improves human leukocyte engraftment in SCID mice.

Severe combined immunodeficient (SCID) mice accept human xenografts and can act as a model for human immune functions. Murine natural killer cells (NK), however, represent an important barrier for the reconstitution of SCID mice with human peripheral blood leukocytes (Hu-PBL). We investigated the effect on Hu-PBL survival of pretreatment with TM-beta1, a rat monoclonal antibody for the mouse IL-2 receptor beta chain. TM-beta1 greatly improved the survival of Hu-PBL. Human lymphocytes, predominantly T cells, survived in the peritoneum and infiltrated spleen and lungs already 1 week after engraftment and liver and thymus from 2 weeks on. Secondary humoral responses were evaluated with Hu-PBL from a donor immune to hepatitis-B surface Ag (HBsAg) and tetanus toxoid (TT). TM-beta1 pretreatment enhanced the recall Ig response to HBsAg and did not affect the baseline anti-TT Ig production. In conclusion, TM-beta1 pretreatment of SCID mice significantly improves the survival and functionality of the Hu-PBL graft.

Animals↗

PubMed1998

HBV-specific lymphoproliferative and cytokine responses in patients with chronic hepatitis B.

BACKGROUND/AIMS: Hepatitis B virus specific T cell responses are crucial for viral elimination but their nature is not fully understood. METHODS: We studied the regulation of proliferation and cytokine production after antigenic stimulation in peripheral blood mononuclear cells from chronically HBV-infected patients and subjects with natural immunity after recovery from an acute infection. Proliferation and production of interferon-gamma, IL-10 and tumor necrosis factor-alpha were determined after stimulation with HBcAg, HBeAg or HBsAg in the absence or presence of IL-12 or neutralizing antibodies to IL-12, interferon-gamma, IL-4, IL-10 or tumor necrosis factor-alpha. RESULTS: Upon stimulation with HBcAg or HBeAg, peripheral blood mononuclear cells from chronic hepatitis B virus patients displayed a clear class-II restricted proliferative response (SI greater than 2.5). Both interferon-gamma (less than 50 IU/ml) and IL-10 levels up to 600 pg/ml were detected. Proliferative or cytokine responses to HBsAg were very weak or absent. Addition of IL-12 to HBeAg-stimulated cultures increased the production of interferon-gamma to more than 200 IU/ml in all patients and slightly increased the production of IL-10. Neutralization of IL-10 increased the HBeAg-induced interferon-gamma production but had no effect on tumor necrosis factor-alpha production. Addition of anti-IL-4 or anti-tumor necrosis factor-alpha had no significant influence on proliferation or cytokine release. Importantly, in both chronic hepatitis B virus patients and naturally immune subjects, IL-12 induced proliferative and interferon-gamma responses in peripheral blood mononuclear cells stimulated with HBsAg. CONCLUSIONS: Our data indicate that peripheral blood mononuclear cells from chronic hepatitis B virus patients proliferate and produce interferon-gamma and IL-10 upon HBeAg but not upon HBsAg stimulation. IL-12 augments the HBeAg-induced responses and, additionally, provokes proliferation and interferon-gamma production in HBsAg-stimulated cultures.

Cryopreservation↗

PubMed1998

Ultrarapid hepatitis C virus clearance by daily high-dose interferon in non-responders to standard therapy.

BACKGROUND/AIMS: To analyze the kinetics of the hepatitis C virus and the patterns of resistance to interferon alpha, we assessed HCV RNA levels early during retreatment with high-dose interferon in patients who did not respond to standard treatment. METHODS: Eleven non-responders to previous therapy with 3-6 MU interferon three times a week were retreated with daily 10 MU. Plasma was sampled at days 0, 1, 2, 3, 14 and 28; all samples were prepared within 2 h and stored at -70 degrees C without thawing until analysis. The quantitative HCV RNA level was assessed by the Superquant assay (NGI, USA). The Eurohep reference panel, tested blindly, confirmed the linearity of the assay with a detection limit for genotypes 1 and 3 between 10(2) and 10(3) copies/ml. RESULTS: All patients showed a fall in viral load between week 0 and week 2 (2.6 log, i.e. 99.7%, range 1.3-4.7 log), whereas no fall was detected after week 2. Closer examination in nine patients revealed that all had a dramatic fall in the first 2 days (first day 1.8 log, 0.8-3.5; second day 0.8 log, -0.2-1.3), without any significant fall thereafter. The calculated half-life of viral decay in plasma was 5 (2-8.9) h, corresponding to a clearance of 2.4 (0.2-13.7) x 10(11) virions per day. Sustained responders showed a significantly greater fall in viral load in the first day (3.2 log, 2.8-3.5) than those who did not respond (1.4 log, 0.8-2.1, p=0.001). All three sustained responders had undetectable plasma HCV RNA at day 14. CONCLUSION: In patients without a response to standard interferon, the hepatitis C virus has a high daily turnover rate similar to that reported in naive patients. Our findings suggest that an early clearance of HCV RNA from the circulation is the key to a sustained response, which might be induced in about 25% of these patients by treatment with high (10 MU) daily doses of interferon. These findings have important implications for the concept of treatment of hepatitis C, which should shift its focus from long-term mild treatment towards aggressive therapy aiming at a fast viral disappearance within the first few days.

Adult↗

PubMed1998

Safety and immunogenicity of a hepatitis B vaccine formulated with a novel adjuvant system.

A formulation of recombinant hepatitis B surface antigen (HBsAg) combined with a novel adjuvant system, SBAS4--a combination of aluminium salt and monophosphoryl lipid A (MPL), was assessed in 27 healthy adult volunteers with a commercial vaccine (Engerix-B) as control. After three doses (0, 1, 6 months schedule), reactogenicity profiles were similar. Local reactions were essentially mild, the most frequent being soreness at the injection site. Seroprotection was achieved after two doses in all subjects given the candidate vaccine, all Engerix-B vaccines being seroprotected after the third dose. After the second and third doses, higher anti-HBs Geometric Mean Titres (GMTs) were observed in the group which received the formulation with the novel adjuvant system, and cellular immunity, measured as HBsAg-specific lymphoproliferation was stronger than with Engerix-B. These results indicate that the new formulation is safe, well-tolerated and immunogenic and may promote more rapid protection against hepatitis B infection.

Adjuvants, Immunologic↗

PubMed1998

Response to hepatitis B vaccine: multiple HLA genes are involved.

The mechanism underlying the impaired immune response to hepatitis B vaccines in up to 10% of healthy subjects is not known. An increased incidence of poor responsiveness in subjects with HLA-DR3+ or -DR7+ haplotypes has been documented, suggesting that HLA-DR-linked genes may regulate the human response to hepatitis B surface antigen. However, not all HLA-DR3+ and/or -DR7+ individuals are poor responders, and subjects with identical HLA-DR haplotypes sometimes display totally divergent antibody responses to vaccination. HLA class II DNA typing was performed in well and poorly responding hepatitis B vaccine recipients and we analyzed the role of the single HLA-DR, -DP, and -DQ molecules and of their associated (interaction) haplotypes in the response to hepatitis B vaccination. Statistical analysis revealed that HLA-DRB1*010*, -DR5, -DPB1*040*, -DQB1*0301, and -DQB1*0501 were more abundant in good responders, whereas HLA-DRB1*07, -DPB1*1101, and -DQB1*020* were associated with poor response, with DQB1*020* showing the strongest association with poor responsiveness. We further investigated whether there were interactions between the HLA factors contributing to poor responsiveness. We show here that HLA-DPB1*02 was negatively associated with responsiveness when it occurred in association with haplotype DRB1*0701/DRB4*0101-DQB1*020*, and DRB4*0101 was negatively associated with responsiveness when it occurred in association with haplotype DRB1*0301/DRB3*0101-DQB1*020*. Our results indicate that the immune response to hepatitis B vaccine is largely determined by HLA-DR, -DP, and -DQ genes and that interaction between HLA molecules that are not in linkage disequilibrium contributes to poor responsiveness.

Adult↗

PubMed1998

Relapse markers in multiple sclerosis: are in vitro cytokine production changes reflected by circulatory T-cell phenotype alterations?

In vitro tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma) and interleukin-2 (IL-2) production, serum neopterin levels, and T-lymphocyte subpopulations were determined on a monthly basis in 22 MS patients. We found increased in vitro TNF-alpha production from 4 weeks on prior to the day of an exacerbation. There was a significant correlation with in vitro IFN-gamma release, the absolute blood monocyte count and the serum neopterin levels, suggesting that monocytes stimulated by IFN-gamma play an important role in the TNF-alpha production. Serial analysis of in vitro TNF-alpha production proved to be a helpful tool in predicting relapses in MS patients. Furthermore, elevated levels of IFN-gamma and IL-2 after stimulation with OKT3 during exacerbations were demonstrated. These increases were not reflected by changes in T-lymphocyte subpopulations. However, significant differences in T-cell subsets were observed between controls and relapsing progressive patients.

Adult↗

PubMed1997

Hepatitis B vaccine containing surface antigen and selected preS1 and preS2 sequences. 1. Safety and immunogenicity in young, healthy adults.

The safety and immunogenicity of a yeast-derived recombinant hepatitis B virus (HBV) vaccine containing surface antigen (S) and selected preS1 and preS2 sequences (S-L*) were compared with those of a vaccine prepared with S alone (Engerix-B). S-L* consisted of composite particles containing S and L* at a ratio of 70/30. L* encompassed amino acid residues 12-52 of preS1 residues 133-145 of preS2, and the entire S domain. A total of 100 healthy, HBV-seronegative, young adults were randomized to receive 20 micrograms/dose of either S-L* or Engerix-B under double-blind conditions according to a 0-, 1-, 2-, 12-month schedule. In vivo humoral and in vitro lymphoproliferative responses to S and preS regions were monitored. Addition of the selected preS sequences to S did not enhance the in vivo humoral anti-HBs response but improved the in vitro stimulating capacity of the antigen (L*) in S-L* primed subjects.

Adult↗

PubMed1997

Hepatitis B vaccine containing surface antigen and selected preS1 and preS2 sequences. 2. Immunogenicity in poor responders to hepatitis B vaccines.

The immunogenicity of a yeast-derived recombinant hepatitis B virus (HBV) vaccine containing surface antigen (S) and selected preS1 and preS2 sequences (S-L*) was compared with that of a vaccine containing S alone (Engerix-B) in 32 healthy adults with a previous history of poor response (anti-HBs < 10 mIU ml-1) after at least three consecutive monthly doses of hepatitis B vaccines. The poor responders were randomized to receive three additional 20-microgram doses of either S-L* or Engerix-B in a double-blind fashion according to a 0-, 1-, 2-month schedule. In vivo humoral and in vitro lymphoproliferative responses to the S and preS regions were monitored. Although the addition of the selected preS sequences to S did not enhance the in vivo humoral anti-HBs response, the administration of the three additional vaccine doses, irrespective of their preS content, induced seroprotective anti-HBs levels in most vaccinees (29/32, 91%). In vitro proliferative responses to HBV surface antigens were only observed in subjects displaying anti-HBs titers > 1000 mIU ml-1 after the third additional vaccine dose.

Adult↗