Reduced humoral immune response after BNT162b2 coronavirus disease 2019 messenger RNA vaccination in cancer patients under antineoplastic treatment.

BACKGROUND: Cancer patients are at a higher risk of developing severe coronavirus disease 2019 (COVID-19). However, the safety and efficacy of COVID-19 vaccination in cancer patients undergoing treatment remain unclear. PATIENTS AND METHODS: In this interventional prospective multicohort study, priming and booster doses of the BNT162b2 COVID-19 vaccine were administered 21 days apart to solid tumor patients receiving chemotherapy, immunotherapy, targeted or hormonal therapy, and patients with a hematologic malignancy receiving rituximab or after allogeneic hematopoietic stem cell transplantation. Vaccine safety and efficacy (until 3 months post-booster) were assessed. Anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) receptor-binding domain (RBD) antibody levels were followed over time (until 28 days after the booster) and in vitro SARS-CoV-2 50% neutralization titers (NT50) toward the wild-type Wuhan strain were analyzed 28 days after the booster. RESULTS: Local and systemic adverse events (AEs) were mostly mild to moderate (only 1%-3% of patients experienced severe AEs). Local, but not systemic, AEs occurred more frequently after the booster dose. Twenty-eight days after the booster vaccination of 197 cancer patients, RBD-binding antibody titers and NT50 were lower in the chemotherapy group {234.05 IU/ml [95% confidence interval (CI) 122.10-448.66] and 24.54 (95% CI 14.50-41.52), respectively} compared with healthy individuals [1844.93 IU/ml (95% CI 1383.57-2460.14) and 122.63 (95% CI 76.85-195.67), respectively], irrespective of timing of vaccination during chemotherapy cycles. Extremely low antibody responses were seen in hematology patients receiving rituximab; only two patients had RBD-binding antibody titers necessary for 50% protection against symptomatic SARS-CoV-2 infection (<200 IU/ml) and only one had NT50 above the limit of detection. During the study period, five cancer patients tested positive for SARS-CoV-2 infection, including a case of severe COVID-19 in a patient receiving rituximab, resulting in a 2-week hospital admission. CONCLUSION: The BNT162b2 vaccine is well-tolerated in cancer patients under active treatment. However, the antibody response of immunized cancer patients was delayed and diminished, mainly in patients receiving chemotherapy or rituximab, resulting in breakthrough infections.

Assessment of IgA anti-PT and IgG anti-ACT reflex testing to improve Bordetella pertussis serodiagnosis in recently vaccinated subjects.

OBJECTIVES: Quantifying IgG antibodies to pertussis toxin (PT) is the most specific and sensitive method for the serodiagnosis of a Bordetella pertussis infection. Since PT is a component of acellular pertussis vaccines, anti-PT IgG is also induced by vaccination, precluding pertussis serodiagnosis based exclusively on anti-PT IgG in recently vaccinated subjects. Here, we aim to identify additional B. pertussis-specific serological markers that can discriminate between infection and recent vaccination. METHODS: The clinical usefulness of measuring IgA directed to the vaccine antigen PT and IgG directed to non-vaccine antigens (Fim2/3, LPS, ACT, CatACT) was evaluated in nine well characterized subject groups, aged 10-89 years (n = 390). Serum anti-PT IgG levels (>125 IU/mL) served as an indicator for a recent B. pertussis infection. Comparing symptomatic pertussis-infected subjects (n = 140) with recently vaccinated, non-infected subjects (n = 100) revealed the optimal cut-off, accuracy, sensitivity and specificity for each single parameter. RESULTS: For pertussis diagnosis in recently vaccinated subjects, the measurement of anti-PT IgA (cut-off 15 IU/mL) and anti-ACT IgG (cut-off 15 U/mL) resulted in accuracies of 95% (91.5-97.1) and 87.5% (82.7-91.1), sensitivities of 92.9% (87.4-96.0) and 83.6% (76.5-88.8) and specificities of 98% (93.0-99.4) and 93% (86.3-96.6), respectively. Comparing anti-PT IgA levels between the youngest (10-19 years, n = 38) and oldest (70-89 years, n = 17) age groups revealed an age-dependent increase in antibody levels in pertussis-infected subjects (p < 0.0001). CONCLUSIONS: Reflex testing of anti-PT IgA and anti-ACT IgG improves pertussis serodiagnosis in recently vaccinated symptomatic subjects with elevated anti-PT IgG levels. Furthermore, both markers can discriminate between vaccination and recent infection in pertussis serosurveillance studies.

HCV genotype distribution in Flanders and Brussels (Belgium): unravelling the spread of an uncommon HCV genotype 5a cluster.

In order to study the hepatitis C virus (HCV) epidemiology in Flanders, Belgium, the HCV genotype of 2,301 patients diagnosed with HCV between 2001 and 2009 was determined. HCV genotyping was conducted using the Versant LiPA 1.0 or Versant LiPA 2.0 assay. To explore the transmission history of a remarkable cluster of the rarely found HCV genotype 5a, face-to-face interviews based on detailed questionnaires and maximum likelihood phylogenetic analysis were performed. HCV genotype 1 was the most prevalent genotype in all provinces, followed by HCV genotype 3 in East Flanders, Antwerp, Flemish Brabant and Limburg. In Brussels, HCV genotype 4 was the second most prevalent genotype. This observation is due to the immigration of patients from the Middle East and Africa. Remarkably, a cluster of HCV genotype 5a was found in West Flanders, where it represents the second most prevalent genotype, accounting for 26.2% of HCV infections. We could not identify one major transmission source explaining the whole HCV genotype 5a epidemic. Instead, several smaller possible transmission chains were identified and confirmed phylogenetically. Overall, the HCV genotype 5a epidemic in West Flanders seems to be mainly associated with blood transfusion and unsafe medical practices.

The duration of in vitro stimulation with recall antigens determines the subset distribution of interferon-gamma-producing lymphoid cells: a kinetic analysis using the Interferon-gamma Secretion Assay.

Analyses of cellular immune responses during natural infections and following vaccination with established or candidate vaccines are becoming increasingly important and so are the research tools used to achieve this goal. During a recent evaluation of the analytical performance characteristics of one of these techniques, the interferon-gamma secretion assay, we noticed that following overnight incubation of PBMC with recall antigens (varicella-zoster antigen, Candida albicans antigen or hepatitis B surface antigen) NK cells are frequently the most predominant interferon-gamma-producing cell population. In this study, we monitored the subset distribution of interferon-gamma-producing cells following more extended in vitro culture periods and found that, irrespective of the antigen applied, the contribution of NK cells decreased whereas the importance of T cells and NKT cells rose. Analysis of the subset distribution showed that HBsAg stimulated CD4 cells predominantly whereas Candida antigen and varicella-zoster antigen were better inducers of CD8 responses. No correlation was found between the kinetics of total number of interferon-gamma-producing cells and the changes of concentrations of interferon-gamma in the culture supernatants. Interferon-gamma levels in culture supernatants correlated strongly with the kinetics of T(H) lymphocytes (CD3+, CD4+), CTL (CD3+, CD8+), and NKT cells (CD3+, CD56+). These observations lead us to conclude that methods that enumerate cytokine-secreting cells without determining their phenotype should be interpreted with great care and that an 'elispot' should not be directly considered as the footprint of a T lymphocyte.

Non-responsiveness to hepatitis B surface antigen vaccines is not caused by defective antigen presentation or a lack of B7 co-stimulation.

The mechanisms causing non-responsiveness to hepatitis B surface antigen (HBsAg) vaccines in man remain elusive. The increased incidence of non-responsiveness in subjects with HLA-DR3(+) or -DR7(+) haplotypes suggests that immune response mechanisms governed by genes of the MHC are involved. Homozygotes for these two haplotypes are found almost exclusively in the non-responder (NR) population. It is conceivable that antigen-presenting cells (APC) of NR are defective in the uptake of HBsAg and that they are unable to present this Ag adequately. Previously, we demonstrated that DR2(+), DR7(+) and DP4(+) NR were able to present HBsAg. In the present paper we demonstrate that six DR0301(+) NR, five of which are homozygous for this marker, were able to take up, process and present HBsAg to HBsAg-specific, DR0301-restricted T cell lines. Non-fractionated peripheral blood mononuclear cells (PBMC) from the DR0301(+) NR did not proliferate to HBsAg in vitro, whereas they proliferated vigorously upon stimulation with tetanus toxoid, thus ruling out the presence of a generalized immunodeficiency. We therefore conclude that HLA-DR0301(+) NR vaccinees are not deficient in their HBsAg-presentation. Because it was demonstrated that recently activated T cells can apparently bypass the requirement for B7, we may have overlooked the role of the B7-co-stimulation in our set-up that used HBsAg-specific T cell lines. Therefore we examined the expression of B7 co-stimulatory molecules on NR-APC. CD86 was normally present on these cells and was not down-regulated after culturing the PBMC in the presence of HBsAg. We conclude that CD86 expression on CD14(+) monocytes of DR0301- and DR07-homozygous poor responders is not deficient and cannot be the mechanism underlying the non-responsiveness of these subjects.

The interferon gamma secretion assay: a reliable tool to study interferon gamma production at the single cell level.

Different single-cell analyses for the detection of antigen-specific T cells based on antigen-triggered induction of cytokine production (elispot, intracellular cytokine staining, cytokine secretion assay, etc.) have been analyzed. In this paper we present the data of a thorough validation of the IFNgamma Secretion Assay (ISA, Miltenyi Biotec, Bergisch Gladbach, Germany). In this assay the secreted IFNgamma is bound to the cell surface and is then stained as an artificial surface molecule and analyzed by flow-cytometry. The introduction of five quality criteria markedly improved the reproducibility of this assay and made it very reliable (intra-assay variability<5%; inter-assay variability<20%). Recovery experiments further demonstrated that almost 100% of IFNgamma(+) labeled cells could be detected by this technology. In order to analyze which cell subsets contribute to IFNgamma-production, we compared the results obtained in different individuals after VZAg-stimulation. Three different IFNgamma-secretion patterns could be discerned. In Pattern 1 there is a predominant and almost equal contribution of T cells and NK cells with a minor contribution of CD3(+)CD56(+) and B cells. Pattern 2, which is most abundant, is characterized by a predominance of NK cells (60-70%). Pattern 3 differs from the previous one in its minor contribution of NK cells. Here T cells predominate the IFNgamma secretion. These results clearly demonstrate that the IFNgamma(+) subset distribution after VZAg-stimulation is not uniform and differs individually. Furthermore, the ISA-technology proves to be very useful in vaccine research. This was demonstrated by testing the IFNgamma(+) secretion pattern after HBsAg-stimulation in PBMC from HBsAg-vaccinated individuals.

The immunogenicity and reactogenicity profile of a candidate hepatitis B vaccine in an adult vaccine non-responder population.

Approximately 5% of vaccinees display an inadequate response after the administration of the standard three dose hepatitis B vaccine. A new hepatitis B vaccine (HBsAg/AS04) formulated with the adjuvant AS04 which contains 3'-deacylated monophosphoryl lipid A (3D-MPL) and alum has been developed. AS04 enhances the immune response which may be beneficial to non-responders. In a single-blind, randomised study, we tested the immunogenicity and reactogenicity of the new vaccine with that of commercially established hepatitis B vaccine, both on a 0, 1, 6 months schedule in 20-60 years old non-responders (titre <10 m IU/ml after four doses of hepatitis B vaccine). One month after the first dose the seroprotection rate was 44% for group 1 (58 subjects) receiving the established vaccine versus 66% for group 2 receiving HBsAg/AS04 (57 subjects) (P=0.03). One month after the second dose this was 58 and 81%, respectively (P<0.005) and 1 month after the third dose this was 68 and 98%, respectively (P<0.001). One month after each dose, GMTs were 34, 56 and 111 mIU/ml for group 1 versus 123222 and 1937 mIU/ml for the HBsAg/AS04 group (P<0.05, <0.01 and 0.0001, respectively). Pain at the injection site was the most commonly reported local symptom and very few symptoms were scored as severe. In this group of adult non-responders to previous hepatitis vaccination, the HBsAg/AS04 vaccine was well tolerated and induced, at all time-points, a superior immune response compared to the licensed hepatitis B vaccine.

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.

Prevention of hepatitis B infections: vaccination and its limitations.

Infection with hepatitis B virus has become a vaccine-preventable disease. The recombinant hepatitis B vaccines available today are safe and immunogenic. In order for these vaccines to eradicate HBV a universal vaccination of neonates and/or children needs to be implemented. Major obstacles on the road to global hepatitis B vaccination are poverty and scarcity of human resources in those parts of the world who are most badly in need of these vaccines. Despite their proven immunogenicity hepatitis B vaccines are unable to induce an adequate immune response in 5-10% of healthy adults. The non-responsiveness of these subjects is a selective phenomenon and not the expression of a general immune deficiency. Studies that correlated the HLA haplotype of vaccine recipients with their anti-HBs response patterns has led to the identification of markers of good and non/poor response. Universal vaccination of neonates and children has elicited questions about the durability of antibody persistence and the need for booster doses later in life. The European Consensus Group on Hepatitis B Immunity has proposed a series of recommendations that are summarized in this review.

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.

Hepatitis B virus core antigen binds and activates naive human B cells in vivo: studies with a human PBL-NOD/SCID mouse model.

The hepatitis B virus (HBV) core (HBc) antigen (HBcAg) is a highly immunogenic subviral particle. Studies with mice have shown that HBcAg can bind and activate B cells in a T-cell-independent fashion. By using a human peripheral blood leukocyte (hu-PBL)-Nod/LtSz-Prkdc(scid)/Prkdc(scid) (NOD/SCID) mouse model, we show here that HBcAg also activates human B cells in vivo in a T-cell-independent way. HBcAg was capable of inducing the secretion of HBcAg-binding human immunoglobulin M (IgM) in naive human B cells derived from adult human and neonatal (cord blood) donors when these hu-PBL were transferred directly into the spleens of optimally conditioned NOD/SCID mice. No such responses were found in chimeric mice that were given hu-PBL plus HBV e antigen or hu-PBL plus phosphate-buffered saline. In addition, HBcAg activated purified human B cells to produce anti-HBc IgM in the chimeric mice, thus providing evidence that HBcAg behaves as a T-cell-independent antigen in humans. However, HBcAg-activated hu-PBL from naive donors were unable to switch from IgM to IgG production, even after a booster dose of HBcAg. Production of HBcAg-specific IgG could only be induced when hu-PBL from subjects who had recovered from or had an ongoing chronic HBV infection were transferred into NOD/SCID mice. Our data suggest that humans also have a population of naive B cells that can bind HBcAg and is subsequently activated to produce HBcAg-binding IgM.

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.

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.

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.

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.

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.

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.

Safety and immunogenicity of a combined hepatitis A and hepatitis B vaccine in young healthy adults.

BACKGROUND: A combination of hepatitis A and hepatitis B monovalent vaccines could offer advantages for disease control programs in terms of convenience, compliance and cost. METHODS: Under randomized, double-blind conditions, 156 healthy young adults were divided into 3 groups to receive 1 of 3 lots of a combined hepatitis A/hepatitis B vaccine administered at months 0, 1, and 6. Safety and immunogenicity were assessed after each dose. RESULTS: Transient and predominantly mild reactions were reported by slightly more than half the vaccinees; no serious adverse effects were relate to vaccination. One month after dose 2, all subjects had converted to the hepatitis A component. Geometric mean titers (GMTs) of antibodies of hepatitis A virus varied from 4415 to 4882 mIU/ml in the three groups. For hepatitis B, most vaccinees (73%-92%) had protective levels of antibodies to hepatitis B virus (anti-HBs) after the second dose, and all were sero-protected after the booster. Anti-HBs GMTs at month 7 ranged from 1917 to 3298 mIU/ml. CONCLUSIONS: No statistically significant differences were observed between vaccine lots. The combined hepatitis A/hepatitis B vaccine was safe and clinically well tolerated and induced immune responses quantitatively similar to those obtained with the respective monovalent vaccines.

Lymphoproliferative responses to hepatitis C virus core, E1, E2, and NS3 in patients with chronic hepatitis C infection treated with interferon alfa.

The quality of the hepatitis C virus (HCV)-specific T-cell response may greatly determine the course of an HCV infection. An adequate T-cell response may contribute to a successful clearance of the virus and a rapid recovery from the disease. An inadequate response may lead to viral persistence and may eventually contribute to the pathogenesis of hepatocellular damage in chronic disease. The effect of interferon alfa (IFN-alpha), presently the most popular therapeutic agent for chronic HCV infections, on HCV-specific T-cell responses is completely unknown. To demonstrate the presence of HCV-specific T lymphocytes during chronic HCV infections, to know their antigenic specificities, and to examine possible effects of IFN-alpha treatment on their presence and antigen recognition patterns, we have stimulated peripheral blood mononuclear cells (PBMC) from 35 chronic HCV patients with nine pools of synthetic peptides representing the HCV Core, E1, and E2 proteins as well as with a recombinant NS3 protein. The proliferative responses of PBMC from 16 healthy control subjects toward these antigens were measured for comparison. Lymphoproliferative responses of patients with chronic HCV infections were assayed either before (in 10 patients), during (in 13 patients), or after (in 21 patients) treatment with IFN-alpha. The analysis showed that PBMC from most HCV patients consistently recognized the COOH-terminal part of the core protein. E1, E2, and NS3 were recognized less frequently. This recognition pattern was not related to the therapy with IFN-alpha nor to the clinical response of the patient toward this therapy. The response to the Core protein could be fine-mapped to the COOH-terminal region encompassing amino acids (aa) 73 to 92, 121 to 140, 145 to 164, and 157 to 176.

Nonresponders to hepatitis B vaccine can present envelope particles to T lymphocytes.

The mechanisms causing nonresponsiveness to hepatitis B surface Ag (HBsAg) vaccines in humans remain largely unknown. The increased incidence of nonresponsiveness in subjects with HLA-DR3 or -DR7 haplotype suggests that immune response mechanisms governed by genes of the MHC are involved. It is conceivable that APC of nonresponders are defective in the presentation of HBsAg because they are unable to adequately take up, process, or present this Ag. To examine this hypothesis we have used PBMC from nonresponders to present recombinant particles containing S or PreS2-S sequences to HBsAg-specific T cell lines from haplo-identical responder vaccinees. The proliferative response of these lines was used to evaluate the efficacy of Ag presentation. Unfractionated PBMC from five DR2+ and six DR7+ nonresponders did not proliferate to HBsAg in vitro, whereas they vigorously proliferated upon stimulation with tetanus toxoid, thus ruling out the presence of a generalized immunodeficiency. All DR2(15)+ nonresponders were able to present hepatitis B envelope Ag to HBsAg-specific, DR1501-restricted T cells. PBMC from six DR7+ nonresponders were all able to present HBsAg to DR07-restricted T cell lines and PBMC from three DPw4+ nonresponders were able to present HBsAg to DP0402-restricted T cell lines. Additional experiments showed that PBMC from two nonresponders presented HBsAg equally well and sometimes better than PBMC from two partially HLA-matched high responders. We conclude that HLA-DR2+, -DR7+, and -DPw4+ nonresponder vaccinees are able to take up, process and present HBsAg to allogeneic, haplo-identical T cell lines in vitro.