Molecular Basis of the Divergent Immunogenicity of Two Pediatric Tick-Borne Encephalitis Virus Vaccines.

UNLABELLED: Studies evaluating the immunogenicity of two pediatric tick-borne encephalitis virus (TBEV) vaccines have reported contradictory results. These vaccines are based on two different strains of the European TBEV subtype: FSME-Immun Junior is based on the Neudörfl (Nd) strain, whereas Encepur Children is based on the Karlsruhe (K23) strain. The antibody (Ab) response induced by these two vaccines might be influenced by antigenic differences in the envelope (E) protein, which is the major target of neutralizing antibodies. We used an established hybrid virus assay platform to compare the levels of induction of neutralizing antibodies against the two vaccine virus strains in children aged 1 to 11 years who received two immunizations with FSME-Immun Junior or Encepur Children. The influence of amino acid differences between the E proteins of the Nd and K23 vaccine strains was investigated by mutational analyses and three-dimensional computer modeling. FSME-Immun Junior induced 100% seropositivity and similar neutralizing antibody titers against hybrid viruses containing the TBEV E protein of the two vaccine strains. Encepur Children induced 100% seropositivity only against the hybrid virus containing the E protein of the homologous K23 vaccine strain. Antibody responses induced by Encepur Children to the hybrid virus containing the E protein of the heterologous Nd strain were substantially and significantly (P < 0.001) lower than those to the K23 vaccine strain hybrid virus. Structure-based mutational analyses of the TBEV E protein indicated that this is due to a mutation in the DI-DII hinge region of the K23 vaccine strain E protein which may have occurred during production of the vaccine seed virus and which is not present in any wild-type TBE viruses. IMPORTANCE: Our data suggest that there are major differences in the abilities of two European subtype pediatric TBEV vaccines to induce antibodies capable of neutralizing heterologous TBEV strains. This is a result of a mutation in the DI-DII hinge region of the E protein of the K23 vaccine virus strain used to manufacture Encepur Children which is not present in the Nd strain used to manufacture FSME-Immun Junior or in any other known naturally occurring TBEVs.

A Novel multivalent OspA vaccine against Lyme borreliosis is safe and immunogenic in an adult population previously infected with Borrelia burgdorferi sensu lato.

Lyme borreliosis (LB) patients who recover, as well as previously infected asymptomatic individuals, remain vulnerable to reinfection with Borrelia burgdorferi sensu lato. There is limited information available about the use of OspA vaccines in this population. In this study, a randomized double-blind phase I/II trial was performed to investigate the safety and immunogenicity of a novel multivalent OspA vaccine in healthy adults who were either seronegative or seropositive for previous B. burgdorferi sensu lato infection. The participants received three monthly priming immunizations with either 30 µg or 60 µg alum-adjuvanted OspA antigen and a booster vaccination either 6 months or 9 to 12 months after the first immunization. The antibody responses to the six OspA serotypes included in the vaccine were evaluated. Adverse events were predominantly mild and transient and were similar in the seronegative and seropositive populations. Substantial enzyme-linked immunosorbent assay (ELISA) and surface-binding antibody responses against all six OspA antigens were induced after the primary immunization schedule in both populations, and they were substantially increased with both booster schedules. The antibody responses induced by the two doses were similar in the seronegative population, but there was a significant dose response in the seropositive population. These data indicate that the novel multivalent OspA vaccine is well tolerated and immunogenic in individuals previously infected with B. burgdorferi sensu lato. (This study is registered at ClinicalTrials.gov under registration no. NCT01504347.).

Safety and immunogenicity of a vero cell culture-derived whole-virus influenza A(H5N1) vaccine in a pediatric population.

BACKGROUND: Children are highly vulnerable to infection with novel influenza viruses. It is essential to develop candidate pandemic influenza vaccines that are safe and effective in the pediatric population. METHODS: Infants and children aged 6-35 months and 3-8 years, respectively, were randomized to receive 2 immunizations with a 7.5-µg or 3.75-µg hemagglutinin (HA) dose of a nonadjuvanted whole-virus A/Vietnam(H5N1) vaccine; adolescents aged 9-17 years received a 7.5-µg dose only. A subset of participants received a booster immunization with an A/Indonesia(H5N1) vaccine approximately 1 year later. HA and neuraminidase antibody responses were assessed. RESULTS: Vaccination was safe and well tolerated; adverse reactions were transient and predominantly mild. Two immunizations with the 7.5-µg dose of A/Vietnam vaccine induced virus microneutralization (MN) titers of ≥1:20 against the A/Vietnam strain in 68.8%-85.4% of participants in the different age groups. After the booster, 93.1%-100% of participants achieved MN titers of ≥1:20 against the A/Vietnam and A/Indonesia strains. Neuraminidase-inhibiting antibodies were induced in ≥90% of participants after 2 immunizations with the 7.5 µg A/Vietnam vaccine and in 100% of participants after the booster. CONCLUSIONS: A whole-virus influenza A(H5N1) vaccine is suitable for prepandemic or pandemic immunization in a pediatric population. CLINICAL TRIALS REGISTRATION: NCT01052402.

Safety and immunogenicity of a novel multivalent OspA vaccine against Lyme borreliosis in healthy adults: a double-blind, randomised, dose-escalation phase 1/2 trial.

BACKGROUND: Lyme borreliosis is caused by Borrelia burgdorferi sensu stricto in the USA and by several Borrelia species in Europe and Asia, but no human vaccine is available. We investigated the safety and immunogenicity of adjuvanted and non-adjuvanted vaccines containing protective epitopes from Borrelia species outer surface protein A (OspA) serotypes in healthy adults. METHODS: Between March 1, 2011, and May 8, 2012, we did a double-blind, randomised, dose-escalation phase 1/2 study at four sites in Austria and Germany. Healthy adults aged 18-70 years who were seronegative for B. burgdorferi sensu lato were eligible for inclusion. Participants were recruited sequentially and randomly assigned to one of six study groups in equal ratios via an electronic data capture system. Participants and investigators were masked to group allocation. Participants received three vaccinations containing 30 µg, 60 µg, or 90 µg OspA antigen with or without an adjuvant, with intervals of 28 days, and a booster 9-12 months after the first immunisation. The coprimary endpoints were the frequency and severity of injection-site and systemic reactions within 7 days of each vaccination, and the antibody responses to OspA serotypes 1-6, as established by ELISA. This study is registered with ClinicalTrials.gov, number NCT01504347. FINDINGS: 300 participants were randomly assigned: 151 to adjuvanted vaccines (50 to 30 µg, 51 to 60 µg, and 50 to 90 µg doses), and 149 to non-adjuvanted vaccines (50 to 30 µg, 49 to 60 µg, and 50 to 90 µg doses). Adverse reactions were predominantly mild, and no vaccine-related serious adverse events were reported. The risk of systemic reactions (risk ratio 0·54 [95% CI 0·41-0·70]; p<0·0001) and of moderate or severe systemic reactions (0·35 [0·13-0·92]; p=0·034) was significantly lower for adjuvanted than non-adjuvanted formulations. The 30 µg adjuvanted formulation had the best tolerability profile; only headache (five [10%, 95% CI 4-20] of 50), injection-site pain (16 [32%, 21-45]), and tenderness (17 [34%, 23-47]) affected more than 6% of patients. All doses and formulations induced substantial mean IgG antibody titres against OspA serotypes 1-6 after the first three vaccinations (range 6944-17,321) and booster (19,056-32,824) immunisations. The 30 µg adjuvanted formulation induced the highest antibody titres after the booster: range 26,143 (95% CI 18,906-36,151) to 42,381 (31,288-57,407). INTERPRETATION: The novel multivalent OspA vaccine could be an effective intervention for prevention of Lyme borreliosis in Europe and the USA, and possibly worldwide. Larger confirmatory formulation studies will need to be done that include individuals seropositive for Borrelia burgdorferi sensu lato before placebo-controlled phase 3 efficacy studies can begin. FUNDING: Baxter.

Cell culture (Vero cell) derived whole-virus non-adjuvanted H5N1 influenza vaccine induces long-lasting cross-reactive memory immune response: homologous or heterologous booster response following two dose or single dose priming.

BACKGROUND: Influenza pandemic preparedness involves priming of the population with pre-pandemic vaccines. Such vaccines should be well tolerated and induce a long-lasting immunological memory that can effectively be boosted with a single dose of pandemic vaccine once available. The presented studies assessed different prime-boost regimens with a Vero cell-derived whole virus non-adjuvanted H5N1 vaccine. METHODS: In one study, 281 healthy adult (18-59 years) and 280 elderly (≥ 60 years) subjects received two vaccinations, 21 days apart, with Vero cell-derived whole virus non-adjuvanted H5N1 vaccine (7.5 µg HA Antigen A/Vietnam/1203/2004) followed by a 6, 12-15, or 24 month booster (7.5 or 3.75µg A/Indonesia/05/2005 or A/Vietnam/1203/2004). In the other study, 230 healthy adults (18-59 years) received single dose priming (7.5 µg A/Vietnam/1203/2004) followed by a 12 month booster (7.5 or 3.75 µg A/Indonesia/05/2005). Antibody responses were assessed by microneutralization (MN) and single radial hemolysis (SRH) assay. Vaccine safety was assessed throughout. RESULTS: Two dose priming was equally immunogenic in adults and the elderly: >72% of subjects in each population achieved MN titers ≥ 1:20 after the second vaccination. Booster vaccinations at 6, 12-15, and 24 months induced substantial antibody increases to both strains: after a 7.5 µg A/Indonesia/05/2005 booster, 93-95% of adults and 72-84% of the elderly achieved MN titers ≥ 1:20 against this strain. Homologous and heterologous booster responses were higher in the 7.5µg dose group than in the 3.75 µg dose group. Booster responses following single dose priming were similar; a 7.5 µg booster dose induced homologous MN titers ≥ 1:20 in 93% of subjects. CONCLUSIONS: A Vero cell derived whole virus non-adjuvanted H5N1 influenza vaccine is well tolerated and induces long-lasting cross-clade immunological memory that can be effectively boosted 1-2 years after two dose or single dose priming, supporting its suitability for pre-pandemic vaccination.

Antibody persistence after two vaccinations with either FSME-IMMUN® Junior or ENCEPUR® Children followed by third vaccination with FSME-IMMUN® Junior.

Tick-borne encephalitis (TBE) vaccination strategies to induce optimal seroprotection in children are under constant evaluation. This multi-center, randomized, controlled, phase III clinical study examined antibody persistence in children aged 1-11 y following two prospectively administered doses of either the FSME-IMMUN® Junior or Encepur Children® vaccines, as well as investigating the immunogenicity, safety and vaccine interchangeability of a third vaccination with FSME-IMMUN(®) Junior. A high level of antibody persistence was observed in all subjects 6 mo after the first of two vaccinations with either pediatric TBE vaccine. Based on both immunological tests and viral antigens used, slightly higher seropositivity rates and higher GMCs /GMTs were found in children vaccinated with FSME-IMMUN® Junior compared with those who received Encepur® Children. Seropositivity rates across all age strata combined six months after the first vaccination with FSME-IMMUN® 0.25 mL Junior were 95.1% as determined by Immunozym ELISA, 93.2% as determined by Enzygnost ELISA and 95.3% as determined by NT; compared with 62.6%, 80.5% and 91.0% respectively after vaccination with Encepur® Children. A third vaccination with FSME-IMMUN(®) Junior induced 100% seropositivity in both study groups and was well tolerated as demonstrated by the low rates of systemic and injection site reactions. Subjects who received either FSME-IMMUN Junior® or Encepur(®) Children vaccine for the first two vaccinations and FSME-IMMUN Junior® for the third showed a comparably strong immune response regardless of the previous TBE vaccine administered, demonstrating that two vaccinations with Encepur® Children can successfully be followed by a third vaccination with FSME-IMMUN Junior®.

Clinical evaluation to determine the appropriate paediatric formulation of a tick-borne encephalitis vaccine.

Two dose-finding studies and one open label safety study with a paediatric FSME-IMMUN formulation were conducted in children and adolescents aged 1-15 years (N=3697). The 1.2 microg antigen dose was identified as the optimal dose, inducing high seroconversion rates following the primary vaccination series. Adolescents (aged 12-15 years) vaccinated with the optimal paediatric dose (1.2 microg) attained similarly high seroprotective rates to adults (aged 16-35 years) vaccinated with the 2.4 microg formulation of FSME-IMMUN. We concluded that the FSME-IMMUN paediatric vaccine formulation is safe and highly immunogenic, not only for children <12 years, but also for adolescents <16 years.

Comparison of immunogenicity and safety between two paediatric TBE vaccines.

TBE vaccination strategies capable of inducing strong paediatric immunogenicity and acceptable reactogenicity are still under evaluation. This single-blind, multi-center, randomized, controlled, phase III clinical study compared the immunogenicity and safety of the two paediatric TBE vaccines available in Europe (FSME-IMMUN Junior and Encepur Children) following administration of two doses of either vaccine in 303 children aged 1-11 years. Regardless of immunological test or viral antigen used, immunological responses were consistently higher in children vaccinated with FSME-IMMUN Junior than those vaccinated with Encepur Children. FSME-IMMUN Junior is also non-inferior to Encepur Children, with respect to NT seropositivity rates (p<0.0001). Systemic reaction rates were low and similar between the vaccines. However, among children aged 7-11 years, local reactions were significantly higher after the first (p<0.01) and second (p<0.001) vaccination with Encepur Children than with FSME-IMMUN Junior, affecting half the children in the former group: 22.4% and 10.2% with FSME-IMMUN Junior vs. 49.0% and 51.0% for Encepur Children.

A cell culture (Vero)-derived H5N1 whole-virus vaccine induces cross-reactive memory responses.

Novel strategies are required to provide rapid vaccine coverage in the event of an influenza pandemic. A phase I/II dose finding/formulation study was performed with a whole-virus H5N1 clade 1 A/Vietnam vaccine (2-dose priming regimen) to evaluate safety and immunogenicity. Seventy-seven of 141 subjects in this study received a booster (12-17 months after priming) with a 7.5-microg dose of a clade 2.1 A/Indonesia vaccine. The prime-boost regimen resulted in antibody responses against clade 1, 2.1, 2.2, and 2.3 viruses that were significantly higher than those after the priming regimen. These findings demonstrate that a prime-boost regimen may alleviate vaccine supply constraints in a pandemic.

The influence of carrier protein on the immunogenicity of simultaneously administered conjugate vaccines in infants.

Continuing additions of new vaccines to routine infant vaccination schedules have prompted concerns about potential interactions between vaccine components reducing desired protective effects. One hypothesis is that increasing loads of carrier protein may interfere with immune responses to polysaccharide components of co-administered glycoconjugate vaccines. Based upon a critical appraisal of existing evidence, however, neither carrier protein type nor dose adequately explains observed interference. Moreover, in five clinical trials, enhancement of anti-polyribosylribitol phosphate Haemophilus influenzae type b antibody has been demonstrated after co-administration of monovalent meningococcal C conjugate vaccine with tetanus toxoid carrier. Empirical observations do not fit well with carrier-induced epitope suppression as an underlying mechanism of interference. Thus, co-administration of conjugate vaccines can have positive as well as negative effects, and predictors of vaccine interactions are still lacking.

A clinical trial of a whole-virus H5N1 vaccine derived from cell culture.

BACKGROUND: Widespread infections of avian species with avian influenza H5N1 virus and its limited spread to humans suggest that the virus has the potential to cause a human influenza pandemic. An urgent need exists for an H5N1 vaccine that is effective against divergent strains of H5N1 virus. METHODS: In a randomized, dose-escalation, phase 1 and 2 study involving six subgroups, we investigated the safety of an H5N1 whole-virus vaccine produced on Vero cell cultures and determined its ability to induce antibodies capable of neutralizing various H5N1 strains. In two visits 21 days apart, 275 volunteers between the ages of 18 and 45 years received two doses of vaccine that each contained 3.75 microg, 7.5 microg, 15 microg, or 30 microg of hemagglutinin antigen with alum adjuvant or 7.5 microg or 15 microg of hemagglutinin antigen without adjuvant. Serologic analysis was performed at baseline and on days 21 and 42. RESULTS: The vaccine induced a neutralizing immune response not only against the clade 1 (A/Vietnam/1203/2004) virus strain but also against the clade 2 and 3 strains. The use of adjuvants did not improve the antibody response. Maximum responses to the vaccine strain were obtained with formulations containing 7.5 microg and 15 microg of hemagglutinin antigen without adjuvant. Mild pain at the injection site (in 9 to 27% of subjects) and headache (in 6 to 31% of subjects) were the most common adverse events identified for all vaccine formulations. CONCLUSIONS: A two-dose vaccine regimen of either 7.5 microg or 15 microg of hemagglutinin antigen without adjuvant induced neutralizing antibodies against diverse H5N1 virus strains in a high percentage of subjects, suggesting that this may be a useful H5N1 vaccine. (ClinicalTrials.gov number, NCT00349141.)

Group C meningococcal polysaccharide-tetanus toxoid conjugate vaccine: a meta-analysis of immunogenicity, safety and posology.

A conjugate vaccine comprised of de-O-acetylated group C meningococcal polysaccharide coupled to tetanus toxoid (GCMP-TT) has been licensed in 32 countries and incorporated in a comprehensive UK vaccination program. Extensive evidence, forming the subject of this meta-analysis, has rapidly accumulated on the immunogenicity, safety and posology of GCMP-TT as well as its epidemiological impact. GCMP-TT has been shown effective after a single dose in individuals >12 months of age, and initial posology specified three doses in infants. However, based on a recent clinical trial, posology was reduced to two doses in infants. Pooled protection rate, defined as proportion of subjects with serum bactericidal antibody (SBA) levels > or = 1:8, was 99.4% (CI, 98.2-99.9%) in seven clinical trials covering all age groups. Robust responses to GCMP-TT have been demonstrated with respect to SBA, IgG levels and antibody avidity. In post-marketing pharmacosurveillance encompassing >12 x 10(6) GCMP-TT doses distributed worldwide, the vaccine has been well tolerated with an incidence rate of 0.01% for all the most commonly encountered types of adverse events. After a catch-up UK vaccination campaign where 5-8 year old children were primarily given GCMP-TT, a 93% decline in meningococcal disease incidence was observed. In view of its immunogenicity, safety and potential suitability for use among infants in reduced dose schedules, GCMP-TT appears to mark a major advance over predecessor polysaccharide vaccines for the prevention of meningococcal C disease.